Surface passivation of lithium nitride as pre-lithiation reagents to enhance its air-stability

Prelithiation is a highly attractive technique to offset the irreversible lithium loss caused by the formation of the SEI film during the first charging cycle in lithium-ion batteries. Li 3 N is an ideal prelithiation reagent due to its high theoretical specific capacity, proper decomposing potential and no residues after decomposition. However, the chemical instability of Li 3 N inevitably limits its large-scale use as prelithiation additives. Here we successfully developed a facile surface passivation method to improve the stability of Li 3 N by immersing Li 3 N in both fluoroethylene carbonate (FEC) and Vinylenecarbonate (VC) to in situ generate a coating layer on the Li 3 N surface via the spontaneous decomposition of the solvents. The coating composed of LiF, Li 2 CO 3 and lithium carbonate organics enables excellent stability of Li 3 N in the ambient environment. Remarkably, surface-passivated Li 3 N display a high prelithiation capacity of 1799 mAh/g and maintain a high capacity of 1612 mAh/g (almost 90 % of initial capacity) after exposed to humid air with 12 % relative humidity for 26 h. The effect of the compensation of lost active lithium is verified via a LiFePO 4 @ex-Li 3 N-coated//HC full cell, which exhibits not only a high capacity but also a stable cycling performance. The specific energy of LiFePO 4 @ex-Li 3 N-coated//HC full cell shows a remarkable increase compared to the LiFePO 4 //HC full cell, exhibiting ~29 % more specific energy after the 1st cycle, even Li 3 N-coated have been exposed to air with 12 % relative humidity for 26 h before use.