Non-flammable Gel Polymer Electrolyte for Enhancing the Safety and High-Temperature Performance of Lithium-Ion Batteries

As
the applications of lithium-ion batteries (LIBs) have expanded,
battery safety has emerged as a major concern because of the thermal
runaway of LIBs arising from the use of flammable liquid electrolytes
(LEs). Gel polymer electrolytes (GPEs) have been considered as potential
candidates to replace LEs and improve the thermal safety of LIBs.
In our study, a chemically cross-linked nonflammable GPE was synthesized
and used in an LIB. A cross-linking agent, spirocyclic pentaerythritol
diphosphate perfluorinated ether acrylate, comprising a phosphorus
moiety and a fluoroether chain, was designed and synthesized to prepare
a nonflammable cross-linked GPE. The obtained GPE effectively suppressed
the deleterious reactions of the LE and imparted nonflammable characteristics.
The pouch-type graphite/LiNi0.6Co0.2Mn0.2O2 cell with a nonflammable GPE delivered an initial discharge
capacity of 146.7 mAh g–1 with a capacity retention
of 71.1% after 300 cycles at 0.5 C and 55 °C. Moreover, the chemically
cross-linked GPE exhibited excellent dimensional and thermal stability,
which allowed for the safer operation of LIBs even under harsh conditions.
This work provides guidelines for designing nonflammable electrolyte
systems for advanced LIBs with high safety, enhanced thermal stability,
and good cycling characteristics at elevated temperatures.