Realizing Complete Solid-Solution Reaction to Achieve Temperature Independent LiFePO ₄ 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 and low temperatures due to its low Li+diffusivity,which greatly limits its applications.The solid-solution reac-tion,compared with the traditional two-phase transi-tion,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 lithium ion diffusivity of the traditional LFP and frees the lithium ion diffusivity from tempera-ture constraints,leading to almost the same lithium ion diffusivities at room temperature,0,-20,and-40 ℃.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.