JP2008300179A - Nonaqueous secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a nonaqueous secondary battery restoring a negative electrode material deteriorated by repeating charge/discharge and realizing high charge/discharge characteristics. <P>SOLUTION: The nonaqueous secondary battery is equipped with a positive electrode containing a positive active material capable of absorbing and releasing lithium; a negative electrode containing a negative active material capable of alloying with lithium or absorbing and releasing lithium; and a nonaqueous electrolyte containing an electrolyte ionizing lithium ions and a nonaqueous solvent. A metal complex is contained in the nonaqueous electrolyte, a metal complex in the negative electrode, metallic fine particles of the metal complex in the positive electrode, and deposition potential of ionic species eluted from the metallic fine particles or ionized from the metal complex is nobler than 0.3 V vs. Li/Li<SP>+</SP>. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an additive for a lithium secondary battery and a lithium secondary battery.

  In recent years, lithium secondary batteries that use a non-aqueous electrolyte and charge and discharge by moving lithium ions between a positive electrode and a negative electrode have been used as one of new secondary batteries with high output and high energy density. .

  As such a negative electrode for a lithium secondary battery, a lithium transition metal oxide or a material alloyed with lithium is used as a negative electrode active material. For example, lithium vanadium oxide, silicon, tin, and the like are being studied. However, in these materials, the volume of the active material expands and contracts when lithium is occluded / released. Therefore, the active material is pulverized or the active material is detached from the current collector with charge / discharge. For this reason, there existed a problem that the current collection property in an electrode fell and charging / discharging cycling characteristics worsened.

  In response to these problems, thin film formation such as sputtering, chemical vapor deposition (CVD), and vapor deposition is used as an electrode for a lithium secondary battery that uses silicon as an active material and exhibits good charge / discharge cycle characteristics. An electrode in which a silicon thin film is formed on a current collector by a method has been proposed (Patent Document 1). Further, an electrode for a lithium secondary battery in which another element such as cobalt is added to silicon has been proposed (Patent Document 2).

  On the other hand, in a lithium secondary battery using a carbon material or metallic lithium as a negative electrode active material, it has been proposed to dissolve phosphazene in a non-aqueous electrolyte (for example, Patent Document 3).

The lithium secondary battery using the above electrode is a battery having a very large charge / discharge capacity, but the active material isolated from the isolated active material or the current collecting material due to the pulverization of the active material generated by repeated charge / discharge. It is not possible to maintain or restore the electrical conductivity from. Therefore, the cycle characteristics may be insufficient as compared with a graphite (Graphite) negative electrode having a small volume change due to charge and discharge.
International Publication No. 01/29913 Pamphlet International Publication No. 02/071512 Pamphlet JP 2006-185829 A

  The present invention has been made in view of the above circumstances, and can repair a negative electrode material that deteriorates by repeated charge and discharge during a charge and discharge cycle, and can realize high charge and discharge characteristics. The purpose is to provide.

  The non-aqueous secondary battery of the present invention includes a positive electrode including a positive electrode active material capable of occluding and releasing lithium, a negative electrode including a negative electrode active material capable of alloying with or absorbing lithium, and lithium, and lithium. In a non-aqueous secondary battery comprising an electrolyte that ionizes ions and a non-aqueous electrolyte solution containing a non-aqueous solvent, the non-aqueous electrolyte solution has a metal complex compound and ionized ions from the metal complex compound The deposition potential is nobler than 0.3 V on the basis of a lithium reference electrode.

  The non-aqueous secondary battery of the present invention includes a positive electrode including a positive electrode active material capable of occluding and releasing lithium, and a negative electrode including a negative electrode active material capable of being alloyed with lithium and occluding and releasing lithium. In a non-aqueous secondary battery comprising an electrolyte that ionizes lithium ions and a non-aqueous electrolyte solution containing a non-aqueous solvent, the negative electrode has a metal complex compound and is ionized from the metal complex compound. It is characterized in that the potential is nobler than 0.3 V on the basis of the lithium reference electrode.

