Study On Zinc-ion Microbatteries And High-voltage Microsupercapacitors

Micro-electrochemical energy storage devices are one of the mainstream devices for micro-energy.These devices include lithium-ion microbatteries,zinc-ion microbatteries and microsupercapacitors.With the rapid development of the Internet of Things and wearable electronics in recent years,energy storage devices with high energy density are needed.Energy storage devices with high output voltages are also needed,especially for some applications.Zinc-ion batteries have caught lots of attentions for the high specific capacity and environmental friendliness of zinc anode.However,a lower specific capacity and lower energy density of the cathode material has become a bottleneck for further application.On the other hand,the voltage of a typical micro-storage device does not exceed 5 V.Although lots of researches have been done,there is still no good way to provide a sufficient high voltage,which limits the practical application of the energy storage device.This work focuses on the above two key issues:improving the energy storage performance of aqueous zinc-ion microbatteries and increasing the output voltage of microsupercapacitors.The main research contents and innovations include:（1）The research status and development trend of micro-energy storage devices at home and abroad are reviewed and analyzed in detail.The research objectives,research contents and technical implementation routes of the study are determined for the existing scientific and technical problems.At the same time,the system summarizes the key material characterization and testing techniques involved in this work.For the electrochemical testing requirements,based on the universal testing instrument,a new electrochemical testing program was designed,which can complete the flexible testing of micro-electrochemical energy storage devices.（2）A zinc-ion microbattery with zinc metal as anode,MnOOH-CNT as cathode and zinc trifluoromethanesulfonate as electrolyte was proposed and realized.Among them,a new cathode material of zinc-ion microbattery:MnOOH-CNT composite was synthesized and a new mechanism of charge storage of manganese-based zinc-ion microbattery was proposed.During the discharge of the zinc-ion microbattery,zinc ions are eluted from the anode zinc metal into the electrolyte and enter the crystal structure of the cathode material MnOOH-CNT,thereby forming zinc manganese hydrate.Experiments show that when the zinc-ion microbattery is discharged to 0.8 V,the cathode material will transform into a layered zinc-buserite with a layer spacing of 1.1 nm,which provides enough space for the storage of a large amount of zinc ions.At a constant current charge/discharge rate of 0.2 C,the cathode material MnOOH-CNT exhibits an areal specific capacity of up to 293.5μAh cm^-2,the corresponding volumetric specific capacity is 92.6 mAh cm^-3 and the mass specific capacity is 218.0 mAh g^-1.In addition,the cycle charge and discharge test was carried out at a rate of 4 C.The first Coulombic efficiency of the MnOOH-CNT zinc-ion microbattery was 92.3%and the capacity remained94.5%of the initial capacity after 1000 cycles.（3）A novel microsupercapacitor with an in-series structure is proposed,which realizes the high-voltage output of the planar microsupercapacitor for the first time.A 209 V high voltage microsupercapacitors was selected as the research object.The laser-induced graphene was used as the electrode material by CO₂ laser.The high-voltage planar in-series structure was designed by computer software.The patterned laser-induced graphene was prepared according to the designed pattern.Then it was assembled into an all-solid flexible device after coating the PVA-H₂SO₄ gel electrolyte.The results show that for a 209 V microsupercapacitor,the capacity of the device can reach 0.43μF at a charge/discharge current of 0.2μA and the capacity retention rate is 95.6%after 5000 cycles.In terms of the volumetric capacitance,the 209 V microsupercapacitor has reached 1.43μF cm^-3,exceeding the specific capacity of current commercial capacitors.In addition,the prepared high-voltage microsupercapacitors show very good flexibility.The flexibility tests show that the performance exhibited by the device in any bending state is hardly affected.Finally,we also demonstrate the successful application of high-voltage microsupercapacitors to drive wearable piezoresistive pressure sensors and crawling microrobots.In conclusion,we focuse on the core issues of aqueous zinc-ion microbatteries and microsupercapacitors,mainly solving the problem of low specific capacity for cathode materials of zinc-ion microbatteries and low output voltage for traditional micro energy storage devices.The outlook pointed out the direction for the further work.