JPH11185809A - Lithium second battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lithium secondary battery that allows the amount for irreversible capacity of lithium to be rapidly doped into a carbonaceous material constituting a negative electrode active material after the assembly of the battery without lowering energy density or adding a doping process and is thereby brought into a usable condition immediately after the assembly of the battery. SOLUTION: In a lithium secondary battery having a positive electrode 1 containing lithium expressed by a chemical formula LiMn2 O4 , a negative electrode 2 where a lithium metal 9 formed from a carbonaceous material is arranged in a short-circuited form, and a nonaqueous electrolytic solution, aromatic hydrocarbon to form a complex in cooperation with the lithium metal 2 such as naphthalene, phenanthlene and anthracene is added to the nonaqueous electrolytic solution at a mixing ratio of not more than 0.005 mol.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a charge / discharge cycle characteristic and a charge / discharge cycle by doping lithium corresponding to an irreversible capacity into a carbonaceous material constituting a negative electrode without adding a lithium releasing step of the positive electrode. The present invention relates to a lithium secondary battery having an improved capacity.

[0002]

2. Description of the Related Art In recent years, with the remarkable progress of electronic technology, electronic devices have been reduced in size and weight, and accordingly, there has been a demand for smaller and lighter batteries with higher energy density. In this type of battery, a non-aqueous battery such as a lithium-ion secondary battery has been conventionally used instead of an alkaline battery such as a nickel-cadmium battery because of its high energy density, large capacity, and excellent storage performance. Electrolyte secondary batteries are being used.

Meanwhile, a lithium secondary battery uses a lithium metal or a lithium alloy as an active material of a negative electrode material, and a carbonaceous material capable of reversibly inserting and extracting lithium at a low potential. Some are used,
Secondary batteries that use lithium metal or a lithium alloy as the negative electrode active material have the disadvantages of lithium precipitation and alloy micronization, whereas secondary batteries that use a carbonaceous material as the negative electrode material do not. There are no significant drawbacks, and thus good cycle characteristics can be obtained.

[0004] Here, a secondary battery using the carbonaceous material for the negative electrode does not enter a dischargeable state unless charged after assembly. That is, when the battery of this type is charged in the first cycle, lithium in the positive electrode is electrochemically doped between the layers of the negative electrode carbonaceous material to be in a dischargeable state. The reversible charge / discharge cycle in which the doped lithium is dedoped and returns to the positive electrode again is repeated.

[0005] However, in this carbonaceous material, although the degree varies depending on the type of the electrolytic solution, the dedoping amount is 1 to the doping amount of lithium in the first cycle.
It does not become 00%, and some% is inactivated and remains in the carbonaceous material, and does not participate in the subsequent cycle.

On the other hand, the charge / discharge reaction is carried out by moving lithium ions from the positive electrode to the negative electrode and from the negative electrode to the positive electrode, so that the amount of movable lithium is the charge / discharge capacity of the battery. However, as described above, the amount of lithium ions that can move during the undoping in the first cycle decreases, so that charge and discharge are repeated with the capacity reduced throughout the subsequent cycles.

As means for solving this problem, (1) a positive electrode material containing an amount of lithium corresponding to a capacity loss generated in the first cycle at the negative electrode is supplemented. A method of providing a step of doping lithium into a porous material.

However, the method (1) has a drawback that the volume and the weight energy density decrease because the battery space is occupied by the increased amount of the positive electrode material.

In the method (2), it is necessary to provide a step of doping lithium into the carbonaceous material in the battery manufacturing process. That is, as specific examples of these steps,
A method in which gas phase lithium is brought into contact with a carbonaceous material by heating, a method in which carbonaceous powder and lithium metal are mixed in an inert gas or dehumidified air atmosphere, and then heated or pressurized; And a method of externally short-circuiting or electrolyzing the counter electrode of the carbonaceous material electrode with lithium metal in an organic electrolytic solution containing. However, each of these methods involves complicated processing, and has a drawback of increasing the cost and the number of steps for installing mass-production equipment and increasing the manufacturing unit price associated therewith.

As means for solving the above-mentioned problems, there is one disclosed in Japanese Patent Application Laid-Open No. 5-251111. This is because lithium metal is short-circuited to the negative electrode carbonaceous material, placed in the battery case, and the non-aqueous electrolyte is injected into the case to form an internal space between the lithium metal and the negative electrode. This may cause a short circuit and an electrochemical reaction to cause the carbonaceous material to be doped with lithium.

