BR102017019200B1 - COMPOSITE ELECTROLYTE, SECONDARY BATTERY AND BATTERY PACK - Google Patents

Abstract

ACCORDING TO AN EMBODIMENT, A COMPOUND ELECTROLYTE IS PROVIDED. THE COMPOUND ELECTROLYTE INCLUDES A MIXTURE OF INORGANIC SOLID PARTICLES AND A NON-AQUEOUS ELECTROLYTE WHICH INCLUDES LI. THE MIXTURE OF INORGANIC SOLID PARTICLES INCLUDES FIRST INORGANIC SOLID PARTICLES WITH A FIRST LI ION CONDUCTIVITY AT 25°C AND SECOND INORGANIC SOLID PARTICLES WITH A SECOND LI ION CONDUCTIVITY AT 25°C BEING LOWER THAN THE FIRST S INORGANIC SOLID PARTICLES. A RATIO OF A WEIGHT OF NON-AQUEOUS ELECTROLYTE TO A WEIGHT OF COMPOUNDED ELECTROLYTE IS 0.1% TO 25%. THE MIXTURE OF INORGANIC SOLID PARTICLES SATISFIES 10 = D90/D10 = 500.

Description

TECHNOLOGICAL FIELD

[0001] The embodiments described here relate, in general terms, to a composite electrolyte, a secondary battery, a battery pack and a vehicle.

CONTEXT

[0002] Recently, a non-aqueous electrolytic battery, such as a secondary lithium-ion battery, has been researched and developed as a high energy density battery. The expectation is to use the non-aqueous electrolytic battery as a power source for hybrid vehicles, electric cars, an uninterruptible power source for portable phone charging bases and other similar items. Especially in the case of internal vehicle batteries, a completely solid battery has been widely studied and its high safety attracts attention.

[0003] Because the all-solid Li-ion secondary battery uses a solid electrolyte, the all-solid Li-ion secondary battery causes less ignition than a Li-ion secondary battery that uses a non-aqueous electrolyte. However, a high-capacity all-solid Li-ion secondary battery has not been put into practice to date. Some of the reasons for this include the interface between the solid electrolyte and the active electrode material. Both the solid electrolyte and the active material are solid and easily adhere to each other when heated. However, since the active material can be expanded or retracted with the addition or extraction of Li, the active material ends up being separated from the solid electrolyte when it is repeatedly subjected to charging and discharging, which can make it impossible to perform charging cycles. efficient loading and unloading. Therefore, it is necessary for the solid electrolyte to act in a way that reduces the influence of expansion or retraction of the active material and allows a good interface to form between the solid electrolyte and the active material.

BRIEF DESCRIPTION OF FIGURES

[0004] Figure 1 schematically shows the displacement of Li+ in an example of a composite electrolyte according to a first embodiment;

[0005] Figure 2 shows the particle size distribution of a mixture of inorganic solid particles comprised in an example of a composite electrolyte according to a first embodiment;

[0006] Figure 3 is a schematic view illustrating a particle size measurement method;

[0007] Figure 4 is a schematic cross-sectional view of a first example of a composite electrode that can be comprised in a secondary battery according to a second embodiment;

[0008] Figure 5 is a schematic cross-sectional view of a second example of a composite electrode that can be comprised in a secondary battery according to the second embodiment;

[0009] Figure 6 is a schematic view of a first example of a secondary battery according to the second embodiment;

[0010] Figure 7 is a schematic view illustrating a step of a method of producing a third example of a composite electrode that can be comprised in a secondary battery according to the second embodiment;

[0011] Figure 8 is a schematic view illustrating the step following the production step illustrated in Figure 7;

[0012] Figure 9 is a schematic cross-sectional view of the composite electrode produced by the production method illustrated in the Figures. 7 and 8;

[0013] Figure 10 is a schematic cross-sectional view illustrating a second example of a secondary battery according to the second embodiment;

[0014] Figure 11 is an enlarged view of the cross-section of part B of the secondary battery illustrated in Figure 10;

[0015] Figure 12 is a schematic perspective view illustrating an example of a battery module according to the third embodiment;

[0016] Figure 13 is a schematic exploded perspective view illustrating an example of a battery pack according to a fourth embodiment;

[0017] Figure 14 is a block diagram illustrating an electrical circuit of the battery pack of Figure 13;

[0018] Figure 15 is a schematic sectional view illustrating an example of a vehicle according to a fifth embodiment;

[0019] Figure 16 is a schematic view illustrating another example of a vehicle according to the fifth embodiment.

DETAILED DESCRIPTION

[0020] Generally speaking, according to one embodiment, a composite electrolyte is presented. The composite electrolyte comprises a mixture of inorganic solid particles and a Li-containing non-aqueous electrolyte. The solid particle mixture comprises first inorganic solid particles having a first conductivity of Li ions at 25°C and second inorganic solid particles having a second conductivity of Li ions at 25°C with the second conductivity of Li ions at 25°C being lower than the first conductivity of Li ions at 25°C. A ratio of a weight of non-aqueous electrolyte to a weight of composite electrolyte is 0.1% to 25%. The mixture of inorganic solid particles satisfies 10 < d90/d10 < 500. d10 is a particle size [μm] in which a cumulative frequency from a small particle size side is 10% on a cumulative particle size curve . The cumulative particle size curve is obtained by laser diffraction scattering method. d90 is a particle size [μm] in which a cumulative frequency on the small particle size side is 90% on the cumulative particle size curve.

[0021] According to one embodiment, a secondary battery is provided. The secondary battery comprises a layer containing positive electrode active material, a layer containing active material of negative electrode and a Li conductive layer. The Li conductive layer is provided between the layer containing active material of the positive electrode and the layer containing the material active of the negative electrode. The Li conductive layer comprises the electrolyte composed according to the embodiment.

[0022] According to one embodiment, the battery module is provided. The battery module comprises secondary batteries according to each embodiment.

[0023] According to one embodiment, a battery pack is provided. The battery pack comprises the secondary battery according to the embodiment.

[0024] According to one embodiment, a vehicle is provided. The vehicle comprises the battery pack according to the embodiment.

[0025] The embodiments will be explained below with reference to the diagrams (Figures). In this case, structures common to all embodiments are represented by the same symbols and repeated descriptions will be omitted. Likewise, each scheme is a typical visualization to facilitate the explanation and understanding of the concretizations. Even though, in relation to a real device, there are different parts in terms of shape, size and proportion, structural designs can be adapted taking into account the following explanations and known technologies.

(First realization)

[0026] According to a first embodiment, a composite electrolyte is provided. The composite electrolyte comprises a mixture of inorganic solid particles and a non-aqueous electrolyte comprising Li. The inorganic solid particle mixture comprises first inorganic solid particles with a first Li ion conductivity at 25°C. The second Li ion conductivity at 25°C is lower than the first Li ion conductivity at 25°C. A ratio of a weight of non-aqueous electrolyte to a weight of composite electrolyte is 0.1% to 25%. The mixture of inorganic solid particles satisfies 10 < d90/d10 < 500. d10 is a particle size [μm] in which a cumulative frequency from one size side is 10% on a small particle size cumulative curve of a mixture of inorganic solid particles. The cumulative particle size curve is obtained by laser diffraction scattering method. d90 is a particle size [μm] in which a cumulative frequency on the small particle size side is 90% on the cumulative particle size curve.

[0027] An electrolyte composed according to a first embodiment can be used, for example, in a secondary battery.

[0028] The electrolyte composed according to the first embodiment can comprise a secondary battery which can exhibit excellent half-life and efficiency in low temperature environments, according to the reasons presented below.

[0029] In the mixture of inorganic solid particles comprised in the composite electrolyte, according to the first embodiment, the second inorganic solid particles have a Li ion conductivity (a second Li ion conductivity at 25°C) lower than the Li ion conductivity of the first inorganic solid particles and may have a dielectric constant greater than that of the first inorganic solid particles. Such a mixture of inorganic solid particles comprising the first inorganic solid particles and the second inorganic solid particles can provide dielectric polarization on the surface of the second inorganic solid particles when an external electric field is applied. In the composite electrolyte, according to the first embodiment, the dissociation of Li ions can be promoted, from the non-aqueous electrolyte comprising Li, at the interface between the second inorganic solid particle in which dielectric polarization is occurring and the non-aqueous electrolyte. Consequently, it is possible to increase the concentration of Li ions acting in ionic conduction (of Li ions). An increase in Li ion concentration can also occur at the interface between the first inorganic solid particle and the non-aqueous electrolyte. Since the first Li ion-conducting inorganic solid particles can form a Li ion conduction system on the surface, the first inorganic solid particles can conduct Li ions with high transport rates. Just like these results, in the composite electrolyte, according to the first embodiment, electrical charges can be transferred with high transport rates.

[0030] In the composite electrolyte, according to the first embodiment, the ratio between the weight of the non-aqueous electrolyte and the weight of the composite electrolyte is 0.1% to 25%. In the composite electrolyte, according to the first embodiment, a sufficient amount of Li ions can be dissociated from the non-aqueous electrolyte comprised in a fraction of 0.1% or more. The non-aqueous electrolyte comprising a fraction of 25% or less of composite electrolyte, according to the first embodiment, is easily retained by the mixture of inorganic solid particles. Consequently, a secondary battery - particularly a secondary battery comprising a group of stacked-type electrodes characterized by having a bipolar structure - comprising the electrolyte composed in accordance with the first embodiment, may exhibit a low probability of causing separation of the non-aqueous electrolyte from the group. of electrodes, for example, or the effusion of non-aqueous electrolyte from the electrode group, in addition to exhibiting excellent durability. The use of the composite electrolyte in accordance with the first embodiment facilitates the manufacture of a composite such as the stacked type electrode group.

[0031] Furthermore, in a mixture of inorganic solid particles that has a d90/d10 ratio of 10 or more, a particle of size d90 and a particle of size d10 are sufficiently separated from each other on a cumulative frequency curve. The result has a large enough standard deviation, that is, there is a sufficiently wide particle size distribution.

[0032] Generally, it is considered that the smaller the amplitude of the size distribution of inorganic solid particles comprised in the composite electrolyte, that is, the smaller the d90/d10 ratio, the greater the functionality of the inorganic solid particles. However, the creators of this invention paid attention to the association between particle size distribution and dielectric constant distribution and discovered that the dissociation and conduction of Li ions described above can be improved by establishing a d90/d10 ratio that varies from 10 to 500, that is, expanding the particle size distribution. The reasons for this are considered to be the following, although we do not wish to be restricted to theory. It is considered that the degree of dielectric polarization that can occur on the surface of each particle when an electric field is applied also depends on the size of the particle. Therefore, with the mixture of inorganic solid particles having a wide particle size distribution, the degree of dielectric polarization will not be uniform. This lack of uniformity in the degree of dielectric polarization leads to the formation of a density gradient, i.e., a higher concentration of Li ions in the vicinity of the particle surface of the inorganic particle mixture. This concentration gradient acts as a driving force and promotes the conduction of Li ions dissociated by dielectric polarization. If Li ions are conducted more homogeneously, more Li ions can be dissociated by dielectric polarization. Consequently, in the electrolyte composed according to the first embodiment, the dissociation of Li from the non-aqueous electrolyte and conduction of the dissociated Li promote each other reciprocally. The result is that the electrolyte composed in accordance with the first embodiment can achieve more homogeneous Li dissociation and conduction.

[0033] Li conduction at low temperatures is greatly influenced by the apparent activation energy of the Li displacement. When Li dissociation is promoted, there is a reduction in the apparent activation energy. Consequently, the effect of more homogeneous dissociations of Li from the non-aqueous electrolyte and more homogeneous conduction of Li dissociated from the composite electrolyte is noticeable in accordance with the first embodiment when the composite electrolyte is used in an environment with low temperatures.

[0034] As previously described, since the composite electrolyte in accordance with the first embodiment comprises a mixture of inorganic solid particles that can exhibit a wide particle size distribution, the composite electrolyte can maintain electrical insulation between the electrodes when used on the secondary battery. Since the composite electrolyte in accordance with the first embodiment can achieve better Li conduction, as described previously, the secondary battery comprising the composite electrolyte makes it possible to reduce the load applied to each item of the battery, such as the electrodes. positive and negative when the battery is repeatedly charged and discharged. According to these results, the electrolyte composed in accordance with the first embodiment can provide a secondary battery that can exhibit excellent service life.

[0035] Therefore, the electrolyte composed in accordance with the first embodiment can provide a secondary battery with excellent service life and excellent performance in a low temperature environment.

[0036] A composite electrolyte in which the mixture of inorganic solid particles comprises only the first inorganic solid particle or only the second inorganic solid particle, cannot dissociate the Li ions from the non-aqueous electrolyte or guarantee the conduction of Li ions to a degree sufficient, which causes an increase in the apparent activation energy of the Li displacement. Therefore, in this case, the electrolyte does not present excellent performance in low temperature environments.

[0037] The ratio between the weight of the first inorganic solid particles and the weight of the second inorganic solid particles should preferably be 1% or more and less than 99%, even better between 10% and 90% and even better between 25% and 75%. A composite electrolyte in which the weight ratio of the first inorganic solid particles to the second inorganic solid particles is within a preferable range can achieve a better balance between the dissociation and conduction of Li ions. As a result, the composite electrolyte can achieve better efficiency in environments with low temperatures.

[0038] Since the composite electrolyte not comprising non-aqueous electrolyte or not having a ratio of less than 0.1% between the weight of the non-aqueous electrolyte and the composite electrolyte is not capable of dissociating sufficient Li ions from the non-aqueous electrolyte, the composite electrolyte will not achieve the best efficiency in low temperature environments. On the other hand, in the composite electrolyte where the ratio of the weight of the non-aqueous electrolyte to the weight of the composite electrolyte exceeds 25%, the non-aqueous electrolyte can escape (leak) from the composite electrolyte, which may create a liquid junction within the battery. The best ratio between the weight of the non-aqueous electrolyte and the weight of the composite electrolyte should vary between 1% and 10, preferably, with a variation between 2% and 10% being even better, preferably, and an even better variation between 3% and 5%. %, preferably. In the composite electrolyte where the amount of non-aqueous electrolyte is within the preferred range, the retention of the non-aqueous electrolyte in the mixture of non-aqueous electrolyte and inorganic solid particles increases. Therefore, using the composite electrolyte with this preferential characteristic facilitates the production of a series-stacked structure characterized by a bipolar structure, without the need for a separator. Furthermore, in a composite electrolyte with this preferential characteristic, Li dissociated from the nonaqueous electrolyte is more likely to move in the vicinity of the surface of the inorganic solid particles without diffusing through the nonaqueous electrolyte, so that the apparent activation energy of conduction of Li should decrease.

[0039] In a composite electrolyte comprising the mixture of inorganic solid particles with a d90/d10 ratio less than 10, the concentration gradient of Li ions generated by dielectric polarization is very small, so that the displacement of Li ions does not can be sufficiently promoted. On the other hand, a composite electrolyte comprising the mixture of inorganic solid particles with a d90/d10 ratio greater than 500 has low coatability. Therefore, it is more difficult to uniform the thickness of the composite electrolyte layer present between the positive and negative electrodes in secondary battery comprising such composite electrolyte. Such a secondary battery can cause an electrical short circuit between the positive and negative electrodes and does not have an optimal useful life.

[0040] The best d90/d10 ratio should vary between 10 and 100, with the range from 15 to 60 being even better. A composite electrolyte comprising d90/d10 ratio in a preferred range has good coatability and also better Li conductivity due to to a broad particle size distribution and may have better insulation properties between electrodes.

[0041] Preferably, the first Li ion conductivity at 25°C of the first inorganic solid particles should be 1x10-10 S/cm or more, with 1x10-6 S/cm being more desirable and even more desirable 1x10-4 S/cm cm. The first Li ion conductivity at 25°C of the first inorganic solid particles is, for example, 1x1Q-2 S/cm or less. On the other hand, preferably, the second Li ion conductivity at 25°C of the second inorganic solid particles should be less than 1x10—1° S/cm, with less than 1x1Q-12 S/cm being more desirable. The second Li ion conductivity at 25°C of second inorganic solid particles, for example, is 1x10-14 S/cm or more.

[0042] It is desirable that the mixture of inorganic solid particles meets 10 < OH/OL. Here, O is the first Li ion conductivity [S/cm] at 25°C of the first inorganic solid particles and oL is the second Li ion conductivity [S/cm] at 25°C of the second inorganic solid particles. The composite electrolyte comprising a mixture of inorganic solid particles that satisfies the oH/oL ratio of 10 or more can generate a greater Li ion concentration gradient, which can result in more homogeneous conduction of Li ions. The oH ratio /oL is more desirable 400 or more, and even more desirable is 1000 or more. The oH/oL ratio may be, for example, 1x1016 or less.

[0043] The average particle size of the first inorganic solid particles is preferably equal to the average particle size of the second inorganic solid particles. In this regard, preferably, the particle sizes are equal, so that the distance between the particles is constant and the empty spaces can be filled by the non-aqueous electrolyte. Therefore, when the Li ions dissociated from the non-aqueous electrolyte by dielectric polarization on the surface of the inorganic solid particles move on the surface of the first inorganic solid particles, the Li can move through the void spaces of uniform size. This makes it possible to minimize the distance traveled during travel, which is desirable. Alternatively, the mixture of inorganic solid particles satisfies 1 < RH/RL ≤ 100. Here, RH is an average particle size [μm] of particles having a larger average particle size between the average particle sizes of the first inorganic solid particles and of the second inorganic solid particles. RL is an average particle size [μm] of particles having a smaller average particle size between the average particle sizes of the first inorganic solid particles and the second inorganic solid particles. In this regard, preferably, the packing density of the composite electrolyte can be improved while ensuring a sufficient distance between particles for Li conduction while maintaining filling by the non-aqueous electrolyte. In this way, even if the thickness of the composite electrolyte is reduced, it is possible to maintain insulation between the electrodes. The best RH/RL ratio varies between 1 and 20 or less than 20.

