JP4984402B2 - Nonaqueous electrolyte secondary battery - Google Patents

Description

  The present invention relates to an improvement in the negative electrode of a nonaqueous electrolyte secondary battery, and provides a nonaqueous electrolyte secondary battery having a high electric capacity and excellent charge / discharge cycle characteristics.

  Many researches and developments have been made using metallic lithium capable of realizing a high energy density at a high voltage as a negative electrode of a nonaqueous electrolyte secondary battery. Currently, lithium ion batteries that use graphite-based carbon materials that reversibly occlude and release lithium and have excellent cycle life and safety as negative electrodes have been put into practical use.

  However, a battery using a graphite material as a negative electrode has already been put to practical use in a state close to a theoretical capacity (372 mAh / g) of about 350 mAh / g. In order to realize this, a negative electrode material having a capacity higher than that of graphite is required.

  In view of this, alloy-based negative electrode materials containing elements such as silicon and tin are currently attracting attention. Certain metal elements such as silicon and tin can occlude and release lithium ions electrochemically, and can charge and discharge a very large capacity compared to graphite materials. For example, silicon is known to have a theoretical discharge capacity of 4199 mAh / g, 11 times as high as that of graphite. However, when these alloy materials occlude lithium, they form an alloy such as lithium-silicon and lithium-tin, and change from the original crystal structure, resulting in large expansion. For example, in silicon, when the maximum capacity is charged, the theoretical expansion is 4.1 times. Note that the graphite negative electrode that is widely used now has an expansion of 1.1 times due to the use of an intercalation reaction in which lithium is inserted between graphite layers.

  In the case of an alloy-based negative electrode, due to this large expansion phenomenon, electrical conduction in the negative electrode tends to be poor, and the negative electrode has a large cycle deterioration.

  In Patent Document 1, although expansion occurs, destruction of the alloy material itself does not occur, and this effect makes it easy to ensure the current collecting property of the negative electrode during charge and discharge, and the cycle performance can be greatly improved.

  However, due to the increase in the surface area of the alloy material due to expansion, side reactions between the electrolyte and the alloy material surface increase, and the components generated in the reaction process exist near the alloy surface, hindering the charge / discharge reaction. The problem of increasing the negative electrode impedance and deteriorating the charge / discharge cycle has not been solved.

Moreover, in patent document 2 and patent document 3, although the negative electrode active material is different from the viewpoint of containing an organic acid in the negative electrode body, it is a negative electrode constituent layer containing a carboxylic acid or a salt in a chalcogen compound or oxide. For example, it has been proposed to improve the cycle performance by using a coating solution containing oxalic acid as a negative electrode plate, but there is no description of the mechanism and consideration leading to the improvement of the cycle performance, and technical details are detailed. It is hard to say that the study has been sufficiently conducted.
JP 2004-103340 A JP-A-9-190819 JP-A-9-190820

  As described above, when a high-capacity alloy material is used, a side reaction between the electrolytic solution and the surface of the alloy material increases due to an increase in the surface area of the alloy material due to the expansion of the alloy material during charging. The components generated in the reaction process exist in the vicinity of the alloy surface, which becomes a factor that inhibits the charge / discharge reaction, increases the negative electrode impedance, and deteriorates the charge / discharge cycle.

  In view of these drawbacks, the present invention is a negative electrode using an alloy material capable of electrochemically inserting and extracting Li containing Si as a negative electrode active material, and the negative electrode has one or more double bonds. By containing at least one selected from fatty acids, salts thereof, or anhydrides thereof, the deterioration of the cycle characteristics of the battery as described above is suppressed.

