Electrolyte-Resistant Dual Materials for the Synergistic Safety Enhancement of Lithium-Ion Batteries

Safety issues associated with lithium-ion
batteries are of major
concern, especially with the ever-growing demand for higher-energy-density
storage devices. Although flame retardants (FRs) added to electrolytes
can reduce fire hazards, large amounts of FRs are required and they
severely deteriorate battery performance. Here, we report a feasible
method to balance flame retardancy and electrochemical performance
by coating an electrolyte-insoluble FR on commercial battery separators.
By integrating dual materials via a two-pronged mechanism,
the quantity of FR required could be limited to an ultrathin coating
layer (4 μm) that rarely influences electrochemical performance.
The developed composite separator has a four-times better flame retardancy
than conventional polyolefin separators in full pouch cells. Additionally,
this separator can be fabricated easily on a large scale for industrial
applications. High-energy-density batteries (2 Ah) were assembled
to demonstrate the scaling of the composite separator and to confirm
its enhanced safety through nail penetration tests.