JP7286559B2 - Electrode group, non-aqueous electrolyte secondary battery, battery pack and vehicle - Google Patents

Description

TECHNICAL FIELD Embodiments of the present invention relate to electrode groups, nonaqueous electrolyte secondary batteries, battery packs, and vehicles.

In recent years, research and development of non-aqueous electrolyte secondary batteries, such as lithium ion secondary batteries, have been actively promoted as high energy density batteries. Non-aqueous electrolyte secondary batteries are expected as power sources for hybrid vehicles, electric vehicles, and uninterruptible power sources for mobile phone base stations. In particular, a battery using lithium nickel manganese oxide (LNMO), which has a discharge potential of 4.7 V based on Li/Li ⁺ and a high discharge potential, as a positive electrode active material for a positive electrode has a high energy density. It is attracting attention because it is possible.

However, since LNMO has a very noble discharge potential, decomposition of the organic solvent contained in the non-aqueous electrolyte occurs at the positive electrode, gas is generated, and the battery tends to swell.

In Patent Document 1, the entire active material is covered with lithium conductive glass to suppress contact with an organic solvent, thereby suppressing gas generation. However, since the lithium conductive glass has lower lithium ion conductivity than the organic solvent, the coating of the active material with the lithium conductive glass raises the problem that the resistance increases and the rate characteristics deteriorate.

JP-A-2003-173770

Provided is an electrode group that suppresses gas generation and realizes a non-aqueous electrolyte secondary battery with good rate characteristics and high battery voltage.

The electrode group according to the present embodiment includes lithium composite oxide LiM _x Mn _2-x O ₄ (0<X≦0.5, M is selected from Ni, Cr, Fe, Cu, Co, Mg and Mo) as a positive electrode active material. a positive electrode containing at least one selected from the group consisting of: a negative electrode containing a negative electrode active material; and a composite electrolyte layer containing at least one of a solid electrolyte and an inorganic compound having alumina between the negative electrode and the positive electrode, and a separator. , the density of the composite electrolyte layer is 1.0 g/cc or more and 2.2 g/cc or less.

FIG. 2 is a conceptual cross-sectional view of an electrode group according to the first embodiment; The cross-sectional schematic diagram which shows an example of the non-aqueous electrolyte secondary battery of 2nd Embodiment. The enlarged cross-sectional schematic diagram of the A part of FIG. FIG. 4 is a partially cutaway perspective view showing another example of the non-aqueous electrolyte secondary battery according to the second embodiment; The enlarged cross-sectional schematic diagram of the B section of FIG. The schematic perspective view which shows an example of the assembled battery which concerns on 3rd Embodiment. FIG. 11 is an exploded perspective view showing an example battery pack according to a third embodiment; FIG. 8 is a block diagram showing an electric circuit of the battery pack of FIG. 7; Sectional drawing which shows roughly the vehicle of an example which concerns on 4th Embodiment. Sectional drawing which shows roughly the vehicle of an example which concerns on 4th Embodiment.

Hereinafter, embodiments will be described with reference to the drawings. In addition, the same code|symbol shall be attached|subjected to the common structure through embodiment, and the overlapping description is abbreviate|omitted. In addition, each drawing is a schematic diagram for explaining the embodiments and promoting understanding thereof, and there are places where the shapes, dimensions, ratios, etc. are different from the actual device, but these are the following explanations and known techniques. Consideration can be taken into consideration and the design can be changed as appropriate.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(First embodiment)
FIG. 1 is a conceptual cross-sectional view of an electrode group according to the first embodiment. The electrode assembly according to the first embodiment shown in FIG. 1a comprises a positive electrode 5, a composite electrolyte layer 8, a separator 4 and a negative electrode 3. The electrode assembly according to the first embodiment shown in FIG. 1b comprises a positive electrode 5, a separator 4, a composite electrolyte layer 8 and a negative electrode 3. The electrode group according to the first embodiment shown in FIG. The composite electrolyte layer, the separator, the positive electrode, and the negative electrode that constitute the electrode group will be specifically described. When the positive electrode and the negative electrode are collectively described, they may also be described as electrodes.

(composite electrolyte layer)
The composite electrolyte layer is formed between the positive electrode and the negative electrode, and has a density of 1.0 g/cc or more and 2.2 g/cc or less. The composite electrolyte layer contains a solid electrolyte, which will be described later, and the solid electrolyte preferably has a lithium ion conductivity of 1×10 ⁻¹⁰ S/cm or more at 25° C. The composite electrolyte layer can be mixed with a binder and formed on the negative electrode or the positive electrode. Therefore, they can be arranged as shown in FIGS. 1a and 1b, in which the composite electrolyte layer, the later-described separator, and the electrodes can be arranged in this order. Alternatively, composite electrolyte layers may be disposed on both major surfaces of the separator, as shown in FIG. 1c. That is, the composite electrolyte layer can be formed so as to face both the positive electrode and the negative electrode. When forming the composite electrolyte layer, it may be formed by coating directly on the electrode, or may be formed by coating on the separator. The order may be the separator, the composite electrolyte layer, and the electrode, or the electrodes may be faced via the separator, that is, the order may be the composite electrolyte, the separator, and the electrode. The composite electrolyte layer may contain inorganic particles, a plasticizer, a dispersing agent, etc. in addition to the solid electrolyte particles. The electrode and the composite electrolyte and the separator and the composite electrolyte do not necessarily have to be in contact with each other.

When the density of the composite electrolyte layer is 1.0 g/cc or more and 2.2 g/cc or less, the movement of decomposition products of the organic solvent contained in the non-aqueous electrolyte can be suppressed, and the composite electrolyte layer can moderately absorb the non-aqueous electrolyte. can hold. Decomposition products of organic solvents include, for example, water and alcohol. The migration of the decomposition products of the organic solvent means that the generated decomposition products of the organic solvent move between the positive and negative electrodes via the separator. By moving the decomposition products of the organic solvent, for example, the decomposition products generated at the positive electrode move and are reduced on the negative electrode to become hydrogen or the like, promoting gas generation. Therefore, since the movement of decomposition products of the organic solvent can be suppressed, the generation of gas in the secondary battery can be suppressed, and the life performance can be improved. In addition, lithium ions can move because the non-aqueous electrolyte can be appropriately retained.

If the density of the composite electrolyte layer is less than 1.0 g/cc, the migration of decomposition products of the organic solvent cannot be suppressed. If the holding power of the non-aqueous electrolyte in the composite electrolyte layer is lowered, the ionic conductivity is lowered, which is not preferable. The density of the composite electrolyte layer is more preferably 1.3 g/cc or more and 1.5 g/cc or less. Within this range, the migration of decomposition products of the organic solvent can be suppressed, and the retention of the non-aqueous electrolyte in the composite electrolyte layer can be maintained.

The density of the composite electrolyte layer is preferably substantially uniform within the composite electrolyte layer. That is, the density distribution in the composite electrolyte layer falls within the range of 1.0 g/cc or more and 2.2 g/cc or less, and the density distribution in the composite electrolyte layer has a density portion outside the range defined in the present invention. Absence is preferred. If there is a portion where the density in the composite electrolyte layer is not equal to or greater than 1.0 g/cc and equal to or less than 2.2 g/cc, the retention of the non-aqueous electrolyte in the composite electrolyte layer is reduced as described above, and the organic solvent is decomposed. This is because there is a portion where the movement of matter cannot be suppressed, so that gas generation cannot be suppressed and ionic conductivity cannot be maintained.

The thickness of the composite electrolyte layer is desirably 0.1 μm or more and 100 μm or less. If the thickness of the composite electrolyte layer is too thin, the solid electrolyte layer is too thin to suppress the movement of decomposition products of the organic solvent. decreases. More preferably, it is 1 μm or more and 20 μm or less. This is because, within this range, it is possible to simultaneously suppress the movement of decomposition products of the organic solvent and the resistance of the composite electrolyte layer.

Since the composite electrolyte layer contains a solid electrolyte, it can permeate only lithium ions. Therefore, by forming the composite electrolyte layer on the positive electrode, the negative electrode, and the separator, it is possible to block the movement of decomposition products of the organic solvent without blocking the movement of cations without covering the active material.

The lithium ion conductivity at 25° C. of the separator solid electrolyte provided in the electrode group according to the first embodiment is preferably 1×10 ⁻¹⁰ S/cm or more. When the solid electrolyte has a lithium ion conductivity of 1×10 ⁻¹⁰ S/cm or more at 25° C., the lithium ion concentration in the vicinity of the particle surface tends to increase, so that rate performance and life characteristics can be improved. More preferably, the solid electrolyte has a lithium ion conductivity at 25° C. of 1×10 ⁻⁶ S/cm or more. When the lithium ion conductivity of the solid electrolyte at 25° C. is 1×10 ⁻⁶ S/cm or more, the lithium ion concentration in the vicinity of the surface of the solid electrolyte tends to be higher, so the rate performance and life characteristics are further improved. . The upper limit of the lithium ion conductivity is according to one example 2×10 ⁻² S/cm.

