JP2003007342A - Manufacturing method of secondary nonaqueous battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a secondary nonaqueous battery, which has a large capacity and superior cycle characteristics. SOLUTION: The secondary nonaqueous battery having a negative electrode activator made of a complex material is manufactured, the complex material composed of silicon, silicon compound, or silicon and conductive material, After assembled, the secondary battery is charged at first until a crystalline silicon phase in the negative electrode activator disappears. The secondary battery is further charged once or more in such a way that the potential of the negative electrode becomes higher than that of metal lithium by more than 100 mV at the end of charge. When the conductive material is made of carbon, it is preferable that the complex material composed of silicon and conductive material should be a complex material made by covering part or the whole of the surface of silicon grains or silicon compound grains with carbon. When the conductive material is metal, it is preferable that the complex material composed of silicon and conductive material should be a complex material made by alloying metal with silicon.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a non-aqueous secondary battery, and more particularly, to a non-aqueous secondary battery characterized by manufacturing a non-aqueous secondary battery through a specific charging process after battery assembly. The present invention relates to a method of manufacturing a secondary battery.

[0002]

2. Description of the Related Art Non-aqueous secondary batteries typified by lithium secondary batteries have high capacity, high voltage, and high energy density, and therefore, there are great expectations for their development.

In this non-aqueous secondary battery, an organic solvent-based electrolytic solution in which a lithium salt is dissolved in an organic solvent is used, and lithium or a lithium alloy has been used as a negative electrode active material. When using, the capacity can be expected to increase, but an internal short circuit is likely to occur due to the dendrite growth of lithium during charging, and the deposited dendrite-like lithium has a high specific surface area and is highly reactive. It reacts with the solvent inside to form an interfacial film lacking electron conductivity, increasing the internal resistance of the battery and causing a decrease in charge / discharge efficiency. As a result, there are problems that the battery characteristics are deteriorated and the safety is deteriorated.

Therefore, in place of lithium or a lithium alloy, amorphous carbon such as coke or glassy carbon that can be doped or dedoped with lithium ions, or a carbon material such as natural or artificial graphite is used as the negative electrode active material. It has been proposed to use it as a substance (for example, Japanese Patent Laid-Open No. 1-2043).
61, Japanese Patent Application Laid-Open No. 2-66856, and Japanese Patent Application Laid-Open No. 4-
No. 24831, JP-A-5-17669, etc.). However, the capacity per unit volume is insufficient regardless of whether an amorphous or crystalline carbon material is used, and further improvement in performance is desired.

Therefore, in order to increase the capacity per unit volume, attempts have been made to use silicon or its compounds as the negative electrode active material. For example, JP-A-7-2960
No. 2 gazette discloses a non-aqueous secondary battery using Li _x Si (0 ≦ x ≦ 5) as a negative electrode active material.

However, the above-mentioned metal-based negative electrode material having a capacity higher than that of carbon, when repeatedly charged and discharged, becomes fine powder due to expansion and contraction, causing swelling of the negative electrode and unnecessary absorption of the electrolytic solution. There was a problem of deterioration. Therefore, in order to solve the above problem, Japanese Patent Laid-Open No. 2000-21
5887 discloses that the carbon layer suppresses the expansion of the negative electrode by coating the surface of the silicon particles with carbon. Further, in the patent, in a battery charging method using a silicon-containing negative electrode, the final charging voltage of the negative electrode is 30.
It was regulated to -100 mV.

[0007]

However, it has been difficult to obtain practical cycle characteristics even by the above method. The reason is considered as follows.

Silicon contains eight silicon atoms in its crystallographic unit cell (cubic crystal, space group Fd-3m). Converted from the lattice constant a = 0.5431 nm, the unit lattice volume is 0.1592 nm ³ , and the volume occupied by one silicon atom (the value obtained by dividing the unit lattice volume by the number of silicon atoms in the unit lattice) is 0. It is 0199 nm ³ . When the silicon negative electrode is charged to 100 mV or less (containing lithium), a lithium-rich compound Li ₁₅ Si ₄ or Li
₂₂ Si ₁₅ is produced, and the capacity corresponds to about 4000 mAh / g, but the volume expansion coefficient becomes extremely large. For example, Li ₂₁
Si ₁₅ crystallographic unit cell (cubic, space group F-43
m) contains 83 silicon atoms. Converted from the lattice constant a = 1.750 nm, the unit lattice volume is 6.5918 nm ³ , and the volume per silicon atom is 0.079 nm ³ . This value is 3.95 times that of elemental silicon, and the material expands extremely greatly. Since the volume difference between charging and discharging is extremely large as described above, it is considered that a large strain is generated in the material, cracks are generated, and the particles are miniaturized. Further, it is considered that a space is generated between the finely divided particles, the electron conduction network is divided, the portion that cannot participate in the electrochemical reaction increases, and the charge / discharge capacity decreases.

