Design And Construction Of Wearable Solar Charging Self-powered System

Wearable solar charging self-powered system suffers burgeoning development which encompasses in various of emerging technologies such as energy conversion technology,energy storage technology,wearable flexible electronics,and bio-intelligent sensing.Such cutting-edge multi-functional systems serve to broad application prospects in human-computer interaction(VR glasses,smart displays,and vital signs monitoring).However,the tough missions of the development still lie in the unacceptable overall energy conversion efficiency,low compatibility between energy conversion systems and energy storage systems,and poor lifespan in wearable scenarios.In light with these,we design the wearable solar charging self-powered system according the following two aspects:(1)By selecting solar cell system with high photoelectric conversion efficiency whilst constructing energy storage system of high energy storage efficiency,the higher overall energy conversion efficiency is obtained;(2)Utilizing a variety of flexible electronic fabricating technology(printing technology,soft package technology and laser cutting technology),ensuring good compatibility between energy storage devices and solar cells.The main research contents of this thesis are as follows:(1)A lithium-ion hybrid capacitor was assembled employing lithium titanate as the negative electrode and commercial activated carbon as the positive electrode respectively.Furthermore,a flexible lithium-ion hybrid capacitor was prepared using soft-package battery technology,achieving an energy density of up to 60 Wh kg-1.The flexible lithium-ion hybrid capacitor was used as an energy storage system to integrate with a flexible perovskite solar cell,achieving the construction of an integrated wearable solar-charge self-powered system.The peak overall energy conversion efficiency reached 8.41%.In addition,such flexible integrated unit could supply to the pressure sensor to detect the vital signs of the human body.(2)A quasi-solid magnesium ion asymmetric supercapacitor was assembled using vanaditum nitride as the negative electrode,manganese dioxide as the positive electrode,and magnesium sulfate as the electrolyte respectively.Aforementioned supercapacitor achieved a high volume energy density of 13.1 mWh cm-3.Further,we used screen printing technology to prepare flexible micro magnesium ion asymmetric supercapacitors.Finally,we integrated the above-prepared micro-magnesium ion asymmetric supercapacitors with flexible silicon-based solar cells,successfully constructing a wearable solar charging self-powered unit with a high overall energy conversion efficiency of 11.95%and durable solar charge cycle stability(capacity retention rate remains 95%after 100 circles).(3)Using nickel-cobalt double-layer hydroxide as the positive electrode and zinc flake as the negative electrode,an alkaline zinc-ion battery was assembled with outstanding rate performance.At a current density of 1 A g-1,the mass specific capacity was 278 mAh g-1.When the current density was increased to 20 A g-1,the capacity was maintained at 274 mAh g-1,and the capacity retention rate reached a significant 98.56%.Further,the laser cutting technology was employed to fabricate flexible micro alkaline zinc-ion batteries,exhibiting excellent flexibility and high area energy density(136 ?Wh cm-2).Finally,we integrated the micro batteries with gallium arsenide solar cells and designed a wearable integrated light-charge self-powered device with the highest energy conversion efficiency of 23.11%.