[0044] The BET specific surface area of the first inorganic solid particles is preferably equal to the BET specific surface area of the second inorganic solid particles. In this regard, preferably, the contact areas of the particles with the non-aqueous electrolyte are equal to each other. The Li ions dissociated from the non-aqueous electrolyte by the dielectric polarization on the surface of the second inorganic solid particles can move on the surface of the first inorganic solid particles in a suitable proportion, so that a higher Li conductivity can be achieved. Alternatively, the mixture of inorganic solid particles preferably satisfies 1 < SH/SL < 50. Here, SH is a BET specific surface area [m2/g] of particles having a greater BET specific surface area among the BET specific surface areas of the first inorganic solid particles and second inorganic solid particles. SL is a BET specific surface area [m2/g] of particles having a smaller BET specific surface area between the BET specific surface areas of the first inorganic solid particles and the second inorganic solid particles. With these preferential aspects, the Li ions dissociated from the non-aqueous electrolyte by the dielectric polarization on the surface of the second inorganic solid particles can easily move on the surface of the first inorganic solid particles, and the coating uniformity of the composite solid electrolyte is improved, which is preferable. It is best for the SH/SL ratio to be between 1 and 6 or less than 6.

[0045] It is desirable that the electrolyte composed in accordance with the first embodiment satisfies the inequality OI>Ü2. Here, 01 is a peak frequency in a complex modulus spectrum of the composite electrolyte. W2 a peak frequency in a complex modulus spectrum of the non-aqueous electrolyte comprised in the composite electrolyte. Each complex module spectrum is represented by the following formula:

[0046] Detailed descriptions, such as of the parameters of the above formula, can be found in "I. M. Hodge, M. D. Ingram, and A. R. West, "IMPEDANCE AND MODULUS SPECTROSCOPY OF POLYCRYSTALINE SOLID ELCTROLYTE", Journal of Electroanalytical Chemistry 74 (1976) 125- 143".

[0047] The spectrum of the complex module is described here. The charge transfer in each of the components of the compound is reflected in the modulus spectrum. Specifically, a component with a peak in a high-frequency region means that there is rapid displacement of Li ions. When there is a distribution at the peak frequency, then the mobility of Li varies, that is, in the component in which there is a frequency distribution of peak, there is a mixture of sites where Li will move quickly and other sites where Li will move slowly. In a component with these characteristics, it can be determined that the Li ion concentration is high or that there are many paths for Li ions to move. Therefore, the Li ion concentration distribution can be estimated from the modulus spectrum.

[0048] It can be stated that in an electrolyte that satisfies the inequality wi > W2 that the mobility of Li ions in the entire composite electrolyte is greater than the mobility of Li ions in the non-aqueous electrolyte. Although the concentration of Li ions in the non-aqueous electrolyte is normally constant, the mobility of Li ions in the entire composite electrolyte is greater than that in a non-aqueous electrolyte. This can be said to increase the apparent concentration of Li ions due to the interaction with the inorganic particles of the composite electrolyte. A composite electrolyte performs well in low temperature environments.

[0049] For example, the electrolyte composed according to the first embodiment can satisfy the inequality C2 > C1 > C3. Here, C1 is the Li ion concentration [mol/L] at the interface between the first inorganic particles and the non-aqueous electrolyte. C2 is the Li ion concentration [mol/L] at the interface between the second inorganic particles and the non-aqueous electrolyte. C3 is the Li ion concentration [mol/L] in the non-aqueous electrolyte. That is, in a composite electrolyte that satisfies the above inequality, the concentration of Li ions in the nonaqueous electrolyte is less than the concentration of Li ions at the interface between the first inorganic solid particles and the nonaqueous electrolyte and than the concentration of Li ions at the interface between the second inorganic solid particles and the non-aqueous electrolyte. In this case, the concentration of Li ions at the interface between the second inorganic solid particles and the non-aqueous electrolyte is not less than the concentration of Li ions at the interface between the first inorganic solid particles and the non-aqueous electrolyte. In an electrolyte with these characteristics, the dissociation of Li ions can be promoted by dielectric polarization on the surface of the second inorganic compound, by which conductivity can be achieved on the surface of the first inorganic compound, so that there is a passage with a high rate of transfer and more advantageous Li driving is achieved. According to these results, the composite electrolyte with these desirable characteristics can achieve better performance in low temperature environments, more specifically, better performance in charge-and-discharge rates in low temperature environments.

[0050] Preferably, the non-aqueous electrolyte comprises a solid polymer electrolyte and/or a gel polymer electrolyte. A secondary battery is produced using the composite electrolyte of desired characteristic comprising solid polymer electrolyte, so that miniaturization of the secondary battery is facilitated. When using the composite electrolyte of the desired characteristic comprising the gel polymer electrolyte, the secondary battery can be more easily produced and interventions such as, for example, changes in the shape of the secondary battery become easier. Alternatively, the non-aqueous electrolyte may comprise a non-aqueous liquid electrolyte.

[0051] The electrolyte composed according to the first embodiment may also comprise a ligand. The state of the non-aqueous electrolyte can be adjusted by modifying the composition and amount of both the non-aqueous electrolyte and the binder in combination with the amount of polymerization initiator.

[0052] From now on, the materials that can comprise the electrolyte composed in accordance with the first embodiment will be described in greater detail.

(1) Mixture of inorganic solid particles

[0053] The first Li ion conductivity of the first Li ion-conducting inorganic solid particles is, by way of example, 1x10-10 S/cm or more at 25°C. Preferably, inorganic solid particles with a garnet-like structure are used as the first inorganic solid particles and this is because they have advantages such as high conductivity of Li ions, high resistance to reduction and a wide electrochemical window. Examples of inorganic solid particles with garnet-like structures are those of compounds represented by the general formula La5+xAxLa3-xM2O12 (“A” represents one or two groups selected from Ca, Sr and Ba, or a combination of Ca, Sr and Ba, and “M” is Nb and/or Ta), a general formula of Li3M2-xL2O12 (“M” is Ta and/or Nb, and “L” is Zr), a general formula Li7-3xAlxLa3Zr3O12 or a general formula Li7La3Zr2O12. In the general formulas above, x should be between 0 and 0.5, preferably. Among them, Li6.25Al0.25La3Zr3O12 and Li7La3Zr2O12 have higher ionic conductivity and are electrochemically stable, can achieve optimal discharge performance and yield, and are advantageously electrochemically stable in organic solvent, even when microparticulate.

[0054] In addition to inorganic solid particles with a garnet-like structure, particles of Li ion-conducting material of the Perovskite type with a composition represented by the formula La0.56Li0.33TiO3 or particles of a glass-ceramic electrolyte with a NASICON-type structure and represented by the formula Typical structural Li1+x+yTi2-xAlxP3-ySiyO12 (x = 0.3, y = 0.2) and others of the type can be used as the first inorganic solid particles.

[0055] The average particle size of the first inorganic solid particles should vary between 0.01 μm to 10 μm. Furthermore, the best range for average particle size of the first inorganic solid particles is 0.1 μm to 8 μm. This range allows for an improvement in the ionic conductivity of the composite electrolyte.

[0056] Preferably, the first inorganic solid particles should have a d90A/d10A ratio that varies from 10 to 100, and it is even better if it varies from 15 to 60. Here, d10A is a particle size [μm] in which a cumulative frequency from a small particle size side is 10% on a cumulative particle size curve of the mixture of inorganic solid particles, the cumulative particle size curve being obtained by a laser diffraction dispersion method. d90A is a particle size [μm] in which a cumulative frequency on the small particle size side is 90% in the cumulative particle size curve of the first inorganic solid particles.

[0057] The second inorganic solid particles are, preferably and without any particular limitation, at least one type of particles selected from a group comprising aluminum oxide particles, zirconium oxide particles, silicon oxide particles and magnesium oxide, taking into account its high resistance to reduction and low cost. Other examples of second inorganic solid particles are metallic oxide particles, such as rutile-type titanium oxide particles, niobium oxide particles, tantalum oxide particles, hafnium oxide particles, yttrium oxide particles, gallium oxide, germanium oxide particles and lanthanide oxide particles such as lanthanum oxide particles.

[0058] Preferably, the average particle size of the second inorganic solid particles respects a range of 0.01 μm to 10 μm. It is even more desirable that the average particle size of the second inorganic solid particles varies in a range of 0.1 μm to 8 μm.

[0059] Preferably, the second inorganic solid particles should have a d90B/d10B ratio that varies from 10 to 100, and it is even better if it varies from 15 to 60. Here, d10B is a particle size [μm] in which a cumulative frequency from a small particle size side is 10% on a cumulative particle size curve of the mixture of inorganic solid particles, the cumulative particle size curve being obtained by a laser diffraction dispersion method. d90B is a particle size [μm] in which a cumulative frequency on the small particle size side is 90% in the cumulative particle size curve of the second inorganic solid particles.

[0060] The “average particle size” of each of the inorganic solid particles described above is a primary average particle size number when the particles are comprised of primary particles, a secondary average particle size number when the particles are comprised of secondary particles and an average number of particle sizes of a mixture of primary and secondary particles without distinction between the primary and secondary particles when the particles are comprised of a mixture of the primary and secondary particles.

(2) Non-aqueous electrolyte

[0061] The non-aqueous electrolyte comprises Li ion.

[0062] The non-aqueous electrolyte may comprise, for example, a non-aqueous liquid electrolyte, a solid polymer electrolyte and/or a gel polymer electrolyte, as previously described. The non-aqueous electrolyte comprising the solid polymer electrolyte and/or gel polymer electrolyte can also be called an organic polymer-containing electrolyte.

[0063] Both the solid polymer electrolyte and the gel polymer electrolyte can be, for example, a mixture of a non-aqueous liquid electrolyte and a binder. Thus, the solid polymer electrolyte and the gel polymer electrolyte may comprise a mixture of two components, one component being a non-aqueous electrolyte solution and one component being a monomer.

[0064] The non-aqueous liquid electrolyte may comprise, for example, an organic solvent and an electrolyte (Li supporting electrolyte) comprising Li and dissolved in the organic solvent. The electrolyte concentration should be in a range of 0.5 mol/L to 2.5 mol/L, preferably.

[0065] Examples of possible organic solvents are cyclic carbonates, such as propylene carbonate (PC), ethylene carbonate (EC) and vinylene carbonate; linear carbonates, such as diethyl carbonate (DEC), dimethyl carbonate (DMC) and methyl ethyl carbonate (MEC); cyclic esters, such as tetrahydrofuran (THF), 2-methyltetrahydrofuran (2-MeTHF) and dioxolane (DOX); linear esters, such as dimethoxyethane (DME) and diethoxyethane (DEE); Y-butyrolactone (GBL), acetonitrile (AN) and sulfolane (SL). One of these organic solvents can be used alone or two or more of these solvents can be used in the form of a mixture of solvents. The organic solvent should preferably comprise at least one solvent selected from the following: propylene carbonate, ethylene carbonate, diethyl carbonate and methyl ethyl carbonate.

[0066] Examples of the electrolyte (Li supporting electrolyte) are lithium salts, such as lithium perchlorate (LiClO4), lithium hexaflurophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium hexafluoroarseant (LiAsF6), lithium trifluoromethanesulfonate lithium (LiCF3SO3) and lithium bis-trifluoromethylsulfonylimide (LiN(CF3SO2)2) and mixtures thereof. Preferably, the electrolyte should be resistant to oxidation, even in high potential situations and LiPF6 is even more desirable.

[0067] Examples of binders include polymer gel materials that form a gel with carbonates. Some specific examples are polyacrylonitrile (PAN), polyethylene oxide (PEO), polyvinylidene fluoride (PVdF) and polymethyl methacrylate. One of the above binders can be used alone or more than one can be used as a mixture. In the case of PVdF, for example, the amount of binder should preferably be less than 20% by weight of the weight of the composite electrolyte.

[0068] The solid polymer electrolyte and the gel polymer electrolyte are different from each other with regard to the hardness and viscosity of the polymer. A solid polymer does not exhibit fluidity due to its high degree of polymerization and high hardness. The gel polymer electrolyte comprises an electrolyte with a hardness lower than that of the solid polymer and with fluidity (viscosity).

[0069] Benzenesulfonic acid esters and alkylsulfonium salts can be used as polymerization initiators. The amount of polymerization initiator can be suitable according to the composition and amount of non-aqueous liquid electrolyte and binder.

[0070] From now on, the Li conduction mechanism in the composite electrolyte is described in accordance with the first embodiment, taking Figure 1 as a reference.

[0071] Figure 1 schematically illustrates the displacement of Li+ in an example of a composite electrolyte in accordance with the first embodiment.

[0072] The composite electrolyte 9 shown in Figure 1 comprises a mixture of inorganic solid particles 91 and a non-aqueous electrolyte 92. The mixture of inorganic solid particles comprises the first inorganic solid particles 91A and second inorganic solid particles 91B. The non-aqueous electrolyte comprises Li+, i.e. Li ions.

[0073] When an external electric field is applied to the composite electrolyte 9, dielectric polarization occurs on the surface of the second inorganic solid particles 91B. In this way, a portion of the Li ions comprised in the non-aqueous electrolyte 92 are dissociated and accumulated in the vicinity of an interface 9B between the second inorganic solid particles 91B and a portion 92B of the non-aqueous electrolyte 92. Thus, in the composite electrolyte 9, the concentration of Li ions in the vicinity of the 9B interface should increase. However, in the compound electrolyte 9 as a whole, a force acts to prevent the increase of Li ion concentration in the vicinity of interface 9B, so as to maintain the balance of Li ion concentration. Specifically, a part of the Li ions accumulated in the vicinity of interface 9B moves to the vicinity of interface 9A, between the first inorganic solid particles 91A and a part 92A of the non-aqueous electrolyte 92. In this way, Li ions would accumulate in the vicinity of interface 9A. A force acts to prevent an increase in the concentration of Li ions in the vicinity of interface 9A and a portion of the Li ions in the vicinity of interface 9A moves to the nonaqueous electrolyte 92. A portion of the Li contained in the nonaqueous electrolyte 92 can dissociate from the non-aqueous electrolyte through interface 9B. Another part is conducted through the non-aqueous electrolyte 92 and/or the first inorganic solid particles 91A. The non-aqueous electrolyte 92 and/or the inorganic solid particles 91A can form an optimal Li ion conductive path. This series of actions are linked and, in the compound electrolyte 9, the Li ions are conducted homogeneously.

[0074] The greater the concentration of Li ions at each of the interfaces 9A and 9B, the greater the force to act in maintaining the balance of Li ions. Consequently, in this case, the conduction of Li ions is facilitated. As described previously, in the composite electrolyte having a d90/d10 ratio of 10 or more for the mixture of inorganic solid particles 91, the concentration of Li ions in the vicinity of the interface 9B can be sufficiently increased by dielectric polarization. In this way, the electrolyte composed in accordance with the first embodiment can provide a secondary battery with excellent service life and excellent performance in low temperature environments.

[0075] From now on, by means of examples, a size distribution of particles comprised in a composite electrolyte is described in accordance with the first embodiment.

[0076] Figure 2 is a particle size distribution of a mixture of inorganic solid particles in an example of a composite electrolyte in accordance with the first embodiment.

[0077] The solid line shown in Figure 2 is a particle size frequency distribution of an example mixture of inorganic solid particles. On the other hand, the dotted line presented in Figure 2 is a cumulative particle size curve obtained from the particle size frequency distribution illustrated by the solid line.

[0078] In the cumulative particle size curve represented by the dotted line in Figure 2, a particle size d10 in which a cumulative frequency from a small particle size side is 10% is 0.109 μm. In the cumulative particle size curve represented by the dotted line in Figure 2, a d90 particle size in which a cumulative frequency from a small particle size side is 90% is 1.681 μm. That is, in the cumulative particle size curve represented by the dotted line in Figure 2, the d90/d10 ratio is 15.42.

[Production method]

[0079] In a composite electrolyte in accordance with the first embodiment, a mixture of inorganic solid particles is mixed with a non-aqueous electrolyte comprising Li. At this point, the weight of the non-aqueous electrolyte is set at between 0.1% to 25% of the total weight of the composite electrolyte.

[0080] The mixture of inorganic solid particles can be prepared by mixing the first inorganic solid particles with the second inorganic solid particles. Preferably, the first inorganic solid particles are prepared by mixing a series of groups of particles having different particle size distributions. By way of example, first inorganic solid particles can be prepared by the following procedure. Firstly, the particles to be treated, that is, the raw material for the first inorganic solid particles, are made available. The particles to be treated are divided into a series of groups. At this point, it is desirable to substantially standardize the weights of the groups. These groups are milled under different conditions. By way of example, one group of particles is subjected to a ball mill, while another group of particles is subjected to dry grinding in a roller compactor (steam roller) and yet another group of particles is subjected to wet grinding in a mill. of spheres (beads, pearls). Alternatively, the grinding method may be the same, but grinding done under different conditions for each group. For example, in ball or ball mill grinding, the size of the grinding medium, grinding time and rotation speed, among other parameters, can be modified for each group. Consequently, the series of particle groups obtained under different conditions can be mixed to obtain the first inorganic solid particles. Similarly, the second inorganic particles are preferably also obtained by mixing a series of groups of particles obtained by grinding under different conditions. By mixing the first and second inorganic solid particles, all obtained by the methods described above, a mixture of inorganic solid particles with a d90/d10 ratio ranging from 10 to 500 can be obtained.

[0081] In general, it is preferable for functional ceramics to have a narrow particle size distribution. In other words, as described previously, the inorganic solid particles comprised in the composite electrolyte should preferably have a lower d90/d10 ratio. On the other hand, in the composite electrolyte according to the first embodiment, a mixture of inorganic solid particles with a d90/d10 ratio ranging from 10 to 500 is used.

[Varied measurement methods] [First pre-treatment]

[0082] When one wants to measure a composite electrolyte comprised in a secondary battery, the composite electrolyte is removed from the secondary battery through the following method.

[0083] First, the battery is completely discharged. The battery can be discharged at a pre-established cut-off voltage at a current of 0.1C at a temperature of 25°C.

[0084] Next, in an isolated chamber (glove box) saturated with argon, the battery is disassembled and the composite electrode (or set of electrodes) is removed. The weight W of the composite electrode is measured. At this point, the weight W does not include the weight of the electrolyte solution adhered to the battery container.

[0085] Next, only one layer of composite electrolyte is removed from the electrode surface using the surface and inter-facial cutting analysis system (SAICAS) method. Consequently, the composite electrolyte can be separated from the composite electrode.

[0086] Next, the total weight, Wtotal, of the composite electrolyte separated from the composite electrode is determined. The type of solvent and concentration of Li salt, as well as other parameters of the non-aqueous electrolyte comprised in the composite electrolyte, can be determined by pyrolysis-GC-MS. Then, the composite electrolyte is washed with an appropriate solvent and dried, under reduced pressure, at 60°C, for 12 hours. By way of example, ethyl methyl carbonate (ethyl methyl carbonate) and the like can be used. Consequently, an organic electrolyte solution comprised in the composite electrolyte can be withdrawn. The weight Wd of a first mixture, which is obtained after drying, is determined. The weight We of the organic electrolyte solution can be obtained by subtracting the weight Wd of the first mixture from the weight Wtotal of the composite electrolyte.

