With reference to FIG. 11A, there is shown a full spectrum ranging from 0-1100 eV, clearly displaying the strong peaks of main elements. Also referring to FIGS. 11B to 11D, besides two satellite peaks (indicated as “Sat.”), the Ni 2p high-resolution spectrum contains typical peaks located at 855.3 eV and 872.8 eV, characteristic of Ni³⁺. The Co 2p spectrum is best fitted with two spin-orbit doublets, suggesting the existence of Co³⁺ and Co²⁺. The atomic ratio of Co³⁺ to Co²⁺ is calculated to be about 3:2 according to their peak areas integrated from the XPS spectrum. The O 1s spectrum indicates OH groups at 530.7 eV. These data show that the surface composition of the NiCoO hydroxide contains Ni³⁺, Co3+ and Co2+. Combined with the aforementioned elemental atomic ratio, the formula of NiCoO could thus be approximately expressed as Ni³⁺Co²⁺_0.4Co³⁺_0.6O₃H_0.4.

The inventors have evaluated the performances of the fabricated Zn//NiCoO battery 800A. With reference to FIG. 12A, there is shown a cyclic voltammetry (CV) profiles of the solid-state Zn//NiCo battery 800A at various scan rates demonstrate obvious redox peaks. With the increase of scan rate, the redox peaks in CVs gradually deviate from equilibrium potentials due to higher ionic transfer resistance dominated by diffusion limitation.

With reference to FIG. 12B, there is shown the galvanostatic charge/discharge (GCD) curves at high rates ranging from 5.8 C to 184 C (1 C=260 mAh g-1). All these GCD curves demonstrate typical charge and discharge plateaus with a gradually increased voltage hysteresis.