A Doping Protonation Strategy for the Highly Elastic Foam-Structured Hydrogels to Boost the Performance of SiOx Anodes

Abstract

Silicon oxide (SiO_x) is a promising high-capacity anode material of lithium-ion batteries (LIBs), but the inferior electrical conductivity and apparent bulk effect during cycling still seriously hinder its practical application. In this work, poly(acrylic acid) (PAA) is used as a counterbalance ion in doped protonated polyaniline (PANI), which greatly increases the solubility of PANI in water to successfully design PAA@PANI@SA (N-PPS) hydrogels as the binder of SiO_x anode with entangled chain-linked foam structure. The high-density electrostatic interactions between the PAA and PANI chains act as a dynamic link to initiate chain entanglement, providing N-PPS with ultrahigh mechanical strength (maximum peel strength of 0.472 N) and fast self-healing properties. After 300 cycles under different test conditions, the N-PPS electrode capacity remained at 1200 mAh g^–1, and the battery works stably. A series of molecular dynamics tests demonstrate that N-PPS has excellent ion transport properties (D_Li⁺ = 7.2 × 10^–17) and enhanced conductivity (2.12 × 10^–3 S cm^–1). Quantitative simulations validate that the sufficient ion channels inside the N-PPS entangled chain foam structure can effectively reduce the energy barrier of lithium-ion diffusion, indicating the inherent advantages of the N-PPS binder and the promising prospects for application in the SiO_x anode of LIBs.