[0087] Then, the first mixture is poured into a platinum crucible and heated to 600°C in atmospheric air for 1 hour. Consequently, a monomeric component (a gel polymer electrolyte and/or a monomeric component comprising a ligand) comprised in the mixture can be removed. A second mixture, the mixture left after heating, is defined as a mixture of inorganic solid particles and its weight Wi is determined. The weight Wp of a polymeric content can be obtained by the difference between the weight Wi of the second mixture (the mixture of inorganic solid particles) and the weight Wd of the first mixture.

[Measurement of particle size distribution of inorganic solid particle mixture]

[0088] The cumulative frequency curve of the mixture of inorganic solid particles can be obtained by subjecting the second mixture obtained by the previously described method to a particle size distribution measurement by the laser diffraction dispersion method.

[Second pre-treatment]

[0089] The second mixture, obtained by the method described previously, is dispersed in purified water and then centrifuged. Each fraction of the centrifuge is collected using a freeze-drying device. Consequently, particles of the second mixture with different compositions and sizes can be separated. A number of particle properties comprised in the composite electrolyte can be analyzed by powder x-ray diffraction, BET specific surface area and ionic conductivity measurement. Naturally, other analyzes can be done on the particles.

[X-ray diffraction measurement by powder method]

[0090] On each particle separated from the composite electrolyte, as previously described, the X-ray diffraction method can be applied by the powder method using Cu-Kα rays to characterize the crystalline structure of each particle.

[0091] First, the inorganic solid particles of the target sample are ground until they have an average particle size of about 5 μm. The average particle size can be obtained by the laser diffraction method. The resulting sample is transferred to a 0.2 mm deep holder in a glass sample dish. At this point, you need to fill the entire support with the sample.

[0092] Then, using another glass support, one support is pressed against the other, in order to level the surface of the sample. Care must be taken to use the right amount of sample to avoid the formation of cracks, voids and ripples in the sample. Care must also be taken that the pressure on the glass plate is sufficient.

[0093] The glass dish with the sample is taken to the X-ray diffractometer using the powder method. In this device, the sample is subjected to X-ray diffraction using the Cu-Kα ray beam method to obtain the X-ray diffraction pattern. The measurement is made using a Kβ filter or a monochromator. The measurement is performed under the following conditions: sweep speed, 2 degrees/min; step size, 0.2 degrees; tube voltage, 40 kV and tube current, 300 mA.

[0094] When the degree of sample orientation is very high, there is the possibility of deviation in the peak position and variation in the ratio of intensities, depending on the way the sample is filled. A sample with a particularly high orientation is measured using a capillary. Specifically, the capillary is filled with the sample and then attached to a rotating sample table to be analyzed under rotation. Such a measurement method can be used to reduce the influence of orientation.

[0095] On the other hand, when the inorganic solid particles comprised in the composite electrolyte cannot be isolated from the battery, the crystalline structure and crystallinity of the inorganic solid particles can be examined by the x-ray diffraction method by the powder method. According to the analysis using the Rietveld method, it is possible to identify mixture components and obtain quantitative information, such as mixing ratio, even when there are two or more phases. When the composite electrolyte layer is directly subjected to X-ray diffraction measurement by the powder method, the thickness of the composite electrolyte layer to be measured is equated to the depth of the support so that there are no errors when measuring the irradiated surface by x-rays. Measurement by the x-ray diffraction method is carried out using a parallel beam method from a Cu-Kα ray source capable of providing an output of 40 kV and 200 mA or more and using a Kβ filter or a monochromator. The measurement is carried out under the following conditions: Angular pitch 2θ = 0.02° or less, with better 2θ = 0.01° or less in a condition where the scan speed, in a θ/2θ interlocking scan mode θ /2θ, is set to 5 degrees/min or less, with 1 degree/min being better and the highest peak intensity set to 5000 cps or more.

[Measurement of particle size distribution]

[0096] The particle size distribution of each group of particles is determined by the laser diffraction scattering method. The average particle size of each group of particles can be determined from the particle size distribution obtained by this method.

[0097] For inorganic solid particles comprised in a composite electrolyte comprised in a secondary battery, the first and second inorganic solid particles can be analyzed by discriminating the first from the second inorganic solid particles and, thus, the average particle size can be determined for each group.

[0098] A sample to be analyzed must be prepared by the following method. First, a composite electrode is removed from the battery according to the procedure described previously. Then, under the same argon atmosphere, a layer comprising the composite electrolyte is exposed. Then the composite electrode is cut in the electrode stacking direction. To perform this cut, a focused ion beam (FIF) is used. Thus, a cutting surface is obtained without breaking the tissue structure. When the planar structure of the removed composite electrode is a quadrilateral (or other polygonal shape), the composite electrode shall be cut so as to obtain a straight section parallel to the diagonal line of the surface of the composite electrode and parallel to a direction in which the electrodes are stacked. Alternatively, when the planar structure of the composite electrode is circular (or substantially circular in shape, including elliptical), the composite electrode shall be cut so that the straight section is parallel to the diameter of the circle and parallel to the direction in which the electrodes are stacked. .

[0099] The cut surface obtained is analyzed in its entirety by scanning electron microscopy (SEM). In an SEM image obtained in this way, particles are randomly selected from the first and second inorganic solid particles and their sizes are measured. In this procedure, at least 100 particles are measured. The average size obtained from the 100 measurements is considered the average particle size.

[0100] Here, the particle size can be determined by the following method. First, a minimal circumscribed circle is drawn on the particles to be measured, particles selected in the SEM images obtained by the method described previously. Specifically, as demonstrated in Figure 3, a circle C with the smallest diameter among the circles surrounding the particle P (i.e., a circumscribed circle), i.e., a minimum circumscribed circle, is obtained. The diameter of the minimum circumscribed circle is defined as the particle size.

[BET specific surface area]

[0101] The BET Specific Surface Area is determined by a method in which a molecule of known adsorption area is adsorbed on the surface of the particles of the analyzed material, at a temperature of liquid nitrogen and the specific surface area is calculated from the amount adsorbed . The BET method, which uses the physical adsorption of an inert gas at low temperatures and low humidity, is the most widespread method. This BET method is based on BET Theory, the most famous methodology for calculating specific surface area, in which Langmuir theory, a monomolecular layer adsorption theory, is extended to multimolecular layer adsorption. The specific surface area obtained by this method is known as specific surface area.

[Measurement of ionic conductivity of inorganic solid particles]

[0102] The ionic conductivities of the first and second inorganic solid particles can be measured using the following procedure.

[0103] First, the first and second inorganic solid particles are separated from the secondary battery through the procedure described previously. From this point on, the object to be measured will be simply called “inorganic solid particles”, but the procedure for measuring ionic conductivity is the same for both the first and second inorganic solid particles.

[0104] Next, the inorganic solid particles are molded into a compacted green solid, with the aid of a compactor. A gold (Au) electrode is vapor deposited on each surface of the green compact to measure the sample.

[0105] Next, the sample is analyzed with a frequency response analyzer, model 1260, produced by Solartron. The frequency range for measurement varies from 5 Hz to 32 MHz. The measurement is carried out in a dry argon-saturated environment at 25°C, without exposing the sample to atmospheric air. From the measurement results, an impedance CA ZLi [ohm] of Li ion conduction is obtained. From the impedance CA ZLi, the area S [cm2] and the thickness d [cm] of the sample, the Li ion conductivity OLÍ [S/cm] of inorganic solid particles can be calculated using the following formula: σLi= (1/ZLi)X(d/S) (Where d/S is defined as a cell constant k.)

[Method for measuring ionic conductivity and modulus spectrum for composite electrolyte]

[0106] Ionic conductivity can be calculated by measuring the AC impedance of the composite electrolyte and the distribution of Li ion concentration in the composite electrolyte can be defined using an analytical method that uses complex modulus spectra.

[0107] The measurement can be carried out using the following procedure. First, a composite electrolyte layer comprising composite electrolyte is provided. A gold (Au) electrode is vapor deposited on each surface of the composite electrolyte layer to prepare a sample for analysis. The sample is analyzed by a frequency response analyzer, model 1260, produced by Solartron. The frequency range for measurement varies from 5 Hz to 32 MHz. The measurement is carried out in a dry argon-saturated environment at 25°C, without exposing the sample to atmospheric air. From the measurement results, an impedance CA ZLi [ohm] of Li ion conduction is obtained. From the impedance CA ZLi, the area S [cm2] and the thickness d [cm] of the sample, the Li ion conductivity OLÍ [S/cm] of inorganic solid particles can be calculated using the following formula: σLi= (1/ZLi)X(d/S) (In d/S is defined as a cell constant k.)

[0108] Next, the complex module spectrum analysis is performed using the following formula:

[0109] From the above formula [w: angular frequency, εc: dielectric constant, Z (w): complex impedance, k: cell constant] a complex modulus graph is obtained, in which the horizontal axis represents the logarithm of base 10 of the frequency (Hz) and the vertical axis represents the imaginary part (M”) of a complex module. The vertex frequency of the graph obtained in this way is defined as wmax. Here, in "B. Roling, "What do electrical conductivity and electrical modular modulus spectroscopy process about the mechanism of ion transport processes in melts, glasses, and crystals?", Journal of Non-Crystalline Solids 244 (1999) 34-43" , it is reported that the value of Wmax is expressed by Wmax = (Nv*1/T/εfp, where the value of Wmax is directly proportional to Nv. As Nv corresponds to the concentration of a charge carrier, the distribution of the concentration of Li ions in the composite electrolyte can be evaluated using Umax. An increase in the number of Li ions, which move easily in the composite electrolyte, statistically gives varying rates of displacement to the ions, so that the width of the peak in the graph of modulus increases (refer to "I. M. Hodge, M. D. Ingram, and A. R. West, "IMPEDANCE AND MODULUS SPECTROSCOPY OF POLYCRYSTALINE SOLID ELCTROLYTE", Journal of Electroanalytical Chemistry74 (1976) 125-143" and "B. Roling, "What do electrical conductivity and electrical modulus spectra tell us about the mechanism of ion transport processes in melts, glasses, and crystals?", Journal of Non-Crystalline Solids 244 (1999) 34-43" for details).

[0110] By this method, U1 in the entire composite electrolyte and U2 in an isolated non-aqueous electrolyte can be measured and compared.

[Confirmation of Li ion concentration distribution in composite electrolyte]

[0111] The distribution of Li ion concentration in the composite electrolyte can be confirmed by in-situ measurement using the Rutherford Back-scattering Spectrometry/Nuclear Reaction Analysis (NRA) method (Nuclear Reaction Analysis) together.

[0112] Specifically, the distribution of Li ion concentration can be confirmed by the following procedure. First, a composite electrolyte layer comprising a composite electrolyte is provided. A gold (Au) electrode is vapor deposited on each surface of the composite electrolyte layer and measurement is made by RBS/NRA at the same time that a voltage of 5V is applied between the two electrodes. Thus, it is possible to measure and compare, in the composite electrolyte layer, the concentration of Li C1 ions [mol/L] at the interface between the first inorganic solid particles and the non-aqueous electrolyte, the concentration of Li C2 ions [mol/L] /L] at the interface between the second inorganic solid particles and the non-aqueous electrolyte and the Li C3 ion concentration [mol/L] in the non-aqueous electrolyte. The C3 concentration is defined as the concentration of Li ions in the central region of a gap in the particle comprised of first inorganic solid particles and/or second inorganic solid particles.

[0113] According to the first embodiment, a composite electrolyte is provided. The composite electrolyte comprises a mixture of inorganic solid particles and a non-aqueous electrolyte comprising Li. The mixture of inorganic solid particles comprises first Li ion-conducting inorganic solid particles and second inorganic solid particles. The first inorganic solid particles have a first Li ion conductivity and the second inorganic solid particles have a second Li ion conductivity, where the second conductivity is less than the first. The weight ratio of the non-aqueous electrolyte and the weight of the composite electrolyte ranges from 0.1% to 25%. The mixture of inorganic solid particles satisfies 10 < d90/d10 < 500. In this composite electrolyte, the dissociation of Li ions from the non-aqueous electrolyte and the conduction of Li ions can occur homogeneously. As a result, the electrolyte composed in accordance with the first embodiment can provide a secondary battery capable of excellent useful life and excellent performance in low temperature environments.

(Second implementation)

[0114] According to a second embodiment, a secondary battery is provided. The secondary battery comprises a positive electrode active material-containing layer, a negative electrode active material-containing layer and a Li conductive layer. The Li conductive layer is provided between the positive electrode active material-containing layer and the active material-containing layer of the negative electrode. The Li conductive layer comprises an electrolyte composed in accordance with the first embodiment.

[0115] The layer containing active material of the positive electrode, layer containing active material of the negative electrode and the Li conductive layer provided between them, may constitute, by way of example, an electrode assembly.

[0116] The layer containing positive electrode active material may comprise a positive electrode active material. A layer containing negative electrode active material may comprise a negative electrode active material. Positive electrode active material and negative electrode active material will be described later in this text.

[0117] The layer containing positive electrode active material can be provided in a current collector to constitute a positive electrode, for example. The layer containing negative electrode active material may be provided on a current collector to constitute a negative electrode, for example.

[0118] Alternatively, the positive electrode active material-containing layer may be provided on one surface of the current collector and the negative electrode active material-containing layer may be provided on the opposite surface of the current collector to constitute a composite electrode. The composite electrode may also be referred to as a composite electrode comprising a bipolar-type structure. That is, the electrode comprising a bipolar-type structure may comprise a current collector comprising a first surface and an opposing second surface, a layer containing positive electrode active material provided on the first surface of the current collector, and a layer containing electrode material negative provided on the second surface of the current collector.

[0119] Both the positive electrode active material-containing layer and the negative electrode active material-containing layer may comprise an electrolyte. The electrolyte, which may be comprised in the layer containing positive electrode active material and/or in the layer containing active material of negative electrode, may be comprised (or comprise) the electrolyte composed according to the first embodiment. Alternatively, the electrolyte, which may be comprised in the positive electrode active material-containing layer and/or in the negative electrode active material-containing layer, may comprise an electrolyte other than the electrolyte composed according to the first embodiment. The electrolyte may be a non-aqueous electrolyte and/or gel polymer electrolyte, which is different from the non-aqueous electrolyte comprised in the composite electrolyte according to the first embodiment. These may be those described in the first embodiment.

[0120] The Li conductive layer can conduct Li ions. For example, the Li conductive layer can be a separator provided between the layer containing positive electrode active material and the layer containing negative electrode active material. Alternatively, the Li conductive layer may be located between the positive electrode active material-containing layer and the negative electrode active material-containing layer. The Li conductive layer comprises the electrolyte composed in accordance with the first embodiment. The Li conductive layer may also comprise, for example, a liquid electrolyte. This liquid electrolyte, for example, may be a non-aqueous electrolyte. Such a non-aqueous electrolyte, for example, may be the non-aqueous liquid electrolyte described previously. The weight fraction of the composite electrolyte according to the first embodiment in the Li conductive layer is preferably 100% with respect to the weight of the Li conductive layer.

[0121] The layer containing positive electrode active material, the layer containing negative electrode active material and the Li conductive layer can constitute a group of electrodes. For example, the electrode group may have a coil-type structure. The electrode group having a coil-like structure is obtained by spirally folding stacked electrodes. This electrode stack comprises a positive electrode, a Li conductive layer and a negative electrode, all stacked in that order. Here, as previously described, the positive electrode comprises a current collector and a layer containing positive electrode active material provided on the current collector. Furthermore, as previously described, the negative electrode comprises a current collector and a layer containing negative electrode active material provided on the current collector. By way of example, the coil-type electrode group may have a flat shape.

[0122] Alternatively, by way of example, the electrode group may have a stacked structure. The group of electrodes with stacked-type structure comprises, for example, positive electrodes, negative electrodes and Li conductive layers. Each Li conductive layer is provided between a layer containing positive electrode active material and a layer containing negative electrode active material . Alternatively, the group of electrodes with stack-type structure may comprise, for example, electrodes with bipolar-type structures, i.e., the secondary battery in accordance with one aspect of the second embodiment comprises composite electrodes and each of the composite electrodes has the structure bipolar described previously. The secondary battery in accordance with this aspect may comprise, for example, a first electrode composite and a second electrode composite provided adjacent to the first electrode composite. In a secondary battery of this type, the Li conductive layer is provided between the active material-containing layer of the first electrode composite and the active material-containing layer of the second electrode composite. The secondary battery with these characteristics may also comprise a pair of positive and negative electrodes. The positive electrode may comprise, for example, a current collector and a layer containing positive electrode active material provided on a surface of the current collector. The negative electrode may comprise, for example, a current collector and a layer containing negative electrode active material provided on a surface of the current collector. The positive electrode active material-containing layer of the positive electrode may face the negative electrode active material-containing layer of an electrode composite with the Li conductive layer sandwiched between them.

[0123] The battery according to the second embodiment may also comprise a container. The positive electrode active material containing layer, the negative electrode active material containing layer and the Li conductive layer can be packed in the container. When combining the use of another non-aqueous electrolyte, the non-aqueous electrolyte can also be packed in the container.

[0124] The battery comprising the negative electrode and the positive electrode may also comprise a negative electrode terminal electrically connected to the negative electrode and a positive electrode terminal electrically connected to the positive electrode.

[0125] The battery according to the second embodiment may be connected in series or parallel, combined with another type of battery and/or combined with a casing to form a battery pack. For the battery pack, known and conventional configurations can be appropriately selected. The specific battery pack configuration example will be described later.

[0126] From now on, parts that may be included in the battery according to the second embodiment will be described in detail.

(1) Layer containing negative electrode active material

[0127] The layer containing negative electrode active material may comprise, for example, a negative electrode active material, a conductive agent and a binder.

[0128] The negative electrode active material can be a material to which it is possible to add and from which it is possible to remove Li. As such, one can use as the negative electrode active material, a carbon material, an alloy material Li metal, a metal oxide and a metal sulfide, for example. Among these, materials with Ti (Ti-containing) in their composition are the best. It is particularly preferred to use negative electrode active material particles of at least one type of Ti-containing oxide selected from Ti-Li-containing oxide, Ti-containing oxide, Nb-Ti-containing oxide and Na-Nb-Ti-containing oxide. , each of these having a Li ion insertion-extraction potential of 1 V (vs. Li/Li+) to 3 V (vs. Li/Li+), based on the oxidation-reduction potential of Li.

