JP2002231309A - Lithium secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lithium secondary battery of high charging/discharging cycle characteristics by retarding the reaction of a negative electrode with a nonaqueous electrolyte in the charging/discharging of the lithium secondary battery having a positive electrode, the negative electrode, and the nonaqueous electrolyte prepared by dissolving a solute in a nonaqueous solvent. SOLUTION: In the lithium secondary battery equipped with the positive electrode 1, the negative electrode 2, and the nonaqueous electrolyte prepared by dissolving the solute in the nonaqueous solvent; and a negative electrode material containing aluminum is used in the negative electrode, and at least one compound selected from between fluorinated phosphate and fluorinated phosphite is added to the nonaqueous solvent.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lithium secondary battery comprising a positive electrode, a negative electrode, and a non-aqueous electrolyte in which a solute is dissolved in a non-aqueous solvent. The present invention relates to a lithium secondary battery which is selected and improved in a non-aqueous electrolyte and has improved charge / discharge cycle characteristics.

[0002]

2. Description of the Related Art In recent years, as a new battery with high output and high energy density, a high electromotive force lithium secondary battery using a non-aqueous electrolyte in which a solute is dissolved in a non-aqueous solvent and utilizing oxidation and reduction of lithium. Has come to be used.

In such a lithium secondary battery, a carbon material capable of inserting and extracting lithium, a metallic lithium,
An alloy of lithium and a metal such as aluminum, lead, bismuth, tin, and indium capable of inserting and extracting lithium has been used.

Here, in such a lithium secondary battery, when metallic lithium is used for the negative electrode, dendrites precipitate during charging, and when charging and discharging are repeatedly performed, the dendrites grow, thereby breaking the separator. Thus, there has been a problem that charging and discharging cannot be performed.

On the other hand, when an alloy of lithium and a metal capable of storing and releasing lithium, such as a lithium-aluminum alloy, is used for the negative electrode, lithium is electrochemically stored and released, so that dendrites do not precipitate. , Can be repeatedly charged and discharged.

However, even when the above-described lithium alloy is used for the negative electrode, when the lithium secondary battery is charged and discharged, the lithium alloy used for the negative electrode expands and contracts, and the charge and discharge are repeatedly performed. However, there has been a problem that the lithium alloy gradually becomes finer and sufficient charge / discharge cycle characteristics cannot be obtained.

For this reason, in recent years, for example, as disclosed in JP-A-9-320634, a lithium-aluminum-manganese alloy in which lithium is occluded in an aluminum-manganese alloy is used as a negative electrode of a lithium secondary battery. In addition, there has been proposed a device that suppresses the occurrence of fine powder when charging and discharging are repeatedly performed as described above to improve the charge and discharge cycle characteristics.

However, even when the lithium-aluminum-manganese alloy in which lithium is occluded in the aluminum-manganese alloy is used for the negative electrode, the negative electrode reacts with the non-aqueous electrolyte during charging and discharging, and the battery is charged. Discharge cycle characteristics have deteriorated. In particular, in recent years, the life of equipment has been prolonged, and lithium secondary batteries having more excellent charge / discharge cycle characteristics have been demanded.

[0009]

SUMMARY OF THE INVENTION The present invention provides a positive electrode,
It is an object of the present invention to solve the above-described problem in a lithium secondary battery including a negative electrode and a nonaqueous electrolyte in which a solute is dissolved in a nonaqueous solvent. It is an object of the present invention to suppress the reaction with a liquid and to obtain a lithium secondary battery having excellent charge / discharge cycle characteristics.

[0010]

According to the present invention, a lithium secondary battery comprising a positive electrode, a negative electrode, and a non-aqueous electrolyte in which a solute is dissolved in a non-aqueous solvent is provided in order to solve the above-mentioned problems. In the battery, while using a negative electrode material containing aluminum for the negative electrode, for the above non-aqueous solvent,
At least one selected from a fluorinated phosphate ester and a fluorinated phosphite ester is added.

Here, as in the lithium secondary battery of the present invention, a negative electrode material containing aluminum is used for the negative electrode, and a phosphate ester fluorinated and a fluorinated phosphite ester in a non-aqueous solvent are used. When adding at least one selected from the group consisting of, the negative electrode material containing aluminum reacts with at least one selected from fluorinated phosphates and fluorinated phosphites added to the non-aqueous solvent. As a result, an ion-conductive film is formed on the surface of the negative electrode material containing aluminum. The coating suppresses the reaction between the negative electrode and the non-aqueous electrolyte during charge and discharge, and improves the charge and discharge cycle characteristics of the lithium secondary battery.

