Regulating Solvation Structure In Aqueous Zinc-ion Battery Towards Stable Zinc Anode

Aqueous zinc ion batteries(AZIBs)with the advantages of high theoretical capacity(820 mA h g-1,5854 mA h cm-3)and intrinsic safety are promising large-scale energy storage devices.However,zinc dendrite growth and side reactions(corrosion and hydrogen evolution)occurring on the Zn anode can lead to poor cycle life and performance degradation of the battery,which greatly hinders the development of AZIBs.Therefore,the development of highly reversible and stable Zn anode is essential to enhance the long cycle life of AZIBs.Regulating the composition of the Zn anode/electrolyte interface is an effective strategy to reduce zinc dendrites and side reactions.Herein,mesoporous alumina zincophilic sieve with tiny pores and triethanolamine electrolyte additive are used to regulate solvent structure and improve the stability of Zn anode.We also investigate the mechanism of AZIBs for improving the performance.The details of the work are as follows:1.The pore size of mesoporous alumina is regulated by carboxylic acids with different carbon chain lengths from C3 to C18.Base on the principle of sieve effect,we are able to regulate solvation structure by mesoporous alumina zincophilic sieve.Among them,the lactic acid-induced(C3)mesoporous alumina(LA-MA)molecular sieve of pore size at 3.0 nm.And Raman spectroscopy reveals that LA-MA can regulate the solvation structure from[Zn2+(H2O)6]SO42-]to the higher coordinated[Zn2+(H2O)5OSO32-],which greatly inhibits the corrosion and hydrogen evolution reaction of Zn.In addition,the LA-MA surface with abundant ion channels and zincophilic functional groups(C=O,C-O)facilitates the adsorption of Zn ions and accelerates the diffusion of Zn ions,which enables the uniform deposition of Zn ions on the zinc surface.As a result,the LA-MA anode exhibits high cycling stability over 5100 h at 0.25 mA cm-2,0.25 mA h cm-2.And the LA-MA@Zn‖LA-MA@Cu cell shows high CE of 99.6%over 1300 cycles.Moreover,LA-MA@Zn‖CNT/MnO2 full cell maintains a remarkable capacity retention of 94.2%after 3500 cycles and the pouch battery delivers a high reversible capacity of 164 mA h g-1 after 1000 cycles at 1 A g-1.2.The triethanolamine(TEA)electrolyte additive is introduced to stabilize the zinc anode by regulating the solvent structure of the interface.Due to the abundant hydroxyl groups and strong surface charge density of triethanolamine,Raman spectroscopy reveals that it will replace part of the solvated water and coordinate with Zn ions,thus reducing the amount of active water of Zn ions and inhibiting water-induced side reactions.Furthermore,the addition of TEA increases the ionic conductivity of the electrolyte,which accelerates the transfer kinetics of Zn ions,making Zn ions plating/stripping process faster.And it also inhibits the formation of zinc dendrites.As a result,the Zn anode can cycle for 2400 hours at 1 mA cm-2,1 mA h cm-2 in a symmetric cell with only 32 mV overpotential.And even under a high current density of 5 mA cm-2,it can still maintain 840 hours.Impressively,the Zn‖CNT/MnO2 full cell with TEA additive can reach a capacity retention of 82.5%after 1100 cycles.