SiOx Coated Graphite with Inorganic Aqueous Binders as High-Performance
Anode for Lithium-Ion Batteries
Abstract
Inorganic aqueous binders (IAB) are an emerging class of aqueous
binders. They offer exceptional physicochemical properties like
intrinsic ionic conductivity, high thermal stability
(>1000°C), and environmental benignity making them
attractive. In a previous study, we found that graphite anode shows
improved electrochemical performance with these binders as compared to
conventional PVDF binder for lithium-ion batteries (LIB). However, the
cyclic performance of graphite-IAB at a higher rate (e.g., 1C) showed a
declining trend. We attributed it to the poor binding strength between
graphite and IAB due to insufficient functional groups in graphite.
Therefore in this report, SiOx-based surface coatings of graphite are
employed to improve its rate capability with silicate-based IAB by
providing functional silicon oxide polymorphs on the coated graphite as
an intermediate layer. The nature and structural arrangement of these
coatings are investigated by tip-enhanced Raman spectroscopy (TERS),
X-ray photoelectron spectroscopy (XPS), and transmission electron
microscopy (TEM). Optimized SiOx-coated graphite (GS) with sodium
metasilicate binder leads to excellent cyclic stability with a capacity
retention of >90% at 20C for more than 4000 cycles. A high
specific capacity of >315 mAhg-1 at 2C, stable for over
1000 cycles, is achieved for GS with IAB. The improved performance of
the coated graphite is attributed to ameliorated binding with IAB as
well as stable solid electrolyte interphase. We propose inorganic
aqueous binders in combination with SiOx-coated graphite as an approach
to realize a stable anode for LIB.