Adjusting the local solvation structures and hydrogen bonding networks for stable aqueous batteries with reduced cost

Abstract

Exploring low-cost and effective approaches to extend the potentials of aqueous electrolytes is highly desired. Herein, it is found that the activity of H2O in aqueous electrolytes could be intensively manipulated by introducing small urea and long-chain polyethylene glycol (PEG) molecules into LiTFSI-H2O electrolyte systems without super salt concentration. The urea and PEG molecules could exclude partial coordinated H2O out of the inner solvation shell of Li+ and reconstruct hydrogen-bonding network between H2O and PEG molecules outside the solvation sheaths with restricted H2O activity and extended electrochemical window. The bonding competitions in aqueous electrolytes and their correlation to the electrochemical performance of full cells are studied. When the occurrence probability of H2O around Li+ is lower than 40%, stable cycling of 3.1 V LiMn2O4−Li4Ti5O12 full cell is achieved, showing 73% capacity retention after 200 cycles at 1 C rate in optimal electrolytes. This work provides new avenues to understand the role of H2O and explore low-cost and effective approaches for the development of next-generation aqueous lithium-ion batteries.