FIGS. 1 to 4 show application examples of this method in the case of an electrode wound type (spiral type) lithium secondary battery as an example. FIG. 1 to FIG. 4 are views showing an embodiment of the present invention. That is, as shown in FIG. 1, during the spot welding of the negative electrode lead plate 5 during the assembling process, the U-shaped nickel wire 10 around which the lithium foil 9 is wound is spot-welded together to short-circuit the negative electrode 2. In addition, as shown in FIG.
A lithium foil 9 is wound around the outer periphery of the substrate in advance. Further, as shown in FIG. 3, 0.13 g of lithium foil 9 is attached to the inner side surface of the bottomed cylindrical battery case 6 excluding the bottom, and the surface is covered with a polypropylene (PP) separator 3.
As shown in FIG. 4, a 0.13 g donut-shaped lithium foil 9 is formed on the inner bottom of a bottomed cylindrical battery case 6.
And a PP insulating plate 6a is disposed thereon. In any of the embodiments shown in FIGS. 1 to 4, by applying the above method and injecting a non-aqueous electrolyte into the battery case, the lithium metal and the negative electrode are electrochemically short-circuited and carbon The porous material is doped with lithium.

According to this method, the short-circuited lithium metal is dissolved by a chemical reaction after the injection of the non-aqueous electrolyte and is sequentially doped into the carbonaceous material constituting the negative electrode active material. Diffusion until homogeneously dispersed. Then, in order to cause this reaction, it is only necessary to add a step of arranging lithium metal in a short-circuit state on the negative electrode side in an amount equivalent to the amount compensated for at the time of dedoping during the assembling step. A complicated doping step is not required, and there is no increase in equipment cost for this, and an inexpensive and high-quality lithium secondary battery can be provided.

[0013]

However, when this method is applied, the following problems appear.

(1) When a non-aqueous electrolyte is injected into a battery case, gas is generated on the surface of the lithium metal accommodated in the initial stage of the injection, and the electrolyte deteriorates and a part of the lithium metal is deteriorated. Discolors and falls off.

(2) It takes about 6 to 7 days for all the lithium metal contained in the battery case to be dissolved and doped into the negative electrode carbonaceous material.

The cause of the problem (1) is that the contact area between the lithium metal electrolyte contained in the battery case and the electrolyte of the carbonaceous material negative electrode is extremely small. For this reason, the rate at which lithium metal dissolves cannot catch up with the rate at which the entire carbonaceous material negative electrode absorbs lithium. In order to avoid this problem, it is necessary to appropriately control the injection rate so as to gradually increase the contact area between the negative electrode and the electrolyte, which is time-consuming in the manufacturing process, which is a problem.

The reason for the problem (2) is that the potential at which the negative electrode carbonaceous material stores and releases lithium becomes very close to the lithium metal potential according to the amount of lithium stored in the carbonaceous material. In other words, the driving force for the short-circuit reaction between the lithium metal accommodated in the battery case and the negative electrode carbonaceous material proceeds is the difference between the potential at which the negative electrode carbonaceous material absorbs and releases lithium and the lithium metal potential. The reaction speed of this short-circuit reaction becomes slow with time, and there is a disadvantage that the manufactured battery cannot be used immediately.

The present invention solves the above problems.
The purpose is to quickly dope lithium into the carbonaceous material constituting the negative electrode active material after battery assembly without lowering the energy density and without adding a doping process, so that the battery can be used immediately after battery assembly. It is an object of the present invention to provide a lithium secondary battery.

[0019]

To achieve the above object, a lithium secondary battery of the present invention has a chemical formula of LiMn ₂ O
_In a lithium secondary battery having a positive electrode containing lithium represented by ₄ , a negative electrode made of a carbonaceous material and arranged in a state where lithium metal is short-circuited, and a nonaqueous electrolyte, the nonaqueous electrolyte contains naphthalene. , Phenanthrene, anthracene, or other aromatic metal which forms a complex with a lithium metal at a mixing ratio of 0.05 mol or less.

