JPH08102324A - Nonaqueous secondary battery - Google Patents

Abstract

PURPOSE: To provide a nonaqueous secondary battery with large charge/ discharge capacity. CONSTITUTION: A nonaqueous secondary battery comprises a positive electrode, a negative electrode, and an electrolyte prepared by dissolving an electrolyte in a nonaqueous solvent. Coke with a heat history of 400-700 deg.C is crushed and coke powder is heat-treated in an inert gas atmosphere at 900-100 deg.C, then used as a negative electrode material.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-aqueous secondary battery. More specifically, the present invention relates to a non-aqueous secondary battery such as a lithium secondary battery, which is particularly suitable for small and lightweight electronic devices.

[0002]

2. Description of the Related Art In recent years, clean non-aqueous batteries, especially lithium secondary batteries, which replace lead-acid batteries and nickel-cadmium batteries have been attracting attention from the standpoints of downsizing and weight saving of electronic devices, power saving, and environmental protection. Reached to. However, when lithium metal is used for the negative electrode, there is a problem that the lithium metal grows in a dendrite shape during charging and causes an internal short circuit. As a countermeasure, absorb lithium metal atoms
Materials that can be released are actively developed, and among them, those using coke are promising in terms of low cost and high capacity (JP-A-62-90863, JP-A-1-221859). , JP-A-63-1212257).

[0003]

However, although coal-based or petroleum-based coke has a high initial charge capacity, the charge / discharge capacity after that is equal to the value (372 mAh / g) proposed as the theoretical capacity of carbon. In about half, even if a battery is manufactured, the charge / discharge capacity is not sufficiently satisfied, and modification to increase the capacity is desired.

[0004]

The present inventors have arrived at the present invention as a result of extensive studies to solve the above problems.
That is, the gist of the present invention is a non-aqueous secondary battery comprising a positive electrode, a negative electrode, and an electrolytic solution in which an electrolyte is dissolved in a non-aqueous solvent, and coke that has undergone a heat history of 400 to 700 ° C. is crushed. The non-aqueous secondary battery is characterized in that it is used as a negative electrode material after being heat-treated in an inert gas atmosphere at a temperature of 900 to 1500 ° C.

The present invention will be described in detail below. First, the coke used in the present invention includes petroleum heavy oil such as FCC (fluid catalytic cracking) residual oil, EHE oil (by-product during ethylene production), atmospheric residual oil, reduced pressure residual oil, coal tar and coal. Heavy coal oil such as tar pitch is 400 to 50 by delayed coker, autoclave, etc.
Raw coke coked at a temperature of about 0 ° C., and this raw coke is then placed in a rotary kiln, electric furnace, etc.
Examples include calcined coke calcined at a temperature of 00 ° or less.

The battery of the present invention is characterized in that coke is used as a negative electrode material, and the coke is inactive in the crushed state of coke which has been subjected to a heat history of 400 to 700 ° C., as described below. 9 in a gas atmosphere
It must be heat-treated at a temperature of 00 to 1500 ° C. The heat history before the heat treatment is 400 to 700 ° C.
The heat history is preferably low, but coke having a heat treatment temperature of less than 400 ° C. contains a large amount of oil components such as anthracene oil and uncarbonized pitch components.
During the heat treatment at 1500 ° C., they are rapidly carbonized to have low crystallinity and become porous carbon, which deteriorates the battery characteristics. On the other hand, those that have undergone a thermal history at temperatures above 700 ° C. are 90% in the crushed state of the present invention.
There is almost no effect on heat treatment at 0 to 1500 ° C.

That is, in the present invention, it is important that the untreated organic matter in the coke is efficiently removed from the coke, and those that have been subjected to a heat history of more than 700 ° C. have almost no effect. It is considered that the organic matter was transformed into carbon, which is unfavorable for battery characteristics, at a temperature exceeding 700 ° C. Further, those that have been subjected to a heat history of less than 400 ° C have too much untreated organic matter content, and untreated organic matter cannot be sufficiently removed by the treatment at 900 to 1500 ° C in the inert atmosphere of the next step, This is probably due to the fact that untreated organic matter is rapidly carbonized.

Further, in the present invention, 900 to 1500
The particle size of the crushed coke to be subjected to the heat treatment at ℃ is usually selected from about 1 mm or less. Maximum particle size is 100 μm
It is preferably not more than 50 μm, more preferably not more than 50 μm. Examples of the inert gas include nitrogen gas, argon gas, helium gas, etc., but nitrogen is preferable for practical use. The flow rate, depending on the type of firing furnace, the state of coke filling, the amount of coke, the particle size of coke, the thermal history of coke, the blowing state of inert gas, the ventilation condition of the furnace, the pressure inside the furnace, the firing temperature, etc. The untreated organic matter may be appropriately set so as to be removed without being carbonized, and is not particularly limited.

The final heat treatment (baking) is 900
~ 1500 ° C. If the temperature is lower than 900 ° C, the ratio of the charge / discharge capacity after the second time to the initial charge capacity is low,
If the temperature exceeds 00 ° C, the capacity will decrease. Then, in the temperature range of 900 to 1500 ° C., the heating time may be relatively short if the heating temperature is high, and conversely, the heating time may be lengthened if the heating temperature is low.

