Balancing Charged Groups in Protein Additives: A Key to Enhancing the Performance of Polymer-Based Electrolytes in Solid-State Lithium–Metal Batteries
Jianming Tao, Lang Wen, Qinghao Liu, Cai Yanhuang, Yanmin Yang, Feng Qi, Yingbin Lin
Abstract
Solid-state Li metal batteries equipped with polymer electrolytes are highly coveted for their flexibility and remarkable energy density; however, their advancement is hindered by limited ionic conductivity and poor interfacial stability. Herein, we report that protein additives can significantly improve the performance of poly(ethylene oxide)-based solid electrolytes and elucidate the ion-conducting mechanism by comparing proteins with different charged groups (CGs). Positive CGs can anchor anions in Li salts to increase ion transference number but also adsorb polymer chains resulting in a decrease in ionic conductivity. Negative CGs promote the dissociation of Li salts and Li + conduction; however, it depends on the long-range protein chains. In comparison to the α-amylase with more negative CGs and bovine serum albumin (BSA) with more positive CGs, the casein with balanced groups enables the solid electrolyte to have a significantly higher Li + transference number of 0.45 and superior mechanical properties. Furthermore, it can also promote uniform Li plating and stripping, as well as the formation of a stable solid electrode–electrolyte interphase. When paired with the LiNi 0.8 Co 0.1 Mn 0.1 O 2 cathode, the batteries can still maintain a high specific capacity of 97.7 mA h g –1 after 200 cycles at a 1 C-rate, highlighting the efficacy of utilizing CGs-balanced proteins as additives in solid-state batteries.