Solid electrolytes include, for example, sulfide-based Li ₂ SeP ₂ S ₅ -based glass ceramics, lithium-lanthanum-titanium composite oxides (e.g., Li _0.5 La _0.5 TiO ₃ ), which are inorganic compounds having a perovskite structure, Inorganic compounds having a LISICON-type structure (for example, Li _3.6 Si _0.6 P _0.4 O ₄ ), LATP having a NASICON-type skeleton (Li _1+x Al _x Ti _2-x (PO ₄ ) ₃ ) (0. 1≦x≦ _{0.4 ) and Li3.6Si0.6PO4} , amorphous LIPON ( _{Li2.9PO3.3N0.46} ), lithium calcium zirconium _oxide and garnet-type structures It contains at least one selected from the group consisting of inorganic compounds. Only one kind of inorganic compound may be used as the solid electrolyte particles, or two or more kinds thereof may be used. The particles of the solid electrolyte may consist of a mixture of inorganic compounds.

If the particles of the solid electrolyte contain elemental sulfur, the sulfur component will dissolve in the organic electrolyte, which will be described later, which is not preferable. The inorganic compound particles preferably do not contain elemental sulfur.

Preferred inorganic compound particles are oxides such as LATP having a NASICON- _type skeleton, amorphous LIPON, and _garnet -type lithium-lanthanum-zirconium-containing oxides (for example, _Li7La3Zr2O12 : _LLZ ).

Among these, the inorganic compound particles are preferably inorganic compounds having a garnet structure. An inorganic compound having a garnet-type structure is preferable because it has high Li ion conductivity and resistance to reduction, and has a wide electrochemical window.

The solid electrolyte can be in the form of particles. Therefore, the solid electrolyte may be expressed as solid electrolyte particles. The shape of the solid electrolyte is not particularly limited, and may be, for example, spherical, elliptical, flat, fibrous, or the like.

The average particle size of the solid electrolyte particles is preferably in the range of 0.1 μm or more and 10 μm or less. When the average particle diameter of the solid electrolyte particles is less than 0.1 μm, the amount of solvent contained in the solid electrolyte particles becomes too large, which excessively accelerates the decomposition reaction of the non-aqueous electrolyte, resulting in a decrease in rate performance and battery failure. This is not preferable because it degrades the battery performance such as shortening the life.

If the average particle size of the solid electrolyte particles is larger than 10 μm, the voids between these particles increase, and the ionic conductivity of the solid electrolyte particles decreases, which is not preferable. Further, if the average particle diameter of the solid electrolyte particles is too large, it is difficult to make the composite electrolyte layer sufficiently thin when the solid electrolyte particles are mixed with the electrolyte and the composite electrolyte layer described later is provided between the positive and negative electrodes. Become. As a result, the distance between the positive and negative electrodes increases, and the diffusion resistance of lithium ions increases, which is not preferable.

More preferably, it is in the range of 0.1 μm or more and 5 μm or less. Within this range, the decomposition reaction of the electrolyte is moderately promoted, and the gaps between the solid electrolyte particles are moderate, so that the ionic conductivity of the solid electrolyte particles can be better maintained.

The average particle size of the solid electrolyte particles can be measured as follows. The electrodes removed from the battery are washed with a suitable solvent and dried. As a solvent used for washing, for example, ethyl methyl carbonate may be used. Drying is carried out in air. After that, the electrode is cut out in the direction of the short side of the electrode, and 10 portions are selected at equal intervals from positions 10% or more away from the edge of the cut cross section. The selected 10 locations are observed at a magnification of 10,000 using a scanning electron microscope (SEM). 10 particles are selected for each selected location, and the particle size of each particle is measured. At this time, particles that are easy to observe are selected. The results of such measurements are summarized in spreadsheet software. Exclude extremely large and small particles and calculate the average particle size.

The binder is, for example, a polymer that gels with an organic solvent such as carbonates. Examples of binders include polyacrylonitrile (PAN), polyethylene oxide (PEO), polyvinylidene fluoride (PVdF), and polymethylmethacrylate. One type of the binder may be used alone, or a plurality of types may be mixed and used.

The ratio of the weight of the binder to the weight of the composite electrolyte layer is, for example, in the range of 0.1 wt % to 10 wt %, preferably in the range of 0.5 wt % to 5 wt %. If the ratio of the weight of the binder to the weight of the composite electrolyte layer is too low, the binding strength is weak and the composite electrolyte layer tends to come off, making it impossible to retain the solid electrolyte particles. Conversely, if it is too high, the movement of lithium ions will be hindered, and ion diffusion resistance will tend to increase.

A composite electrolyte layer can include an inorganic compound with alumina instead of a solid electrolyte. Therefore, the composite electrolyte layer can contain at least one of a solid electrolyte and an inorganic compound having alumina. Inorganic compounds containing alumina include, for example, mullite (for example represented by the chemical formula 3Al ₂ O ₃ .2SiO ₂ to 2Al ₂ O ₃ .SiO ₂ ), cordierite (for example represented by the chemical formula 2MgO.2Al ₂ O ₃ .5SiO _{2 )} . ), ceramic fibers (eg, alumina fibers, alkaline earth silicate wool, refractory ceramic fibers, etc.), alumina composites containing polymer materials, etc., silica-alumina (eg, zeolite, etc.), and the like. For the sake of convenience, the inorganic compound containing alumina also includes a simple substance of alumina. When it is called alumina, it means alumina simple substance. These inorganic compounds containing alumina may be used alone or in combination of two or more. Moreover, you may use with the solid electrolyte mentioned above.

Among the inorganic compounds containing alumina, alumina is particularly preferred. This is because the inclusion of alumina in the composite electrolyte layer can further suppress gas generation.

The ratio of the weight of the inorganic compound containing alumina to the weight of the composite electrolyte layer is, for example, 10% or more and 90% or less.

The average particle size of the inorganic compound containing alumina is preferably 0.1 μm or more and 10 μm or less. If it is less than 0.1 μm, the amount of solvent contained in the particles of the inorganic compound having alumina becomes too large, so that the decomposition reaction of the non-aqueous electrolyte is excessively promoted, resulting in a decrease in rate characteristics and a shortened battery life. This is not preferable because it lowers the battery performance. If it is larger than 10 μm, the voids between the particles increase, making it difficult to make the composite electrolyte thin, which is not preferable. More preferably, it is 0.1 μm or more and 5 μm or less. Within this range, the decomposition reaction of the non-aqueous electrolyte is moderately promoted, and the gaps between the inorganic compound having alumina and the solid electrolyte particles are also moderate, so that the composite electrolyte can be kept thin and the ionic conductivity can be better maintained. Therefore, it is more preferable.

The average particle size of the inorganic compound containing alumina is the same as the method for measuring the average particle size of the particles of the solid electrolyte described above.

The method for producing the composite electrolyte layer is as follows.
A solid electrolyte and a binder are mixed and applied on the electrode. Any coating method may be used as long as it can be applied uniformly, such as a doctor blade method, a spray method, a microgravure method, a pull-up method, or a spin coating method.

Density can be adjusted by drying after coating and pressing. Pressing is performed by a roll press or the like, and the pressing pressure is in the range of 0.15 ton/mm to 0.3 ton/mm. When the pressing pressure is in this range, the density of the composite electrolyte layer can be 1.0 g/cc or more and 2.2 g/cc or less. Furthermore, the adhesiveness (peel strength) is increased, and the elongation of the electric body becomes 20% or less, which is preferable.

If the pressing pressure is less than 0.15 ton/mm, the density of the composite electrolyte layer cannot be increased to 1.0 g/cc or more, and the peel strength is lowered, which is not preferable. On the other hand, if it is more than 0.3 ton/mm, the density of the composite electrolyte layer becomes too high and the ionic conductivity is lowered, which is not preferable.

The density of the composite electrolyte layer can be measured as follows.