[0129] Examples of Li-Ti-containing oxides are a lithium-titanium oxide composite represented by the general formula LÍ4+xTÍ50i2 (-1 < x < 3) with a spinel-type crystalline structure, a lithium-titanium oxide composite represented by the general formula LÍ2+XTÍ3O7 (0 ^ x < 4) with a ramsdellite-type crystal structure.

[0130] Examples of a Ti-containing oxide are a Ti-containing oxide represented by the general formula Li1+xTi2O4, a general formula Li1.1+xTi1.8O4, a general formula Li1.07+xTi1.86O4 or a general formula LixTiO2 ( 0 ≤ x ≤ 1 for all general formulas), Ti-containing oxide represented by the general formula LixTiO2 (0≤ x≤ 1) with a monoclinic structure ((TiO2(B) as pre-charge structure) is Ti-containing oxide with rutile or anatase structure (TiO2 as pre-charge structure).

[0131] Examples of Nb-Ti-containing oxide are those represented by the general formula LiaTiMbNb2±β07±o (0 < a < 5; 0 < b < 0.3; 0 < β < 0.3; 0 < o < 0 ,3; “M” is at least one element selected from Fe, V, Mo and Ta (“M” can be an isolated element from the group or a combination of two or more elements selected from the above group)).

[0132] Examples of metal oxide composites are those represented by the general formula Li2+aM(I)2-bTi6-cM(II)dO14+o (M(I) is Na or contains Na and at least one other element selected from Sr , Ba, Ca, Mg, Cs and K (M(I) can be one of the elements of the group or a combination of one or more elements of the group); M(II) is at least one element selected from Zr, Sn, V , Nb, Ta, Mo, W, Fe, Co, Mn and Al (M(II) can be an element of the group or a combination of two or more elements of the group); 0 ≤ a ≤ 6, 0 ≤ b < 2 , 0 < c < 6, 0 < d ≤ 6, -0.5 ≤ σ ≤ 0.5) . Among the compounds represented by the general formula presented above, the one containing Na, Li, Nb and Ti is included among the oxides containing Li-Na-Nb-e-Ti.

[0133] For use as a negative electrode active material, one of the materials may be used alone or two or more materials may be used together. The lithium-titanium oxide composite represented by the general formula LÍ4+XTÍ5O12 (-1 ≤ x ≤ 3), with a spinel-type crystalline structure and small volumetric variation, is the most suitable.

[0134] When using the previously described Ti-containing oxide, an aluminum foil can be used as a current collector that supports the layer containing negative electrode active material instead of a copper foil. Aluminum foil can weigh less than copper foil and be low in cost. As a result, the weight and cost of the battery can be reduced. Furthermore, it is advantageous from the point of view of weight and capacity in relation to the size of the battery with bipolar structure electrode described below.

[0135] The negative electrode active material may have, for example, a particle shape. The negative electrode active material particles may be primary or secondary particles formed by the aggregation of the primary particles. Alternatively, the negative electrode active material particles may be a mixture of the primary particles and secondary particles. For a further increase in density, it is preferable that the primary particles present represent an amount ranging from 5% of the volume to 50% of the volume of the layer containing negative electrode active material.

[0136] Negative electrode active material particles must have an average primary particle size of 1 μm or less and a specific surface area ranging from 3 m2/g to 200 m2/g measured by a BET method in accordance with N2 adsorption . By using such negative electrode active material particles, the affinity between the layer containing negative electrode active material and the non-aqueous electrolyte can be improved when the non-aqueous electrolyte is used in the battery. By setting the primary particle size to 1 μm or less, the diffusion distance of Li ions within the active material can be decreased. The specific surface area can be increased. The method of measuring specific surface area by the BET method is the same as that described previously. The average primary particle size should preferably vary between 0.1 and 0.8 μm.

[0137] The reason why the average primary particle size of the negative electrode active material particles must be within this range is as follows: when the specific surface area of the layer containing negative electrode active material increases from 3 m 2 / g to 50 m2/g, because of the use of primary particles whose average size is greater than 1 μm, a decline in the porosity of the layer containing negative electrode active material cannot be avoided. The details of this phenomenon will be described later. However, when the average primary particle size is small, aggregation of primary particles is more likely to occur. When aggregation of primary particles occurs in the battery with non-aqueous electrolyte, for example, the distribution of non-aqueous electrolyte is diverted to the layer containing negative electrode active material, which may cause a decrease in the electrolyte in the layer containing active electrode material positive. The minimum desirable limit is 0.1 μm.

[0138] The average particle size (diameter) of the secondary particles of the negative electrode active material particles is preferably greater than 2 μm. It is more preferable that the average secondary particle size of the negative electrode active material particles is greater than 5 μm. The average secondary particle size range should vary from 7 μm to 20 μm. This range allows a layer containing high-density negative electrode active material to be produced even when there is a drop in pressure over the negative electrode. For example, in the case of using an Al-containing sheet as a current collector, the elongation of the Al-containing sheet can be suppressed.

[0139] Negative electrode active material particles containing secondary particles of an average size of 2 μm can be obtained, for example, in the following way. First, an active material precursor containing primary particles of average particle size of 1 μm or less is produced by reacting the raw materials and then subjecting them to a fire treatment. The incinerated product obtained is then ground in a grinder, such as a ball mill or jet mill. The ground material thus obtained is then subjected to fire treatment. With this procedure, the active material precursor can aggregate and form secondary particles of larger particle size.

[0140] It is preferable to coat the surface of the secondary particles with carbon dioxide material, in order to reduce the electrical resistance of the layer containing negative electrode active material. Secondary particles of the negative electrode active material coated with carbonic material can be produced, for example, by adding a precursor of a carbonic material in a secondary particle production process and carrying out a fire treatment at a temperature of 500°C or more, in an inert atmosphere.

[0141] A conductive agent is added to improve the conductivity of the layer containing negative electrode active material. When the current collector is used, the contact resistance between the layer containing negative electrode active material and the current collector can be suppressed by the conductive agent. A carbonic material, for example, can be used as a conductive agent. Examples of carbonic material are soot, carbon black, coke, carbon fiber, aluminum powder or TiO. Most suitable are coke, graphite and a TiO powder, each having been subjected to heat treatment at a temperature ranging from 800°C to 2000°C and with an average particle size of 10 μm or less, or a carbon fiber with a fiber diameter of 1 μm or less. The specific surface area of these carbonic materials, measured by the BET N2 adsorption method, must be 10 m2/g or more. One of these can be used as a conductive agent or a mixture of two or more of these materials can be used as a conductive agent.

[0142] The binder can, for example, connect the negative electrode active material and the conductive agent. Examples of binders include poly-tetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), fluorine-based rubber, styrene-butadiene rubber and “core-shell” binders. Alternatively, a combination of two or more of these ligands can be used as a ligand.

[0143] With regard to the fractions of each component in mixtures of negative electrode active material, the conductive and binding agent in the layer containing negative electrode active material, it is best if the negative electrode active material ranges from 80% by weight to 95% by weight, that the conductive agent ranges from 3% by weight to 18% by weight and that the binder ranges from 2% by weight to 7% by weight.

[0144] As the amount of binder increases, the dispersibility of the particles tends to increase. However, in these cases, the surface of the particles is easily covered by the ligand and, consequently, the specific surface area of the layer containing negative electrode active material decreases. On the other hand, if the amount of binder is small, the particles agglomerate easily and, consequently, it is desirable to adjust the stirring conditions (the number of revolutions of a ball mill, stirring time and stirring temperature) to suppress the agglomeration of particles. Thus, fine particles can be dispersed evenly. Furthermore, even if the added amount of binder and the stirring conditions are in the appropriate ranges, when the amount of conductive agent is large, the surface of the negative electrode active material is easily covered by the conductive agent and the porosity of the electrode surface negative electrode decreases and therefore the specific surface area of the negative electrode layer decreases.

[0145] On the other hand, when the amount of conductive agent is small, the negative electrode active material may tend to be easily sprayed, and therefore, the specific surface area of the layer containing negative electrode active material increases. Alternatively, in these cases, the dispersibility of the negative electrode active material particles may tend to decrease and therefore the specific surface area of the layer containing negative electrode active material decreases. Furthermore, not only the amount of conductive agent but also the average particle size and specific surface area of the conductive agent can affect the specific surface area of the layer containing negative electrode active material. It is desirable that the conductive agent have an average particle size equal to or smaller than that of the negative electrode active material and a specific surface area greater than that of the negative electrode active material.

[0146] The layer containing negative electrode active material can be produced by the following procedure, for example. First, the negative electrode active material, the conductive agent and the ligand described above are suspended in an appropriate solvent to obtain a suspension. In this case, it is desirable to evenly disperse the negative electrode active material particles at such a point that the amount of ligand is small. Then, this suspension is applied to a substrate, such as the current collector. The film applied to the current collector is dried and compressed under heat. In this way, the layer containing negative electrode active material can be obtained.

[0147] Next, a reason is given why the specific surface area of the layer containing negative electrode active material should preferably vary between 3 m2/g to 50 m2/g. In a layer containing negative electrode active material with a specific surface area less than 3 m2/g, particle agglomeration is prominent. For this reason, for example, when non-aqueous electrolyte is used, the affinity between the layer containing negative electrode active material and non-aqueous electrolyte may be reduced, leading to an increase in the interface resistance of the layer containing negative electrode active material . As a result, output performance and charge-discharge cycle performance may be deteriorated. On the other hand, in a layer containing negative electrolyte active material with a specific surface area greater than 50 m2/g, the distribution of the non-aqueous electrolyte may be biased towards the layer containing negative electrode active material, resulting in a lack of electrolyte. non-aqueous in the layer containing positive electrode active material. In this case, the output performance and charge-discharge cycle performance may not be improved. An even more desirable range for specific surface area is from 5 m2/g to 50 m2/g. Here, the specific surface area of the layer containing negative electrode active material means the surface area per 1 gram of the layer containing negative electrode active material.

[0148] The layer containing negative electrode active material may be, for example, a porous layer supported on the current collector and comprise the negative electrode active material, the conductive agent and the binder. If the layer containing negative electrode active material is porous, the porosity (excluding the current collector) should preferably vary between 20% and 50%. Therefore, for example, in a battery in which non-aqueous electrolyte is used, it is possible to obtain the layer containing negative electrode active material of high density and with excellent affinity between the layer containing negative electrode active material and the non-aqueous electrolyte. . An even more desirable range for porosity is 25% to 40%.

(2) Layer containing positive electrode active material

[0149] The layer containing positive electrode active material may comprise, for example, a positive electrode active material, a conductive agent and a binder. 0 ≤ a ≤ 6, 0 ≤ b < 2, 0 < c < 6, 0 < d ≤ 6, -0.5 ≤ σ ≤ 0.5)

[0150] The negative electrode active material can be a material to which it is possible to add and from which it is possible to remove Li. As such, the Li-Ni-Al-containing oxide composite ( e.g., LixNi1-yAlyO2; 0 < x ≤ 1, 0 < y < 1), Li-Co-containing oxide composite (e.g., LixCoO2; 0 < x ≤ 1), Li-Mn-containing oxide composite (e.g. , LixMn2O4 or LixMnO2; 0 < x ≤ 1), Li-Ni-containing oxide composite (e.g. LixNiO2; 0 < x ≤ 1), Li-Co-Al-containing oxide composite, Li-Ni-containing oxide composite Co-Mn (e.g., LixNi1-yCoyO2; 0 < x ≤ 1, 0 < y < 1), Li-Mn-Ni-containing oxide composite with a spinel-type structure (e.g., LixMn2-yNiyO4; 0 < x ≤ 1.0 < y < 2), Li-Mn-Co-containing oxide composite (e.g. LixMnyCo1-yO2; 0 < x ≤ 1.0 < y < 1), lithium phosphate with olivine-type crystal structure ( e.g., lithium iron phosphate (LixFePO4; 0 < x ≤ 1)lithium phosphate salt (e.g., LixFe1-yMnyPO4 and LixCoPO4; 0 < x ≤ 1, 0 < y < 1)) and fluorinated iron sulfates (e.g. LixFeSO4F; 0 < x ≤ 1).

[0151] These oxide composites are used preferentially because it is possible to obtain high potential on the positive electrode. Among these, the Li-Ni-Al-containing oxide composite, the Li-Ni-Co-Mn-containing oxide composite and the Li-Mn-Co-containing oxide composite can suppress the reaction with the non-aqueous electrolyte at high temperatures and considerably increases battery life. Particularly, the Li-Ni-Co-Mn-containing oxide composite represented by the formula LixNi1-y-zCoyMnzO2 (0 < x < 1.1; 0 < y < 0.5; 0 < z < 0.5) is desirable. Excellent durability and lifetime under high temperatures can be obtained when using Li-Ni-Co-Mn-containing oxide composite.

[0152] Other material can be used as positive electrode active material, such as, for example, manganese dioxide (MnO2), iron oxide, nickel oxide and vanadium oxide (for example, V2O5).

[0153] One of the materials mentioned above can be used alone as the positive electrode active material or a mixture of two or more materials.

[0154] The positive electrode active material may have, for example, a particle shape. The average primary particle size of the positive electrode active material should preferably range from 100 nm to 1 μm. Positive electrode active material with an average primary particle size of 100 nm or more is easily operated during industrial production. Positive electrode active material with an average primary particle size of 1 μm or less allows homogeneous diffusion of Li ions into a solid.

[0155] The specific surface area of the active material of the positive electrode should preferably vary between 0.1 m2/g to 10 m2/g. Positive electrode active material with a specific surface area of 0.1 m2/g or more can ensure sufficient sites into which lithium ions can be inserted and from which they can be removed. Positive electrode active material with a specific surface area of 10 m2/g or less has easier industrial production and can ensure good charge-discharge cycle performance.

[0156] The conductive agent can be added to improve electrical conductivity in the layer containing positive electrode active material. If a current collector is used, the contact resistance between the positive electrode active material-containing layer and the positive electrode current collector can be suppressed. Examples of conductive agents are soot, carbon black and graphite. One of these materials may be used individually or a combination of two or more as a conductive agent.

[0157] By way of example, the binder can connect the active material and the conductive agent. Examples of binders are polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF) and fluorine rubber. One of these compounds can be used alone as a ligand or a combination of two or more can be used as a ligand.

[0158] With regard to the fractions of each component in mixtures of positive electrode active material, the conductive and binding agent in the layer containing negative electrode active material, it is best if the negative electrode active material ranges from 80% of the weight to 95% by weight, that the conductive agent ranges from 3% by weight to 18% by weight and that the binder ranges from 2% by weight to 7% by weight. For the conductive agent, if its content represents 3% of the weight or more, the effect described above can be obtained. If the content of the conductive agent represents 18% by weight or less, the decomposition of non-aqueous electrolyte on the surface of the conductive agent can be suppressed during storage at high temperatures. For the binder, if the content represents 2% or more of the weight, sufficient electrode force can be achieved. If the binder content represents 7% by weight or less, the amount of insulator in the electrode can be reduced.

[0159] The layer containing positive electrode active material can be produced, for example, according to the following procedure. First, the positive electrode active material described above, the conducting agent and the ligand are suspended in appropriate solvent to obtain a suspension. Then, the suspension is applied to the substrate, such as a current collector. The film applied to the current collector is dried and compressed and thus a layer containing positive electrode active material can be obtained. The pressure on the positive electrode should preferably vary between 0.15 ton/mm to 0.3 ton/mm. When compression is performed with a pressure within this range, the adhesion between the layer containing positive electrode active material and the substrate increases and the elongation percentage of the substrate can be suppressed to 20% or less, which is preferable.

(3) Current collector

[0160] It is preferable to use a foil comprising aluminum (Al) as a current collector, which can be used as a negative electrode. For such Al-containing foil, it is preferable to use aluminum foil or aluminum alloy foil. Particularly, it is preferable to use pure Al aluminum foil (100% purity) or aluminum alloy foil (Al alloy) in which the aluminum purity is 98% or more and less than 100 %. The purity of aluminum in Al alloy is preferably 99.99%. The thickness of the Al foil or Al alloy foil is, for example, 20 μm or less, and preferably 15 μm or less. An alloy comprising at least one element selected from Fe, Mg, Zn, Mn and Si, in addition to Al, may be used as an Al alloy. For example, an Al-Fe alloy, an Al-Mn base alloy and an Al-M alloy. Al-Mg can obtain a higher strength than an Al alloy. On the other hand, the amount for transition metals such as Cu, Ni, Cr, etc., in Al or Al alloy is preferably 100 ppm or less (comprising 0 ppm). For example, an Al-Cu base alloy has higher strength but lower corrosion resistance and consequently the Al-Cu base alloy is not suitable as a current collector.

[0161] It is preferable to use a sheet comprising aluminum (Al) for the current collector and which can be used on the positive electrode. For such Al-containing foil, it is preferable to use an aluminum foil of pure Al (100% purity) or an aluminum alloy foil in which the purity of aluminum is 99% or more and less than 100%. An alloy comprising at least one element selected from Fe, Mg, Zn, Mn and Si, in addition to Al, may be used as an Al alloy. For example, an Al-Fe alloy, an Al-Mn base alloy and an Al alloy. Al-Mg can obtain a higher strength than an Al alloy. On the other hand, the amount for transition metals such as Cu, Ni, Cr, etc., in Al or Al alloy is preferably 100 ppm or less (comprising 0 ppm). For example, an Al-Cu base alloy has higher strength but lower corrosion resistance and consequently the Al-Cu base alloy is not suitable as the current collector.

[0162] The purity of Al in the Al-containing foil used as the positive electrode current collector should preferably vary between 99.0% and 99.99%. Within this range, the deterioration of high-temperature cycle life caused by the dissolution of impurities can be reduced.

[0163] It is preferable to use the same Al-containing foil as those used in the positive electrode current collector and negative electrode current collector as the current collector comprised in the electrode with bipolar structure.

(4) Li conductive layer

[0164] The Li conductive layer comprises the electrolyte composed in accordance with the first embodiment. The interface between the Li conductive layer and the layer containing positive electrode active material may reflect irregularities on the surface of the layer containing positive electrode active material. Likewise, the interface between the Li conductive layer and the layer containing negative electrode active material may reflect irregularities on the surface of the layer containing negative electrode active material. For example, the surface of an active material-containing layer may have irregularities because of the constituent materials of the active material-containing layer. When the active material is located on the surface of the active material-containing layer, the surface of the active material-containing layer may also have irregularities due to the active material particles.

