Iron-Doping-Induced Phase Transformation in Dual-Carbon-Confined Cobalt Diselenide Enabling Superior Lithium Storage

Transition metal chalcogenides (TMCs) have been investigated as promising anodes for high-performance lithium-ion batteries, but they usually suffer from poor conductivity and large volume variation, thus leading to unsatisfactory performance. Although nanostructure engineering and hybridization with conductive materials have been proposed to address this concern, a better performance toward practical device applications is still highly desired. Herein, we report an iron-doping-induced structural phase transition from pyrite-type (cubic) to marcasite-type (orthorhombic) phases in porous carbon/rGO-coupled CoSe₂. The dual-carbon-confined orthorhombic CoSe₂ ( o-Fe _xCo_{1- x}Se₂@NC@rGO) composites exhibit dramatically enhanced lithium storage performance (920 mAh g^-1 after 1000 cycles at 1.0 A g^-1) over cubic CoSe₂-based composites ( c-CoSe₂@NC@rGO). The combined experimental studies and density functional theory calculations reveal that this doping-induced structural phase transformation strategy could create a favorable electronic structure and ensure a rapid charge transfer. These results demonstrate that the phase-transformation engineering may provide another opportunity in the design of high-performance TMC-based electrodes.