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. An electrochemical device comprising a polymer solid electrolyte synthesized by crosslinking a mixture comprising a lithium salt, a crosslinkable monomer, an initiator, a sulfone 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 electrochemical device 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 electrochemical device of claim 1 , wherein the lithium salt has a concentration ranging from 0.5 M to 7 M.
4. The electrochemical device of claim 1 , wherein the carbonate additive is selected from the group consisting of ethylene carbonate (EC), vinylene carbonate (VC) and fluoroethylene carbonate (FEC).
5. The electrochemical device of claim 1 , wherein the sulfone ion dissociation compound is 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.
6. The electrochemical device of claim 1 , wherein the crosslinkable monomer has a concentration ranging from 5 wt % to 40 wt %.
7. The electrochemical device of claim 1 , wherein the lithium salt is LiTFSI with a concentration of 0.5 M, the sulfone ion dissociation compound is diethyl sulfone, the additive is VC with a concentration of 0.5 wt %, the crosslinkable monomer has a concentration of 20 wt %, and the initiator is AIBN with a concentration of 1 wt %.
8. The electrochemical device of claim 1 , wherein the lithium salt is LiTFSI with a concentration of 3.0 M, the sulfone ion dissociation compound is diethyl sulfone, the additive is VC with a concentration of 0.5 wt %, the crosslinkable monomer has a concentration of 20 wt %, and the initiator is AIBN with a concentration of 1 wt %.
9. The electrochemical device of claim 8 , wherein the electrochemical device, at room temperature, has an initial capacity of 162 mAh/g.
10. The electrochemical device of claim 8 , wherein the electrochemical device, at a temperature of 85° C., has an initial capacity of 169 mAh/g.
11. The electrochemical device of claim 1 , wherein the lithium salt is LiTFSI with a concentration of 0.5 M, the sulfone ion dissociation compound is diethyl sulfone, the additive is FEC with a concentration of 0.5 wt %, the crosslinkable monomer has a concentration of 20 wt %, and the initiator is AIBN with a concentration of 1 wt %.
12. The electrochemical device of claim 1 , wherein the lithium salt is LiTFSI with a concentration of 3.0 M, the sulfone ion dissociation compound is diethyl sulfone, the additive is FEC with a concentration of 0.5 wt %, the crosslinkable monomer has a concentration of 20 wt %, and the initiator is AIBN with a concentration of 1 wt %.
13. The electrochemical device of claim 12 , wherein the electrochemical device, at room temperature, has an initial capacity of 152 mAh/g.
14. The electrochemical device of claim 1 , further comprising an anode comprising graphite or lithium metal.
15. The electrochemical device of claim 1 , wherein the lithium salt is LiTFSI with a concentration of 1.8 M, the sulfone ion dissociation compound is dimethyl sulfone, the additive is trimethyl phosphate and fluoroethylene carbonate (FEC), and the volume ratio of dimethyl sulfonate/trimethyl phosphate/FEC is 55/40/5, the crosslinkable monomer has a concentration of 10 wt %, and the initiator is AIBN with a concentration of 1 wt %.
16. The electrochemical device 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+.