Designing boron and hydroxyl-functionalized 3D crosslinked binder for enhancing high-energy-density silicon anode of lithium-ion batteries

초록

Silicon (Si) is a candidate anode for high-energy-density lithium-ion batteries due to its higher theoretical capacity (4200 mAh g-1) than graphite (372 mAh g-1). However, Si suffers rapid capacity fading owing to large volume changes and excessive solid electrolyte interphase (SEI) layer during repeated lithiation/delithiation. The design of the binder plays an important role in preventing such volume changes over a long cycle life. This study uses a crosslinked polymer composed of poly (acrylic acid) (PAA) and boric acid (BA) with the electron-deficient boron with the remaining hydroxyl groups (PBH) as a Si-based anode binder. The crosslinked PBH binder provides a robust electrode with improved adhesive strength at an optimized ratio, which effectively fixes Si particles and forms a LiF-rich SEI that can promote rigidity and ion conduction while suppressing the volume expansion of Si. The Si anode with the PBH binder achieves a high capacity of 2275 mAh g-1 after 150 cycles, with an average Coulombic efficiency of 98.8 % and high-capacity retention of 88.85 %. A LiNi0.6Co0.2Mn0.2O2 (NCM622)||Si cell is shown to withstand 100 cycles and exhibit improved retention. The crosslinked polymer derived from electron-deficient components is a promising Si binder for high-energy and high-stability lithium-ion batteries.

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