N-doped carbon boosted high-rate and stable lithium storage for TiP2O7-based anode

The three-dimensional framework for lithium storage endows TiP 2 O 7 with excellent stability and considerable capacity. However, its practical application is hindered by poor electrical conductivity and an unclear understanding of its structural evolution. Herein, we present a nitrogen-doped carbon-coated TiP 2 O 7 composite prepared by a straightforward and scalable surface modification strategy, which exhibits superior rate capability compared to previous reports. Specifically, it achieves specific capacities of 435, 341, and 263 mA h g −1 at current densities of 2, 5, and 10 A g −1 , respectively. Kinetic analysis confirms that the nitrogen-doped carbon coating on TiP 2 O 7 surface significantly accelerates the interfacial charge transfer, leading to a dominant pseudocapacitive behavior. Importantly, ex-situ transmission electron microscopy characterization reveals that the TiP 2 O 7 in the composite evolves into homogeneous nanocrystals after 100 cycles at a low current density of 0.2 A g −1 . By contrast, despite the TiP 2 O 7 transforming into nanocrystals with inconsistent sizes and reduced crystallinity after 1000 cycles at a high current density of 1 A g −1 , the effective coating of N-doped carbon preserves the capacity of the anode at up to 462.6 mA h g −1 . These findings suggest that this universal strategy can significantly enhance the performance of TiP 2 O 7 -based anode materials for lithium-ion batteries. Graphical abstract