The non-aqueous electrolyte secondary battery in the present invention is a non-aqueous electrolyte secondary battery including a positive electrode capable of reversibly occluding and releasing lithium, a negative electrode, and a non-aqueous electrolyte. and a phase composed mainly of Si, and a B phase comprising an intermetallic compound of a transition metal element and Si, and at least one of the a-phase and B-phase is microcrystalline or amorphous, two more Mixed with an anhydride of a fatty acid having one or more heavy bonds, the fatty acid anhydride is stearic anhydride, oleic anhydride, linoleic anhydride and linolenic anhydride
The content of the fatty acid anhydride with respect to the amount of the negative electrode active material is at least one selected from the group consisting of 0.001 to 20 wt% .

  According to the present invention, in a battery using a conventional alloy material as a negative electrode active material, a non-aqueous electrolyte secondary battery in which deterioration of the cycle characteristics of the battery due to expansion of the negative electrode active material during charging is suppressed is realized.

  The negative electrode for a non-aqueous electrolyte secondary battery in the present invention includes at least an alloy material containing Si capable of electrochemically inserting and extracting Li and graphite, and the alloy material transitions from an A phase mainly composed of at least Si. At least a metal element and a B phase containing a silicide containing Si, and either or both of the A phase and the B phase are low crystalline or amorphous, and one double bond is formed in the negative electrode It contains at least one selected from the above-mentioned fatty acids or their salts or their anhydrides.

  The A phase contained in the alloy material is a phase mainly composed of Si, and particularly preferably a Si single phase. The A phase is a phase that occludes and releases Li, and needs to be a phase that can electrochemically react with Li. In the case of the Si single phase, it is possible to occlude and release Li in a very large amount per weight and per volume. However, since Si itself is a semiconductor, it has poor electron conductivity. In order to improve the problem, a trace amount of additive elements such as P and H, or a transition metal element may be contained up to about 5% by weight.

  The B phase preferably forms a silicide of a transition metal element and Si. By forming a silicide, this has high affinity with the A phase, and cracks at the crystal interface are less likely to occur.

  Further, it has higher electron conductivity and higher hardness than Si alone. Therefore, the B phase also works as a holding phase that compensates for the low electronic conductivity of the A phase and maintains its shape against expansion stress.

A plurality of B phases may exist. For example, two or more phases (for example, MSi ₂ and MSi) having different composition ratios of the transition metal elements M and Si may exist.

Two or more phases may exist due to silicides with different transition metal elements. The transition metal element is preferably at least one selected from Ti, Zr, Ni, Co, Mn, Fe, and Cu. Particularly preferred are Ti and Zr. These elements have higher electronic conductivity and higher strength than silicides of other elements when silicides are formed.

  The abundance ratio of the A phase and the B phase is preferably 10% by weight or more and 95% by weight or less for the A phase. It is particularly preferably 15% by weight or more and 85% by weight or less. If the A phase is less than 10% by weight, the capacity of the alloy material itself decreases. On the other hand, when the amount is more than 95% by weight, the amount of the B phase is overwhelmingly reduced, so that the above-described effect is reduced and the battery characteristics are deteriorated.

  The crystal state of the alloy material used in the present invention is desirably low crystal or amorphous. When a crystalline active material is used, particle cracking is liable to occur with the occlusion of Li, and the current collecting property is rapidly lowered to deteriorate the battery characteristics. Here, the term “low crystal” refers to a case where the crystal grain size calculated by the Scherrer equation is 50 nm or less using the half-width of the peak having the highest intensity from the spectrum obtained when X-ray diffraction measurement is performed. . Amorphous means a state having a spectrum having a broad peak in the range of 2θ = 15 to 40 ° in the X-ray diffraction measurement. By using the amorphous or low crystalline alloy material shown above, particle cracking caused by expansion due to the occlusion of Li hardly occurs.

  The transition element is preferably at least one selected from Ti, Zr, Ni, Co, Mn, Fe, and Cu. More preferred are Ti and Zr.

