Flame-retardant quasi-solid polymer electrolyte enabling sodium metal batteries with highly safe characteristic and superior cycling stability
flame-retardant, quasi-solid polymer electrolyte, highly safe characteristic, sodium metal batteries, long-term cycling stability
Conventional liquid electrolytes based sodium metal batteries suffer from severe safety hazards owing to electrolyte leakage, inflammability and dendritic sodium deposition. Herein, we report a flame-retardant quasi-solid polymer electrolyte with poly(methyl vinyl ether-alt-maleic anhydride) (P(MVE-alt-MA)) as host, bacterial cellulose (BC) as reinforcement, and triethyl phosphate/vinylene carbonate/sodium perchlorate (TEP/VC/NaClO4) as plasticizer for highly safe sodium metal batteries. The as-obtained quasi-solid polymer electrolyte exhibits superior flame retardancy (self-extinguish within 1 s), complete non-leakage property and wide electrochemical windows (4.4 V). More importantly, Na3V2(PO4)3/Na metal batteries using such polymer electrolyte delivers superior long-term cycling stability (84.4% capacity retention after 1000 cycles) which is significantly better than that (only 2% after 240 cycles) of liquid electrolyte. In addition, this flame-retardant quasi-solid polymer electrolyte provides favorable cycle performance (80.2% capacity retention after 70 cycles at 50 oC and 84.8% capacity retention after 50 cycles at −10 oC) for Na3V2(PO4)3/Na metal batteries. And this battery also displayed a normal charge/discharge property even at −15 oC. These fascinating cycle properties are mainly ascribed to the effective protective layers formed on Na3V2(PO4)3 cathode and sodium metal anode. More thorough investigation elucidates that such flame-retardant quasi-solid polymer electrolyte plays a multifunctional role in the advanced sodium metal batteries: (1) Being involved in the formation of a favorable cathode electrolyte interface (CEI) to inhibit the dissolution of vanadium and maintain the structure integrity of the Na3V2(PO4)3; (2) Participating in building a stable solid electrolyte interface (SEI) to suppress the growth of Na dendrites; (3) Integrating flame-retardance into polymer sodium batteries to enhance flame-resistance, eliminate electrolyte leakage, and thus improve safety of sodium batteries. Based on these results, we further assembled Na3V2(PO4)3/MoS2 pouch cell which can withstand harsh conditions (bended or cut off a corner), confirming the obtained polymer electrolyte with superior non-leakage property. In all, these outstanding characteristics would endow this flame-retardant quasi-solid polymer electrolyte a very promising candidate for highly-safe sodium metal batteries.
Tsinghua University Press
Jinfeng Yang,Min Zhang,Zheng Chen,Xiaofan Du,Suqi Huang,Ben Tang,Tiantian Dong,Han Wu,Zhe Yu,Jianjun Zhang,Guanglei Cui, Flame-retardant quasi-solid polymer electrolyte enabling sodium metal batteries with highly safe characteristic and superior cycling stability. NanoRes.2019, 12(9): 2230–2237