Excellent ultrahigh voltage performance of a layered cathode supported by a sacrificial layer arising from deep selenium modification

The implementation of multifunctional application scenarios for mobile terminal devices has increased the energy density requirements of batteries. Increasing the charging voltage can rapidly increase the specific capacity of layered transition metal oxides; however, it also exacerbates the release of lattice oxygen and the contraction of the unit cell. Ternary materials are designed in a secondary particle state to meet the requirements of power battery applications. Therefore, to create ternary materials that can operate under ultrahigh voltages, attention should be given to both surface modification and particle integrity maintenance. By utilizing elemental selenium (Se) with a low melting point, easy sublimation, and multiple variable valence states, deep grain boundary modification was implemented inside the particles. The performance of the cathode material was evaluated through pouch cells, and the improvement mechanism was explored through molecular dynamics simulation calculations. Under the protection of a three-dimensional Se-rich modified layer, LiNi1/3Co1/3Mn1/3O2 achieved stable operation at ultrahigh voltages (4.6 V vs. Li/Li+); a sacrificial protection mechanism based on the chronic decomposition of the Se-rich layer was proposed to explain the efficacy of Se modification in stabilizing ternary materials. This deep grain boundary modification based on elemental Se provides a new solution for the ultrahigh-voltage operation of transition metal oxides and provides a scientific basis and technical support for solving the interface contact problem of all-solid-state batteries.