  In the nonaqueous secondary battery of the present invention, the metal element contained in the metal complex compound contains Al, Si, Sc, Ti, V, Co, Ni, Cu, Zn, Zr, Nb, Ag, In, It is preferably any of Sn, W, Ga, Pd, Pt or Au.

  The non-aqueous secondary battery of the present invention includes a positive electrode including a positive electrode active material capable of occluding and releasing lithium, and a negative electrode including a negative electrode active material capable of being alloyed with lithium and occluding and releasing lithium. In a non-aqueous secondary battery comprising a non-aqueous electrolyte containing an electrolyte that ionizes lithium ions and a non-aqueous solvent, the positive electrode has metal fine particles or a metal complex compound and is eluted from the metal, or metal The deposition potential of the ion species ionized from the complex compound is characterized by being nobler than 0.3 V on the basis of the lithium reference electrode.

  In the nonaqueous secondary battery of the present invention, the metal element contained in the metal fine particles or the metal complex compound contains Al, Si, Sc, Ti, V, Co, Ni, Cu, Zn, Zr, Nb, Ag, In, Sn, W, Ga, Pd, Pt or Au is preferable.

  Moreover, in the lithium secondary battery of this invention, it is preferable that the said negative electrode active material contains a lithium vanadium oxide.

  According to the lithium secondary battery, a positive electrode including a positive electrode active material capable of occluding and releasing lithium, a negative electrode including a negative electrode active material capable of alloying with or absorbing lithium, and non- A metal electrolyte compound is added to the positive electrode, a metal complex compound is added to the negative electrode, or a metal complex compound is added to the electrolytic solution. The deposition potential of metal ions eluted from the metal fine particles or ionized from the metal complex compound is nobler than 0.3 V on the basis of the lithium reference electrode. Therefore, according to the lithium secondary battery of the present invention, it is possible to provide a lithium secondary battery having excellent cycle characteristics by imparting electronic conductivity between cracks of the negative electrode active material during charging and suppressing capacity deterioration.

Embodiments of the present invention will be described below.
The lithium secondary battery of the present invention comprises a positive electrode, a negative electrode, and a nonaqueous electrolyte.
In the lithium secondary battery of the present invention, metal fine particles or a metal complex compound thereof are added to the positive electrode in advance, or a metal complex compound is added to the non-aqueous electrolyte or the negative electrode. When the metal fine particles are added to the positive electrode, when the positive electrode potential reaches the metal dissolution potential, it is ionized and eluted into the electrolytic solution. When added as a metal complex compound to the positive electrode, negative electrode or non-aqueous electrolyte, it is electrostatically ionized in the electrolyte and dissolved as metal ions. These metal ions are electrodeposited on the negative electrode during the initial charge. The amount of electrodeposition is controlled by the first and second charging conditions and the amount added.

When metal fine particles are added to the positive electrode, it undergoes electrochemical oxidation during the first charge and is eluted into the electrolyte as metal ions. In the case where the additive is a metal complex compound, the electrolyte is poured into the battery and then electrostatically ionized and dissolved in the electrolyte. When these metal ions migrate and diffuse to the vicinity of the negative electrode, and the potential of the negative electrode active material reaches the reduction potential (precipitation potential) of each metal ion, the metal ions near the negative electrode are sequentially subjected to an electrochemical reduction reaction. Deposited (electrodeposited) on the negative electrode.
At this time, the negative electrode active material undergoes an insertion reaction of lithium ions. However, the negative electrode active material starts to crack due to volume expansion from the surface where lithium is occluded. Also in this charging process, when the negative electrode potential reaches the metal deposition potential, the metal ions are electrodeposited on the negative electrode active material by an electrochemical reduction reaction and coated. The volume shrinks due to the lithium ion desorption reaction during discharge, and the crack expands. However, the next charge causes the above electrodeposition, and the crack is also electrodeposited.