  The fatty acids and their salts used in the present invention or their anhydrides are characterized by having one or more double bonds. As described above, on the surface of the negative electrode active material containing Si that has expanded during charging, side reactions with the electrolytic solution are likely to occur. However, the presence of fatty acids, their salts, or their anhydrides in the negative electrode By specifically acting on the surface of the negative electrode active material, side reactions with the electrolytic solution are suppressed, and the surface of the negative electrode active material is maintained in a state suitable for charge / discharge. Even when the negative electrode active material expands, it is considered that the negative electrode active material works well following its volume change to some extent.

  Among these, the fatty acid preferably contains at least one selected from the group consisting of oleic acid, linoleic acid and linolenic acid. Both have excellent effects and can be used, but these have a structure in which H in the structure is decreased by 2 and double bonds are increased by one. Particularly preferred is oleic acid. Regarding this, if there are too few double bonds in the material structure, the action on the negative electrode active material will be insufficient, while if there are too many double bonds, It is thought that there is a factor in starting the unstable state in the chemical state.

  The fatty acid salt used in the present invention is at least one selected from a lithium salt or a sodium salt.

  Although the action is the same as described above, in the method for producing a negative electrode, the use of a salt thereof rather than an organic acid may have advantages such as stability in the electrode coating step and can be used.

  The fatty acid anhydride used in the present invention is at least one selected from the group consisting of stearic anhydride, oleic anhydride, linoleic anhydride, and linolenic anhydride. In the case of acid anhydride, in addition to its action, hydrolysis reaction by acid anhydride in the negative electrode active material or the negative electrode is the same as the effect of suppressing side reaction with the electrolyte on the surface of the negative electrode active material. By absorbing unnecessary water in the negative electrode active material, in the negative electrode, or inside the battery, problems such as side reactions with water with the electrolyte can be reduced.

  In particular, stearic anhydride is preferred. This seems to be due to the presence of an appropriate proportion of double bonds in the material structure. If the amount is too small, the action on the negative electrode active material will be insufficient. On the other hand, if there are too many double bonds, an unstable state will begin to occur in the electrolyte or in the electrochemical state of charge / discharge. There seems to be a factor.

  The fatty acid, fatty acid salt and fatty acid anhydride are not limited to a single component, but may be a mixture.

  The content of the fatty acid, fatty acid salt or fatty acid anhydride used in the present invention relative to the negative electrode active material is preferably in the range of 0.001 to 20 wt%, particularly preferably 0.01 to 10 wt%. .

  If the content is too small, the above-described action on the surface of the negative electrode active material is not sufficient, and if it is excessively large, the charge / discharge reaction on the surface of the negative electrode active material is inhibited, resulting in a decrease in capacity.

  The negative electrode includes a binder that holds a graphite material, an alloy material, a conductive agent, and the like in a certain shape. The binder may be any material as long as it is electrochemically inactive with respect to Li in the working potential range of the negative electrode and does not affect other substances. For example, styrene-butylene-copolymer rubber, polyacrylic acid, polyethylene, polyurethane, polymethyl methacrylate, polyvinylidene fluoride, polytetrafluoroethylene, carboxymethylcellulose, methylcellulose and the like are suitable. The greater the amount added, the more likely the electrode structure will be in a strong electrode state, but conversely there is a drawback in that the battery capacity decreases because the material that does not react with Li increases in the negative electrode. A plurality of binders may be used in combination.

  The current collector mainly contains Cu, and the content is preferably 90% by weight or more. Further, in order to improve the strength or flexibility of the current collector, elements such as P, Ag, and Cr may be included.

  Furthermore, the thickness of the current collector is preferably 6 μm or more and 40 μm or less. Current collectors thinner than 6 μm are difficult to handle and many process problems appear. In addition, the strength required for the current collector is difficult to maintain, and the negative electrode is cut off or wrinkled due to expansion / contraction of the active material layer accompanying the charge / discharge reaction, resulting in deterioration of battery characteristics. Conversely, in a current collector thicker than 40 μm, the volume occupied by the current collector in the battery increases and the capacity decreases. In addition, the thick current collector makes it difficult to handle, such as being difficult to bend.