An object of the present invention is to solve the above-mentioned problems of the prior art and to provide a non-aqueous secondary battery having a high capacity and excellent cycle characteristics.

[0010]

In order to solve the above problems, the present invention provides a non-aqueous secondary battery having a negative electrode active material of silicon, a silicon compound or a composite material of silicon and a conductive material. During charging for forming the assembled battery, in the first charge, silicon in the negative electrode active material reacts with lithium to form an alloy of silicon and lithium, and the crystalline silicon phase in the negative electrode active material. Is charged until the battery disappears, and in the second and subsequent charges, the potential of the negative electrode is higher than 100 mV with respect to metallic lithium, that is, in the cyclic voltatan gram or the differential curve of charging and discharging (control electrode: metallic lithium). , Charging from the high potential side to end at the potential before the second cathode peak starts.

That is, in the present invention, the silicon phase in the negative electrode active material is the lithium silicon alloy Li after the first charging.
_The battery is charged until _x Si (2 ≦ x ≦ 4) is reached, and in the second and subsequent charges, the final compound to be charged is changed from Li ₂ Si to Li.
The range is up to ₂₁ Si ₈ , which allows the expansion coefficient of silicon to be reduced to about half and the cycle characteristics to be greatly improved.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below. As the silicon compound in the present invention, for example, silicon oxide can be used. As the composite material composed of silicon and a conductive substance, any composite material of silicon and a conductive substance can be used. To exemplify a typical one of them, carbon or a metal such as nickel, copper, tin, or aluminum can be used as the conductive substance, and when the conductive substance is carbon, it can be composed of silicon and the conductive substance. Examples of the composite material include a composite material obtained by coating a part or all of the surface of particles of silicon or a silicon compound with carbon. Further, in coating the surface of the particles of silicon or silicon compound as described above, for example, various resins, using a carbon precursor such as tar or pitch, after coating the surface of the particles of silicon or silicon compound, followed by firing. The carbon precursor may be converted into carbon. When the conductive substance is a metal such as nickel, copper, tin, or aluminum, the composite material of silicon and metal includes an alloy of silicon and metal, and the alloy includes a solid solution of silicon and metal. Any of the intermetallic compounds of silicon and metal may be used.

The amount of silicon in the composite material composed of silicon and a conductive substance as described above may be determined according to the capacity of the battery to be produced and is not particularly limited, but may be 5 to 5. 80% by weight is preferred.

When coating the surface of the silicon or silicon compound particles with carbon, the coating may be carried out on a part or the whole of the surface of the silicon or silicon compound particles. That is, it is preferable that the coating with carbon is performed on the entire surface of the particles of silicon or a silicon compound, but if the carbon coating the surface suppresses the expansion of the negative electrode, the coating is performed only on a part thereof. You may be told.

After assembling a non-aqueous secondary battery using the above-mentioned silicon, a silicon compound or a composite material comprising silicon and a conductive material as a negative electrode active material, the battery after the assembly is charged to form 1 The second charging is performed until the crystalline silicon phase in the negative electrode active material disappears, but the charging method is not particularly limited, but constant current charging or a combination of constant current charging and constant voltage charging is used. It is preferable to carry out the above method. For example, until the set voltage (E) is reached, a constant current charging region where charging is performed at a constant current value (I), and after reaching the set voltage (E), a constant voltage charging is performed at the set voltage (E). It is preferable that the charging is performed in combination with the constant voltage charging region. At that time, it is preferable that the charging current density is small. The first charge is performed until the crystalline silicon phase in the negative electrode active material disappears and silicon becomes an alloy Li _x Si (2 ≦ x ≦ 4) of lithium and silicon. Li _x Si is the final compound for this first charge.
(2 ≦ x ≦ 2.625) is preferable. That is, Li ₂
When the amount of lithium is smaller than that of Si, the negative electrode active material is not fully utilized and the capacity becomes low. When the amount of lithium is larger than that of Li ₂₁ Si ₈ , the expansion coefficient becomes large and the cycle characteristics may be deteriorated.