When a metal complex compound is added to the negative electrode, the electrolytic solution is poured into the battery, and then electrostatically ionized and dissolved in the electrolytic solution. When these metal ions are dissolved in and near the negative electrode and the potential of the negative electrode active material reaches the reduction potential (precipitation potential) of each metal ion, the negative electrode is sequentially subjected to an electrochemical reduction reaction from the metal ions close to the negative electrode. Precipitated (electrodeposited).
When a metal complex compound is added to the electrolytic solution, it is already electrostatically ionized and dissolved in the electrolytic solution, and these metal ions are adsorbed at the negative electrode / electrolytic solution interface or dissolved in the vicinity of the negative electrode. When the potential of the negative electrode active material reaches the reduction potential (deposition potential) of each metal ion, the metal ions close to the negative electrode are sequentially deposited (deposited) on the negative electrode by an electrochemical reduction reaction.

During the above charging, the negative electrode active material undergoes an insertion reaction of lithium ions. However, the negative electrode active material starts to crack due to volume expansion from the surface where lithium is occluded. Also in this charging process, when the negative electrode potential reaches the metal deposition potential, the metal ions are electrodeposited on the negative electrode active material by an electrochemical reduction reaction and coated. The volume shrinks due to the lithium ion desorption reaction during discharge, and the crack expands. However, the next charge causes the above electrodeposition, and the crack is also electrodeposited.
Hereinafter, the positive electrode, the negative electrode, and the nonaqueous electrolyte constituting the lithium secondary battery of the present invention will be sequentially described.

(Positive electrode)
In the lithium secondary battery of the present invention, as a positive electrode, a positive electrode mixture containing a positive electrode active material capable of occluding and releasing lithium, a conductive additive, and a binder, and a positive electrode joined to the positive electrode mixture A sheet-like electrode made of a current collector can be used. Further, as the positive electrode, a pellet type or sheet-shaped positive electrode formed by forming the above positive electrode mixture into a disk shape can also be used.
In addition, the positive electrode mixture may contain metal fine particles or metal complex compounds described later.

Examples of the positive electrode active material include Li-containing compounds, oxides, and sulfides, and examples of the contained metal include substances containing at least one or more of Mn, Co, Ni, Fe, Al, and the like. it can. More specifically, LiMn ₂ O ₄ , LiCoO ₂ , LiNiO ₂ , LiFeO ₂ , LiNi _1/3 Co _1/3 Mn _1/3 O ₂ , LiNi _0.8 Co _0.2 O _{2 and the} like can be exemplified.
Examples of the binder include polyvinylidene fluoride and polytetrafluoroethylene.
Furthermore, examples of the conductive aid include carbonized materials such as carbon black, ketjen black, and graphite. Furthermore, examples of the positive electrode current collector include a metal foil or a metal net made of aluminum, stainless steel, or the like.

  The addition rate in the case of adding metal fine particles or metal complex compounds to the positive electrode has a range of 0.0001% by mass to 0.1% by mass with respect to the weight of the positive electrode mixture regardless of the metal fine particles or metal complex compounds. The range of 0.001% by mass or more and 0.05% by mass or less is more preferable. The metal fine particle diameter is preferably 1 μm or less at D50, and more preferably 0.1 μm or less in consideration of the short circuit between the electrodes during electrode fabrication, elution efficiency, and the cathode porosity after elution. If the addition rate is 0.001% by mass or more, a sufficient electrodeposition coating is formed.

(Negative electrode)
Next, as the negative electrode, a negative electrode mixture containing a negative electrode active material capable of being alloyed with lithium or occluding and releasing lithium, a binder, and optionally a conductive additive, and the negative electrode mixture A sheet-like electrode comprising a negative electrode current collector bonded to the electrode can be used. Further, as the negative electrode, a pellet-type or sheet-like electrode obtained by forming the negative electrode mixture into a disk shape can also be used.

