Exploring BaxCoO2 as a potential cathode material for rechargeable batteries

Abstract

Layered cobalt oxides are emerging as a pivotal class of cathode materials due to their high theoretical energy density, tunable interlayer spacing for efficient ion diffusion, and structural resilience under electrochemical cycling. Here, we report the synthesis of barium cobaltite (Ba_xCoO₂, x ≈ 0.34) through a two-step solidstate reaction coupled with ion exchange, establishing a stable layered structure consisting of alternating Ba-O layers and edge-shared CoO6 octahedral sheets. This unique architecture provides an expanded interlayer spacing (c-axis: 1.23 nm) and efficient Li⁺ diffusion channels, enabling a lithium-ion battery (LIB) with the Ba_xCoO₂ cathode to achieve ultrahigh reversible capacities of 820.7 mAh·g^-1 at 0.1C and 483.2 mAh·g^-1 at 5C, along with 99.37% Coulombic efficiency retained over 1000 cycles, demonstrating remarkable cycling stability. Comparative studies on a sodium-ion battery (SIB) also reveal the superior capacity of the LIB, attributed to smaller ionic radius of Li⁺ and stabilized electrode.electrolyte interface. These results demonstrate that the combination of structural resilience and fast ion kinetics position Ba_xCoO₂ as a promising candidate for high-energy-density storage systems. Further optimization of the Ba/Co ratio and defect engineering may unlock enhanced cyclability for practical applications.