Key Figure Based Incoming Inspection of Lithium-Ion Battery Cells

Kerstin Ryll,Louisa Hoffmann,Oliver Landrath,Michael Kurrat,Frank Lienesch

doi:10.3390/batteries7010009

Kerstin Ryll, Louisa Hoffmann + Show 3 more

Open Access

https://doi.org/10.3390/batteries7010009

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Abstract

The cell characterization in the incoming inspection is an important but time and cost intensive process step. In order to obtain reliable parameters to evaluate and classify the cells, it is essential to design the test procedures in such a way that the parameters derived from the data allow the required statements about the cells. Before the focus is placed on the evaluation of cell properties, it is therefore necessary to design the test procedures appropriately. In the scope of the investigations two differently designed incoming inspection routines were carried out on 230 commercial lithium-ion battery cells (LIBs) with the aim of deriving recommendations for optimal test procedures. The derived parameters of the test strategies were compared and statistically evaluated. Subsequently, key figures for the classification were identified. As a conclusion, the capacity was confirmed as an already known important parameter and the average cell voltage was identified as a possibility to replace the usually used internal resistance. With regard to capacity, the integration of CV steps in the discharging processes enables the determination independently from the C-rate. For the average voltage cycles with high C-rates are particularly meaningful because of the significant higher scattering due to the overvoltage parts.

Highlights

Published: 26 January 2021Next to usages of lithium-ion batteries (LIBs) in smartphones, tablets and laptops, the increasing electrification of powertrains in passenger cars and commercial vehicles induces a growing demand of this battery cell technology [1]
The determined internal resistances were not significant at different current rates from 50% state of charge up to 90%
Based on the performance assessment from the long quality test (LQT), it should be noted that for state of charge (SoC) below 50%, the internal resistance shows a strong dependence on the SoC

Summary

Introduction

Published: 26 January 2021Next to usages of lithium-ion batteries (LIBs) in smartphones, tablets and laptops, the increasing electrification of powertrains in passenger cars and commercial vehicles induces a growing demand of this battery cell technology [1]. In terms of other battery cell technologies in the market [2,3], LIBs stand out due to high specific energy density and good cycle stability, in addition to acceptable costs for mass production [1,4,5,6,7,8]. Efficient mass production of large-format and high-quality LIBs forms the basis for successful electrical mobility [9]. Classification of these cells is necessary during the entire battery use phase, from production to second use. Qualitatively different cells influence the performance and aging behavior of an entire module [10]. In a parallel connection, balancing currents occur from good to bad cells, which accelerate the aging of the cells

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Discussion

Conclusion