Hierarchical conformal coating enables highly stable microparticle Si anodes for advanced Li-ion batteries

●A unique pancake-like Si composite featuring hierarchical coating is fabricated.●The prepared sample consists of an Li-Si-O inner layer and a graphene outer layer.●The Li-Si-O layer increases the mechanical property and ionic diffusion.●The graphene layer improves the electrode/electrolyte interfaces and electronic conductivity.●The Si@Li-Si-O@rGO anode exhibits superior overall electrochemical properties. Microsized silicon powders have great potential for high capacity anode materials in next-generation lithium ion batteries, because of the high gravimetric and volumetric energy densities, ease of mass production and low costs. However, large volume change and consequently rapid capacity fading upon lithiation and delithiation prevent its practical applications. Herein, we demonstrate an effective hierarchical conformal coating strategy for high-performance microsized Si anodes. The Si-based composites consist of an amorphous Li-Si-O inner coating layer and a graphene outer encapsulation layer, which are prepared by coupling reactive milling with electrostatic self-assembly. This unique hierarchical conformal coating structure not only strengthens the mechanical property (31.8 GPa for the elastic modulus) and promotes the ionic diffusion (2.03 × 10−10 cm2 s−1) of Si anode, but also effectively stabilizes the electrode/electrolyte interfaces and increases the electronic conductivity. As a result, a high reversible capacity (1450 mA⋅h g−1 at 0.1 A g−1), good cycling stability (97.7% of capacity retention from the 2nd to the 310th cycle at 0.5 A g−1), and high rate capability (703 mA⋅h g−1 at 5 A g−1) have been successfully achieved. These findings provide new insights into the improvement of electrochemical properties of microsized Si composite anodes for high-performance Li-ion batteries. [Display omitted] A pancake-like microsized Si composite featuring hierarchical conformal coating is successfully fabricated, which presents superior overall electrochemical properties as anode for next-generation Li-ion batteries.