After removing the electrodes from the non-aqueous electrolyte secondary battery and washing them, the composite electrolyte layer is peeled off from the electrodes and the separator. Measure the thickness of the peeled-off composite electrolyte layer with a constant-pressure thickness gauge, etc., cut it into a certain size that shows the area, measure the weight of the composite electrolyte layer before and after coating, and calculate the weight of the composite electrolyte layer alone ÷ It is calculated from (thickness of composite electrolyte layer)/(area of cut composite electrolyte layer). The size to be cut out may be, for example, 2 cm×2 cm. The density and thickness of the composite electrolyte layer are measured at 5 locations, and the average value obtained by excluding the maximum and minimum values of the 5 locations is used.
Alternatively, when it is difficult to peel off the composite electrolyte layer, the electrode after washing is subjected to FIB (Focused Ion Beam) processing, a cross section of the electrode is cut out, and then the cross section of the electrode is observed with a SEM. It can be substituted by measuring the thickness.

(separator)
Examples of electrolyte membranes include porous films made of materials such as polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET), cellulose, and polyvinylidene fluoride (PVdF); Synthetic resin nonwoven fabric or the like can be used. Furthermore, an electrolyte membrane obtained by applying an inorganic compound to a porous film can also be used. A preferred porous film is made of polyethylene or polypropylene, which melts at a certain temperature and can block electric current, thus improving safety.

(positive electrode)
The positive electrode can include a positive electrode current collector and a positive electrode active material layer. The positive electrode active material layer may be formed on one side or both sides of the positive electrode current collector. The positive electrode active material layer may contain a positive electrode active material, and optionally a conductive agent and a binder. Moreover, the positive electrode can also contain the inorganic compound particles according to the first embodiment.

The positive electrode active material is lithium nickel manganese oxide LiM _x Mn _2-x O ₄ (0<X≤0.5, where M is selected from the group consisting of Ni, Cr, Fe, Cu, Co, Mg and Mo) having a spinel structure. at least one selected) is used. At this time, M is preferably Ni, which has high stability.

The positive electrode can further contain another positive electrode active material. For example, oxides, polymers, etc. can be used. Moreover, the positive electrode active material may contain one of these oxides and polymers, or may contain two or more thereof.

Other oxides are, for example, lithium-occluded manganese dioxide (MnO ₂ ), iron oxide, copper oxide, nickel oxide and lithium-manganese composite oxides (e.g. Li _x Mn ₂ O ₄ or Li _x MnO ₂ ), lithium nickel composite oxides (eg, Li _x NiO ₂ ), lithium phosphorous oxides having an olivine structure (eg, Li _x FePO ₄ , Li _x Fe _{1-y Mny} PO ₄ ), iron sulfate (Fe ₂ (SO ₄ ) ₃ ), Or vanadium oxide (eg V ₂ O ₅ ) can be used. The above x and y are preferably 0<x≦1 and 0≦y≦1.

As the polymer, for example, a conductive polymer material such as polyaniline or polypyrrole, or a disulfide-based polymer material can be used. Sulfur (S) and carbon fluoride can also be used as active materials.

As the positive electrode current collector, it is preferable to use an aluminum foil or an aluminum alloy foil with a purity of 99% or more. The aluminum alloy is preferably an alloy containing, in addition to aluminum, one or more elements selected from the group consisting of iron, magnesium, zinc, manganese and silicon. For example, Al--Fe alloys, Al--Mn based alloys and Al--Mg based alloys are capable of obtaining higher strength than aluminum.

Examples of conductive agents for increasing electronic conductivity and suppressing contact resistance with the current collector include acetylene black, carbon black, and graphite.

Examples of binders for binding the active material and the conductive agent include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), and fluororubber.

The compounding ratio of the positive electrode active material, the conductive agent and the binder in the positive electrode active material layer is 80% by weight or more and 95% by weight or less of the positive electrode active material, 3% by weight or more and 18% by weight or less of the conductive agent, and 2% by weight of the binder. It is preferably within the range of 7% by weight or more and 7% by weight or less. When the conductive agent is 3% by weight or more, the above effects can be exhibited, and when it is 18% by weight or less, decomposition of the non-aqueous electrolyte on the surface of the conductive agent can be reduced under high temperature storage. When the binder is 2% by weight or more, sufficient electrode strength can be obtained, and when it is 7% by weight or less, the insulating portion of the electrode can be reduced.

A positive electrode can be produced, for example, by the following method. First, a slurry is prepared by suspending a positive electrode active material, a conductive agent, and a binder in a solvent. This slurry is applied to one side or both sides of the positive electrode current collector. Next, the applied slurry is dried to obtain a laminate of the positive electrode active material layer and the positive electrode current collector. After that, the laminate is pressed. The positive electrode press pressure is preferably in the range of 0.15 ton/mm to 0.3 ton/mm. When the positive electrode pressing pressure is within this range, the adhesiveness (peel strength) between the positive electrode active material layer and the positive electrode current collector increases, and the elongation rate of the positive electrode current collector becomes 20% or less, which is preferable. Thus, a positive electrode is produced. Alternatively, the positive electrode may be produced by the following method. First, a positive electrode active material, a conductive agent, and a binder are mixed to obtain a mixture. The mixture is then formed into pellets. A positive electrode can then be obtained by placing these pellets on a positive electrode current collector.

(negative electrode)
The negative electrode can include a negative electrode current collector and a negative electrode active material layer. The negative electrode active material layer may be formed on one side or both sides of the negative electrode current collector. The negative electrode active material layer may include a negative electrode active material, and optionally a conductive agent and a binder.

Examples of negative electrode active materials include carbon materials, graphite materials, lithium alloy materials, metal oxides and metal sulfides. It is preferable to select the negative electrode active material of one or more titanium composite oxides selected from titanium oxide, titanium oxide, niobium titanium oxide, and lithium sodium niobium titanium oxide. These can be used singly or in combination.

Lithium-titanium composite oxides can be represented by the general formula Li _4+x Ti ₅ O ₁₂ (where x is −1≦ _x ≦ ₃ ). x) (TiO ₂ (B) as the structure before charging), rutile structure, Li _a TiM _b Nb _2±β O _7±σ (0≦a≦5, 0 ≤ b ≤ 0.3, 0 ≤ β ≤ 0.3, 0 ≤ σ ≤ 0.3, M is at least one element selected from the group consisting of Fe, V, Mo and Ta) niobium titanium represented by oxides, anatase-type titanium composite oxides (TiO ₂ as the structure before charging) and Li _2+x Ti ₃ O _{7 ,} Li _1+x Ti ₂ O _{4 ,} Li _1.1+x Ti _1.8 O _{4 ,} Li _1.07+x Ti _1.86 O _{4 ,} Li _x TiO ₂ (where x is 0≦x) and the like, and Ti _1-x M1 _x Nb _2-y M2 _y O _{7- δ} (0≦x<1, 0≦y<1, M1 and M2 contain at least one of Mg, Fe, Ni, Co, W, Ta and Mo, and the element M1 and the element M2 are the same lithium sodium niobium titanium oxide Li _2+v Na _2-w M1 _x Ti _6-yz Nb _y M2 _z O _{14+ δ} (M1 is Cs; K, Sr, Ba, Ca, and M include at least one of Zr, Sn, V, Ta, Mo, W, Fe, Co, Mn, and Al, and 0≤v≤4, 0<w<2, 0 ≦x<2, 0<y≦6, 0≦z<3, −0.5≦δ≦0.5). Among them, lithium titanate having a spinel structure is preferable because it is excellent in cycle characteristics and rate characteristics. In addition, niobium composite oxide may be included. For _example , _Nb2O5 , _Nb12O29 , etc. are mentioned _.

The negative electrode active material particles preferably have an average particle size of 1 μm or less and a specific surface area of 3 m ² /g to 200 m ² /g as determined by the BET method by N ₂ adsorption. Thereby, affinity with the non-aqueous electrolyte of the negative electrode can be increased.

The reason for defining the specific surface area of the negative electrode in the above range will be explained. If the specific surface area is less than 3 m ² /g, aggregation of particles is conspicuous, the affinity between the negative electrode and the non-aqueous electrolyte is lowered, and the interfacial resistance of the negative electrode is increased. As a result, output characteristics and charge/discharge cycle characteristics are degraded. On the other hand, if the specific surface area exceeds 50 m ² /g, the distribution of the non-aqueous electrolyte is biased toward the negative electrode, which may lead to a shortage of the non-aqueous electrolyte at the positive electrode. do not have. A more preferable range of the specific surface area is 5 to 50 m ² /g. Here, the specific surface area of the negative electrode means the surface area per 1 g of the negative electrode active material layer (excluding the weight of the current collector). The negative electrode active material layer is a porous layer containing a negative electrode active material, a conductive agent, and a binder supported on a current collector.

The porosity of the negative electrode (excluding the current collector) is preferably in the range of 20-50%. This makes it possible to obtain a high-density negative electrode having excellent affinity between the negative electrode and the non-aqueous electrolyte. A more preferred range of porosity is 25-40%.

