Polymer-in-Salt Electrolyte from Poly(caprolactone)-graft-polyrotaxane for Ni-Rich Lithium Metal Batteries at Room Temperature

摘要

Solid-state lithium batteries with solid polymer electrolyteshaverecently attracted extensive attention due to their promising potentialin high energy density and safety. However, the principal issues plaguingthe solid polymer electrolytes are their restricted ionic conductivitiesat ambient temperature and the limited tolerance to the widely usedhigh-voltage cathodes (such as LiNi0.8Mn0.1Co0.1O2, NCM811), thus limiting their practical applicationsseriously. In this regard, a superior polymer-in-salt solid electrolytefrom poly(caprolactone)-graft-polyrotaxane (PGPE)is developed for high-voltage lithium batteries operated at room temperature.The PGPE displays remarkable electrochemical properties at room temperature,with an exceptional ionic conductivity of 4.89 x 10(-4) S cm(-1) and a lithium-ion transference number ofapproximately 0.64, stemming from the rapid segmental motions of PCLsidechains by the enhanced dynamics of the cyclic molecules alongthe axial polymer chain of polyrotaxane. More importantly, the PGPEdemonstrates a high electrochemical oxidation voltage of & SIM;4.7V, suggesting the excellent electrochemical stability of PGPE againstthe NCM811-based cathode. Owing to the dense LiF-rich CEI self-generatedon the NCM811 particles in the cathode, the transition metal ion diffusionis successfully constrained and the PGPE is well protected from continuousdecomposition. The PGPE also shows superior interfacial stabilitybetween the metallic Li and the electrolyte. As a result, the all-solid-stateNCM811|PGPE|Li cell exhibits superior discharge capacity (196 mAhg(-1)) and extraordinary long-term cycling stability(74% capacity retention at 150 cycles) at 30 & DEG;C.

关键词