Construction of TiP2O7 nanosheets/rGO hierarchical Flower-like heterostructures for superfast and ultralong lithiation/delithiation process

Abstract

Despite significant progress in lithium-ion batteries (LIBs), the commercialization and performance improvement of anode materials are impended by their inferior stability and sluggish kinetics. Herein, a modified strategy, involving the one-step solvothermal reaction and subsequent sintering process, is proposed to synthesize the TiP2O7/reduced graphene oxide (rGO) microsphere, which serves as a Li-ion storage material. Profiting from the stable chemical characteristics of pyrophosphate and unique structure framework, the TiP2O7/rGO composite exhibits extraordinary electrochemical performance, especially in long-term cycling (over 4000 loops at a ultrahigh rate of 2000 mA g−1). In this hierarchical architecture, the three-dimensional TiP2O7 microflowers are intimately wrapped by the interlinked rGO nanosheets, constructing a well-designed conductive network with favorable electrochemical kinetics. Moreover, the dynamic changes of impedance and phase evolutions are further verified by in-situ electrochemical impedance spectroscopy (EIS) measurement. Based on the detailed analysis of kinetic features, enhanced pseudocapacitance effect could boost the rate of Li-ion transferring, leading to the superior rate capability (460.7, 372.1, 327.0, 280.9, 235.6, 176.8, 127.5 mAh g−1 at 40, 80, 200, 400, 800, 2000, 4000 mA g−1). This work provides an effective strategy to realize high performance of pyrophosphate-based materials for Li-ion storage.