Hybrid electrolytes with controlled network structures for lithium metal batteries
Solid polymer electrolytes (SPEs) with tunable network structures are prepared by a facile one-pot reaction of polyhedral oligomeric silsesquioxane (POSS) and poly(ethylene glycol) (PEG). These SPEs with high conductivity and high modulus exhibit superior lithium dendrite growth resistance even at high current densities. Measurements of lithium metal batteries with a LiFePO4 cathode show excellent cycling stability and rate capability. Also disclosed are products made by the process of the invention and batteries including such products.
1. A process for making lithium or sodium solid polymer electrolytes comprising a step of reacting an inorganic polyhedral oligomeric silsesquioxane with end functional groups and a diterminal functionalized poly(ethylene glycol) or a diterminal functionalized poly(ethylene oxide) to form a chemically crosslinked network in the presence of a lithium or sodium salt or mixture of lithium and sodium salts.
2. The process of claim 1 , wherein the polyhedral oligomeric silsesquioxane is reacted with an amine-terminated diterminal functionalized poly(ethylene glycol).
3. The process of claim 1 wherein the polyhedral oligomeric silsesquioxane is reacted with the diterminal functionalized poly(ethylene oxide).
4. A process as claimed in claim 1 , wherein the inorganic polyhedral oligomeric silsesquioxane has the structure:
wherein each R group is independently selected from hydrogen, hydrocarbyl, reactive functional groups and functionalized hydrocarbyl groups and at least one of the R groups contains a functional group suitable for a cross-linking reaction.
5. The process as claimed in claim 4 , wherein at least one R group comprises an epoxy group.
6. The process as claimed in claim 4 , wherein the inorganic polyhedral oligomeric silsesquioxane has eight R groups each of which comprises a functional group suitable for a cross-linking reaction selected from reactive functional groups and functionalized hydrocarbyl groups.
7. The process as claimed in claim 1 , wherein the inorganic polyhedral oligomeric silsesquioxane is selected from octakis(3-glycidyloxypropyldimethylsiloxy)octasilsesquioxane, epoxycyclohexylethyl polysilsesquioxane, glycidyl polyhedral oligomeric silsesquioxane, and octa epoxycyclohexyldimethylsilyl polyhedral oligomeric silsesquioxane.
8. The process as claimed in claim 1 , wherein the polyhedral oligomeric silsesquioxane is reacted with the diterminal functionalized poly(ethylene glycol) and a poly(ethylene glycol) chain in the diterminal functionalized poly(ethylene glycol) has a number average molecular weight of from about 250 g/mol to about 300,000 g/mol.
9. The process as claimed in claim 1 , wherein the salt is the lithium salt with an anion selected from the group consisting of bis(trifluoromethane)sulfonamide, hexafluoroarsenate, hexfluorophosphate, perchlorate, tetrafluoroborate, tris(pentafluoroethyl)trifluorophosphate, trifluoromethanesulfonate, bis(fluorosulfonyl)imide, cyclo-difluoromethane-1,1-bis(sulfonyl)imide, cyclo-hexafluoropropane-1,1-bis(sulfonyl)imide, bis(perfluoroethyanesulfonyl)imide, bis(oxalate)borate, difluoro(oxalato)borate, dicyanotriazolate, tetracyanoborate, dicyanotriazolate, dicyano-trifluoromethyl-imidazole, and dicyano-pentafluoroethyl-imidazole.
10. The process as claimed in claim 1 , wherein the molar ratio of moles of the polyhedral oligomeric silsesquioxane to moles of the diterminal functionalized poly(ethylene glycol) or moles of the diterminal functionalized poly(ethylene oxide) is from about 1:100 to about 10:1.
11. The process as claimed in claim 1 , further comprising a step of blending with poly(ethylene glycol), having a number average molecular weight of less than 2,000 g/mol.
12. The process as claimed in claim 2 , wherein the amine-terminated diterminal functionalized poly(ethylene glycol) has a molecular weight of from about 2,000 g/mol to about 6,000 g/mol.
13. The process as claimed in claim 1 , wherein the polyhedral oligomeric silsesquioxane is reacted with the diterminal functionalized poly(ethylene oxide) and the diterminal functionalized poly(ethylene oxide) is amine-terminated.
14. A product made by the process of claim 1 .
15. A battery comprising the product of claim 14 .
16. The process as claimed in claim 1 , wherein the polyhedral oligomeric silsesquioxane is reacted with the diterminal functionalized poly(ethylene oxide) and the diterminal functionalized poly(ethylene oxide) is hydroxyl-terminated.
17. The process as claimed in claim 1 , wherein the polyhedral oligomeric silsesquioxane is reacted with the diterminal functionalized poly(ethylene glycol) and the diterminal functionalized poly(ethylene glycol) is amine-terminated.
18. The process as claimed in claim 1 , wherein the molar ratio of moles of the polyhedral oligomeric silsesquioxane to moles of the diterminal functionalized poly(ethylene glycol) or moles of the diterminal functionalized poly(ethylene oxide) is from about 1:20 to about 1:1.
19. The process as claimed in claim 1 , wherein the molar ratio of moles of the polyhedral oligomeric silsesquioxane to moles of the diterminal functionalized poly(ethylene glycol) or moles of the diterminal functionalized poly(ethylene oxide) is from about 1:6 to about 1:2.
20. The process as claimed in claim 1 , wherein the polyhedral oligomeric silsesquioxane is reacted with the diterminal functionalized poly(ethylene glycol) and a poly(ethylene glycol) chain in the diterminal functionalized poly(ethylene glycol) has a number average molecular weight of from about 500-10,000 g/mol.