JPH11214004A - Negative electrode material for nonaqueous electrolyte secondary battery and nonaqueous electrolyte secondary battery equipped with negative electrode using the negative electrode material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nonaqueous electrolyte secondary battery with a high capacity, superior cycle performance, and higher safety performance. SOLUTION: A metal that capable of forming an alloy with lithium, or an alloy, an oxide, or a nitride consisting of two kinds or more elements including a metal that is capable of forming an alloy with lithium forms carbide by means of a reaction with carbon to be in a state of chemically bonding with carbon particles as a negative electrode material for a nonaqueous electrolyte secondary battery a composite material of carbon, metal, an alloy, oxide, or nitride is used. Thereby, a nonaqueous electrolyte secondary battery with a high capacity, a superior cycle characteristic, and higher safety performance is provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-aqueous electrolyte secondary battery.

[0002]

2. Description of the Related Art Non-aqueous electrolyte secondary batteries are small, lightweight, and have a high energy density, and are therefore expected to contribute to portable and cordless equipment used.

Conventionally, the positive electrode active material of a non-aqueous electrolyte secondary battery
Is LiCoO_Two, LiNiO _Two, LiMn
_TwoO_Four, V_TwoO_FiveAre known, while, on the other hand,
As the negative electrode active material, metallic lithium, Li-Al alloy,
Although a Li-Pb alloy was considered, the charge-discharge cycle was repeated.
Then, dendrite-like lithium precipitates and grows,
Finally, through the separator, causing a short circuit between the positive and negative electrodes
And it has not been put to practical use.

[0004] For safety reasons, some carbon materials, such as graphite, capable of inserting and extracting lithium and having excellent cycle characteristics have been put to practical use.

Further, in order to increase the charge / discharge capacity of the carbon material, as disclosed in Japanese Patent Application Laid-Open No. 5-299073, the surface of the high-crystalline carbon particles forming the core is formed by VI.
A carbon composite coated with a film containing a Group II metal element and further coated with carbon, or a carbon composite and a metal capable of being alloyed with lithium as disclosed in JP-A-2-121258. Mixtures are known.

Further, as disclosed in Japanese Patent Application Laid-Open No. 8-273702, a lithium secondary battery having high capacity and excellent charge / discharge cycle characteristics is known by supporting a metal forming an alloy with lithium on carbon particles. Have been.

[0007]

However, Japanese Patent Laid-Open Publication No.
In the technology disclosed in Japanese Patent Application Laid-Open No. 99073 and Japanese Patent Application Laid-Open No. 2-121258, the theoretical capacity of carbon itself was not obtained by coating carbon with metal, and the output density was not sufficient. Japanese Patent Application Laid-Open No. H8-273702 discloses that, by carrying metal fine particles that can be alloyed with lithium on carbon, the capacity is larger than that of graphite and the charge / discharge cycle characteristics are improved. Insufficient capacity and cycle characteristics for automotive batteries
There was also a problem in terms of safety.

[0008]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a metal capable of forming an alloy with lithium or a metal capable of forming an alloy with lithium at a carbon particle interface. An alloy or oxide or nitride composed of two or more types of elements that form a carbide by reacting with carbon and that is in a chemical bond with carbon particles is used as a negative electrode material for a non-aqueous electrolyte secondary battery By using the negative electrode material for a non-aqueous electrolyte secondary battery as a negative electrode, a non-aqueous electrolyte secondary battery having high capacity, excellent cycle characteristics, and high safety is provided.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention can be implemented by adopting the configuration described in each claim. However, in order to make the embodiment easy to understand, the following is a technical feature of the present invention. Explicit background.

[0010] The negative electrode material of the present invention is prepared by using existing carbon particles (X
The plane distance d (002) by the line diffraction method is 3.35 to 4.
1Å) An alloy or an oxide composed of two or more elements including at least one kind of metal capable of forming an alloy with lithium, or at least one kind of metal capable of forming an alloy with lithium, in its own capacity. Increase the capacity by adding the capacity of the material or nitride, and furthermore, carbon particles and metal or alloy or oxide or nitride,
At the interface of the carbon particles, a carbide having a composition of carbon and the metal or alloy or oxide or nitride is formed, and a chemical bond is formed between the carbon particles and the metal or alloy or oxide or nitride. It is a material that shows excellent cycle characteristics. Thus, the feature emphasized in the present invention is that the carbon particles and the metal or the alloy or the oxide or the nitride form carbides and are strongly bonded. As disclosed in Japanese Patent Application Laid-Open No. 8-273702, only metal fine particles capable of being alloyed with lithium are supported on carbon (in the examples of Japanese Patent Application Laid-Open No. 8-273702, only the supported metal is seen by X-ray diffraction. (But not for carbides), the supported metal expands and contracts due to the occlusion and release of lithium, so that the supported metal is more likely to be desorbed from carbon, and floats over the current collector after repeated cycles. In addition, the current collecting property of the metal is deteriorated and inactivated. As a result, the cycle characteristics required for a motorcycle or an electric vehicle cannot be satisfied.

