Cycle ageing analysis of a LiFePO4/graphite cell with dynamic model validations: Towards realistic lifetime predictions

Abstract

h i g h l i g h t sMethodology for cycle ageing semi-empirical model dynamic validation. Ageing tests acceleration evaluation. Detailed analysis of the influence of DOD, C-rate and Ah-throughput on cell ageing. Keywords: Li-ion battery ageing LiFePO 4 (LFP)/graphite Cycle-life performance model Dynamic storage profiles Lithium inventory loss (LLI) Loss of active material (LAM) a b s t r a c tThe present investigation work compares cycling ageing behaviour upon constant operation conditions (static tests) with degradation under non-constant schemes (dynamic tests), through a novel methodology for ageing model dynamic validation. A LFP-based Li-ion cell performance loss is analysed using a DOD and C-rate stress factors Ah-throughput-domain characterisation method, and represented using a semi-empirical model. The proposed stepwise validation approach enables assessing the static ageing tests acceleration factor and systematically improving the ageing model. The result is a simple but comprehensive model. The predictions root-mean-square error, under dynamic cycling operation conditions, is just 1.75%.

On the complex ageing characteristics of high-power LiFePO4/graphite battery cells cycled with high charge and discharge currents

“…[8] but the difference in ageing rate between symmetric/non-symmetric cycles or load patterns with rest periods was not studied. Furthermore, both capacity fade and impedance rise of LiFePO 4 /graphite battery cells during accelerated calendar and cycle ageing were studied in Ref.…”

Deterioration of lithium iron phosphate/graphite power batteries under high-rate discharge cycling

“…Although LiFePO 4 has a very stable structure, it has been indicated that the LiFePO 4 /graphite batteries still suffer from life and power decay during long time cycling [8][9][10][11]. Therefore, aging of this type of battery remains one of the biggest concerns of automakers and end customers.…”

Duty-cycle characterisation of large-format automotive lithium ion pouch cells for high performance vehicle applications

“…• The discharge energy capacity test, commonly used in cycle aging studies [25,26], determines the amount of electrical energy that can be stored in the cell under defined environmental and loading conditions. A cell is charged using a constant current-constant voltage (CC-CV) procedure at 26.5 A (0.5C) until a cell reaches a maximum potential of 4.2 V, then kept at 4.2 V, until the charging current drops to 2 A (< 0.04C).…”