Hydrothermal Synthesis of Nickel Phosphate Nanorods for High‐Performance Flexible Asymmetric All‐Solid‐State Supercapacitors

Abstract

Ni20[(OH)12(H2O)6][(HPO4)8(PO4)4]·12H2O nanorods are successfully synthesized via a one‐pot hydrothermal reaction. A high‐performance flexible asymmetric all‐solid‐state supercapacitor based on the obtained Ni20[(OH)12(H2O)6][(HPO4)8(PO4)4]·12H2O nanorods (positive electrode) and graphene nanosheets (negative electrode) is successfully assembled. It is the first report of this nanomaterial applied for all‐solid‐state supercapacitors. Interestingly, a maximum volumetric energy density of 0.446 mW h cm−3 at a current density of 0.5 mA cm−2 and a maximum power density of 44.1 mW cm−3 at a current density of 6.0 mA cm−2 are achieved by the as‐assembled device. What's more, the device also shows excellent mechanical flexibility and little capacitance change after over 5000 charge/discharge cycles at a current density of 0.5 mA cm−2.

High capacitive amorphous barium nickel phosphate nanofibers for electrochemical energy storage

“…22 Besides metal oxides which are widely studied as pseudocapacitive materials, [23][24][25][26][27] limited research has shown that onedimensional (1D) phosphate materials can also be effective supercapacitive materials. Pang 30 which were made by hydrothermal method. Beneting from the high pressure and heating of hydrothermal reaction condition, the material showed good crystallinity and exhibited higher energy density compared to conventional carbon based materials.…”

Metal Phosphides and Phosphates‐based Electrodes for Electrochemical Supercapacitors

“…Nickel Phosphates : In the past few years, several studies have attempted to establish nickel phosphates as pseudocapacitive materials, because of their relatively high specific capacitance . Pramanik et al developed an effective way to prepare nanoporous nickel phosphates by thermolysis of the corresponding precursor materials.…”

“…Remarkably, no obvious capacitance decrease took place for the electrode over 3000 cycles at 30.0 A g −1 , implying the excellent cycling stability. Zhao et al have presented a facile hydrothermal approach for producing VSB‐5 nanorods, which showed a high surface area of 488 m 2 g −1 . A flexible asymmetric all‐solid‐state supercapacitor (VSB‐5 nanorod as the positive electrode, and graphene nanosheet as the negative electrode) was shown with great performances and excellent mechanical flexibility.…”

High‐Performance Flexible Solid‐State Asymmetric Supercapacitors based on Ordered Mesoporous Cobalt Oxide

“…Although SCs have many advantages compared to rechargeable batteries and fuel cells, their low energy density limits practical applications. Recently, asymmetric SCs (ASCs) with battery‐type Faradaic electrodes showed promise as alternative to SCs . According to the equation E =( C × U 2 )/2, the energy density ( E ) increases when as either the device capacitance ( C ) or cell voltage ( U ) increases.…”

“…Recently, asymmetric SCs (ASCs) with battery‐type Faradaic electrodes showed promise as alternative to SCs . According to the equation E =( C × U 2 )/2, the energy density ( E ) increases when as either the device capacitance ( C ) or cell voltage ( U ) increases. Compared to symmetric SC devices, ASCs can significantly increase the operating voltage in aqueous electrolytes by combining voltage windows from two electrodes.…”