Self-Assembled Ordered Nanostructure of Zwitterionic Co-Solutes Induces Localized High-Concentration Electrolytes for Ultrastable and Efficient Zinc Metal Anodes

Localized high-concentration electrolytes (LHCEs) are considered as promising electrolyte candidates to resolve technical issues of metal batteries owing to their unique interfacial properties and solvation structures. Herein, we propose a self-assembly chemical strategy into the LCHEs induced by ordered nanostructure of zwitterionic co-solutes for highly efficient and ultrastable zinc (Zn) metal batteries. Through the systematic screening of six zwitterionic compounds, 3-(decyldimethylammonio)propanesulfonate salt (C₁₀) with the decyl chain and zwitterions was determined as an optimum to construct quasi-spherical aggregates with a periodic length of 3.77 nm, as confirmed by comprehensive synchronous small-angle X-ray scattering, Guinier, pair distance distribution function, Porod, and other spectroscopic characterizations and molecular dynamic simulation. In particularly, this self-assembled structure in electrolyte environments was attributed to increasing the proportion of both contact and aggregated ion pairs for the formation of LHCEs as well as to providing fast and selective Zn²⁺ conducting channels and uniform solid electrolyte interfaces for facilitated charge transfer kinetics. Moreover, the preferential adsorption of the self-assembled C₁₀ on the Zn(002) surface modulated the electrical double layer to suppress hydrogen evolution and corrosion reactions. Consequently, the Zn||Zn symmetric cells in Zn(OTf)₂/C₁₀ electrolytes showed long-term plating/stripping behaviors over 2800 h at 1 mA cm^-2 and 1 mAh cm^-2 as well as over 1200 h even at 5 mA cm^-2 and 5 mAh cm^-2 with a very high depth of discharge of 42.7%. Furthermore, the Zn||VO₂/CNT full cells in Zn(OTf)₂/C₁₀ electrolytes delivered a record-high capacity of 8.10 mAh cm^-2 at an ultrahigh cathode mass loading of 50 mg cm^-2 after 150 cycles.