However, the negative electrode material of the present invention does not simply carry carbon particles and a metal or alloy, an oxide or a nitride, but uses a composition of carbon and a metal or an alloy or an oxide or a nitride at the interface of the carbon particles. To form a strong bond between the carbon and the metal or alloy or oxide or nitride by chemical bonding,
By preventing the metal, alloy, oxide or nitride from easily detaching from the carbon particles due to expansion and contraction, a cycle superior to the non-aqueous electrolyte secondary battery disclosed in JP-A-8-273702 is achieved. It shows the characteristics. further,
It is also possible to combine more metals or alloys or oxides or nitrides with carbon.
A considerably higher capacity can be expected than the non-aqueous electrolyte secondary battery disclosed in Japanese Patent No. 3702.

Thus, in the negative electrode material of the present invention, 100
It has excellent cycle characteristics in which the capacity can be maintained at a high capacity even in a cycle of 0 to 2,000 cycles or more.

Further, as disclosed in Japanese Patent Application Laid-Open No. Hei 8-273702, in the case where Ag or Sn is supported on carbon particles, the bond between Ag and Sn and carbon is weak.
As the charge / discharge cycle is repeated, the supported metal detaches from the carbon particles due to expansion and contraction of the supported metal that occludes and releases lithium, and as a result, the current collecting property decreases and the overvoltage increases. Therefore, the charge / discharge cycle is set to 100
When the cycle is repeated for 0 cycles or more, the cycle deterioration becomes remarkable. In the cycle-deteriorated state, the desorbed metals exist in a state where they occlude lithium, and those metals are in a thermally unstable state due to a large specific surface area, which is extremely dangerous from the viewpoint of safety. In state. in this way,
There is also a problem in terms of safety by simply supporting the metal on the carbon particles.

However, in the negative electrode material of the present invention, even if the charge and discharge cycle is repeated, carbon and the metal or alloy or oxide or nitride form carbide at the carbon interface,
Since they are strongly chemically bonded to each other, even if the charge / discharge cycle is repeated, the metal, alloy, oxide, or nitride does not desorb from the carbon particles due to expansion and contraction of itself, and thus, 1000 cycles. Even if the above-mentioned charge / discharge is performed, there is no deterioration of the cycle except for the deterioration factors inherent to the carbon material. Therefore, lithium does not accumulate in a portion distant from the carbon material, and the safety is high.

For the above reasons, by using the negative electrode material of the present invention, a non-aqueous electrolyte secondary battery having high capacity, excellent cycle characteristics, and high safety can be provided.

Hereinafter, the materials used in carrying out the present invention will be described in detail. As the carbon particles, natural graphite, artificial graphite, petroleum, graphitizable carbon obtained from coal pitch or coke, infusibilized carbon, petroleum, coal pitch or coke fired in a temperature range of 650 to 1000 ° C. And non-graphitizable carbon obtained by firing a resin or the like in a temperature range of 600 to 1300 ° C., and the shape thereof may be spherical, massive, scale-like, fibrous, or a crushed product thereof. Among these carbon materials, the plane distance d (002) determined by the X-ray diffraction method as described in claim 2 is 3.35.
To 4.1 °, and the average particle size is preferably 1 to 4.1 °.
It is preferably from 50 μm to 50 μm.

The method for bonding a metal or an alloy to carbon particles includes a vapor deposition method, a sputtering method, a wet reduction method, an electrochemical reduction method, a plating method, a gas phase reduction gas treatment method, a mechanical mixing method, and a high frequency wave. There is a thermal plasma method, etc.
In each method, it is necessary to set conditions so that the carbon particles and the metal or alloy form carbide at the carbon interface.

As the metal capable of forming an alloy with lithium, Al, B
a, B, Ca, Si, Sr, or a metal element selected from the group consisting of Mg, and preferably contains at least one kind of metal capable of forming an alloy with lithium.
In alloys or oxides or nitrides composed of more than one kind of element, it is preferable that at least one kind of transition metal or at least one kind of typical metal is contained, and further, a metal capable of forming an alloy with lithium Or an alloy or oxide or nitride composed of two or more elements containing at least one metal capable of forming an alloy with lithium has an average particle diameter of 0.01.
And preferably 1 to 20% by weight based on carbon particles.

As described above, in a non-aqueous electrolyte secondary battery having a non-aqueous electrolyte, a positive electrode, and a negative electrode capable of inserting and extracting lithium, the constituent materials of the negative electrode include:
By using the negative electrode material having the characteristics described in claim 1, a nonaqueous electrolyte secondary battery having high capacity, excellent cycle characteristics, and high safety can be realized.

