Since the transportation sector wants to move away from fossil fuels and become more dependen ton clean and green energy, the use of rechargeable batteries is a good solution. Lithium-based batteries work very well as rechargeable batteries in electric vehicles. To extend the cycle life of lithium-based batteries a reversed Li+-trapping protocol has been implemented to extract lostcapacity. Prior to the start of this project, reversed Li+-trapping has been used on a proof-of-concept level and no specific protocol has been utilised in conjunction with full cells. With a protocol that uses constant voltage discharge steps on every fifth cycle, trapped Li+ can diffuse out from the graphite (anode) and travel back to the NMC811 (cathode). This will result in a lower capacity loss than if it only had cycled with constant current, using a C-rate of 1C. If a cell is operated with a constant voltage discharge step on every cycle, high capacity can be maintained for many cycles. This could potentially be used as a formation cycle protocol. The capacity is higher in the long run if the constant voltage discharge step is applied on every fifth cycle rather than every cycle. With a constant voltage discharge cell voltage of 2.8 V good results are obtained. A constant voltage discharge cell voltage of 0 V will however destroy the cell due to Cucurrent collector dissolution.
| Identifer | oai:union.ndltd.org:UPSALLA1/oai:DiVA.org:uu-511594 |
| Date | January 2023 |
| Creators | Thulin, Christopher |
| Publisher | Uppsala universitet, Oorganisk kemi, Uppsala universitet, Strukturkemi |
| Source Sets | DiVA Archive at Upsalla University |
| Language | English |
| Detected Language | English |
| Type | Student thesis, info:eu-repo/semantics/bachelorThesis, text |
| Format | application/pdf |
| Rights | info:eu-repo/semantics/openAccess |
| Relation | UPTEC K, 1650-8297 ; 23033 |
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