[0165] Particularly, as described above, particles with an average secondary particle size greater than 5 μm can be used as negative electrode active material on the surface of the layer containing negative electrode active material. The layer containing negative electrode active material produced using such particles may have large irregularities on the surface. The Li conductive layer can have close contact with the layer containing negative electrode active material along the irregularities. Similarly, the Li conductive layer can have close contact with the layer containing positive electrode active material along the surface irregularities.

[0166] Such a structure allows the interface between the Li conductive layer and the layer containing positive electrode active material, as well as the interface between the Li conductive layer and the layer containing negative electrode active material, to not present gaps. Particularly, a part of the mixture of inorganic solid particles may insert deep into the gaps on the surface of the layer containing negative electrode active material.

[0167] The Li conductive layer can have a minimum thickness of less than 8 μm. The minimum thickness is preferably less than 5 μm. The minimum thickness of the Li conductive layer is the thickness of the region with the smallest thickness in the Li conductive layer. In other words, the minimum thickness of the Li conductive layer is the thickness of the region closest to the surface of the layer containing Li active matter. positive electrode and the surface of the layer containing negative electrode active material. When the surface of the layer containing active material has irregularities, a fraction in which the convex parts of the surface face each other may be, for example, the fraction with the smallest thickness.

[0168] As described above, the mixture of inorganic solid particles comprised in the electrolyte composed in accordance with the first embodiment has a d90/d10 ratio of 10 or more. Consequently, the composite electrolyte according to the first embodiment comprising the mixture of inorganic solid particles with such a wide particle size distribution can have excellent electrical insulation properties. As described above, the mixture of inorganic solid particles comprised in the composite electrolyte according to the first embodiment has a d90/d10 ratio of 500 or less. The composite electrolyte comprising the mixture of inorganic solid particles can suppress deterioration in the application property due to the very wide particle size distribution of the solid content. Therefore, the Li conductive layer comprising the composite electrolyte can exhibit great planar uniformity. According to these results, the secondary battery can ensure electrical isolation between the layer containing positive electrode active material and the layer containing active material of negative electrode even if the thickness of the Li conductive layer is reduced. The thinner the thickness of the Li conductive layer, the smaller the secondary battery, which guarantees an advantageous increase in capacity per volume.

[0169] The minimum thickness of the Li conductive layer can be set at 0.05 μm or more, for example, with 0.5 μm or more being preferred. The average thickness of the Li conductive layer is preferably 0.1 μm or more and less than 8 μm. The average thickness preferably varies from 0.5 μm to 5 μm.

[0170] The method for forming the Li conductive layer is not particularly limited. The Li conductive layer can be formed, for example, by applying a material onto the positive electrode active material-containing layer or the negative electrode active material-containing layer. Alternatively, the Li conductive layer can be formed by injecting a material between the positive electrode active material-containing layer and the negative electrode active material-containing layer. A specific example will be described later, with reference to the figures.

(5) Container

[0171] As a container, a metal container or a container made of laminated film can be used.

[0172] A metal container made of aluminum, an aluminum alloy, iron, stainless steel or others of the type can be used as a metal container. The metal container may have, for example, an angular shape or a cylindrical shape. The thickness of the container plate is, for example, 1 mm or less, preferably 0.5 mm or less, and even better 0.3 mm or less.

[0173] The metallic container made of Al alloy is preferably made of an alloy with 99.8% purity of Al and comprises at least one type of element selected from Mn, Mg, Zn and Si. The Al alloy can be used, so that the strength of the metal is drastically increased and, therefore, the thickness of the metal container decreases. As a result, it is possible to obtain a thin, light battery with high output performance and excellent heat dissipation.

[0174] It can be used as a laminated film, for example, a multilayer film with resin films and a metallic film sandwiched between the resin films, etc. Preferably, the metal film is made from aluminum foil or aluminum alloy foil to reduce weight. Polymers such as propylene (PP), polyethylene (PE), nylon and polyethylene terephthalate (PET) can be used as resin. Furthermore, a thickness of the laminated film is preferably 0.2 mm or less. The Al foil preferably has a purity of 99.5% or more if the Al foil is used as a metal film. The laminated film can be heat sealed or molded to the shape of the container.

[0175] The shape of the container is not particularly limited and can be, for example, flat, square, cylindrical, coin or button shaped. The container depends on the size of the battery and can be a container for a compact battery fitted on a mobile electronic device or the like and a container for a large battery fitted on a two- or four-wheeled automobile or the like.

(6) Negative electrode terminal

[0176] The negative electrode terminal can be made of stable material in a voltage range ranging from 1.0 V (vs. Li/Li+) to 3.0 V (vs. Li/Li+) based on the oxi-reduction potential of lithium and with electrical conductivity. Specific examples of material for the negative electrode termnial are copper, nickel, stainless steel, aluminum, an aluminum alloy with at least one element selected from Mg, Ti, Zn, Mn, Fe, Cu and Si. It is It is preferable that aluminum or an aluminum alloy be used as the material for the negative electrode terminal. The negative electrode terminal is preferably made of the same material as the negative electrode current collector, in order to reduce the contact resistance with the negative electrode current collector.

(7) Positive electrode terminal

[0177] The positive electrode terminal can be made of stable material in a voltage range ranging from 3.0 V (vs. Li/Li+) to 4.5 V (vs. Li/Li+) based on the oxi-reduction potential of lithium and with electrical conductivity. Specific examples of material for the positive electrode terminal are copper, nickel, stainless steel, aluminum, an aluminum alloy with at least one element selected from Mg, Ti, Zn, Mn, Fe, Cu and Si. It is It is preferable that aluminum or an aluminum alloy be used as the material for the positive electrode terminal. The positive electrode terminal is preferably made of the same material as the positive electrode current collector, in order to reduce the contact resistance with the positive electrode current collector.

[Method for measuring the minimum thickness and average thickness of the Li conductive layer.]

[0178] The minimum thickness of the Li conductive layer in the battery is determined as follows. First, a composite electrode is removed from the battery as previously described. Then, the removed composite electrode is cut with the aid of a FIF (FIB) as previously described. Consequently, it is possible to obtain a straight section in the stacking direction of the positive electrode active material-containing layer/Li conductive layer/negative electrode active material-containing layer. All layers included in the cut surface obtained in this way are measured by SEM (SEM). The magnitude of observation (the increase) at this point is preferably 20,000 times. All layers included in the straight section in the stacking direction are observed and the thickness of the thinnest region of the Li conductive layer is defined as the thickness of a region with the smallest thickness of the electrolytic layer.

[0179] The average thickness of the Li conductive layer is determined as described below. First, as already described, the cutting surface of the composite electrode is obtained. Then, the straight section is analyzed as a whole, from one end to the other, along the entire surface, with the aid of SEM (SEM) with the same observation magnitude (magnification). This observation magnitude (increase) should preferably be 20,000 times. From the image obtained through SEM (SEM), the area of the diagonal straight section of the Li conductive layer is obtained. The area value is divided by the length of the Li conductive layer, measured in a direction perpendicular to the electrode stacking direction , that is, the length of the incision on the surface of the composite electrode, to find the quotient. By converting this quotient into the increase used, the average thickness can be obtained.

[0180] In the following, a specific example of a secondary battery in accordance with the second embodiment will be described using the figures as reference.

[0181] First, a composite electrode of a first example that can be comprised in a secondary battery in accordance with the second embodiment will be described with reference to Figure 4.

[0182] Figure 4 is a schematic cross-sectional view of a first example of a composite electrode that can be comprised in a secondary battery in accordance with the second embodiment.

[0183] A composite electrode 10A illustrated in Figure 4 comprises a layer containing positive electrode active material 5b, a Li conductive layer 4, a layer containing negative electrode active material 3b and two current collectors 8. As illustrated, on the electrode compound 10A, the Li conductive layer 4 is provided between the positive electrode active material-containing layer 5b and the negative electrode active material-containing layer 3b. The Li conductive layer 4 is in contact with a surface of the layer containing positive electrode active material 5b and a surface of the layer containing active material of negative electrode 3b. A surface of the layer containing positive electrode active material 5b that is not in contact with the Li conductive layer 4 is in contact with a current collector 8. Similarly, a surface of the layer containing active material of negative electrode 3b that is not in contact with the Li conductive layer 4 is in contact with the other current collector 8. Thus, the composite electrode 10A has a structure in which a current collector 8, the Li conductive layer 4, the layer containing active material of positive electrode 5b and another current collector 8 are stacked in this order. In other words, the composite electrode 10A, as illustrated in Figure 4, is an electrode body comprising an electrode assembly configuration 12, comprising the positive electrode active material-containing layer 5b, the negative electrode active material-containing layer 3b and Li conductive layer provided between them.

[0184] Next, there is described, with reference to Figure 5, a second example of a composite electrode that can be comprised in a secondary battery in accordance with the second embodiment.

[0185] Figure 5 is a schematic view of the cross-section of a composite electrode that may be included in a secondary battery in accordance with the second embodiment.

[0186] A composite electrode 10B illustrated in Figure 5 comprises, for example, four electrodes 11 with a bipolar structure. As illustrated in Figure 5, each electrode 11 comprises a current collector 8, a positive electrode active material-containing layer 5b formed on one surface of the current collector 8, and a negative electrode active material-containing layer 3b formed on the other surface of the collector. current 8. As is illustrated in Figure 5, these electrodes 11 are provided so that the layer containing positive electrode active material 5b of one electrode 11 faces the layer containing active material of negative electrode 3b of another electrode 11 with the Li 4 conductive layer sandwiched between them.

[0187] The composite electrode 10B also comprises the other two Li conductive layers 4, the other two current collectors 8, the other layer containing positive electrode active material 5b and the other layer containing negative electrode active material 4b. As illustrated in Figure 5, a positive electrode active material-containing layer 5b faces the negative electrode active material-containing layer 3b of the electrodes 11 located on the uppermost layer of the electrode stack 11 with a Li conductive layer 4 sandwiched between they. A surface of the layer containing negative electrode active material 3b that is not in contact with the Li conductive layer 4, is in contact with a current collector 8. A layer containing negative electrode active material 3b faces the layer containing positive electrode active material 5b of the electrode 11 located in the lowest layer of the electrode stack 11 with a Li conductive layer 4 sandwiched between them. A surface of the layer containing negative electrode active material 3b which is not in contact with the Li conductive layer 4, is in contact with a current collector 8.

[0188] A composite electrode that can be comprised in a secondary battery in accordance with the second embodiment can be tuned by establishing close contact between the positive electrode active material-containing layer and the Li conductive layer and between the material-containing layer Therefore, in the secondary battery according to the second embodiment, a large number of sets composed of a layer containing positive electrode active material, a layer containing positive electrode active material, and a layer containing positive electrode active material can be stacked. negative and a Li conductive layer sandwiched between them. Consequently, it is possible to provide a thin secondary battery, which requires less space and has a large number of charge and discharge cycles, good thermal stability and electrochemical stability. The composite electrode 10B in accordance with the example illustrated in Figure 5 comprises five groups of electrode arrays 12, each comprising the positive electrode active material-containing layer 5b, the negative electrode active material-containing layer 3b and the Li conductive layer 3b. sandwiched between them. However, the number of electrode arrays 12 can be determined according to battery design and size.

[0189] Figure 6 illustrates a schematic view of the straight section of a secondary battery in accordance with the embodiment.

[0190] As illustrated in Figure 6, a secondary battery 100 comprises a composite electrode 10c accommodated in a container 2. The composite electrode 10c, illustrated in Figure 6, has a similar structure to the composite electrode 10B, illustrated in Figure 5. A positive electrode guide connector 8A is provided at one end of the current collector 8 located on the upper layer of the composite electrode 10c. On the other hand, a negative electrode guide connector 8B is provided at one end of the current collector 8 located on the lowermost layer of the composite electrode 10C. A negative electrode terminal and a positive electrode terminal (both are not illustrated) are connected to the positive electrode guide connector 8A and the negative electrode guide connector 8B, respectively, and the negative electrode terminal and the positive electrode terminal connect to each other. extend outside the container.

[0191] In Figure 6, as well as the composite electrode 10B illustrated in Figure 5, a secondary battery 100 comprising a composite electrode 10C, this comprising five groups of electrode assemblies, these comprising a layer containing positive electrode active material 5b, a layer containing negative electrode active material 3b sandwiched between them, is illustrated as an example. However, the secondary battery according to the second embodiment may comprise electrode arrays greater than 5 in number, for example, a composite electrode comprising a group of electrode arrays such as the composite electrode 10A illustrated in Figure 4 or may comprise a composite electrode , this comprising two or more groups of electrode arrays.

[0192] Next, an example method of producing a composite electrode comprising a layer containing positive electrode active material, a layer containing negative electrode active material and a Li conductive layer sandwiched between them will be described with reference to the schematics.

[0193] Figure 7 is a schematic view illustrating a step of a method of producing a third example of a composite electrode that can be comprised in a secondary battery according to the second embodiment. Figure 8 is a schematic view illustrating the step following the production step illustrated in Figure 7. Figure 9 is a schematic cross-sectional view of the composite electrode produced by the production method illustrated in Figures 7 and 8.

[0194] In a specific example described here, a method of forming the Li 4 conductive layer on a layer containing positive electrode active material 5b will be described, but a method of forming the Li 4 conductive layer, which can be understood in a secondary battery in accordance with a second embodiment, is not limited to what is described here.

[0195] First, a mixture of inorganic solid particles 91 is dispersed in a solution containing a binder so as to prepare a liquid binder dispersion comprising the mixture of inorganic solid particles 91. Here, any of the types of binders already cited. The mixture of inorganic solid particles 91 is a mixture of inorganic solid particles comprised in the electrolyte composed in accordance with the first embodiment. Then, this liquid binder-dispersion is applied onto the layer containing positive electrode active material 5b. Next, a solvent is evaporated from the applied film. Consequently, as illustrated in Figure 7, the mixture of inorganic solid particles 91 is provided on the positive electrode active material-containing layer 5b.

[0196] Next, a coating material containing a non-aqueous electrolyte 92 or a non-aqueous electrolyte precursor 92 is distributed over the layer containing positive electrode active material 5b. By way of example, the coating material contains components for gelatinizing the non-aqueous electrolyte coating material, such as a non-aqueous electrolyte, a binder and a polymerization initiator, and is distributed over the layer containing positive electrode active material 5b , so as to form a coated film. By heating this coated film film, a composite electrolyte 9 comprising a non-aqueous solid polymer or gel polymer electrolyte and a mixture of inorganic solid particles 91 is obtained, as illustrated in Figure 8.

[0197] Subsequently, the layer containing positive electrode active material 5b and the layer containing negative electrode active material 4b are arranged so that they are facing each other and compressed against each other. Accordingly, as illustrated in Figure 9, an electrode array 12 comprising the positive electrode active material-containing layer 5b, the negative electrode active material-containing layer 3b and the Li conductive layer 4 sandwiched between them and comprising the composite electrolyte 9 is obtained.

[0198] As can be seen, the method for forming the Li 4 conductive layer on the positive electrode active material-containing layer 5b has already been described, but the Li 4 conductive layer can be formed on the negative electrode active material-containing layer 3b. Alternatively, the Li conductive layer 4 can be formed on the surfaces of both the positive electrode active material-containing layer 5b and the negative electrode active material-containing layer 3b.

[0199] Here, when the negative electrode active material-containing layer 3b is pressed against the Li conductive layer 4 provided on the positive electrode active material-containing layer 5b, specifically when the non-aqueous electrolyte 92 comprises a gel polymer electrolyte , the composite electrolyte 9 enters or penetrates the recesses of the irregularities in the surfaces of the positive electrode active material-containing layer 5b and negative electrode active material-containing layer 3b, particularly in the irregularities of the active materials that may be present on the surfaces of these active material-containing layers of electrode. Consequently, the positive electrode active material containing layer 5b, the negative electrode active material containing layer 3b and the Li conductive layer 4 can be firmly adhered to each other along respective irregularities. Therefore, in the electrode array 12 thus obtained, the Li conductive layer 4 can increase the contact areas with the positive electrode active material-containing layer 5b and the negative electrode active material-containing layer 3b at the interface with the Li-electrode active material-containing layer 3b. positive electrode 5b and at the interface with the layer containing active material of negative electrode 3b. Therefore, the Li conductive layer 4 can homogeneously exchange Li ions with each of the layers containing positive electrode active material 5b and the layer containing negative electrode active material 3b. Furthermore, since the Li conductive layer 4 is in close contact with the positive electrode active material-containing layer 5b and the negative electrode active material-containing layer 3b, the thickness of the Li conductive layer can also be reduced.

[0200] Furthermore, when the non-aqueous electrolyte 92 comprises a solid polymer electrolyte, it is preferable to obtain a composite electrode with the following procedure, for example. First, the liquid binder dispersion comprising the mixture of inorganic solid particles 91, already described, is applied to a layer containing active material. Then, a solvent is evaporated from the coated film. Consequently, the mixture of inorganic solid particles 91 is provided on a layer containing active material. Then, the coating material containing a non-aqueous electrolyte precursor is applied over a layer containing active material on which the mixture of inorganic solid particles 91 is provided. Here, it is preferable to use a coating material with high fluidity. Consequently, the coating material can be caused to enter the recesses of the irregularity in the surface of the active material-containing layer and, as a result, a coated film with a more uniform thickness is obtained. When the fluidity of the coating material is very high, a method such as spraying can be used. Next, the coated film is heated. The degree of heating at this point is determined such that the non-aqueous electrolyte precursor is not completely solidified. Subsequently, the positive electrode active material-containing layer 5b and negative electrode active material-containing layer 3b are arranged to face each other and compressed. In this way, it is possible to obtain a state in which the non-aqueous electrolyte precursor penetrates the recesses of the surface irregularities of both layers containing active material. Then, the coated film containing the non-aqueous electrolyte precursor is heated further. Thus, the electrode array 12 comprising the positive electrode active material-containing layer 5b, the negative electrode active material-containing layer 3b and the Li conductive layer 4 sandwiched between them and comprising the composite electrolyte 9 is obtained. The composite electrolyte 9 may comprise the mixture of inorganic solid particles 91 and the non-aqueous electrolyte 92 comprising the solid polymeric electrolyte. The mixture of inorganic solid particles 91 can be provided in both the positive electrode active material-containing layer 5b and the negative electrode active material-containing layer 3b and the non-aqueous electrolyte path-containing material can be applied thereafter.

[0201] According to the method described above, by way of example, the thickness of the Li 4 conductive layer can be regulated by adapting the amount of solid content in the liquid dispersion containing the mixture of inorganic solid particles 91 and the amount applied of non-aqueous electrolyte 92 or coating material containing the precursor of non-aqueous electrolyte 92, among others.

