Lithium iron phosphate (������������4, ������) , and lithium manganese phosphate (������������4, ������) , have been extensively researched as viable alternatives to cathode material lithium cobalt oxide (����������2, ������), due to their higher specific charge capacity, low toxicity and relative chemical stability. However, they are not without their disadvantages; LFP has a lower operating voltage than LCO, leading to an overall lower energy density, while LMP’s poor conductivity results in lower realized capacity. A new class of cathode materials, ��������������1−������4, has been studied, in the hopes that a mixture of Fe and Mn will yield better electrochemical properties than pure LFP or LMP alone. Thus, it is necessary to determine the exact role that iron and manganese play in the electrochemical properties of these materials, and how these properties can be fine-tuned with the composition x. We characterize the ��������������1−������4 system via single crystal nuclear magnetic resonance (NMR) spectroscopy using 7Li and 31P as probe nuclei. Measurements of the angular dependences of chemical shifts are necessary, in order to study the anisotropy and identify the various interaction tensors that govern the lithium and phosphorus crystal environments. In principle, it is possible to separate the electric field gradient tensor (EFG) from the paramagnetic shift tensor about 7Li nuclei. An evaluation of the EFG will lead towards a greater understanding of electronic and structural environment of the lithium ions, leading to a better understanding of electrochemical properties in this system. The principal goal in this investigation is to map out the interaction tensors as well as characterize the structure and magnetic susceptibility �� of ��������������1−������4 single crystals, for x = 0, 0.25, 0.4, 0.5, 0.75, and 1.0. It is hoped that such localized structural information may shed light on the lithium diffusion anisotropy, known to occur in these materials.

Single crystal NMR study of LiFexMn1-xPO4

256th National Meeting (2018)

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