Electrochemical Preparation of Lithium-Rich Graphite Anode for LiFePO 4 Battery
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ANOSTRUCTURES AND NANOMATERIALS
Electrochemical Preparation of Lithium-Rich Graphite Anode for LiFePO4 Battery Y. Z. Songa, *, Jie Songa, Lili Zhanga, Benlin Daia, and Chuchu Weia a
School of Chemistry and Chemical Engineering, Huaiyin Normal University, Jiangsu Province Key Laboratory for Chemistry of Low-Dimentional Materials, Huai An 223300, People’s Republic of China *e-mail: [email protected] Received April 18, 2020; revised April 18, 2020; accepted July 9, 2020
Abstract—The lithium-rich graphite anode is prepared using porous lithium foil/graphite for LiFePO4 battery. The specific capacities of LiFePO4/lithium-rich graphite battery are tested by the galvanostatic current charge-discharge technology at higher current densities. The lithium-rich graphite anode can improves the capacities of LiFePO4/lithium-rich graphite battery at higher currents. During 300 cycles of charge-discharge no short circuit is observed in the lithium-rich battery at 0.5~5 mA cm–2. The electrode materials are characterized by scanning electron microscopy, X-ray diffraction powder diffraction, thermogravimetric analysis, and AC impedance, indicating that there was no obvious damage to the battery materials, and the capacity attenuation at the higher current density was caused by the increase of polarization voltage due to the lack of lithium ions in the cathode and the increase of anode resistance. Keywords: Lithium-rich graphite anode, lithium iron phosphate battery, capacity DOI: 10.1134/S0018143920060144
INTRODUCTION Lithium-ion iron phosphate (LiFePO4) battery has been widely used in mobile phones, laptops, electric drills, and electric vehicles [1, 2] due to its higher specific capacity (SC), stable and high discharge voltage, long cycle life, high safety rating, and good environmental compatibility [3–5]. The capacities of commercial LiFePO4 battery was related to the structural damage of the electrode material, the increase of internal resistance and the loss of active materials etc. in the use. When the discharging voltage was set at more than 2 V (vs. graphite) the active lithium adsorbed in graphite couldn’t be completely oxidized, the capacities would also decay. The polarization of the LiFePO4 battery caused by the resistance of the LiFePO4, non-conductive organic solvents and separator, etc., also greatly reduced the charge-discharge efficiency. The growth of the solid electrolyte interphase (SEI) film limited and lowered the capacities of lithium-ion cell [6], the lithium inventory loss in the SEI layer was generally considered as the most crucial factor responsible for the capacity decay of LiFePO4/graphite cells [7–14], and the lithium ions loss were mainly attributed to the formation of LiF, LixPFy, LixPOFy, Li2CO3 and ROCO2Li on the surface of graphite electrode [15, 16]. The studies have shown that the active lithium of 15.7% in the commercial 18650 batteries was consumed by the SEI film
[17]. Therefore, it is of great significance to provide Lirich anode for LiFePO4/graphite cell. Lithium has higher theoretical
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