Pre-lithiation is a process that involves the addition of extra lithium to a cell during the initial assembly, prior to the first charge/discharge cycle. The primary goal of pre-lithiation is to mitigate the irreversible capacity loss that occurs during the initial battery cycling, known as the first-cycle capacity loss. This loss is caused by the formation of a Solid Electrolyte Interphase (SEI) on the anode surface and the partial consumption of lithium ions in the process.
✔️Methods of Pre-lithiation:
Several pre-lithiation techniques have been developed to introduce extra lithium into the battery system. These methods can be broadly classified into three categories:
a) Direct pre-lithiation of anodes: In this approach, lithium is directly deposited onto the anode surface, either electrochemically or through a vapor deposition process. This method is relatively simple but can lead to uneven lithium distribution and poor adhesion of lithium to the anode, which may affect the overall battery performance.
b) Pre-lithiation using lithium sources: This approach involves incorporating a lithium source, such as lithium metal or lithium-containing compounds, into the electrode or electrolyte. During the initial charge/discharge cycle, lithium ions are released from the lithium source and become available for electrochemical reactions.
c) Electrochemical pre-lithiation: In this method, an additional lithium-containing electrode is added to the battery assembly, forming a tri-layer structure. During the first charge, the lithium ions are extracted from this extra electrode and transported to the anode. Once pre-lithiation is complete, the additional electrode can be removed or left in place to act as a reservoir for lithium ions.
✔️Benefits of Pre-lithiation:
a) Improved energy density: By compensating for the initial capacity loss, pre-lithiation can significantly increase the battery's energy density, which is crucial for applications like EVs that require extended driving range.
b) Enhanced Coulombic efficiency: Pre-lithiation reduces the irreversible capacity loss during the first cycle, thereby improving the overall Coulombic efficiency of the battery.
c) Prolonged cycle life: By reducing the formation of SEI and preventing excessive lithium consumption, pre-lithiation can contribute to a longer cycle life for LIBs.
✔️Challenges and Future Outlook:
The methods used for pre-lithiation can be complex and may introduce additional costs and manufacturing steps. Furthermore, the extra lithium ions may increase the risk of lithium plating on the anode surface, especially at high charging rates, leading to a higher risk of internal shorts and a reduced cycle life; hence, the selection of novel and optimal pre-lithiation strategies is essential.
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