JP2015185491A - Nonaqueous electrolyte secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nonaqueous electrolyte secondary battery which enables the achievement of a high capacity, and in which a silicon oxide (SiOx, where 0.5≤x<1.6) is mixed with graphite material and used as a negative electrode active material.SOLUTION: A nonaqueous electrolyte secondary battery 10 according to one embodiment of the present invention comprises: a positive electrode plate having a positive electrode mixture layer including a positive electrode active material capable of occluding and releasing lithium ions; a negative electrode plate having a negative electrode mixture layer including a negative electrode active material capable of occluding and releasing lithium ions; a separator; and a nonaqueous electrolyte. The negative electrode active material is a mixture of graphite material and a silicon oxide expressed by SiOx(0.5≤x<1.6). The surface of the graphite material is covered with amorphous carbon; the amount of the amorphous carbon covering the graphite material is 0.1-3.0 mass% to that of the graphite material, and the content of the silicon oxide is 1-10 mass% to the total amount of the negative electrode active material.

Description

  The present invention relates to a non-aqueous electrolyte secondary battery that can achieve high capacity, in which silicon oxide (SiOx, 0.5 ≦ x <1.6) is mixed with a graphite material and used as a negative electrode active material.

  Conventionally, graphite materials such as natural graphite and artificial graphite are often used as negative electrode active materials for non-aqueous electrolyte secondary batteries. This is because the graphite material has a charge / discharge potential comparable to that of lithium metal or lithium alloy, but the dendrite does not grow, so the safety is high, the initial efficiency is excellent, and the potential flatness is also good. This is because it has excellent properties such as high density.

However, when a negative electrode active material made of a graphite material is used, lithium can be inserted only up to the composition of LiC ₆ and the theoretical capacity is 372 mAh / g, which is an obstacle to increasing the capacity of the battery. Yes. Therefore, a nonaqueous electrolyte secondary battery using silicon or silicon alloy or silicon oxide alloyed with lithium as a negative electrode active material having high energy density per mass and volume has been developed. In this case, for example, since silicon can insert lithium up to a composition of Li _4.4 Si, the theoretical capacity is 4200 mAh / g, and a capacity larger than that when a carbon material is used as the negative electrode active material can be expected.

  As specific examples thereof, the following Patent Document 1 discloses a material containing silicon and oxygen as constituent elements as a negative electrode active material (provided that the element ratio x of oxygen to silicon is 0.5 ≦ x ≦ 1.5). Hereinafter, this material is referred to as “silicon oxide”) and a non-aqueous electrolyte secondary battery using a material containing a graphite material is disclosed. In this nonaqueous electrolyte secondary battery, a negative electrode active material having a silicon oxide ratio of 3 to 20% by mass is used, where the total of silicon oxide and graphite material is 100% by mass.

  In addition, the use of the graphite material as the negative electrode active material is because the organic solvent is reduced and decomposed on the electrode surface in the initial charging process, and the battery is swollen by the generation of gas, and the negative electrode impedance is increased due to deposition of side reaction products. There is a problem of increasing charging and discharging efficiency, deterioration of charging / discharging cycle characteristics, and the like. Therefore, as shown in Patent Document 2 below, as a negative electrode active material for a non-aqueous electrolyte secondary battery, a material in which the surface of the graphite material is coated with amorphous carbon is used. The surface area is reduced to reduce side reactions at the time of initial charging, thereby suppressing a decrease in initial discharge capacity.

JP 2010-212228 A JP 2001-185147 A

  According to the non-aqueous electrolyte secondary battery disclosed in Patent Document 1, it is possible to suppress deterioration of battery characteristics due to the volume change while using silicon oxide having a high capacity and a large volume change accompanying charge / discharge. Therefore, good battery characteristics can be secured without greatly changing the configuration of the conventional nonaqueous electrolyte secondary battery.

