Perovskite KNi0.1Co0.9F3 as a pseudocapacitive conversion anode for high-performance nonaqueous Li-ion capacitors and dual-ion batteries

Abstract

Perovskites K–Ni–Co–F (denoted as KNCF) with various Ni/Co ratios have been introduced as high-performance anodes for nonaqueous Li-ion capacitors (LICs) and dual-ion batteries (DIBs). The optimal KNCF (Ni/Co = 1-6) material possesses the stoichiometric formula of KNi_0.1Co_0.9F₃ with cubic nanocrystal morphology and hierarchical porous structure. The KNCF (1-6) electrode shows a typical surface conversion reaction mechanism with a synergistic contribution of Ni and Co electroactive species for Li-ion storage. The KNCF (1-6)//activated carbon (AC) LIC with the anode precharged (or prelithiated) exhibits much higher energy/power densities and cycling stability than the non-precharged one, moreover, the overall performance is better than those of the KNCF (1-0)//AC and KNCF (0-1)//AC LICs. Interestingly, the constructed KNCF (1-6)//AC + LiFePO₄ (LFP) (1 : 1) LIC exhibits better performance than the KNCF (1-6)//AC LIC by using a capacitor–battery hybrid cathode with higher specific capacity, and the performance of the KNCF (1-6)//AC LIC is also enhanced by the precharging treatment of both the KNCF (1-6) anode and AC cathode. The designed KNCF (1-6)//graphite (918) DIB exhibits better performance than the other three DIBs with the 918 + AC (1 : 1), 918 + LFP (1 : 1) and 918 + AC + LFP (1 : 1 : 1) cathodes. Furthermore, the designed LICs and DIBs also show a remarkable behavior at low (−20 °C) and high (40 °C) temperatures.