The negative electrode active material in the non-aqueous electrolyte secondary battery of the present invention is obtained by adding carbon as a conductive material to the negative electrode material of the present invention.
It is preferable that the positive electrode active material is contained in an amount of 80% by weight. Co, Ni, Mn, Ti, Mo, W, Nb,
It is preferable to use compounds such as composite oxides and composite sulfides of one or more transition metals such as V, Fe, Cr and the like. Particularly with respect to high voltage and high energy density, LiCoO ₂ ,
Positive electrode active materials such as LiNiO ₂ and LiMn ₂ O ₄ are suitable.

Further, as a solvent for the non-aqueous electrolyte,
Lencarbonate (hereinafter referred to as EC), propylene carbonate
-Carbonate (hereinafter referred to as PC), dimethyl carbonate
(Hereinafter referred to as DMC), ethyl methyl carbonate
(Hereinafter referred to as EMC), diethyl carbonate (hereinafter referred to as EMC)
Cyclic, chain carbonates such as
-Γ-lactones such as butyrolactone, 1,2-dimethoate
Xiethane (hereinafter referred to as DME), 1,2-diethoxy
Cietan (hereinafter referred to as DEE), ethoxymethoxye
Chain carbonate ethers such as tan (hereinafter referred to as EME),
Cyclic ethers such as tetrahydrofuran, acetonitrile
Or a solvent selected from nitriles such as
More than one type of mixed solvent is used, especially carbonate-based
Organic solvents are preferred. As the solute of the non-aqueous electrolyte, L
iAsF₆, LiPF₆, LiAlCl_Four, LiClO
_Four, LiCF_ThreeSO_Three, LiSbF₆, LiSCN, L
iCl, LiC₆HSO_Three, Li (CF_ThreeSO_Two)_Two, L
iC (CF_ThreeSO_Two)_Three, C_FourF ₆SO_ThreeLithium such as Li
Salts and mixtures thereof are used.

According to a twelfth aspect of the present invention, the non-aqueous electrolyte secondary battery according to any one of the eighth to eleventh aspects of the present invention is used as a power source of a motor for driving a motorcycle. It specifies an application invention that can be used.

According to a thirteenth aspect of the present invention, the non-aqueous electrolyte secondary battery according to any one of the eighth to eleventh aspects of the present invention is used as a power source of a motor for driving an electric vehicle. It specifies an application invention that can be used.

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in more detail with reference to the drawings, but the present invention is not limited to these embodiments.

(Example 1) As carbon particles, an average particle diameter of 2
0 μm carbon particles shown below were used. The carbon particles were high-purity processed natural graphite. The carbon particles were artificial graphite obtained by heat-treating a carbonized product obtained from petroleum pitch at 2800 ° C. As the carbon particles, petroleum pitch was made infusible, and was made into a graphitizable carbon which was heat-treated at 750 ° C. in an Ar atmosphere and fired at a low temperature. The carbon particles were made of non-graphitizable carbon obtained by heat-treating a phenol resin at 850 ° C. in an Ar atmosphere at low temperature. The carbon particles were made into amorphous carbon (high-temperature sinterable non-graphitizable carbon) which was obtained by subjecting a phenol resin to a crosslinking treatment in air and heat-treating it at 1100 ° C.

A metal chemically bonded to these carbon particles,
As alloys, Al, Ba, B, Ca, Si, Sr, M
g, peritectic alloy of NiSi ₂ and Si, AlSb, CuMg
Sb, SiO, AlN were used, and Ag, S
Loading on carbon was performed using n and Bi.

The method of chemical bonding between the carbon particles and the metal or alloy was performed as follows. In a high-frequency magnetic field of 4 MHz, metal, alloy, oxide, or nitride powder is fed into a high-frequency plasma of argon, vaporized, and the carbon particles or powder having an average particle diameter of 20 μm are dispersed in the region. 5% by weight of ultrafine metal or alloy or oxide or nitride fine particles having an average particle diameter of 0.1 μm are chemically bonded to the carbon particles by controlling the vapor pressure. Al, Ba, B, Ca, Si, Sr, Mg, NiS
peritectic alloy of i ₂ and Si, AlSb, CuMgSb, Si
O and AlN were carried out under the condition of forming a carbide at the carbon interface, and Ag, Sn and Bi were carried out under the condition of simply supporting carbide.

The prepared sample was subjected to X-ray diffraction and XPS
(X-ray Photoelectron Spec
(troscopy).

