A Multifunctional Surface Modifier Capable of Stabilizing 5.0 V Graphite Cathode via Reinforced Mechanical Strength and Preferential Anion Adsorption

Abstract With the ever‐increasing demand for high power and high energy batteries, extensive researches devote to high voltage cathode materials. Graphite cathode‐based dual‐ion batteries (DIBs) possess the unique advantages of high working voltage (≈4.5−5.0) and high power, but still suffer from low coulombic efficiency and poor long‐term stability mainly resulted by the serious oxidative decomposition of electrolytes and significant structural deterioration of graphite cathode. From the perspectives of simultaneously reinforcing the mechanical strength of graphite cathode and suppressing the decomposition of electrolytes via a cathode/electrolyte interphase (CEI), polyacrylic acid (PAA) is adopted as the surface modifier of natural graphite (NG). The mechanical stability of graphite cathode is significantly improved by virtue of the bonding interaction between PAA and binder, which is validated through both theoretical calculation and experimental observation. In addition, PAA contributes to the formation of a LiF‐rich and homogeneous CEI through the preferential adsorption of anions, and effectively mitigates the cointercalation and decomposition of solvent. As the cathode material of DIBs, NG@PAA manifests fast charge/discharge capability and outstanding capacity retention of 73.9% after 8000 cycles. This work provides a surface modification strategy for optimizing the performance of electrode materials from multiple perspectives.