Li2Se as cathode additive to prolong the next generation high energy lithium-ion batteries

The initial lithium loss caused by the formation of solid electrolyte interface (SEI) is a critical issue that reduces the energy density of lithium-ion batteries (LIBs). In order to offset the initial capacity loss, herein we propose lithium selenide (Li2Se) as an effective cathode prelithiation agent, which has a high “donor” Li-ion capacity, poor reversibility, relatively low delithiation potential and good compatibility to the existing cell fabrication processes. In a LiNi0.8Co0.1Mn0.1O2 (NCM)/ Si-C-Gr full cell, a high initial charge capacity of 250 mAh/g is obtained with 7% Li2Se additive, and the discharge capacity is 188.2 mAh/g (10.3 mAh/g higher than that of the pristine counterpart). The released capacity from Li2Se can offset the initial capacity loss during the SEI formation, confirmed by the enhanced discharged capacity. In addition, it can serve as a “lithium bank” to compensate the Li loss caused by the ongoing SEI breakage and reformation of Si-C-Gr anodes, leading to an improved cycling stability. The reversible capacity of the full cell with Li2Se prelithiation additives remains 152 mAh/g after 150 cycles at 0.3C, with an increase of 37.1% as compared to the counterpart without the additive. Li2Se is a promising cathode prelithiation agent especially for future advanced battery systems involving high specific capacity anodes with large initial irreversible capacity and poor cycling performance.