Al, Ba, B, Ca, Si,
Sr, Mg, peritectic alloy of NiSi ₂ and Si, AlSb,
X-ray diffraction suggests that particles of CuMgSb, SiO, AlN, which are bonded to a metal or alloy or oxide or nitride, are formed by reaction with carbon, each metal or alloy or oxide or nitride, and carbon particles. Al ₄ C _{3 for} Al and Ba for Ba
C _2, the B B ₄ C, the Ca CaC _2, Si in Si
SrC _{2 for} C and Sr, MgC ₂ and NiSi _{2 for} Mg
SiC in peritectic alloy of Si and Si, Al in AlSb
₄ C ₃ , MgC _{2 for} CuMgSb, Si for SiO
In C and AlN, Al ₄ C ₃ was confirmed. Furthermore, XP
The chemical bonding state of the element bonded to the carbon particles was examined by S analysis. As an example, in a sample in which Si having an average particle diameter of 0.1 μm is bonded to carbon particles having an average particle diameter of 20 μm by a thermal plasma method, the binding energy of Si2p is 99.4 eV. Next, about 0.09 μm of Si on the carbon particles was removed by argon sputtering, and the same measurement was performed.
Two lines of 00.4 eV appeared. The value of 99.4 eV reflects the binding energy of Si2p of the Si metal alone, and 1
It is considered that the value of 00.4 eV reflects the binding energy of Si of SiC (Handbook of JEOL).
of X-ray Photoelectron S
Spectroscopy reference). In other words, it is understood that Si forms carbide SiC and bonds at the interface with the carbon particles. Also, other metals, or alloys or oxides or nitrides are measured in the same way,
It was found that each formed a carbide at the interface of the carbon particles similarly to Si, and was in a state of a chemical bond with the carbon particles.

However, with respect to Ag, Sn, and Bi, only one bond energy was observed before argon sputtering (Ag3d5 _{/ 2} : 36).
8.2 eV, Sn3d5 _{/ 2} : 484.87 eV, Bi4
f _7/2 : 157.8 eV) and Ag, Sn, Bi supported on carbon particles are considered to be bonded to the interface with the carbon particles without forming carbides.

As described above, a carbon particle powder in which a metal, an alloy, an oxide, or a nitride is chemically bonded or supported is used as a negative electrode active material.

Next, a cylindrical battery was manufactured using the negative electrode material manufactured as described above, and the battery characteristics were evaluated. FIG.
1 shows a longitudinal sectional view of a cylindrical battery using the negative electrode of the present invention.
In FIG. 1, a positive electrode 1 is LiCoO ₂ as a positive electrode active material.
A mixture of carbon black as a conductive material and an aqueous dispersion of polytetrafluoroethylene as a binder in a weight ratio of 100: 2.5: 7.5 is applied on both sides of an aluminum foil core material. , Dried and rolled, cut into a predetermined size, and spot welded to a positive electrode lead plate 2 made of titanium.

The negative electrode 3 is prepared by adding polyvinylidene fluoride as a binder and a carbon material (acetylene black, artificial graphite, spherical graphite, natural graphite, fibrous graphite, easily graphitized) to the negative electrode active material powder prepared above. And a non-graphitizable carbon can be used at a weight ratio of 75: 20: 5, and a predetermined amount of the mixture is applied to a copper foil core material.
After being dried and rolled, it was cut into a predetermined size, and a copper negative electrode lead plate 4 was formed by spot welding. Reference numeral 5 denotes a separator made of a microporous film made of a polypropylene resin. The positive electrode 1 and the negative electrode 3 are spirally wound through the separator 5 to form an electrode plate group. An upper insulating plate 6 and a lower insulating plate 7 made of a polypropylene resin are respectively disposed above and below the electrode plate group, and inserted into a case 8 plated with nickel on iron, and the positive electrode lead plate 2 is inserted into a titanium sealing plate 9 and the negative electrode After the lead plate 4 was spot-welded to the bottom of the case 8, respectively, an electrolytic solution was injected, and the resultant was sealed via a gasket 10 to produce a battery.

The dimensions of this battery are 17 mm in diameter and 50 in height.
mm. Reference numeral 11 denotes a positive terminal, and the case 8 also serves as the negative terminal.

The electrolyte used was a lithium salt of LiPF ₆ as a solute, 1.5 mol / dm ^3. Was dissolved in a 1: 1 mixed solvent of a high-viscosity organic solvent of EC and a low-viscosity organic solvent of DEC as a solvent.

The negative electrode material of the battery embodying the present invention is composed of Al, Ba, B, Ca, Si, Sr, Mg, NiSi
₂ and Si peritectic alloy, AlSb, CuMgSb, Si
A battery in which O and AlN are chemically bonded is used, and the comparative battery includes the above-described carbon to simple substance, and Ag,
What carried Sn and Bi was used.

For the evaluation of each battery, a constant current charge / discharge cycle test was performed at 0.2 C (1 C charge / discharge corresponds to 780 mAh charge / discharge in one hour). The charge upper limit voltage was 4.2 V, and the discharge lower limit voltage was 3.0 V. Table 1 shows the discharge capacity at the initial stage, after 300 cycles, and after 1000 cycles.

[0038]

[Table 1]

As can be seen from Table 1, the batteries using the negative electrode material according to the embodiment of the present invention have different carbon materials (d (002) =
3.35 to 4.1４), the discharge capacity in the first cycle is higher than that of the comparative battery. That is, in the batteries 1, 2 and 3 according to the present invention, the batteries 10 and 10 according to the present invention were compared with the comparative batteries 4 and 5 and in the batteries 6 and 7 according to the present invention as compared with the comparative batteries 8 and 9. 11,12
In comparison with the comparative batteries 13 and 14, the batteries 15 and 16 embodying the present invention are more than the comparative batteries 17 and 18 and the batteries 19 and 20 embodying the present invention are one more than the comparative batteries 21 and 22.
It can be seen that the discharge capacity at the cycle is high.

