Deciphering the lithium storage chemistry in flexible carbon fiber‐based self‐supportive electrodes

Abstract Flexible carbon fiber cloth (CFC) is an important scaffold and/or current collector for active materials in the development of flexible self‐supportive electrode materials (SSEMs), especially in lithium‐ion batteries. However, during the intercalation of Li ions into the matrix of CFC (below 0.5 V vs. Li/Li⁺), the incompatibility in the capacity of the CFC, when used directly as an anode material or as a current collector for active materials, leads to difficulty in the estimation of its actual contribution. To address this issue, we prepared Ni₅P₄ nanosheets on CFC (denoted CFC@Ni₅P₄) and investigated the contribution of CFC in the CFC@Ni₅P₄ by comparing to the powder Ni₅P₄ nanosheets traditionally coated on a copper foil (CuF) (denoted P‐Ni₅P₄). At a current density of 0.4 mA cm⁻², the as‐prepared CFC@Ni₅P₄ showed an areal capacity of 7.38 mAh cm⁻², which is significantly higher than that of the P‐Ni₅P₄ electrode. More importantly, theoretical studies revealed that the CFC has a high Li adsorption energy that contributes to the low Li‐ion diffusion energy barrier of the Ni₅P₄ due to the strong interaction between the CFC and Ni₅P₄, leading to the superior Li‐ion storage performance of the CFC@Ni₅P₄ over the pristine Ni₅P₄ sample. This present work unveils the underlying mechanism leading to the achievement of high performance in SSEMs.