For the negative electrode current collector, a material that is electrochemically stable at the lithium absorption and release potentials of the negative electrode active material is used. The negative electrode current collector is preferably made of copper, nickel, stainless steel, aluminum, or an aluminum alloy containing one or more elements selected from Mg, Ti, Zn, Mn, Fe, Cu, and Si. The thickness of the negative electrode current collector is preferably in the range of 5 μm or more and 20 μm or less. A negative electrode current collector having such a thickness can balance the strength and weight reduction of the negative electrode. The negative electrode active material is contained in the negative electrode in the form of particles, for example. The negative electrode active material particles can be single primary particles, secondary particles that are aggregates of primary particles, or mixtures of single primary particles and secondary particles. From the viewpoint of increasing the density, the negative electrode active material layer preferably contains 5 to 50% by volume of primary particles. The shape of the primary particles is not particularly limited, and can be, for example, spherical, elliptical, flat, fibrous, and the like.

For example, a carbon material can be used as the conductive agent. Examples of carbon materials include acetylene black, carbon black, coke, carbon fiber, graphite, aluminum powder, and TiO. More preferably, the heat treatment temperature is 800° C. to 2000° C., and coke, graphite, or TiO powder having an average particle diameter of 10 μm or less, and carbon fibers having an average fiber diameter of 1 μm or less are preferable. The BET specific surface area by N2 adsorption of the carbon material is preferably 10 m ² /g or more.

Examples of binders include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), fluororubber, styrene-butadiene rubber, and core-shell binders.

The compounding ratio of the negative electrode active material, the conductive agent and the binder is preferably in the range of 80 to 95% by weight of the negative electrode active material, 3 to 18% by weight of the conductive agent, and 2 to 7% by weight of the binder. . If the conductive agent is less than 3% by mass, the current collecting performance of the negative electrode active material layer may deteriorate, and the large current characteristics of the non-aqueous electrolyte secondary battery may deteriorate. On the other hand, if the binder content is less than 2% by mass, the binding between the negative electrode active material layer and the negative electrode current collector may deteriorate, and the cycle characteristics may deteriorate. On the other hand, from the viewpoint of increasing the capacity, it is preferable that each of the conductive agent and the binder is 10% by mass or less.

A negative electrode can be produced, for example, by the following method. First, a slurry is prepared by suspending a negative electrode active material, a conductive agent, and a binder in an appropriate solvent. This slurry is then applied to one or both sides of the negative electrode current collector. A negative electrode active material layer is formed by drying the coating film on the negative electrode current collector. Thereafter, the negative electrode current collector and the negative electrode active material layer formed thereon are pressed. As the negative electrode active material layer, a pellet obtained by forming a negative electrode active material, a conductive agent, and a binder may be used.

As described above, in the electrode group according to the first embodiment, the lithium composite oxide LiM _x Mn _2-x O ₄ (0<X≦0.5, M is Ni, Cr, Fe, Cu, a positive electrode containing at least one selected from the group consisting of Co, Mg and Mo; a negative electrode containing a negative electrode active material; and a composite electrolyte layer containing at least one of a solid electrolyte and an inorganic compound having alumina between the negative electrode and the positive electrode. and a separator, and the composite electrolyte layer has a density of 1.0 g/cc or more and 2.2 g/cc or less.

With the electrode group having such a configuration, it is possible to provide a non-aqueous electrolyte secondary battery that suppresses gas generation and has good rate characteristics and a high battery voltage.

(Second embodiment)
A non-aqueous electrolyte secondary battery according to the second embodiment includes the electrode group according to the first embodiment, a non-aqueous electrolyte, and an exterior member.

Each member of the non-aqueous electrolyte secondary battery according to the second embodiment will be described below.

(electrode group)
Since the electrode group is the same as that described in the first embodiment, the description thereof will be omitted.

(Non-aqueous electrolyte)
A non-aqueous electrolyte includes an organic solvent and an electrolyte salt. The organic solvent should be one that does not easily melt the composite electrolyte layer and can exist stably.

As the non-aqueous electrolyte, a liquid non-aqueous electrolyte or a gel non-aqueous electrolyte can be used. A liquid non-aqueous electrolyte is prepared by dissolving an electrolyte salt in an organic solvent. The electrolyte salt concentration is preferably in the range of 0.5 to 2.5 mol/l. A gel-like non-aqueous electrolyte is prepared by combining a liquid non-aqueous electrolyte and a polymer material. Liquid non-aqueous electrolytes are preferable because they have higher Li conductivity than gel-like non-aqueous electrolytes and provide excellent input/output characteristics.

Examples of organic solvents are N-methyl-2-pyrrolidone (NMP), propylene carbonate (PC), ethylene carbonate (EC), cyclic carbonates such as vinylene carbonate; diethyl carbonate (DEC), dimethyl carbonate (DMC), methyl ethyl carbonate. acyclic carbonates such as (MEC); cyclic ethers such as tetrahydrofuran (THF), 2methyltetrahydrofuran (2MeTHF), dioxolane (DOX); acyclic ethers such as dimethoxyethane (DME) and diethoethane (DEE) or gamma-butyrolactone (GBL), acetonitrile (AN), sulfolane (SL), and the like can be used. These organic solvents can be used alone or in the form of a mixed solvent.

Electrolyte salts include lithium perchlorate ( _LiClO4 ), lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate ( _LiBF4 ), lithium arsenic hexafluoride ( _LiAsF6 ), lithium trifluoromethanesulfonate _. (LiCF ₃ SO ₃ ), lithium bistrifluoromethylsulfonylimide [LiN(CF ₃ SO ₂ ) ₂ ], or a mixture thereof. The organic electrolyte may contain other electrolyte salts.

(Exterior material)
As the exterior member, a laminated film bag-like container or a metal container is used.

Shapes include flat type, square type, cylindrical type, coin type, button type, sheet type, laminated type, and the like. Needless to say, in addition to small-sized batteries mounted on portable electronic devices, large-sized batteries mounted on two-wheeled or four-wheeled automobiles, etc., may also be used.

A multilayer film in which a metal layer is interposed between resin films is used as the laminate film. The metal layer is preferably aluminum foil or aluminum alloy foil for weight reduction. Polymer materials such as polypropylene (PP), polyethylene (PE), nylon, and polyethylene terephthalate (PET) can be used for the resin film. The laminate film can be formed into the shape of the exterior member by performing sealing by heat sealing. The laminate film preferably has a thickness of 0.2 mm or less. In addition, the laminated film used for the exterior member is not limited to one in which a metal layer is interposed between two resin films, and a multilayer film composed of a metal layer and a resin layer covering the metal layer can be used. .

Metal containers can be formed from aluminum or an aluminum alloy. The aluminum alloy preferably contains elements such as magnesium, zinc and silicon. On the other hand, the content of transition metals such as iron, copper, nickel and chromium is preferably 100 ppm or less. This makes it possible to dramatically improve long-term reliability and heat dissipation in a high-temperature environment. The metal container preferably has a thickness of 0.5 mm or less, more preferably 0.2 mm or less.

(Positive terminal)
The positive electrode terminal is made of a material that is electrically stable and conductive in a potential range of 3.0 V or more and 5.5 V or less with respect to lithium ion metal. It is preferably formed from aluminum or an aluminum alloy containing elements such as Mg, Ti, Zn, Mn, Fe, Cu and Si. In order to reduce contact resistance with the positive electrode current collector, the positive electrode terminal is preferably made of the same material as the positive electrode current collector.

(negative terminal)
The negative electrode terminal is made of a material that is electrically stable and conductive in a potential range of 1.0 V or more and 3.0 V or less with respect to lithium ion metal. It is preferably made of aluminum or an aluminum alloy containing elements such as Mg, Ti, Zn, Mn, Fe, Cu, Si. In order to reduce contact resistance with the negative electrode current collector, the negative electrode terminal is preferably made of the same material as the negative electrode current collector.

Hereinafter, the non-aqueous electrolyte secondary battery according to the second embodiment will be described more specifically with reference to FIGS. 2 and 3. FIG. However, the non-aqueous electrolyte secondary battery according to the second embodiment is not limited to the following electrode group. 2 is a cross-sectional view of a flat-type non-aqueous electrolyte secondary battery 10 according to the first embodiment, and FIG. 3 is an enlarged cross-sectional view of part A in FIG.