Further, comparing the discharge capacity at the 300th cycle, it is found that each battery in which the present invention in which carbon particles are chemically bonded to a metal or alloy or an oxide or a nitride, or which carries them, has a carbon content of only carbon. It shows a larger discharge capacity than the battery (the battery without the metal or alloy to be bonded in Table 1).

At the 1000th cycle, the batteries 1, 2, 3, 6, 7, 10, 11, 11
12, 15, 16, 19, and 20, the high capacity is still maintained and the cycle deterioration is small. This is due to the fact that the negative electrode material of the present invention forms carbide at the interface of carbon particles by the reaction between carbon and metal or alloy or oxide or nitride, and the carbon particles and metal or alloy or oxide or nitride are chemically bonded. By bonding more strongly, the metal or alloy or oxide or nitride due to repeated charge and discharge is prevented from desorbing from the carbon particles due to its own expansion and contraction,
As a result, it is considered that the electrode plate deterioration was suppressed to a small value. However, in the comparative batteries 5, 9, 14, 18, and 22 in which a metal is simply supported on carbon particles, the discharge capacity is smaller than that in the comparative batteries made of only carbon. It is considered that this is because the carried metal separated from the electrode and became inactive due to expansion and contraction of the carried metal due to the charge / discharge cycle. Further, it is considered that during the metal degradation process, the carbon particles of the base material had some adverse effect, and the discharge capacity was smaller than that of the comparative battery made of only the carbon particles.

The judgment on safety was made by charging and discharging the battery using each sample as a negative electrode material for 1000 cycles.
TG of the negative electrode material taken out by disassembling the battery in the charged state
-Perform DTA heat measurement in the temperature range from room temperature to 350 ° C, and determine whether the temperature at which the calorific value reaches the maximum value within that temperature range is higher or lower than that of the negative electrode material consisting of only carbon material. Was judged.

As a result, in the negative electrode material of the present invention, the temperature showing the maximum value of the calorific value was higher than that of the negative electrode material composed of only the carbon material. In the negative electrode material in which a metal was simply supported on carbon particles, the temperature at which the maximum value of the calorific value was lower than that of the negative electrode material composed of only the carbon material.

Thus, it can be seen that the negative electrode material of the present invention is also excellent in safety.

As described above, when the negative electrode material of the present invention is used for a nonaqueous electrolyte secondary battery, a higher capacity is obtained than a secondary battery using a material containing only carbon particles or a material in which a metal is simply supported on carbon particles. Thus, a non-aqueous electrolyte secondary battery exhibiting excellent cycle characteristics and high safety can be provided.

(Example 2) Next, the carbon in Example 1 was sieved to have an average particle diameter of 0.5 to 70 µm, and the carbon having the average particle diameter of 0.
1 μm Si particles were chemically bonded by a thermal plasma method.
At this time, it was confirmed by X-ray diffraction and XPS analysis that SiC was formed at the carbon particle interface. Also, the difference in the average particle size of the carbon particles caused a difference in the amount of Si chemically bonded.
The amount (weight ratio) was determined by chemical analysis. As a comparative example, carbon particles carrying 0 (only carbon) to 50% by weight of Ag having an average particle size of 0.1 μm were used instead of Si.
In the case of carrying Ag, as in Example 1, carbon and Ag
No carbides were found.

Using these samples as a negative electrode active material, a non-aqueous electrolyte secondary battery was produced in the same manner as in Example 1. In the evaluation of the battery, a 0.2 C (1 C charge / discharge corresponds to 780 mAh charge / discharge in 1 hour) constant current charge / discharge cycle test was performed in the same manner as in Example 1. The charge upper limit voltage was 4.2 V, and the discharge lower limit voltage was 3.0 V. As a result, Table 2 shows the discharge capacity at the initial stage, after 300 cycles, and after 1000 cycles.

[0048]

[Table 2]

According to Table 2 (A), the average particle size of carbon is 0.5
It can be seen that the discharge capacity in the first cycle (initial) of the batteries (batteries 23 to 26) in the range of ５０50 μm is high enough to exceed the theoretical capacity of graphite.

Batteries 27 and 28 (each having an average particle size of 7
0,100 μm), the discharge capacity in the first cycle may be lower than that of the battery 35 of the comparative example shown in Table 2 (B), probably because of the small amount of Si.
However, the discharge capacity after 1000 cycles is slightly smaller than that of the battery made only of carbon, as compared with the battery made of only carbon. It is considered that the cause is that a slight amount of Si chemically bonded to carbon has some adverse effect on cycle characteristics. In the case of the battery 23, the amount of Si chemically bonded to the carbon particles was 40% by weight based on the carbon particles.
Therefore, the discharge capacity in the first cycle is 3243 mA
h, but at the 1000th cycle, the discharge capacity was smaller than that of the battery 35 of the comparative example shown in Table 2 (B) manufactured using only carbon. This is because the amount of Si in the entire negative electrode material is too large,
It is considered that the expansion and contraction of the gas increased, and the overvoltage increased. Therefore, the average particle size of the carbon particles is 1 to 50.
It can be seen that the case of μm shows excellent cycle characteristics.

