![]() ![]() The improvement in the bulk conductivity is not due to antisite defects (Co or Fe on the Li site) but from the mobile polarons, and associated with lithium vacancies 20, 21. Moreover, in several works, cobalt ions were substituted with different transition metals such as Ni, Mn, and Fe, and this substitution caused significant improvement in the electronic and ionic conductivity of LiCoPO 4, thus enhancing its electrochemical performance 15, 16, 17, 18, 19. To increase the electrochemical performance of LiCoPO 4, different strategies were used, such as coating of LCP with various carbon sources to increase electronic conductivity 1, 2, 10, 11, 12, 13, 14 and nanosizing to improve ionic conductivity. LiCoPO 4 belongs to the LiMPO 4 olivine family (M = Co, Mn, Fe, and Ni) and demonstrates mediocre rate performance and cycle stability because of low diffusion of lithium ions in the lattice and poor electronic conductivity 7, 8, 9. LiCoPO 4 (lithium cobalt phosphate, LCP) is of particular interest due to a high theoretical capacity of around 167 mAh g −1, and high operating voltage (OV) ~ 4.8 V vs. To improve the battery energy density, it's necessary to utilize a high voltage positive electrode material. The improvement of Li-ion batteries (LIB) is focused on enhancing the specific power and energy density. The calculation of DFT and Bader charge analysis expects the oxygen redox procedure combined with d-metals redox, which supplements iron charge variations and dominates at high voltages when x < 0.75 in Li xCoFePO 4. Rietveld's refinement of XRD data allowed us to analyze the changes in the lattice of cathode material and their reversibility upon (de)lithiation during cycling. Thus, we were able to track the phase transitions in the material upon charge and discharge and quantitatively analyze the M 2+/M 3+ electrochemical conversion rate for both Fe and Co. For both Co and Fe two components were extracted, they correspond to fully lithiated and delithiated phases of Li xMPO 4 (where M = Fe, Co). Principal components analysis (PCA) of XAS data allowed the extraction of spectra of individual phases in the material and their concentrations. Here we used a combination of operando synchrotron-based XRD and XAS to investigate the dynamics of d-metal local atomic structure and charge state upon cycling of LiCo 0.5Fe 0.5PO 4 mixed d-metal olivine cathode material. However, such modification requires a deep understanding of the structural behavior of cathode material upon lithiation/delithiation. One way to overcome this issue might be decreasing the working potential of the battery by doping LiCoPO 4 by Fe, thus reducing electrolyte degradation upon cycling. Lithium-ion batteries based on high-voltage cathode materials, such as LiCoPO 4, despite being promising in terms of specific power, still suffer from poor cycle life due to the lower stability of common non-aqueous electrolytes at higher voltages.
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