  In addition, when a negative electrode active material for a non-aqueous electrolyte secondary battery as disclosed in Patent Document 2 is a material in which the surface of a graphite material is coated with amorphous carbon, high capacity and good room temperature and low temperature are obtained. Thus, a non-aqueous electrolyte secondary battery having a capacity retention ratio of 1 can be obtained.

  However, as the amount of the amorphous carbon covered on the graphite material increases, the swelling of the battery during charge storage is suppressed, but the capacity of the negative electrode is reduced. For this reason, it is difficult to achieve both a reduction in generated gas due to an increase in the coating amount of amorphous carbon on the graphite material and securing of battery capacity.

According to the nonaqueous electrolyte secondary battery of one embodiment of the present invention,
A positive electrode plate having a positive electrode mixture layer containing a positive electrode active material capable of occluding and releasing lithium ions;
A negative electrode plate having a negative electrode mixture layer containing a negative electrode active material capable of occluding and releasing lithium ions;
A separator, a non-aqueous electrolyte,
With
The negative electrode active material is
It is a mixture of graphite material and silicon oxide represented by SiOx (0.5 ≦ x <1.6),
The surface of the graphite material is coated with amorphous carbon,
The coating amount of the amorphous carbon is 0.1 to 3.0% by mass with respect to the graphite material,
The content of the silicon oxide is 1 to 10% by mass with respect to the total amount of the negative electrode active material,
A non-aqueous electrolyte secondary battery is provided.

  In the nonaqueous electrolyte secondary battery of one embodiment of the present invention, the negative electrode active material contains not only graphite material but also silicon oxide represented by SiOx (0.5 ≦ x <1.6), The surface of the graphite material is covered with 0.1 to 3.0% by mass of amorphous carbon with respect to the graphite material. Silicon oxide as the negative electrode active material has a negative electrode capacity larger than that of the graphite material, but also has a large irreversible capacity, and the negative electrode capacity is lower than the theoretical value during initial charge / discharge.

  When the surface of the graphite material is coated with amorphous carbon, the capacity of the negative electrode is usually reduced. Between graphite material and silicon oxide, silicon oxide reacts preferentially in terms of reaction potential. For this reason, when the graphite material and silicon oxide coexist at the time of initial charge, the graphite material is unlikely to form a film due to the initial reactant. If a film is not formed on the surface of the graphite material, the reaction with the non-aqueous electrolyte proceeds on the surface of the graphite material, which is inherently unstable, leading to a reduction in battery capacity. However, when the surface of the graphite material is coated with amorphous carbon, this amorphous carbon film plays a role as a protective film.

  When silicon oxide and a graphite material with a surface coated with amorphous carbon coexist as a negative electrode active material, the decrease in negative electrode capacity during the initial charge / discharge of silicon oxide was caused by the surface being coated with amorphous carbon. Reduced by graphite material. As a result, according to the nonaqueous electrolyte secondary battery of one embodiment of the present invention, the negative electrode capacity of the entire negative electrode active material is increased as compared with the case where a graphite material whose surface is not coated with amorphous carbon is used. The effect is effective.

  When the coating amount of amorphous carbon is less than 0.1% by mass with respect to the graphite material, the effect of coating the surface of the graphite material with amorphous carbon is not achieved. When the coating amount of amorphous carbon exceeds 3.0% by mass with respect to the graphite material, the capacity decrease due to the surface of the graphite material being coated with amorphous carbon becomes large, and the battery is due to the addition of silicon oxide. Since the capacity increasing effect is exceeded, an increase in the negative electrode capacity of the entire negative electrode active material is not recognized. A more preferable coating amount of amorphous carbon on the graphite material is 0.1 to 0.9% by mass.