In the second and subsequent charging, the charge end voltage is set to 1
Regulate to a voltage higher than 00 mV. That is, in the charge / discharge differential curve (control electrode: metallic lithium), charging is completed from the high potential side to the potential before the second cathode peak starts. The potential to terminate this charging is 150 to 25
0 mV, that is, the potential of the negative electrode is 1 with respect to metallic lithium
It is preferable to terminate the charging at 50 to 250 mV.

In the present invention, the necessity of the conductive auxiliary agent for the negative electrode varies depending on the kind of the negative electrode active material used. For example, when the negative electrode active material is silicon or a silicon compound, a conductive auxiliary agent is necessary, but when the negative electrode active material is a composite material composed of silicon and a conductive material, it has conductivity by itself. Although a conductive auxiliary agent is not always required, it is preferable to use a conductive auxiliary agent in order to make the negative electrode have sufficient conductivity even when using this composite material. The conductive auxiliary agent used for such a purpose is not particularly limited as long as it is an electron conductive material that has electronic conductivity and does not cause a chemical change in the constituted non-aqueous secondary battery. For example, natural graphite (scaly graphite, earthy graphite, etc.), artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, metal powder (metals such as copper, nickel, aluminum and silver) can be used. Powder), metal fiber, polyphenylene derivative (JP-A-59-
It is preferable to use one kind or two or more kinds of conductive substances such as 20971).

In the present invention, the binder for the negative electrode may be either a thermoplastic resin or a thermosetting resin. Then, specific examples of the binder for the negative electrode include, for example, starch, polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, regenerated cellulose, diacetyl cellulose, polyvinyl chloride, polyvinylpyrrolidone, tetrafluoroethylene, polyvinylidene fluoride, polyethylene. , Polypropylene, ethylene-propylene-diene terpolymer (EPDM), sulfonated EPDM, styrene-butadiene rubber, butadiene rubber, polybutadiene, fluororubber, polysaccharides such as polyethylene oxide, thermoplastic resins, polymers having rubber elasticity, and the like. One kind or two or more kinds of modified forms can be used.

In the present invention, as the positive electrode active material,
There is no limitation and various types can be used.
But especially Li_xCoO₂, Li_xNiO₂, Li_xMn
O₂, Li_xCo_yNi_1-yO₂, Li_xCo_yM_1-y
O_z, Li_xNi_1-yM_yO _z, Li_xMn₂O_Four, L
i_xMn_2-yM_yO_Four(Where M = Mg, Mn, F
e, Co, Ni, Cu, Zn, Al, Cr
1 and x, y, and z are 0 ≦ x ≦ 1.
1,0 <y <1.0, 2.0 ≦ z ≦ 2.2) etc.
The lithium-containing transition metal oxide of is preferably used.

In the present invention, the conductive additive for the positive electrode is not particularly limited as long as it is an electron conductive material that does not cause a chemical change at the charge / discharge potential of the positive electrode active material used, but various ones can be used. , For example, natural graphite (scaly graphite etc.), graphite such as artificial graphite, carbon black such as acetylene black, Ketjen black, channel black, furnace black, lamp black, thermal black, carbon fiber, metal fiber, etc. One kind or two or more kinds of conductive fibers can be used. Among these conductive aids, artificial graphite and acetylene black are particularly preferable.

The binder for the positive electrode used in the present invention may be either a thermoplastic resin or a thermosetting resin. And, as the binder for this positive electrode, for example, polyethylene, polypropylene, polytetrafluoroethylene (P
TFE), polyvinylidene fluoride (PVdF), styrene butadiene rubber, tetrafluoroethylene-hexafluoroethylene copolymer, tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-chlorotrifluoroethylene copolymer, ethylene-tetrafluoroethylene copolymer (ETFE resin), etc.
More than one seed is used. Among these, polyvinylidene fluoride and polytetrafluoroethylene are particularly preferable.

As the non-aqueous electrolyte in the present invention, either a liquid electrolyte (electrolyte solution) or a gel electrolyte obtained by gelating the above liquid electrolyte can be used. Usually, a liquid electrolyte called an electrolyte solution is used. Since there are many, the liquid electrolyte will be described in detail below as an electrolyte.

