One of the main challenges for application of negative electrodes with high Si-content for high-energy lithium ion batteries is the huge volume expansion of Si upon lithiation and consecutive high irreversible capacities due to continuous formation of the solid/electrolyte interphase (SEI). To diminish the loss of active lithium and to enable anodes with high Si-contents (≥10 wt.%), pre-lithiation is considered to be an effective approach.
In this talk, electrochemical pre-lithiation by electrolysis of cost-efficient LiCl, here defined as ‘electrolytic pre-lithiation’, is investigated using Si thin films as model electrode.
The concept of pre-lithiation is presented and the consequences of pre-lithiation on the specific energy with respect to different Si/C electrodes are discussed using basic model calculations. Application of the sacrificial salt LiCl is enabled by development of novel electrolyte formulations based on γ-butyrolactone (GBL). Electrochemical properties and interphase formation are analysed by electrochemical methods in cell setups with a sacrificial lithium electrode. Optimisation of the pristine electrolyte with additives leads to reversible de/lithiation, a decrease of solvent decomposition, and a CEff in the range of standard carbonate-based electrolytes. The interphase formation on Si model electrodes is fundamentally investigated by X-ray photoelectron spectroscopy. Furthermore, the practical electrolysis setup is validated by systematic pre-lithiation experiments and failure mechanisms lowering efficiency of pre-lithiation are investigated by analytical methods. Eventually, applicability of the concept is shown by performance evaluation in LIB full cells.
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