Investigation of the effects of a hybrid Li-ion and electron conductive coating on a high-voltage LiFe x Mn 1-x PO 4 cathode material Jimin Kim, Dung The Nguyen and Youngil Lee 1 Department of Chemistry, University of Ulsan, Ulsan 44776, Republic of Korea, 2 Chemical Industry Research Institute, Core Research Institute, University of Ulsan, Ulsan 44776, Republic of Korea *E-mail: nmryil@ulsan.ac.kr The cathode material of a Li-ion battery is the key material that determines the battery energy. LiFePO 4 (LFP) has been successfully commercialized for electric vehicles (EVs) due to its high stability, environmental friendliness, and low cost. However, LFP has the limitation of low energy density, which limits its application for long-range EVs. Accordingly, LiFe x Mn 1-x PO 4 (LFMP), which combines LFP and LiMnPO 4 (LMP) for a higher operating voltage and thus a higher energy density, has attracted much attention worldwide. However, LFMP has its inherent low electronic conductivity and Li-ion diffusion coefficient. Therefore, a hybrid coating of Li-ion and electron conducting layers on the LFMP surface is expected to simultaneously provide transfer paths for both electrons and Li-ions, thus overcoming their inherent drawbacks. In this study, a hybrid coating layer containing carbon (C) and Li 1.3 Al 0.3 Ti 1.7 (PO 4 ) 3 (LATP) solid electrolyte on the LFMP (LFMP@C-LATP) was synthesized by the solid-state method. The structure and morphology of LFMP@C-LATP were characterized by X-ray diffraction and scanning electron microscopy equipped with energy dispersive X-ray spectroscopy. The electrochemical properties were characterized by using galvanostatic charge-discharge and cyclic voltammetry measurements. The coating material was found to improve the Li-ion diffusivity, prolong and stabilize the voltage plateaus, and contribute an additional capacity to the LFMP active material. As a result, the LFMP@C-LATP exhibits excellent capacity and cycling performance.
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