A flat wound electrode group 1 is housed in a bag-shaped exterior member 2 made of a laminate film in which a metal layer is interposed between two resin films. The flat-shaped wound electrode group 1 is formed by spirally winding and press-molding a laminate in which the negative electrode 3, the composite electrolyte layer 8, the separator 4, the positive electrode 5, and the separator 4 are laminated in this order from the outside. . As shown in FIG. 3, the outermost negative electrode 3 has a structure in which a negative electrode active material layer 3b containing a negative electrode active material is formed on one inner surface of a negative electrode current collector 3a. The negative electrode active material layer 3b is formed on both surfaces of the electric body 3a. The positive electrode 5 is configured by forming positive electrode active material layers 5b on both sides of a positive electrode current collector 5a.

In the vicinity of the outer peripheral end of the wound electrode group 1, the negative electrode terminal 6 is connected to the negative electrode current collector 3a of the outermost negative electrode 3, and the positive electrode terminal 7 is connected to the positive electrode current collector 5a of the inner positive electrode 5. These negative terminal 6 and positive terminal 7 are extended outside from the opening of the bag-shaped exterior member 2 . For example, a liquid non-aqueous electrolyte is injected from the opening of the bag-like exterior member 2 . The wound electrode group 1 and the liquid non-aqueous electrolyte are completely sealed by heat-sealing the opening of the bag-shaped exterior member 2 with the negative electrode terminal 6 and the positive electrode terminal 7 sandwiched therebetween.

The non-aqueous electrolyte secondary battery according to the second embodiment is not limited to the configuration shown in FIGS. 2 and 3, and may have the configuration shown in FIGS. 4 and 5, for example. 4 is a partially cutaway perspective view schematically showing another flat type non-aqueous electrolyte secondary battery according to the first embodiment, and FIG. 5 is an enlarged cross-sectional view of part B in FIG. The composite electrolyte layer is not shown in FIG. 5 for the sake of complication.

The laminated electrode group 11 is housed in an exterior member 12 made of a laminate film in which a metal layer is interposed between two resin films. As shown in FIG. 5, the laminated electrode group 11 has a structure in which positive electrodes 13 and negative electrodes 14 are alternately laminated with a composite electrolyte layer and a separator 15 interposed therebetween. A plurality of positive electrodes 13 are present, each of which includes a current collector 13a and a positive electrode active material layer 13b carried on both sides of the current collector 13a. A plurality of negative electrodes 14 are present, each of which includes a current collector 14a and negative electrode active material layers 14b supported on both sides of the current collector 14a. One side of the current collector 14 a of each negative electrode 14 protrudes from the positive electrode 13 . The projecting current collector 14 a is electrically connected to a strip-shaped negative electrode terminal 16 . The tip of the strip-shaped negative electrode terminal 16 is pulled out from the exterior member 12 . Moreover, although not shown, the current collector 13 a of the positive electrode 13 has a side opposite to the projecting side of the current collector 14 a protruding from the negative electrode 14 . A current collector 13 a protruding from the negative electrode 14 is electrically connected to a strip-shaped positive electrode terminal 17 . The tip of the strip-shaped positive electrode terminal 17 is located on the opposite side of the negative electrode terminal 16 and is pulled out from the side of the exterior member 12 .

The non-aqueous electrolyte secondary battery according to the second embodiment described above includes the electrode group according to the first embodiment and a non-aqueous electrolyte. With such a non-aqueous electrolyte secondary battery, it is possible to suppress the electrolyte decomposition reaction and gas generation while maintaining the input/output characteristics of the cell. The following batteries can be provided.

(Third embodiment)
A battery pack according to the third embodiment has one or a plurality of non-aqueous electrolyte secondary batteries (single cells) of the second embodiment described above. When a plurality of single cells are provided, each single cell is electrically connected in series or in parallel.

Such a battery pack will be described in detail with reference to FIGS. 6 and 7. FIG. A flat battery shown in FIG. 2 can be used as the single battery.

A plurality of unit cells 21 composed of the flat-type non-aqueous electrolyte cells shown in FIG. The assembled battery 23 is configured by fastening. These cells 21 are electrically connected in series with each other as shown in FIG.

The printed wiring board 24 is arranged to face the side surface of the cell 21 from which the negative terminal 6 and the positive terminal 7 extend. As shown in FIG. 7, the printed wiring board 24 is mounted with a thermistor 25, a protective circuit 26, and a terminal 27 for supplying power to an external device. An insulating plate (not shown) is attached to the surface of the protection circuit board 24 facing the assembled battery 23 in order to avoid unnecessary connection with the wiring of the assembled battery 23 .

The positive lead 28 is connected to the positive terminal 7 located at the bottom layer of the assembled battery 23, and its tip is inserted into the positive connector 29 of the printed wiring board 24 and electrically connected. The negative lead 30 is connected to the negative terminal 6 located on the uppermost layer of the assembled battery 23, and its tip is inserted into the negative connector 31 of the printed wiring board 24 and electrically connected. These connectors 29 and 31 are connected to the protection circuit 26 through wirings 32 and 33 formed on the printed wiring board 24 .

FIG. 8 is a block diagram showing the electric circuit of the battery pack of FIG. 7, so to explain with reference to FIG. The temperature of battery 21 is detected and the detection signal is sent to protection circuit 26 . The protection circuit 26 can cut off the plus side wiring 34a and the minus side wiring 34b between the protection circuit 26 and the terminal 27 for energizing the external device under predetermined conditions. The predetermined condition is, for example, when the temperature detected by the thermistor 25 is equal to or higher than a predetermined temperature. Further, the predetermined condition is when overcharge, overdischarge, overcurrent, or the like of the cell 21 is detected. The detection of overcharging or the like is performed for each unit cell 21 or the unit cells 21 as a whole. When detecting the individual cells 21, the battery voltage may be detected, or the positive electrode potential or the negative electrode potential may be detected. In the latter case, a lithium electrode used as a reference electrode is inserted into each unit cell 21 . In the case of FIGS. 6 and 7 , wiring 35 for voltage detection is connected to each of the cells 21 , and a detection signal is transmitted to the protection circuit 26 through these wirings 35 .

Protective sheets 36 made of rubber or resin are arranged on three side surfaces of the assembled battery 23 excluding the side surface from which the positive electrode terminal 7 and the negative electrode terminal 6 protrude.

The assembled battery 23 is housed in a housing container 37 together with each protective sheet 36 and the printed wiring board 24 . That is, the protective sheets 36 are arranged on both inner surfaces in the long-side direction and the inner surface in the short-side direction of the storage container 37, and the printed wiring board 24 is arranged on the inner surface on the opposite side in the short-side direction. The assembled battery 23 is positioned within a space surrounded by the protective sheet 36 and the printed wiring board 24 . A lid 38 is attached to the upper surface of the storage container 37 .

A heat-shrinkable tape may be used instead of the adhesive tape 22 for fixing the assembled battery 23 . In this case, protective sheets are placed on both sides of the assembled battery, the heat-shrinkable tube is wound around the assembled battery, and then the heat-shrinkable tube is heat-shrunk to bind the assembled battery.

6 and 7 show the form in which the cells 21 are connected in series, they may be connected in parallel in order to increase the battery capacity. Assembled battery packs can be connected in series or in parallel.

Moreover, the assembled battery 23 shown in FIG. 6 and the battery pack 200 shown in FIG. good.

Moreover, the embodiment of the battery pack is appropriately changed depending on the application. The battery pack according to the present embodiment is suitable for applications that require excellent cycle performance when a large current is extracted. Specifically, it can be used as a power supply for a digital camera.

Since the battery pack according to this embodiment includes the non-aqueous electrolyte battery according to the second embodiment, it can exhibit excellent rate characteristics.

(Fourth embodiment)
According to a fourth embodiment, a vehicle is provided. This vehicle is equipped with the battery pack according to the third embodiment.

In the vehicle according to the fourth embodiment, the battery pack recovers, for example, regenerative energy of power of the vehicle.

Examples of vehicles according to the fourth embodiment include two- to four-wheeled hybrid electric vehicles, two- to four-wheeled electric vehicles, assisted bicycles, and railway vehicles.

The mounting position of the battery pack in the vehicle according to the fourth embodiment is not particularly limited. For example, when the battery pack is installed in an automobile, the battery pack can be installed in the engine compartment of the vehicle, behind the vehicle body, or under the seat.

Next, an example of a vehicle according to a fourth embodiment will be described with reference to the drawings.

FIG. 9 is a cross-sectional view schematically showing an example of a vehicle according to the fourth embodiment.

A vehicle 300 shown in FIG. 9 includes a vehicle body 301 and a battery pack 302 . The battery pack 302 may be the battery pack according to the third embodiment.

