JP2940710B2 - Non-aqueous electrolyte battery - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (A) Industrial Application Field The present invention relates to a positive electrode, a negative electrode using lithium as an active material,
The present invention relates to a non-aqueous electrolyte battery provided with a non-aqueous electrolyte, and more particularly to improvement of a non-aqueous electrolyte.

(B) Conventional technology Non-aqueous electrolyte batteries using lithium as a negative electrode active material have attracted attention because they have a particularly high energy density, and are being actively studied.

By the way, since lithium, which is a negative electrode active material, is very active, it reacts with a solvent constituting an electrolytic solution, and a polymer or a decomposition product thereof may adhere to a surface of a positive electrode or a negative electrode in some cases. Therefore, when the battery is stored for a long period of time, there are problems such as an increase in the internal impedance of the battery and a decrease in storage characteristics, and in the case of a secondary battery, deterioration of cycle characteristics.

Therefore, suppressing the reactivity between the electrolyte and the negative electrode lithium is an important issue in putting this type of battery to practical use.

Conventionally, organic solvents used for the electrolyte of this type of battery include low-viscosity ether solvents such as 1,2-dimethoxyethane (DME), tetrahydrofuran (THF), and 1,3-dioxolane (DOXL), and propylene carbonate. (PC), ethylene carbonate (EC), γ-butyrolactone (γ-
There are cyclic carbonates such as BL) and cyclic lactones, and the like.
It has been proposed to use a derivative obtained by partially substituting an ether solvent, such as -methyl-tetrahydrofuran (2Me-THF) or 4-methyl-1,3-dioxolane (4Me-DOXL). Neither can be said to be fully satisfactory.

(C) Problems to be Solved by the Invention The present invention relates to a primary or secondary non-hydrogen electrolyte battery using lithium as a negative electrode active material, in particular, to suppress the reaction between the negative electrode lithium and the non-aqueous electrolyte and to improve the storage characteristics. It is a first object to improve the above. It is a second object of the secondary battery to improve the charge / discharge cycle characteristics in addition to the storage characteristics.

(D) Means for Solving the Problems In a non-aqueous electrolyte battery including a positive electrode, a negative electrode using lithium as an active material, and a non-aqueous electrolyte, at least one kind of a solvent constituting the non-aqueous electrolyte is used. A 5- or more-membered cyclic lactone having an unsaturated bond in the CC ring is used.

(E) Action In a non-aqueous electrolyte battery using lithium as the negative electrode, it is known that highly active lithium reacts with the electrolyte, and that the polymer or decomposition product adheres as a film to the surface of the positive electrode or the negative electrode. Have been. All of these coatings are inert, have poor ionic conductivity, increase the internal impedance of the battery,
In addition to deteriorating the battery characteristics, it also causes the cycle characteristics of the secondary battery to deteriorate.

However, at least one C-C
When a cyclic lactone having five or more members having an unsaturated ring in the ring is used as a solvent, the problems relating to such an electrolytic solution are greatly improved, an increase in the internal impedance of the battery due to storage or the like is suppressed, and storage characteristics are improved. In addition, it was found that the cycle characteristics were improved in the case of the secondary battery.

Considering the reason, the cyclic lactone having a CC internal unsaturated bond is structurally similar to propylene carbonate, γ-butyrolactone, and the like, and therefore has excellent properties as a solvent. Then, the unsaturated ring in the ring is preferentially coordinated with the active lithium of the negative electrode on the surface thereof to form a very thin film, thereby suppressing the reaction between lithium and the electrolytic solution, It is considered that by having a strong orientation with respect to, lithium ions are solvated and stabilized in the electrolytic solution, and lithium is uniformly deposited on the negative electrode during charging. Also, due to the unsaturated ring in the ring,
It is considered that the solvent itself is less susceptible to reduction by lithium and is stabilized.

Furthermore, when a fluorine-based lithium Lewis acid salt is used as a solute, a small amount of fluorine ions contained in the solute react with lithium to form a hybrid film with the above-described lithium surface film, so that the lithium surface is stable and dense. It is considered that the storage characteristics are further improved by being covered with the protective film.

The 5- or more-membered cyclic lactone having a CC intracyclic unsaturated bond may be used alone as a solvent, or may be used as a mixture with another solvent. The ratio of the solvent to the total solvent may be a mixing ratio of 5 vol% or more.

(F) Examples Hereinafter, examples of the present invention will be described in detail.

Example 1 In this example, a nonaqueous electrolyte primary battery will be described in detail as an example.

FIG. 1 is a cross-sectional view of a flat nonaqueous electrolyte primary battery as one embodiment of the present invention. Reference numeral 1 denotes a negative electrode made of lithium metal, which is pressure-bonded to a negative electrode current collector 3 that is fixed to the inner bottom surface of a negative electrode can 2 made of ferritic stainless steel (SUS430) and having a substantially U-shaped cross section. 4 is a positive electrode, 350 to 430
Using manganese dioxide heat-treated in a temperature range of ° C. as an active material, this manganese dioxide, carbon powder as a conductive agent, and fluororesin powder as a binder were mixed at 85: 10: 5.
And then heat-treated at a temperature of 250 to 350 ° C., which is press-bonded to a positive electrode current collector 6 fixed to the inner bottom surface of the positive electrode can 5. Reference numeral 7 denotes a separator, which is impregnated with an electrolytic solution serving as a framework of the present invention. As the electrolyte, a solution prepared by dissolving 1 mol / mol of lithium trifluoromethanesulfonate as a solute in an equal volume mixed solvent of 2 (5H) -furanone and 1,2-dimethoxyethane was used. Reference numeral 8 denotes an insulating packing made of polypropylene, and the battery dimensions are 20.0 mm in diameter and 2.5 mm in height. This battery was designated as battery (A) of the present invention.