As the negative electrode material containing aluminum used for the negative electrode, a lithium-aluminum alloy in which lithium is occluded in aluminum or an alloy in which lithium is occluded in an alloy of aluminum and another metal can be used. In particular, when a lithium-aluminum-manganese alloy in which lithium is occluded in an aluminum-manganese alloy is used, a film having excellent ion conductivity can be appropriately formed on the surface of the negative electrode material, and further excellent chargeability can be obtained. Discharge cycle characteristics can be obtained.

Further, the lithium-aluminum alloy obtained by absorbing lithium in the aluminum-manganese alloy is used.
In using a manganese alloy for the negative electrode, if the proportion of manganese in this alloy is low, a sufficient coating will not be formed, while if the proportion of manganese is too high, the coating will be too thick, and the charge / discharge reaction will not easily occur. Therefore, the ratio of manganese to the total amount of aluminum and manganese is preferably in the range of 0.1 to 10% by weight.

In addition, in adding at least one selected from a fluorinated phosphate ester and a fluorinated phosphite ester to a non-aqueous solvent, the fluorinated phosphate ester and the fluorinated phosphorus phosphite are added. If the addition amount of the acid ester is small, a sufficient film is not formed, while if the addition amount is too large, the ionic conductivity in the non-aqueous electrolyte is reduced, and the formed film is too thick, Since the charge / discharge reaction is less likely to occur, the fluorinated phosphate and the fluorinated phosphite in the entire solvent to which the fluorinated phosphate and the fluorinated phosphite are added Is preferably in the range of 0.1 to 20% by volume.

Here, there are many fluorinated phosphates and fluorinated phosphites to be added to the non-aqueous solvent, but they improve the charge / discharge cycle characteristics of the lithium secondary battery. To do so, tri (trifluoromethyl) phosphate, tri (pentafluoroethyl) phosphate and tri (trifluoroethyl) phosphate can be used as fluorinated phosphates as fluorinated phosphites It is preferable to use di (trifluoromethyl) phosphite and tri (trifluoromethyl) phosphite.

In the lithium secondary battery of the present invention, the positive electrode material used for the positive electrode is not particularly limited, and known positive electrode materials generally used conventionally can be used. Vanadium oxide, niobium oxide, lithium cobaltate, lithium nickelate, spinel manganese, and the like can be used. When, is used, more excellent charge / discharge cycle characteristics can be obtained.

The boron-containing lithium-manganese composite oxide has an atomic ratio of boron to manganese Mn (B / Mn) in the range of 0.01 to 0.20 and an average valence of manganese of 3.80. Use the above.

In order to obtain the above-mentioned boron-containing lithium-manganese composite oxide, for example, a boron compound, a lithium compound and a manganese compound are prepared by mixing a boron B: lithium Li: manganese Mn with an atomic ratio of 0.0
The mixture is mixed at a ratio of 1 to 0.20: 0.1 to 2.0: 1, and the mixture is heat-treated in air.

In the heat treatment of the mixture as described above, if the heat treatment temperature is lower than 150 ° C., the reaction does not proceed sufficiently, and the water in the manganese dioxide MnO ₂ cannot be sufficiently removed. On the other hand, if the heat treatment temperature exceeds 430 ° C., the manganese dioxide MnO ₂ is decomposed, and the average valence of manganese becomes smaller than 3.80. Since the boron-containing lithium-manganese composite oxide is decomposed due to an imbalance in the electronic state and is easily eluted into the non-aqueous electrolyte, the temperature for the heat treatment is set to 150 ° C.
The temperature is in the range of 430 ° C, preferably in the range of 250 to 430 ° C, more preferably in the range of 300 to 430 ° C.

Examples of the boron compound include boron oxide B ₂ O ₃ , boric acid H ₃ BO ₃ , metaborate HBO ₂ , lithium metaborate LiBO ₂ , and lithium tetraborate Li ₂ B ₄ O ₇ . Examples of the lithium compound include lithium hydroxide LiOH, lithium carbonate Li ₂ CO ₃ , lithium oxide L
i ₂ O, lithium nitrate LiNO ₃ can be used,
As the manganese compound, for example, manganese dioxide MnO ₂ or manganese oxyhydroxide MnOOH can be used.

