Synthesis of nickel-copper layered double hydroxides for asymmetric supercapacitors by low-temperature chemical co-precipitation method

In this paper, a straightforward low-temperature chemical co-precipitation method for the preparation of nickel-copper layered double hydroxide (L-Ni₄CuLDH) was reported. The doping of copper element makes the stacking morphology of the composite material change obviously, from large block stacking to small block stacking, which enables greater exposed surface area of the L-Ni₄CuLDH, increases the material contacts of the redox reaction and promotes electrode reaction. At 1 A g⁻¹, the specific capacity of L-Ni₄CuLDH electrode is 1656.9 F g⁻¹. After it is increased to 20 A g⁻¹, the rate performance is 69.7%. Furthermore, an asymmetric supercapacitor (ASC) was prepared using L-Ni₄CuLDH composite as cathode and activated carbon (AC) as anode, which has an energy density of 45.40 Wh kg⁻¹ at 800 W kg⁻¹ (20.22 Wh kg⁻¹ at 8000 W kg⁻¹). Besides, after 10,000 cycles at 5 A g⁻¹, 73.1% of its initial capacitance remained.