Journal of Electroanalytical Chemistry, p. 115488, 2021. DOI: 10.1016/j.jelechem.2021.115488

A Mathematical Method for Open-Circuit Potential Curve Acquisition for Lithium-Ion Batteries

Jufnu Li1,2,3, Ming Zhao2,4, Changsong Dai3, Zhenbo Wang3,4, and Michael Pecht5

1 School of Automotive Engineering, Harbin Institute of Technology, Weihai 264209, Shandong, China
2 Guangdong Guanghua Sci-Tech Co. Ltd., Shantou 515000, Guangdong, China
3 School of Chemical Engineering and Chemistry, Harbin Institute of Technology, Harbin 150001, Heilongjiang, China
4 Zhuhai Zhongli New Energy Sci-Tech Co.Ltd., Zhuhai 519000, Guangdong, China
5 Center for Advanced Life Cycle Engineering (CALCE), University of Maryland, College Park, MD, USA

Abstract:

A half-cell test is often used to obtain electrode potentials for lithium-ion batteries when using an electrochemical model to simulate terminal voltage, which needs a series of time-consuming processes. However, this method generally requires expensive electrochemical measuring equipment, reference electrodes, and a vacuum glove box. This study develops a mathematical method for open-circuit potential curve acquisition. With a known open-circuit potential of the positive electrode and full-cell open-circuit voltage approximately measured at a low discharge rate of 0.02C, an open-circuit potential curve of the negative electrode can be calculated. A mathematical expression incorporating hyperbolic tangent functions and exponential functions with central coordinate positions against different lithiation states is then selected to describe the negative open-circuit potential. Finally, a least squares fitting method is adopted to identify the unknown coefficients in the expression. Five types of batteries are then tested to assess the accuracy and robustness of the method.

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