In the lithium secondary battery of the present invention, the solute used for the non-aqueous electrolyte is not particularly limited, and a known solute generally used conventionally can be used. For example, lithium trifluoromethanesulfone Acid imide, lithium pentafluoroethanesulfonic acid imide, lithium trifluoromethanesulfonic acid methide, lithium trifluoromethanesulfonic acid, or the like can be used.

The non-aqueous solvent used in the above-mentioned non-aqueous electrolyte is not particularly limited, and any known non-aqueous solvent conventionally used can be used. In particular, ethylene carbonate, propylene carbonate, butylene Carbonate, vinylene carbonate, at least one non-aqueous solvent selected from the group consisting of γ-butyrolactone and sulfolane, and 1,2-dimethoxyethane;
1,2-diethoxyethane, 1,2-ethoxymethoxyethane, tetrahydrofuran, 1,3-dioxolan,
When a mixed solvent containing at least one non-aqueous solvent selected from the group consisting of dimethyl carbonate, diethyl carbonate and methyl ethyl carbonate is used, the ionic conductivity of the non-aqueous electrolyte is increased, and the aluminum used for the negative electrode is used. An excellent ion-conductive film is formed on the negative electrode material containing, and the charge-discharge cycle characteristics are improved.

[0023]

EXAMPLES Hereinafter, the lithium secondary battery according to the present invention will be specifically described with reference to examples, and it will be compared with the lithium secondary battery according to this example that the charge / discharge cycle characteristics are improved. Clarify with an example. The lithium secondary battery according to the present invention is not limited to those shown in the following examples, but can be appropriately modified and implemented without changing the gist of the invention.

(Example 1) In this example, a positive electrode and a negative electrode prepared as described below were used, and a non-aqueous electrolyte prepared as described below was used. A flat coin-shaped lithium secondary battery having a thickness of 24 mm and a thickness of 3 mm was produced.

[Preparation of Positive Electrode] In preparing a positive electrode, lithium hydroxide LiOH, boron oxide B ₂ O _3, and manganese dioxide MnO ₂ were mixed at an atomic ratio of Li: B: Mn of 0.53: 0.06. : 1.00, and the mixture was heat-treated in air at 375 ° C for 20 hours, and then pulverized to obtain a boron-containing lithium-manganese composite oxide powder.

When the boron-containing lithium-manganese composite oxide was measured by X-ray diffraction, the X-ray diffraction pattern showed that the peak of Li ₂ MnO ₃ shifted slightly from the original peak position to the lower angle side. Only the MnO ₂ peak was observed.

The average valence of manganese in the boron-containing lithium-manganese composite oxide was measured and found to be 3.80.

Here, in order to determine the average valence of manganese in the boron-containing lithium-manganese composite oxide, a solution is prepared by dissolving the boron-containing lithium-manganese composite oxide in hydrochloric acid. After adding the aqueous solution of ferrous ammonium, excess ammonium ferrous sulfate is titrated with an aqueous solution of potassium permanganate to determine the amount of available oxygen in the solution, and the amount of manganese in the solution is determined by atomic absorption spectrometry. The average valence of manganese was calculated from the obtained amount of available oxygen and the amount of manganese thus obtained.

[0029] Incidentally, the average valence of manganese is less than 4, the lithium is believed to be due to the solid solution in the MnO _2, and also the same for the peak of the MnO ₂ in the X-ray diffraction pattern is shifted to the lower angle side This is probably the reason.

Then, the powder of the boron-containing lithium-manganese composite oxide obtained as described above, the powder of carbon black as the conductive agent, and the powder of the fluororesin as the binder were mixed in a ratio of 85: 10: 5. To obtain a positive electrode mixture. Next, the positive electrode mixture was molded into a disk shape, and then dried at 250 ° C. for 2 hours in a vacuum to prepare a positive electrode.

[Preparation of Negative Electrode] In preparing the negative electrode, lithium-manganese alloy in which lithium was electrochemically occluded in an aluminum-manganese alloy in which the ratio of manganese to the total amount of aluminum and manganese was 1% by weight was used. An aluminum-manganese alloy (Li-AL-Mn alloy) was punched out in a disk shape to produce a negative electrode.

