Heterogeneous interface containing selenium vacancies space-confined in double carbon to induce superior electronic/ionic transport dynamics for sodium/potassium-ion half/full batteries

Abstract

The exploration of suitable anode materials to overcome key issues of electrode volume fluctuation and sluggish electronic/ionic transport dynamics caused by the large radius of sodium/potassium ions is an urgent need for Na+/K+ storage. Herein, a fascinating FeSe2/CoSe2/C (FCSe@C) containing heterostructure and special selenium vacancies is confined within the void space inside carbon sphere by using a combination strategy of melting diffusion and selenization. Surface chemical states and structural analyses demonstrate that the as-obtained FCSe@C@void@C is constructed by an internal FCSe@C core and an external carbon sphere. The rational design of double carbon architectures with large interior void space can not only promote the electrical conductivity but also protect the integrity of selenide during cycling. As a result, FCSe@C@void@C electrode delivers the prominent energy storage properties in half/full SIBs and PIBs. More importantly, the thorough understanding of heterogeneous interfaces on the improved performance is explicitly interpreted by combining experimental and theoretical analysis. This work demonstrates a new idea to construct phase interface and internal reserved void structure of transition metal selenides, and provide an effective method for the design and optimization of other advanced anode materials for secondary batteries and other energy storage systems.