Enhanced high-voltage tolerance of ether electrolyte by adding tiny nitrate High-voltage tolerance was first evaluated in the cyclic voltammetry (CV) and linear sweep voltammetry (LSV) tests on Li||LiCoO2 and Li||Al cells, respectively (Figure and Figure ). When using the LiCoO2 electrode as the working electrode, unlike the low oxidation onset voltage of ~3.9 V for pristine ether electrolytes of 1 M lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) in DME, the ether electrolyte with 50 mM NO3 -showed greatly improved oxidation stability by giving a cutoff voltage at 4.4 V (Figure ). To assess the feasibility of adding the nitrate to enable the dilute ether electrolyte under high voltages, LMBs, with a LiCoO2 cathode and 1 M LiTFSI in DME, were cycled at a high charge cutoff voltage of 4.3 V. A low cathode areal loading of 0.3 mAh cm -2 and excess Li were used to ensure only a small amount of Li metal was cycled, the impact of electrolyte stability on the Li anode is deliberately minimized. As shown in Figure , in only the 7 th cycle, the cell with the nitrate-free dilute ether electrolyte failed to reach the cutoff voltage (<4.2 V), demonstrating that the conventional dilute ether electrolyte has extremely poor high-voltage compatibility. In stark contrast, the NO3 --containing ether electrolyte (i.e., 1 M LiTFSI/DME with 50 mM LiNO3) could achieve 93% capacity retention with a limited polarization increase (Figure ) after 1000 cycles. In addition to LiCoO2 cathodes, remarkable high-voltage stability (1000 cycles with 89% capacity retention) was also found in the long-term cycling of NMC532 cathodes (Figure ). Furthermore, microscopy images proved that Al foil cycled in the NO3 --containing dilute ether electrolyte remains intact, whereas pitting corrosion occurred in the pristine ether electrolyte (Figure ). These results prove the robustness of NO3 --containing dilute ether electrolyte under high voltages. Note that because of the poor oxidation stability of the pristine ether electrolyte at high voltages (Figure and Figure ), it was not studied further in electrochemical cells.