Quasi‐2D Ruddlesden–Popper Oxides LaSrCu _0.5 Mn _0.5 O ₄ and LaSrZn _0.5 Mn _0.5 O ₄ for Charge Storage

Charge storage by oxide anion intercalation into oxide materials has been recently demonstrated. In an effort to further expand this field beyond 3D systems, we have investigated this effect in quasi‐2D oxides LaSrCu 0.5 Mn 0.5 O 4 and LaSrZn 0.5 Mn 0.5 O 4 . The structure of these materials consists of octahedral (Cu/Mn)O 6 or (Zn/Mn)O 6 units, forming 2‐dimensional layers, while La/Sr are located in the gaps between those layers. The spaces within the structure are expected to support the intercalation of the oxide anion. We first undertook half‐cell measurements in a three‐electrode setup and analyzed the contributions from capacitive and diffusive processes to the observed current in electrochemical measurements. We then assembled symmetric full cells using these materials and conducted galvanostatic charge–discharge studies, which showed greater pseudocapacitive properties for LaSrCu 0.5 Mn 0.5 O 4 compared to LaSrZn 0.5 Mn 0.5 O 4 . Considering that the two materials are isostructural, a correlation between pseudocapacitive activity and charge transfer resistance was demonstrated. The energy density obtained from the symmetric cell of LaSrCu 0.5 Mn 0.5 O 4 was superior to that of LaSrZn 0.5 Mn 0.5 O 4 , as well as those reported for several previously studied systems that operate based on oxide anion intercalation. In addition, symmetric cells of both materials were tested for at least 6000 cycles to examine the stability of these materials.