[0202] Alternatively, the Li conductive layer can also be formed by a method comprising injecting a non-aqueous electrolyte between the layer containing positive electrode active material 5b and the layer containing negative electrode active material 3b. Specifically, by way of example, the method follows as now described. First, according to the same procedure described above, the inorganic solid particles 91 are provided on either surface of the positive electrode active material-containing layer 5b and the surface of the negative electrode active material-containing layer 3b. Next, the layer containing positive electrode active material 5b and the layer containing negative electrode active material 3b are arranged at a constant distance from each other (a distance established for the thickness of the Li conductive layer 4). Next, the coating material containing the non-aqueous electrolyte 92, or the non-aqueous electrolyte precursor 92, is injected between the layer containing positive electrode active material 5b and the layer containing negative electrode active material 3b. In this way, the coating material also penetrates the small recesses of the surface irregularities of both the layer containing positive electrode active material 5b and the layer containing active material negative electrode 3b. Then, when carrying out the above procedure, the electrode assembly 12 comprising the positive electrode active material-containing layer 5b, the negative electrode active material-containing layer 3b, the Li conductive layer 4 provided between them and comprising the composite electrolyte 9 is obtained.

[0203] In the above description, the secondary battery comprising the electrode with bipolar structure was given as an example, but the secondary battery according to the second embodiment is not limited to the secondary battery comprising electrode with bipolar structure. The secondary battery according to the second embodiment may have a structure illustrated in Figures 10 and 11, for example.

[0204] Figure 10 is a schematic cross-sectional view illustrating a second example of a secondary battery according to the second embodiment. Figure 11 is an enlarged cross-sectional view of a part B of the secondary battery illustrated in Figure 10.

[0205] A secondary battery 100 illustrated in Figures 10 and 11 comprises a bag-type container 2 illustrated in Figures 10 and 11. The electrode group 1 is installed in the container 2.

[0206] The bag-type container 2 is made of laminated film comprising two layers of resin and a metallic layer sandwiched between them.

[0207] As illustrated in Figure 10, electrode group 1 is a flat coil-type electrode group. As illustrated in Figure 11, the flat coil electrode group 1 comprises a negative electrode 3, a Li conductive layer 4, and a positive electrode 5. The Li conductive layer is sandwiched between the negative electrode 3 and the positive electrode 5. .

[0208] The negative electrode 3 comprises a negative electrode current collector 3a a layer containing negative electrode active material 3b. As illustrated in Figure 11, in the part of the negative electrode 3 located in the outermost layer of the coil-type electrode group 1, the layer containing negative electrode active material 3b is formed only on the inner side of the surface of the negative electrode current collector 3a. The other part of the negative electrode 3 comprises the negative electrode active material-containing layer 3b formed on each of the current collector surfaces of the negative electrode 3a.

[0209] The positive electrode 5 comprises a positive electrode current collector 5a and a layer containing positive electrode active material 5b formed on each of the surfaces.

[0210] The Li 4 conductive layer comprises the electrolyte composed according to the first embodiment, as well as the Li 4 conductive layer described above.

[0211] As illustrated in Figure 10, a negative electrode terminal 6 and a positive electrode terminal 7 are located in the vicinity of the peripheral layer of the coil-type electrode group 1. The negative electrode terminal 6 is connected to a part of the negative electrode 3a current collector from negative electrode 3 located in the outermost layer. The positive electrode terminal 7 is connected to the positive electrode current collector 5a of the positive electrode 5 located in the outermost layer. The negative electrode terminal 6 and the positive electrode terminal 7 reach the outside through an opening in the bag-type container 2. The bag-type container 2 is heat sealed with a layer of thermoplastic resin provided on the inner surface of the container.

[0212] The secondary battery according to the second embodiment may comprise a plurality of positive electrodes and a plurality of negative electrodes. These may be alternatively stacked such that the Li conductive layer is provided between the layers containing positive electrode active material and the layer containing negative electrode active material. In conclusion, the secondary battery according to the second embodiment may comprise a stacked type electrode group.

[0213] Since the secondary battery according to the second embodiment comprises the electrolyte composed according to the first embodiment, the secondary battery according to the second embodiment can exhibit excellent durability and excellent output performance in low temperature environments.

(Third embodiment)

[0214] According to a third embodiment, a battery module is presented. The battery module according to the third embodiment comprises secondary batteries, all according to the second embodiment.

[0215] In the battery module according to the third embodiment, each of the individual batteries may be electrically connected in series, in parallel or a combination of series and parallel connections.

[0216] Below, an example of a battery module in accordance with the third embodiment is described using the diagrams (Figures) as reference.

[0217] Figure 12 is a schematic perspective view illustrating an example of a battery module according to the third embodiment. A battery module 200 illustrated in Figure 12 comprises five individual batteries 100, four electrical buses 21, a positive electrode guide connector 22, and a negative electrode guide connector 23. Each of the five individual batteries 100 is a secondary battery in accordance with the second embodiment.

[0218] Each electrical bus 21 connects a negative electrode terminal 6 of an individual battery 100 to a positive electrode terminal 7 of a neighboring individual battery 100. The five individual batteries 100 are thus connected in series across the four electrical buses 21. Thus, the battery module 200 illustrated in Figure 12 is a five-connect battery module in series.

[0219] As illustrated in Figure 12, the positive electrode terminal 7 of the individual battery 100 located at the left end of the group of five individual batteries 100 is connected to the electrode positive side guide connector 22 for an external connection. Furthermore, the negative electrode terminal 6 of the individual battery 100 located at the right end of the group of five individual batteries 100 is connected to the negative side guide connector of the electrode 23 for an external connection.

[0220] The battery module according to the third embodiment comprises the secondary battery according to the second embodiment. Therefore, the battery module in accordance with the third embodiment can exhibit excellent durability and excellent output performance in low temperature environments.

(Fourth realization)

[0221] According to the fourth embodiment, a battery pack is presented. The battery pack comprises a battery module in accordance with the third embodiment. The battery pack may comprise an individual secondary battery in accordance with the second embodiment rather than a battery module in accordance with the third embodiment.

[0222] The battery pack in accordance with the fourth embodiment may also comprise a protection circuit. The protection circuit's function is to control the charging and discharging of the secondary battery. Alternatively, a circuit comprised in equipment (e.g., electronic devices, vehicles, etc.), in which the battery pack functions as a power source, can be used as a protection circuit for the battery pack.

[0223] Additionally, the battery pack may also comprise an external power distribution terminal. The external power distribution terminal is configured to allow current to exit the secondary battery and/or allow current to enter the secondary battery. In other words, when the battery pack is used as a power source, current is supplied externally through the external power distribution terminal. Similarly, when the battery pack is charged, charging current (comprising regenerative energy arising from the kinetic energy of vehicles, such as automobiles) is supplied to the battery pack through the external power distribution terminal.

[0224] Below, a battery pack is described, by way of example, in accordance with the embodiment, with the diagrams as references.

[0225] Figure 13 is a schematic exploded perspective view illustrating an example of a battery pack according to a fourth embodiment. Figure 14 is a block diagram illustrating an electrical circuit of the battery pack of Figure 13.

[0226] A battery pack 300, illustrated in Figures 13 and 14, comprises a frame 31, a cover 32, protective plates 33, a battery module 200, a printed wiring board 34, a wiring 35, a insulation (not illustrated).

[0227] The frame 31 is designed to receive the protective plates 33, the battery module 200, the printed wiring board 34 and the wiring 35. The cover 32 is located on the frame 31 to receive the battery module 200, between others. The frame 31 and cover 32 have an opening, a connecting terminal, or other similar structure (not illustrated), which can be connected to an external device.

[0228] Protection plates 33 are distributed both on the inner surfaces along the larger side of the frame 31 and on an inner surface that faces the printed wiring board 34 through the battery module 200, along the smaller side. of the framework 31. The protection plates 33 are made of rubber or resin, for example.

[0229] The battery module 200 comprises individual batteries 100, a positive electrode guide connector 22, a negative electrode guide connector 23, and an adhesive tape 24. The battery module 200 may be a single individual battery 100 .

[0230] The individual batteries 100 have the structure illustrated in Figures 10 and 11. At least one of the individual batteries 100 is a secondary battery in accordance with the second embodiment. The individual batteries 21 are stacked so that the positive electrode terminals 6 and the outwardly extending negative electrode terminals are arranged in the same direction. The individual batteries 100 are connected in series, as illustrated in Figure 14. The individual batteries 100 may be connected in parallel or in a combination of series connection and parallel connection. If the plurality of individual batteries 100 are connected in parallel, the battery capacity increases compared to series connection.

[0231] Adhesive tape 24 secures the individual batteries 100. Instead of adhesive tape 24, a heat-shrinkable tape can be used to secure the individual batteries 100. In this case, protective sheets are provided On both sides of the battery module 200, heat-shrinkable tape is wrapped around the battery module and the heat-shrinkable tape is heat-shrinkable to package the individual batteries.

[0232] One end of the positive electrode guide connector 22 is connected to the positive electrode terminal 7 of the individual battery 100 located in the lower end layer of the individual battery stack 100. One end of the negative electrode guide connector 23 is connected to the negative electrode terminal 6 of the individual battery 100 of the upper end layer of the individual battery stack 100.

[0233] A printed wiring board 34 is provided with a positive electrode side connector 341, a negative electrode connector 342, a thermistor 343, a protection circuit 344, wiring 345 and 346, an external power distribution terminal 347, a positive-side wire 348a and a negative-side wire 348b. One of the main surfaces of the printed wiring board 34 faces the side plane of the battery module 200 onto which the negative electrode terminals 6 and positive electrode 7 are extended. The insulation board (not shown) is sandwiched between the printed wiring board 34 and the battery module 200.

[0234] The connector on the positive side of electrode 341 is provided as a hole. The other end of the electrode positive side guide connector 22 is inserted into the hole so as to electrically connect the electrode positive side connector 341 and the electrode positive side guide connector 22. The electrode negative side connector 342 is provided as an orifice. The other end of the electrode negative side guide connector 23 is inserted into the hole so as to electrically connect the electrode negative side connector 342 and the electrode negative side guide connector 23.

[0235] Thermistor 343 is affixed to one of the main surfaces of the printed wiring board 34. Thermistor 343 senses the temperatures of each of the individual batteries 100 and transmits the detection signal to the protection circuit 344.

[0236] The external power distribution terminal 347 is affixed to the other main surface of the printed wiring board 34. The external power distribution terminal 347 is electrically connected to a device exterior to the battery pack 300.

[0237] The protection circuit 344 is affixed to the other main surface of the printed wiring board 34. The protection circuit 344 is connected to the external power distribution terminal 347 by a positive side wire 348a. The protection circuit 344 is connected to the external power distribution terminal 347 by a negative side wire 384b. Additionally, the protection circuit 344 is electrically connected to the electrode positive side connector 341 by wiring 345. The protection circuit 344 is electrically connected to the electrode negative side connector 342 by wiring 346. Finally, the protection circuit 344 is electrically connected to each of the individual batteries 100 by wiring 35.

[0238] Protection circuit 344 controls the charging and discharging of the plurality of individual batteries 100. Protection circuit 344 is also configured to sever the electrical connection between protection circuit 344 and the external power distribution terminal to a device external, based on signals detected by thermistor 343 or signals detected and transmitted from each individual battery 100 or battery module 200.

[0239] An example of a detection signal transmitted by thermistor 343 is a signal representing the detection of the temperature of an individual battery 100 is the predetermined temperature or is above that value. An example of a detection signal transmitted from each individual battery 100 or battery module 200 is a signal representing overload, overdischarge, and overcurrent detection of the individual battery 100. If overload or other such effect is detected in any of the individual batteries 100, the battery voltage can be detected or the potentials of the positive or negative electrodes can be detected. In this case, a lithium electrode to be used as a reference pole is inserted into each individual battery 100.

[0240] Note that it is possible to use a circuit comprised in a device (e.g., an electronic device or an automobile) that uses the battery pack 300 as a power source as a protection circuit 344.

[0241] Such a battery pack 300 is used, for example, in an application such that the battery pack 300 is necessary for optimal life cycle performance when the output is a very high current. More specifically, for example, the battery pack 300 is used as a power source for an electronic device, a stationary battery, or a battery on board a vehicle or railway vehicle. An example of electronic equipment is a digital camera. It is particularly preferred that the battery pack 300 is used as an on-board battery.

[0242] As already described, the battery pack 300 comprises an external power distribution terminal 347. Thus, the battery pack 300 can transmit current from the battery module 200 to an external device and receive current from an external device to the battery module 200 through the external power distribution terminal 347. In other words, when using the battery pack 300 as a power source, current from the battery module 200 is supplied to the external device through the external terminal power distribution terminal 347. When charging the battery pack 330, a charging current from an external device is supplied to the battery pack 300 through an external power distribution terminal 347. If the battery pack 300 is used As an on-board battery, the vehicle's kinetic energy converted into regeneration energy can be used as the charging current of an external device.

[0243] Note that battery pack 300 may comprise battery module 200. In this case, battery modules 200 may be connected in series, in parallel, or in a combination of series and parallel connections. Printed wiring board 34 and wiring 35 can be omitted. In this case, the electrode positive side guide connector 22 and the electrode negative side guide connector 23 can be used as the external power distribution terminal.

[0244] The battery pack according to the fourth embodiment comprises the secondary battery according to the second embodiment or the battery module according to the third embodiment. Therefore, the battery pack in accordance with the fourth embodiment can have great lifespan and great output performance in low temperature environments.

(Fifth implementation)

[0245] According to a fifth embodiment, a vehicle is presented. The battery pack in accordance with the fourth embodiment is installed in the vehicle.

[0246] In the vehicle according to the fifth embodiment, the battery pack is configured to convert the vehicle's kinetic energy into regeneration energy, for example.

[0247] Examples of vehicles in accordance with the fifth embodiment are hybrid electric cars with two or four wheels, electric cars with two or four wheels, electro-assisted bicycles and railway vehicles.

[0248] In the vehicle according to the fifth embodiment, the position in which the battery pack is installed is not unique. For example, in the case where the battery pack is installed in an automobile, the battery pack may be installed in the engine, in the rear parts of the vehicle or under the seats.

[0249] An example of a vehicle in accordance with the fifth embodiment is explained below, with reference to the diagrams.

[0250] Figure 15 is a schematic sectional view illustrating an example of a vehicle according to a fifth embodiment.

[0251] A vehicle 400, illustrated in Figure 15, comprises a vehicle body 40 and a battery pack 300 in accordance with the fourth embodiment.

[0252] Vehicle 400, illustrated in Figure 15, is a four-wheeled automobile. For example, two- or four-wheel electric hybrid automobiles, electro-assisted bicycles and railway vehicles may also be used as the vehicle 400.

[0253] This vehicle 400 may have a plurality of battery packs 300 installed. In this case, the battery packs 300 may be connected in series, in parallel, or in a combination of series and parallel connections.

[0254] The battery pack 300 is installed in the engine compartment located at the front of the vehicle body 40. The installation location of the battery pack 300 is not limited to that point, however. The battery pack 300 may be installed in the rear portions of the vehicle body 40 or under the seat. The battery pack 300 can be used as a power source for the vehicle 300. The battery pack 300 can also convert the kinetic energy of the vehicle 400 into regenerative energy.

[0255] Next, an aspect of the vehicle in accordance with the fifth embodiment is explained, with reference to Figure 16.

[0256] Figure 16 is a schematic view illustrating another example of a vehicle according to the fifth embodiment. A vehicle 400, illustrated in Figure 16, is an electric automobile.

[0257] The vehicle 400, illustrated in Figure 16, comprises a vehicle body 40, a vehicle power source 41, an electrical control unit 42 (ECU), which is a master controller of the vehicle power source 41, an external power connection terminal 43, an inverter 44 and a steering motor 45.

[0258] Vehicle 400 comprises the power source of vehicle 41 in the engine compartment, in the rear parts of the automobile body or under the seats, for example. In Figure 16, the installation position of the power source 41 of the vehicle 400 is schematically illustrated.

[0259] The vehicle power source 41 comprises a plurality of battery packs (three, in this example) 300a, 300b, and 300c, a battery management unit 411 (BMU), and a communication bar 412.

[0260] The three battery packs 300a, 300b and 300c are connected in series. The battery pack 300a comprises a battery module 200a and a battery module monitoring unit (VTM: “voltage temperature monitoring”) 301a. The battery pack 300b comprises a battery module 200b and a battery module monitoring unit 301b. The 300c battery pack comprises a 200c battery module and a 301c battery module monitoring unit. Battery packs 300a, 300b and 300c can be removed independently and can be exchanged for different types of battery packs 300.

[0261] Each of battery modules 200a to 200c comprises a plurality of individual batteries connected in series. At least one of the individual batteries is a secondary battery in accordance with the second embodiment. Each of the battery modules 200a to 200c charges and discharges via a positive electrode terminal 413 and a negative electrode terminal 414.

[0262] In order to collect data regarding the security of the vehicle's power source 41, the battery management unit 411 communicates with the battery module monitoring units 301a to 301c and collects various data, such as voltage or temperature of individual batteries 100 comprised in battery modules 200a to 200c comprised in vehicle power source 41.

[0263] Communication bus 412 is connected between battery management unit 411 and battery module monitoring units 301a to 301c. The communication bus 412 is configured so that multiple nodes (battery management unit and one or more battery module monitoring units) share a group of communication lines. The communication bus 412 is, for example, a configuration bus with configuration based on a CAN (Control Area Network) network standard.

[0264] Battery module monitoring units 301a to 301c measure a voltage and temperature of each individual battery in battery modules 200a to 200c, based on commands from battery management unit 411. It is possible, however, to measure the temperature only at different points on each battery module and, therefore, it is unnecessary to measure the temperature of all individual batteries.

[0265] The vehicle power source 41 may also have an electromagnetic contact (e.g., a distribution unit 415 illustrated in Figure 16) to change the connection between the positive electrode terminal 413 and the negative electrode terminal 414. distribution unit 415 comprises a pre-charge circuit breaker (not illustrated), which is turned on when battery modules 200a to 200c are charged, and the main circuit breaker (not illustrated), which is turned on when battery output is supplied to a component. The pre-charge circuit breaker and main circuit breaker include a relay (not shown), which is turned on or off based on a signal transmitted to a coil located near the breakers.

