Regeneration of Lithium-Ion Cells
Typ
Examensarbete för masterexamen
Master's Thesis
Master's Thesis
Program
Sustainable energy systems (MPSES), MSc
Publicerad
2023
Författare
Rasmussen, Marcus
Dufvenius Esping, Elin
Modellbyggare
Tidskriftstitel
ISSN
Volymtitel
Utgivare
Sammanfattning
Electric Vehicles (EVs) are a key factor in the vision of reaching the goal of net-zero
emission by 2050, and Lithium-Ion Batteries (LIBs) are one of the most promising
technologies for EVs in this pursuit. However, as the demand for LIBs increase, the
waste generated by the spent batteries also increases. From a material supply shortage
perspective, as well as a waste management perspective, further improvements
are needed to achieve a more sustainable approach. While recycling is an important
aspect, regeneration could provide a more efficient solution by extending the LIB
lifecycle. In this work, a study to investigate the potential for capacity regeneration
of lithium-ion cells was initiated. The aim was to develop and validate a general
non-invasive regenerative approach which in the long run could be implemented into
the Volvo battery management system.
Lithium-ion cells were aged with two different charging rates during a two-month
period, after ageing, three different regenerative approaches were investigated. The
cells consisted of an NMC cathode. Performance tests and Electrochemical Impedance
Spectroscopy (EIS) were performed before ageing, after ageing and after regeneration
to quantify the effects of ageing as well as regeneration. Differential Analysis and
EIS were used to identify the different modes of degradation occurring in the cells,
meaning Loss of Active Material (LAM) and Loss of Lithium Inventory (LLI). The
cells were cycled for 365 cycles and displayed a maximum capacity fade of 3.18 %,
reaching around 97 % State of Health (SoH). Furthermore, LAM, LLI and internal
resistance increase were identified as plausible causes for capacity fade.
Three different regeneration approaches were investigated based on crystal spatial
movement, current pulses and a combination if spatial and current pulses. Electrochemical
characterization suggested additional capacity fade after the end of regeneration
for all approaches. However, an indication towards regained active anode
material was observed for all regenerated cells. The combination of crystal spatial
movement and current pulses showed indications of regained lithium inventory. Further
investigations and results validation are required to confirm those results.
Beskrivning
Ämne/nyckelord
lithium-ion batteries , battery degradation , loss of active material , loss of lithium inventory , capacity regeneration