Improving LiNi_xCo_yMn_1−x−yO₂ cathode electrolyte interface under high voltage in lithium ion batteries

Abstract

The demanding for high energy density as well as high safety is still an important threshold for battery commercialization. Next‐generation layered LiNixCoyMn1−x−yO2 (NCM) cathodes will meet the specific energy required for driving range of at least 300 miles from a single charge to guarantee the success of electric vehicles. Extending operating voltage of NCM cathode materials is considered as an effective way to increase energy density of lithium ion batteries. However, unstable electrode electrolyte interface (CEI) limits the electrochemical performance of NCM cathodes when operating at high voltages (>4.3 V). In this review, underlying factors and mechanisms that result in the failure to form a robust CEI are analyzed, including surface phase reconstruction, stress‐induced cracking, transition metal dissolution, electrolyte decomposition and oxygen redox reaction. Then, progress on how to improve and stabilize CEI is summarized. To bridge the gap between current and next generation automotive batteries, it is expected that the situation of NCM electrode materials at high voltage to be fine‐tuned with available variables such as nickel content, packaging density and loading level. Moreover, more detailed work on designing and studying a reliable CEI can help the application of NCM cathodes under high voltage.

Lithium Phosphonate Functionalized Polymer Coating for High‐Energy Li[Ni0.8Co0.1Mn0.1]O2 with Superior Performance at Ambient and Elevated Temperatures

“…These findings globally indicate that the outer CEI layer is more organic in nature, while the inner layer is rather composed of inorganic products, which is in line with earlier CEI studies. [ 29 ] Moreover, they show that the surface chemistry of the pristine electrodes is somehow retained, which includes the preservation of the PP10‐Li coating layer at the intimate particle surface.…”

Strategic Approach to Diversify Design Options for Li‐Ion Batteries by Utilizing Low‐Ni Layered Cathode Materials

“…In this case, the CEI layer of NCM523 is not stable due to the continuous formation/decomposition reaction of the electrolyte on the cathode electrode surface. [ 5,27 ] Thus, it is speculated that NCM523 exhibited an activation process‐like behavior during the initial cycling until the CEI layer formation/decomposition reaction was finished and stabilized. The discharge capacity retention of the NCM523 cathode was 98.7% after 100 cycles and 78.7% after 400 cycles compared with the NCA cathode (93.7% for 100 cycles and 78.1% for 400 cycles).…”

Tris(2,4,6‐trimethylphenyl) phosphine with Aluminum Oxide Incorporated Polyethylene Separator for Lithium‐Ion Batteries

“…The cycling performances show that the cell cycled with the bare PE separator shows a continuous decrease in cycling retention, which reaches 47.1% after 150 cycles. Note that electrolyte decomposition also continuously occurs on the surface of NCM811 cathode owing to the unstable nature of the Ni 4+ species in the charging state 34,35 . Once the electrolyte is decomposed, it provides radical intermediates in the cell, and these trigger additional decomposition reactions during the electrochemical charging/discharging process 36,37 .…”