Abstract: By employing a solution combustion method and a doping strategy involving inactive cations with different valence states (K+, Mg2+, and Al3+), three spinel-type high-entropy oxide (HEO) anode materials, namely (KCrFeMnNiZn)3/6O4, (KMgCrFeMnNiZn)3/7O4, and (KMgAlCrFeMnNiZn)3/8O4, were successfully synthesized using a cobalt-free spinel (Cr0.2Fe0.2Mn0.2Ni0.2Zn0.2)3O4 HEO as a model material.Testing results demonstrate that although the optimized (KMgAlCrFeMnNiZn)3/8O4 anode material exhibits a 17.3% reduction in theoretical specific capacity compared to the undoped counterpart, it effectively suppresses the initial capacity fading during early cycles and improves the reversible specific capacity after long-term cycling. At 200 mA·g-1, the reversible specific capacity gradually increases, reaching a 15% enhancement at the 50th cycle relative to the initial value, and a 51.3% improvement compared to the undoped sample. Meanwhile, its long-term cycling stability is significantly enhanced, with the specific capacity increasing to 1300 mAh·g-1 after 300 cycles, representing a 19.5% improvement over the undoped material. In addition, the capacity retention of this electrode at 3000 mA·g-1(relative to that at 100 mA·g-1) is 33.2%.The enhanced cycling stability is attributed to the “spectator effect” induced by the multicomponent inactive cation doping, lattice contraction, and reduced oxygen vacancy concentration; while the enhanced rate performance benefits from the increased specific surface area, optimization of the most probable pore size, and an appropriate oxygen vacancy concentration, which synergistically improve the pseudocapacitive contribution and electron Li+ transport kinetics.

Key words: Spinel-type high-entropy oxide, Anode materials; K/Mg/Al doping, Oxygen vacancies, Structural stability, Lithium storage performance