Engineering Sodium-Ion Solvation Structure to Stabilize Sodium Anodes: Universal Strategy for Fast-Charging and Safer Sodium-Ion Batteries

Abstract

Sodium (ion) batteries are promising alternatives for lithium-ion batteries due to their lower cost caused by global sodium availability. However, the low Coulombic efficiency (CE) of the sodium metal plating/stripping process represents a serious issue for the Na anode, which hinders achieving higher energy density. Herein, we report that the Na+ solvation structure, particularly the type and location of the anions, plays a critical role in determining the Na anode performance. We show that the low CE results from anion-mediated corrosion, which can be tackled readily through tuning the anion interaction at the electrolyte/anode interface. Our strategy thus enables fast charging Na-ion and Na-S batteries with remarkable cycle-life. The presented insights differ from the prevailing interpretation that the failure mechanism mostly results from sodium dendrite growth and/or solid electrolyte interphase formation. Our anionic model introduces a new guideline for improving the electrolytes for metal (ion) batteries with greater energy density.

Engineering Solid Electrolyte Interface at Nano‐Scale for High‐Performance Hard Carbon in Sodium‐Ion Batteries

“…That could be associated with the high dielectric constant of EC solvent that induced stronger interaction between PF 6 − -solvent-Na + complex in carbonate electrolyte than in ether electrolytes (Figure 2c). [27,28] The different Na + -solvent-PF 6 − solvates could result in different reduction pathway and products of electrolytes, which usually contributes differential SEI components and structures. [28] This was confirmed by the CV scanning of HC electrodes in initial cycles for carbonate and ether electrolytes.…”

Lithium‐Ion Desolvation Induced by Nitrate Additives Reveals New Insights into High Performance Lithium Batteries

“…The observed mechanistic insight into the Li + desolvation process significantly enhances the previous investigation, such as carbonate‐based electrolytes for lithium‐ion, sodium‐ion, and potassium‐ion batteries. [ 23 ]…”

Design aspects of electrolytes for fast charge of Li‐ion batteries

“…This subject relates to the structure and stability of Li + ion solvation shell in the electrolytes, as shown in Figure 2, which are intrinsically affected by the type and ratio of solvents and counter anions. [29][30][31][32][33][34] In the electrolyte solutions, the Li + -coordinated solvent molecules are dynamically exchanging with the solvent molecules and counter anions (X − ) in the outer shell. Unlike the solvation and desolvation energies that are equal in value and offset at the anode and cathode, the solvation and desolvation activation energies at the anode and cathode are different in value, and both are required low for fast charge.…”

“…This subject relates to the structure and stability of Li + ion solvation shell in the electrolytes, as shown in Figure 2, which are intrinsically affected by the type and ratio of solvents and counter anions 29‐34 . In the electrolyte solutions, the Li + ‐coordinated solvent molecules are dynamically exchanging with the solvent molecules and counter anions (X − ) in the outer shell.…”