The binder for the negative electrode may be either organic or inorganic, and may be any material as long as it is dispersed or dissolved in a solvent together with the negative electrode active material and further binds the negative electrode active material by removing the solvent. . Alternatively, the negative electrode active material may be bound by mixing with the negative electrode active material and performing solidification molding such as pressure molding. As such a binder, for example, vinyl resin, cellulose resin, phenol resin, thermoplastic resin, thermosetting resin and the like can be used, such as polyvinylidene fluoride, polyvinyl alcohol, carboxymethyl cellulose, styrene butadiene rubber, etc. Resins can be exemplified.
In addition to the negative electrode active material and the binder, carbon black, graphite powder, carbon fiber, metal powder, metal fiber, or the like may be added as a conductive additive. Furthermore, examples of the negative electrode current collector include a metal foil or a metal net made of copper.

Examples of the negative electrode active material include a metal substance that can be alloyed with lithium and a lithium-containing V compound, V oxide, and V sulfide that can occlude and release lithium. Examples thereof include substances containing at least one kind such as Mg, Ti, Al, Zr, and the like. More specifically, Li _1.1 V _0.9 O ₂ can be exemplified. Examples of metals that can be alloyed with lithium include Si, Al, Sn, Pb, Zn, Bi, In, Mg, Ga, and Cd. A metal lithium foil can also be used as the negative electrode active material. Examples of the carbonaceous material to be compounded with the metallic material include artificial graphite, natural graphite, graphitized carbon fiber, graphitized mesocarbon microbeads, and amorphous carbon.
When the metal complex compound is added to the negative electrode, the addition ratio is preferably in the range of 0.0001% by mass to 0.1% by mass with respect to the negative electrode mixture weight, and is 0.001% by mass to 0.05% by mass. The range of is more preferable. The crystal powder particle size of the metal complex compound is preferably 1 μm or less at D50, and is 0.1 μm or less in consideration of the solubility and elution efficiency after pouring the electrolyte into the battery and the negative electrode porosity after elution. More preferred. If the addition rate is 0.001% by mass or more, a sufficient electrodeposition coating is formed.

(Nonaqueous electrolyte)
Examples of the non-aqueous electrolyte include a non-aqueous electrolyte in which a lithium salt is dissolved in an aprotic solvent. Moreover, the metal complex compound mentioned later may be added to the nonaqueous electrolyte.

The aprotic solvent is generally used alone or in combination with a cyclic carbonate, but when mixed, the following combination examples can be given.
Ethylene carbonate and dimethyl carbonate, ethylene carbonate and methyl ethyl carbonate, ethylene carbonate and diethyl carbonate, propylene carbonate and dimethyl carbonate, propylene Carbonate and methyl ethyl carbonate, propylene carbonate and diethyl carbonate, ethylene carbonate, propylene carbonate and dimethyl carbonate, ethylene carbonate, Propylene carbonate and methyl ethyl carbonate, ethylene carbonate and propylene carbonate and diethyl carbonate, ethylene carbonate, dimethyl carbonate and methyl ethyl carbonate, Ethylene carbonate and dimethyl carbonate and diethyl carbonate, ethylene carbonate and methyl ethyl carbonate And diethyl carbonate, ethylene carbonate, dimethyl carbonate, methyl ethyl carbonate and diethyl carbonate, ethylene carbonate, propylene carbonate and dimethyl carbonate Methyl ethyl carbonate, ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethylene carbonate, propylene carbonate, methyl ethyl carbonate Diethyl carbonate, ethylene carbonate, propylene carbonate, dimethyl carbonate, methyl ethyl carbonate, and diethyl carbonate.
The mixing ratio of the cyclic carbonate and the chain carbonate (cyclic carbonate: chain carbonate) is preferably expressed by weight ratio, preferably 1:99 to 99: 1, More preferably, it is 5: 95-70: 30, More preferably, it is 10: 90-60: 40. This mixing ratio is appropriately determined with good electrical conductivity of the nonaqueous electrolyte that does not impair the charge / discharge characteristics of the lithium secondary battery.

