The Design And Efficiency Enhancement Research Of Nickel Based Photorechargeable Device

Photorechargeable Device refer to devices that directly convert and store solar energy,which can well solve a series of problems caused by the uneven distribution of solar energy in time and space.The most important parameter of a photorechargeable device is its overall efficiency.The mismatch of the photovoltaic part and energy storage part is a major obstacle to improving this efficiency.By device selection,structural design,and material synthesis,the working states of the photovoltaic part and energy storage part are matched,enabling both to maintain their original device performance during the photo charging process.(Through device selection,structural design,and material synthesis,the working states of the photovoltaic and energy storage components are optimized-allowing them to maintain their original device performance during the photocharging process.)This greatly improves the overall efficiency of photorechargeable device,while also effectively improving their practical value.This thesis focuses on the matching of photovoltaic and energy storage part to achieve a high-efficiency photorechargeable device.The main research contents are as follows:Nanosized battery-type materials applied in electrochemical capacitors can effectively reduce a series of problems caused by low conductivity and large volume changes.However,this approach will lead to the charging and discharging process being dominated by capacitive behavior,resulting in a serious decline in the specific capacity of the material.By controlling the material particles to an appropriate size and a suitable number of nanosheet layers,the battery-type behavior can be retained to maintain a large capacity.Here,Ni(OH)2,which is a typical battery-type material,is grown on the surface of reduced graphene oxide to prepare a composite electrode.By controlling the dosage of the nickel source,the composite material with an appropriate Ni(OH)2 nanosheet size and a suitable number of layers was prepared.The highcapacity electrode material was obtained by retaining the battery-type behavior.The prepared electrode had a specific capacity of 397.22 mA h·g-1 at 2 A·g-1.The prepared electrochemical capacitor had an energy density of 30.91 Wh·kg-1 at a power density of 1319.86 W·kg-1 and the retention rate could reach 79%after 20,000 cycles.An optimization strategy was advocated that retains the battery-type behavior of electrode materials by increasing the size of nanosheets and the number of layers,which can significantly improve the energy density while combining the advantage of the highrate capability of the electrochemical capacitor.The preparation of high energy density energy storage devices creates conditions for the construction and preparation of highperformance photorechargeable device.Ni(OH)2 has low production cost and high theoretical specific capacity,while on account of the poor electronic conductivity,it shows inferior electrochemical performance including cycling stability and rate capability.The composite materials were built by in situ grown Ni(OH)2 nanosheets on reduced graphene oxide,and employed the fewer-defect rGO to build a three-dimensional conductive network that provides outstanding conductivity.The specific capacitance of the Ni(OH)2-rGO electrode is 2776 F·g-1 at 2 A·-g-1 and even 1570 F·g-1 at 50 A·g-1,demonstrating remarkable rate capability.It indicates that the combination of the nano-grown Ni(OH)2 and rGO conductive substrate shortens the ion diffusion path and increases the electron transfer rate;hence,the composite rate capability has been significantly improved.The composite materials and active carbon were combined to be an asymmetric supercapacitor,which had a high energy density of 39.24 Wh·kg-1 at 1962 W·kg-1.After 10000 cycles at 5 A·g-1,the capacity retains 91.4%.Electrochemical capacitors with large capacity and high-rate performance will be of great importance to building high-efficient photorechargeable device.A photorechargeable device can generate power from sunlight and store it in one device,which has a broad application prospect in the future.However,if the working state of the photovoltaic part in the photorechargeable device deviates from the maximum power point,its actual power conversion efficiency will reduce.The strategy of voltage match on the maximum power point was reported to achieve a high overall efficiency(ηoa)of the photorechargeable device assembled by a passivated emitter and rear cell(PERC)solar cell and Ni-based asymmetric capacitors.By matching the voltage of the maximum power point of the photovoltaic part,the charging characteristics of the energy storage part can be optimized to achieve a high actual power conversion efficiency for the photovoltaic part(ηpv).The ηpv of a Ni(OH)2-rGObased photorechargeable device is 21.53%,and the ηoa is up to 14.55%.This strategy can promote further practical application for the development of photorechargeable devices.By constructing a photorechargeable device based on the strategy of voltage matching on the maximum power point,it is possible to significantly enhance the actual power conversion efficiency of the photovoltaic part during the photo charging process.Furthermore,the energy storage efficiency during this process also plays a critical role in determining the overall efficiency of the system.Using alkali etched NiAl LDH instead of Ni(OH)2-rGO composite material,an energy storage part with the highest charge and discharge efficiency during the photo charging process was prepared by changing the etching time.The alkali etched NiAl LDH not only demonstrates a substantial enhancement in energy storage efficiency during the photo charging process,but also accurately aligns its optimal inflection point voltage and fully charged voltage with the solar cell’s maximum power point voltage.As a result,it achieves both high power conversion efficiency and high energy storage efficiency during the photo charging process,ultimately leading to an ideal overall efficiency.The device ultimately exhibits an overall efficiency of 18.30%,has a power conversion efficiency of up to 22.53%,and also achieves an energy storage efficiency of 81.24%.The preparation of a high-efficiency photorechargeable device is of great significance for its popularization and further research.