Comprehensive Aging Analysis of Volumetric Constrained Lithium-Ion Pouch Cells with High Concentration Silicon-Alloy Anodes

Lysander De Sutter,Yousef Firouz,Gert Berckmans,Margret Wohlfahrt-Mehrens,Mario Marinaro,Joeri Van Mierlo,Noshin Omar,Jelle Smekens

doi:10.3390/en11112948

Abstract

In this research, twenty-four high capacity (1360 mAh) NMC622/Si-alloy Li-ion full pouch cells with high silicon-alloy content (55%) are cycle aged under seven different cycling conditions to study the effect of different stressors on the cycle life of Si-anode full cells, among which are the effect of ambient temperature, Depth of Discharge (DoD) and the discharge current. The cells are volumetrically constrained at an optimal initial pressure to improve their cycle life, energy and power capabilities. Furthermore, the innovative test setup allows measuring the developed pressure as a result of repeated (de-)lithiation during battery cycling. This uniquely vast testing campaign on Si-anode full cells allows us to study and quantify independently the influence of different stress factors on their cycle life for the first time, as well as to develop a new capacity fade model based on an observed linear relationship between capacity retention and total discharge capacity throughput.

Highlights

The continuous rise of long-lived greenhouse gases in our Earth’s atmosphere, among which are CO2, CH4 and N2 O, presents the largest driving force behind climate change and has driven humankind to explore new technologies
Twenty-four high capacity (1360 mAh) NMC622/Si-alloy Li-ion full pouch cells with high silicon-alloy content (55%) are cycle aged under seven different cycling conditions, including the Worldwide harmonized Light Vehicles Test Procedure (WLTP) driving cycle, to study the effect of different stressors on the cycle life of Si-anode full cells, among which are the effect of ambient temperature, Depth of Discharge (DoD) and the discharge current
The average measured capacity retention over the battery lifetime during the Quasi-Open Circuit Voltage test (QOCV) check-up tests is presented for all cells in Figure 5, along with their respective error bars

Summary

Introduction

The continuous rise of long-lived greenhouse gases in our Earth’s atmosphere, among which are CO2 , CH4 and N2 O, presents the largest driving force behind climate change and has driven humankind to explore new technologies. Decarbonization of transportation has become a huge element of these new technologies due to the overwhelming contribution that combustion of fossil fuels presents to these harmful gases [1]. Electric Vehicles (EV), powered by rechargeable batteries rather than traditional combustion engines, show great potential in advancing this decarbonization. The commercial Li-ion batteries currently powering EV’s are reaching their theoretical capacity limits, leaving limited opportunity to increase energy density using traditional materials [2]. Silicon (Si) presents an attractive alternative to the graphite anode material currently used in conventional Li-ion batteries owing to its natural abundance, significantly higher volumetric capacity and specific capacity (2194 Ah/l vs 719 Ah/l for Li15 Si4 and LiC6 ; 3579 mAh/g vs 372 mAh/g for Si and graphite) [3,4]. Plenty of research [5,6,7,8,9,10,11,12,13,15,16,17] is available in the literature, identifying the aging mechanisms induced by electrochemical cycling of Si anode half-cells

Methods

Results

Conclusion