As a specific configuration of the lithium secondary battery of the present invention, a lithium-containing positive electrode and a negative electrode made of a carbonaceous material are arranged via a separator, and lithium metal is short-circuited to the negative electrode. It is housed in a case and forms a structure that causes an electrochemical reaction between the lithium metal and the negative electrode by injecting a non-aqueous electrolyte into the case. The non-aqueous electrolyte contains lithium and a complex. To form an aromatic hydrocarbon or lithium-aromatic complex of 0.05 mol
1 or less. Here, the reason why they are referred to as an aromatic hydrocarbon or a lithium-aromatic complex is that both of them appear reversibly regardless of whether they are added.

The aromatic hydrocarbon complex (naphthalene, phenanthrene, anthracene, etc.) is used for intercalating an alkali metal such as potassium, sodium, lithium or the like between layers of crystallites of a carbonaceous material in a solvent, Various properties have been found.

In the case of lithium, for example, when powdered lithium metal and graphite are stirred in an organic solvent to which an aromatic hydrocarbon has been added, the aromatic hydrocarbon dissolves the lithium metal and forms a lithium-aromatic substance. Form a group hydrocarbon complex. Lithium is absorbed (intercalated) by the contact of this complex with graphite, a lithium-graphite intercalation compound is formed, and the process of returning to the original aromatic hydrocarbon is repeated, whereby lithium is absorbed in graphite. It is believed that. At this time, the reason why the lithium-aromatic hydrocarbon complex occludes lithium in graphite is that this complex is more noble than the lithium metal potential but is more noble than the lithium-graphite intercalation compound. I have.

As will be described later, if the amount of the aromatic hydrocarbon or lithium-aromatic hydrocarbon complex of the present invention is too small, the effect is small. If too large, the internal resistance of the battery increases, and the discharge cutoff voltage increases. In practice, the continuous discharge time until the temperature reaches 0.001 mol / l to 0.
It is preferable to determine the addition amount in the range of 05 mol / l.

In this case, the positive electrode material is represented by the chemical formula Li
It is limited to a material containing lithium represented by Mn ₂ O ₄ .
Since the positive electrode material is noble with respect to the potential of the lithium-aromatic hydrocarbon complex, it absorbs lithium when in contact with the lithium-aromatic hydrocarbon complex. However, there is no problem because the positive electrode material is reversible even if it stores lithium having a stoichiometric composition or more.

The non-aqueous electrolyte is prepared by appropriately combining an organic solvent and an electrolyte, and any of these organic solvents and electrolytes can be used as long as they are used in this type of battery. For example, examples of the organic solvent include propylene carbonate, ethylene carbonate, 1,2-dimethoxyethane, γ-butyrolactone, tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxolan, 4-methyl-1,3 dioxolan, diethyl ether, sulfolane and the like. It is. As the electrolyte, Li
ClO ₄ , LiAsF ₆ , LiBF ₄ , LiPF ₆ , L
iCF ₃ SO ₃ , LiCl and the like.

According to the above configuration, the lithium metal disposed in a short-circuit state with the negative electrode carbonaceous material is dissolved by the injection of the nonaqueous electrolyte, and the carbonaceous material is doped with lithium and added in advance. Aromatic hydrocarbon or lithium-
It will also be doped from the aromatic hydrocarbon complex. Accordingly, the electrode potential of the carbonaceous material shifts to a lower speed more quickly, so that the oxidative decomposition reaction of the non-aqueous electrolyte does not easily occur.

When a lithium-aromatic hydrocarbon complex is added to a non-aqueous electrolyte, the lithium-aromatic hydrocarbon complex is converted into an aromatic hydrocarbon by doping the negative electrode carbonaceous material with lithium. The aromatic hydrocarbon reacts with the negative electrode carbonaceous material and the lithium metal arranged in a short circuit state to form a lithium-aromatic hydrocarbon complex. The lithium-aromatic hydrocarbon complex is obtained by doping the carbonaceous material with lithium, and is converted again into an aromatic hydrocarbon complex. By repeating the above-described process as described above, doping of the carbonaceous material with lithium is promoted, and the battery can be used immediately after the battery is assembled.

Even if only the aromatic hydrocarbon complex is added to the non-aqueous electrolyte, the same circulation is repeated to promote the doping of the carbonaceous material with lithium, and the effect of the present invention can be sufficiently obtained.

[0029]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described mainly with reference to examples.