[Preparation of Non-Aqueous Electrolyte] In preparing a non-aqueous electrolyte, a fluorinated non-aqueous solvent was prepared by mixing propylene carbonate (PC) and 1,2-dimethoxyethane (DME). Tri (trifluoromethyl) phosphate O = P (OCF ₃ ) ₃ was added as a phosphate ester.

Then, the above-mentioned propylene carbonate (PC), 1,2-dimethoxyethane (DME),
Tri (trifluoromethyl) phosphate O = P (OCF ₃ )
₃ at a volume ratio of 47.5: 47.5: 5, and the volume ratio of tri (trifluoromethyl) phosphate is 5% by volume.
The solvent became, and lithium trifluoromethanesulfonate imide LiN the (CF ₃ SO _{2) 2} was dissolved to a concentration of 1 mole / liter as a solute to prepare a nonaqueous electrolyte.

[Preparation of Battery] In preparing a battery, as shown in FIG. 1, the positive electrode 1 was attached to a positive electrode current collector 5 made of a stainless steel plate (SUS316), while the negative electrode 2 was attached to the positive electrode current collector 5. Stainless steel plate (SUS30
4) Attached to the negative electrode current collector 6 constituted in 4), the non-aqueous electrolytic solution is impregnated into the separator 3 made of a polypropylene microporous film, and the separator 3 is placed between the positive electrode 1 and the negative electrode 2. These are interposed and accommodated in a battery case 4 formed of a positive electrode can 4a and a negative electrode can 4b, and the positive electrode 1 is connected to the positive electrode can 4a via a positive electrode current collector 5,
The negative electrode 2 is connected to the negative electrode can 4b via the negative electrode current collector 6,
The positive electrode can 4a and the negative electrode can 4b were electrically insulated by an insulating packing 7 made of polypropylene to obtain a coin-shaped lithium secondary battery. The discharge capacity of this lithium secondary battery was about 90 mAh, and the internal resistance of the battery before charging and discharging was about 10Ω.

Example 2 In Example 2, a fluorinated phosphate ester was used instead of the above-mentioned tri (trifluoromethyl) phosphate in the preparation of the non-aqueous electrolyte in Example 1 above. A certain tri (pentafluoroethyl) phosphate O = P (OCF ₂ CF ₃ ) ₃ was used, and the other conditions were the same as in Example 1 above.
A lithium secondary battery of Example 2 was produced.

Example 3 In Example 3, a fluorinated phosphate ester was used instead of the above-mentioned tri (trifluoromethyl) phosphate in the preparation of the non-aqueous electrolyte in Example 1 described above. So that certain tri (trifluoroethyl) phosphate O = P (OCH ₂ CF ₃ ) ₃ is used,
Otherwise, in the same manner as in Example 1 described above, a lithium secondary battery of Example 3 was manufactured.

Example 4 In Example 4, a fluorinated phosphite was used instead of the above-mentioned tri (trifluoromethyl) phosphate in the preparation of the non-aqueous electrolyte in Example 1 described above. The lithium secondary battery of Example 4 was manufactured in the same manner as in Example 1 except that di (trifluoromethyl) O = PH (OCF ₃ ) ₂ was used. did.

Example 5 In Example 5, a fluorinated phosphite was used instead of the above-mentioned tri (trifluoromethyl) phosphate in the preparation of the non-aqueous electrolyte in Example 1 above. Then, a lithium secondary battery of Example 5 was manufactured in the same manner as in Example 1 except that tri (trifluoromethyl) P (OCF ₃ ) ₃ was used.

Comparative Example 1 In Comparative Example 1, the propylene carbonate (PC) and 1,2-dimethoxyethane (DME) were mixed in a volume of 50:50 in the preparation of the non-aqueous electrolyte in Example 1 described above. The lithium secondary battery of Comparative Example 1 was fabricated in the same manner as in Example 1 except that tri (trifluoromethyl) phosphate was not added to the non-aqueous solvent mixed at a specific ratio. did.

Comparative Example 2 In Comparative Example 2, in the preparation of the non-aqueous electrolyte in Example 1 described above, instead of the above-mentioned tri (trifluoromethyl) phosphate, a non-fluorinated phosphate ester was used. Trimethyl phosphate O =
A lithium secondary battery of Comparative Example 2 was fabricated in the same manner as in Example 1 except that P (OCH ₃ ) ₃ was used.

