Nickel–cobalt layered double hydroxide nanoflakes combined carbonized melamine sponge for high-performance supercapacitors and pressure sensors

Nickel–cobalt layered double hydroxide (Ni–Co LDH) is a pseudocapacitance electrode material, which has attracted wide attention due to its excellent electrochemical performance, high theoretical capacitance, and a large amount of natural resources. However, the current problem is its poor electrical conductivity and the collapse and stacking of the lamellar structure during the charging and discharging process. In this paper, carbonized melamine sponge (CMS) was prepared by high-temperature calcination, and then, it is compounded with the Ni–Co LDH by further hydrothermal reaction. The resulted Ni–Co LDH nanoflake structure induced the improved electrolyte flow and ion transfer. The Ni–Co LDH@CMS electrode achieved a specific capacitance of 2039.8 mF cm−2 and 80.3% capacity retention after 5000 cycles. Then, an all-solid-state flexible asymmetric supercapacitor (ASC) was prepared by Ni–Co LDH@CMS as a cathode. When the power density is 0.699 mW cm−2, the energy density of the ASC is 66.79 μWh cm−2. The capacitor retention rate is as high as 85.2% after 5000 cycles. In addition, Ni–Co LDH@CMS composite was applied to a wearable pressure sensor for monitoring human health, which has a fast response time and recovery time of 20 ms, as well as excellent stability after 5000 cycles. This work indicates that Ni–Co LDH@CMS composite has an excellent prospect as a kind of flexible versatile material.