Vacancy engineering in Co-doped CuS_1-x with fast Electronic/Ionic migration kinetics for efficient Lithium-Ion...

Slow Li ion diffusion kinetics and disordered migration of electrons are two most crucial obstacles to be resolved in electrode material design for higher rate capability of Li-ion batteries. Herein, the Co-doped CuS_1-x with abundant high active S vacancies is proposed to accelerate the electronic and ionic diffusion during the energy conversion process, because contraction of Co-S bond can cause the expansion of atomic layer spacing, thus promoting the Li ion diffusion and directional electron migration parallel to the Cu₂S₂ plane, and also induce the increasing of active sites to improve the Li⁺ adsorption and electrocatalytic conversion kinetics. Especially, the electrocatalytic studies and plane charge density difference simulations demonstrate that electron transfer near the Co site is more frequent, which is conducive to more rapid energy conversion and storage. Those S vacancies formed by Co-S contraction in CuS_1-x structure obviously increase Li ion adsorption energy in Co-doped CuS_1-x to 2.21 eV, higher than the 2.1 eV for CuS_1-x and 1.88 eV for CuS. Taking these advantages, the Co-doped CuS_1-x as anode of Li-ion batterie shows an impressive rate capability of 1309 mAh·g^-1 at 1A g^-1, and long cycling stability (retaining 1064 mAh·g^-1 capacity after 500 cycles). This work provides new opportunities for the design of high-performance electrode material for rechargeable metal-ion batteries.