The electrolytic solution is composed of a non-aqueous solvent such as an organic solvent and an electrolyte salt such as a lithium salt dissolved in the solvent. That is, the electrolytic solution is prepared by dissolving the electrolyte salt in the non-aqueous solvent. As the organic solvent,
For example, propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, γ-
Butyrolactone, 1,2-dimethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, dimethylsulfoxide, 1,3-dioxolane, formamide,
Dimethylformamide, dioxolane, acetonitrile, nitromethane, methyl formate, methyl acetate, phosphoric acid triester, trimethoxymethane, dioxolane derivative,
At least one kind of aprotic organic solvent such as sulfolane, 3-methyl-2-oxazolidinone, propylene carbonate derivative, tetrahydrofuran derivative, diethyl ether, and 1,3-propane sultone is used,
Examples of the electrolyte salt include LiClO ₄ , LiB
F ₄ , LiPF ₆ , LiCF ₃ SO ₃ , LiCF ₃ CO
₂ , LiAsF ₆ , LiSbF ₆ , LiB ₁₀ Cl ₁₀ , lower aliphatic lithium carboxylate, LiAlCl ₄ , LiC
One, two or more of 1, 1, LiBr, LiI, lithium chloroborane, lithium tetraphenylborate and the like are used. The concentration of the electrolyte salt in the electrolytic solution is not particularly limited, but is preferably about 0.2 to 3.0 mol / l.

The gel electrolyte corresponds to a gel of the above-mentioned electrolytic solution with a gelling agent. For the gelation, for example, a linear polymer such as polyvinylidene fluoride, polyethylene oxide, polyacrylonitrile, or the like. , A polyfunctional monomer that is polymerized by irradiation with actinic rays such as ultraviolet rays, electron rays, visible rays, and far infrared rays (for example, pentaerythritol tetraacrylate, ditrimethylolpropane tetraacrylate, ethoxylated pentaerythritol tetraacrylate, dipentaerythritol hydroxy). Polymers obtained by polymerizing tetra-functional or higher acrylates such as pentaacrylate and dipentaerythritol hexaacrylate, and tetra-functional or higher methacrylates similar to the above acrylates, etc. It is needed.

The shape of the battery is not particularly limited, and may be any shape such as coin shape, button shape, sheet shape, laminated shape, cylindrical shape, flat shape, and prismatic shape. In addition, it can be applied not only to small-sized ones but also large-sized ones used in electric vehicles and the like.

[0026]

The present invention will be described in more detail with reference to the following examples. However, the present invention is not limited to those examples.

Example 1 To 90 parts by weight of silicon particles having an average particle size of 10 μm, 5 parts by weight of carbon powder and 5 parts by weight of polyvinylidene fluoride were added and mixed, and these were added to dehydrated N-methyl-2-pyrrolidone. A negative electrode mixture-containing paste was prepared by dispersion, and the negative electrode mixture-containing paste was applied onto a negative electrode current collector made of copper foil, dried and then rolled to prepare an electrode. This was cut into a disk shape having a diameter of 16 mm, and the disk electrode was dried under vacuum for 24 hours.

The above disk-shaped electrode is combined with lithium metal.
Used together, a coin-shaped model cell was assembled. electrolytic
Liquid is propylene carbonate and dimethyl carbonate
LiPF in a mixed solvent with (volume ratio 1: 1)₆1 mol
/ L dissolved was used. The charging / discharging method of the above cell is as follows.
I went as below. The first charge has a current density of 0.5 mA
/ Cm²60m with constant current of 60mV
After reaching V, the current density becomes 1/10 of the constant current charge.
Constant voltage charging was performed until. This charge is silicon
_2.3This is equivalent to making Si. All discharges are current density
0.5 mA / cm ²The discharge end voltage is 2.
It was set to 0V. Charging after the second time (second cycle) is
Flow density 0.5 mA / cm²Performed with constant current of end-of-charge voltage
Is 150 mV (Example 1-1) and 250 mV (Example 1)
-2). That is, the charge / discharge differential curve shown in FIG.
(Control electrode: metallic lithium) From the higher potential side, the second cathode
We decided to stop charging at the potential before the peak started.
It was And charge and discharge is performed up to 50 cycles and 2 cycles
The discharge capacity at the second and 50th cycles was measured. Note that the figure
The vertical axis of 1 is dQ / dE, which is dQ / dE
It is the differential of the battery capacity (Q) with respect to the voltage (E), and the horizontal axis
Indicates the potential of the negative electrode with respect to metallic lithium.
It

Comparative Example 1 Assembling and charging / discharging of the cell were performed in the same manner as in Example 1 except that the end-of-charge voltage after the second cycle was set to 80 mV.