On the other hand, lithium salt includes LiPF ₆ , LiBF ₄ , LiClO ₄ , LiAsF ₆ , Li ₂ SiF ₆ , LiOSO ₂ C _k F _{(2k + 1)} (k = 1 to 8), LiPF _n {C _k F _{(2k + 1)} )} _(6-n) (wherein n is an integer of 1 to 5, k is an integer of 1 to 8). Moreover, the lithium salt shown by the following general formula can also be used. LiC (SO ₂ R ₅ ) (SO ₂ R ₆ ) (SO ₂ R ₇ ), LiN (SO ₂ OR ₈ ) (SO ₂ OR ₉ ), LiN (SO ₂ R ₁₀ ) (SO ₂ OR ₁₁ ), LiN ( _{SO 2 R 12) (SO 2} R 13). Here, R _{5 to} R ₁₃ may be the same as or different from each other, and are a C 1-8 perfluoroalkyl group. These lithium salts may be used alone or in combination of two or more.
Moreover, you may add the additives (vinylene carbonate, fluoroethylene carbonate, etc.) applied with a prior art.

  In addition, as a non-aqueous electrolyte, a polymer such as PEO or PVA mixed with any of the lithium salts described above, a highly swellable polymer impregnated with the above aprotic solvent or lithium salt, or the like A so-called polymer electrolyte can also be used.

  When the metal complex compound is added to the nonaqueous electrolyte, the addition ratio is preferably in the range of 0.01% by mass to 1% by mass, more preferably in the range of 0.05% by mass to 1% by mass, A range of from mass% to 0.5 mass% is more preferable. When the addition rate is 0.05% by mass or more, a sufficient electrodeposition coating can be formed.

  Furthermore, the lithium secondary battery of the present invention is not limited to the positive electrode, the negative electrode, and the non-aqueous electrolyte, and may include other members as necessary. For example, the lithium secondary battery includes a separator that separates the positive electrode and the negative electrode. Also good. The separator is essential when the non-aqueous electrolyte is not a polymer electrolyte, and a known separator such as a porous polypropylene film or a porous polyethylene film can be appropriately used.

Next, the additive added to a positive electrode, a negative electrode, and a nonaqueous electrolyte is demonstrated.
The fine particles and complex compounds according to the present invention are made of a metal having a deposition potential of the eluted or ionized metal ion species that is nobler than 0.3 V on the basis of the lithium reference electrode.

As the metal element constituting the metal fine particles and the metal complex compound, a deposit having high electron conductivity is preferable from the viewpoint of high current collection efficiency between cracks, and the same metal as the main constituent element of the negative electrode active material Is preferable from the viewpoint of high adhesion to the active material. Examples include Al, Si, Sc, Ti, V, Co, Ni, Cu, Zn, Zr, Nb, Ag, In, Sn, W, Ga, Pd, Pt, and Au.
As for defining the dimensional specification of the metal fine particles, the metal fine particle diameter is preferably 1 μm or less at D50, and 0.1 μm or less is taken into account when short-circuiting between electrodes and elution efficiency at the time of battery production, and the positive electrode porosity after elution are taken into account. More preferred. If the addition rate is 0.001% by mass or more, a sufficient electrodeposition coating is formed.

The metal complex compound may be a salt of an organic acid or an inorganic acid of the metal element, and the metal ion may be a constituent element of a cation molecule or an anion molecule. For example, AgBF ₄ , AgPF ₆ , NiPF ₆ , Cu (BF ₄ ) ₂ , Ga (ClO ₄ ) ₃ , Li ₂ TiF ₆ , organic acid —PF _n {C _k F _{(2k + 1)} } _(6-n) (n = 1 to 5 integer, k = 1 to 8 _{integer), - C (SO 2 R} 5) (SO 2 R 6) (SO 2 R 7), - n (SO 2 OR 8) (SO 2 OR ₉ ), —N (SO ₂ R ₁₀ ) (SO ₂ OR ₁₁ ), and —N (SO ₂ R ₁₂ ) (SO ₂ R ₁₃ ) are included. Here, R _{5 to} R ₁₃ may be the same as or different from each other, and are a C 1-8 perfluoroalkyl group. These salts may be used alone or in combination of two or more.

  The deposition pattern of the metal film formed by the conductive film forming compound is basically controlled by the current applied at the battery voltage corresponding to the deposition potential of each metal, the voltage holding conditions, the temperature, and the addition amount. it can. Further, in order to control dendritic precipitation, it is more preferable to use a boron compound or a fluorinated ester in combination.

