JP6503768B2 - Lithium ion secondary battery - Google Patents

Description

  The present invention relates to a lithium ion secondary battery.

Conventionally, as the lithium ion secondary batteries, glass ceramics Li as a solid electrolyte that conducts lithium ion _{1 + X Ti 2 Si X P} 3-X O 12 · AlPO 4 ( hereinafter, referred Ohara electrolyte) to the positive or negative electrode What is contained is proposed (for example, refer patent document 1). It is said that this battery can improve the storage stability under high temperature environment and the charge and discharge cycle characteristics. In addition, a solid electrolyte to be mixed in the electrode is Li _0.35 La _0.65 TiO ₃ to improve stability at the time of short circuit of positive and negative electrodes (see, for example, Patent Document 2). Moreover, the thing which added the garnet-type oxide which conducts lithium ion to a positive electrode, and improved cycling characteristics and thermal stability is proposed (for example, refer patent document 3).

JP, 2008-117542, A Japanese Patent Application Laid-Open No. 10-116632 Patent No. 5381640 gazette

  By the way, in a vehicle-mounted power supply or the like, from the viewpoint of starting an engine, for example, a characteristic capable of exhibiting a high output in a short time of about 2 seconds is required. However, in the cases of Patent Documents 1 to 3, for example, the output in a short time of about 2 seconds may be small, and it is desired to further increase the output in a short time of about 2 seconds.

  The present invention has been made to solve such problems, and has as its main object to further increase the output in a short time.

  In order to achieve the above-mentioned purpose, the present inventors have found that the output in a short time of about 2 seconds can be further enhanced if, in addition to the active material, fine garnet-type oxide is included in the negative electrode, The present invention has been completed.

That is, the lithium ion secondary battery of the present invention is
The garnet type oxide having a particle diameter of 3 μm or less and capable of conducting lithium ions, and a negative electrode active material, and the content of the garnet type oxide in the range of 10 mol% to 45 mol% with respect to the negative electrode active material With the negative electrode inside,
Positive electrode,
A non-aqueous electrolyte which is interposed between the negative electrode and the positive electrode and which conducts lithium ions;
Is provided.

  In this lithium ion secondary battery, the output in a short time of about 2 seconds can be further enhanced. The reason why such effects can be obtained is presumed as follows. That is, by arranging an appropriate amount of fine garnet-type oxide in the void in the electrode of the negative electrode, ion conduction at the interface between the non-aqueous electrolyte and the garnet-type oxide can be performed more smoothly, and ions of the non-aqueous electrolyte can be obtained. It is presumed that the conductivity is improved. Furthermore, it is presumed that the ion conductivity is further improved by the lithium ion conduction in the garnet-type oxide.

FIG. 2 is an explanatory view showing an example of the structure of a lithium ion secondary battery 10;

  The lithium ion secondary battery of the present invention comprises a negative electrode, a positive electrode, and a non-aqueous electrolytic solution which is interposed between the negative electrode and the positive electrode and which conducts lithium ions.

  The negative electrode of the lithium ion secondary battery of the present invention contains a garnet-type oxide having a particle diameter of 3 μm or less and capable of conducting lithium ions, and a negative electrode active material, and the content of the garnet-type oxide relative to the negative electrode active material In the range of 10 mol% to 45 mol%. The garnet type oxide capable of conducting lithium ions may have a particle diameter of 3 μm or less, preferably 2 μm or less, and more preferably 1 μm or less. As the particle diameter is smaller, the output for 2 seconds can be improved. Here, the particle diameter is measured using a laser diffraction type particle size distribution measuring apparatus, using ethanol as a dispersion medium, and is calculated as a median diameter D50. The content of the garnet-type oxide capable of conducting lithium ions may be in the range of 10 mol% to 45 mol% with respect to the negative electrode active material, but for example, those in the range of 10 mol% to 25 mol% It may be If the content of the garnet-type oxide is in the range of 10 mol% or more and 45 mol% or less, the 2-second output can be further improved, and a decrease in the discharge capacity or the 10-second output can be further suppressed. The proportion of the negative electrode active material that contributes to charge and discharge can be increased as the content of H is smaller. The output in a short time of about 2 seconds (2 seconds output) is a value obtained as follows. That is, first, after adjusting the lithium ion secondary battery to 50% of the battery capacity (SOC = 50%), the current is flowed at various current values, and the battery voltage after 2 seconds is measured. Then, the supplied current and voltage are linearly complemented, and a current value when the voltage after 2 seconds becomes 3.0 V is obtained. The product of the current and voltage is determined as a 2 second output. Also, the 10-second output is a value obtained as follows. That is, first, after adjusting the lithium ion secondary battery to 50% of the battery capacity (SOC = 50%), current is flowed at various current values, and the battery voltage after 10 seconds is measured. Then, the supplied current and voltage are linearly complemented, and a current value when the voltage after 10 seconds becomes 3.0 V is obtained. The product of the current and voltage is determined as a 10 second output.

