Upgrading Carbonate Electrolytes for Ultra-stable Practical Lithium Metal Batteries.

LiNO3 is a widely used salt-additive that markedly improves the stability of ether-based electrolytes at a Li metal anode but is generally regarded as incompatible with alkyl carbonates. Here we find that contrary to common wisdom, cyclic carbonate solvents such as ethylene carbonate can dissolve up to 0.7 M LiNO3 without any additives, largely improving the anode reversibility. We demonstrate the significance of our findings by upgrading various state-of-the-art carbonate electrolytes with LiNO3 , which provides large improvements in batteries composed of thin lithium (50 µm) anode and high voltage cathodes. Capacity retentions of 90.5 % after 600 cycles and 92.5 % after 200 cycles are reported for LiNi0.6 Mn0.2 Co0.2 O2 (2 mAh cm-2 , 0.5 C) and LiNi0.8 Mn0.1 Co0.1 O2 cathode (4 mAh cm-2 , 0.2 C), respectively. 1 Ah pouch cells (≈300 Wh kg-1 ) retain more than 87.9 % after 100 cycles at 0.5 C. This work illustrates that reforming traditional carbonate electrolytes provides a scalable, cost-effective approach towards practical LMBs.