The research on supercapacitors has been attractive due to their large power density, fast charge/discharge speed and long lifespan. The electrode materials for supercapacitors are thus intensively investigated to improve the electrochemical performances. Various transition metal layered double hydroxides (LDHs) with a hydrotalcite-like structure have been developed to be promising electrode materials. Earth-abundant metal hydroxides are very suitable electrode materials due to the low cost and high specific capacity. This is a review paper on NiMn LDHs for supercapacitor application. We focus particularly on the recent published papers using NiMn LDHs as electrode materials for supercapacitors. The preparation methods for NiMn LDHs are introduced first. Then, the structural design and chemical modification of NiMn LDH materials, as well as the composites and films derived from NiMn LDHs are discussed. These approaches are proven to be effective to enhance the performance of supercapacitor. Finally, the reports related to NiMn LDH-based asymmetric supercapacitors are summarized. A brief discussion of the future development of NiMn LDHs is also provided.

Li-rich manganese-based layered cathode Li_1.2Mn_0.54Ni_0.13Co_0.13O₂ (LMNCO) nanotubes are synthesized by electrospinning and surface coated with different amounts of amorphous Al₂O₃.

Hierarchical composite films grown on current collectors are popularly reported to be directly used as electrodes for supercapacitors. Highly dense and conductive NiCo₂O₄ nanowires are ideal backbones to support guest materials. In this work, low crystalline MnO₂ nanoflakes are electrodeposited onto the surface of NiCo₂O₄ nanowire films pre-coated on nickel foam. Each building block in the composite films is a NiCo₂O₄–MnO₂ core–shell nanowire on conductive nickel foam. Due to the co-presence of MnO₂ and NiCo₂O₄, the MnO₂@NiCo₂O₄@Ni electrode exhibits higher specific capacitance and larger working voltage than the NiCo₂O₄@Ni electrode. It can have a high specific capacitance of 1186 F·g⁻¹ at 1 A·g⁻¹. When the core–shell NiCo₂O₄–MnO₂ composite and activated carbon are assembled as a hybrid capacitor, it has the highest energy density of 29.6 Wh·kg⁻¹ at a power density of 425 W·kg⁻¹ with an operating voltage of 1.7 V. This work shows readers an easy method to synthesize composite films for energy storage.