  In addition, the thickness of the negative electrode mixture portion is preferably 10 μm or more and 100 μm or less in the distance from the current collector surface to the mixture surface. When the thickness is less than 10 μm, the volume ratio occupied by the current collector increases, which is not suitable for high capacity. Moreover, when the thickness of the mixture is thicker than 100 μm, the electrolyte solution hardly penetrates to the vicinity of the current collector, and there is a problem in high rate discharge characteristics.

  A lithium secondary battery is manufactured using the negative electrode produced by the above-described method, the positive electrode, and the nonaqueous electrolytic solution. The method for manufacturing the positive electrode may be a general manufacturing method. As a typical example, a positive electrode active material, a conductive agent such as carbon black, and a binder such as polyvinylidene fluoride are mixed in a solvent, and coated, dried and rolled on a positive electrode current collector such as Al. Obtained by.

The positive electrode active material is preferably a lithium-containing transition metal compound that is generally used in lithium secondary batteries, and representative examples thereof include LiCoO ₂ , LiNiO ₂ , LiMn ₂ O ₄ , LiMnO ₂ , and the like. These compounds may be compounds obtained by substituting transition metal elements of these compounds with different metal elements. For example LiCo _1-x Mg x O ₂ as a representative _{example, LiNi 1-y Co y O} 2, LiNi 1-yz Co y Mn z O 2 (x, y, z are all positive numbers), and the like.

As the non-aqueous electrolyte, it is desirable to use an organic solvent generally composed of an organic solvent used in a lithium secondary battery and a lithium salt soluble in the organic solvent. As the organic solvent, a mixed solvent of cyclic carbonates such as ethylene carbonate and propylene carbonate and chain carbonates such as dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate is generally used. Furthermore, γ-butyl lactone, dimethoxyethane or the like may be mixed. Examples of the lithium salt include inorganic lithium fluoride and lithium imide compound. The former includes LiPF ₆ and LiBF ₄ , and the latter includes LiN (CF ₃ SO ₂ ) ₃ . Furthermore, LiClO ₄ or LiCF ₃ SO ₃ may be mixed. Further, a solid electrolyte such as a gel may be used.

  Furthermore, in order to prevent an internal short circuit between the positive electrode and the negative electrode, a separator is installed between them. As the material of the separator, any material can be used as long as it allows a non-aqueous electrolyte to pass through appropriately and the positive electrode and the negative electrode do not contact each other. Generally used is a polymer film such as porous polyethylene or polypropylene, and the thickness is desirably 10 μm or more and 30 μm or less.

  The lithium secondary battery described in the present invention includes a cylindrical shape, a flat shape, a coin shape, a square shape, and the like, but the shape is not particularly limited. Moreover, it does not matter whether the exterior is sealed in a metal can or sealed with a laminate film.

  Hereinafter, preferred embodiments of the present invention will be described. However, the following embodiment is a preferred embodiment of the present invention, and the present invention is not limited to the following embodiment.

  The present invention will be specifically described below based on examples. First, in the following examples, a method for producing a negative electrode, a cylindrical battery used for measurement of cycle life, and a method for measuring discharge capacity and cycle life will be described.

(Production method of negative electrode)
The alloy material as the negative electrode active material was synthesized by the following method. First, the mixing ratio of metal Ti (purity 99.99% made by high purity chemical -20 μm product) and metal Si (purity 99.999% made by Kanto Chemical -20 μm product) is Ti: Si = 9.2: 90.8, respectively. (Weight ratio) Weighed and mixed. At this time, the fatty acids and their salts shown in the present invention or their anhydrides were further mixed in the range of 0.0005 to 30 wt% with respect to the negative electrode active material.

  3.5 kg of this mixture was charged into a vibration mill device (FV-20 manufactured by Chuo Kako Koki Co., Ltd.), and a stainless steel ball (diameter 2 cm) was further charged so as to occupy 70% by volume of the content of the mill device.

