Functional Binder with Enhanced Chemical Adsorption for Black Phosphorus Anode in Lithium‐Ion Capacitors

Abstract Black phosphorus (BP) has been recognized as an ideal anode material for fast‐charging lithium (Li)‐ion capacitors (LICs) due to its high theoretical capacity (2596 mAh g −1 ), appropriate lithiation potential (0.7 V vs Li + /Li) and fast ion diffusion capability. However, large volume change and soluble polyphosphides (Li x Ps)‐based intermediates during charging‐discharging process seriously deteriorate cycling performance. To address the aforementioned issues, an elaborated design is reported on the binder for BP electrode. The ‐NH 2 polar functional group in grafted chitosan (GCS) binder presents strong chemical anchoring effect for both BP and soluble Li x Ps, achieving superior adhesion force and Li x Ps constraining capability for enhanced structure integrity of BP electrode. In addition, GCS exhibits strong Li‐ion binding energy that promotes the Li‐ion adsorption at electrode level, leading to a boosted cycle life for BP. As a result, the graphene (G) incorporated BP electrode using GCS binder shows specific capacity of 997.6 mAh g −1 after 400 cycles at 1 A g −1 . This study unravels the crucial role of functional groups for binder in high‐performance BP electrode.