  In addition, as for content of a silicon oxide, 1-10 mass% is preferable with respect to the total amount of negative electrode active materials. When the content of silicon oxide is less than 1% by mass with respect to the total amount of the negative electrode active material, the effect of increasing the negative electrode capacity due to the addition of silicon oxide is not achieved. When the content of silicon oxide exceeds 10% by mass with respect to the total amount of the negative electrode active material, the expansion / contraction of the silicon oxide during charging / discharging is large, so that the negative electrode active material is pulverized and missing from the conductive network. Occurs, and the capacity retention rate decreases.

It is a perspective view of the laminate type nonaqueous electrolyte secondary battery common to each experimental example. It is the graph which showed the relationship between the amount of silicon oxide addition, and battery capacity for every coating amount of the amorphous carbon of graphite material.

  Hereinafter, the form for implementing this invention is demonstrated in detail using each experiment example. However, each experimental example shown below is illustrated in order to embody the technical idea of the present invention, and is not intended to limit the present invention to these experimental examples. The present invention can also be applied to various modifications made without departing from the technical idea shown in the claims.

First, the configuration of the nonaqueous electrolyte secondary battery common to each experimental example will be specifically described.
[Production of positive electrode plate]
The positive electrode plate was produced as follows. During the synthesis of cobalt carbonate (CoCO ₃ ), 0.1 mol% of zirconium and 1 mol% of magnesium and aluminum are co-precipitated with respect to cobalt, respectively, and are subjected to a thermal decomposition reaction. Tricobalt oxide was obtained. This was mixed with lithium carbonate (Li ₂ CO ₃ ) as a lithium source and calcined at 850 ° C. for 20 hours to obtain a zirconium / magnesium / aluminum-containing lithium cobalt composite oxide (LiCo _0.979 Zr _0.001 Mg _{0. 01} Al _0.01 O ₂ ) was obtained.

  95 parts by mass of the zirconium-magnesium-aluminum-containing lithium cobalt composite oxide powder synthesized as described above as the positive electrode active material, 2.5 parts by mass of the carbon material powder as the conductive agent, and polyvinylidene fluoride as the binder (PVdF) powder was mixed so that it might become 2.5 mass parts, this was mixed with the N-methylpyrrolidone (NMP) solvent, and the positive mix slurry was prepared. The positive electrode mixture slurry was applied to both surfaces of an aluminum core having a thickness of 15 μm by a doctor blade method. Then, after drying this and removing NMP, it rolled using the compression roller, it cut | judged to predetermined size, and produced the positive electrode plate in which the positive mix layer was formed on both surfaces of the positive electrode core.

[Production of negative electrode plate]
(Preparation of silicon oxide negative electrode active material)
After adjusting the particle size by crushing and classifying silicon oxide having a composition of SiO (corresponding to x = 1 in SiOx), the temperature is raised to about 1000 ° C., and the surface of the particle is made of a carbon material by a CVD method in an argon atmosphere. Covered. At that time, the coating amount of the carbon material was set to 5 mass% of the total amount of silicon oxide including the carbon material. Then, this was crushed and classified to prepare silicon oxide whose surface was coated with a carbon material.

  Artificial graphite was used as the graphite material. The pitch is mixed so that the charging ratio is 0% by mass, 0.1% by mass, 0.3% by mass, 0.9% by mass, 1.5% by mass and 3.0% by mass with respect to the artificial graphite particles. did. Thereafter, these were fired at 900 ° C. to carbonize the pitch, and crushed and classified to obtain a graphite material in which an amorphous carbon film was formed on the surface of the artificial graphite particles.

(Formation of negative electrode mixture layer)
The silicon oxide and graphite material prepared as described above were weighed and mixed so as to have the blending ratios shown in Table 1 below, and used as the negative electrode active material. Subsequently, the negative electrode active material, carboxymethyl cellulose (CMC) as a thickener, and styrene butadiene rubber (SBR) as a binder have a mass ratio of 97.0: 1.5: 1.5. Thus, the mixture was mixed in water to prepare a negative electrode mixture slurry. This negative electrode mixture slurry was applied to both surfaces of a negative electrode core made of a copper foil having a thickness of 8 μm by a doctor blade method. Subsequently, after drying and removing water | moisture content, it rolled to the predetermined thickness using the compression roller, it cut | judged to the predetermined size, and produced the negative electrode plate in which the negative mix layer was formed on both surfaces of the negative electrode core.

