JPS58214279A - Nonaqueous electrolyte for lithium secondary battery - Google Patents

Abstract

PURPOSE:To provide an electrolyte in which charge-discharge performance of a Li electrode is good and Li<+> ion conductivity is high by using inorganic salts as a solute and a mixed solvent of propylene carbonate and 1,2-dimethoxy ethane as a solvent. CONSTITUTION:A solvent having high dielectric constant and increased Li<+> ion dissociation such as propylene carbonate is mixd with a solvent having low viscosity and increased Li<+> ion mobility such as 1,2-dimethoxy ethane as an organic solvent for a lithium secondary battery. A mixing ratio of propylene carbonate dissolving 0.5-2.5 N of a solute and 1,2-dimethoxy ethane dissolving 0.5-2.5 N of a solute is preferably 2:8-7:3 and the most preferably about 5:5 in the volume ratio. When the mixing ratio is less than 2:8, charge-discharge performance become close to that of 1,2-dimethoxy ethane alone. When the mixing ratio is more than 7:3, charge-discharge performance becomes close to that of propylene carbonate alone. In either case, charge-discharge performance is decreased.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a pF+ solution used in lithium secondary batteries.

Batteries using lithium as a negative electrode foil material have been studied as small, highly engineered, and durable batteries, and their secondary use has become a major problem.

As a secondary active material, ■2o3, V6O1
Layered compounds of Ti512 and V82, which are tertiary metal compounds, are known as compounds that cause topochemical warping with Li, and up to now, the compounds of titanium, zirconium, hafnium, niobium, tantalum, and vanadium have been developed. , selenide, telluride? A battery using L (U.S. Pat. No. 4,089,052, Tatami Silk Sho) and the like have been disclosed.

However, compared to such research on active materials for Futakichi Pond, research on the charging and discharging characteristics of Li electrodes has not been sufficient. The search for electrolytes with excellent charge-discharge characteristics such as discharge efficiency and cycle life has become a serious issue. In an attempt to improve the charging and discharging efficiency of Li electrodes, an attempt was made to add triLiCtO4/propylene carbonate V nitromethane and S02 cicada additives (Electro-chimica, Acta,
vol. 22, p. 75-83 (1977))
etc. have been carried out, but they are not necessarily sufficient, and furthermore, the preparation for lithium secondary illumination has been delayed.

The present invention has been made based on these four aspects, and one of the aspects is to provide a non-aqueous solution for lithium secondary batteries, which has been custom-made for charging and discharging Li+.

Therefore, the lithium secondary turtle and other non-water holes due to non-invention
The explanation is that in a nonaqueous electrolyte in which a lithium salt is dissolved into an organic solution, propylene carbonate is added to the nonaqueous solution as a part of the solution.
e) and 1,2-dimethoxyethane (1,2-di
The special feature is the use of a covered solvent (methoxy ethane).

According to the present invention, the charging of Li electrode Tj51. We can provide custom-made excellent non-aqueous electrolytes for lithium secondary batteries.

The present invention will be explained in more detail.

Lithium secondary batteries use lithium as a negative electrode active material, and Li
+ Electrochemically for ions? At i5 company, 〃・tsuL
1+ Ion and Tsukasa are inversely anti-chemistry brothers, -th is a fact of life to stop goods trade, and lithium salts are treated like mushrooms. However, as for this lithium secondary battery σ Ariiso # love, uninvented 2, 1,
A mixed solvent of 2-dimethoxyethane and propylene carbonate is used.

In order to improve the photodischarge efficiency of Li electrodes, it is thought that a material in which the Li salt in the solvent system is easily dissociated and the mobility of Li + ions is large is required. The most effective method is to mix a solvent with a low conductivity, which easily dissociates Li salts, and a sowing medium, which has a low conductivity of 1,2-dimethoxyethane, and increases the mobility of Li+ ions, in an optimal ratio. It is true.

The non-aqueous electrolyte for lithium batteries according to the invention uses propylene carbonate and 1 as an organic solvent of the non-aqueous electrolyte.
, 2-dimethoxyethane combination? Since we use 27,
The photodischarge efficiency of the formed lithium battery is significantly improved.

