Key design considerations for synthesis of mesoporous alpha-Li3V2(PO4)(3)/C for high power lithium batteries

Abstract

In this article, we propose key design criteria to synthesis carbon coated α-Li3V2(PO4)3 positive electrode material for high power lithium batteries. A facile and scalable one-pot soft template method is adopted to synthesize α-Li3V2(PO4)3/C (LVP/C), which exhibits unique morphology of micron-size mesoporous secondary particles comprising interconnected primary nanoparticles showing good storage and rate performances with long cycle life. This cathode material displays high discharge capacities of 178, 90 and 59 mAh.g−1 at 0.1C, 30C and 80C, respectively. The mesoporous LVP/C with a 3D lithium diffusion network exhibits better rate performance (90 mAh.g−1 at 30C) as compared to the known phosphate, silicate or oxide cathode materials for lithium-ion batteries (LIBs). In addition, LVP/C electrode material retains 80% (at 1C) and 100% (at 20C) of its initial capacity after 1,000 cycles. The phase transitions during delitiation/litiation are discussed at different cutoff voltages, corresponding to the number of moles of lithium involved in the redox reactions. The reversibility of electrochemical extraction/insertion processes are confirmed using operando XRD measurements. Observed storage performances can be attributed not only to high crystallinity of LVP/C calcined at 800°C for 6 h; also to the unique mesoporous architecture of this carbon coated cathode material forming high packing density during the soft template synthesis. Obtained dense packed mesoporous architecture of LVP/C allows favourable (i) electrolyte wettability for lithium-incorporation from the electrolyte and (ii) long electronic wiring by the well-connected carbon coating towards the current collector.