Conductivity enhancement mechanism and application of NiCo-MOF hollow sphere electrode materials in lithium-ion batteries†

Abstract

Metal–organic frameworks (MOFs) are considered highly promising anode materials for lithium-ion batteries (LIBs) due to their unique physical and chemical properties. However, the low electrical conductivity of single-metal MOF materials limits their application in LIBs. To overcome this challenge, this work designed and synthesized a bimetallic NiCo-MOF material with a hollow spherical structure. Through a combination of theoretical and experimental methods, we explored the differences in conductive mechanisms between Ni-MOF and NiCo-MOF, as well as their electrochemical performance as anode materials for lithium-ion batteries. Specifically, the average electrical conductivity of NiCo-MOF is 0.058 mS cm⁻¹, which is 34 times that of Ni-MOF (0.0017 mS cm⁻¹). Density functional theory (DFT) calculations indicate that the increase in conductivity is due to the introduction of Co²⁺, which increases the electron transport pathways and significantly boosts carrier concentration. Compared to Ni-MOF, NiCo-MOF has 19 additional electrons at the Fermi level. This enhanced conductivity also results in a more significant electrochemical performance; under 2C conditions, NiCo-MOF maintains a specific capacity of 696.3 mA h g⁻¹ after 200 cycles, which is twice that of Ni-MOF (299.9 mA h g⁻¹). This work provides a potential strategy for improving the conductivity of MOF materials and their application in lithium-ion batteries.