[Preparation of non-aqueous electrolyte]
Ethylene carbonate (EC), methyl ethyl carbonate (MEC), and diethyl carbonate (DEC) were mixed at a volume ratio of 30:60:10 at 25 ° C., and then lithium hexafluorophosphate (LIPF ₆ ) Was dissolved to a concentration of 1 mol / L. Furthermore, vinylene carbonate (VC) is added and dissolved so that 2.0 mass% and fluoroethylene carbonate (FEC) are 1.0 mass% with respect to the whole non-aqueous electrolyte, and a non-aqueous electrolyte is prepared. did.

[Production of battery]
The positive electrode plate and the negative electrode plate prepared as described above are wound through a separator made of a polyethylene microporous film, and a cylindrical wound electrode body is produced by attaching a polypropylene tape to the outermost periphery. A flat wound electrode body (not shown) was produced by pressing. Next, the positive electrode current collector tab was attached to the positive electrode plate, and the negative electrode current collector tab was attached to the negative electrode plate by welding.

  Here, the configuration of a laminate type nonaqueous electrolyte secondary battery common to each experimental example will be described with reference to FIG. Prepare a sheet-like aluminum laminate material consisting of a five-layer structure of resin layer (polypropylene) / adhesive layer / aluminum alloy layer / adhesive layer / resin layer (polypropylene) and fold this aluminum laminate material to form the bottom. Then, a laminate outer package 11 having a cup-shaped electrode body storage space was produced. Next, in the glove box under an argon atmosphere, the flat wound electrode body is accommodated in the laminate outer package 11 together with the non-aqueous electrolyte, and the flat wound coil body 12 is welded from the welding sealing portion 12 of the laminate outer package 11. The positive electrode current collecting tab 13 and the negative electrode current collecting tab 14 respectively connected to the positive electrode plate and the negative electrode plate of the rotating electrode body were protruded.

  Thereafter, the laminate exterior body 11 was depressurized to impregnate the separator with a nonaqueous electrolyte, and the opening of the laminate exterior body 11 was sealed with the welded sealing portion 12. In the laminate outer package 11, between the positive electrode current collection tab 13 and the negative electrode current collection tab 14 and the laminate outer package 11, between the positive electrode current collection tab 13 and the negative electrode current collection tab 14 and the laminate outer package 11. In order to improve adhesion and prevent a short circuit between the positive electrode current collector tab 13 and the negative electrode current collector tab 14 and the aluminum alloy layer constituting the laminate outer package 11, a positive electrode current collector tab resin 15 and a negative electrode current collector tab resin 16 respectively. Arranged. The obtained laminate type nonaqueous electrolyte secondary battery 10 common to each experimental example has a height of 62 mm, a width of 35 mm, and a thickness of 3.6 mm (excluding the size of the welded sealing portion 12), and the design capacity is the end of charging. It is 800 mAh at a voltage of 4.4V.

Next, the different configurations of the nonaqueous electrolyte secondary battery of each experimental example will be described.
[Experimental Examples 1-4]
As the nonaqueous electrolyte secondary batteries of Experimental Examples 1 to 4, the negative electrode active material was a graphite material whose surface is not coated with amorphous carbon (covering amount = 0 mass%), and the composition in the negative electrode active material The addition amount of silicon oxide represented by SiO is 0 mass% (Experimental Example 1), 2.5 mass% (Experimental Example 2), 5.0 mass% (Experimental Example 3), and 10 mass% (Experimental Example). What was changed to 4) was used.

