Realizing Complete Solid-Solution Reaction to Achieve Temperature Independent LiFePO4 for High Rate and Low Temperature Li-Ion Batteries

The lithium iron phosphate battery (LiFePO4 or LFP) does not satisfactorily deliver the necessary high rates andlowtemperaturesdue toits lowLi(+) diffusivity, which greatly limits its applications. The solid-solution reaction, compared with the traditional two-phase transition, needs less energy, and the lithium ion diffusivity is also higher, which makes breaking the barrier of LFP possible. However, the solid-solution reaction in LFP can only occur at high rates due to the lattice stress caused by the bulk elastic modulus. Herein, pomegranate-like LFP@C nanoclusters with ultrafine LFP@C subunits (8 nm) (PNCsLFP) were synthesized. Using in situ X-ray diffraction, we confirmed that PNCsLFP can achieve complete solid-solution reaction at the relatively low rate of 0.1C which breaks the limitation of low lithiumion diffusivity of the traditional LFP and frees the lithium ion diffusivity from temperature constraints, leading to almost the same lithium ion diffusivities at room temperature, 0, -20, and -40 degrees C. The complete solid-solution reaction at all rates breaks the shackles of limited lithium ion diffusivity on LFP and offers a promising solution for next-generation lithium ion batteries with high rate and low temperature applications.