As a comparative example, when the average carbon particle diameter in Table 2 (B) is 1 to 50 μm, the discharge capacity in the first cycle is larger than that of the battery 35 using only carbon, but becomes smaller after 1000 cycles. I will. The cause is that Ag is not strongly bonded to the carbon particles. Therefore, when the charge / discharge cycle is repeated, Ag is separated from the carbon particles by the expansion and contraction of Ag, the Ag particles are inactivated, and the electrode plate is loosened. It is considered that the discharge capacity of carbon itself also decreased.

As for the safety, as in Example 1, a battery using each sample as a negative electrode material was charged and discharged for 1000 cycles, the battery was disassembled in a charged state, and TG-DTA measurement of the negative electrode material was performed. Was carried out in a temperature range from room temperature to 350 ° C., and safety was judged by comparing the temperature showing the maximum value of the calorific value within the temperature range with the temperature shown in the negative electrode material composed only of carbon.

As a result, the average particle size of carbon was 1 to 100.
The temperature at which the maximum value of the calorific value of the negative electrode material of μm (batteries 24 to 28) is higher than that of the negative electrode material of only the carbon material, and the temperature at which the maximum value of the calorific value of the negative electrode material of the battery of the comparative example is only the carbon material Lower than the negative electrode material.

As described above, the carbon particles in the negative electrode material of the present invention have an average particle diameter of 1 to 50 μm, and the weight ratio of the metal or alloy bonded to the carbon particles to the carbon particles is 1
It can be seen that when the content is up to 20% by weight, more excellent characteristics are exhibited with respect to capacity, cycle characteristics and safety.

(Example 3) Next, the average particle size of Example 1
0 μm of carbon having an average particle size of 0.0
05-10 μm Si particles were bonded by a thermal plasma method. At this time, it was confirmed by X-ray diffraction and XPS analysis that SiC was formed at the carbon particle interface. Also,
As a comparative example, the average particle diameter is 0.005 to 1 instead of Si.
What was carried on Ag of 0 μm was used. In Ag, as in Example 1, no carbide was found at the carbon interface.

Using this sample as a negative electrode active material, a non-aqueous electrolyte secondary battery was produced in the same manner as in Example 1. In the evaluation of the battery, a constant current charge / discharge cycle test of 0.2 C (1 C charge / discharge is equivalent to 780 mAh charge / discharge in one hour) was performed in the same manner as in Example 1. The charge upper limit voltage was 4.2 V.
The discharge lower limit voltage was 3.0 V. The result is initial, 300
Table 3 shows the discharge capacity after 1000 cycles.
(A) (for Si) and Table 3 (B) (for Ag as a comparative example).

[0057]

[Table 3]

From Table 3 (A), it is found that S bonded to carbon particles
When the average particle size of i is in the range of 0.005 to 10 μm, the discharge capacity at the first cycle is not larger than that of the battery 35 shown in Table 2 (B).
Carbon (average particle size 20 μm) only (800 mA
h), and when the average particle diameter of Si of the batteries 40 and 41 is in the range of 2 to 10 μm, the discharge capacity at the 1000th cycle is extremely reduced to 500 mAh or less.
This is because when the Si particles become 2 μm or more, carbon particles and Si particles
It is thought that the effect of forming a carbide at the interface with and strongly bonding chemically is weakened, and metals and alloys fall off from the carbon particles due to expansion and contraction, resulting in cycle deterioration.

When Ag was carried on the carbon particles in Table 3 (B), the discharge capacity in the first cycle was as shown in Table 2 (B).
Although the discharge capacity of the battery 35 is equal to or higher than that of the battery 35, the average particle diameter becomes 1000 mAh or less after 1000 cycles. The reason for this is that A
Since g is not strongly bonded to the carbon particles, when the charge and discharge cycle is repeated, Ag separates from the carbon particles due to expansion and contraction of the Ag, inactivates the Ag particles, and discharge capacity of the carbon particles due to electrode plate expansion. It is considered that the discharge capacity after 1000 cycles becomes less than graphite.

Regarding safety, as in Example 1, a battery using each sample as a negative electrode material was charged and discharged for 1000 cycles, the battery was disassembled in a charged state, and TG-DTA measurement of the negative electrode material was performed at room temperature. To 350 ° C., and safety was determined by comparing the temperature showing the maximum value of the calorific value within the temperature range with the temperature shown for the negative electrode material composed only of carbon.