FIG. 1 shows a first embodiment of an AA type lithium secondary battery of a wound electrode type (spiral type) according to the present invention. This lithium secondary battery basically has a polypropylene (P) between the positive electrode 1 and the negative electrode 2 as in the prior art.
P) A winding element is formed by spirally winding a separator 3 made of a porous film made of a porous film, and a positive electrode lead plate 4 connected to the positive electrode 1 side is connected to an upper part thereof, and a negative electrode 2 side is connected to a lower part thereof. P with the negative electrode lead plate 5
It is housed in the bottomed cylindrical case 6 via the P insulating plate 6a,
The negative electrode lead plate 5 is connected to the center of the inner bottom surface of the bottomed cylindrical case 6 by spot welding, and the positive electrode lead plate 4 is spot welded to the bottom of the positive electrode terminal plate 7 with a safety valve. And the positive electrode terminal plate 7 is fitted into the opening of the case 6 via the sealing gasket 8 and caulked to complete the battery.

The positive electrode 1 is made of LiMn which is a positive electrode active material.
₂ O ₃ , a carbon powder as a conductive agent and an aqueous dispersion of polytetrafluoroethylene (hereinafter referred to as PTFE) were mixed at a weight ratio of 100: 10: 10, and kneaded in a paste with water. After applying the thing on both sides of a 30 μm thick aluminum foil constituting a current collector, the strip was dried, rolled and cut into a predetermined size, and the mixture was mixed at right angles to the longitudinal direction of the strip. A part was scraped off, and the positive electrode lead plate 4 was spot-welded thereto. The ratio of the aqueous dispersion of PTFE in the above mixture ratio is the ratio of the solid content.

LiMn ₂ O _{3 as the} active material is composed of manganese dioxide (MnO ₂ ) and lithium carbonate (LiC
O ₃ ) at a molar ratio of 2: 1 and 750 ° C. in air.
For 7 hours.

The negative electrode 2 is formed by kneading a carbonaceous powder and an aqueous PTFE dispersion in a weight ratio of 100: 3 with water at a ratio of 100: 3, pressing into a nickel expanded metal, drying, and cutting to form a strip. Further, a part is scraped off in a direction perpendicular to the longitudinal direction, and the negative electrode lead plate 5 is spot-welded thereto. In addition, the ratio of the aqueous dispersion of PTFE is the ratio of the solid content as described above,
The weight of the carbonaceous powder of the negative electrode was 3.5 g.

When the negative electrode is charged and discharged at a constant current of 1 mA / cm ^{2 with} a current density of 1 mA / cm ² using lithium metal as a counter electrode, the doping amount of lithium in the first cycle is:
800 mAh up to a voltage between both electrodes of 0.01 V, and the dedoping amount is 500 mAh.

The non-aqueous electrolyte is lithium perchlorate (L
iClO ₄ ) dissolved in a mixed solvent of propylene carbonate and 1,2-dimethoxyethane at a ratio of 1 mol / l was used.

During the assembly process, as shown in FIG.
At the time of spot welding of the negative electrode lead plate 5, a U-shaped nickel wire 1 to which 0.13 g of foamed lithium metal 9 has been crimped
0 is short-circuited to the negative electrode 2 by spot welding together, and then the non-aqueous electrolyte is injected.

The electrolyte solution contains 0 mol, 0.001 mol, and 0.005 mol of an aromatic hydrocarbon, respectively.
mol, 0.01mol, 0.05mol, 0.1mo
1 at various concentrations to complete a prototype battery.

Focusing on the lithium-aromatic hydrocarbon complex instead of the above-mentioned aromatic hydrocarbon, the lithium-aromatic hydrocarbon complex is also similarly 0.001 mol and 0.1 mol based on the electrolytic solution, respectively. 005 mol, 0.
A trial battery was completed by adding various concentrations of 01 mol, 0.05 mol, and 0.1 mol, and the result is the same as that when the aromatic hydrocarbon was added. Therefore,
The case where an aromatic hydrocarbon is added and the case where a lithium-aromatic hydrocarbon complex is added will be described equivalently.

