Water-Soluble Polymer Assists Multisize Three-Dimensional Microspheres as a High-Performance Si Anode for Lithium-Ion Batteries

We report a clean and easy way to tackle the challenges of large-scale applications of silicon (Si) anodes for lithium-ion batteries. Using an aqueous solution of water-soluble polymer carboxymethyl chitosan and nanosilicon as a precursor, multisize three-dimensional (3D) microspheres as a silicon anode material is fabricated by one-step spray-drying. The effective functional groups, viscoelasticity, and hydrophilicity of polymers are retained, which can prevent the agglomeration of nanoparticles, enhance the internal binding force of the secondary particles, buffer volume expansion, promote the formation of a stable solid electrolyte interface (SEI) film, and maintain electrode integrity. Accordingly, when the mass ratio of Si/polymer reaches 4:1, the compound exhibits a reversible capacity of 1484 mAh g–1 and 75% capacity retention after 100 cycles. Silicon and polymer can be combined effectively via spray-drying, so that the electrode has good cycle stability (930 mAh g–1 after 300 cycles at 1 A g–1), excellent rate performance (871 mAh g–1 at 4 A g–1), and high initial Coulombic efficiency (80%).