Fabrication And Performance Investigation Of Printed Flexible Supercapacitors Based On Pseudocapacitive Nanomaterials

Flexible supercapacitors（SCs）show a broad application prospect in portable and wearable electronics for their high power density,short charging time,long cycling stability,flexibility and safety.However,some critical challenges are still remained for flexible SCs,such as low energy density,complicated fabrication process,expensive cost and insufficient mechanical flexibility.In order to solve these problems,the active electrode materials and fabrication techniques for SCs applications have attracted lots of research interests.On this basis,this work focuses attempts to solve these problems on active electrode materials,fabrication process and structure design of flexible SCs,based on preparation of high performance pseudocapacitive nanomaterials and screen printing electronic fabrication technique,the fabrication and electrochemical performance of printed flexible SCs based on pseudocapacitive nanomaterials are carefully studied.Specific works have been carried out in the following areas:1.Fabrication of printed flexible SCs based on Mn O₂/PPy nanocomposite and electrochemical performance study.Mn O₂/PPy nanocomposite are synthesized through wet chemistry method,and the effects of different Mn O₂/PPy mole ratio for Mn O₂/PPy nanocomposite are invesgatied.The optimized Mn O₂/PPy nanocomposite exhibit high specific capacitance of 293.8 F g^-1 and good capacitance retention of 84.3%after 5000cycles.The printed flexible SCs based on Mn O₂/PPy nanocomposite are firstly fabricated on flexible nitrile rubber and exhibit good electrochemical performance,such as high areal capacitance of 22.6 m F cm^-2,high energy density of 0.00201 m Wh cm^-2,88.2%capacitance retention after 3000 cycles and good capacitance retention at different bending conditions,which show great potential for wearable electronics application.2.Fabrication of printed flexible SCs based on Ag@PPy nanocomposite and electrochemical performance study.Ag@PPy nanocomposite are prepared through a simple self-template in-situ oxidative polymerization reaction,the Ag@PPy nanocomposite prepared with CH₃COO^-exhibit best electrochemical performance of high specific capacitance(576.6 F g^-1)and good cycling ability（96.2%capacitance retention after 10000 cycles）.The printed flexible SCs based on Ag@PPy nanocomposite are firstly fabricated on flexible PET and exhibit excellent capacitive features,including high areal capacitance of 48.5 m F cm^-2,high energy density of0.00433 m Wh cm^-2,superior stability of 82.6%after 10000 cycles and remarkable mechanical flexibility of 77.6%after 1000 bending times.The obtained SCs can also be connected in series or in parallel to extent the voltage window or capacitance,and the connected SCs can stably light up LEDs.Utilization of the simple,fast and facile screen printing techinique,serveal flexible SCs can be easily obtained at the same time,which further highlighting the potential application.3.Fabrication of printed ultraflexible asymmetric SCs based on Ag@PPy@Mn O₂nanocomposite and electrochemical performance study.Combining the Mn O₂with optimized Ag@PPy nanocomposite to obtain Ag@PPy@Mn O₂ nanocomposite through hydrothermal method.The obtained Ag@PPy@Mn O₂ nanocomposite exhibit high areal capacitance of 426.3 m F cm^-2 and good cycling ability of 98.7%capacitance retention after 10000 cycles.The printed ultraflexible and stretchable asymmetric SCs based on Ag@PPy@Mn O₂ nanocomposite are firstly fabricated on flexible textile and exhibit excellent capacitive features,including high voltage window of 1.6 V,high areal capacitance of 95.3 m F cm^-2,large energy density of 0.0337 m Wh cm^-2,good cycling stability（90.8%retention after 5000 cycles）,excellent mechanical flexibility and superior stretchable stability（86.2%retention after 40%stretching strain）,which make it possible for the tandem asymmetric SCs keeping stable to light up a LED at various flexible conditions.The innovative study of ultraflexible and stretchable asymmetric SCs with remarkable mechanical flexibility and superior stretchable stability provide references for fabricating high-performance flexible stretchable SCs.4.Fabrication of structure-designed printed flexible SCs based on porous Ni Co₂O₄nanowires and electrochemical performance study.Porous Ni Co₂O₄ nanowires are prepared through a simple hydrothermal reaction followed by a calcinations treatment.The unique hierarchical porous one-dimensional nanostructures effectively increase the conductivity and ion transfer efficiency.The obtained porous Ni Co₂O₄ nanowires exhibit high specific capacitance of 1481.9 F g^-1 and good cycling ability of 98.6%capacitance retention after 10000 cycles.Utilization of the screen printing technique,the structure of SCs based on porous Ni Co₂O₄ nanowires have been firstly systematically studied to construct smart SCs on flexible PET.The optimized printed flexible SCs exhibit excellent capacitive features,including high areal capacitance of35.3 m F cm^-2,large energy density of 0.00687 m Wh cm^-2,good cycling stability(91%retention after 5000 cycles and excellent mechanical flexibility,which make it possible for the tandem SCs stably lighting up a LED.Additionly,the SCs can be fabricated as various patterns with artistic design on various flexible substrates（PET,paper and textile）,demonstrating great potential for commercial application.In this work,the performance of SCs is optimized by systematical structural design,revealing the influence of different structures for the performance of SCs,providing references for performance evalution and optimization of structure of flexible SCs.