Comparative Example 3 In Comparative Example 3, in the preparation of the non-aqueous electrolyte solution in Example 1 described above, instead of the above tri (trifluoromethyl) phosphate, non-fluorinated phosphorous acid was used. Dimethyl phosphite O which is an ester
= PH (OCH ₃ ) ₂ , otherwise,
A lithium secondary battery of Comparative Example 3 was manufactured in the same manner as in Example 1 described above.

Comparative Example 4 In Comparative Example 4, in the preparation of the non-aqueous electrolyte solution in Example 1 described above, instead of the above tri (trifluoromethyl) phosphate, non-fluorinated phosphorous acid was used. A lithium secondary battery of Comparative Example 4 was produced in the same manner as in Example 1 except that trimethyl phosphite P (OCH ₃ ) ₃ as an ester was used.

Next, Example 1 manufactured as described above was used.
-5 and each of the lithium secondary batteries of Comparative Examples 1-4,
After charging to a charge end voltage of 3.2 V with a charge current of 10 mA, a discharge end voltage of 2.
Discharge to 0 V, and the discharge capacity is 50% of the initial discharge capacity.
%, And the number of cycles until the percentage becomes less than% was obtained. The result is shown in Table 1 below.

[0044]

[Table 1]

As is apparent from the results, a lithium-aluminum-manganese alloy which is a negative electrode material containing aluminum is used for the negative electrode, and a fluorinated phosphate ester or a fluorinated fluorinated solvent is used in a non-aqueous solvent in a non-aqueous electrolyte. The lithium secondary batteries of Examples 1 to 5 to which the phosphite was added were the lithium secondary batteries of Comparative Example 1 in which nothing was added to the non-aqueous solvent in the non-aqueous electrolyte, or fluorinated. The charge / discharge cycle characteristics are significantly improved as compared with the respective lithium secondary batteries of Comparative Examples 2 to 4 in which a phosphoric acid ester or a phosphite is not added.
In the lithium secondary batteries of Examples 1 to 3 using the fluorinated phosphate, the charge / discharge cycle characteristics were further improved.

(Examples A1 to A5) In Examples A1 to A5, only the amount of manganese in the aluminum-manganese alloy used for the negative electrode in the preparation of the negative electrode in Example 1 was changed.

Here, in Example A1, a lithium-aluminum alloy in which lithium was electrochemically occluded in aluminum containing no manganese was used. In Example A2, the ratio of manganese in the aluminum-manganese alloy was 0.1%.
In Example A3, a lithium-aluminum-manganese alloy in which lithium was electrochemically occluded in an aluminum-manganese alloy in which the content of manganese in the aluminum-manganese alloy was 0.5% by weight was 0.5% by weight. A lithium-aluminum-manganese alloy in which lithium is electrochemically occluded in a manganese alloy,
In Example A4, a lithium-aluminum-manganese alloy in which lithium was electrochemically occluded in an aluminum-manganese alloy in which the proportion of manganese in the aluminum-manganese alloy was 5% by weight was used. In Example A5, an aluminum-manganese alloy was used. The ratio of manganese in the medium is 1
Lithium-aluminum in which lithium is electrochemically occluded from aluminum-manganese alloy of 0% by weight
The lithium secondary batteries of Examples A1 to A5 were manufactured in the same manner as in Example 1 except that a manganese alloy was used.

Next, the embodiment A manufactured as described above was used.
The lithium secondary batteries 1 to A5 were also charged to a charge end voltage of 3.2 V at a charge current of 10 mA and then discharged to a discharge end voltage of 2.0 V at a discharge current of 10 mA in the same manner as in Example 1 above. The number of cycles until the discharge capacity became 50% or less of the initial discharge capacity was determined. The results are shown in Table 2 below.

[0049]

[Table 2]

As a result, Examples 1, A2 to A, in which a lithium-aluminum-manganese alloy in which lithium was electrochemically occluded in an aluminum-manganese alloy was used for the negative electrode.
Each of the lithium secondary batteries of No. 5 has improved charge / discharge cycle characteristics as compared with the lithium secondary battery of Example A1 using a lithium-aluminum alloy in which lithium is electrochemically occluded in aluminum as the negative electrode, In particular, the ratio of manganese in the aluminum-manganese alloy is 0.5 to 5
In the lithium secondary batteries of Examples 1, A3 and A4 in the range of weight%, the charge / discharge cycle characteristics were further improved.

