CoP Quantum Dots Embedded in Carbon Polyhedra through Co―P―C Bonding Enabling High-Energy Lithium-Ion Capacitors

Phosphides with high theoretical capacity are considered ideal anode materials for lithium-ion capacitors (LICs), but poor electronic conductivity as well as unsatisfied cyclic stability limits the performance of the phosphides. Here a covalently bonded CoP@C heterostructure is reported, which consists of 5 nm CoP quantum dots (QDs) like pomegranate seeds pinned in carbon polyhedron through interfacial CoPC bonding. The ultrafine size of CoP QDs provides more reactive sites and a shorten electrons/ions diffusion path, boosting the specific capacity. The CoPC bond induces the energy band variation of CoP and increases the interfacial charge density, bringing about fast kinetics. Besides, the CoPC bond introduces a robust pining effect among CoP QDs and carbon polyhedra, greatly improving the structure stability of 5 nm CoP QDs. The CoP@C heterostructure electrode exhibits high capacity (nearly 1000 mAh g-1) and superior cycling stability. It is worth noting that a prototyped LIC full-cell of YP80//CoP@C presents an impressive high energy density of 172 Wh kg-1 and a power density of 10.8 kW kg-1. Moreover, the LIC possesses an ultra-long life, retaining 80% after 20,000 cycles. This study offers an effective design for phosphides achieving fast kinetics and superior structure stability through an interfacial bonding approach. A CoP@C heterostructure is prsented in which 5 nm-CoP quantum dots (QDs) are pinned in a carbon polyhedron through interfacial CoPC bonding. CoP QDs brings more reactive sites and reduces ions diffusion length. The CoPC bond promotes interfacial charge density and enhances structure duration. Consequently, a lithium-ion capcitor presents high energy density of 172 Wh kg-1 and superior cycling performance. image