The Effect of Charging and Discharging Lithium Iron Phosphate-graphite Cells at Different Temperatures on Degradation.

Akos Kriston,Andreas Pfrang,Daniela Fontana,Ibtissam Adanouj,Matteo Destro,Vanesa Ruiz Ruiz

doi:10.3791/57501

Akos Kriston, Andreas Pfrang + Show 4 more

Open Access

https://doi.org/10.3791/57501

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Abstract

The effect of charging and discharging lithium iron phosphate-graphite cells at different temperatures on their degradation is evaluated systematically. The degradation of the cells is assessed by using 10 charging and discharging temperature permutations ranging from -20 °C to 30 °C. This allows an analysis of the effect of charge and discharge temperatures on aging, and their associations. A total of 100 charge/discharge cycles were carried out. Every 25 cycles a reference cycle was performed to assess the reversible and irreversible capacity degradation. A multi-factor analysis of variance was used, and the experimental results were fitted showing: i) a quadratic relationship between the rate of degradation and the temperature of charge, ii) a linear relationship with the temperature of discharge, and iii) a correlation between the temperature of charge and discharge. It was found that the temperature combination for charging at +30 °C and discharging at -5 °C led to the highest rate of degradation. On the other hand, the cycling in a temperature range from -20 °C to 15 °C (with various combinations of temperatures of charge and discharge), led to a much lower degradation. Additionally, when the temperature of charge is 15 °C, it was found that the degradation rate is nondependent on the temperature of discharge.

Highlights

Durability has become one of the pivotal topics of interest in lithium-ion batteries (LIB)[1,2,3] research, not neglecting safety behavior, performance, and cost
The results obtained from their electrochemical characterization are divided into three sections: i) cycling at the same charging and discharging temperatures, ii) cycling at different discharging temperatures and iii) cycling at different charging temperatures
After each block of 25 cycles, there is a drastic decay of capacity and a recuperation during the reference cycling

Summary

Introduction

Durability has become one of the pivotal topics of interest in lithium-ion batteries (LIB)[1,2,3] research, not neglecting safety behavior, performance, and cost. Future standards and regulations might benefit from the results presented in this work on the testing of charge and discharge at different temperatures[22]. The effect of different temperatures of charge and discharge on the degradation behavior of lithium iron phosphate (LFP)/graphite cells designed for sub-ambient temperatures is described. The number of possible temperature combinations was minimized using a design of experiment (DOE) method[36]; an approach used commonly in industrial optimization processes This method was applied by Forman et al.[37] to study battery degradation, providing the minimum prediction error (D-Optimum). The method helps to understand the effect of temperatures of charge and discharge and their possible interactions This information can be relevant to support the establishment of future fit for purpose and realistic protocols and standards.

Pouch Cell Preparation and Formation

Cell Fixture Prior to Electrochemical Testing

Electrochemical Cycling

Post-mortem Analysis

Representative Results

Discussion