  In addition, when the formed conductive film functions as an active material such as an alloy with lithium, if a compound that forms a film at a potential lower than the potential at which the conductive film is formed is added at the same time, the decomposition of the nonaqueous electrolyte is simultaneously performed. Can be suppressed. For example, a conventional SEI forming additive such as vinylene carbonate may be added to the non-aqueous electrolyte. The SEI formation additive may be added to the positive electrode and the negative electrode in advance.

In order to add the conductive film forming compound to the positive electrode, for example, a slurry containing a positive electrode active material, a conductive additive, a binder, and a film forming compound is prepared in advance, and this slurry is applied onto a current collector. The conductive film forming compound may be added to the positive electrode by removing the solvent in the slurry by heating.
In this method, when the solvent in the slurry is removed by heating, heating is performed at about 40 ° C to 120 ° C, preferably 80 ° C to 120 ° C, more preferably 100 ° C to 120 ° C.

In addition, in order to add the film-forming compound to the non-aqueous electrolyte, the film-forming compound may be added to the non-aqueous electrolyte in advance, and this may be injected into the battery. The non-aqueous electrolyte and the film-forming compound may be separately added. It may be added to the battery.
The conductive film-forming compound added in this way is electrodeposited when energized in the initial charging step after battery assembly, and forms a conductive film on the negative electrode. At the time of initial charging, charging may be performed while heating to about 0 ° C to 80 ° C, preferably 10 ° C to 60 ° C, more preferably 14 ° C to 38 ° C. By charging while heating, the formation of the conductive film can be promoted.
Thus, a film is formed mainly by the second charge.

  As described above, according to the lithium secondary battery of the present embodiment, the conductivity is a metal fine particle or complex compound in which the precipitation potential of the eluted or ionized ion species is nobler than 0.3 V on the basis of the lithium reference electrode. Since film formation is added and a conductive film is formed on the negative electrode by this film-forming compound, to realize a lithium secondary battery using a high-capacity negative electrode active material such as lithium vanadium oxide, silicon, or tin Can do.

Example 1
An N-methyl-2-pyrrolidone solution in which polyvinylidene fluoride as a binder (# 1100 manufactured by Kureha Chemical Industry Co., Ltd.) was dissolved was prepared. In this solution, 95 parts by mass of LiCoO ₂ and 2 parts by mass of conductive carbon were prepared. And was slurried. The prepared positive electrode slurry was uniformly applied on an Al foil having a thickness of 20 μm and dried to obtain a positive electrode. The ratio of LiCoO ₂ : conductive carbon: polyvinylidene fluoride: Ni fine particles in the positive electrode was 95: 2: 3.
Next, a mixture of lithium vanadium oxide (LVO) powder and carbon material powder is used as the negative electrode active material, 90 parts by weight of the mixed powder of this LVO powder and carbon material powder, and polyvinylidene fluoride (PVDF) 10 serving as a binder. Part by weight was mixed and dispersed in N-methyl-2-pyrrolidone to obtain a negative electrode slurry. And this negative electrode slurry was uniformly apply | coated on the 20-micrometer-thick copper foil, it dried, and it was set as the negative electrode.

A 2032 μm polypropylene separator was interposed between the positive electrode and the negative electrode, and a nonaqueous electrolyte was injected to prepare a 2032 type coin-type lithium secondary battery.
As the non-aqueous electrolyte, a non-aqueous electrolyte solution in which LiPF ₆ was dissolved at a concentration of 1.50 mol / L in a mixed solvent in which ethylene carbonate and diethyl carbonate were mixed at a ratio of 3: 7 was used. .
In addition, silver hexafluorophosphate (AgPF ₆ ) was added to the non-aqueous electrolyte at a ratio of 0.1% by mass with respect to the non-aqueous electrolyte.

