Fire‐Retardant, Stable‐Cycling and High‐Safety Sodium Ion Battery

Abstract

The safety of energy storage equipment has always been a stumbling block to the development of battery, and sodium ion battery is no exception. However, as an ultimate solution, the use of non‐flammable electrolyte is susceptible to the side effects, and its poor compatibility with electrode, causing failure of batteries. Here, we report a non‐flammable electrolyte design to achieve high‐performance sodium ion battery, which resolves the dilemma via regulating the solvation structure of electrolyte by hydrogen bonds and optimizing the electrode–electrolyte interphase. The reported non‐flammable electrolyte allows stable charge‐discharge cycling of both sodium vanadium phosphate@hard carbon and Prussian blue@hard carbon full pouch cell for more than 120 cycles with a capacity retention of >85 % and high cycling Coulombic efficiency (99.7 %).

Rational Electrolyte Design toward Cyclability Remedy for Room‐Temperature Sodium–Sulfur Batteries

“…This suggests that the FDMA : MTFE system not only exhibits a low solubility of polar NaPSs to suppress their shuttling, [14] but also possesses weak dissociation of Na salts, allowing more anions to participate in SEI construction and thus, optimizing the electrode j electrolyte interfaces (insets of Figure 1d). [15] Molecular dynamics (MD) simulations were conducted to compare the solvation structures of three electrolytes: 1 M sodium bis(trifluoromethylsulfonyl)imide (NaTFSI) -FDMA, 1 M NaTFSI-FDMA with 1 wt % FEC, and 1 M NaTFSI-FDMA : MTFE (1 : 1 by volume) with 1 wt % FEC electrolytes. The radial distribution functions (RDF) data and MD snapshot revealed that 1 M NaTFSI-FDMA electrolyte displayed a characteristic contact-ion pair-rich structure (CIP, one TFSI À coordinating to one Na + ) (Figure S2a), where 2.67 FDMA and 0.96 TFSI À coordinating to one Na + (Figure S2b), demonstrating the weakly solvating FDMA solvent allowed a participation of TFSI À in the solvation sheath of Na + .…”

Hard‐Carbon Anodes for Sodium‐Ion Batteries: Recent Status and Challenging Perspectives

“…To date, the most used electrolyte are liquid electrolytes, they show the merits of high ionic conductivity and low resistance for high energy cells, but the potential risks of electrolyte leakage and flammability can't be ignored during application. [ 186 ] To solve these challenges and further improve the energy density of full cells, more and more attention has been paid to constructing solid‐state electrolytes, especially the polymer gel electrolyte composed of liquid electrolyte and the hosting polymer networks. [ 215 ] The preparation process is facile, while most of the organic, aqueous, and ionic liquid electrolytes can be used in this system.…”

“…Reproduced with permission. [ 186 ] Copyright 2021, WILEY‐VCH. e) Cycling performance of full cells at different being states.…”

“…To further promote the application fields of SIBs, many works have adjusted the electrode–electrolyte interphase by optimizing the electrolytes to build full cells with unique characters. [ 186,189 ] For instance, to enhance the low‐temperature properties of Na 3 V 2 (PO 4 ) 2 F 3 || hard‐carbon full cell, Deng et al [ 185 ] introduced a low‐concentration electrolyte (0.3 M NaClO 4 in EC:PC = 1:1 v v −1 with 5% FEC) to construct a weakly solvating structure, which endowed the cell a lower activation energy barrier and facilitates the process of Na + desolvation. This full cell exhibited a high capacity of 108.5 mAh g −1 under −25 °C, of which energy density was 400 Wh kg −1 (based on the active material of cathode) (Figure 16b).…”

“…Another challenge that hinders the development of full cells is the safety of the equipment, as most of the non‐flammable electrolytes are unsuitable for batteries. [ 190 ] To date, Yang et al [ 186 ] reported an electrolyte of 1.2 M sodium bis(fluorosulfonyl)imide dissolved in trimethyl phosphate: bis(2,2,2‐trifluoroethyl) ether: vinylene carbonate=1:1.5:0.15 to construct NVP|| hard carbon cells with stable cycling and nonflammable property simultaneously. The electrode/electrolyte interphases of the cell were well optimized by adjusting the solvation structure of the electrolyte through an intermolecular Hbond.…”