Modulation of p- and n-Type Transitions in Co3- x Nix O4 Nanoparticles for Enhanced Supercapacitor Electrochemical Performance

The efficient storage of electrons and the type of conduction in semiconductor materials are important factors in determining their electrochemical performance. However, the interaction between these two factors is often overlooked by researchers. In this study, the effects of Ni doping at Co3- x Nix O4 nanoparticles on the electronic storage form of the material and resulting changes in the conduction p/n-type are reported. Theoretical calculations demonstrate that n-type conduction with high effective mass of electrons contributes significantly to the redox reaction of electrode materials and is beneficial for improving electrochemical performance. The specific capacitance of Co3- x Nix O4 (x = 0.67) electrode material is 10 times larger than that of Co3 O4 due to enhanced orbital hybridization caused by Ni atom doping. The findings provide new directions for exploring the mechanism of conductive type conversion of materials and offer insights beyond the traditional approach of considering doping content alone.

A facile synthesis of a NiMoO4@metal-coated graphene-ink nanosheet structure towards the high energy density of a battery type-hybrid supercapacitor

Recently, reagent-based electrode materials (urea, ammonium fluoride, hexamethylenetetramine, l-cysteine, acetic acid, and triethylamine) have received great attention in numerous applications (e.g., solar cells, fuels cells, and battery-type hybrid supercapacitors (BHSCs)). Herein, we designed a wrinkle-type nanosheet structure with a mixture of NiMoO4 using triethylamine via a hydrothermal synthesis. The dual metal ions of Ni2+/Ni3+ and Mo2+/Mo3+ can significantly boost the energy storage performance by the support of triethylamine. NiMoO4 was deposited onto a nickel foam substrate without any binders, and the electrode exhibited a high specific capacitance/capacity of 415.66 F g-1 (249.4 mA h g-1) at 8 mA cm-2 with a good long-term cycling performance over 5000 cycles. Moreover, we assembled flexible HSCs (NiMoO4@MCG-ink) as the core, and the outer material delivered a high specific energy of 40.14 W h kg-1 at 1066.39 W kg-1. The HSC device demonstrated excellent long-term durability with a capacity retention of 99%, and various bending conditions were also tested for flexibility of the device after 5000 cycles. Furthermore, a series of two HSC devices were efficient to light up red and green light-emitting diodes (LEDs) for about 60 minutes, indicating its potential applications in energy storage devices. Hence, our work provides new insights into the preparation of new electrode materials for high energy storage performance of lithium-ion batteries (LIBs) and SCs.