Synthesis and electrochemical characteristics of xLi2MnO3–(1−x)Li(Mn0.375Ni0.375Co0.25)O2 (0.0 ≤ x ≤ 1.0) thin film cathode for lithium rechargeable micro batteries

• Synthesis of thin film composite cathodes for rechargeable micro batteries.
• Structure-property relation of thin film and bulk composite cathode.
• The discharge capacity of composite cathode is measured to be 217 μAhcm−2.

We have compared the structure, microstructure, and electrochemical characteristics of xLi2MnO3–(1−x)Li(Mn0.375Ni0.375Co0.25)O2 (0.0 ≤ x ≤ 1.0) thin films with their bulk cathode laminate counterparts of identical compositions. Pure Li(Mn0.375Ni0.375Co0.25)O2 as well as the synthesized composite films partially transform into cubic spinel structure during charge–discharge cycling. In contrast, such layered to spinel phase transformation has only been identified in bulk cathode laminates with x ≥ 0.75. At a current density 0.05 mAcm−2, the discharge capacity of Li(Mn0.375Ni0.375Co0.25)O2 thin film was measured to be ∼60 μAhcm−2. The discharge capacity (∼217 μAhcm−2) was markedly improved in x∼0.5 composite thin film. The capacity retention after 20 charge discharge cycles are improved in composite films; however, their capacity fading could not be eliminated completely.

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