In the present invention, the thus obtained
Was used as a negative electrode material for non-aqueous secondary batteries.
You. Electrolyte prepared by dissolving electrolyte in positive electrode and non-aqueous solvent
Regarding dissolution, it has been used in non-aqueous secondary batteries.
It may be any one and is not particularly limited. Specifically,
Then LiCoO₂, MnO₂, TiS₂, Fe
S₂, Nb₃S_Four, Mo ₃S_Four, CoS₂, V₂O_Five,
P₂O_Five, CrO₃, V₃O₃, TeO₂, GeO₂etc
However, as an electrolyte, LiClO_Four, LiBF_Four, Li
PF₆However, as a non-aqueous solvent that dissolves the electrolyte,
Pyrene carbonate, tetrahydrofuran, 1,2-di
Methoxyethane, dimethyl sulfoxide, dioxola
Dimethylformamide, dimethylacetamide,
And a mixed solvent of two or more of these is used.

Among them, the most preferable combination is LiCo.
O ₂ -LiPF ₆ - propylene carbonate and 1,2
It is dimethoxyethane. The separator is preferably a porous body in order to reduce the internal resistance of the battery, and a non-woven fabric such as polypropylene or an organic solvent resistant material such as a glass filter is used. These negative electrode, positive electrode, electrolytic solution and separator are generally incorporated in, for example, stainless steel or a battery case plated with nickel.

As a battery structure, a spiral structure in which a band-shaped positive electrode and a negative electrode are wound in a spiral shape with a separator interposed therebetween, or a method in which a pellet-shaped positive electrode and a disk-shaped negative electrode are inserted into a button type case through a separator, etc. are adopted. It Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to the following Examples unless the gist thereof is exceeded.

[0013]

【Example】

(Example 1) 4 coal tar pitch was autoclaved
Heat treatment was performed at 80 ° C. for 30 hours to obtain raw coke. The raw coke was crushed to 44 μm or less with a hammer mill and calcined in a nitrogen stream at 1100 ° C. for 3 hours to obtain coke of the present invention. FIG. 1 shows a half sectional view of a button type non-aqueous secondary battery as an embodiment of the present invention. Here, the negative electrode 1 is composed of the coke of the present invention. This negative electrode is the negative electrode current collector 2
The current collector 2 is fixed to the inside of the negative electrode can 3 made of ferritic stainless steel (SUS430).

The peripheral end of the negative electrode can 3 is fixed inside an insulating packing 4 made of polypropylene, and the outer periphery of the insulating packing 4 is made of stainless steel.
The positive electrode can 5 is fixed in the opposite direction. A positive electrode current collector 6 is fixed to the inner bottom surface of the positive electrode can 5, and a positive electrode 7 is fixed to the inner surface of the positive electrode current collector 6. A separator is interposed between the positive electrode 7 and the negative electrode 1 and is impregnated with an electrolytic solution in which an electrolyte is dissolved.

The negative electrode is made of coke and poly according to the present invention.
A mixture of propylene powder and a weight ratio of 90:10
It was made by pressure molding. The positive electrode is LiCoO₂And guidance
Acetylene black as an electric agent and fluorine as a binder
A mixture of a base resin and a weight ratio of 85: 10: 5
It was made by pressure molding. Also, the electrolyte solution should be propylene carbonate.
Carbonate (PC) with LiPF 6 as electrolyte ₆1 mo
The one dissolved at a ratio of 1 / liter was used. In addition, this
Regarding the capacity of the battery, the negative electrode is much smaller than the positive electrode.
The comb is set so that the negative electrode is dominant. This battery
Charge current and discharge current 1mA / cm²And charging is 3.
The discharge was performed up to 6V and the discharge up to 2.5V. The results are shown in Table 1.
You.

Example 2 The raw coke powder of Example 1 was heat-treated at 600 ° C. in an inert atmosphere and then heated in a nitrogen stream at 110 ° C.
After firing at 0 ° C. for 3 hours, the same evaluation as in Example 1 was performed.
The results are shown in Table 1. (Comparative Example 1) The raw coke powder of Example 1 was heat-treated at 800 ° C in an inert atmosphere and then calcined in a nitrogen stream at 1100 ° C for 3 hours, and the same evaluation as in Example 1 was performed. The results are shown in Table 1. (Comparative Example 2) The raw coke powder of Example 1 was placed in a nitrogen stream 16
After firing at 00 ° C. for 3 hours, the same evaluation as in Example 1 was performed. The results are shown in Table 1.

[0017]

[Table 1]

[0018]

According to the present invention, it is possible to provide a non-aqueous secondary battery having a large charge / discharge capacity, using low cost coke as a negative electrode material.

[Brief description of drawings]

FIG. 1 is a cross-sectional explanatory view of a button type non-aqueous electrolyte secondary battery which is an example of the non-aqueous secondary battery of the present invention.

[Explanation of symbols]

 1 Negative electrode 2 Negative electrode current collector 3 Negative electrode can 4 Insulating packing 5 Positive electrode can 6 Positive electrode current collector 7 Positive electrode

Claims (1)

[Claims] 1. A non-aqueous secondary battery comprising a positive electrode, a negative electrode, and an electrolytic solution in which an electrolyte is dissolved in a non-aqueous solvent, and a coke which has been subjected to a heat history of 400 to 700 ° C. in a crushed state. 900 to 150 in an inert gas atmosphere
A non-aqueous secondary battery, which is obtained by performing heat treatment at a temperature of 0 ° C. as a negative electrode material.