Table 1 shows the performance evaluation results of the negative electrode in the cells of Example 1 and Comparative Example 1 described above. The discharge capacities shown in Table 1 are calculated per 1 g of silicon. Also,
This is the same in the following tables showing discharge capacities.
The capacity retention rate at the 50th cycle is calculated by dividing the discharge capacity at the 50th cycle by the discharge capacity at the second cycle, and
It was calculated by multiplying by 00. That is, the capacity retention rate was obtained based on the following formula.

[0031]

[Table 1]

As shown in Table 1, Examples 1-1 and 1-2
Had a high capacity retention of 70% or more even at the 50th cycle, and had excellent cycle characteristics, but Comparative Example 1 had a significantly low capacity retention at the 50th cycle.
The cycle characteristics were inferior.

Example 2 Instead of the silicon particles in Example 1, an average particle size of 0.1
Average particle size of silicon coated with carbon on the surface of 15 μm
A silicon-carbon composite material (composite material composed of silicon and carbon, the content of silicon in which is 60% by weight) having a thickness of μm was used as the negative electrode active material.
The cell was assembled and charged / discharged in the same manner as in Example 1 to determine the discharge capacity and the capacity retention rate at the 50th cycle. The results are shown in Table 2.

Comparative Example 2 A cell was assembled and charged / discharged in the same manner as in Example 2 except that the end-of-charge voltage after the second cycle was set to 80 mV, and the discharge capacity and the discharge retention rate at the 50th cycle were obtained. . The results are shown in Table 2.

[0035]

[Table 2]

As shown in Table 2, Examples 2-1 to 2-2
Had a high capacity retention rate of 90% or more even at the 50th cycle and had excellent cycle characteristics, but Comparative Example 2 had a low capacity retention rate at the 50th cycle of 25% and had a good cycle characteristic. Was inferior.

Example 3 Instead of silicon particles, a solid solution of silicon and aluminum (a kind of composite material composed of silicon and aluminum, and the content of silicon in this solid solution is 80% by weight) is used as a negative electrode. Example 1 except that it was used as the active material
The cell was assembled and charged / discharged in the same manner as in 1. to determine the discharge capacity and the capacity retention rate at the 50th cycle. The results are shown in Table 3.

Comparative Example 3 A cell was assembled and charged / discharged in the same manner as in Example 3 except that the end-of-charge voltage after the second cycle was set to 80 mV, and the discharge capacity and the capacity retention rate at the 50th cycle were obtained. . The results are shown in Table 3.

[0039]

[Table 3]

As shown in Table 3, Examples 3-1 to 3-2
Had a high capacity retention rate of 82% or more even at the 50th cycle and had excellent cycle characteristics, but Comparative Example 3 had a very low capacity retention rate at the 50th cycle of 6%, The cycle characteristics were inferior.

Example 4 Using the silicon-carbon composite material of Example 2 as the negative electrode active material and LiCoO ₂ as the positive electrode active material, the diameter of 18
A cylindrical non-aqueous secondary battery having a size of 65 mm and a height of 65 mm was assembled. The battery charge after assembly is 800mA (approx. 1 /
3C) constant current charging (CC) and constant voltage charging (CV) were performed in combination. The charging was stopped at the time when the charging current value reached 80 mA in the constant voltage region (E). The first charge cutoff voltage was set to 4.25V. This 4.25V
The charge end voltage of the negative electrode corresponds to 50 mV with respect to metallic lithium. And the discharge is 800
The discharge end voltage was set to 2.5 V with a constant current of mA. Two
Charging after the second time (second cycle) is performed by constant current charging of 800 mA, and the charge end voltages thereof are 4.15 V (Example 4-1), 4.1 V (Example 4-2) and 4.05 V ( It was set to Example 4-3). These have a potential of 150 mV (Example 4
-1) and 200 V (Example 4-2) and 250 mV (Example 4-3). Then, charging and discharging were performed up to 100 cycles, the discharge capacities at the second cycle and the 100th cycle were measured, and the capacity retention rate at the 100th cycle was calculated from the discharge capacities based on the following formula.

FIG. 2 shows a charge / discharge curve when the end-of-charge voltage is 4.15V. As shown in FIG. 2, this battery has a discharge capacity of 2500 mAh and an average operating voltage of 3.5.
It was V.