Next, after the inside of the container was evacuated, Ar (purity 99.999% Japanese oxygen) was substituted so that the pressure became 1 atm. Under these conditions, a mechanical alloying operation was performed. The conditions were 1300 rpm and 60 hours.

  When the Ti—Si alloy produced by this operation was collected and the particle size distribution was examined, it was found that it had a wide particle size from 0.5 μm to 80 μm.

  Moreover, when it investigated with the Fourier-transform infrared spectrophotometer (FTIR), it confirmed that the input fatty acid, those salts, or those anhydrides contained.

  Moreover, when it investigated by thermogravimetric analysis, it confirmed that it was the same amount as the weight ratio in which the fatty acid, those salts, or those anhydrides were thrown.

  The alloy powder thus obtained was classified with a sieve under 10 μm to obtain an alloy material having a maximum particle size of 8 μm and an average particle size of 5 μm.

When this alloy material was measured by X-ray diffraction, it was a low crystal alloy material, and the crystal grain size was calculated to be 10 nm from the peak intensity and the half-value width of the largest peak based on the Scherrer equation. Further, when the structure is estimated from the result of X-ray diffraction, there is a Si single phase and a phase presumed to be TiSi _2, and it is calculated from the mixture ratio on the assumption that only the two phases exist in this alloy. : TiSi ₂ = 80: 20 (weight ratio). When this alloy material was observed with a transmission electron microscope (TEM), it was found that a Si phase having amorphous or crystals of about 10 nm and a TiSi ₂ phase having crystals of about 15 to 20 nm existed.

  A negative electrode was produced using the alloy material produced above, a graphite material, and a binder. As the graphite material, KS-44 (manufactured by Timcal) is used, and this graphite is flaky graphite having an average particle diameter of 20 μm. Moreover, as a binder, the negative mix paste was obtained by fully kneading | mixing using polyacrylic acid (Molecular weight 150,000 Wako Pure Chemical Industries make). The mixing ratio at this time was alloy material: graphite material: binder = 20: 80: 5. As a mixing method, the Ti—Si alloy and polyacrylic acid were first kneaded at 2.5 g, and then graphite and the remaining polyacrylic acid were added and kneaded.

  This paste was applied to both surfaces of an electrolytic Cu foil (made by Furukawa Circuit Foil) having a thickness of 10 μm, dried and rolled to obtain a negative electrode. The mixture density of the negative electrode was 1.3 to 1.4 g / cc, and the porosity was 40 to 45%.

  As a comparative example of the negative electrode of the present invention, a negative electrode produced only from the above graphite, and the above alloy material and acetylene black (trade name: Denka Black, manufactured by Denki Kagaku Kogyo) as a conductive agent were produced at a mixing ratio of 100: 10 (weight ratio). A negative electrode was used. In both cases, the binder was used by adding 5% by weight of the above polyacrylic acid to 100% by weight of the active material.

(Production method of positive electrode)
First, LiCoO _{2 as} a positive electrode active material was synthesized by mixing Li ₂ CO ₃ and CoCO ₃ at a predetermined molar ratio and heating at 950 ° C. Furthermore, what classified this in the magnitude | size of 45 micrometers or less was used. To 100 g of the positive electrode active material, 5 g of acetylene black as a conductive agent and 4 g of polyvinylidene fluoride as a binder (resin component, used as an N-methyl-2-pyrrolidone solution) are added and mixed thoroughly. A paste was obtained. This paste was applied in an arbitrary amount on an Al core material, dried and rolled to obtain a positive electrode.

