In situ construction of a MOF-derived carbon-encapsulated LiCoO2 heterostructure as a superior cathode for elevated-voltage lithium storage: from experimental to theoretical study

Abstract

Lithium cobalt oxide (LiCoO₂) is a promising cathode material for lithium ion batteries (LIBs). LiCoO₂ achieves merely half of its theoretical specific capacity for commercial applications. Its intrinsic issues lead to significant structural instability and severe degradation of electrochemical performance. Herein, a strategy for a surface-modified LiCoO₂ heterostructure by in situ metal–organic framework (MOF)-derived carbon-coating is proposed. The carbon-coated layer can not only reduce direct contact between the LiCoO₂ bulk and electrolyte, but boost the electrochemical conductivity and strain structural distortion during lithiation/delithiation, further facilitating prolonged cyclability and distinguished rate performance. Moreover, the annealing temperature effect of fabricating such LCO@C electrodes was investigated systematically. N-doped LCO@C-700 delivered prolonged cycling stability (gravimetric/areal capacity of 171.1 mA h g⁻¹/4.2 mA h cm⁻² at 1C after 200 cycles) and superior rate capability (high capacity of 150.3 mA h g⁻¹ even at a harsh current density of 10C) in the voltage range of 3.0–4.5 V. Density functional theory (DFT) calculations synchronously showed the electronic properties and Li-vacancy diffusion pathway of heterostructured N-doped LCO@C cathode material. These results indicate that electron-density charges, boosted electronic conductivity, and low energy barriers contributed to much faster lithium-ion storage kinetics of LCO@C particles than those of sole LCO. Our proposed in situ MOF-derived carbon-encapsulated strategy for cathode materials provides an innovative perspective and avenue for design of MOF-derived surface-modified heterostructure materials for LIBs.