Graphitic Carbon Quantum Dots on 3D MXene Hollow Microspheres for Lithium-Ion Storage

Three-dimensional (3D) MXene architectures are promising anode materials for lithium-ion batteries (LIBs) because they alleviate nanosheet restacking, enhance ion transport, and buffer volume changes. However, their electrochemical performance is still restricted by narrow Li+ transport channels, insufficient utilization of active surfaces, and suboptimal conductivity. Herein, we report a confined catalytic carbonization strategy that integrates highly graphitized carbon quantum dots (CQDs) with 3D MXene hollow microspheres to address these challenges. Cationic poly(lactic acid) (c-PLA) microspheres were employed as sacrificial templates and electrostatically assembled with MXene nanosheets to form c-PLA@MXene precursors. Subsequent pyrolysis decomposed the c-PLA and generated CQDs in situ, resulting in honeycomb-like hollow MXene microspheres decorated with CQDs on both surfaces and within interlayer regions. The CQDs served as conductive nanospacers to expand MXene interlayer spacing, suppress nanosheet restacking, reduce charge-transfer resistance, and simultaneously reinforce the framework to buffer volume fluctuations. Benefiting from these synergistic effects, the CQDs/3D-MXene anode delivered a reversible capacity of 517.7 mAh/g at 0.3 C, and maintained 218.4 mAh/g after 1000 cycles at 5 C. This study provides an effective strategy for integrating graphitic nanocarbons with MXene frameworks to achieve high-rate and durable LIB anodes.