(Examples B1 to B5) In Examples B1 to B5, propylene carbonate (PC) and 1,2-dimethoxyethane (DME) were mixed in the preparation of the non-aqueous electrolyte in Example 1 described above. Tri (trifluoromethyl) phosphate O = P to be added to the nonaqueous solvent
(OCF ₃ ) Only the ratio of ₃ was changed.

Here, in Example B1, the volume ratio of PC: DME: tri (trifluoromethyl) phosphate was 49.9.
5: 49.95: 0.1, and in Example B2, PC: DM
E: The volume ratio of tri (trifluoromethyl) phosphate is 4
9.75: 49.75: 0.5, and in Example B3, P
The volume ratio of C: DME: tri (trifluoromethyl) phosphate was 49.5: 49.5: 1. In Example B4, PC:
The volume ratio of DME: tri (trifluoromethyl) phosphate was 45:45:10, and in Example B5, the volume ratio of PC: DME: tri (trifluoromethyl) phosphate was 40: 4.
0:20, and the volume ratio of tri (trifluoromethyl) phosphate in the solvent was 0.1% by volume in Example B1, 0.5% by volume in Example B2, and 1% by volume in Example B3. 10% by volume in Example B4 and 20% in Example B5.
The lithium secondary batteries of Examples B1 to B5 were prepared in the same manner as in Example 1 except that the content was set to volume%.

Next, the embodiment B manufactured as described above was used.
Similarly to the case of Example 1 described above, each of the lithium secondary batteries 1 to B5 was charged to a charging end voltage of 3.2 V at a charging current of 10 mA, and then was discharged to a charging end voltage of 2.0 V at a discharging current of 10 mA. The number of cycles until the discharge capacity became 50% or less of the initial discharge capacity was determined. The results are shown in Table 3 below.

[0054]

[Table 3]

As a result, the ratio of tri (trifluoromethyl) phosphate in the solvent of the non-aqueous electrolyte was 0.5 to 10%.
In each of the lithium secondary batteries of Examples 1 and B2 to B4 in the range of volume%, the lithium secondary battery of Example B1 in which the proportion of tri (trifluoromethyl) phosphate was 0.1% by volume was used. , The ratio of tri (trifluoromethyl) phosphate is 20
The charge / discharge cycle characteristics are improved as compared with the lithium secondary battery of Example B5 in which the volume percentage is reduced to volume%, and particularly, the ratio of tri (trifluoromethyl) phosphate is in the range of 1 to 5 volume%. In the lithium secondary batteries of Examples 1 and B2,
The charge / discharge cycle characteristics were further improved.

In Examples B1 to B5,
Although the case where tri (trifluoromethyl) phosphate was used is shown, the tri (pentafluoroethyl) phosphate, tri (trifluoroethyl) phosphate, and di (trifluoromethyl) phosphate used in Examples 2 to 5 were used. Similar results are obtained when using methyl) and tri (trifluoromethyl) phosphite.

(Examples C1 to C7) In Examples C1 to C7, propylene carbonate (PC) and 1,2-
Dimethoxyethane (DME) and tri (trifluoromethyl) phosphate O = P (OCF ₃ ) ₃ were mixed with 47.5: 4.
Only the type of solute to be dissolved in the solvent mixed at a volume ratio of 7.5: 5 was changed.

Here, in Example C1, lithium pentafluoroethanesulfonic acid imide LiN (C ₂ F ₅ S
O ₂ ) ₂ , LiC (CF ₃ SO ₂ ) ₃ in Example C2, and Li Li (trifluoromethanesulfonate) in Example C3.
CF ₃ SO ₃ , lithium hexafluorophosphate LiPF ₆ in Example C4, lithium tetrafluoroborate LiBF ₄ in Example C5, lithium hexafluoroarsenate LiAsF ₆ in Example C6, and perchlorine in Example C7. Example C1 was carried out in the same manner as in Example 1 except that lithium oxide LiClO ₄ was used.
To C7 were produced.

Next, the embodiment C manufactured as described above was used.
Similarly to the case of Example 1 described above, each of the lithium secondary batteries 1 to C7 was charged to a charging end voltage of 3.2 V at a charging current of 10 mA, and then discharged at a discharging current of 10 mA to 2.0 V at a discharging current of 10 mA. The number of cycles until the discharge capacity became 50% or less of the initial discharge capacity was determined. The results are shown in Table 4 below.

