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Nano/micro-hierarchical-structured LiMn0.85Fe0.15PO4 cathode material for advanced lithium ion battery Zhihong Lei, Jiulin Wang, Jun Yang, Yanna Nuli, and Zifeng Ma ACS Appl. Mater. Interfaces, Just Accepted Manuscript • Publication Date (Web): 24 Apr 2017 Downloaded from http://pubs.acs.org on April 25, 2017
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ACS Applied Materials & Interfaces
Nano/micro-hierarchical-structured LiMn0.85Fe0.15PO4 cathode material for advanced lithium ion battery Zhihong Lei, Jiulin Wang*, Jun Yang, Yanna Nuli, Zifeng Ma Shanghai Electrochemical Energy Devices Research Center, Department of Chemical Engineering, Shanghai Jiao Tong University, Shanghai 200240, P. R. China.
ABSTRACT: Nano/micro-hierarchical-structured LiMn0.85Fe0.15PO4/C cathode materials were prepared by solvothermal synthesis combined with spray pyrolysis. XRD patterns and HRTEM images indicate that the LiMn0.85Fe0.15PO4/C are well crystallized and no impurity is observed. The as-prepared LiMn0.85Fe0.15PO4/C porous spherical (0.5-11 µm) are accumulated by primary nanoparticles (~50 nm in width, 50-250 µm in length). Adopting the sucrose as a carbon source, the cathode delivers a reversible discharge capacity of 171.2 mAh g-1 at 0.1C, almost exactly its theoretical capacity (~170 mAh g-1). Moreover, the composite exhibits high cycle stability without apparent capacity fading after 100 cycles at rates of 0.1C and 1C. The outstanding electrochemical performances are partially due to Fe2+ substituting and carbon coating which improve the electrical conductivity, and importantly due to its nano/micro-hierarchical structure, where primary nanoparticles exhibit high electrochemical activity, abundant mesopores benefit electrolyte penetration and hierarchical structure ensure the cycling stability.
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KEYWORDS: LiMn0.85Fe0.15PO4; Cathode material; Solvothermal synthesis; Spray pyrolysis; Nano/micro hierarchical structure
INTRODUCTION Considering the growing demand on energy and environmental protection, energy storage and conversion has been a very hot and important topic in modern society. Various strategies have been proposed for highly efficient energy storage and conversion. Nowadays, lithium ion batteries (LIB) are among one of the most important technologies in energy storage and conversion. Over the past decades, lithium transition metal phosphate, for example LiFePO4, has been intensively investigated and successfully commercialized for its low cost, environmental benignancy, and preferable safety. 1-3 The disadvantage of poor electronic conductivity (1.8×10-8 S cm-1) of LiFePO4 4 has been minimized by employing various strategies, e.g. reducing particles to nano-scale, coating carbon layer and doping other metal ions.1,5-11 Isostructural lithium manganese phosphate (LiMnPO4) has a similar specific capacity, but a higher charge/discharge potential of ca. 4.1 V (LiFePO4: 3.5 V) versus Li/Li+, and thereby could provide more than 20% energy density than LiFePO4. However, compared to LiFePO4, LiMnPO4 has even lower electronic conductivity (
