Synthesis and modification of F-doped olivine LiFe0.5Mn0.5PO4 cathode materials for Li-ion batteries
At present,LiFePO4 materials is difficult to meet the demand of high energy density.LiMnxFe1-xPO4(LMFP)cathode materials exhibit higher energy density compared with LiFePO4,while maintain the advantage of low cost and high stability of olivine structure.However,the inferior rate and cycle performance limit its practical application,which is ascribed by poor Li-ion diffusion kinetic and Jahn-Teller effect of Mn3+.In this work,a F-doping strategy was proposed to construct 110nm nanoparticles of LMFP with highly ordered b-axis orientation.The basic physicochemical properties and electrochemical properties of materials were explored,finding that the exposed(010)crystal face acted as Li-ion diffusion channel can significantly improve the Li-ion transport efficiency,while the doped F ions can increase the Li—O bond distance and the PO43-binding energy to enhance the stability of crystal structure.Therefore,the reversible specific discharge capacity of the F-doped LMFP was 153mA·h/g and 106mA·h/g at 0.1C and 5C,respectively.After 750 cycles at 1C,the capacity retention increased from 90.6%to 96.4%compared with the unmodified material.
electrochemistrylithium iron manganese phosphate(LiMn0.5Fe0.5PO4)cathodelithium-ion batteryF-doping
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