Boosting capacity and operating voltage of LiVO₃ as cathode for lithium-ion batteries by activating oxygen reaction in the lattice

Capacity and operating voltage are critical parameters of cathode materials that dictate the energy density of lithium-ion batteries. Traditionally, redox reaction of the transition metal in the cathode limits the operating voltage and capacity during charge/discharge. Here, we simultaneously increase the capacity and operating voltage of LiVO₃ by utilizing the anionic redox reaction of oxygen in the lattice. While LiVO₃ gives a capacity of 235 mAh g⁻¹ with an average potential of 2.18 V vs. Li/Li⁺ between 1.5 and 3.0 V from the vanadium redox reaction, they increase to 358 mAh g⁻¹ and 2.55 V vs. Li/Li⁺, respectively, between 1.5 and 4.8 V. The higher capacity and operating voltage are due to the extraction of 0.56 mol of Li from its lattice when charging it to 4.8 V, despite vanadium originally in its highest oxidation state of 5+. The additional charge transfer derives from oxygen in the material, as X-ray spectroscopies and density functional theory calculation demonstrate the presence of peroxide species in the material and spin density around oxygen atoms, respectively, upon lithium extraction. Structural and gas analyses further reveal the stability of the anionic reaction, with only 0.21% volume change during lithium extraction with no O₂ gas release.