The garnet-type oxide capable of conducting lithium ions is not particularly limited, but preferably contains at least Zr, and more preferably further contains at least one of Nb and Ta. More preferably, it contains La in addition to that. This can further enhance the lithium ion conductivity. The garnet-type oxide which conducts this lithium ion has a composition formula Li _{5 + X} La ₃ (Zr _x , A _2-x ) O ₁₂ (wherein, A is Sc, Ti, V, Y, Nb, Hf, Ta And one or more elements selected from the group consisting of Al, Si, Ga and Ge, and X may be represented by 1.4 ≦ X <2). The garnet-type oxide used here has lithium ion conductivity compared to the known garnet-type oxide Li ₇ La ₃ Zr ₂ O ₁₂ (that is, X = 2) because X satisfies 1.4 ≦ X <2. And the activation energy also decreases. For example, when A is Nb, the conductivity is 2.5 × 10 ⁻⁴ Scm ⁻¹ or more, and the activation energy is 0.34 eV or less. Therefore, according to the lithium ion secondary battery containing this oxide, lithium ions are easily conducted, the resistance is lowered, and the output of the battery is improved. In addition, since the activation energy is small, that is, the rate of change of conductivity to temperature is small, the output of the battery is stabilized. In addition, it is more preferable that X satisfies 1.6 ≦ X ≦ 1.95 because the conductivity is higher and the activation energy is lower. Furthermore, if X satisfies 1.65 ≦ X ≦ 1.9, it is more preferable because the conductivity is almost maximum and the activation energy is almost minimum. As A, Nb or Ta having an ion radius equal to that of Nb is preferable.

In the garnet-type oxide capable of conducting lithium ions, the Zr site of the composition formula Li ₇ La ₃ Zr ₂ O ₁₂ is substituted by an element having a different ion radius from Zr, and the intensity of (220) diffraction in XRD is standardized to 1. The intensity after normalization of (024) diffraction may be 9.2 or more. (024) When the intensity after normalization of diffraction exceeds 9.2, the triangle formed by the oxygen ion of the tetrahedron of LiO ₄ (I) approaches an equilateral triangle, and the area of the triangle becomes large. Compared with the garnet-type oxide Li ₇ La ₃ Zr ₂ O ₁₂ (that is, X = 2), the conductivity is higher and the activation energy is also smaller. For example, when A is Nb, the conductivity is 2.5 × 10 ⁻⁴ Scm ⁻¹ or more, and the activation energy is 0.34 eV or less. Therefore, when this oxide is used in a lithium ion secondary battery, lithium ions are easily conducted, and the output of the battery is improved. In addition, since the activation energy is small, that is, the rate of change of conductivity to temperature is small, the output of the battery is stabilized. If the intensity after normalization of (024) diffraction is 10.0 or more, the conductivity is higher and the activation energy is lower, which is more preferable. Furthermore, if the intensity after normalization of (024) diffraction is 10.2 or more, the conductivity is almost maximized and the activation energy is substantially minimized, which is more preferable. As the element having a different ion radius from Zr, one or more elements selected from the group consisting of Sc, Ti, V, Y, Nb, Hf, Ta, Al, Si, Ga and Ge can be mentioned. Among these, Nb and Ta having the same ion radius as Nb are preferable.

  Here, the garnet-type oxide capable of conducting lithium ions only needs to have a garnet-type structure, for example, some of the other structures are included, or the peak position of X-ray diffraction is shifted, for example. It may be a structure including a distorted structure as seen from the garnet. Although shown by the composition formula, the garnet-type oxide capable of conducting lithium ions may partially contain other elements, structures, and the like.