[Experiment 1] Lithium-aromatic hydrocarbon complex or aromatic hydrocarbon was added to a non-aqueous electrolyte at 0 mo, respectively.
1, 0.001 mol, 0.005 mol, 0.01 m
ol, 0.05 mol, and 0.1 mol of the batteries added at various concentrations, after assembling these batteries, the upper limit voltage is 4.
At 2 V and a lower limit voltage of 3.0 V, charge and discharge were performed for 20 cycles at a constant current of 0.17 A, and the charge capacity at the first cycle and the discharge capacity at the 20th cycle were measured. The result is shown in FIG. In FIG. 5, a black triangle indicates the charge capacity (Ah) at the first cycle, and a black circle indicates the discharge capacity (Ah) at the 20th cycle.
h). The difference between the charge capacity at the first cycle and the discharge capacity at the 20th cycle (the level difference between the black triangles and the black circles in the figure) indicates the rate of capacity deterioration. The battery in which the amount of the aromatic hydrocarbon or the lithium-aromatic hydrocarbon complex added to the nonaqueous electrolyte was 0 mol, that is, the battery without the addition, was left for 140 hours after assembly, and then started charging and discharging.

According to the characteristics shown in FIG. 5, the lithium-aromatic hydrocarbon complex or the aromatic
mol, 0.005 mol, 0.01 mol, 0.05
It can be seen that when added in various concentrations of 0.1 mol and 0.1 mol, a lithium secondary battery having a larger capacity than in the case of no addition can be obtained. Further, the amount of addition is 0.001 mol to 0.1 mol.
Up to less than 01 mol, almost no capacity deterioration was observed,
When the amount becomes 0.01 mol or more, deterioration of the capacity starts to be recognized, and when the amount is 0.1 mol, the discharge capacity (Ah) at the 20th cycle becomes almost the same as in the case where no addition is made. Accordingly, the addition amount of the lithium-aromatic hydrocarbon complex or the aromatic hydrocarbon is 0.01 mol, which is a range in which the discharge capacity (Ah) at the 20th cycle does not fall below the value in the case of no addition.
It can be seen that it is better to keep the value at less than 0.05 mol, preferably at a value of 0.05 mol or less at which the rate of deterioration of the capacity is not so large.

Further, in the graph of FIG.
When the addition amount of the aromatic hydrocarbon complex or the aromatic hydrocarbon exceeds the above-mentioned upper limit value of 0.05 mol, the discharge capacity rapidly decreases, but this is because the internal resistance of the battery is reduced by the addition of an excessive amount of the aromatic hydrocarbon. Suggests an increase.

[Experiment 2] Lithium-aromatic hydrocarbon complex or aromatic hydrocarbon was added to the non-aqueous electrolyte at 0.00
1 mol, 0.005 mol, 0.01 mol, 0.0
Regarding the batteries added at various concentrations of 5 mol and 0.1 mol, during the battery assembling process, the presence or absence of gas generation at the time of injection was confirmed. Table 1 shows the results.

[0043]

[Table 1]

As shown in Table 1, when a lithium-aromatic hydrocarbon complex or an aromatic hydrocarbon was added to the non-aqueous electrolyte, the addition amount was 0.001 mol to 0.05 mol.
Within the range of 1 (Examples 1 to 4), gas generation during injection, that is, decomposition of the electrolytic solution was not confirmed. This is because the generation of gas is recognized in the battery with the added amount of 0 mol shown in the left side of Table 1 as a comparison, that is, the conventional battery not added, which causes inconveniences such as swelling of the battery and deterioration of the electrolyte. And in contrast.

[Experiment 3] A lithium-aromatic hydrocarbon complex or an aromatic hydrocarbon was added to a non-aqueous electrolyte at 0.00
1 mol, 0.005 mol, 0.01 mol, 0.0
Regarding the batteries added at various concentrations of 5 mol and 0.1 mol, these batteries were brought up to 4.05 V immediately after assembly.
The battery was charged at a constant current of 17 A and left for 15 minutes, and then the voltage (voltage a (V)) of the battery was measured. Furthermore, after leaving this battery for 120 hours, the voltage (voltage b (V))
Was measured, and the measured values shown in Table 2 were obtained.

[0046]

[Table 2]

In Table 2, the addition concentration of the cobalt complex or the lithium-cobalt complex was 0.005 mol /
In the case of 1 or less, the voltage b value after leaving for 120 hours was higher than the voltage a value after leaving for 15 minutes. It is considered that this is because even after the charging process, all the lithium metal arranged in a short-circuit state with the negative electrode could not be dissolved and remained, and this short-circuit reaction continued.

