Enabling All-Solid-State Li Metal Batteries Operated at 30 °C by Molecular Regulation of Polymer Electrolyte

Y Wei and TH Liu and WJ Zhou and H Cheng and XT Liu and J Kong and Y Shen and HH Xu and YH Huang, ADVANCED ENERGY MATERIALS, 13 (2023).

DOI: 10.1002/aenm.202203547

The low ionic conductivity of poly(ethylene oxide) (PEO)-based polymer electrolytes at room temperature and the undesired lithium-dendrite growth at Li|PEO interface impede their further application. Herein, a PEO polymer is regulated at the molecular level through a copper ion (Cu2+) coordination effect with both PEO and Li salts to achieve a high Li+ conductivity of 0.2 mS cm(-1) and a transference number of 0.42 at 30 degrees C. Moreover, the Cu-coordinated PEO electrolyte is neither sticky nor hygroscopic because the hydrophilic oxygen groups in PEO are terminated by Cu ions. Furthermore, the in situ formed F/Li-rich inorganic layer induced by CuF2 additive accelerates Li+ transport kinetics and enables uniform Li+ deposition during Li plating/stripping. As a result, the Cu2+-coordinated PEO electrolytes deliver a high critical current density of 1.5 mA cm(-2) at 30 degrees C. An all-solid- state Li-LiNi0.83Co0.12Mn0.05O2 (NCM83) battery with such a copper coordinated PEO electrolyte exhibits a long cycle life over 500 cycles with a capacity retention of 71% under 0.6 C at 30 degrees C. When the mass loading increases to a record high of 7 mg cm(-2), the Li-NCM83 cell delivers a high areal capacity of 1.07 mAh cm(-2) under 0.1 C at 30 degrees C.

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