[Experimental Examples 5 to 8]
As the non-aqueous electrolyte secondary batteries of Experimental Examples 5 to 8, the negative electrode active material was a graphite material having an amorphous carbon coating amount of 0.1% by mass with respect to the graphite material, and the composition in the negative electrode active material was SiO. The addition amount of silicon oxide represented by 0% by mass (Experimental Example 5), 2.5% by mass (Experimental Example 6), 5.0% by mass (Experimental Example 7) and 10% by mass (Experimental Example 8) What was changed was used.

[Experimental Examples 9 to 12]
As the nonaqueous electrolyte secondary batteries of Experimental Examples 9 to 12, the negative electrode active material was a graphite material having a coating amount of amorphous carbon of 0.3% by mass on the graphite material, and the composition in the negative electrode active material was SiO. The addition amount of silicon oxide represented by the formula is 0 mass% (Experimental Example 9), 2.5 mass% (Experimental Example 10), 5.0 mass% (Experimental Example 11), and 10 mass% (Experimental Example 12). What was changed was used.

[Experimental Examples 13 to 16]
As the non-aqueous electrolyte secondary batteries of Experimental Examples 13 to 16, a graphite material having a coating amount of amorphous carbon of 0.9 mass% on the graphite material was used as the negative electrode active material, and the composition in the negative electrode active material was SiO. The addition amount of silicon oxide represented by the formula is 0 mass% (Experimental Example 13), 2.5 mass% (Experimental Example 14), 5.0 mass% (Experimental Example 15), and 10 mass% (Experimental Example 16). What was changed was used.

[Experimental Examples 17 to 20]
As the non-aqueous electrolyte secondary batteries of Experimental Examples 17 to 20, a graphite material having an amorphous carbon coating amount of 1.5% by mass with respect to the graphite material was used as the negative electrode active material, and the composition in the negative electrode active material was SiO. The addition amount of silicon oxide represented by the formula is 0 mass% (Experimental Example 17), 2.5 mass% (Experimental Example 18), 5.0 mass% (Experimental Example 19), and 10 mass% (Experimental Example 20). What was changed was used.

[Experimental Examples 21 to 24]
As the nonaqueous electrolyte secondary batteries of Experimental Examples 21 to 24, the negative electrode active material was a graphite material having an amorphous carbon coating amount of 3.0% by mass with respect to the graphite material, and represented by SiO in the negative electrode active material. The amount of silicon oxide added is changed to 0% by mass (Experimental example 21), 2.5% by mass (Experimental example 22), 5.0% by mass (Experimental example 23) and 10% by mass (Experimental example 24). What was made to use was used.

[Measurement of capacity at the second cycle]
Each of the nonaqueous electrolyte secondary batteries of Experimental Examples 1 to 24 was charged at 25 ° C. with a constant current of 1 It = 800 mA until the battery voltage became 4.4 V, and then the current was 40 mA at a constant voltage of 4.4 V. Charged until converged. Next, the battery was discharged at a constant current of 1 It = 800 mA until the battery voltage reached 2.5 V, and the current flowing at that time was determined as the discharge capacity of the first cycle. The same charge and discharge was repeated, the discharge capacity at the second cycle was measured, and the discharge capacity at this time was determined as a relative value based on the discharge capacity of Experimental Example 1.

  The measurement results of the battery capacities of Experimental Examples 1 to 24 are summarized in Table 1. Furthermore, the addition amount of silicon oxide in the negative electrode active material was 0% by mass (Experimental Examples 1, 5, 9, 13, 17, and 21) and 2.5% by mass (Experimental Examples 2, 6, 10, 14, 18). And 22), 5.0 mass% (Experimental Examples 3, 7, 11, 15, 19 and 23) and 10.0 mass% (Experimental Examples 4, 8, 12, 16, 20 and 24), A graph in which the horizontal axis represents the content of silicon oxide in the negative electrode active material and the vertical axis represents the battery capacity is shown in FIG.