[0060]

[Table 4]

As a result, in each of the lithium secondary batteries of Examples C1 to C7 using any of the above solutes, the charge / discharge cycle characteristics were remarkably higher than those of the lithium secondary batteries of Comparative Examples 1 to 4. In particular, the solute contains lithium trifluoromethanesulfonimide LiN (CF ₃
SO ₂ ) ₂ lithium pentafluoroethanesulfonic acid imide LiN (C ₂ F ₅ SO ₂ ) ₂ , lithium trifluoromethanesulfonic acid methide LiC (CF ₃ SO ₂ ) ₃ ,
Lithium trifluoromethanesulfonate LiCF ₃ SO
_In the lithium secondary batteries of Examples 1 and C1 to C3 using No. ₃ , the charge / discharge cycle characteristics were further improved.

In each of the above embodiments, a mixed solvent of propylene carbonate (PC) and 1,2-dimethoxyethane (DME) was used as the non-aqueous solvent in the non-aqueous electrolyte. Carbonate,
Propylene carbonate, butylene carbonate, vinylene carbonate, at least one non-aqueous solvent selected from the group consisting of γ-butyrolactone and sulfolane, and 1,2-dimethoxyethane, 1,2-diethoxyethane, 1,2-ethoxymethoxy Ethane, tetrahydrofuran, 1,3-dioxolane, dimethyl carbonate, diethyl carbonate, and the same applies when using a mixture obtained by appropriately combining at least one non-aqueous solvent selected from the group consisting of methyl ethyl carbonate. The effect of is obtained.

[0063]

As described in detail above, in the lithium secondary battery of the present invention, a negative electrode material containing aluminum is used for the negative electrode, and phosphorus fluorinated with respect to the non-aqueous solvent in the non-aqueous electrolyte is used. Since at least one selected from an acid ester and a fluorinated phosphite is added, the fluorinated phosphate or fluorinated phosphite added to the non-aqueous solvent and aluminum are added. The reaction with the negative electrode material containing aluminum caused an ion-conductive film to be formed on the surface of the negative electrode material containing aluminum.

Then, the reaction between the negative electrode and the non-aqueous electrolyte during charging / discharging was suppressed by this coating, and a lithium secondary battery having excellent charge / discharge cycle characteristics was obtained.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of a lithium secondary battery produced in an example of the present invention and a comparative example.

[Explanation of symbols]

 1 Positive electrode 2 Negative electrode

Continuation of the front page (72) Inventor Maruo Jinno 2-5-5 Keihanhondori, Moriguchi-shi, Osaka Sanyo Electric Co., Ltd. F term (reference) 5H029 AJ05 AK03 AL11 AM03 AM04 BJ03 BJ16 HJ01 HJ07 5H050 AA07 BA16 CB12 HA01 HA07

Claims (5)

[Claims] 1. A lithium secondary battery comprising a positive electrode, a negative electrode, and a non-aqueous electrolyte in which a solute is dissolved in a non-aqueous solvent, wherein the negative electrode uses aluminum-containing negative electrode material, A lithium secondary battery, wherein at least one selected from a fluorinated phosphate ester and a fluorinated phosphite is added to an aqueous solvent. 2. The lithium secondary battery according to claim 1, wherein an alloy containing aluminum and manganese is used for the negative electrode. 3. The lithium secondary battery according to claim 2, wherein the amount of manganese in the alloy containing aluminum and manganese is in the range of 0.1 to 10% by weight based on the total amount of aluminum and manganese. A lithium secondary battery characterized by the following. 4. The lithium secondary battery according to claim 1, wherein the fluorinated phosphoric acid ester and the fluorinated phosphite are added in the entire solvent. The volume ratio of the fluorinated phosphoric acid ester and the fluorinated phosphite is 0.
A lithium secondary battery in the range of 1 to 20% by volume. 5. The lithium secondary battery according to claim 1, wherein the fluorinated phosphate is tri (trifluoromethyl) phosphate or tri (pentafluorophosphate). Ethyl) and tri (trifluoroethyl) phosphate, and the fluorinated phosphite is di (trifluoromethyl) phosphite or tri (trifluoromethyl) phosphite. And at least one selected from the group consisting of fluoromethyl).