Towards safer sodium-ion batteries via organic solvent/ionic liquid based hybrid electrolytes

Abstract

h i g h l i g h t sThe ionic liquid of the hybrid electrolytes improves the general safety. The cation solvation shell is modified with the composition of the electrolyte. The physical properties are relatively unaltered by addition of up to 20% of IL. Half-cells using hard carbon electrodes exhibit good capacities and capacity retentions. a b s t r a c tHybrid electrolytes aimed at application in sodium-ion batteries (SIB) consisting of an organic solvent mixture (EC:PC) and different ionic liquids (ILs); EMImTFSI, BMImTFSI, and Pyr 13 TFSI, and with the NaTFSI salt providing the Na þ charge carriers have here been extensively studied. The physico-chemical and electrochemical characterisation includes ionic conductivity, viscosity, density, cation coordination and solvation, various safety measures, and electrochemical stability window (ESW). Hybrid electrolytes with 10e50% of IL content were found to have ionic conductivities on par with comparable organic solvent based electrolytes, but with highly enhanced safety properties. A systematic Raman spectroscopy study of the cation coordination and solvation before and after electrolyte safety tests by ignition suggest that IL cations and TFSI remain stable when ignited while organic solvents are consumed. Finally, the solid electrolyte interphase (SEI) formed when using hybrid electrolytes has both better mechanical and electrochemical stability than the SEI derived from pure IL based electrolytes. For a half-cell with a hard carbon (HC) electrode and a hybrid electrolyte with a composition of 0.8 m NaTFSI in EC 0.45 :PC 0.45 :-Pyr 13 TFSI 0.10 encouraging results were obtained for IL based electrolytes e ca. 182 mAhg À1 at C/10 over 40 cycles.

Electrolytes, SEI Formation, and Binders: A Review of Nonelectrode Factors for Sodium‐Ion Battery Anodes

“…Regarding the effects of IL electrolytes with anode materials solely, Monti et al reported the use of a hybrid organic/IL electrolyte composed of EC 0.45 :PC 0.45 :Pyr 13 TFSI 0.10 in a half-cell with a hard carbon anode. [53] The addition of the organic solvent allowed the electrolyte to have a lower operational temperature, while the IL was able to provide stability at low operational voltages. The observed capacity in the half-cell at a current rate of C/10 was of 180 mA h g −1 , which is still respectable while not as high as hard carbon with traditional electrolytes.…”

Electrolytes for electrochemical energy storage

“…Surprisingly, compared to the active and dynamic research on electrode materials, research on electrolytes received relatively less attention. [13][14][15][16][17][18] Electrolyte is an indispensable constituent, liquid in most cases, in all types of EES devices and helps conduct electricity by means of the transportation of ions, but not electrons. Because the electrolyte is placed between, and in close interaction with the positive electrode (positrode) and…”

Electrochemical Behavior of PEDOT/Lignin in Ionic Liquid Electrolytes: Suitable Cathode/Electrolyte System for Sodium Batteries

“…[17] Moreover,c onducting polymers have been proven to be good electroactivem aterials for sodium batteries duet ot heir flexible structure to reversibly host Na ions. [17] Moreover,c onducting polymers have been proven to be good electroactivem aterials for sodium batteries duet ot heir flexible structure to reversibly host Na ions.…”

“…Sodium secondary batteries have gained great interest owing to the lower price and significantly greater abundance of sodiumc ompared to lithium.I midazolium-and pyrrolidinium-based ILs were studied as potentiale lectrolytes for sodium batteries, which demonstrated sodiumd eposition and dissolution with good efficiency. [17] Moreover,c onducting polymers have been proven to be good electroactivem aterials for sodium batteries duet ot heir flexible structure to reversibly host Na ions. [18] The goal of the presents tudy is to investigate the electrochemicalb ehavior of PEDOT/lignin biopolymers in as eries of imidazolium-and pyrrolidinium-based ILs.…”