A vehicle 300 shown in FIG. 9 is a four-wheel automobile. As the vehicle 300, for example, a two- to four-wheeled hybrid electric vehicle, a two- to four-wheeled electric vehicle, an assisted bicycle, and a railway vehicle can be used.

This vehicle 300 may be equipped with a plurality of battery packs 302 . In this case, the battery packs 202 may be connected in series, connected in parallel, or connected in a combination of series connection and parallel connection.

Battery pack 202 is mounted in an engine room located in front of vehicle body 301 . The mounting position of battery pack 302 is not particularly limited. The battery pack 202 may be mounted behind the vehicle body 301 or under the seat. This battery pack 302 can be used as a power source for the vehicle 300 . Also, this battery pack 302 can recover the regenerated energy of the power of the vehicle 300 .

Next, an embodiment of the vehicle according to the fourth embodiment will be described with reference to FIG.

FIG. 10 is a diagram schematically showing another example of the vehicle according to the fourth embodiment. A vehicle 300 shown in FIG. 10 is an electric vehicle.

A vehicle 300 shown in FIG. 10 includes a vehicle main body 301, a vehicle power source 302, a vehicle ECU (ECU: Electric Control Unit) 380 that is a host control means of the vehicle power source 302, and an external terminal (external power source 370 , an inverter 340 , and a drive motor 345 .

A vehicle 300 has a vehicle power supply 302 mounted, for example, in the engine room, behind the vehicle body, or under the seat. In the vehicle 300 shown in FIG. 10, the locations where the vehicle power source 302 is mounted are schematically shown.

The vehicle power supply 302 includes a plurality (eg, three) of battery packs 312a, 312b, and 312c, a battery management unit (BMU) 311, and a communication bus 310.

The three battery packs 312a, 312b and 312c are electrically connected in series. The battery pack 312a includes an assembled battery 314a and an assembled battery monitoring device (VTM: Voltage Temperature Monitoring) 313a. The battery pack 312b includes an assembled battery 314b and an assembled battery monitoring device 313b. The battery pack 312c includes an assembled battery 314c and an assembled battery monitoring device 313c. Battery packs 312 a , 312 b , and 312 c can each be independently removed and replaced with another battery pack 312 .

Each of the assembled batteries 314a-314c includes a plurality of single cells connected in series. At least one of the plurality of cells is the secondary battery according to the second embodiment. The assembled batteries 314a to 314c charge and discharge through the positive terminal 316 and the negative terminal 317, respectively.

The battery management device 311 communicates with the assembled battery monitoring devices 313a to 313c in order to collect information on maintenance of the vehicle power supply 302, Collect information about battery voltage, temperature, etc.

A communication bus 310 is connected between the battery management device 311 and the assembled battery monitoring devices 313a to 313c. The communication bus 310 is configured such that one set of communication lines is shared by a plurality of nodes (battery management device and one or more assembled battery monitoring devices). The communication bus 310 is, for example, a communication bus configured based on the CAN (Control Area Network) standard.

The assembled battery monitoring devices 313a to 313c measure the voltage and temperature of the individual single cells that make up the assembled batteries 314a to 314c based on commands from the battery management device 311 through communication. However, the temperature can be measured at only a few points per assembled battery, and it is not necessary to measure the temperature of all the single cells.

The vehicle power supply 302 may also have an electromagnetic contactor (eg, the switch device 333 shown in FIG. 10) for turning on and off the connection between the positive terminal 316 and the negative terminal 317 . The switch device 333 includes a precharge switch (not shown) that is turned on when the assembled batteries 314a to 314c are charged, and a main switch (not shown) that is turned on when the battery output is supplied to the load. contains. The precharge switch and the main switch each have a relay circuit (not shown) that is turned on or off by a signal supplied to a coil arranged near the switch element.

Inverter 340 converts the input DC voltage into a three-phase alternating current (AC) high voltage for driving the motor. Three-phase output terminals of the inverter 340 are connected to respective three-phase input terminals of the drive motor 345 . Inverter 340 controls the output voltage based on a control signal from battery management device 311 or vehicle ECU 380 for controlling the operation of the entire vehicle.

Drive motor 345 is rotated by power supplied from inverter 340 . This rotation is transmitted to the axles and drive wheels W, for example, via a differential gear unit.

In addition, although not shown, vehicle 300 includes a regenerative braking mechanism. The regenerative braking mechanism rotates drive motor 345 when vehicle 300 is braked, and converts kinetic energy into regenerative energy as electrical energy. The regenerative energy recovered by the regenerative braking mechanism is input to inverter 340 and converted to direct current. The DC current is input to vehicle power supply 302 .

One terminal of the connection line L<b>1 is connected to the negative terminal 317 of the vehicle power source 302 via a current detector (not shown) in the battery management device 311 . The other terminal of connection line L1 is connected to the negative input terminal of inverter 340 .

One terminal of the connection line L<b>2 is connected to the positive terminal 316 of the vehicle power source 302 via the switch device 333 . The other terminal of connection line L2 is connected to the positive input terminal of inverter 340 .

The external terminal 370 is connected to the battery management device 311 . The external terminal 370 can be connected to, for example, an external power supply.

Vehicle ECU 380 cooperatively controls battery management device 311 together with other devices in response to an operation input by a driver or the like to manage the entire vehicle. Between the battery management device 311 and the vehicle ECU 380, data transfer related to the maintenance of the vehicle power source 302, such as the remaining capacity of the vehicle power source 302, is performed via a communication line.

A vehicle according to the fourth embodiment includes the battery pack according to the third embodiment. That is, since the vehicle according to the fourth embodiment is equipped with a battery pack with high cycle performance, it has excellent rate characteristics, and since the battery pack has excellent life performance, it is possible to provide a highly reliable vehicle. can be done.

[Example]
A non-aqueous electrolyte secondary battery was produced in the following procedure.

<Preparation of positive electrode>
100 parts by weight of spinel-type lithium nickel composite oxide (LiNi _0.5 Mn _1.5 O ₄ ) powder as a positive electrode active material, 5 parts by weight of acetylene black as a conductive agent, and polyvinylidene fluoride (PVdF) as a binder 2 parts by weight were added to N-methylpyrrolidone (NMP) and mixed to prepare a slurry. A positive electrode was obtained by coating both surfaces of a current collector made of aluminum foil having a thickness of 12 μm, drying in a constant temperature bath at 120° C., and pressing.

<Production of negative electrode>
Mix 100 parts by weight of lithium titanate powder as a negative electrode active material, 4 parts by weight of acetylene black as a conductive agent, and 2 parts by weight of polyvinylidene fluoride (PVdF) as a binder with N-methylpyrrolidone (NMP). to prepare a slurry. This slurry was applied to both sides of a current collector made of aluminum foil having a thickness of 12 μm, dried in a constant temperature bath at 120° C. and pressed to obtain a negative electrode.

<Preparation of Composite Electrolyte Layer>
LATP (Li _1.4 Al _0.4 Ti _1.6 (PO ₄ ) ₃ ) particles with an average particle size of 1 μm and PVdF were mixed at a ratio of 9:1, diluted with NMP to prepare a slurry, applied on the positive electrode, and a composite electrolyte was formed on the positive electrode. A layer was made. A polyethylene nonwoven fabric having a thickness of 25 μm was used as the separator.

<Production of electrode group>
A positive electrode coated with a composite electrolyte layer, a separator, a negative electrode, and a separator were laminated in this order to obtain a laminate. This laminate was then spirally wound. A flat electrode group was produced by hot-pressing this at 80°C. The obtained electrode group is housed in a pack made of a laminate film having a three-layer structure of nylon layer/aluminum layer/polyethylene layer and having a thickness of 0.1 mm, and dried in vacuum at 120° C. for 16 hours. bottom.

<Preparation of non-aqueous electrolyte>
A non-aqueous electrolyte was obtained by dissolving 1 mol/L of LiPF ₆ as an electrolyte in a mixed solvent of propylene carbonate (PC) and diethyl carbonate (DEC) (volume ratio 1:2). Electrolyte adjustments were performed in an argon box.

After the non-aqueous electrolyte was injected into the laminate film pack containing the electrode group, the pack was completely sealed by heat sealing. Thus, a non-aqueous electrolyte secondary battery was obtained.

<Performance evaluation>
The battery was tested in a 25°C environment. In charging and discharging, the battery was first charged to 3.5 V at 100 mA, then discharged to 2.5 V at 20 mA to check the capacity of the battery, and then discharged at a discharge current of 1 A to check the capacity of the battery. After that, charging and discharging were repeated 200 cycles at 100 mA, and the amount of gas generated and the discharge capacity retention rate were compared. The results are shown in Table 2.

