A synergistic CoO/MXene heterostructure anode with facilitated interfacial charge transfer for high-rate micro...

Micro lithium-ion batteries (MLIBs) are promising power devices for miniaturized intelligent terminals, but are limited by low energy density and poor cycling stability. Among potential anodes, cobalt oxide (CoO) offers a high theoretical capacity while suffering from low electrical conductivity and structural degradation. Herein, we propose a synergistic 0D-2D CoO/MXene heterostructure anode with uniformly anchored CoO nanoparticles on Ti₃C₂ MXene nanosheets, enabling facilitated interfacial charge transfer and high-rate performance for advanced MLIBs. In this architecture, the nanosized CoO particles alleviate pulverization, shorten ion diffusion pathways, and amplify active sites, while the conductive, robust MXene framework facilitates electron conduction, ion transport, and accommodates mechanical strains. The intimate CoO-MXene vdW interface further enables synergistic charge coupling, leading to accelerated interfacial kinetics and enhanced electrochemical stability. The heterostructure is fabricated by a facile solvothermal strategy involving electrostatic adsorption of Co²⁺, MXene-guided nucleation, and oriented growth, which effectively suppresses CoO aggregation and MXene oxidation. Interfacial characterizations verify noncovalent vdW coupling, confirming intimate atomic contact and excluding covalent bonding features. As a result, the CoO/MXene 0D-2D van der Waals heterostructure achieves an ultrahigh reversible capacity of 1282.3 mAh g^-1 after 100 cycles. It also exhibits an outstanding rate capacity of 731.7 mA h g^-1 at 0.8 A g^-1 for over 300 cycles. Notably, when the current density is returned to 0.1 A g^-1 after high-rate cycling, the capacity recovers to 1111.6 mAh g^-1, demonstrating remarkable structural integrity and electrochemical reversibility. Furthermore, density functional theory (DFT) calculations analyzed that the MXene-CoO heterostructure enhances conductivity through increased density of states near the Fermi level, optimizes interfacial charge-transfer kinetics to strengthen Li adsorption, and lowers Li⁺ diffusion barriers, collectively contributing to the improved rate performance and cycling stability. This work establishes a novel and controllable strategy for constructing 0D-2D vdW heterostructures and provides mechanistic insights into structure-property relationships, offering a practical pathway toward high-performance anodes for MLIBs applications.