Phosphorylated Chitosan/Polyacrylic Acid Cross‐Linked Binder Enabling Silicon Anodes with High Electrochemical Stability and Intrinsic Thermal Safety

Silicon (Si) anodes show broad application prospects given the current high demand for high-energy-density batteries. However, its application is restricted by volume expansion during cycling. Meanwhile, higher energy density also brings greater risks. To tackle these issues, the water-soluble flame retardant additive phosphorylated chitosan (PCS) was introduced into the commonly used polyacrylic acid (PAA) binder system, resulting in the design of a cross-linked binder system with both thermal safety and electrochemical stability. PCS and PAA cross-link through hydrogen bonds, which restricts the expansion of nano silicon to a certain extent. The battery using it as a binder still has a reversible capacity of 1148.3 mAh g^-1 after 200 cycles. In addition, PCS also inhibits the pyrolysis of PAA, increases the temperature at which the binder decomposes to produce combustible gases, and reduces the number of combustible gases generated, thereby enhancing the fire safety of the binder. Moreover, its water solubility also reduces the use of organic solvents, making it more environmentally friendly. This research work introduces a novel method for realizing a binder with electrochemical cycling stability and high thermal safety, addressing the key challenges in the pursuit of sustainable energy solutions.