  The negative electrode active material may be any material that can occlude and release lithium ions, and examples thereof include lithium alloys, metal oxides, metal sulfides, and carbonaceous materials that occlude and release lithium. Examples of lithium alloys include alloys of lithium with aluminum, silicon, tin, magnesium, indium, calcium and the like. Examples of the metal oxide include tin oxide, silicon oxide, titanium oxide, lithium titanium oxide, lithium manganese oxide, niobium oxide, tungsten oxide and the like. Examples of the metal sulfide include tin sulfide and titanium sulfide. As a carbonaceous substance which occludes and releases lithium, for example, graphite, coke, mesophase pitch carbon fiber, spherical carbon, resin-calcined carbon and the like can be mentioned. Among them, lithium titanium oxide, lithium manganese oxide, graphite and the like are preferable as the negative electrode active material. The negative electrode active material may be, for example, graphite having a particle diameter of 5.0 μm to 20.0 μm, or an oxide-based negative electrode active material having a particle diameter of 1.0 μm to 25.0 μm. It is also good.

  The negative electrode of the lithium ion secondary battery of the present invention is prepared, for example, by mixing the above-mentioned garnet-type oxide capable of conducting lithium ions, the above-mentioned negative electrode active material, the conductive material and the binder and adding an appropriate solvent The negative electrode material may be applied to the surface of the current collector and dried, and compressed as needed to increase the electrode density. The conductive material is not particularly limited as long as it is an electron conductive material that does not adversely affect the battery performance, and, for example, graphite such as natural graphite (flaky graphite, scaly graphite) or artificial graphite, acetylene black, carbon black, ketjen What mixed 1 type or 2 types or more, such as black, carbon whisker, needle coke, carbon fiber, metals (copper, nickel, aluminum, silver, gold etc.), can be used. Among these, carbon black and acetylene black are preferable as the conductive material from the viewpoint of electron conductivity and coatability. The binder plays a role of holding the active material particles and the conductive material particles, and is, for example, a fluorine-containing resin such as polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), fluororubber, or polypropylene. A thermoplastic resin such as polyethylene, ethylene propylene diene monomer (EPDM) rubber, sulfonated EPDM rubber, natural butyl rubber (NBR) or the like can be used alone or as a mixture of two or more. In addition, an aqueous dispersion of a cellulose based or styrene butadiene rubber (SBR), which is an aqueous binder, can also be used.

  Examples of solvents for dispersing garnet type oxides, negative electrode active materials, conductive materials, and binders include N-methylpyrrolidone, dimethylformamide, dimethylacetamide, methyl ethyl ketone, cyclohexanone, methyl acetate, methyl acrylate, diethylenetriamine, N, N. Organic solvents such as dimethylaminopropylamine, ethylene oxide, tetrahydrofuran etc. can be used. Further, a dispersing agent, a thickener and the like may be added to water, and the active material may be slurried with a latex such as SBR. As the thickener, for example, polysaccharides such as carboxymethylcellulose and methylcellulose can be used alone or as a mixture of two or more. The application method includes, for example, roller coating such as applicator roll, screen coating, doctor blade method, spin coating, bar coater and the like, and any thickness and shape can be made using any of these. In the current collector of the negative electrode, in addition to copper, nickel, stainless steel, titanium, aluminum, calcined carbon, conductive polymer, conductive glass, Al-Cd alloy, etc., adhesion, conductivity and reduction resistance are improved. For the purpose, for example, one obtained by treating the surface of copper or the like with carbon, nickel, titanium, silver or the like can also be used. For these, it is also possible to oxidize the surface. The shape of the current collector may, for example, be a foil, a film, a sheet, a net, a punched or expanded one, a lath body, a porous body, a foam, a formed body of a fiber group, and the like. The thickness of the current collector is, for example, 1 to 500 μm.

