高供体电解质赋予石墨阴离子衍生界面以实现稳定钾储存

High-donor electrolyte endows graphite with anion-derived interphase to achieve stable K-storage

石墨负极有望应用于钾离子电池,但受到循环过程中不可控的体积波动和枝晶生长的限制.在此,我们利用酰胺基电解质构建了具有高机械强度和离子电导率的阴离子衍生界面,可有效解决这些问题.酰胺分子的高供体数可以加强溶剂分子与K+的溶剂化作用,确保更多的阴离子进入初级溶剂化鞘层.缩短的溶剂与阴离子距离有利于电子从溶剂化的K+转移到阴离子,进而促进阴离子还原.生成的富含无机物的界面缓冲了充放电过程中的体积变化,抑制了K枝晶的生成,促进了钾离子的扩散.基于此,K//K对称电池以0.15 V的极化电位稳定循环超过2800 h.石墨电极实现了C?KC60?KC48?KC36?KC_(2)4?KC8的高度可逆相变,在循环100周后仍保持了217.6 mA h g-1的高放电容量和86.9%的容量保持率.组装的全电池也表现出52.5 W h kg-1的高能量密度.这项工作突出了界面结构的重要性,并为设计高性能电解质提供了全新策略.

Graphite anodes are expected to be applied in potassium-ion batteries,but it is limited by uncontrolled volume fluctuation and dendrite growth during cycles.Herein an anion-derived interphase with high mechanical strength and ionic conductivity is constructed to address the aforementioned issues using an amide-based electrolyte.The highdonor number for an amide molecule can strengthen the solvation with K+,ensuring more anions enter the primary solvation sheath.The shortened distance is in favor of the electron transfer from the solvated K+to the anion and subsequently motivates the anion reduction.The obtained inorganic-rich interphase buffers volume change,suppresses K dendrite propagation,and facilitates ion diffusion.Based on these,symmetric K//K cells could operate stable plating and stripping with a small polarization of 0.15 V for over 2800 h The graphite electrode achieves a highly reversible phase transition of C?KC60?KC48?KC36?KC_(2)4?KC8.A high discharge capacity of 217.6 mA h g-1with retention of 86.9%is obtained after 100 cycles.The assembled full battery also exhibits a high energy density of 52.5 W h kg-1.This work highlights the importance of the interfacial structure and provides a brand-new strategy for designing high-performance electrolytes.