Here, the negative electrode of the cylindrical non-aqueous secondary battery,
The configurations of the positive electrode and the electrolytic solution and the battery structure will be described in detail. First, 5 parts by weight of carbon powder and 5 parts by weight of polyvinylidene fluoride were mixed with 90 parts by weight of the silicon-carbon composite material of Example 2. However, for the mixing, the polyvinylidene fluoride is dissolved in N-methyl-2-pyrrolidone in advance, and N-methyl-2 of this polyvinylidene fluoride is mixed.
A silicon-carbon composite material and carbon powder were added to the pyrrolidone solution, and mixed and dispersed to prepare a slurry-containing negative electrode mixture-containing paste. The paste containing the negative electrode mixture has a thickness of 15 μm.
A predetermined amount was uniformly applied onto the negative electrode current collector made of the copper foil and dried to form a negative electrode mixture layer. Similarly, a predetermined amount of the negative electrode mixture-containing paste is evenly applied to the back surface of the negative electrode current collector made of the copper foil, and dried to form a negative electrode mixture layer,
It was rolled and then cut into strips of a predetermined size to obtain a negative electrode.

Further, with respect to 92 parts by weight of LiCoO ₂ ,
3 parts by weight of acetylene black and 5 parts by weight of polyvinylidene fluoride were added and mixed. However, in the mixing, the polyvinylidene fluoride is dissolved in N-methyl-2-pyrrolidone in advance, and the polyvinylidene fluoride N
LiCoO ₂ and acetylene black were added to the methyl-2-pyrrolidone solution, and the mixture was thoroughly mixed and dispersed to prepare a paste containing a positive electrode mixture. A predetermined amount of this positive electrode mixture-containing paste was uniformly applied onto a positive electrode current collector made of an aluminum foil having a thickness of 20 μm and dried to form a positive electrode mixture layer.
Similarly, the positive electrode mixture-containing paste is applied evenly on the back surface of the positive electrode current collector made of the aluminum foil in a predetermined amount,
After being dried to form a positive electrode mixture layer, it was rolled and then cut into strips of a predetermined size to obtain a positive electrode.

A separator made of a microporous polyethylene film having a thickness of 25 μm is arranged between the strip-shaped positive electrode and the strip-shaped negative electrode produced as described above, and the spirally wound electrode body is formed by spirally winding the separator. Insert in the bottom cylindrical battery case,
The positive electrode lead body and the negative electrode lead body were welded.

Then, 1 mol / l L was placed in the battery case.
iPF ₆ / EC / DEC (electrolyte solution having a volume ratio of 1: 2 [that is, 1 mol / l of LiPF ₆ was dissolved in a mixed solvent of ethylene carbonate (EC) and diethyl carbonate (DEC) at a volume ratio of 1: 2) Non-aqueous electrolyte]
Was injected.

Then, the opening of the battery case was sealed according to a conventional method, and a cylindrical non-aqueous secondary battery having an outer diameter of 18 mm and a height of 65 mm was manufactured with the structure shown in FIG.

The battery shown in FIG. 3 will be described below. 1 is the positive electrode and 2 is the negative electrode. However, in order to avoid complication, FIG. 3 does not show a metal foil or the like as a current collector used for manufacturing the positive electrode 1 and the negative electrode 2. The positive electrode 1 and the negative electrode 2 are spirally wound via the separator 3 and housed in the battery case 5 as a spiral electrode body together with the electrolyte 4 made of the specific electrolytic solution.

The battery case 5 is made of stainless steel, and an insulating plate 6 made of polypropylene is arranged on the bottom of the battery case 5 prior to the insertion of the spiral electrode body. The sealing plate 7 is
It is made of aluminum and has a disk shape, and a thin portion 7a is provided in the center thereof, and a hole as a pressure introducing port 7b for causing the internal pressure of the battery to act on the explosion-proof valve 9 is provided around the thin portion 7a. ing. The protruding portion 9a of the explosion-proof valve 9 is welded to the upper surface of the thin portion 7a to form the welded portion 11. The thin portion 7a provided on the sealing plate 7 and the protruding portion 9a of the explosion-proof valve 9 are shown only on the cut surface for easy understanding in the drawings, and the contour line behind the cut surface is shown. Are not shown. In addition, the thin portion 7a of the sealing plate 7
The welded portion 11 of the explosion-proof valve 9 and the protruding portion 9a of the explosion-proof valve 9 is also shown in an exaggerated state from the actual state for easy understanding in the drawings.