The positive electrode of the lithium ion secondary battery of the present invention is, for example, a mixture of a positive electrode active material, a conductive material and a binder, and an appropriate solvent added thereto to form a paste-like positive electrode material on the surface of the current collector. It may be applied and dried, and compressed to increase the electrode density if necessary. As the positive electrode active material, a sulfide containing a transition metal element, an oxide containing lithium and a transition metal element, or the like can be used. Specifically, transition metal sulfides such as TiS ₂ , TiS ₃ , MoS ₃ , FeS ₂ , Li _(1-x) MnO ₂ (0 <x <1, etc., the same applies hereinafter), Li _(1-x) Mn Lithium manganese complex oxide such as ₂ O ₄ , lithium cobalt complex oxide such as Li _(1-x) CoO ₂ , lithium nickel complex oxide such as Li _(1-x) NiO ₂ , lithium such as LiV ₂ O ₃ Vanadium complex oxides, transition metal oxides such as V ₂ O _{5 and the} like can be used. Among these, lithium transition metal complex oxides such as LiCoO ₂ , LiNiO ₂ , LiMnO ₂ , LiV ₂ O _{3 and the} like are preferable. In addition, as the conductive material, the binder, the solvent, and the like used for the positive electrode, those exemplified for the negative electrode can be used. As the current collector, aluminum, titanium, stainless steel, nickel, iron, calcined carbon, conductive polymer, conductive glass, etc., aluminum, copper, etc. for the purpose of improving adhesion, conductivity and oxidation resistance The surface of the above may be treated with carbon, nickel, titanium, silver or the like. For these, it is also possible to oxidize the surface. The shape of the current collector can be the same as that of the negative electrode.

  The non-aqueous electrolyte solution of the lithium ion secondary battery of the present invention may contain a non-aqueous solvent and a support salt. As the non-aqueous solvent, carbonates, esters, ethers, nitriles, furans, sulfolanes and dioxolanes can be mentioned, and these can be used alone or in combination. Specifically, as carbonates, cyclic carbonates such as ethylene carbonate, propylene carbonate, vinylene carbonate, butylene carbonate, chloroethylene carbonate, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, ethyl-n-butyl carbonate, methyl-t -Linear carbonates such as -butyl carbonate, di-i-propyl carbonate, t-butyl-i-propyl carbonate, cyclic esters such as γ-butyl lactone and γ-valerolactone, methyl formate, methyl acetate, ethyl acetate, Chain esters such as methyl butyrate; ethers such as dimethoxyethane, ethoxymethoxyethane and diethoxyethane; nitriles such as acetonitrile and benzonitrile; Examples include furans such as orchid, methyltetrahydrofuran and the like, sulfolanes such as sulfolane and tetramethyl sulfolane, and dioxolanes such as 1,3-dioxolane and methyldioxolane. Among these, a combination of cyclic carbonates and linear carbonates is preferred. According to this combination, not only the cycle characteristics representing the battery characteristics in repetition of charge and discharge are excellent, but also the viscosity of the electrolytic solution, the electric capacity of the obtained battery, the battery output and the like can be balanced. it can.

The supporting salt is, for example, LiPF ₆ , LiBF ₄ , LiAsF ₆ , LiCF ₃ SO ₃ , LiN (CF ₃ SO ₂ ) ₂ , LiC (CF ₃ SO ₂ ) ₃ , LiSbF ₆ , LiSiF ₆ , LiSiF ₆ , LiAlF ₄ , LiSCN, LiClO ₄ LiCl, LiF, LiBr, LiI, LiAlCl _{4 and the} like. Among them, inorganic salts such as LiPF ₆ , LiBF ₄ , LiAsF ₆ and LiClO ₄ , and organic salts such as LiCF ₃ SO ₃ , LiN (CF ₃ SO ₂ ) ₂ and LiC (CF ₃ SO ₂ ) ₃ It is preferred from the viewpoint of the electrical properties to use one or more selected salts in combination. The concentration of the supporting salt in the non-aqueous electrolytic solution is preferably 0.1 mol / L to 5 mol / L, and more preferably 0.5 mol / L to 2 mol / L. When the concentration of the supporting salt is 0.1 mol / L or more, a sufficient current density can be obtained, and when the concentration is 5 mol / L or less, the electrolytic solution can be made more stable. In addition, a phosphorus-based or halogen-based flame retardant may be added to this non-aqueous electrolytic solution.

  The lithium ion secondary battery of the present invention may include a separator between the negative electrode and the positive electrode. The separator is not particularly limited as long as it has a composition that can withstand the use range of the lithium ion secondary battery, but, for example, a polymeric nonwoven fabric such as a polypropylene non-woven fabric or a polyphenylene sulfide non-woven fabric, or an olefin resin such as polyethylene or polypropylene A microporous membrane is mentioned. These may be used alone or in combination of two or more.