As a result, the average grain size of Si was 0.01 to 1
μm, that is, the temperature at which the maximum value of the calorific value of the negative electrode material of the batteries 37 to 39 was higher than that of the negative electrode material including only the carbon material. However, the temperature showing the maximum value of the calorific value of the negative electrode materials of the batteries 36, 40, 41, and 42 to 47 was lower than that of the negative electrode material including only the carbon material.

The battery 36 has an average Si particle diameter of 0.005.
It is considered that the specific surface area was considerably large due to the small size of μm, and the temperature at which the maximum value of the calorific value was higher than that of the negative electrode material containing only the carbon material.

In the batteries 40 and 41, Si bonded to the carbon particles is large, and when charge and discharge cycles are repeated as seen in the case of metals and alloys of large particles, Si becomes finer, the specific surface area becomes considerably large, and the maximum amount of heat is increased. It is considered that the temperature indicating the value was higher than that of the negative electrode material containing only the carbon material.

In the batteries 42 to 47, the bond between the carbon particles and Ag is weak. Therefore, when charge and discharge are repeated for 1000 cycles, the Ag is desorbed from the carbon particles while remaining bonded to lithium, thereby increasing the specific surface area. It is considered that the temperature at which the maximum value of the calorific value became higher than that of the negative electrode material containing only the carbon material.

As described above, the average particle size of the metal or alloy chemically bonded to the carbon particles in the negative electrode material of the present invention is:
It can be seen that when the thickness is 0.01 to 1 μm, more excellent characteristics are exhibited with respect to capacity, cycle characteristics, and safety.

Example 4 Next, carbon particles obtained by chemically bonding Si particles having an average particle diameter of 0.1 μm to the carbon of Example 1 having an average particle diameter of 20 μm by a thermal plasma method (X-ray diffraction or EP
MA analysis confirmed that SiC was formed at the carbon particle interface) and acetylene black as a conductive material (other carbons shown in Example 1 as a conductive material, all of which can be used) were mixed. A negative electrode plate was manufactured using the obtained material, and a cylindrical battery was manufactured.

For the evaluation of the battery, a constant current charge / discharge cycle test of 0.2 C (1 C charge / discharge corresponds to 780 mAh charge / discharge in 1 hour) was performed in the same manner as in Example 1. The charge upper limit voltage was 4.2 V, and the discharge lower limit voltage was 3.0 V. As a result, Table 4 shows the discharge capacity at the initial stage, after 300 cycles, and after 1000 cycles. Also, as a comparative example, a battery manufactured without a conductive material was evaluated.

[0068]

[Table 4]

From Table 4, the discharge capacity in the first cycle is slightly lower in the batteries 49 to 51 than in the battery 53 of the comparative example due to the mixing of the conductive material. It can be seen that the capacity is higher than that of the battery 53 of the comparative example. This is considered to be due to the fact that when a conductive material is added, the direct resistance component is suppressed to a low level by the improvement in conductivity, and the overvoltage is reduced, thereby improving the maintenance ratio of the discharge capacity.

However, when the amount of the conductive material is small as in the battery 48, the effect cannot be obtained. When the amount of the conductive material is large as in the battery 52, the capacity of the negative electrode material cannot be increased.

Regarding safety, as in Example 1, a battery using each sample as a negative electrode material was charged and discharged for 1000 cycles, the battery was disassembled in a charged state, and TG-DTA measurement of the negative electrode material was performed at room temperature. To 350 ° C., and safety was determined by comparing the temperature showing the maximum value of the calorific value within the temperature range with the temperature shown for the negative electrode material composed only of carbon.

As a result, also in the batteries 48 to 52 and the battery 53 of the comparative example, the temperature at which the maximum value of the calorific value of the negative electrode material was higher than that of the negative electrode material containing only the carbon material.

As described above, when the negative electrode material of the present invention contains carbon as a conductive material in an amount of 5 to 80% by weight, there is no problem in safety at all, and a battery characteristic with further excellent cycle characteristics is obtained although the initial capacity is slightly reduced. We can see that we can do it.

Further, when the negative electrode material of the present invention is used in a non-aqueous electrolyte secondary battery, the positive electrode active material may include Ti, Mn transition metal compounds other than lithium-containing Co, Ni, Mn transition metal compounds.
The same effect can be obtained by using a compound such as a composite oxide or a composite sulfide of one or more transition metals such as o, W, Nb, V, Fe, and Cr. In particular, regarding high voltage and high energy density, LiCoO ₂ , LiNiO ₂ , LiMn ₂ O
A positive electrode active material such as ₄ is suitable.

In Examples 1-4, EC, P were used as the solvent of the electrolyte used for the non-aqueous electrolyte secondary batteries.
Cyclic, chain carbonates such as C, DMC, EMC, and DEC; γ-lactones such as γ-butyrolactone; DM
The EC and DEC of the examples can be obtained by using a solvent selected from chain carbonate ethers such as E, DEE and EME, cyclic ethers such as tetrahydrofuran, nitriles such as acetonitrile, or a mixed solvent of two or more kinds. The same effect as in the case of mixing 1: 1 can be obtained. In particular, it is preferable to use a mixed solvent containing EC as an essential component.

