Hierarchical Ti₃C₂@TiO₂ MXene hybrids with tunable interlayer distance for highly durable lithium-ion batteries

To realize high-rate and long-term performance of rechargeable batteries, the most effective approach is to develop an advanced hybrid material with a stable structure and more reaction active sites. Recently, 2D MXenes have become an up-and-coming electrode owing to their high conductivity and large redox-active surface area. In this work, we firstly prepared Ti3C2 MXenes through the selective etching of silicon from Ti3SiC2 (MAX) using HF and an oxidant for highly durable lithium-ion batteries (LIBs). The interlayer distance of Ti3C2 MXenes can be controlled with the oxidizability of the oxidant and etching temperature. In addition, Ti3C2@TiO2 MXene hybrids with further expanded interlayer spacing were purposefully fabricated by a simple hydrothermal method. The hierarchical N-doped Ti3C2@TiO2 MXene hybrids show that the in situ synthesized nanoscale TiO2 particles are loaded homogeneously on the layered N-doped Ti3C2 surface. The interlayer distance of N-doped Ti3C2@TiO2 MXene can reach 12.77 Å when using HNO3 as the oxidant at room temperature. As an anode material, the N-doped Ti3C2@TiO2(HNO3-RT) hybrid displays a high reversible capacity of 302 mA h g-1 at 200 mA g-1 after 500 cycles and 154 mA h g-1 at 2000 mA g-1 after 1500 cycles, which indicates its long cycle lifetime and excellent stability in LIBs. This highly durable LIB anode performance is ascribed to synergetic contributions from the high capacitive contribution, high electrical conductivity, high-capacity of in situ formed nanoscale TiO2 and interlayer-expanded architecture of the N-doped Ti3C2@TiO2(HNO3-RT). This study provides a theoretical basis for the application of MXenes as high capacity anodes for advanced LIBs.