钠离子电容器负极的双功能补钠研究

Bifunctional sodium compensation of anodes for hybrid sodium-ion capacitors

电极的首次库伦效率低是限制快充钠离子电容器规模化使用的原因之一,这主要源于电解液的不可逆分解以及电极材料造成的不可逆损失.我们选取高倍率特性的Nb_(2)O_(5)负极材料作为研究对象,采用钠萘/2-甲基-四氢呋喃作为预钠化剂,发展了一种简单且可精确调控的双功能预钠化剂,实现了预活化,获得了高稳定循环的NaxNb_(2)O_(5)电极,从而补偿了钠在材料中的不可逆吸收.研究发现,预钠化过程同时抵消了电解液分解所产生的损失,有利于在电极/电解液界面形成坚固的富含无机物的固体电解质界面膜.通过补偿Nb_(2)O_(5)负极的体相与界面的钠损失,构建了稳定且具有高能量密度的钠离子电容器.本研究为调控储钠电极的首次库伦效率及其在下一代钠离子电容器中的应用提供了新方法.

The low initial Coulombic efficiency(ICE)for the electrodes which stems from electrolyte decomposition and irreversible sodium uptake by the material itself,is one of the reasons limiting the large-scale sodium-ion capacitors(SICs).Here,we report a simple but precise bifunctional presodiation of the Nb_(2)O_(5)anode(as a typical example)using sodium naphthalene/2-methyltetrahydrofuran as a pre-sodiated agent.The pre-sodiated agent realizes the pre-activation to achieve stable cycling of NaxNb_(2)O_(5),thus compensating the irreversible Na uptake.Moreover,this process offsets the electrolyte decomposition loss,and facilitates the formation of a robust inorganic-rich solid electrolyte interphase layer.Stable and high-energy SIC devices are achieved by compensating the interphase and bulk sodium loss of Nb_(2)O_(5)anodes.This work provides new insights into tuning the ICE of sodium-storage electrodes for next-generation and scaled-up applications of SICs.