Application Of Zinc Cobalt And Nickel Hydroxide In Supercapacitor

Energy storage device, especially supercapacitor, has been played a more important role in daily life, such as electronic device, micro-detector and so on. In this paper, we used the ZnCo₂O₄ as the electrode materials, designed new class of flexible all-solid-state planar-integrated fiber supercapacitors（FSC）. What is more, we also reported on a new high performance flexible on-chip microsupercapacitors（MSC）with two-dimensional Ni（OH）₂ nanoplates as the electrode material.The main research results obtained can be summarized as following:（1） one dimensional ZnCo₂O₄ nanorods were synthesized on the a nickel wire via a simple hydrothermal method free of any template and catalyst. After that, we use the ZnCo₂O₄ nanorods on a Ni wire electrode as the work electrode; a platinum electrode and a saturated calomel electrode（SCE） were used as the counter electrode and reference electrode, 3 M KOH as the electrolyte in a three-electrode cell, respectively.In three-electrode system, the prepared ZnCo₂O₄ nanorods exhibited obvious pseudocapacitance features with a pair of well-defined redox peaks within 0–0.45 V（vs. SEC）. The result shows electrochemistry stability, we can find that the CV curve have a good symmetry, revealing the redox reaction of ZnCo₂O₄ nanorods in KOH is highly reversible, which can be attributed to one dimensional nanotopography of ZnCo₂O₄ nanorods on the Ni wire substrate. Above that, it makes it possible to consider it as an attractive candidate in supercapacitors due to its superior electrochemistry stability.（2） In order to evaluate the application of the supercapacitor, we used the nickel wire to fabricate a fiber solid-state supercapacitor directly. In two-electrode system,the FSC has a high specific capacitance of 10.9 F/g at a scan rate of 30 mV/s, an energy density of 76 mWh/kg and a power density of up to 1.9 W/kg. Good electrochemical performance stability was maintained at 92% of 2 mA after 3500charge/discharge cycles. Meanwhile, the performance of our coaxial FSC does not decay under the different bending states（30°, 45°, 60°, 90°）, which demonstrated that our device has excellent flexibility. In view of their excellent electrochemical performance and facile and cost-effective synthesis, these ZnCo₂O₄ nanostructures might hold great promise as advanced electrode materials for high-performance supercapacitors. Furthermore, by decreasing the diameter of the metal fiber, flexiblefiber supercapacitors with smaller diameter and size are expected to be fabricated,which will make it possible to weave the fiber supercapacitor into design patterns for wearable electronic applications.（3） We synthesized two-dimensional Ni（OH）₂ nanoplates via a simple hydrothermal method free of any template and catalyst. After that, we use the Ni（OH）₂ nanoplates on a foam Ni electrode as the work electrode; a platinum electrode and a saturated calomel electrode（SCE） were used as the counter electrode and reference electrode, 2 M NaOH solution was used as the electrolyte in a three-electrode cell, respectively. In three-electrode system, the prepared Ni（OH）₂nanoplates exhibited obvious pseudocapacitance features with a pair of well-defined redox peaks with in 0–0.45 V（vs. SEC） and one pair of redox peaks can be clearly seen in 0.3–0.35 V and 0.2–0.25 V. The result shows electrochemistry stability, we can find that the CV curve have a good symmetry, revealing the redox reaction of Ni（OH）₂ nanoplates in NaOH is highly reversible. Above that, suggested that Ni（OH）₂nanoplates have a excellent pseudocapacitance performance, makes it as an attractive candidate in supercapacitors.（4） In order to be satisfied with the application of the microelectromechanical systems or medical microrobots, we report on a new high performance flexible on-chip MSC with two-dimensional Ni（OH）₂ nanoplates as the electrode material by a method of photolithography. In two-electrode system, the FSC has achieved a specific capacitance of 8.80 F/cm3 at the scan rates of 100 mV/s, losing only 0.20% of its original value after 10,000 charge/discharge cycles. Besides, the MSCs reached an energy density of 0.59 mWh/cm3 and a power density up to 1.80 W/cm3, which is comparable to traditional carbon-based devices. The flexible MSCs exhibited good electrochemical stability when subjected to bending at various conditions, illustrating the promising application as electrodes for wearable energy storage.