(Cylindrical battery manufacturing method)
A cylindrical battery shown in FIG. 1 was produced. The strip-shaped electrode body is provided between the negative electrode plate 12 having the negative electrode lead 15 made of Ni attached by spot welding in the same manner as the positive electrode plate 11 having the positive electrode lead 14 made of Al attached to the end of the electrode body by spot welding. The entire structure is wound in a spiral through a strip-shaped polyethylene separator 13 wider than the plate. Further, polypropylene insulating plates 16 and 17 are arranged on the upper and lower sides of the electrode body, inserted into the battery case 18, and a step is formed on the upper part of the battery case 18. An equal volume mixed solution of ethylene carbonate and diethyl carbonate in which / l lithium hexafluorophosphate was dissolved was injected and sealed with a sealing plate 19 to obtain a battery.

(Measurement method of discharge capacity and cycle life)
The charge / discharge cycle test of the cylindrical battery was performed as follows in a thermostat set at 20 ° C. First, constant current charging of the cylindrical battery is performed at a charging current of 0.2 C (1 C is a one hour rate current) until the battery voltage reaches 4.05 V, then the constant voltage charging is set to 4.05 V, and the current value is It went until it became 0.01C. Thereafter, the cylindrical battery was discharged at a current of 0.2 C until the battery voltage reached 2.5V. The discharge capacity at this time was defined as the initial discharge capacity. From the next time, the charging current was 1 C until the battery voltage reached 4.05 V, and then the constant voltage charging was performed until 4.05 V and the current value reached 0.05 C. Thereafter, the cylindrical battery was discharged at a current of 1 C until the battery voltage reached 2.5V. This charge / discharge cycle was repeated, the ratio of the discharge capacity at the 100th cycle to the discharge capacity at the second cycle was determined, and the value was multiplied by 100 to obtain the capacity retention rate (%). The closer the capacity retention rate is to 100, the better the cycle life.

  First, the type of fatty acid contained in the negative electrode active material was examined.

  Table 1 shows the types of fatty acids examined. That is, oleic acid when the weight ratio with respect to the negative electrode active material is fixed at 1 wt%, and when the weight ratio with respect to the negative electrode active material is fixed at 0.5 wt% in each case of oleic acid, linoleic acid, and linolenic acid The case of + stearic acid, linoleic acid + stearic acid, linolenic acid + stearic acid, oleic acid + stearic acid was examined. Table 1 also shows the results of similar evaluations for the case where no fatty acid was contained.

  It was revealed that the cycle life of the negative electrode in this example was significantly improved as compared with Comparative Example 1 when any fatty acid was contained.

The fatty acids and their salts used in the present invention or their anhydrides are characterized by having one or more double bonds. As described above, on the surface of the negative electrode active material containing Si that has expanded during charging, side reactions with the electrolytic solution are likely to occur. However, the presence of fatty acids, their salts, or their anhydrides in the negative electrode By specifically acting on the surface of the negative electrode active material, side reactions with the electrolytic solution are suppressed, and the surface of the negative electrode active material is maintained in a state suitable for charge / discharge. Even when the negative electrode active material expands, it is considered that the negative electrode active material works well following its volume change to some extent.

  Among them, as the fatty acid, it is preferable to contain at least one selected from the group consisting of oleic acid, linoleic acid and linolenic acid, both of which have excellent effects and can be used. The structure has a structure in which H in the structure decreases by two and double bonds increase by one. Particularly preferred is oleic acid. Regarding this, if there are too few double bonds in the material structure, the action on the negative electrode active material will be insufficient, while if there are too many double bonds, It is thought that there is a factor in starting the unstable state in the chemical state.

  Next, the type of fatty acid salt contained in the negative electrode active material was examined.

  Table 2 shows the types of fatty acid salts examined. That is, the weight ratio to the negative electrode active material is fixed to 1 wt%, and in each case of lithium oleate, lithium linoleate, lithium linolenate, lithium oleate, and sodium oleate, sodium linoleate, Each case of linolenic acid sodium salt and oleic acid sodium salt was examined.

  Moreover, about the case where it does not contain a fatty acid salt, the result of having performed the same evaluation is shown together in Table 2.