[0266] Inverter 44 converts a direct voltage/current to a three-phase alternating high voltage/current (AC) to drive the motor. The three-phase output terminal(s) of the inverter 44 are connected to each of the three-phase input terminals of the motor 45. The inverter 44 controls an output voltage based on signals control unit of the battery management unit 411 or the vehicle ECU 42, which controls the entire operation of the vehicle.

[0267] Motor 45 is driven by electrical energy provided by inverter 44. Rotation is transferred to a shaft and steering wheels W via a differential transmission unit, for example.

[0268] Vehicle 400 also comprises a regenerative braking mechanism, although not illustrated. The regenerative braking mechanism drives the engine 45 when the vehicle 400 is braked and converts kinetic energy into regenerative energy in the form of electrical energy. The regenerative energy, recovered in the regenerative braking mechanism, is supplied to inverter 44 and converted into direct current. Direct current is supplied to the vehicle power supply 41.

[0269] One terminal of an L1 connection line is connected, via a current detector (not illustrated) in the battery management unit 411, to the negative electrode terminal 414 of the vehicle power source 41. The other terminal of the connection line L1 is connected to a negative electrode input terminal of the inverter 44.

[0270] One terminal of a connection line L2 is connected, via a distribution unit 415, to the positive electrode terminal 413 of the vehicle power source 41. The other terminal of the connection line L2 is connected to the input terminal of the positive electrode of inverter 44.

[0271] External terminal 43 is connected to battery management unit 411. External terminal 43 may connect, for example, to an external power source.

[0272] The vehicle ECU 42 cooperatively controls the battery management unit 411, along with other units, in response to a driver's operating inputs and thereby performs management of the entire vehicle. Data regarding the security of the vehicle's power source 41, such as the remaining capacity of the vehicle's power source 41, are transmitted between the battery management unit 411 and the vehicle's ECU 42 via the communication lines.

[0273] The vehicle according to the fifth embodiment comprises the battery pack according to the fourth embodiment. Thus, the vehicle in accordance with the fifth embodiment can present excellent durability and excellent output performance in environments with low temperatures.

[Examples]

[0274] From now on, the previous embodiments will be described in greater detail through examples. In the following examples, when the thickness of the Li conductive layer was determined, the Li conductive layer was sliced with a FIF (FIB) and the cross section of the composite electrolyte was analyzed by SEM. The magnification used was 20,000 times.

(Example 1)

[0275] In example 1, an electrode assembly of example 1 was produced as follows.

(Positive electrode production)

[0276] Particles of a lithium-containing oxide composite with a formula LiMn0.85Fe0.1Mg0.05PO4 and with an olivine-type crystalline structure were provided as a positive electrode active material. Fine carbon particles with an average particle size of 5 nm were adhered to the surface of the particles. The adhesion percentage was 0.1% by weight. The particles provided were primary particles with a primary particle size of 50 nm.

[0277] A vapor-grown carbon fiber with a diameter of 0.1 μm and a graphite powder were provided as conductive agents. Polyvinylidene fluoride (PVdF) was provided as a binder.

[0278] The positive electrode active material particles, carbon fiber, graphite powder and PVdF were mixed in the proportion of 87% by weight: 3% by weight: 5% by weight: 5% by weight, respectively . This mixture was dispersed in an N-methylpyrrolidone (NMP) solvent in order to prepare a positive electrode suspension. Then, the positive electrode suspension was applied to each of the surfaces of an aluminum alloy sheet (99% purity) with a thickness of 15 μm so as to establish a coated film, and then the coated film was dried. Then, the coated film was compressed. In this way, a positive electrode comprising a current collector and a layer containing positive electrode active material formed on each surface of the current collector was obtained. The amount of suspension applied and the compression pressure were determined such that the thickness of the layer containing positive electrode active material formed on a surface of the current collector was 67 μm and the density of the layer containing positive electrode active material formed on a current collector surface was 2.2 g/cm3.

(Negative electrode production)

[0279] Lithium titanate particles with a formula of Li4Ti5O12 were used as the negative electrode active material. The primary particle size of lithium titanate particles was 0.6 μm. The BET specific surface area of the lithium titanate particles was 10m2/g. A graphite powder with an average particle size of 6 μm was provided as a conducting agent. PVdF was used as a ligand.

[0280] Then, the negative electrode active material particles, graphite powder and PVdF were mixed at a ratio of 95% weight: 3% weight: 2% weight, respectively. This mixture was dispersed in an N-methylpyrrolidone (NMP) solvent. The dispersion obtained was stirred in a ball mill, at a rotation speed of 1000 rpm, for two hours (2h). A negative electrode suspension was thus obtained.

[0281] The negative electrode suspension obtained was applied to an aluminum alloy sheet (purity 99.3%) with a thickness of 15 μm in order to obtain a coated film, and then this coated film was dried. Then, the dried coated film was subjected to compression under heat. Thus, a negative electrode comprising a current collector and a layer containing negative electrode active material formed on each surface of the current collector was obtained. A negative electrode was produced through this process. The amount of suspension applied and the compression pressure were determined so that the thickness of the layer containing negative electrode active material formed on a surface of the current collector was 59 μm and the density of the layer containing negative electrode active material formed on a current collector surface was 2.2 g/cm3. The porosity of the layer containing negative electrode active material was 35%.

(Preparation of inorganic solid particle mixture)

[0282] Particles with a garnet-type crystalline structure with a chemical formula Li7La3Zr2O12 (LLZ) were used as the first inorganic solid particles. The particles had a d50 (average primary particle size) of 0.35 μm, a d10 of 0.12 μm, and a d90 1.61 μm on a cumulative frequency distribution curve. The particles were prepared by the following method. First, LLZ particles were obtained. These were divided equally into three groups. Particles from a first group were crushed for 1 hour, at 140 rpm, using zirconia spheres with a diameter of 10 mmΦ. Particles from a second group were crushed for 3 hours, at 180 rpm, using zirconia spheres with a diameter of 1 mmΦ. Particles from a third group were dispersed in isopropyl alcohol and crushed in a wet bead mill using zirconia beads with a diameter of 0.3 mmΦ at a peripheral speed of 10 m/s. The crushed particles from these groups were mixed to form the first mixture of inorganic solid particles. The average particle size, BET specific surface area and Li ion conductivity at 25°C of the first inorganic solid particles are listed in Table 1.

[0283] On the other hand, alumina particles with a chemical formula of Al2O3 were used as second inorganic solid particles. The particles had a d50 (average primary particle size) of 0.35 μm, a d10 of 0.10 μm, and a d90 of 1.68 μm on a cumulative frequency distribution curve. Particles were prepared by the following method. First, alumina particles were obtained. These particles were divided into three equal groups. Particles from a first group were crushed for 1 hour at 140 rpm, using zirconia spheres with a diameter of 10 mmΦ. Particles from a second group were pulverized at 180 rpm for 3 hours using zirconia spheres with a diameter of 1 mmΦ. Particles from a third group were dispersed in isopropyl alcohol and crushed in a wet bead mill, using zirconia beads with a diameter of 0.3 mmΦ at a peripheral speed of 10 m/s. The crushed particles from these groups were mixed to form the second inorganic solid particles. The average particle size, BET specific surface area and second Li ion conductivity at 25°C of the second inorganic solid particles are listed in Table 1.

[0284] Then, the first and second inorganic solid particles obtained were mixed in a ratio of 50:50 by weight, in order to obtain a mixture of inorganic solid particles. The d90/d10 ratio of the mixture of inorganic solid particles obtained, the mixing ratio of the inorganic solid particles, the conductivity ratio of Li OH/OL, the average particle size ratio RH/RL and the specific surface area ratio BET SH /SL are listed in Table 1.

(Preparation of non-aqueous electrolyte precursor coating material)

[0285] Propylene carbonate (PC) and diethyl carbonate (DEC) were mixed at a ratio of 1: 2, by volume, in order to prepare a solvent. Lithium hexafluorophosphate, LiPF6, was dissolved in the solvent to obtain a concentration of 1.2 mol/l. Thus, a non-aqueous liquid electrolyte was obtained.

[0286] Next, an acrylonitrile monomer was used as a gelatinizing agent. This monomer was added to the non-aqueous liquid electrolyte to obtain a concentration of 2% by weight. Thus, the coating material of a non-aqueous electrolyte precursor was obtained.

(Electrode array production)

[0287] PVdF and the mixture of previously prepared inorganic solid particles were added to N-methylpyrrolidone (NMP) to obtain a suspension. PVdF was added at a proportion of 5% by weight of the inorganic solid particle mixture.

[0288] The suspension thus obtained was applied to a surface of the layer containing positive electrode active material. Then, NMP was evaporated from the coated film. In this way, the mixture of inorganic solid particles was provided on the surface of the layer containing positive electrode active material.

[0289] Then, the previously prepared non-aqueous electrolyte precursor coating material was applied to the surface on which the inorganic solid particles of the positive electrode active material-containing layer were provided to form a coated film. The applied film was then heated at 60°C for 6 hours. In this way, the monomers were polymerized in polyacrylonitrile (PAN). Thus, the Li conductive layer containing the mixture of inorganic solid particles and the non-aqueous electrolyte comprising polymer gel (PAN) was formed on the surface of the positive electrode active material. The non-aqueous electrolyte included in its components a non-aqueous electrolyte solution containing Li and a monomeric component constituting the polymer gel together with this component.

[0290] In the same procedure, the similar Li conductive layer was formed on a surface of the layer containing negative electrode active material.

[0291] Then, the Li conductive layer formed on the positive electrode active material-containing layer was pressed against the Li conductive layer formed on the negative electrode active material-containing layer.

[0292] In example 1, the applied amount of suspension containing the mixture of inorganic solid particles and non-aqueous electrolyte precursor coating material and the compression pressure were determined so that the average thickness of the Li conductive layer was 5 μm and the minimum layer thickness was 0.5 μm.

[0293] In this way, an electrode assembly was obtained comprising a layer containing positive electrode active material, the layer containing negative electrode active material and the Li conductive layer.

[0294] The composite electrolyte comprised in the electrode assembly of example 1 comprises the mixture of inorganic solid particles, the non-aqueous electrolyte solution (component) and the monomeric polyacrylonitrile component in a weight ratio of 99.9: 0.08 : 0.02, respectively. Therefore, the fraction of non-aqueous electrolyte (electrolyte containing organic polymer) in the composite electrolyte was 0.10% by weight.

(Examples 2 to 7)

[0295] In examples 2 to 7, the electrode assemblies of examples 2 to 7 were produced in the same way as in example 1, with the only difference being the amount of non-aqueous electrolyte in the composite electrolyte. Specifically, the amount of non-aqueous electrolyte was modified to 2.0% by weight (example 2), 4.0% by weight (example 3), 10.0% by weight (example 4), 16.0% by weight (example 5), 20.0% by weight (example 6) and 25.0% by weight (example 7).

(Examples 8 to 13)

[0296] In examples 8 to 13, the electrode assemblies of examples 8 to 13 were produced in the same way as that produced in example 3, except for the following details.

[0297] In examples 8 to 13, particles of a compound with a garnet-type crystal structure and with a chemical formula of Li7La3Zr2O12 (LLZ) were provided as first inorganic solid particles. The average particle size, specific surface area and first ionic conductivity at 25°C of the first inorganic solid particles are listed in Table 1.

[0298] On the other hand, alumina particles with a formula Al2O3 were provided as second inorganic solid particles. The average particle size, specific surface area and the first ionic conductivity at 25°C of the second inorganic solid particles are listed in Table 1.

[0299] In examples 8 to 13, the first inorganic solid particles (LLZ) and the second inorganic solid particles were mixtures at a ratio of 1 : 99 (example 8), 10 : 90 (example 9), 25 : 75 (example 10), 75 : 25 (example 11), 90 : 10 (example 12) and 99 : 1 (example 13).

(Examples 14 to 20)

[0300] In examples 14 to 20, the electrode assemblies of examples 14 to 20 were produced in the same way as example 3, but the first and second inorganic solid particles were modified.

[0301] Specifically, in example 14, the first inorganic solid particles are the same as in example 3. In example 14, particles of a compound with the composition Li1.5Ti1.7Al0.3P2.8Si0.2O12 (LATP) were used as second inorganic solid particles.

[0302] In example 15, the same first inorganic solid particles were used as in example 8. In example 15, particles of a lithium phosphorus oxynitride (LIPON) glass electrolyte were used.

[0303] In example 16, particles of a compound with a crystalline structure of the Perovskite type were used as the first solid particles, whose composition is represented by the formula Li0.56Li0.33TiO3 (LLT). In example 16, the same second inorganic solid particles were used as in example 15.

[0304] In example 17, the same inorganic solid particles were used as those in example 8. In example 17, zirconium oxide (zirconia) particles were used as second inorganic solid particles.

[0305] In example 18, the same first inorganic solid particles were used as those used in example 8. In example 18, magnesium oxide (magnesia) particles were used as second inorganic solid particles.

[0306] In example 19, the same first inorganic solid particles were used as those used in example 8. In example 19, particles of titanium oxide (titania) with a rutile-type crystalline structure were used as second inorganic solid particles.

[0307] In example 20, the same first inorganic solid particles were used as those used in example 8. In example 20, silicon oxide (silica) particles were used as second inorganic solid particles.

[0308] The average particle size, the BET specific surface area and the ionic conductivities at 25°C of the first and second inorganic solid particles used in each example are listed in Table 1.

(Examples 21 to 27)

[0309] In examples 21 to 27, the electrode assemblies of examples 21 to 27 were produced with the same procedure as that of example 3, except for the following details.

[0310] In examples 21 to 27, the same first inorganic solid particles and the same second inorganic solid particles were used as those used in example 8. The mixing ratio, by weight, was 50:50 in preparing the particle mixture solid.

[0311] In examples 21 to 27, the thickness of the Li conductive layer was modified in relation to that used in example 1. Specifically, 20.0 μm (example 21), 15.3 μm (example 22), 10 .3 μm (example 23), 7.9 μm (example 24), 3.1 μm (example 25), 1.1 μm (example 26), and 0.5 μm (example 27).

(Examples 28 to 31)

[0312] In examples 28 to 31, electrode assemblies of examples 28 to 31 were produced in the same way as that produced for example 3, but the particle size distributions of the first and second inorganic solid particles are different from those of example 1 .

[0313] Specifically, the particle size distribution of the first and second different inorganic solid particles were obtained by the following procedure.

[0314] In example 28, only ball mills with 10 mmΦ diameter zirconia spheres were used to grind the first inorganic solid particles and, as for the grinding conditions of the second inorganic solid particles, a bead mill was used wet, with a peripheral speed of 15 m/s, for 8 hours.

[0315] In example 29, a wet bead mill was not used to grind the first inorganic solid particles and, for the second inorganic solid particles, grinding was used with a peripheral speed of 10m/s, for 8 hours.

[0316] In example 30, under the conditions of grinding the first inorganic solid particles, through a wet bead mill, a peripheral speed of 10 m/s for 8h was used and, for the second inorganic solid particles, only grinding by ball mill, with zirconia spheres of 10 mmΦ in diameter, for 2 hours.

[0317] In example 31, under the conditions of wet bead mill grinding of the first inorganic solid particles, a peripheral speed of 10 m/s was used for 8 hours and, for the second inorganic solid particles, a bead mill wet was not carried out for grinding.

[0318] The average particle sizes, BET specific surface areas and ionic conductivities at 25°C of the first and second inorganic solid particles for each example are listed in Tables 1 and 2.

(Examples 32 to 34)

[0319] In examples 32 to 34, electrode assemblies of examples 32 to 34 were produced in the same way as the assembly of example 3, except for the following details.

[0320] In examples 32 to 34, the same first and second inorganic solid particles were used as those used in example 8. The mixing ratio, by weight, was 50:50 for preparing the solid particle mixture.

[0321] Furthermore, in examples 32 to 34, the composition of a solvent mixture of a non-aqueous liquid electrolyte comprised in a coating material of a non-aqueous electrolyte precursor is different from that in example 1, as described in follow. Example 32: the solvent is a mixture of propylene carbonate (PC) and dimethyl carbonate (DMC), in a volumetric ratio of 1:2, respectively. Example 33: the solvent is a mixture of ethylene carbonate (EC) and diethyl carbonate (DEC), in a volumetric ratio of 1:2, respectively; and example 34: the solvent is a mixture of propylene carbonate (PC) and methyl ethyl carbonate (MEC), in a volumetric ratio of 1:2, respectively.

(Examples 35 to 41)

[0322] In examples 35 to 41, the electrode assemblies of examples 35 to 41 were produced in the same way as that of example 3, except for the following details.

[0323] In examples 35 to 41, the same first and second inorganic solid particles were used as those in example 8. The ratio between them, by weight, was 50:50 in preparing the mixture of inorganic solid particles.

[0324] Furthermore, in examples 35 to 41, the weight ratio between the mixture of inorganic solid particles, the non-aqueous electrolyte solution fraction and polyacrylonitrile monomer fraction in a composite electrolyte was as follows, for each example: Example 35: [96 : 3.5 : 0.5]; Example 36: [96 : 3.0 : 1.0], Example 37: [96 : 2.5 : 1.5]; Example 38 [96 : 2.0: 2.0]; Example 39 [96 : 1.5 : 2.5]; Example 40: [96 : 1.0 : 3.0] and Example 41: [96 : 0.5 : 3.5]

(Example 42)

[0325] In example 42, an electrode array comprising an electrode with a bipolar structure was produced in the following manner.

[0326] A positive electrode suspension and a negative electrode suspension were prepared according to the procedure presented in example 1. Then, a positive electrode suspension was applied to a surface of an aluminum alloy sheet (purity 99. 3%), with a thickness of 15 μm so as to form a coated film, and then the coated film was dried. A negative electrode suspension was applied to the other surface of the aluminum alloy sheet to form a coated film, and then the coated film was dried. The composite obtained was compressed. The amount of suspension applied and the compression pressure were determined so that the thickness of a layer containing positive electrode active material formed on a surface of a current collector was 67 μm; the density of the layer containing positive electrode active material was 2.2 g/cm3; the thickness of the layer containing negative electrode active material formed in a current collector was 59 μm and the density of the layer containing negative electrode active material was 2.2 g/cm3. Thus, a first electrode was obtained having a bipolar structure and comprising the current collector, the positive electrode active material-containing layer formed on one surface of the current collector and the negative electrode active material-containing layer formed on the other surface of the collector. chain.

[0327] The second to fourth electrodes were prepared, each with the same structure as the first electrode. Furthermore, a fifth electrode with the same structure as the first electrode was prepared, but the fifth electrode did not include the active material layer of the positive electrode, and a sixth electrode with the same structure as the first electrode was prepared, but the sixth electrode did not include included negative electrode active material.

