Liquid ammonia chemical lithiation: an approach for high energy and high voltage Si-graphite | Li 1+ x Ni 0.5 Mn 1.5 O 4 Li-ion batteries
Chemical lithiation using lithium metal dissolved in liquid ammonia is introduced for the first time as a viable, potentially scalable method to over-lithiate cathode materials, in this case, the 5V spinel Li 1+ x Ni 0.5 Mn 1.5 O 4 . In this formula the value of x represents the amount of extra lithium inserted into the spinel. Such over-lithiated cathodes can subsequently be used to pre-lithiate high-energy anodes in a lithium-ion battery configuration during the first charge step. Lithiated 5V spinel Li 1+ x Ni 0.5 Mn 1.5 O 4 cathode materials prepared by this technique show higher first delithiation capacities, confirming the chemically inserted lithium is electrochemically active. Full cells with a Si-graphite anode and the Li 1+ x Ni 0.5 Mn 1.5 O 4 (x=0.62) cathode show a 23 % higher reversible capacity in the first cycle than LiNi 0.5 Mn 1.5 O 4 baseline cells, and improved capacity retention. The extra, chemically inserted lithium therefore sacrificially compensates for the loss of lithium at the anode allowing higher utilization of the cathode capacity in following cycles.