Comparative Example 1 Instead of using 2 (5H) -furanone as the electrolyte,
A battery similar to that of the above example was prepared except that γ-butyrolactone was used. This was designated as Comparative Battery (X).

FIG. 2 shows the initial discharge characteristics of the battery of the present invention (A) and the comparative battery (X), and FIG. 3 shows the discharge characteristics of these batteries after being stored in a 60 ° C. constant temperature bath for 3 months. Each of these discharges was performed by a constant resistance discharge of 300Ω. As is clear from this, it can be seen that the battery of the present invention has a small capacity deterioration after storage and has excellent storage characteristics. Moreover, as a result of measuring the internal impedance of the battery of the present invention (A) before and after storage, as shown in Table 1, it is found that the increase in impedance of the battery of the present invention due to storage is small.

Example 2 In this example, a non-aqueous electrolyte secondary battery will be described as an example.

A battery having a diameter of 24.0 mm and a height of 3.0 mm was produced in the same manner as in Example 1 except that a lithium-aluminum alloy was used for the negative electrode, and a manganese oxide containing lithium in advance for the positive electrode active material was used. This is referred to as a battery (B) of the present invention.

Comparative Example 2 Instead of using 2 (5H) -furanone as the electrolyte,
A battery similar to that of Example 2 was prepared except that γ-butyrolactone was used. Then, this battery is used as a comparative battery (Y)
And

FIG. 4 shows the charge / discharge cycle characteristics of the battery of the present invention (B) and the comparative battery (Y). The charge / discharge conditions are as follows:
A, The charge / discharge time was 4 hours, and the battery that reached 1.5 V within the discharge time was regarded as the life. As apparent from this, it can be seen that the battery of the present invention (B) has an increased cycle life and improved cycle characteristics as compared with the comparative battery (Y).

Embodiment 3 This embodiment will be described in detail with reference to another embodiment of the non-aqueous electrolyte secondary battery.

A battery similar to that of Example 2 except that a solution in which lithium hexafluorophosphate was dissolved at an amount of 1 mol / solute in an equal volume mixed solution of 2 (5H) -furanone and 2-methyl-tetrahydrofuran was used as an electrolytic solution. And this was designated as Battery (C) of the present invention.

Comparative Example 3 A battery similar to that of Example 3 was prepared except that propylene carbonate was used instead of using 2 (5H) -furanone as an electrolytic solution, and a comparative battery (Z) was obtained.

FIG. 5 shows the charge / discharge cycle characteristics of the battery of the present invention (C) and the comparative battery (Z). The charge and discharge conditions are the same as in Example 2. As is clear from this, it can be seen that the battery of the present invention (C) has an increased cycle life and improved cycle characteristics as compared with the comparative battery (Z).

Although the embodiment of the battery of the present invention has been described above, the effect of the present invention is not limited to the above-mentioned 2 (5H) -furanone, but may be a 5- or more-membered cyclic lactone having at least one CC internal unsaturated bond. A similar effect can be obtained, but a 5-membered or 6-membered ring is particularly structurally stable and highly effective.

(G) Effect of the Invention As described above, in a non-aqueous electrolyte battery including a positive electrode, a negative electrode using lithium as an active material, and a non-aqueous electrolyte, the non-aqueous electrolyte has at least a CC inner ring. By using a 5-membered or more cyclic lactone having a saturated bond, the storage characteristics of this type of battery and the charge / discharge cycle characteristics of a secondary battery can be improved, and its industrial value is extremely large. is there.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a flat type non-aqueous electrolyte primary battery which is one embodiment of the battery of the present invention. FIGS. 2 and 3 show discharge characteristics before and after storage of the primary battery. 5 and 5 show the charge / discharge cycle characteristics of the secondary battery, respectively. 1 ... Negative electrode, 2 ... Negative electrode can, 3 ... Negative electrode current collector, 4 ...
Positive electrode, 5: positive electrode can, 6: positive electrode current collector, 7: separator, 8: insulating packing.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Ryuji Oshita 2-18-18 Keihanhondori, Moriguchi-shi, Osaka Sanyo Electric Co., Ltd. (72) Inventor Norihiro Furukawa 2--18 Keihanhondori, Moriguchi-shi, Osaka Sanyo Electric Co., Ltd. (58) Field surveyed (Int.Cl. ⁶ , DB name) H01M 10/40 H01M 6/16

Claims (5)

(57) [Claims] 1. A positive electrode, a negative electrode using lithium as an active material,
A non-aqueous electrolyte battery comprising a non-aqueous electrolyte, wherein a non-aqueous electrolyte is characterized by using a 5- or more-membered cyclic lactone having at least a CC internal unsaturated bond as a solvent for the non-aqueous electrolyte. Electrolyte battery. 2. The method according to claim 1, wherein the cyclic lactone having five or more rings having an unsaturated bond in the CC ring is at least one selected from 2-furanone and derivatives thereof. Water electrolyte battery. 3. The method of claim 2, wherein said 2-furanone and its derivative are 2
4. The non-aqueous electrolyte battery according to claim 3, wherein the battery is (5H) -furanone or 2 (3H) -furanone. 4. The non-aqueous electrolyte battery according to claim 1, wherein at least one kind of fluorine-based lithium Lewis acid salt is used as a solute of the non-aqueous electrolyte. 5. The lithium fluoride Lewis acid salt includes lithium trifluoromethanesulfonate (LiCF ₃ SO ₃ ), lithium hexafluorophosphate (LiPF ₆ ), lithium tetrafluoroborate (LiBF ₄ ), and lithium hexafluoroarsenate. (LiAsF _6), the non-aqueous electrolyte battery according to claim wherein the at least one selected from the group consisting of lithium hexafluoroantimonate (LiSbF _6).