Stacking fault disorder induced by Mn doping in Ni(OH)₂ for supercapacitor electrodes

Mn-doping engineering route has been demonstrated an effective way to enhance the electronic conductivity of α-Ni(OH)₂ as a hybrid supercapacitor electrode material. However, the problem of limited cycling lifetime remains unsolved and the structural evolution of Mn-doping at the atomic level is still under debate. Herein, a novel life span improving strategy is proposed to modulate the electronic configuration and the layer stacking mode of Mn doped Ni(OH)₂ (NiMn-LDH) in situ grown on nickel foam by controlling the Mn doping level (~6% atomic) and occupied site (3a site only). XRD, EXAFS and DFT calculations have been employed to confirm that the modified electronic configuration due to Mn doping induces local contraction of metal-O/metal bond length and increases curve degree within ab planes, which further introduces special stacking fault disorder between layers to stabilize the structure. Finally, the suitable-dose Mn doped NiMn-LDH exhibits high capacity (1498 C g⁻¹ at 2 A g⁻¹), excellent rate capability and superior cycling performance (almost 100% capacity retention after 30,000 cycles at 50 A g⁻¹). This work demonstrates modulating local environment by suitable dose of metal doping can boost the cycling performance of nickel-based electrode materials for applications in energy storage and conversion.