  From the measurement results of Experimental Examples 1 to 24 shown in Table 1 and the graph of FIG. That is, when the negative electrode active material is made of silicon oxide and a graphite material, when the surface of the graphite material is not coated with amorphous carbon, the battery capacity increases in proportion to the amount of silicon oxide added. When the surface of the graphite material is coated with amorphous carbon, when no silicon oxide is added to the negative electrode active material, the battery capacity decreases as the amount of amorphous carbon covered increases.

  However, even if the surface of the graphite material is coated with amorphous carbon, if silicon oxide is added to the negative electrode active material, the battery capacity increases as the amount of silicon oxide added increases. If the amount of amorphous carbon covering the surface of the graphite material is 0.1 to 3.0% by mass, the amount of silicon oxide in the negative electrode active material is within the range of up to 10% by mass, There is a region where a better battery capacity can be obtained than when no silicon oxide is added to the substance. However, when the addition amount of silicon oxide in the negative electrode active material is 5% by mass or more, the increase in battery capacity tends to be saturated as the addition amount of silicon oxide increases.

  When the amount of amorphous carbon covering the surface of the graphite material is 0.1 to 0.9% by mass, silicon oxide is added to the negative electrode active material in the range of 1 to 10% by mass of silicon oxide. A better battery capacity is obtained than if not. When the amount of amorphous carbon covering the surface of the graphite material is 1.5% by mass, silicon oxide is added to the negative electrode active material when the amount of silicon oxide added is in the range of 1.5 to 10% by mass. Better battery capacity is obtained than without. When the amount of amorphous carbon covering the surface of the graphite material is 3.0% by mass, silicon oxide is added to the negative electrode active material when the amount of silicon oxide added is in the range of 2.5 to 10% by mass or less. Better battery capacity than when not.

  From these facts, the coating amount of amorphous carbon on the graphite material is 0.1 to 3.0% by mass with respect to the graphite material, and the content of silicon oxide in the negative electrode active material is the total amount of the negative electrode active material It can be seen that the content is preferably 1 to 10% by mass. A more preferable coating amount of amorphous carbon on the graphite material is 0.1 to 0.9% by mass with respect to the graphite material.

  In each experimental example, the CMC addition amount and the SBR addition amount in the negative electrode mixture were each 1.5% by mass of the total negative electrode mixture. If it is within the range of%, the same good effect is obtained. Similarly, an example in which the addition amount of VC is 2.0 mass% and the addition amount of FEC is 1.0 mass% with respect to the total amount of the non-electrolytic solution is shown, but the addition amount of VC is 1 to 5 mass%, FEC If the addition amount is in the range of 0.5 to 5% by mass, the same effect is obtained. Furthermore, although the coating amount of the carbon material covering the surface of the silicon oxide whose composition is represented by SiO was shown as 5 mass% of the total amount of silicon oxide including the carbon material, 1 to 5 If it is in the range of mass%, the same advantageous effects are obtained.

Further, in each experimental example, an example in which a zirconium-magnesium-aluminum-containing lithium cobalt composite oxide having a composition of LiCo _0.979 Zr _0.001 Mg _0.01 Al _0.01 O ₂ was used as the positive electrode active material. Indicated. However, in the present invention, not only compounds having different contents of different metal elements such as zirconium, magnesium and aluminum but also compounds capable of reversibly occluding and releasing lithium ions are used. be able to. As a compound capable of reversibly occluding and releasing lithium ions, for example, a lithium transition metal composite oxide represented by LiMO ₂ (where M is at least one of Co, Ni, and Mn) (Ie, LiCoO ₂ , LiNiO ₂ , LiNi _y Co _1-y O ₂ (y = 0.01 to 0.99), LiMnO ₂ , LiCo _x Mn _y Ni _z O ₂ (x + y + z = 1), etc.), LiMn _One kind of ₂ O ₄ , LiFePO ₄ or the like, or a mixture of plural kinds thereof can be used.