  About the lithium secondary battery of Example 1, after charging in an environment of 28 ° C. up to 3.8 V at a constant current and constant voltage (0.1 C) as a conductive film forming step, 3.0 V at a constant current (0.1 C). Discharged until. Next, to confirm the effect, after charging to 4.35V with constant current and constant voltage (0.1C), discharging to 3.0V with constant current (0.1C) was repeated, and the transition of discharge capacity was measured. did. FIG. 1 shows the results of charging and discharging from 4.35 V to 3.0 V after the conductive film forming step.

(Example 2)
Implementation was performed in the same manner as in Example 1 except that silver tetrafluoroborate (AgBF ₄ ) was added to the nonaqueous electrolyte (nonaqueous electrolyte) at a ratio of 0.1% by mass with respect to the nonaqueous electrolyte. The lithium secondary battery of Example 2 was manufactured.
The lithium secondary battery of Example 2 was evaluated in the same manner as in Example 1. The results are shown in FIG.

(Example 3)
The same as Example 1 except that copper tetrafluoroborate (Cu (BF ₄ ) ₂ ) was added to the nonaqueous electrolyte (nonaqueous electrolyte) at a ratio of 0.1 mass% with respect to the nonaqueous electrolyte. Thus, a lithium secondary battery of Example 2 was produced.
The lithium secondary battery of Example 3 was evaluated in the same manner as in Example 1. The results are shown in FIG.

Example 4
Similarly to Example 1, an N-methyl-2-pyrrolidone solution in which polyvinylidene fluoride (# 1100 manufactured by Kureha Chemical Industry Co., Ltd.) as a binder was dissolved was prepared, and 95 parts by mass of LiCoO ₂ was added to this solution. Then, 2 parts by mass of conductive carbon and 0.03 parts by mass of Ni fine particles (particle diameter D50, 0.4 μm) were added to form a slurry. The prepared positive electrode slurry was uniformly applied on an Al foil having a thickness of 20 μm and dried to obtain a positive electrode. The ratio of LiCoO ₂ : conductive carbon: polyvinylidene fluoride: Ni fine particles in the positive electrode was 95.00: 2.00: 2.99: 0.01.

A 2032 μm polypropylene separator was interposed between the positive electrode and the negative electrode, and a nonaqueous electrolyte was injected to prepare a 2032 type coin-type lithium secondary battery.
As the non-aqueous electrolyte, LiPF ₆ is dissolved in a mixed solvent obtained by mixing ethylene carbonate (EC) and diethyl carbonate (DEC) at a ratio of 3: 7 at a concentration of 1.50 mol / L. A water electrolyte was used.
The lithium secondary battery of Example 4 was manufactured using the same negative electrode as in Example 1 above. The lithium secondary battery of Example 4 was evaluated in the same manner as in Example 1. The results are shown in FIG.

(Example 5)
A positive electrode was prepared in the same manner as in Example 4 except that nickel tetrafluoroborate (Ni (BF ₄ ) ₂ , crystal particle diameter of 1 μm or less) was added to the slurry in the process of preparing the positive electrode mixture slurry. . The ratio of LiCoO ₂ : conductive carbon: polyvinylidene fluoride: Ni (BF ₄ ) _{2 in} the positive electrode was 95.00: 2.00: 2.97: 0.03. The lithium secondary battery of Example 5 was manufactured using the same negative electrode and electrolytic solution as in Example 4 above. The lithium secondary battery of Example 5 was evaluated in the same manner as in Example 1. The results are shown in FIG.

(Example 6)
A negative electrode was produced in the same manner as in Example 1 except that AgBF ₄ (crystal particle diameter: 1 μm or less) was added to the slurry in the process of producing the negative electrode mixture slurry. The ratio of negative electrode active material: polyvinylidene fluoride: AgPF ₆ in the negative electrode was 90.00: 9.95: 0.05. The lithium secondary battery of Example 6 was manufactured using the same positive electrode and electrolytic solution as in Example 4 above. The lithium secondary battery of Example 6 was evaluated in the same manner as in Example 1. The results are shown in FIG.

(Comparative Example 1)
A lithium secondary battery of Comparative Example 1 was produced in the same manner as in Example 1 except that the conductive film forming agent was not added to the nonaqueous electrolytic solution.
The lithium secondary battery of Comparative Example 1 was evaluated in the same manner as in Example 1. The results are shown in FIG.

