Direct Contact Prelithiation of Silicon-Dominant Anodes Using Ultra-Thin Lithium Foils

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With the steady growth of the electric vehicle market, the development of high-energy-density lithium-ion batteries is increasingly coming into focus. Silicon has a nearly ten times higher specific capacity for lithium storage than conventionally used graphite, making silicon a promising anode material for high-performance lithium-ion battery applications[1]. However, silicon shows a high volume expansion upon lithiation, leading to a rapid capacity fade due to the loss of active lithium associated with continuous solid electrolyte interphase formation[2]. Direct contact prelithiation is a method to compensate for the loss of active lithium by incorporating additional lithium metal during battery cell production. The use of lithium foil is a facile approach but depends on the availability of ultra-thin lithium foils[3].In this study, silicon-dominant anodes with a silicon content of ca. 70 % were prelithiated by lithium foils with a thickness of 5 and 10 µm using a calendering process. A glove box integrated calender under an argon atmosphere was used to transfer the ultra-thin lithium foils from a carrier foil on the entire anode surface. This facilitates a homogenous prelithiation of the anode and equal compression force over the entire anode surface. A process study was conducted to find suitable process parameters for the full-surface lithium foil application on the anodes. The formed anode-lithium-composite was investigated with and without the presence of an electrolyte. Pouch cells with nickel-rich cathodes were built to show the performance improvement through the presented prelithiation technique in the full cell setup.An increase of 16 % in full cell capacity shows the potential of direct contact prelithiation to boost the energy density of already high-energy lithium-ion battery material systems. The incorporated lithium metal compensates for the loss of active lithium and thereby enhances the cycle life of the battery cells, making the proposed prelithiation method an enabler for the use of silicon-dominant anodes for high-performance applications.