The above is the embodiment shown in FIG. 1, that is, when spot welding the negative electrode lead plate 5 during the assembling process,
Although the U-shaped nickel wire 10 to which 0.13 g of the foamed lithium metal 9 has been crimped is spot-welded to short-circuit the negative electrode 2, the present invention is not limited to this. That is, as shown in FIG.
And a 0.13 g lithium foil 9 is stuck on the inner side surface of the bottomed cylindrical battery case 6 excluding the bottom, as shown in FIG. The present invention can be applied even when the surface is covered with a polypropylene separator 3. Also, as shown in FIG. 4, 0.13 g is attached to the inner bottom of the bottomed cylindrical battery case 6.
The present invention can also be applied to a case in which a donut-shaped lithium foil 9 is attached and a PP insulating plate 6a is provided thereon. In this case, the negative electrode lead plate 5 is disposed between the PP insulating plate 6a and the donut-shaped lithium foil 9,
Spot welding is carried out at the center of the inner bottom of the battery case 6, which is the center opening of the lithium foil 9.

Also in these embodiments, by adding an aromatic hydrocarbon or a lithium-aromatic hydrocarbon complex to the non-aqueous electrolyte, lithium ions corresponding to the loss capacity of the negative carbonaceous material are removed from the lithium ions of the positive electrode. It is possible to dope without doping, and to obtain an advantage that a lithium secondary battery having a larger capacity can be obtained as compared with one without doping.

[0050]

As described above, according to the present invention, a positive electrode containing lithium represented by the chemical formula LiMn ₂ O ₄ ,
In a lithium secondary battery including a negative electrode made of a carbonaceous material and arranged in a state where lithium metal is short-circuited and a non-aqueous electrolyte, an aromatic hydrocarbon that forms a complex with lithium metal is added to the non-aqueous electrolyte. Therefore, the injection of the non-aqueous electrolyte solution dissolves the lithium metal disposed in a short-circuit state with the negative carbonaceous material, not only doping the carbonaceous material with lithium, but also adding an aromatic hydrocarbon or a previously added aromatic hydrocarbon. It will also be doped from a lithium-aromatic hydrocarbon complex. Accordingly, the electrode potential of the carbonaceous material shifts to a lower speed more quickly, so that the oxidative decomposition reaction of the non-aqueous electrolyte does not easily occur.

Therefore, when the non-aqueous electrolyte is injected into the battery case, the inconvenience of generating gas on the surface of the lithium metal accommodated at the beginning of the injection can be eliminated, and the deterioration of the electrolyte can be prevented. In addition, from 6 to 10 until all the lithium metal contained in the battery case is dissolved and doped into the negative electrode carbonaceous material.
It is possible to obtain a lithium secondary battery that can be used immediately after assembling the battery without having to wait as long as seven days.

Further, in the present invention, by adding an aromatic hydrocarbon, lithium ions corresponding to the loss capacity of the negative electrode carbonaceous material can be doped without dedoping lithium ions of the positive electrode. Thus, a lithium secondary battery having a larger capacity can be obtained as compared with the case where no lithium secondary battery is added. Furthermore, this aromatic hydrocarbon is 0.05 mol
Since it was added in the following mixing ratio, the continuous discharge time until the discharge end voltage was reached can be lengthened.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a lithium secondary battery according to one embodiment of the present invention.

FIG. 2 is a cross-sectional view illustrating a lithium secondary battery according to another embodiment of the present invention.

FIG. 3 is a sectional view showing a lithium secondary battery according to another embodiment of the present invention.

FIG. 4 is a sectional view showing a lithium secondary battery according to still another embodiment of the present invention.

FIG. 5 is a diagram showing the relationship between the amount of aromatic hydrocarbon or lithium-aromatic hydrocarbon complex added and the battery capacity.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 positive electrode 2 negative electrode 3 separator 4 positive electrode lead plate 5 negative electrode lead plate 6 case 7 positive terminal plate 8 sealing gasket 9 lithium metal (lithium foil) 10 nickel wire

Claims (1)

[Claims] 1. A lithium secondary battery comprising a positive electrode containing lithium represented by the chemical formula LiMn ₂ O ₄ , a negative electrode made of a carbonaceous material and having a lithium metal short-circuited, and a non-aqueous electrolyte. And a non-aqueous electrolyte containing an aromatic hydrocarbon which forms a complex with a lithium metal such as naphthalene, phenanthrene or anthracene in a mixing ratio of 0.05 mol or less.