  The shape of the lithium ion secondary battery of the present invention is not particularly limited, and examples thereof include coin type, button type, sheet type, laminated type, cylindrical type, flat type, and square type. In addition, a plurality of such lithium ion secondary batteries may be connected in series to apply to a large battery used in an electric car or the like. FIG. 1 is a schematic view showing an example of a lithium ion secondary battery 10 of the present invention. The lithium ion secondary battery 10 includes a positive electrode sheet 13 having a positive electrode mixture 12 formed on a current collector 11, a negative electrode sheet 18 having a negative electrode mixture 17 formed on the surface of a current collector 14, a positive electrode sheet 13 and a negative electrode. A separator 19 provided between the sheet 18 and the non-aqueous electrolytic solution 20 that fills the space between the positive electrode sheet 13 and the negative electrode sheet 18 is provided. In this lithium ion secondary battery 10, the separator 19 is sandwiched between the positive electrode sheet 13 and the negative electrode sheet 18, and these are wound and inserted into the cylindrical case 22, and the positive electrode terminal 24 and the negative electrode sheet connected to the positive electrode sheet 13 And the negative electrode terminal 26 connected to each other. In the lithium ion secondary battery 10, the negative electrode mixture includes the negative electrode active material 17a and the garnet type oxide 17b having a particle diameter of 3 μm or less and capable of conducting lithium ions, and the content of the garnet type oxide 17b is negative. It exists in the range of 10 mol% or more and 45 mol% or less with respect to the active material 17a.

  The lithium ion secondary battery of the present embodiment described in detail above can increase the output for 2 seconds. In addition, it is possible to suppress a decrease in discharge capacity and a decrease in output for 10 seconds. And, for example, such effects can be obtained even in a low temperature range below 0 ° C. The reason why such effects can be obtained is presumed as follows. For example, in addition to the lithium ion transport number of the non-aqueous electrolyte being as low as about 0.3, in the porous electrode, in particular, migration of lithium ions and anions and cations constituting the support salt is inhibited by the electrode composition In some cases, lithium ion conductivity may be low. In particular, at low temperatures such as 0 ° C. or less, the influence of the ion conductivity of the negative electrode on the input / output characteristics becomes extremely large. Therefore, when an appropriate amount of fine garnet-type oxide is disposed in the void in the electrode of the negative electrode, ion conduction is smoothly performed at the interface between the non-aqueous electrolyte and the garnet-type oxide, and the ion conductivity of the non-aqueous electrolyte is increased. It is considered to improve. Furthermore, it is thought that the ion conductivity is further improved by conducting lithium ions in the fine garnet-type oxide.

  In addition, garnet-type oxides that conduct lithium ions have a wide potential window, are stable even at low temperatures and high temperatures, have high lithium ion conductivity, and the garnet-type oxides are present in lithium ion secondary batteries, It is believed that thermal stability can be enhanced and cycle characteristics can be enhanced. For example, since the potential window is wide, it is considered that the battery performance is unlikely to be adversely affected even when exposed to environments such as overcharge and overdischarge. Also, for example, when the garnet-type oxide is contained in the electrode, it is considered that by covering a part of the surface of the active material, it is possible to suppress the side reaction between the non-aqueous electrolyte and the active material. Be In addition, garnet-type oxides have high lithium conductivity, and there are few concerns such as deterioration of output characteristics of the battery. In addition, since it is stable in the atmosphere, it does not easily react with or absorb water in the atmosphere. Moreover, since it has a wide electric potential window of 0V-9.5V, even if it charges / discharges, it can exist stably in a battery. That is, it can be mixed or brought into contact with the low potential negative electrode. In addition, even if the overdischarge occurs and the potential of the negative electrode rises too much, the garnet-type oxide is stable, and thus the electrode is hardly adversely affected.

  It is needless to say that the present invention is not limited to the above-mentioned embodiment at all, and can be implemented in various modes within the technical scope of the present invention.

  Below, the example which produced specifically the lithium ion secondary battery of this invention is demonstrated as an experimental example. Experimental examples 1 to 5 and 12 to 15 correspond to examples of the present invention, and experimental examples 6 to 11 and 16 to 19 correspond to comparative examples. The present invention is not limited to the following examples.