The terminal plate 8 is made of rolled steel, has a nickel-plated surface, and has a cap-like shape with a brim-shaped peripheral portion. The terminal plate 8 is provided with a gas outlet 8a. The explosion-proof valve 9 is made of aluminum and has a disk shape. A protrusion 9a having a tip is provided on the power generating element side (lower side in FIG. 3) in the center thereof, and a thin portion 9b is provided. The
The lower surface of the protruding portion 9a is welded to the upper surface of the thin portion 7a of the sealing plate 7 to form the welded portion 11 as described above. The insulating packing 10 is made of polypropylene and has an annular shape. The insulating packing 10 is arranged above the peripheral edge of the sealing plate 7, and the explosion proof valve 9 is arranged on the upper part thereof to insulate the sealing plate 7 and the explosion proof valve 9 from each other. The gap between the two is sealed so that the liquid electrolyte does not leak from between the two. The annular gasket 12 is made of polypropylene, the lead body 13 is made of aluminum, the sealing plate 7 and the positive electrode 1 are connected, the insulator 14 is arranged on the upper part of the electrode stack, and the negative electrode 2 and the bottom part of the battery case 5 are arranged. And are connected by a lead body 15 made of nickel.

In this battery, the thin portion 7 of the sealing plate 7
a and the projection 9a of the explosion-proof valve 9 contact at the welded portion 11,
Since the peripheral portion of the explosion-proof valve 9 and the peripheral portion of the terminal plate 8 are in contact with each other and the positive electrode 1 and the sealing plate 7 are connected by the lead body 13 on the positive electrode side, in a normal state, the positive electrode 1 and the terminal plate 8 are connected. Is the lead body 13, the sealing plate 7, the explosion-proof valve 9 and their welded parts 1
1 provides an electrical connection and functions normally as an electric circuit.

When an abnormal situation occurs in the battery, such as the battery being exposed to high temperature or generating heat due to overcharging, gas is generated inside the battery and the internal pressure of the battery rises. The central portion of the explosion-proof valve 9 is deformed in the internal pressure direction (upward direction in FIG. 3), and the shearing force acts on the thin portion 7a of the sealing plate 7 that is integrated at the welded portion 11 accordingly, and the thin portion 7a is broken, or a welded portion 1 between the protruding portion 9a of the explosion-proof valve 9 and the thin portion 7a of the sealing plate 7
After 1 is peeled off, the thin-walled portion 9b provided in the explosion-proof valve 9 is split and gas is discharged from the gas discharge port 8a of the terminal plate 8 to the outside of the battery to prevent the battery from bursting. Is designed.

Comparative Example 4 The charge end voltage after the second time (second cycle) was 4.22.
V (This is 80m at the potential against the metallic lithium of the negative electrode.
The battery was assembled and charged / discharged in the same manner as in Example 4 except that the discharge capacity and the capacity retention ratio at the 100th cycle were obtained.

Examples 4-1 to 4-3 and Comparative Example 4
Table 4 shows the discharge capacities at the second cycle and the 100th cycle and the capacity retention rate at the 100th cycle of the battery. In addition, in Table 4, the potential of the negative electrode with respect to metallic lithium is shown in parentheses together with the charge / discharge end voltage of the battery.

[0055]

[Table 4]

As shown in Table 4, Examples 4-1 to 4-3
Had a high capacity retention rate of 90% or more even at the 100th cycle, and had excellent cycle characteristics.
Even if the same material is used for the negative electrode, the end-of-charge voltage after the second cycle is 80 m at the potential with respect to the metallic lithium of the negative electrode.
In Comparative Example 4 having a low V, the capacity retention at the 100th cycle was as low as 14%, and the cycle characteristics were inferior.

Example 5 A battery was assembled and charged / discharged in the same manner as in Example 4 except that LiNiO ₂ was used as the positive electrode active material instead of LiCoO ₂ , and the discharge capacity and the capacity retention ratio at the 100th cycle were measured. I asked. In addition, the charge end voltage after the second time (second cycle) in Example 5 is 4.15V (Example 5-1) and 4.1V (Example 5-) as in Example 4.
2) and 4.05 V (Example 5-3) (these are 150 m at the potential with respect to metallic lithium of the negative electrode, respectively).
V, 200 mV, and 250 mV). Table 5 shows the discharge capacities at the second cycle and the 100th cycle and the capacity retention rate at the 100th cycle of the battery of Example 5.

