Positive Surface Pseudocapacitive Behavior-Induced Fast and Large Li-ion Storage in Mesoporous LiMnPO4 @C Nanofibers.

Olivine-structured LiMnPO4 (LMP) is an efficient Li+ host owing to its high theoretical energy density and thermal stability. However, its poor ionic and electronic conductivity severely hinder its practical application. Herein, one-dimensional (1D) LMP@C nanofibers with in situ created 3D mesoporous architecture are reported and the charge-storage behavior is addressed. Ultrafine LMP nanoparticles are homogeneously confined in the nanofibers with interconnected and exposed mesoporous intersections, facilitating the electronic/ionic transportation and retarding the pulverization/fracture of electrodes. Remarkably, the hierarchical construction promotes a certain degree of pseudocapacitive contribution. The diffusion-controlled battery-type and surface-controlled capacitive faradaic redox processes act synergistically, giving new insights into Li-ion storage cathode materials to reach the common goal of high energy density and power density simultaneously. The current separation technique suggests surface-dominated pseudocapacitance as the major Li+ storage mechanism at high rates, which is regarded as an efficient way to improve the rate performance. Hence, the as-prepared LMP@C nanofibers could deliver a high reversible capacity of 149.8 mAh g-1 with 92 % charge retention over 300 cycles at 0.2 C (1 C=171 mA g-1 ). Even at a high rate of 5 C, a capacity of 63.1 mAh g-1 is retained after 2000 cycles with an exceptional cyclic stability.