Si-based
electrodes offer exceptionally high capacity and energy
density for lithium-ion batteries (LIBs),but suffer from poor structural
stability and electrical conductivity that hamper their practical
applications. To tackle these obstacles, we design a C/polymer bilayer
coating deposited on Si-SiO
x
microparticles. The inner C coating is used to improve electrical
conductivity. The outer C-nanoparticle-reinforced polypyrrole (CNP-PPy)
is a polymer matrix composite that can minimize the volumetric expansion
of Si-SiO
x
and enhance
its structural stability during battery operation. Electrodes made
of such robust Si-SiO
x
@C/CNP-PPy microparticles exhibit excellent cycling performance:
83% capacity retention (794 mAh g–1) at a 2 C rate after more than 900 cycles for a coin-type half cell,
and 80% capacity retention (with initial energy density of 308 Wh
kg–1) after over 1100 cycles for a pouch-type full
cell. By comparing the samples with different coatings, an in-depth
understanding of the performance enhancement is achieved, i.e., the
C/CNP-PPy with cross-link bondings formed in the bilayer coating plays
a key role for the improved structural stability. Moreover, a full
battery using the Si-SiO
x
@C/CNP-PPy electrode successfully drives a car model, demonstrating
a bright application prospect of the C/polymer bilayer coating strategy
to make future commercial LIBs with high stability and energy density.
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