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, an ion dissociation compound, and an additive that can enhance capacity retention of an electrochemical device, 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 + , wherein the crosslinkable monomer has a formula of:
where R 1 comprises a structure selected from the group consisting of:
where n is an integer between 1 and 10,000, inclusive; where m is an integer between 1 and 5,000, inclusive; where R 2 , R 3 , R 4 , R 5 , and R 6 are each independently selected from the group consisting of hydrogen, methyl, ethyl, phenyl and benzyl, acrylate, epoxy ethyl, isocyanate, cyclic carbonate, lactone, lactam, and vinyl; and where * indicates a point of attachment.
2. The polymer solid electrolyte of claim 1 , wherein the formula of the monomer is:
3. 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.
4. The polymer solid electrolyte of claim 1 , wherein the lithium salt has a concentration ranging from 0.5M to 7M in the mixture.
5. The polymer solid electrolyte of claim 1 , wherein the additive is a carbonate selected from the group consisting of 1,2-dimethoxyethane carbonate, ethylene carbonate (EC), vinylene carbonate (VC), fluoroethylene carbonate (FEC) and methylene ethylene carbonate.
6. The polymer solid electrolyte of claim 1 , wherein the ion dissociation compound is a sulfone selected from the group consisting of divinyl sulfone, allyl methyl sulfone, butadiene sulfone, ethyl vinyl sulfone, dimethyl sulfone, diphenyl sulfone, methyl phenyl sulfone, isopropyl sulfone, trimethylene sulfone, tetramethylene sulfone, diethyl sulfone, and ethyl methyl sulfone.
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 mixture for synthesizing the polymer solid electrolyte comprises LiTFSI as the lithium salt with a concentration of 0.5M, diethyl sulfone as the ion dissociation compound, VC as the additive with a concentration of 0.5 wt %, the crosslinkable monomer with a concentration of 20 wt % and AIBN as the initiator with a concentration of 1 wt %.
10. The polymer solid electrolyte of claim 8 , wherein the mixture for synthesizing the polymer solid electrolyte comprises LiTFSI as the lithium salt with a concentration of 3.0M, diethyl sulfone as the ion dissociation compound, VC as the additive with a concentration of 0.5 wt %, the crosslinkable monomer with a concentration of 20 wt % and AIBN as the initiator with a concentration of 1 wt %.
11. The polymer solid electrolyte of claim 8 , wherein the mixture for synthesizing the polymer solid electrolyte comprises LiTFSI as the lithium salt with a concentration of 0.5M, diethyl sulfone as the sulfone ion dissociation compound, FEC as the additive with a concentration of 0.5 wt %, the crosslinkable monomer with a concentration of 20 wt % and AIBN as the initiator with a concentration of 1 wt %.
12. The polymer solid electrolyte of claim 8 , wherein the mixture for synthesizing the polymer solid electrolyte comprises LiTFSI as the lithium salt with a concentration of 3.0M, diethyl sulfone as the ion dissociation compound, FEC as the additive is FEC with a concentration of 0.5 wt %, the crosslinkable monomer with a concentration of 20 wt % and AIBN as the initiator with a concentration of 1 wt %.
13. The electrochemical device of claim 1 , wherein the mixture for synthesizing the polymer solid electrolyte further comprises a phosphate additive.
14. The electrochemical device of claim 13 , wherein the phosphate additive is selected from the group consisting of trimethyl phosphate and triethyl phosphate.
15. The polymer solid electrolyte of claim 13 , wherein the mixture for synthesizing the polymer solid electrolyte comprises LiTFSI as the lithium salt with a concentration of 1.8M, dimethyl sulfone as the ion dissociation compound, trimethyl phosphate and fluoroethylene carbonate (FEC) as the additive, the crosslinkable monomer with a concentration of 10 wt % and AIBN as the initiator with a concentration of 1 wt %, wherein the volume ratio of dimethyl sulfonate/trimethyl phosphate/FEC is 55/40/5.
16. An electrochemical device comprising the polymer solid electrolyte of claim 1 .
17. The electrochemical device of claim 16 further comprising an anode comprising graphite or lithium metal.
18. An electrochemical device comprising the polymer solid electrolyte of claim 10 , wherein the electrochemical device has an initial capacity of 162 mAh/g and 169 mAh/g at room temperature and 85° C., respectively.
19. An electrochemical device comprising the polymer solid electrolyte of claim 12 , wherein the electrochemical device has an initial capacity of 152 mAh/g at room temperature.
20. An electrochemical device comprising the polymer solid electrolyte of claim 15 , wherein the electrochemical device has a capacity retention of 80% after 200 cycles using a discharging current at a rate of 0.5C, an oxidation potential of at least 5.0V with reference to Li/Li+.