Understanding the Electrochemical Compatibility and Reaction Mechanism on Na Metal and Hard Carbon Anodes of PC-Based Electrolytes for Sodium-Ion Batteries

Abstract

Electrolytes as an important part of sodium-ion batteries have a pivotal role for capacity, rate, and durability of electrode materials. On account of the high reduction activity of sodium metal with organic solvents, it is very important to optimize the electrolyte component to realize high stability on Na metal and hard carbon anodes. Herein, chemical and electrochemical stability of propylene carbonate (PC)-based electrolytes on sodium metal and hard carbon anodes is investigated systematically. The results demonstrate that whether using NaClO4 or NaPF6, the PC-based electrolytes are not stable on Na metal, but adding of FEC can immensely enhance the stability of the electrolyte because of the compact solid electrolyte interphase film formed. The electrolytes containing FEC also exhibit high electrochemical compatibility on hard carbon anodes, showing high reversible capacity and excellent cycling performance. A reaction mechanism based on the Na+ induction effect is proposed by spectrum and electrochemical measurements. This study can provide a new insight to optimize and develop stable PC-based electrolytes and be helpful for understanding the other electrolyte systems.

High‐Performance Gel Polymer Electrolyte Based on Chitosan–Lignocellulose for Lithium‐Ion Batteries

“…The R ct is the impedance crossing phase from the anode to the SEI, which inhibits the Li/Li + redox reaction. [66][67][68][69][70] As shown in Table 4, R i of all GPEs increases with days, and finally stabilizes after 30 days. The thickness of the SEI increases with time and eventually stabilizes.…”

“…The R p , in the process of charging and discharging, forms by chemical reaction between electrolyte and anode (Li) with time, and it is called solid electrolyte impedance (SEI) in LIBs. The R ct is the impedance crossing phase from the anode to the SEI, which inhibits the Li/Li + redox reaction …”

Role of electrolyte in stabilizing hard carbon as an anode for rechargeable sodium-ion batteries with long cycle life

“…Solvent and salt (from the electrolyte) decomposition are the origin of these chemical species. PC can decompose through a ring opening reaction by single electron nucleophilic attack pathway to form a linear alkyl carbonate [47] . This molecule can then decompose into oxygen and propylene, which react with PC to produce polyesters.…”

Achieving long-cycling sodium-ion full cells in ether-based electrolyte with vinylene carbonate additive

“…Positive effects of vinyl ethylene carbonate (VEC) and fluoroethylene carbonate (FEC) as additives for Nametal and hard carbon anodes in carbonate-based electrolytes were identified. Cao et al pointed out that FEC-derived SEI layers on Na metal and hard carbon anodes are compact and dense which could suppress the decomposition of propylene carbonate (PC) efficiently [37]. Intermetallic alloys, such as Ge, Sb, and Sn, and their composites use FEC as an additive into NaClO 4 -PC induce to form a robust and thin SEI layer enabling a facile Na-ion transfer.…”