Electrolytes for high-voltage cathode materials and other applications
The present invention generally relates to electrolytes for use in various electrochemical devices. In some cases, the electrolytes are relatively safe to use; for example, the electrolytes may be resistant to overheating, catching on fire, burning, exploding, etc. In some embodiments, such electrolytes may be useful for certain types of high-voltage cathode materials. In some cases, the electrolytes may include ion dissociation compounds that can dissociate tight ion pairs. Non-limiting examples of ion dissociation compounds include trialkyl phosphates, sulfones, or the like. Other aspects of the invention are generally directed to devices including such electrolytes, methods of making or using such electrolytes, kits including such electrolytes, or the like.
1. A polymer solid electrolyte synthesized by crosslinking a mixture comprising a lithium salt, a crosslinkable monomer, a flame retardant as ion dissociation compound, and a carbonate additive that can enhance capacity retention of an electrochemical device, wherein the crosslinkable monomer has a formula of:
wherein the volume ratio of the additive to the ion dissociation compound is between 5/95 and 50/50 and the polymer solid electrolyte has an oxidation potential of at least 4.5 V with reference to Li/Li+.
2. The polymer solid electrolyte of claim 1 , wherein the lithium salt is selected from the group consisting of LiTFSI, LiFSI, LiBOB, LiPF 6 , LiBF 4 , LiClO 4 , LiAsF 6 , LiN(CF 3 SO 2 ) 2 , LiC(CF 3 SO 2 ) 3 , LiDFOB, LiF, LiCl, LiBr, LiI, Li 2 SO 4 , LiNO 3 , Li 3 PO 4 , Li 2 CO 3 , LiOH, lithium acetate, lithium trifluoromethyl acetate, and lithium oxalate.
3. The polymer solid electrolyte of claim 1 , wherein the lithium salt has a concentration ranging from 0.5 M to 7 M in the mixture.
4. The polymer solid electrolyte of claim 1 , wherein the carbonate additive is selected from the group consisting of 1,2-dimethoxyethane carbonate, ethylene carbonate (EC), vinylene carbonate (VC), fluoroethylene carbonate (FEC) and methylene ethylene carbonate.
5. The polymer solid electrolyte of claim 1 , wherein the flame retardant is a nitrogen-containing flame retardant, silicon-containing flame retardant, fluorine-containing flame retardant, an organophosphorus flame retardant or a combination thereof.
6. The polymer solid electrolyte of claim 1 , wherein the flame retardant is selected from the group consisting of methyl difluoroacetate, difluoroethyl acetate, trimethyl phosphate, triethyl phosphate, and a mixture thereof.
7. The polymer solid electrolyte of claim 1 , wherein the crosslinkable monomer has a concentration ranging from 5 wt % to 40 wt % in the mixture.
8. The polymer solid electrolyte of claim 1 , wherein the mixture for synthesizing the polymer solid electrolyte comprises an initiator.
9. The polymer solid electrolyte of claim 8 , wherein the initiator is selected from the group consisting of benzoyl peroxide, 2,2′-azobisisobutyronitrile (AIBN), 4,4-azobis(4-cyanovaleric acid) (ACVA), potassium persulfate, and ammonium persulfate.
10. The electrochemical device of claim 1 , wherein the mixture for synthesizing the polymer solid electrolyte further comprises a phosphate additive.
11. The electrochemical device of claim 10 , wherein the phosphate additive is selected from the group consisting of trimethyl phosphate and triethyl phosphate.
12. An electrochemical device comprising the polymer solid electrolyte of claim 1 .
13. The electrochemical device of claim 12 further comprising an anode.
14. The electrochemical device of claim 13 , wherein the anode comprises lithium metal.
15. The electrochemical device of claim 13 , wherein the anode comprises graphite.
16. The electrochemical device of claim 12 further comprising a cathode.
17. The electrochemical device of claim 16 , wherein the cathode comprises an electroactive material selected from the group consisting of lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium titanate, metallic lithium, lithium metal oxide, lithium manganese oxide, lithium cobalt oxide, and lithium iron phosphate.