Electrolyte solvent for improving safety of battery and lithium secondary battery comprising the same
View Patent ↗The present invention provides an electrolyte solvent for batteries, which comprises fluoroethylene carbonate and linear ester solvent. Also, the present invention provides a lithium secondary battery comprising a positive electrode, a negative electrode and an electrolyte, wherein the electrolyte comprises fluoroethylene carbonate and linear ester solvent. The inventive electrolyte solvent can improve the battery safety without deteriorating the battery performance.
1. A method of preventing thermal explosions in a lithium secondary battery, comprising combining
an electrolyte solvent comprising
a lithium salt,
20-60% by volume of fluoroethylene carbonate, and
40-80% by volume of linear ester,
the amounts of fluoroethylene carbonate and linear ester solvent being based on the total volume of the electrolyte solvent, with
a positive electrode, and
a negative electrode,
to form the lithium secondary battery, and charging the battery at up to 4.35 V,
wherein the lithium secondary battery containing the electrolyte is able to withstand a temperature of 150° C. for up to 120 minutes without a thermal explosion.
2. The method of claim 1 , wherein the electrolyte has a conductivity of 7.56 mS/cm or more.
3. The method of claim 1 , wherein the battery is charged at up to 4.2V.
4. The method of claim 3 , wherein the lithium secondary battery containing the electrolyte is able to withstand a temperature of 150° C. for more than 90 minutes without a thermal explosion.
5. The method of claim 1 , wherein the fluoroethylene carbonate solvent is selected from the group consisting of monofluoroethylene carbonate, difluoroethylene carbonate and a mixture thereof.
6. The method of claim 1 , wherein the linear ester solvent is selected from the group consisting of ethyl methyl carbonate, dimethyl carbonate, diethyl carbonate, ethyl acetate, methyl propionate, and a mixture of two or more thereof.
7. The method of claim 1 , wherein the lithium salt comprises lithium hexafluorophosphate (LiPF 6 ), lithium tetrafluoroborate (LiBF 4 ), lithium bis(trifluoromethanesulfonyl)imide (LiN(CF 3 SO 2 ) 2 ), lithium bis(perfluoroethylsulfonyl)imide (LiN(C 2 F 5 SO 2 ) 2 ), lithium tris(trifluoromethanesulfonyl)methide (LiC(CF 3 SO 2 ) 3 ), lithium triflate (LiCF 3 SO 3 ), lithium bisoxalatoborate (LiC 4 BO 8 ) and a mixture of two or more thereof.
8. The method of claim 1 , wherein the positive electrode comprises active materials including LiCoO 2 ; LiNiO 2 ; LiMn 2 O 4 ; LiMnO 2 ; LiNi 1-X Co x M Y O 2 where M=Al, Ti, Mg or Zr, 0<X≦1, and 0≦Y≦0.2; LiNi X Co Y Mn 1-X-Y O 2 where 0<X≦0.5, and 0<Y≦0.5; LiM x M′ y Mn (2-x-y) O 4 where M, M′=V, Cr, Fe, Co, Ni or Cu, and 0<X≦1, 0<Y≦1); or LiCoPO 4 .
9. The method of claim 1 , wherein the negative electrode includes materials which absorb, store, and release lithium, and where the negative electrode materials include carbon, silicon, and tin compounds.
10. A method of preventing thermal explosions in a lithium secondary battery, comprising
combining
an electrolyte solvent comprising
a lithium salt,
20-60% by volume of a fluoroethylene carbonate selected from the group consisting of mono fluoroethylene carbonate, difluoroethylene carbonate and a mixture thereof, and
40-80% by volume of a linear ester selected from the group consisting of ethyl methyl carbonate, dimethyl carbonate, diethyl carbonate, ethyl acetate, methyl propionate, and a mixture of two or more thereof,
the amounts of fluoroethylene carbonate and linear ester solvent being based on the total volume of the electrolyte solvent, with
a positive electrode, and
a negative electrode,
to form the lithium secondary battery, and
charging the battery at up to 4.35 V,
wherein the lithium secondary battery containing the electrolyte is able to withstand a temperature of 150° C. for up to 120 minutes without a thermal explosion.
11. A method of preparing a lithium secondary battery, comprising
combining
an electrolyte solvent comprising
a lithium salt,
20-60% by volume of fluoroethylene carbonate, and
40-80% by volume of linear ester,
the amounts of fluoroethylene carbonate and linear ester solvent being based on the total volume of the electrolyte solvent, with
a positive electrode, and
a negative electrode,
to form the lithium secondary battery, and
charging the battery at up to 4.35 V,
wherein the lithium secondary battery containing the electrolyte is able to withstand a temperature of 150° C. for up to 120 minutes without a thermal explosion.