[Experimental Example 1]
(Synthesis of garnet type oxide (solid electrolyte), particle size evaluation)
In order to obtain a cubic garnet-type oxide, Ta-substituted Li _6.75 La ₃ Zr _1.75 Ta _0.25 O ₁₂ was synthesized by the following procedure. Li ₂ CO ₃ , La (OH) ₃ , ZrO ₂ and Ta ₂ O ₅ were used as starting materials. The starting materials were weighed to a stoichiometric ratio and ball milled in ethanol. After drying the mixed powder of the starting material, calcination was carried out in air at 950 ° C. for 10 hours in an alumina crucible. Thereafter, an excess of Li ₂ CO ₃ corresponding to 10 atom% of the Li preparation composition was added to the calcined powder, and the mixed powder was subjected to a ball mill treatment in ethanol. The obtained powder was heated again in air at 950 ° C. for 10 hours, compacted, and fired at 1200 ° C. for 36 hours to produce a solid electrolyte. Thereafter, the synthetic powder was subjected to a ball mill treatment to control the particle size. The particle diameter was measured using ethanol as a dispersant using a laser diffraction particle size distribution analyzer (SALD-2200 manufactured by Shimadzu Corporation), and was calculated as a median diameter.

(Production of the test battery)
Lithium titanium oxide Li _1.33 Ti _1.67 O ₄ (manufactured by Ishihara Sangyo, LT-106, particle diameter 6.9 μm) is used as the negative electrode active material, the mixture ratio is 85% by mass active material, 10% by mass carbon black as conductive material 5% by mass of polyvinylidene fluoride as a binder. By adding 10 mol% of garnet type oxide Li _6.75 La ₃ Zr _1.75 Ta _0.25 O ₁₂ having a particle diameter of 1 μm synthesized by the above method and adding N-methyl-2-pyrrolidone as a dispersing material and dispersing it in a proper amount It was a slurry-like mixture. The slurry-like mixture was uniformly applied to a 10 μm thick copper foil current collector, and dried by heating to prepare a coated sheet. Thereafter, the coated sheet was passed through a roll press to densify it, and cut into a shape of 54 mm wide × 500 mm long to obtain a negative electrode.

Lithium nickel oxide LiNiO ₂ is used as the positive electrode active material, 85 mass% of the active material, 10 mass% of carbon black as the conductive material, 5 mass% of polyvinylidene fluoride as the binder, and N-methyl- An appropriate amount of 2-pyrrolidone was added and dispersed to obtain a slurry-like mixture. The slurry-like mixture was uniformly applied to a 20 μm thick aluminum foil current collector, and dried by heating to prepare a coated sheet. Thereafter, the coated sheet was passed through a roll press to densify it, and cut into a 52 mm wide × 450 mm long shape to obtain a positive electrode.

The positive electrode sheet and the negative electrode sheet described above were wound around a polyethylene separator of 56 mm width and 25 μm thickness to prepare a roll-shaped electrode body. This electrode assembly was inserted into a 18650-type cylindrical case, impregnated with a non-aqueous electrolyte, and then sealed to fabricate a cylindrical lithium ion secondary battery. As the non-aqueous electrolytic solution, one in which LiPF ₆ was dissolved at a concentration of 1 M in a mixed solvent in which ethylene carbonate and diethyl carbonate were mixed at 30:70 volume% was used.

(Battery capacity, output evaluation)
Discharge capacity is evaluated by measuring the chargeable and dischargeable capacity by CCCV4.1V charge (current value 100mA, CV time 2 hours) / CCCV 3.0V discharge (current value 100mA, CV time 2 hours), and then discharging the capacity The current values at time rates of 0.1 C and 2 C were calculated, and the discharge capacity (mAh) at current values of 0.1 C and 2 C was measured at CC 4.1 V charge / CC 3.0 V discharge at an environmental temperature of 20 ° C.

  The input and output were evaluated by adjusting the battery capacity to 50% (SOC = 50%) at 20 ° C and -30 ° C, then applying current at various current values and measuring the battery voltage after 2 seconds and 10 seconds did. The current and voltage are linearly interpolated, and the current value when the voltage after 2 seconds and 10 seconds becomes 3.0 V is determined, and the product of the current and voltage is output for 2 seconds (W), 10 seconds output ( W).

[Experimental Example 2]
The same as Experimental Example 1 except that garnet-type oxide Li _6.75 La ₃ Zr _1.75 Ta _0.25 O ₁₂ having a particle diameter of 1 μm of Experimental Example 1 was added by 45 mol% of the negative electrode active material.

[Experimental Example 3]
The same as Experimental Example 1 except that garnet-type oxide Li _6.75 La ₃ Zr _1.75 Ta _0.25 O ₁₂ having a particle diameter of 1 μm of Experimental Example 1 was added at 23 mol% of the negative electrode active material.

