Exploring Trimethyl-Phosphate-Based Electrolytes without a Carbonyl Group for Li-Rich Layered Oxide Positive Electrodes in Lithium-Ion Batteries

Abstract

Li-rich layered oxides (LLOs) are one of the most attractive next-generation positive electrode materials as a result of their high energy density and low cost. However, the deterioration of cycling stability observed in LLOs remains one of the fundamental obstacles to commercialization. Carbonate-based electrolytes reacting with oxygen radicals evolved from the lattice of LLOs is the chief cause of their poor cyclability. Herein, we construct no carbonyl group, trimethyl phosphate (TMP)-based electrolytes with a fluorinated ether co-solvent and apply them to investigate the electrochemical behaviors of LLO batteries. These electrolytes can capture active oxygen species; the initial reversible capacity of cells reaches 295.5 mAh g–1; and the capacity retention remains 96.7% after 100 cycles. In contrast, the capacity retention of cells using carbonate-based electrolytes is only 54.7% after 60 cycles. These results would provide the scientific basis and theoretical support for building electrolytes of LLOs with high properties in the future.

Opportunities and Challenges of Layered Lithium-Rich Manganese-Based Cathode Materials for High Energy Density Lithium-Ion Batteries

“…(d) Exploring trimethyl-phosphate-based electrolytes without a carbonyl group for Li-rich layered oxide positive electrodes in lithium-ion batteries. Reproduced with permission from ref . Copyright 2022 American Chemical Society.…”

“…Borate additives can inhibit its production by forming B–F bonds because the stability of the B–F bond is stronger. To study the stabilizing effect of electrolyte additives on the interface of lithium-rich cathode materials, it is very important to design a cathode electrolyte that can not only improve the cycle performance of the material but also stabilize the interface (Figure f); the use of polymeric borate-ester electrolyte additives meets the above requirements . To improve the electrochemical performance of lithium-rich materials, especially the cycling performance, electrolyte additives play an important role.…”

Tuning Local Structural Configurations to Improve Oxygen-Redox Reversibility of Li-Rich Layered Oxides

“…At the start of AR (approximately 4.45 V), the side reaction between oxidized oxygen and electrolyte along with the decomposition of electrolyte at high voltages contribute to the generation of CO 2 . Once O 2 releases, CO 2 shows a sharp peak simultaneously confirming that of the O 2 has a triggering effect on side reactions with electrolytes . It is well accepted that the generated O 2 comes from oxidized oxygen during AR, and the amount of O 2 can reflect the reversibility of AR.…”

“…51 Once O 2 releases, CO 2 shows a sharp peak simultaneously confirming that of the O 2 has a triggering effect on side reactions with electrolytes. 52 It is well accepted that the generated O 2 comes from oxidized oxygen during AR, and the amount of O 2 can reflect the reversibility of AR. From the DEMS data, the most gas was released from CM46-X samples (Figure S14), while the least O 2 was released from the LLO-1.30, indicating a high reversibility for AR.…”