Enhanced Long-Term Cycling Life of Ni-Rich NMC Cathodes in High-Voltage Lithium-Metal Batteries

Li metal batteries (LMBs) have revived people's interest due to their high energy density. This work compares the cycling stability, structure stability, and thermal stability of Li||0.7Nb-NMC 9055 (0.7% Nb-modified LiNi_0.9Co_0.05Mn_0.05O₂) system in commercial carbonate electrolyte (1.0 M LiPF₆ in EC/DMC) and designed carbonate electrolyte (1.0 M LiPF₆-0.125 M LiNO₃-0.025 M Mg(TFSI)₂ in FEC-EMC). Li||0.7Nb-NMC 9055 battery with designed carbonate electrolyte exhibited superior capacity retention, 80% after ∼500 cycles. This can be explained by the improved mechanical integrity of the secondary particles and large reduced charge transfer resistance. Further, the real-time thermal monitoring of full cell via a high-precision, multimode calorimeter TAM IV Micro XL shows that the designed carbonate electrolyte with multisalt additive and FEC cosolvent has less heat release during the charging and discharge process, allowing these high-nickel (Ni) cathodes to reach closer to their full potential.