<Measurement of density and thickness of composite electrolyte layer>
After performance evaluation, the battery was disassembled and the density and thickness of the composite electrolyte layer were measured. First, the composite electrolyte layer was peeled off from the battery, and a 2 cm×2 cm sample piece was cut out. The thickness of the sample piece was 21 μm. Based on these results, the density of the composite non-aqueous electrolyte was measured and found to be 1.5 g/cc.

Hereinafter, for Examples 2-30 and Comparative Examples 1-7, Table 1-6 also shows the type and average particle size of the solid electrolyte or inorganic compound having alumina, the position of the composite electrolyte layer, the density of the composite electrolyte layer, the composite electrolyte The thickness of , the amount of gas generated, and the discharge capacity retention rate are listed together.

(Example 2)
A non-aqueous electrolyte secondary battery was fabricated and evaluated in the same manner as in Example 1, except that the composite electrolyte layer was formed on the negative electrode and the thickness was set to 23 μm.

(Example 3)
A non-aqueous electrolyte secondary battery was fabricated and evaluated in the same manner as in Example 1, except that the composite electrolyte layer was formed on the separator and the thickness was set to 22 μm.

(Example 4)
A non-aqueous electrolyte secondary battery was fabricated and evaluated in the same manner as in Example 1, except that the composite electrolyte layer was formed on both the negative electrode and the positive electrode, and the thickness was 20 μm on the negative electrode side and 21 μm on the positive electrode side. did

(Example 5)
A nonaqueous electrolyte secondary battery was fabricated and evaluated in the same manner as in Example 2, except that the thickness of the composite electrolyte layer was set to 2 μm.

(Example 6)
Except that the solid electrolyte of Example 2 was changed to _Li7La3Zr2O12 and the thickness of _the composite electrolyte layer _was changed to 5 μm, an electrode was produced in the same manner as in _Example 2, and a non-aqueous electrolyte secondary battery was produced and evaluated. rice field.

(Example 7)
An electrode was prepared in the same manner except that the solid electrolyte of Example 2 was changed to Li _0.5 La _0.5 TiO ₃ having an average particle size of 2 μm and the thickness of the composite electrolyte layer was changed to 4 μm. A battery was produced and evaluated.

(Example 8)
Li _3.6 Si _0.6 PO ₄ was used as the solid electrolyte of Example 2, and the thickness of the composite electrolyte layer was changed to 10 μm. made an evaluation.

(Example 9)
An electrode was prepared in the same manner except that the solid electrolyte of Example 2 was changed to LIPON (Li _2.9 PO _3.3 N _0.46 ) having an average particle size of 3 μm and the thickness of the composite electrolyte layer was 11 μm, A non-aqueous electrolyte secondary battery was produced and evaluated.

(Example 10)
An electrode was produced in the same manner as in Example 1 except that the composite electrolyte layer had a density of 1.0 g/cc and a thickness of 10 μm, and a non-aqueous electrolyte secondary battery was produced and evaluated.

(Example 11)
An electrode was produced in the same manner as in Example 2 except that the composite electrolyte layer had a density of 1.0 g/cc and a thickness of 15 μm, and a non-aqueous electrolyte secondary battery was produced and evaluated.

(Example 12)
An electrode was produced in the same manner as in Example 1 except that the composite electrolyte layer had a density of 2.1 g/cc and a thickness of 22 μm, and a non-aqueous electrolyte secondary battery was produced and evaluated.

(Example 13)
An electrode was produced in the same manner as in Example 2 except that the composite electrolyte layer had a density of 2.2 g/cc and a thickness of 2 μm, and a non-aqueous electrolyte secondary battery was produced and evaluated.

(Example 14)
An electrode was produced in the same manner as in Example 6 except that the composite electrolyte layer had a density of 1.2 g/cc and a thickness of 3 μm, and a non-aqueous electrolyte secondary battery was produced and evaluated.

(Example 15)
An electrode was produced in the same manner as in Example 6 except that the composite electrolyte layer had a density of 2.2 g/cc and a thickness of 2 μm, and a non-aqueous electrolyte secondary battery was produced and evaluated.

(Example 16)
An electrode was produced in the same manner as in Example 1 except that the thickness of the composite electrolyte layer was 0.2 μm, and a non-aqueous electrolyte secondary battery was produced and evaluated.

(Example 17)
An electrode was produced in the same manner as in Example 1 except that the thickness of the composite electrolyte layer was 76 μm, and a non-aqueous electrolyte secondary battery was produced and evaluated.

(Example 18)
An electrode was produced in the same manner as in Example 1 except that the thickness of the composite electrolyte layer was 97 μm, and a non-aqueous electrolyte secondary battery was produced and evaluated.

(Example 19)
An electrode was produced in the same manner as in Example 1 except that the average particle size of the solid electrolyte was 9.8 μm, and a non-aqueous electrolyte secondary battery was produced and evaluated.

(Example 20)
An electrode was produced in the same manner as in Example 1 except that the average particle size of the solid electrolyte was 0.1 μm, and a non-aqueous electrolyte secondary battery was produced and evaluated.

(Example 21)
An electrode was produced in the same manner as in Example 1 except that the average particle size of the solid electrolyte was 5.5 μm, and a non-aqueous electrolyte secondary battery was produced and evaluated.

(Example 22)
An electrode was produced in the same manner as in Example 1 except that the average particle size of the solid electrolyte was 7.8 μm, and a non-aqueous electrolyte secondary battery was produced and evaluated.

(Example 23)
An electrode was formed in the same manner as in Example 1 except that alumina (Al ₂ O ₃ ) having an average particle size of 1 μm was used as an inorganic compound containing alumina instead of the solid electrolyte, and the density was 1.5 g/cc and the thickness was 10 μm. A non-aqueous electrolyte secondary battery was produced and evaluated.

(Example 24)
An electrode was prepared in the same manner as in Example 1 except that alumina (Al ₂ O ₃ ) having an average particle size of 0.2 μm was used as the inorganic compound containing alumina instead of the solid electrolyte, and the density was 1.5 g/cc and the thickness was 10 μm. was produced, and a non-aqueous electrolyte secondary battery was produced and evaluated.

(Example 25)
An electrode was prepared in the same manner as in Example 1 except that alumina (Al ₂ O ₃ ) having an average particle size of 8 μm was used as the inorganic compound containing alumina instead of the solid electrolyte, and the density was 1.5 g/cc and the thickness was 15 μm. Then, a non-aqueous electrolyte secondary battery was produced and evaluated.

(Example 26)
Example 1 uses a 1:1 mixture of alumina (Al ₂ O ₃ ) having an average particle size of 1 μm and LATP having an average particle size of 1 μm as an inorganic compound having alumina instead of a solid electrolyte. A non-aqueous electrolyte secondary battery was fabricated and evaluated in the same manner except that the electrode was 5 g/cc and the thickness was 10 μm.

(Example 27)
Example 1 is different from Example 1 except that alumina (Al ₂ O ₃ ) having an average particle size of 1 μm was used as an inorganic compound containing alumina instead of the solid electrolyte, the density was 1.5 g/cc, the thickness was 10 μm, and the aluminum oxide was formed on the negative electrode. Electrodes were produced in the same manner, and non-aqueous electrolyte secondary batteries were produced and evaluated.

(Example 28)
In Example 1, alumina (Al ₂ O ₃ ) having an average particle size of 1 μm and mullite (3Al ₂ O _{3.2SiO 2} ) having an average particle size of 1 μm were mixed at a ratio of 1:1 as inorganic compounds having alumina instead of the solid electrolyte. Using the mixed mixture, electrodes were produced in the same manner except that the density was 1.4 g/cc and the thickness was 10 μm, and a non-aqueous electrolyte secondary battery was produced and evaluated.

(Example 29)
In the same manner as in Example 1, mullite (3Al ₂ O ₃ .2SiO ₂ ) having an average particle diameter of 1 μm was used as an inorganic compound having alumina instead of the solid electrolyte, and the density was 1.4 g/cc and the thickness was 10 μm. An electrode was produced, and a non-aqueous electrolyte secondary battery was produced and evaluated.

(Example 30)
In Example 1, mullite (3Al ₂ O ₃ .2SiO ₂ ) having an average particle size of 1 μm and cordierite (2MgO.2Al _{2 O} 3.5SiO ₂ ) having an average particle size of 1 μm were used as inorganic compounds having alumina instead of the solid electrolyte. were mixed at a ratio of 1:1 to prepare an electrode in the same manner except that the density was 1.4 g/cc and the thickness was 10 μm, and a non-aqueous electrolyte secondary battery was prepared and evaluated.