  It became clear that the cycle life of the negative electrode in this example was significantly improved as compared with Comparative Example 2 when any fatty acid salt was contained.

  Next, the type of fatty acid anhydride contained in the negative electrode active material was examined.

  Table 3 shows the types of fatty acid salts examined. That is, the weight ratio with respect to the negative electrode active material was fixed to 1 wt%, and each case of stearic anhydride, oleic anhydride, linoleic anhydride, and linolenic anhydride was examined. Moreover, about the case where a fatty acid anhydride is not contained, it shows in Table 3 together with the result of having performed the same evaluation.

  It was revealed that the cycle life of the negative electrode in this example was significantly improved compared to Comparative Example 3 when any of the fatty acid salts was contained.

  Next, it fixed in each case of oleic acid and a stearic anhydride, and examined each content with respect to a negative electrode active material. As shown in Table 4, the examined content range was 0.0005 wt% to 30 wt%.

  As shown in Table 4, the content of the negative electrode active material was found to be in the range of 0.001 wt% to 20 t%, with a high capacity and a high cycle capacity retention rate. Considering that the capacity is sufficiently high, it is particularly preferably 0.01 to 10 wt%. About this, when less than 0.0001 wt%, the effect | action with respect to the negative electrode active material of a fatty acid is inadequate, and it is thought that the effect with respect to cycling characteristics is not enough. Moreover, when more than 20 wt%, it will be in an excessive state and will exist more than necessary on the surface of a negative electrode active material, As a result, charging / discharging reaction will be inhibited and it will be thought that the capacity | capacitance fell.

  Next, the case where the transition element of the alloy material is Ti has been described above, but in this example, each case of Zr, Ni, Co, Mn, Fe, and Cu was examined as shown in Table 5.

  The alloy material was synthesized in the same manner as in the case where the transition metal was Ti. Instead of Ti powder as a raw material, each powder of Zr, Ni, Co, Mn, Fe, Cu (purity 99. 99% high-purity chemical (-20 μm product).

  It was found that the cycle life of the negative electrode in this example was significantly improved when any transition metal element was used.

  The nonaqueous electrolyte secondary battery of the present invention provides an excellent nonaqueous electrolyte secondary battery that achieves both high capacity and good charge / discharge cycle characteristics. The present invention can be applied to all forms of non-aqueous electrolyte secondary batteries. For example, the present invention has not only the cylindrical shape described in the embodiment but also a coin shape, a square shape, a flat shape, and the like, and a wound type. The present invention is also applicable to a battery having an electrode body structure such as a stacked type. The nonaqueous electrolyte secondary battery of the present invention is useful as a main power source for mobile communication devices, portable electronic devices and the like.

The longitudinal cross-sectional view of the cylindrical battery in one Example of this invention

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Positive electrode plate 12 Negative electrode plate 13 Separator 14 Positive electrode lead 15 Negative electrode lead 16 Insulating plate 17 Insulating plate 18 Battery case 19 Sealing plate

Claims (2)

A non-aqueous electrolyte secondary battery including a positive electrode, a negative electrode, and a non-aqueous electrolyte capable of reversibly occluding and releasing lithium, wherein the negative electrode active material is composed of at least two different phases, and the A phase mainly composed of Si and a transition metal element And a B phase composed of an intermetallic compound of Si and Si, and at least one of the A phase and the B phase is microcrystalline or amorphous, and further an anhydride of a fatty acid having one or more double bonds; And the fatty acid anhydride is at least one selected from the group consisting of stearic anhydride, oleic anhydride, linoleic anhydride, and linolenic anhydride, with respect to the amount of the negative electrode active material The content of the fatty acid anhydride is in the range of 0.001 to 20 wt%. The non-aqueous electrolyte secondary battery according to claim 1, wherein the transition metal element is at least one selected from the group consisting of Ti, Zr, Ni, Co, Mn, Fe, and Cu.

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