[Experimental Example 4]
The same as Experimental Example 1 except that the grain size of the garnet-type oxide Li _6.75 La ₃ Zr _1.75 Ta _0.25 O ₁₂ of Experimental Example 1 was 3 μm.

[Experimental Example 5]
The same as Experimental Example 2 except that the grain size of the garnet-type oxide Li _6.75 La ₃ Zr _1.75 Ta _0.25 O ₁₂ of Experimental Example 2 is 3 μm.

[Experimental Example 6]
The same as Experimental Example 1 except that the solid electrolyte was not added to the negative electrode of Experimental Example 1.

[Experimental Example 7]
Example 4 is the same as Example 4 except that garnet-type oxide Li _6.75 La ₃ Zr _1.75 Ta _0.25 O ₁₂ having a particle diameter of 3 μm of Example 4 is added to 5 mol% of the negative electrode active material.

[Experimental Example 8]
Example 4 is the same as Example 4 except that 50 mol% of the negative electrode active material of garnet-type oxide Li _6.75 La ₃ Zr _1.75 Ta _0.25 O ₁₂ with a particle diameter of 3 μm of Example 4 is added.

[Experimental Example 9]
Example 8 is the same as Example 7 except that the grain size of the garnet-type oxide Li _6.75 La ₃ Zr _1.75 Ta _0.25 O ₁₂ of Example 7 is 7 μm.

[Experimental Example 10]
Experimental Example 4 except that garnet-type oxide Li _6.75 La ₃ Zr _1.75 Ta _0.25 O ₁₂ of Experimental Example 4 was synthesized as follows to use perovskite-type solid electrolyte Li _0.35 La _0.65 TiO _{3 of} 3 μm Same as 4.

(Synthesis of Perovskite-type Oxide (Solid Electrolyte))
Li ₂ CO ₃ , La ₂ O ₃ and TiO ₂ were weighed, mixed and calcined at 650 ° C. for 2 hours for decarboxylation. The powder obtained was subjected to a ball mill treatment for 6 hours, and baked at 1200 ° C. for 6 hours to obtain Li _0.35 La _0.65 TiO ₃ . Thereafter, the synthetic powder was subjected to a ball mill treatment to control the particle size.

[Experimental Example 11]
Glass ceramics 3 μm in particle diameter Li _{1 + x + y} Al _x Ti _2-x Si _y synthesized as follows in garnet type oxide Li _6.75 La ₃ Zr _1.75 Ta _0.25 O ₁₂ of 3 μm in grain diameter of Experimental example 4 Example 4 is the same as Example 4 except that P ₃ -yO ₁₂ (x = 0.05 to 0.4, y = 0.05 to 0.5).

(Synthesis of lithium ion conductive glass ceramics (solid electrolyte))
H ₃ PO ₄ , Al (PO ₃ ) ₃ , Li ₂ CO ₃ , SiO ₂ and TiO ₂ were used as raw materials. Each constituent element has a composition of P ₂ O ₅ (35 mol%), Al ₂ O ₃ (8 mol%), Li ₂ O (15 mol%), TiO ₂ (37 mol%), SiO ₂ (5 mol%) in terms of oxide The mixture was weighed and uniformly mixed, and then placed in a platinum pot and heat-melted in an electric furnace at 1500 ° C. for 4 hours. Thereafter, a glass melt was dropped into flowing water to prepare a flake-like glass, and this glass was crystallized by heat treatment at 950 ° C. for 12 hours to obtain a target glass ceramic.

[Experimental Results of Experimental Examples 1 to 11]
The experimental results of Experimental Examples 1 to 11 are shown in Table 1. As shown in Table 1, reducing the rate characteristics and the long-term output characteristics by arranging a garnet-type oxide with a particle diameter of 3 μm in the Li _1.33 Ti _1.67 O ₄ negative electrode in a ratio of 10 to 45 mol% of the negative electrode active material. It turned out that it is possible to improve the output for a short time of about 2 seconds. Moreover, it turned out that the output for a short time is further improved by the particle diameter of a solid electrolyte being 1 micrometer or less. On the other hand, in Experiment Example 10 using a perovskite oxide instead of garnet oxide and Experiment Example 11 using a lithium ion conductive glass ceramic, it was found that the output for a short time of about 2 seconds can not be sufficiently improved. . From this, it was found that the solid electrolyte needs to be a garnet-type oxide.

