Ti3C2Tx/Ni5P4/NiP2 Double-Heterojunction Anodes With Fluoride-Free Interfacial Engineering for High-Rate and Ultrastable Lithium Storage.

Transition metal phosphides (TMPs) are promising lithium-ion battery anodes but are hindered by severe volume expansion and poor cycling stability. To address these challenges, we report a fluoride-free strategy combining Lewis acidic molten salt etching and in situ phosphorization to grow biphasic Ni5P4/NiP2 nanoparticles uniformly on Ti3C2Tx MXene, forming a Ti3C2Tx/Ni5P4/NiP2 double-heterostructure. This approach avoids toxic HF, achieves simultaneous MXene exfoliation and active material anchoring, and establishes robust Ti-O-Ni/Ti-P interfacial bonds that are expected to facilitate intimate contact and efficient charge transfer, thereby effectively maintaining structural integrity during prolonged cycling and promoting the absorption and diffusion of lithium ions. As a result, the composite delivers outstanding rate capability (329.1 mAh g-1 at 5.0 A g-1) and long-term cycling stability (487.1 mAh g-1 after 600 cycles at 1 A g-1), significantly outperforming Ti3C2Tx/Ni2P composite and pristine Ti3C2Tx. This work provides a fluorine-free and scalable route for MXene/TMP heterostructures, offering mechanistic insights into interface-engineered electrodes for next-generation energy storage systems.