  As shown in FIG. 1, it can be seen that the capacity retention of the lithium secondary batteries of Examples 1 to 6 is smaller than the initial charge / discharge cycle in comparison with Comparative Example 1, and is excellent in cycle stability. . Such a result is obtained because the conductive film forming compound according to the present invention is added to the nonaqueous electrolytes of Examples 1 to 6, and thus the conductivity between the negative electrode active material particles by the film forming compound is ensured and active. This is probably because the utilization rate of the substance was kept high.

  As described above, according to the present embodiment, by generating a metal plating film or a conductive compound during charging, the surface of the negative electrode active material or the crack wall generated in the process of pulverization is covered, or the crack is filled and isolated. Thus, it is possible to secure the capacity without lowering the utilization rate of the active material by giving the electron conductivity between the active materials, and it is possible to provide a non-aqueous secondary battery having stable charge / discharge cycle characteristics.

  In this embodiment, a non-aqueous secondary battery in which any one of a positive electrode, a negative electrode, and a non-aqueous electrolyte is mixed with a metal complex compound or metal fine particles is manufactured, and the effect of the present invention is verified. However, the present invention is naturally not limited to this, and a metal complex compound or metal fine particles may be mixed simultaneously in two or three elements of the positive electrode, the negative electrode, and the nonaqueous electrolytic solution. Moreover, you may mix a metal complex compound and metal microparticles | fine-particles simultaneously with a positive electrode.

It is a figure which shows the cycling characteristics of the non-aqueous secondary battery of this embodiment.

Claims (6)

A positive electrode containing a positive electrode active material capable of inserting and extracting lithium;
A negative electrode containing a negative electrode active material capable of alloying with lithium, or occluding and releasing lithium; and
In a non-aqueous secondary battery comprising a non-aqueous electrolyte containing an electrolyte that ionizes lithium ions and a non-aqueous solvent,
A non-aqueous secondary battery comprising a metal complex compound in the non-aqueous electrolyte, and a deposition potential of ion species ionized from the metal complex compound being nobler than 0.3 V based on a lithium reference electrode. A positive electrode containing a positive electrode active material capable of inserting and extracting lithium;
A negative electrode containing a negative electrode active material capable of alloying with lithium, or occluding and releasing lithium; and
In a non-aqueous secondary battery comprising a non-aqueous electrolyte containing an electrolyte that ionizes lithium ions and a non-aqueous solvent,
A non-aqueous secondary battery comprising a metal complex compound in the negative electrode, and a deposition potential of ion species ionized from the metal complex compound being nobler than 0.3 V based on a lithium reference electrode.   The metal element contained in the metal complex compound is any of Al, Si, Sc, Ti, V, Co, Ni, Cu, Zn, Zr, Nb, Ag, In, Sn, W, Ga, Pd, Pt, or Au. The nonaqueous secondary battery according to claim 1, wherein the nonaqueous secondary battery is a non-aqueous secondary battery. A positive electrode containing a positive electrode active material capable of inserting and extracting lithium;
A negative electrode containing a negative electrode active material capable of alloying with lithium, or occluding and releasing lithium; and
In a non-aqueous secondary battery comprising a non-aqueous electrolyte containing an electrolyte that ionizes lithium ions and a non-aqueous solvent,
The positive electrode has metal fine particles or a metal complex compound, and the precipitation potential of ion species eluted from the metal fine particles or ionized from the metal complex compound is nobler than 0.3 V on the basis of a lithium reference electrode. Non-aqueous secondary battery.   The metal element contained in the metal fine particles or the metal complex compound is Al, Si, Sc, Ti, V, Co, Ni, Cu, Zn, Zr, Nb, Ag, In, Sn, W, Ga, Pd, Pt. The nonaqueous secondary battery according to claim 4, wherein the battery is either Au or Au.   The non-aqueous secondary battery according to claim 1, wherein the negative electrode active material contains a lithium vanadium oxide.

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