Designing a Dual-Functional Binder for High-Energy-Density Silicon Anodes in Lithium-Ion Batteries

The practical application of silicon (Si) anodes is limited by the large volume change, unstable solid electrolyte interface (SEI), and low intrinsic conductivity. To address these challenges, we designed Prelithiated poly(acrylic acid)-boric acid (LiPAA-BA) a multifunctional binder with a three-dimensional (3D) network structure, using a combined prelithiation and cross-linking strategy. LiPAA-BA showed a high interfacial adhesion force (4.8 N), which was improved by about 2 times compared to conventional PAA due to the increased number of contact sites with the silicon and the 3D network structure. As a result, the Si@LiPAA-BA electrode achieved an excellent capacity retention of 100% after 300 cycles and volume expansion was effectively suppressed. LiPAA-BA contains a Li⁺ conducting group, which increases the Li⁺ diffusion coefficient (D_Li⁺) compared to PAA by a 1.6 times and enhances the rate capability. The cross-linker (BA) adopted in this study contains boron atoms with electron-deficient properties, which enabled the formation of a stable SEI layer on the silicon surface through interaction with anions in the electrolyte. A full cell using a SiO_x@C anode with a LiPAA-BA and an LFP cathode showed 64.89% capacity retention at 50 cycles, demonstrating potential for practical application.