Nonaqueous electrolyte for secondary battery and nonaqueous-electrolyte secondary battery employing the same
View Patent ↗An object is to provide a nonaqueous electrolyte and a nonaqueous-electrolyte secondary battery which have excellent discharge load characteristics and are excellent in high-temperature storability, cycle characteristics, high capacity, continuous-charge characteristics, storability, gas evolution inhibition during continuous charge, high-current-density charge/discharge characteristics, discharge load characteristics, etc. The object has been accomplished with a nonaqueous electrolyte which comprises: a monofluorophosphate and/or a difluorophosphate; and further a compound having a specific chemical structure or specific properties.
1. A nonaqueous electrolyte, comprising:
(A) an electrolyte;
(B) a nonaqueous solvent dissolving the electrolyte;
(C) a salt of a monofluorophosphate ion of formula PO 3 F, a difluorophosphate ion of formula PO 2 F 2 , or a mixture thereof with at least one metal ion selected from a metal of Group 1 of the periodic table selected from lithium, sodium, potassium, and cesium, a metal of Group 2 of the periodic table selected from magnesium, calcium, strontium, and barium and a metal of Group 13 of the periodic table selected from aluminum, gallium, indium, and thallium; and
(D) at least one compound selected from the group consisting of:
wherein R 1 , R 2 , and R 3 are each independently a fluorine atom, an alkyl group comprising 1-12 carbon atoms and optionally substituted with a fluorine atom, or an alkoxy group comprising 1-12 carbon atoms and optionally substituted with a fluorine atom;
(ii) a nitrile compound;
(iii) an isocyanate compound;
(iv) a phosphazene compound;
(v) a disulfonic acid ester compound;
(vi) a sulfide compound;
(vii) a disulfide compound;
(viii) an acid anhydride;
(ix) a lactone compound comprising a substituent in the α-position; and
(x) a compound comprising a carbon-carbon triple bond.
2. The nonaqueous electrolyte of claim 1 , wherein a total content of the compound (D) is from 0.01% to 25% by mass, based on a total mass of the nonaqueous electrolyte.
3. The nonaqueous electrolyte of claim 1 , wherein a total content of the compound (D) is from 0.01% to 10% by mass, based on a total mass of the nonaqueous electrolyte.
4. The nonaqueous electrolyte of claim 1 , wherein a total content of the compound (D) is from 0.01% to 5% by mass, based on a total mass of the nonaqueous electrolyte.
5. The nonaqueous electrolyte of claim 1 , wherein a total content of the compound (D) is from 0.1% to 5% by mass, based on a total mass of the nonaqueous electrolyte.
6. The nonaqueous electrolyte of claim 1 , wherein a total content of the salt (C) is from 0.001% to 5% by mass, based on a total mass of the nonaqueous electrolyte.
7. The nonaqueous electrolyte of claim 1 , wherein a total content of the salt (C) is from 0.01% to 4% by mass, based on a total mass of the nonaqueous electrolyte.
8. The nonaqueous electrolyte of claim 1 , wherein a total content of the salt (C) is from 0.05% to 3% by mass, based on a total mass of the nonaqueous electrolyte.
9. The nonaqueous electrolyte of claim 1 , wherein the salt (C) is Li + PO 7 F 2 .
10. The nonaqueous electrolyte of claim 1 , wherein the salt (C) is Na + PO 2 F 2 .
11. The nonaqueous electrolyte of claim 1 , wherein the salt (C) is Mg 2+ (PO 2 F 2 − ) 2 .
12. A nonaqueous-electrolyte secondary battery comprising:
a negative electrode and a positive electrode, which are capable of occluding/releasing lithium ions; and
the nonaqueous electrolyte of claim 1 .
13. The nonaqueous-electrolyte secondary battery of claim 12 , wherein the negative electrode comprises a carbonaceous material.
14. The nonaqueous-electrolyte secondary battery of claim 12 , wherein the negative electrode comprises a negative-electrode active material comprising at least one selected from the group consisting of a silicon atom, a tin atom, and a lead atom.