[Experimental Example 12]
The same as Experimental Example 1 except that the following negative electrode using graphite as a negative electrode active material was used in place of the negative electrode of Experimental Example 1.

A garnet type oxide having a particle diameter of 1 μm, using graphite (manufactured by Osaka Gas Chemical Co., Ltd., particle diameter 10 μm) as the negative electrode active material, and having a mixture ratio of 95 mass% active material Li _6.75 La ₃ Zr _1.75 Ta _0.25 O ₁₂ was added at 10 mol% of the negative electrode active material, and an appropriate amount of N-methyl-2-pyrrolidone was added as a dispersing agent and dispersed to obtain a slurry-like mixture. The slurry-like mixture was uniformly applied to a 10 μm thick copper foil current collector, and dried by heating to prepare a coated sheet. Thereafter, the coated sheet was passed through a roll press to densify it, and cut into a shape of 54 mm wide × 500 mm long to obtain a negative electrode.

Experimental Example 13
Example 12 is the same as Example 12 except that garnet-type oxide Li _6.75 La ₃ Zr _1.75 Ta _0.25 O ₁₂ having a particle diameter of 1 μm of Example 12 is added by 45 mol% of the negative electrode active material.

[Experimental Example 14]
Example 12 is the same as Example 12 except that the grain size of the garnet-type oxide Li _6.75 La ₃ Zr _1.75 Ta _0.25 O ₁₂ in Example 12 is 3 μm.

[Experimental Example 15]
Example 13 is the same as Example 13 except that the grain size of the garnet-type oxide Li _6.75 La ₃ Zr _1.75 Ta _0.25 O ₁₂ of Example 13 is 3 μm.

[Experimental Example 16]
Example 12 is the same as Example 12 except that the solid electrolyte was not added to the negative electrode of Example 12.

[Experimental Example 17]
Example 14 is the same as Example 14 except that garnet-type oxide Li _6.75 La ₃ Zr _1.75 Ta _0.25 O ₁₂ having a particle diameter of 3 μm of Experimental Example 14 is added at 5 mol% of the negative electrode active material.

[Experimental Example 18]
Example 14 is the same as Example 14 except that 50 mol% of the negative electrode active material of garnet-type oxide Li _6.75 La ₃ Zr _1.75 Ta _0.25 O ₁₂ having a particle diameter of 3 μm of Example 14 is added.

Experimental Example 19
Example 18 is the same as Example 17 except that the grain size of the garnet-type oxide Li _6.75 La ₃ Zr _1.75 Ta _0.25 O ₁₂ of Example 17 is 7 μm.

[Experimental Results of Experimental Examples 12 to 19]
The experimental results of Experimental Examples 12 to 19 are shown in Table 2. As shown in Table 2, in the case of not only Li _1.33 Ti _1.67 O ₄ but also graphite as the negative electrode active material, the garnet-type oxide is added to the electrode without lowering the rate characteristics and the long-term output characteristics. It turned out that it is possible to improve the output for a short time. As mentioned above, it turned out that the kind of negative electrode active material is not specifically limited.

  The invention is applicable to the field of battery industry.

  DESCRIPTION OF SYMBOLS 10 lithium ion secondary battery, 11, 14, current collector, 12 positive electrode composite material, 13 positive electrode sheet, 17 negative electrode composite material, 17a negative electrode active material, 17b garnet type oxide, 18 negative electrode sheet, 19 separator, 20 non-aqueous Electrolyte, 22 cylindrical case, 24 positive terminal, 26 negative terminal.

Claims (1)

Particle size of 1 [mu] m or less lithium ions can conduction composition formula _{Li 5 + X La 3 (Zr} X, A 2-X) O 12 ( wherein, A represents Sc, Ti, V, Y, Nb, Hf, Garnet-type oxides represented by one or more elements selected from the group consisting of Ta, Al, Si, Ga and Ge, X is 1.4 ≦ X <2) , Li _1.33 Ti _1.67 O ₄ and graphite A negative electrode active material which is at least one of the above, and a negative electrode whose content of the garnet-type oxide is in the range of 10 mol% to 45 mol% with respect to the negative electrode active material,
Positive electrode,
A non-aqueous electrolyte which is interposed between the negative electrode and the positive electrode and which conducts lithium ions;
Lithium-ion rechargeable battery equipped with

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