Rational design of a synthetic strategy, carburizing approach and pore-forming pattern to unlock the cycle reversibility and rate capability of micro-agglomerated LiMn0.8Fe0.2PO4 cathode materials

摘要

Nanometer-sized LiMn0.8Fe0.2PO4 (nano-LMFP) is one of the most suitable LiMnPO4 derived cathode materials to maximize gravimetric capacity and rate capability. However, the poor cycling performance, low volumetric energy density and safety hazards of nano-LMFP limit its large-scale commercialization. To overcome these development bottlenecks, a uniform three-dimensional interconnected conductive carbon network modified LiMn0.8Fe0.2PO4 nanoporous micro-agglomerated (micro-LMFP/C) composite was synthesized via a three-step solid-state reaction (3S) combined with three-step carburizing (3C) and two-step pore-forming (2P). The novel micro-LMFP/C composite exhibits excellent gravimetric/volumetric reversible capacities, weak electrochemical polarization and high rate capability. Even if increased to 20C, a satisfactory discharge capacity of 92.5 mA h g(-1) (70.2% of the initial value at 0.1C) and an outstanding discharge plateau of 3.76 V can be observed. More importantly, for the 3S synthetic strategies, the novel 3C2P-assisted synthesis of micro-LMFP/C composites can simultaneously deliver 2.6 and 1.5 times higher volumetric capacity than that of synchronous and stepwise carburizing assisted synthesis of samples, respectively.