The non-aqueous electrolyte solute is Li
AsF ₆ , LiPF ₆ , LiAlCl ₄ , LiCl
O ₄ , LiCF ₃ SO ₃ , LiSbF ₆ , LiSCN,
LiCl, LiC ₆ HSO ₃ , Li (CF ₃ SO ₂ ) ₂ ,
LiPF such as LiC (CF ₃ SO ₂ ) ₃ , C ₄ F ₆ SO ₃ Li or a mixture thereof may be used to prepare the LiPF.
The same effect as in ₆ is obtained.

Further, as for the shape of the battery, the cylindrical shape is used in this embodiment, but a coin shape, a square shape, or any other shape can be used. And the negative electrode active material of the present invention is also effective as a negative electrode active material of a polymer battery.

The non-aqueous electrolyte secondary battery according to any one of claims 8 to 11 and any of the above battery shapes can be applied to a power source for driving a motor of a motorcycle or an electric vehicle. is there.

[0079]

According to the present invention, as described above, as a negative electrode material of a non-aqueous electrolyte secondary battery capable of inserting and extracting lithium, a metal capable of forming an alloy with lithium or an alloy of lithium at the carbon particle interface is used. An alloy or oxide or nitride composed of two or more elements including a metal capable of forming an alloy forms a carbide by reacting carbon with the metal or alloy or oxide or nitride, and forms carbon and By using a composite carbon material in a chemically bonded state, a nonaqueous electrolyte secondary battery having high capacity, excellent cycle characteristics, and high safety can be realized.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a cylindrical battery using a negative electrode according to one embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Positive electrode 2 Positive electrode lead plate 3 Negative electrode 4 Negative electrode lead plate 5 Separator 6 Upper insulating plate 7 Lower insulating plate 8 Case 9 Sealing plate 10 Gasket 11 Positive electrode terminal

Claims (13)

[Claims] At the interface between carbon particles, an alloy or an oxide or a nitride composed of two or more elements including a metal capable of forming an alloy with lithium or a metal capable of forming an alloy with lithium is formed. A negative electrode material for a non-aqueous electrolyte secondary battery, which forms a carbide by reacting carbon with its metal or alloy and is in a state of being chemically bonded to carbon particles. 2. The method according to claim 1, wherein the carbon particles have a plane distance d determined by X-ray diffraction.
2. The negative electrode material for a non-aqueous electrolyte secondary battery according to claim 1, wherein (002) is 3.35 to 4.1%. 3. The negative electrode material for a non-aqueous electrolyte secondary battery according to claim 1, wherein the carbon particles have an average particle diameter of 1 to 50 μm. 4. The metal according to claim 1, wherein the metal capable of forming an alloy with lithium is a metal selected from the group consisting of Al, Ba, B, Ca, Si, Sr, and Mg. Negative electrode material for non-aqueous electrolyte secondary batteries. 5. An alloy or an oxide or a nitride composed of two or more elements including a metal capable of forming an alloy with lithium contains at least one transition metal or at least one typical metal. The negative electrode material for a non-aqueous electrolyte secondary battery according to claim 1, wherein: 6. An alloy or an oxide or a nitride composed of two or more elements including a metal capable of forming an alloy with lithium, or a metal capable of forming an alloy with lithium, has an average particle size of 0%. 2. The negative electrode material for a non-aqueous electrolyte secondary battery according to claim 1, wherein the thickness is from 0.01 to 1 [mu] m. 7. A weight ratio of carbon to a metal capable of forming an alloy with lithium or an alloy or oxide or nitride of two or more elements including a metal capable of forming an alloy with lithium. Is 1-2
The negative electrode material for a non-aqueous electrolyte secondary battery according to claim 1, wherein the amount is 0% by weight. 8. A non-aqueous electrolyte secondary battery having a non-aqueous electrolyte, a positive electrode, and a negative electrode capable of inserting and extracting lithium, comprising a negative electrode using the negative electrode material according to claim 1. Characteristic non-aqueous electrolyte secondary battery. 9. A non-aqueous electrolyte secondary battery according to claim 8, further comprising a negative electrode comprising the negative electrode material according to claim 1 containing 5 to 80% by weight of carbon as a conductive material. 10. The non-aqueous electrolyte secondary battery according to claim 8, further comprising a positive electrode using a lithium-containing transition metal compound as a positive electrode active material. 11. The non-aqueous electrolyte secondary battery according to claim 8, further comprising a non-aqueous electrolyte in which a lithium salt is dissolved in a carbonate-based organic solvent. 12. The non-aqueous electrolyte secondary battery according to claim 8, wherein the non-aqueous electrolyte secondary battery is used as a power source of a motor for driving a motorcycle. 13. The non-aqueous electrolyte secondary battery according to claim 8, wherein the non-aqueous electrolyte secondary battery is used as a power source of a motor for driving an electric vehicle.