  Examples of the nonaqueous solvent in the nonaqueous electrolytic solution that can be used in the nonaqueous electrolyte secondary battery of the present invention include cyclic carbonates such as ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), and fluorine. Cyclic carbonate ester; cyclic carboxylic acid ester such as γ-butyrolactone (γ-BL), γ-valerolactone (γ-VL); dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC) Chain carbonates such as methylpropyl carbonate (MPC) and dibutyl carbonate (DBC); fluorinated chain carbonates; chains such as methyl pivalate, ethyl pivalate, methyl isobutyrate, and methyl propionate Carboxylic acid ester; N, N′-dimethylform Bromide or, N- methyl oxazolidone amide compound, dimethylsulfoxide or the like; may be used tetrafluoroboric acid 1-ethyl-3- ambient temperature molten salt such as methyl imidazolium and the like; sulfur compounds such as sulfolane. Moreover, you may make it use these in mixture of 2 or more types.

As the electrolyte salt dissolved in the non-aqueous solvent in the non-aqueous electrolyte that can be used in the non-aqueous electrolyte secondary battery of the present invention, a lithium salt generally used as an electrolyte salt in the non-aqueous electrolyte secondary battery can be used. . Examples of such lithium salt include lithium hexafluorophosphate (LiPF ₆ ), LiBF ₄ , LiCF ₃ SO ₃ , LiN (CF ₃ SO ₂ ) ₂ , LiN (C ₂ F ₅ SO ₂ ) ₂ , LiN ( _{CF 3 SO 2) (C 4} F 9 SO 2), LiC (CF 3 SO 2) 3, LiC (C 2 F 5 SO 2) 3, LiAsF 6, LiClO 4, Li 2 B 10 Cl 10, Li 2 B ₁₂ Cl ₁₂ or the like can be used singly or as a mixture of a plurality of them. Among these, LiPF ₆ is particularly preferable. The amount of electrolyte salt dissolved in the non-aqueous solvent is preferably 0.8 to 1.5 mol / L.

  In the non-aqueous electrolyte solution of the non-aqueous electrolyte secondary battery of the present invention, for example, vinylene carbonate (VC), vinyl ethylene carbonate (VEC), succinic anhydride (SUCAH), maleic anhydride as an electrode stabilizing compound. Acid (MAAH), glycolic anhydride, ethylene sulfite (ES), divinyl sulfone (VS), vinyl acetate (VA), vinyl pivalate (VP), catechol carbonate, biphenyl (BP), etc. may be added. . Two or more of these compounds may be appropriately mixed and used.

DESCRIPTION OF SYMBOLS 10 ... Laminate type nonaqueous electrolyte secondary battery 11 ... Laminate exterior body 12 ... Welding sealing part 13 ... Positive electrode current collection tab 14 ... Negative electrode current collection tab 15 ... Positive electrode current collection tab resin 16 ... Negative electrode current collection tab resin

Claims (3)

A positive electrode plate having a positive electrode mixture layer containing a positive electrode active material capable of occluding and releasing lithium ions;
A negative electrode plate having a negative electrode mixture layer containing a negative electrode active material capable of occluding and releasing lithium ions;
A separator, a non-aqueous electrolyte,
With
The negative electrode active material is
It is a mixture of graphite material and silicon oxide represented by SiOx (0.5 ≦ x <1.6),
The surface of the graphite material is coated with amorphous carbon,
The coating amount of the amorphous carbon is 0.1 to 3.0% by mass with respect to the graphite material,
The content of the silicon oxide is 1 to 10% by mass with respect to the total amount of the negative electrode active material,
Non-aqueous electrolyte secondary battery.   The non-aqueous electrolyte secondary battery according to claim 1, wherein a coating amount of the amorphous carbon is 0.1 to 0.9 mass% with respect to the graphite material.   The surface of the silicon oxide is coated with a carbon material, and the coating amount of the carbon material is 1 to 5% by mass of the total amount of the silicon oxide including the carbon material. Water electrolyte secondary battery.

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