[0328] Then, a Li conductive layer was formed between the positive electrode active material-containing layer of the first electrode and the negative electrode active material-containing layer of the second electrode. A Li conductive layer was formed between the positive electrode active material-containing layer of the second electrode and the negative electrode active material-containing layer of the third electrode. A Li conductive layer was formed between the positive electrode active material-containing layer of the third electrode and the negative electrode active material-containing layer of the fourth electrode. A Li conductive layer was formed between the negative electrode active material-containing layer of the first electrode and the positive electrode active material-containing layer of the sixth electrode. A Li conductive layer was formed between the fourth electrode active material-containing layer of the first electrode and the negative electrode active material-containing layer of the fifth electrode.

[0329] The Li conductive layer was produced by the same procedure as in example 3, except for the following details.

[0330] First, a mixture was obtained by mixing the same first and second inorganic solid particles as those used in example 8, in a 50:50 ratio by weight. LiPF6 was dissolved in a solvent mixture to a concentration of 1 mol/l at the time of preparing a non-aqueous liquid electrolyte.

(Comparative example 1)

[0331] In Comparative Example 1, an electrode array of Comparative Example 1 was produced in the same way as that of Example 1, except for the following details.

[0332] In comparative Example 1, a conductive Li layer comprising a composite electrolyte was not formed. Instead, a polypropylene (PP) separator with a thickness of 20 μm was introduced between the layer containing positive electrode active material and the layer containing negative electrode active material. This separator was impregnated with the same non-aqueous electrolyte precursor coating material as that prepared in Example 1 and this coating material was heated at 60 ° C for 6 hours. In this way, a non-aqueous electrolyte containing PAN was retained within the active material-containing layer of the positive electrode, the active material-containing layer of the negative electrode, and the separator.

(Comparative example 2)

[0333] In Comparative Example 2, a set of electrodes from Comparative Example 2 was produced in the same way as that from Example 1, except that a polyethylene separator with a thickness of 20 μm was used.

(Comparative example 3)

[0334] In Comparative Example 3, a set of electrodes from Comparative Example 3 was produced in the same way as in Example 1, except for the following details.

[0335] In comparative Example 3, a Li conductive layer comprising a composite electrolyte was not formed. Instead, a body of synthesized Li7La3Zr2O12 particles, with a thickness of 20 μm, was introduced between the layer containing positive electrode active material and the layer containing negative electrode active material. The Li7La3Zr2O12 particles had an average primary particle size of 1 μm.

(Comparative example 4)

[0336] In Comparative Example 4, a set of electrodes from Comparative Example 4 was produced in the same way as in Example 1, except for the following details.

[0337] In comparative Example 4, a Li conductive layer comprising a composite electrolyte was not formed. Instead, a polyacrylonitrile polymer gel sheet, with a thickness of 40 μm, was introduced between the layer containing positive electrode active material and the layer containing negative electrode active material. A non-aqueous electrolyte was retained in the polymeric sheet so that the polyacrylonitrile gel fraction was 2% by weight. The non-aqueous liquid electrolyte was prepared by mixing propylene carbonate and diethyl carbonate at a volumetric ratio of 1:2, respectively, forming a solvent mixture and dissolving LiPF6 to a concentration of 1.2 mol/l in this solvent mixture. .

(Comparative example 5)

[0338] In Comparative Example 5, a set of electrodes from Comparative Example 5 was produced in the same way as in Example 8, but LLZ particles were not used.

(Comparative example 6)

[0339] In Comparative Example 6, a set of electrodes from Comparative Example 6 was produced in the same way as in Example 6, but alumina particles were not used.

(Comparative examples 7 to 9)

[0340] In comparative Examples 7 to 9, sets of electrodes from comparative Examples 7 to 9 were produced in the same way as in Example 1, but the d90/d10 ratio of a mixture of inorganic solid particles differed from that of Example 1.

[0341] Specifically, the d90/d10 ratio was modified by the following procedure.

[0342] In comparative Example 7, in the particle size distribution of the first and second inorganic solid particles, the grinding conditions were established so that the d90/d10 ratio was close to 8.

[0343] In comparative Example 8, measurement of the d90/d10 ratio of the particle size distribution and grinding were carried out alternatively and in a short period of time, so that the particle size distributions of the first and second inorganic solid particles were as equivalent as possible.

[0344] In comparative Example 9, the second inorganic solid particles were ground with just one cycle of the roller compactor (steam roller).

(Comparative examples 10 and 11)

[0345] In Comparative Examples 10 and 11, the electrode assemblies of Comparative Examples 10 and 11 were produced in the same way as in Example 3, except for the following details.

[0346] In comparative Examples 10 and 11, the same first and second inorganic solid particles were used as in Example 8. These particles were mixed in a ratio of 50:50 by weight to form a mixture of inorganic solid particles .

[0347] In comparative Examples 10 and 11, the weight ratio between mixture of inorganic solid particles, non-aqueous electrolyte solution and acrylonitrile monomer was, respectively, for each example: Comparative example 10: [99.95: 0.04: 0.01] and Comparative Example 11: [70 : 20 : 10].

[0348] The parameters of the materials contained in the electrode sets of the Examples and comparative Examples are listed in Tables 1 to 6. Each parameter was measured by the procedure described previously. Table 1: Table 2: Table 3: Table 4: Table 5: (1)Mixture of inorganic solid particles/ Non-aqueous electrolyte solution component/ Monomeric component (2)Relative value. “1” is defined as the value of comparative Example 1 Table 6: (1)Mixture of inorganic solid particles/ Non-aqueous electrolyte solution component/ Monomeric component (2)Relative value. “1” is defined as the value of Comparative Example 1

[Secondary battery production]

[0349] Each of the electrode assemblies of the Examples and comparative Examples was packaged in a laminated film container and the outer circumference of the container was heat sealed. Thus, secondary batteries of Examples and Comparative Examples were produced.

<Evaluation>

[0350] The secondary batteries of the Examples and Comparative Examples were evaluated in the following manner.

[0351] First, a secondary battery was placed in a thermostatic chamber with a temperature of 25°C for 1 hour. Then the secondary battery was charged to 2.8V with a constant current at a discharge rate of 0.2C. Next, the secondary battery was charged to a constant voltage of 2.8V and a current value was converged to 1/20C. Afterwards, the secondary battery was discharged at a constant current of 1C with a cut-off voltage of 1.5V. A discharge capacity obtained by this discharge was defined with a discharge capacity of 1C. Then, after being charged under the same conditions, the secondary battery was discharged at a constant current of 20C with a cut-off voltage of 1.5V. A discharge capacity obtained by this discharge was defined as a discharge capacity 20C. A retention capacity rate ratio (%) was calculated by multiplying the value obtained by dividing the 20C discharge capacity by the 1C discharge capacity by 100.

[0352] Next, the secondary battery was charged at 25°C in the same manner as described above. Subsequently, the temperature of the thermostatic chamber comprising the secondary battery was set at -30°C for 2 hours. Next, the secondary battery was discharged at -30°C at a constant current of 1C, with a cut-off voltage of 1.5V. A discharge capacity obtained by this discharge was defined as a discharge capacity at -30°C. Low temperature performance (output performance ratio) was calculated by multiplying the value obtained by dividing the discharge capacity at -30°C by the discharge capacity value 1C (i.e. the discharge capacity at 25°C). , obtained previously, by 100.

[0353] Then, the temperature of the thermostatic chamber was set at 60°C for 2 hours. Subsequently, the secondary battery was charged to 2.8V with a constant current of 1C. Then, the secondary battery was charged at a constant voltage of 2.8V for 3 hours. After waiting for 10 minutes, the secondary battery was discharged at a constant current of 1C, with a cut-off voltage of 1.5V. This charge-wait-discharge was defined as a charge-and-discharge cycle. By repeating this charge-and-discharge cycle, the life cycle performance at 60°C was evaluated. The value obtained by dividing the discharge capacity at 60°C after 500 cycles by the capacity initially discharged at 60°C was multiplied by 100 to obtain the cycle retention capacity ratio (%) at 60°C.

[0354] The results of the evaluations carried out through the tests described above are listed in Tables 7 and 8. Table 7: Table 8:

[0355] As is clear from the results presented in Tables 7 and 8, it was determined that the secondary batteries of Examples can have excellent low-temperature life and output performances than the secondary batteries of comparative Examples 1 to 11.

[0356] The secondary battery of Example 12 included a Li conductive layer with the same thickness as that of the separators, sintered bodies and sheet electrolytic layers of Comparative Examples 1 to 3 and showed superior performance to Comparative Examples 1 to 3 in all the questions.

[0357] A high overvoltage has been applied to the secondary battery of Comparative Example 8 and the battery cannot be charged. In the secondary battery of Comparative Example 10, the composite solid electrolyte layer has detached from the electrode and the secondary battery cannot be charged due to a short circuit during assembly.

(Example 43)

[0358] In Example 43, an electrode assembly of Example 43 was produced in the same manner as in Example 3, except for the following details.

[0359] In Example 43, particles of a compound with a rhombohedral crystal structure of the NACICON type and with chemical formula Li1.2Zr1.9Ca0.1(PO4)3(LZCP) were used as the first inorganic solid particles. The average particle size, BET specific surface area and Li ion conductivity at 25C of the first inorganic solid particles are listed in Table 9.

[0360] On the other hand, alumina particles with a chemical formula Al2O3 were used as second inorganic solid particles. The average particle size, BET specific surface area and Li ion conductivity at 25°C are listed in Table 9.

[0361] In Example 43, the first inorganic solid particles (LZCP) and the second inorganic solid particles were mixed in a ratio of 50:50.

(Example 44)

[0362] In Example 44, an electrode array of Example 44 was produced in the same manner as in Example 3, except for the following details.

[0363] In Example 44, particles of a compound with a distorted triclinic crystal structure and a chemical formula LiZr2(PO4)3 (LZP) were used as the first inorganic solid particles. The average particle size, BET specific surface area and first Li ion conductivity at 25°C of the first inorganic solid particles are listed in Table 9.

[0364] On the other hand, alumina particles with chemical formula Al2O3 were used as second inorganic solid particles. The average particle size, BET specific surface area and first Li ion conductivity at 25°C of the second inorganic solid particles are listed in Table 9

[0365] In Example 44, the first inorganic solid particles (LZP) and the second inorganic solid particles were mixed in a ratio of 50:50. Table 9:

[0366] The parameters of the materials contained in the electrode sets of Examples 43 and 44 are listed in Tables 10 and 11. Each parameter was measured using the procedure described previously. Table 10: Table 11: (1) Mixture of inorganic solid particles/ Non-aqueous electrolyte solution component/ Monomeric component (2) Relative value. “1” is defined as the value of Comparative Example 1

[Secondary battery production]

[0367] Each of the electrode assemblies of Examples 43 and 44 was packaged in a laminated film container and the outer circumference was heat sealed. Thus, the secondary batteries of Examples 43 and 44 were produced.

<Evaluation>

[0368] The secondary batteries of Examples 43 and 44 were evaluated according to the procedure described above.

[0369] The results of the evaluative tests are shown in Table 12. Table 12:

[0370] As is clear from the results presented in Tables 7,8 and 12, each secondary battery of Examples 43 and 44 may have better life and output performances at low temperatures than the performances of the secondary batteries of comparative Examples 1 to 11, as well as when compared to each secondary battery of Examples 1 to 42. Furthermore, as is clear, for example, in Examples 3, 16, 43 and 44, although the secondary batteries of these examples include first inorganic solid particles different from each other, each one of these secondary batteries exhibited excellent and equivalent life and output performances.

[0371] According to at least one embodiment and examples described above, a composite electrolyte is provided. The composite electrolyte comprises a mixture of inorganic solid particles and a non-aqueous electrolyte comprising Li. The mixture of inorganic solid particles comprises first inorganic solid particles, which have a first Li ion conductivity at 25°C, and second inorganic solid particles, which have a second conductivity Li ions at 25°C. The second Li ion conductivity at 25°C is lower than the first Li ion conductivity at 25°C of the first inorganic solid particles. The weight ratio of the non-aqueous electrolyte and the composite electrolyte varies between 0.1% and 25%. The mixture of inorganic solid particles satisfies 10 < d90/d10 < 500. In this composite electrolyte, the dissociation of Li ions from the non-aqueous electrolyte and the conduction of Li ions can be carried out homogeneously. As a result, the composite electrolyte can provide a secondary battery capable of excellent life and output performances at low temperatures.

[0372] Even though certain embodiments have been described, these embodiments have been presented by way of example only and there is no intention to limit the scope of the invention. In fact, the concretizations presented here can take other forms; Furthermore, the embodiments presented here may be omitted, replaced or changed, without thereby departing from the spirit of the inventions. The claims herein or equivalent are intended to cover such modifications that are within the scope and spirit of the inventions.

Claims (15)

1. Composite electrolyte (9) characterized by comprising: a mixture of inorganic solid particles (91) comprising first inorganic solid particles (91A) with a first lithium ion conductivity at 25 ° C and second inorganic solid particles (92B) with a second Li ion conductivity at 25°C and the second Li ion conductivity at 25°C being lower than the first Li ion conductivity at 25°C; and a non-aqueous electrolyte (92) comprising Li, wherein: a ratio of a weight of the non-aqueous electrolyte (92) to a weight of the composite electrolyte (9) is 0.1% to 25%; the mixture of inorganic solid particles (91) satisfies 10 ≤ d90/d10 ≤ 500; where: d10 is a particle size [μm] where a cumulative frequency from a small particle size side is 10% on a cumulative particle size curve of the mixture of inorganic solid particles (91), the cumulative particle size curve obtained by a laser diffraction dispersion method; and d90 is a particle size [μm] in which a cumulative frequency on the small particle size side is 90% on the cumulative particle size curve. 2. Composite electrolyte (9), according to claim 1, characterized by the fact that the first Li ion conductivity at 25 ° C is 1x1Q-i° S/cm or more, and the second ion conductivity of Li at 25°C is less than 1x1Q-i° S/cm; and a ratio of a weight of the first inorganic solid particles (91A) to a weight of the second inorganic solid particles (91B) is 1% or more and less than 99%. 3. Composite electrolyte (9), according to claim 1 or 2, characterized by the fact that the mixture of inorganic solid particles (91) satisfies 10 < oH/oL; where oH is the first conductivity of Li ions at 25°C; and oL is the second conductivity of Li ions at 25°C. 4. Composite electrolyte (9), according to any one of claims 1 to 3, characterized by the fact that: an average particle size of the first inorganic solid particles (91A) is equal to an average particle size of the second solid particles inorganic particles (91B), or the mixture of inorganic solid particles (91) satisfies 1 < RH/RL ^ 100; where RH is an average particle size [μm] of particles having a larger average particle size between the average particle sizes of the first inorganic solid particles (91A) and the second inorganic solid particles (91B); and RL is an average particle size [μm] of particles having a smaller average particle size between the average particle sizes of the first inorganic solid particles (91A) and the second inorganic solid particles (91B). 5. Composite electrolyte (9), according to any one of claims 1 to 3, characterized by the fact that: a specific surface area BET [m2/g] of the first inorganic solid particles (91A) is equal to a specific surface area BET [m2/g] of the second inorganic solid particles (91B), or the mixture of inorganic solid particles (91) satisfies 1 < SH/SL ^ 50; wherein SH is a BET specific surface area [m2/g] of particles having a BET specific surface area greater than the BET specific surface areas of the first inorganic solid particles (91A) and the second inorganic solid particles (91B); and SL is a BET specific surface area [m2/g] of particles having a smaller BET specific surface area between the BET specific surface areas of the first inorganic solid particles (91A) and the second inorganic solid particles (91B). 6. Composite electrolyte (9), according to any one of claims 1 to 5, characterized by the fact that it satisfies an inequality of wi > ^; where wi is a peak frequency in a complex modulus spectrum of the composite electrolyte (9); and W2 is a peak frequency in a complex modulus spectrum of the nonaqueous electrolyte (92). 7. Composite electrolyte (9), according to any one of claims i to 6, characterized by the fact that it satisfies an inequality of C2 > C1 > C3; where C1 is a concentration of Li ions [mol/L] at an interface (9A) between the first inorganic solid particles (91A) and the non-aqueous electrolyte (92); C2 is a concentration of Li ions [mol/L] at an interface (9B) between the second inorganic solid particles (91B) and the non-aqueous electrolyte (92); and C3 is a Li ion concentration [mol/L] in the non-aqueous electrolyte (92). 8. Composite electrolyte (9), according to any one of claims 1 to 7, characterized in that the non-aqueous electrolyte (92) comprises a solid polymeric electrolyte and/or a gel polymeric electrolyte. 9. Secondary battery (100) characterized by comprising: a layer containing active material of the positive electrode (5b); a layer containing active material of the negative electrode (3b); and a Li conductive layer (4) provided between the active material-containing layer of the positive electrode (5b) and the active material-containing layer of the negative electrode (3b) and comprising the composite electrolyte (9) as defined in any one of claims 1 to 8. 10. Secondary battery (100), according to claim 9, characterized by the fact that a minimum thickness of the Li conductive layer (4) is less than 8 μm. 11. Secondary battery (100), according to claim 9 or 10, characterized in that the negative electrode active material-containing layer (3b) comprises a negative electrode active material containing Ti. 12. Secondary battery (100), according to any one of claims 9 to 11, characterized by the fact that it comprises a first electrode composite (10A, 10B, 10C) and a second electrode composite (10A, 10B, 10C) provided adjacent to the first electrode composite (10A, 10B, 10C), each of the electrode composites (10A, 10B, 10C) comprising: a current collector (8) comprising a first surface and an opposing second surface, the layer containing positive electrode active material (5b) provided on the first surface of the current collector (8), and the layer containing negative electrode active material (3b) provided on the second surface of the current collector (8); and the Li conductive layer (4) is provided between the active material-containing layer of the positive electrode (5b) of the first electrode composite (10A, 10B, 10C) and the active material-containing layer of the negative electrode (3b) of the second composite electrode (10A, 10B, 10C). 13. Battery pack (300) characterized by comprising the secondary battery as defined in any one of claims 9 to 12. 14. Battery pack (300), according to claim 13, characterized by further comprising: an external power distribution terminal (347); and a protection circuit (344). 15. Battery pack (300), according to claim 13 or 14, characterized by comprising a plurality of secondary batteries (100), the plurality of secondary batteries (100) being electrically connected in series, in parallel or in combination of in series and in parallel.