Fast-charging effects on ageing for energy-optimized automotive LiNi1/3Mn1/3Co1/3O2/graphite prismatic lithium-ion cells

Abdilbari Shifa Mussa,Anti Liivat,Fernanda Marzano,Matilda Klett,Bertrand Philippe,Carl Tengstedt,Göran Lindbergh,Kristina Edström,Rakel Wreland Lindström,Pontus Svens

doi:10.1016/j.jpowsour.2019.02.095

Abdilbari Shifa Mussa, Anti Liivat + Show 8 more

Open Access

https://doi.org/10.1016/j.jpowsour.2019.02.095

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Abstract

The reactions in energy-optimized 25 Ah prismatic NMC/graphite lithium-ion cell, as a function of fast charging (1C4C), are more complex than earlier described. There are no clear charging rate dependent trends but rather different mechanisms dominating at the different charging rates. Ageing processes are faster at 3 and 4C charging. Cycling with 3C-charging results in accelerated lithium plating but the 4C-charging results in extensive gas evolution that contribute significantly to the large cell impedance rise. Graphite exfoliation and accelerated lithium inventory loss point to the graphite electrode as the source of the gas evolution. The results are based on careful post-mortem analyses of electrodes using: scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and electrochemical impedance spectroscopy (EIS). SEM results show particle cracking independent of the charging rate used for the cycling. XPS and EIS generally indicate thicker surface film and larger impedance, respectively, towards the edge of the jellyrolls. For the intended application of a battery electric inner-city bus using this type of cell, charging rates of 3C and above are not feasible, considering battery lifetime. However, charging rates of 2C and below are too slow from the point of view of practical charging time.

Highlights

The electric vehicle (EV) market has significantly increased in volume during the last decade mainly due to the development of lithium-ion batteries with higher energy density, lower price, and longer service life
The sudden death in the 4C cells is due to the activation of the current interrupt device (CID) that irreversibly disconnected the positive tab from the jellyroll
The effects of fast charging (1–4C in 20–80% state-ofcharge range) on the ageing of a 25 Ah energy-optimized automotive prismatic lithium-ion cell based on NMC/graphite chemistry is investigated by post-mortem physical, chemical, and electrochemical characterizations, and cell voltage fitting analysis

Summary

Introduction

The electric vehicle (EV) market has significantly increased in volume during the last decade mainly due to the development of lithium-ion batteries with higher energy density, lower price, and longer service life. There are still battery-related challenges to Journal of Power Sources 422 (2019) 175–184 overcome before plug-in hybrid vehicles (PHEV) and battery electric vehicles (BEV) can become major players in the vehicle market, especially in the heavy-duty vehicle segment One such important challenge is driving time versus charging time. Balancing battery size and utilization, a recent study shows that BEV buses with smaller batteries installed and charged at the end stops of the route have the potential to be more cost efficient compared to overnight charged BEV buses when the charging infrastructure is included in the calculation [3] In this case, the fast-charging capability is more crucial for heavyduty commercial vehicles than for passenger cars. In combination with energy optimized lithium-ion batteries, fast charging presents an important challenge regarding battery lifetime

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