Microwave-assisted polyol synthesis of LiMnPO4/C and its use as a cathode material in lithium-ion batteries--颗粒学报PARTICUOLOGY

Long, Y., Zhang, Z., Wu, Z., Su, J., Lv, X., & Wen, Y. (2017). Microwave-assisted polyol synthesis of LiMnPO4/C and its use as a cathode material in lithium-ion batteries. Particuology, 33, 42-49. https://doi.org/10.1016/j.partic.2016.10.006

Microwave-assisted polyol synthesis of LiMnPO₄/C and its use as a cathode material in lithium-ion batteries

Yunfei Long ^{a b}, Zhihua Zhang ^a, Zhi Wu ^a, Jing Su ^{a b}, Xiaoyan Lv ^c, Yanxuan Wen^{a b *}

a School of Chemistry and Chemical Engineering, Guangxi University, Nanning 530004, China
b Guangxi Colleges and Universities Key Laboratory of Novel Energy Materials and Related Technology, Nanning 530004, China
c The New Rural Development Research Institute, Guangxi University, Nanning 530004, China

10.1016/j.partic.2016.10.006

Volume 33, August 2017, Pages 42-49

Received 29 February 2016, Revised 29 September 2016, Accepted 10 October 2016, Available online 28 March 2017, Version of Record 13 June 2017.

E-mail: wenyanxuan@vip.163.com

Highlights

• LiMnPO₄/C composites were synthesized by microwave assisted polyol method in a short time.

• Micromorphology and particle size of the prepared samples were adjusted by using surfactants.

• LiMnPO₄/C particles prepared with PVPk30 had a flaky form coated with a uniform carbon layer.

• Flaky LiMnPO₄/C composites exhibited a good rate performance and cycle stability.

Abstract

We synthesized LiMnPO₄/C with an ordered olivine structure by using a microwave-assisted polyol process in 2:15 (v/v) water–diethylene glycol mixed solvents at 130 °C for 30 min. We also studied how three surfactants—hexadecyltrimethylammonium bromide, polyvinylpyrrolidone k30 (PVPk30), and polyvinylpyrrolidone k90 (PVPk90)—affected the structure, morphology, and performance of the prepared samples, characterizing them by using X-ray diffraction, scanning electron microscopy, transmission electron microscopy, charge/discharge tests, and electrochemical impedance spectroscopy. All the samples prepared with or without surfactant had orthorhombic structures with the Pnmb space group. Surfactant molecules may have acted as crystal-face inhibitors to adjust the oriented growth, morphology, and particle size of LiMnPO₄. The microwave effects could accelerate the reaction and nucleation rates of LiMnPO₄ at a lower reaction temperature. The LiMnPO₄/C sample prepared with PVPk30 exhibited a flaky structure coated with a carbon layer (∼2 nm thick), and it delivered a discharge capacity of 126 mAh/g with a capacity retention ratio of ∼99.9% after 50 cycles at 1 C. Even at 5 C, this sample still had a high discharge capacity of 110 mAh/g, demonstrating good rate performance and cycle performance. The improved performance of LiMnPO₄ likely came from its nanoflake structure and the thin carbon layer coating its LiMnPO₄ particles. Compared with the conventional polyol method, the microwave-assisted polyol method had a much lower reaction time.

Graphical abstract

Keywords

Lithium-ion batteries; Cathode materials; Lithium manganese phosphates; Microwave-assisted polyol method

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