Regulation of surface structure to suppress voltage decay for high-stable Li-rich oxide cathodes

Abstract

Layered lithium-rich manganese oxides (LMO) are promising cathode materials for high-energy density lithium-ion batteries due to their high specific capacity and working potential. However, serious voltage decay and undesirable cycle stability are big obstacles that hinder their industrialization and application. Herein, an innovative and industrially valuable strategy of constructing composite coatings and oxygen vacancies on the LMO surface is put forward to suppress voltage decay and enhance the cycling stability of LMO by precisely modulating NaBH4 treatment. The synergistic effect of surface spinel coating, NaBO2coating, and oxygen vacancies effectively inhibits the release of oxygen, impedes the occurrence of side reactions at the interface, inhibits the migration and dissolution of transition metals, suppresses the irreversible structure transformation and improves the reversibility of redox reaction. The capacity retention of the NaBH4-treated LMO material maintains 100 % after 200 cycles at 0.5C, as well as stable cycling at 2C with a discharge capacity of 180 mAh g−1 harvested. Moreover, the voltage decay is significantly suppressed by NaBH4 modification, especially the NaBH4-0.5 % sample exhibits a mere voltage decay of 1.73 mV per cycle in the 200 cycles. This study provides significant insights into the development of LMO cathodes with long-cycle performance.