Cobalt–Nickel Cyano Coordination Polymer-Derived Square CoSe2@NiSe2 Nanosheets for Advanced Na+/K+ Batteries

Sodium-ion batteries are receiving more and more attention due to their low cost and abundant sodium storage capacity, and are considered to be a promising alternative to lithium-ion batteries. A large number of studies have shown that constructing heterostructures are considered an effective strategy to solve the hysteresis problem of electronic and ion dynamics in sodium-ion battery anode materials. Herein, a nickel–cobalt bimetallic coordination polymer (NiCoCP) was synthesized using a coprecipitation method, and a CoSe₂@NiSe₂ cross-stacked structure was obtained through high-temperature carbonization and selenization processes. CoSe₂@NiSe₂ has a unique heterostructure and carbon film, which synergistically increases a large number of adsorption sites and alleviates the diffusion energy barrier, thereby improving the rapid diffusion kinetics of Na⁺ ions. It has superior rate performance and long-lasting cycle life. For sodium-ion batteries (SIBs), the specific capacity of CoSe₂@NiSe₂ is around 460 mA h g⁻¹ after 400 cycles at 1.0 A g⁻¹. For potassium-ion batteries (PIBs), CoSe₂@NiSe₂ also exhibits excellent cycling stability, maintaining a specific capacity of 160 mA h g⁻¹ after 700 cycles at 1.0 A g⁻¹. This study provides a new way to prepare metal selenide heterostructure as the promising anode material for SIBs.