(Comparative example 1)
An electrode was produced in the same manner as in Example 1 except that the composite electrolyte layer was not included, and a non-aqueous electrolyte secondary battery was produced and evaluated.

(Comparative example 2)
An electrode was produced in the same manner as in Example 1 except that the composite electrolyte layer had a density of 2.7 g/cc and a thickness of 23 μm, and a non-aqueous electrolyte secondary battery was produced and evaluated.

(Comparative Example 3)
An electrode was produced in the same manner as in Example 1 except that the composite electrolyte layer had a density of 0.8 g/cc and a thickness of 22 μm, and a non-aqueous electrolyte secondary battery was produced and evaluated.

(Comparative Example 4)
An electrode was produced in the same manner as in Example 2 except that the composite electrolyte layer had a density of 2.7 g/cc and a thickness of 25 μm, and a non-aqueous electrolyte secondary battery was produced and evaluated.

(Comparative Example 5)
An electrode was produced in the same manner as in Example 2 except that the composite electrolyte layer had a density of 0.8 g/cc and a thickness of 2 μm, and a non-aqueous electrolyte secondary battery was produced and evaluated.

(Comparative Example 6)
An electrode was produced in the same manner as in Example 3 except that the composite electrolyte layer had a density of 0.5 g/cc and a thickness of 10 μm, and a non-aqueous electrolyte secondary battery was produced and evaluated.

(Comparative Example 7)
Electrodes were produced in the same manner as in Example 4, except that the composite electrolyte layer had a density of 2.7 g/cc and a thickness of 5 μm on both the negative electrode side and the positive electrode side, and a non-aqueous electrolyte secondary battery was produced and evaluated. did

Comparing Comparative Example 1 and Example 1, it can be confirmed that the presence of the composite electrolyte layer can suppress the generation of gas, and the cycle characteristics are high. It can be confirmed that in Comparative Example 1, due to the absence of the composite electrolyte layer, a large amount of gas is generated and the cycle characteristics are degraded. Comparing Comparative Example 1 with Examples 2 and 3, it can be seen that in Examples 2 and 3, the amount of gas generated can be reduced regardless of the position of the composite electrolyte layer. Moreover, it can be confirmed that even when the thickness of the composite electrolyte is 2 μm as in Example 4, the amount of gas generated can be reduced. Comparing Comparative Example 1 with Examples 5 to 8, regardless of the type of solid electrolyte, the presence of the composite electrolyte reduces the amount of gas generated and improves the cycle characteristics. Comparing Example 5 and Comparative Example 5, in Example 5, the density of the composite electrolyte layer was 1.0 g/cc or more and 2.2 g/cc or less, so the capacity retention rate after 200 cycles was high, and the amount of gas generated was high. is also found to be suppressed. In Comparative Example 5, since the density of the composite electrolyte layer was less than 1.0 g/cc, the capacity retention rate after 200 cycles decreased and the amount of gas generated increased.

Comparing Comparative Example 2 and Example 1, it can be confirmed that in Comparative Example 2, the density of the composite electrolyte layer is high, so that the cycle characteristics and the rate characteristics are significantly degraded. Comparing Comparative Example 3 and Example 1, it can be confirmed that in Comparative Example 3, since the density of the composite electrolyte layer is low, the cycle characteristics and the amount of gas generated are increased.

In Examples 23 to 30, an inorganic compound with alumina was added to the composite electrolyte layer instead of the solid electrolyte. As a result, it was possible to obtain the same results as when a solid electrolyte was added.

Such a non-aqueous electrolyte secondary battery has a composite electrolyte layer between positive and negative electrodes, and has an electrode group in which the composite electrolyte layer has a density of 1.0 g/cc or more and 2.2 g/cc or less. It is possible to provide a non-aqueous electrolyte secondary battery that can suppress the movement of decomposition products of the organic solvent due to charging and discharging, suppress gas generation, suppress deterioration of the electrode, and have more excellent life characteristics.

It should be noted that although several embodiments of the invention have been described, these embodiments are provided by way of example and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and modifications can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the scope of the invention described in the claims and equivalents thereof.

DESCRIPTION OF SYMBOLS 1, 11... Electrode group 2, 12... Exterior member 3, 14... Negative electrode 3a, 14a... Negative electrode current collector 3b, 14b... Negative electrode active material containing layer 4, 15... Separator 5, 13... Positive electrode , 5a, 13a... positive electrode collector, 5b, 13b... positive electrode active material-containing layer, 6, 16... negative electrode terminal, 7, 17... positive electrode terminal, 8... composite electrolyte layer, 10... non-aqueous electrolyte secondary battery, 20 Battery pack 21 Unit cell 22 Adhesive tape 23 Assembled battery 24 Printed wiring board 25 Thermistor 26 Protective circuit 27 Current-carrying terminal 28 Lead on positive electrode side 29 Positive electrode side Connectors 30 Negative lead 31 Negative connector 32 and 33 Wiring 34a Plus wiring 34b Negative wiring 35 Wiring for voltage detection 36 Protective sheet 37 Storage container , 38... lid, 100... electrode, 200... battery pack, 300... vehicle.

Claims (19)

Lithium composite oxide LiM _x Mn _2-x O ₄ (0<X≦0.5, M is at least one selected from the group consisting of Ni, Cr, Fe, Cu, Co, Mg and Mo) as a positive electrode active material a positive electrode comprising
a negative electrode comprising a negative electrode active material;
a composite electrolyte layer containing at least one of a solid electrolyte and an inorganic compound having alumina between the negative electrode and the positive electrode; a separator;
with
The electrode group, wherein the composite electrolyte layer has a density of 1.0 g/cc or more and 2.2 g/cc or less. Lithium composite oxide LiM as a positive electrode active material _x Mn _2-x O. ₄ (0<X≦0.5, M is at least one selected from the group consisting of Ni, Cr, Fe, Cu, Co, Mg and Mo);
a negative electrode comprising a negative electrode active material;
a composite electrolyte layer containing a solid electrolyte between the negative electrode and the positive electrode; a separator;
with
The electrode group, wherein the composite electrolyte layer has a density of 1.0 g/cc or more and 2.2 g/cc or less. 3. The electrode assembly according to claim 1, wherein said composite electrolyte layer is present between said separator and said positive electrode or said negative electrode. 4. The electrode group according to any one of claims 1 to 3, wherein the composite electrolyte layer has a density of 1.3 g/cc or more and 1.5 g/cc or less. The electrode group according to any one of claims 1 to 4, wherein the composite electrolyte layer has a thickness of 0.1 µm or more and 100 µm or less. The electrode group according to any one of claims 1 to 5 , wherein the composite electrolyte layer has a thickness of 1 µm or more and 20 µm or less. The electrode group according to any one of claims 1 to 6 , wherein the solid electrolyte is particulate and has an average particle size of 0.1 µm or more and 10 µm or less. The electrode group according to any one of claims 1 to 7 , wherein the solid electrolyte has an average particle size of 0.1 µm or more and 5 µm or less. The solid electrolyte is selected from the group consisting of perovskite-type lithium-lanthanum-titanium composite oxides, garnet-type lithium-lanthanum-zirconium-containing oxides, NASICON-type lithium-aluminum-titanium composite oxides and lithium-calcium-zirconium oxides, and inorganic compounds having a LISICON-type structure. 9. The electrode group according to any one of claims 1 to 8 , comprising at least one. 10. The electrode group according to any one of claims 1, 3 to 9, wherein the inorganic compound containing alumina is alumina. 11. The electrode group according to any one of claims 1 to 10 , wherein the positive electrode active material has a discharge potential of 4.5 V or higher on a Li/Li ⁺ basis. 12. The electrode group according to any one of claims 1 to 11 , comprising a titanium composite oxide as the negative electrode active material. 13. The electrode group according to claim 12 , wherein the titanium composite oxide includes at least one selected from the group consisting of lithium titanium oxide, titanium oxide, niobium titanium oxide and lithium sodium niobium titanium oxide. an electrode group according to any one of claims 1 to 13 ;
a non-aqueous electrolyte;
A non-aqueous electrolyte secondary battery. A battery pack comprising the nonaqueous electrolyte secondary battery according to claim 14 . an external terminal for energization;
16. The battery pack of claim 15 , further comprising a protection circuit. 17. The battery pack according to claim 15 , comprising a plurality of said non-aqueous electrolyte secondary batteries, wherein said non-aqueous electrolyte secondary batteries are electrically connected in series, in parallel, or in a combination of series and parallel. A vehicle equipped with the battery pack according to any one of claims 15 to 17 . 19. The vehicle according to claim 18 , wherein said battery pack recovers regenerative energy of power of said vehicle.

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