Probing Hybrid LiFePO4/FePO4 Phases in a Single Olive LiFePO4 Particle and Their Recovering from Degraded Electric Vehicle Batteries

Wenyu Wang; Rui Wang; Renming Zhan; Junmou Du; Zihe Chen; Ruikang Feng; Yuchen Tan; Yang Hu; Yangtao Ou; Yifei Yuan; Cheng Li; Yinguo Xiao; Yongming Sun

doi:10.1021/acs.nanolett.3c01991

Probing Hybrid LiFePO₄/FePO₄ Phases in a Single Olive LiFePO₄ Particle and Their Recovering from Degraded Electric Vehicle Batteries

Nano Lett. 2023 Aug 23;23(16):7485-7492. doi: 10.1021/acs.nanolett.3c01991. Epub 2023 Jul 21.

Authors

Wenyu Wang¹, Rui Wang², Renming Zhan¹, Junmou Du^{1

3}, Zihe Chen¹, Ruikang Feng¹, Yuchen Tan¹, Yang Hu¹, Yangtao Ou¹, Yifei Yuan⁴, Cheng Li⁵, Yinguo Xiao², Yongming Sun¹

Affiliations

¹ Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, Wuhan 430074, China.
² School of Advanced Materials, Peking University, Shenzhen Graduate School, Shenzhen 518055, China.
³ Deepal Automobile Technology Co., Ltd., Chongqing 401120, China.
⁴ College of Chemistry and Materials Engineering, Wenzhou University, Wenzhou 325035, China.
⁵ Neutron Scattering Division, Oak Ridge National Laboratory (ORNL), 1 Bethel Valley Road, Oak Ridge, Tennessee 37831-6473, United States.

PMID: 37477256
DOI: 10.1021/acs.nanolett.3c01991

Abstract

The recycling of LiFePO₄ from degraded lithium-ion batteries (LIBs) from electric vehicles (EVs) has gained significant attention due to resource, environment, and cost considerations. Through neutron diffraction, X-ray photoelectron spectroscopy, and transmission electron microscopy, we revealed continuous lithium loss during battery cycling, resulting in a Li-deficient state (Li_1-xFePO₄) and phase separation within individual particles, where olive-shaped FePO₄ nanodomains (5-10 nm) were embedded in the LiFePO₄ matrix. The preservation of the olive-shaped skeleton during Li loss and phase change enabled materials recovery. By chemical compensation for the lithium loss, we successfully restored the hybrid LiFePO₄/FePO₄ structure to pure LiFePO₄, eliminating nanograin boundaries. The regenerated LiFePO₄ (R-LiFePO₄) exhibited a high crystallinity similar to the fresh counterpart. This study highlights the importance of topotactic chemical reactions in structural repair and offers insights into the potential of targeted Li compensation for energy-efficient recycling of battery electrode materials with polyanion-type skeletons.

Keywords: degraded lithium-ion batteries; hybrid LiFePO4/FePO4; regeneration; single particle; targeted Li compensation.