The organic solvent of the electrolyte according to the invention is propylene carbonate and 1,2-dimethoxyethane, as in the case of circulation, but the bath negative dissolved therein can freely use the solutes conventionally used in batteries of this type. be able to. For example, L,
1c104. LiBF4. LiAsF6LiPk'b
Inorganic salts such as yLI AlCl 4 r and CF”3SO
3; Salts such as Li, CI"3C00Li, etc. can be used.

These solutes are added to the pre-sizing solvent, preferably at a concentration of 0.5 to 2
．． 5N melted. propylene carboney) I/C1
This is because if the solute is less than 0.5 N, the charge/discharge customization will be significantly reduced, and if it exceeds 2.5 N, the solute will not be easily understood. Also, if the concentration of the solute in 1,2-dimethoxyethane is less than 0.5N, the charging 'a#f' property will occur.
2. ! When MJ is exceeded, the viscosity increases and the photoelectric properties also decrease. The most TLF-like way would be to cut 2N each.

The mixing ratio of propylene carbonate and 1,2-dimethoxyethane was as follows: propylene carbonite in which the solute was dissolved for 0.5 to 2.5 hours, and the previous ML solute k o, 5 to 2.
The volume ratio of 1,2-dimethoxyethane in a 5N bath is favorable.
The ratio is preferably 2:8 to 7:3, most preferably 5:5. The surface ratio of propylene carbonite dissolved in the punishment bath is 228. If the surface ratio is less than 228, the flat floor where the introspection was washed becomes wider, and the charge and discharge of 1,2-dimethoxyethane alone is custom made. If the number is more than 723, it will approach the charge/discharge custom order of propylene carbonite kP, and even if it is Isu'nK, the charge/discharge custom order will deteriorate.

Below, we will prove the disadvantages of the present invention.

Example 1 A battery using Lt was prepared using a Pt electrode as a working electrode and a Li-all front electrode as a counter electrode, and Li was precipitated onto the Pt electrode to measure the charge/discharge characteristics of NLi&. The number of electrolysis is lN
LiC4O4 was converted into 1,2-dimethoxyethane (hereinafter, DM
E] and propylene carbonate (hereinafter abbreviated as PC) dissolved in -f:f'L were used in a 1:1 volume ratio. The conductivity of this electrolyte is 11.5 0-3 Ω-1 cm-1.
, INLiCtO4/PC* - Unique conductivity Ruru 6x
io-'Ω-1 cm-1.

Both legs are output for 1 minute at 5mA/Cm2 foot am], pt
After photoelectrically applying Lif Machida on the top, a cycle KM was performed in which Li1i and Machida were placed on Pty in a 4L circle, discharging as i+ ions. The charge/discharge efficiency is calculated from the potential change of Pt, and the Li deposited on the Pt
The amount of energy and P required to discharge Li+ ions
It was calculated from the ratio of the amount of electrolyte required to deposit Lif on the surface of t.

1-th is a diagram showing the island Q of charging/discharging efficiency and number of cycles.
b) D. Photodischarge physical properties of a lifting platform using INLiCtO4/PCJa7L single-thread turtle screen (previous paper f+4).

Further, when the charging and discharging efficiency of the Li tube in the liquid solution of the INL i C104/DME alone system was determined for 1 time, it was approximately 0% in one cycle and did not recover after that. As can be seen from FIG. 1, compared to the single yarn (b), the mixed yarn (a) clearly has the same charge/discharge performance.

As is clear from the above-mentioned intelligence, the inventive method was able to reduce the photodischarge rate of Li and other materials by using ink using a mixed bath of propylene carbonate and 1,2-dimethoxyethane as a solvent and using citrus salt as a solute. It is possible to develop a non-aqueous solution for lithium secondary batteries that has good, long, and local Li+ ion conductivity.

[Brief explanation of the drawing]

FIG. 1 shows the relationship between the charge/discharge efficiency of a lithium ball and the number of cycles in an example of the present invention. Applicant's agent 1) Masa Lee Miya

Claims (1)

[Claims] A non-aqueous electrolyte in which a lithium salt is dissolved in an organic solvent, and a lithium secondary characterized by ink using a mixed solvent of fluoropylene carbonate and 1,2-dimethoxyethane as the organic solvent of the non-aqueous electrolyte. Non-aqueous electrolyte for batteries.