Improving the Performance of Silicon-Based Negative Electrodes in All-Solid-State Batteries by In Situ Coating with Lithium Polyacrylate Polymers

In all-solid-state batteries (ASSBs), silicon-based negative electrodes have the advantages of high theoretical specific capacity, low lithiation potential, and lower susceptibility to lithium dendrites. However, their significant volume variation presents persistent interfacial challenges. A promising solution lies in finding a material that combines ionic-electronic conductivity, stable physicochemical properties, and adhesive characteristics. Poly(acrylic acid) (PAA) is widely used in liquid-state batteries due to its superior properties compared to polyvinylidene fluoride (PVDF). In this study, silicon particles were coated with varying concentrations of PAA and LiPAA using an in situ liquid-phase coating method to form electrode sheets. The experimental and analytical results revealed significant trends in the impact of different additive concentrations on the electrochemical performance, with 1.0 wt % LiPAA showing notable improvements in Coulombic efficiency, rate capability, and long-term cycling stability. The assembled all-solid-state batteries exhibited a high initial discharge capacity of 3200 mAh/g, with a capacity retention of 81.9% after 300 cycles at 0.3 C, and a stable discharge capacity of 1300 mAh/g at a 2 C rate. A rapid and efficient in situ liquid-phase coating method for LiPAA was developed and confirmed through FTIR, XRD, and TEM characterization. SEM and XPS analyses demonstrated that LiPAA encapsulation effectively alleviates interfacial issues. This study demonstrated for the first time that an appropriate amount of LiPAA coating on silicon particles can mitigate the interfacial challenges caused by the volume expansion of silicon-based negative electrodes. These findings improve electrochemical performance and promote the application of silicon-based negative electrodes in all-solid-state batteries.