Geometric method for evaluating capacity recession of lithium ion battery

Abstract

The invention relates to a geometric method for evaluating capacity recession of a lithium ion battery. The geometric method for evaluating capacity recession of the lithium ion battery comprises the steps that (1) geometrical characteristic values under different working conditions are extracted, wherein the number of the geometrical characteristic values is four, and the four geometrical characteristic values are the duration of continuous charging during constant-voltage charging, the maximum curvature radius of a current characteristic curve at the constant-voltage charging stage, the area under the condition of the constant-voltage charging current characteristic curve, and the maximum gradient of a discharge voltage characteristic curve at the early stage; (2) an intrinsic manifold based on the Laplace characteristic mapping method is established, namely the four geometrical characteristic values obtained in the first step are used as input of the Laplace characteristic mapping method to construct a low-dimensional manifold, namely the intrinsic manifold, embedded into a high-dimensional space; (3) a geodesic line on the manifold is used for geometric evaluation of the capacity of the battery. The geometric method for evaluating capacity recession of the lithium ion battery has the advantages that essential recession or the health state of the battery can be determined effectively, studying of a complicated electrochemistry mechanism is not needed, a complicated electrochemistry model does not need to be established, and the method can be realized easily.

Description

Technical field [0001] The invention relates to a method for estimating the capacity decline of a lithium ion battery, and belongs to the technical field of battery health management. Background technique [0002] Because lithium-ion batteries have the advantages of high energy density and light weight, many researchers have carried out a lot of research work on lithium-ion batteries in order to improve the performance of lithium-ion batteries. Considering that the capacity loss rate largely depends on the working conditions and permanent capacity loss over time, an accurate assessment of the battery's available capacity will manage battery energy more reliably and effectively. [0003] In the past few decades, with the development of software capabilities and modern test technology, battery modeling and simulation technology has made remarkable achievements. Some attempts have also been made to evaluate the capacity of lithium-ion batteries. Literature Zhang X, Ross PN, Jr, Kost...

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Problems solved by technology

[0007] (3) Rely on accurate SOC values, and SOC acquisition itself is a major and difficult research field;

[0008] (4) A large number of OCV values ​​are required, which in turn requires a relatively long standing time;

[0009] (5) Not applicable to different working conditions of the battery

[0010] All these problems can be summarized into three main aspects: (1) complex electrochemical mechanisms and corresponding models; (2) poor available data, that is, data is important for many algorithms, but in practical engineering, these data But it is difficult to obtain; (3) Different working conditions, that is, various factors affect the battery capacity estimation

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