Comparative Example 5 The charge end voltage after the second time (second cycle) was 4.22.
V (This is 80m at the potential against the metallic lithium of the negative electrode.
The battery was assembled and charged and discharged in the same manner as in Example 5 except that the discharge capacity and the capacity retention ratio at the 100th cycle were obtained. The results are shown in Table 5.

[0059]

[Table 5]

As shown in Table 5, Examples 5-1 to 5-3
Had a high capacity retention rate of 82% or more even at the 100th cycle and had excellent cycle characteristics.
In Comparative Example 5, the capacity retention at the 100th cycle was as low as 10%, and the cycle characteristics were inferior.

Example 6 A battery was assembled and charged / discharged in the same manner as in Example 4 except that LiMn ₂ O ₄ was used as the positive electrode active material instead of LiCoO ₂ , and the discharge capacity and the capacity retention at the 100th cycle were maintained. I asked for the rate. In addition, the charge end voltage after the second time (second cycle) in Example 6 is 4.15V (Example 6-1) and 4.1V (Example 6-2) as in Example 4. And 4.05 V (Example 6-3).
mV, 200 mV, and 250 mV).
The discharge capacity at the second cycle and the 100th cycle and the capacity retention rate at the 100th cycle of the battery of this Example 6 are shown in Table 6.
Shown in.

Comparative Example 6 The end-of-charge voltage after the second time (second cycle) was also 4.22.
V (This is 80m at the potential against the metallic lithium of the negative electrode.
(Corresponding to V) except that it is set to
Assemble and charge the battery to obtain the discharge capacity of 100
The capacity retention rate at the cycle was calculated. The results are shown in Table 6.

[0063]

[Table 6]

As shown in Table 6, Examples 6-1 to 6-3
Had a high capacity retention rate of 87% or more even at the 100th cycle, and had excellent cycle characteristics.
In Comparative Example 6, the capacity retention at the 100th cycle was as low as 41%, and the cycle characteristics were inferior. Also, from Table 4 above
As shown in FIG. 6, Examples 4 to 6 are cylindrical batteries having a diameter of 18 mm and a height of 65 mm, and 2000 mA at the second cycle.
It had a capacity of h or more, and all had a high capacity.

[0065]

As described above, according to the present invention, a non-aqueous secondary battery having a high capacity and excellent charge / discharge cycle characteristics can be provided.

[Brief description of drawings]

FIG. 1 is a diagram showing a charge / discharge differential curve (reference electrode: metallic lithium).

FIG. 2 is a diagram showing a charge-discharge curve when the end-of-charge voltage after the second cycle of the battery of Example 4 was set to 4.15 V (this corresponds to 150 mV in potential with respect to metallic lithium of the negative electrode).

FIG. 3 is a sectional view schematically showing an example of a non-aqueous secondary battery according to the present invention.

[Explanation of symbols]

1 positive electrode 2 Negative electrode 3 separator

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Shigeo Aoyama             Hitachima, 1-88, Torora, Ibaraki City, Osaka Prefecture             Within Kucsel Co., Ltd. F-term (reference) 4K018 BA20 BC21 BD04 KA38                 5H029 AJ03 AJ05 AK02 AL01 AL06                       AL11 AM02 AM07 BJ02 BJ14                       HJ18                 5H050 AA02 AA07 BA15 CA02 CB01                       CB11 FA18 HA13 HA18

Claims (4)

[Claims] 1. When manufacturing a non-aqueous secondary battery using silicon, a silicon compound or a composite material of silicon and a conductive material as a negative electrode active material, the assembled battery has a negative electrode potential of 100 mV against metallic lithium. A method for producing a non-aqueous secondary battery, which comprises charging so as to terminate at a higher potential. 2. In manufacturing a non-aqueous secondary battery using silicon, a silicon compound or a composite material composed of silicon and a conductive material as a negative electrode active material, the assembled battery is charged with the negative electrode active material at the first charge. The non-aqueous secondary battery is characterized in that it is charged until the crystalline silicon phase therein disappears, and in the second and subsequent charges, the negative electrode is charged so as to terminate at a potential higher than 100 mV with respect to metallic lithium. Battery manufacturing method. 3. The conductive material is carbon, and the composite material composed of silicon and the conductive material is a composite material in which a part or all of the surface of silicon particles or silicon compound particles is coated with carbon. Claim 1 or 2 characterized by the above.
A method for producing the non-aqueous secondary battery described. 4. The conductive material is a metal, and the composite material composed of silicon and a conductive material is a composite material obtained by alloying silicon and a metal. Non-aqueous secondary battery manufacturing method of.