Electrode Fabrication And Performance Studies Of Flexible Triboelectric Nanogenerators

As the progress of science and society,many flexible electronics which are characterized as multi-functional and portable have been widely used,providing services of living,social,entertainment and healthy monitoring.Due to the great mechanical flexibility,the adaptivity to most external conditions and the matching with human motion,flexible electronics have a brilliant prospect and will be an indispensable part for human in future,comparing with the traditional rigid electronics.However,most flexible electronics are still driven by conventional rigid power source like battery,which is regarded as the barrier for the further development of flexible electronics.The invention of triboelectric nanogenerator provides an alternative to tackle this problem perfectly.As an equipment that is able to transfer ubiquitous mechanical energy around the world into electric energy based on the couple effects of contact electrification and electrostatic induction,triboelectric nanogenerator makes the self-charging power system become real,and it has many unique advantages as the power source for flexible electronics.Current studies of flexible triboelectric nanogenerators mainly focus on the electrode materials,triboelectrification materials and device structure.As one of the key components,the flexibility and conductivity of the electrode have a critical impact to the quality and output performance of a flexible triboelectric nanogenerator.Some popular electrode materials involving aluminum and cooper for a flexible triboelectric nanogenerator are all rigid materials,which increases the probability of electrical output performance degradation or be damaged when it is deformed,while other novel electrode materials are mainly limited by complex fabrication process,difficulty to use directly and expensive cost.Therefore,the first aim of this thesis focuses on the method to develop the flexible electrode materials with excellent comprehensive properties,which are stable enough under deformation,contact with skin or other types of harsh conditions.The second research emphasis of this thesis is to design the device structure for a better matching between the electrode materials and electrification materials,and then a flexible triboelectric nanogenerator with great mechanical flexibility,durability and stable electrical output under deformation can be fabricated for the use of self-charging power system.According to the research focuses discussed above,starting with the material selection and device structure,this thesis develops two approaches to fabricate flexible electrode materials with outstanding mechanical property,and the flexible triboelectric nanogenerator fabricated with the developed materials is capable of matching with human motion and generating stable electrical output.The potential problems for its practical application as the self-charging power system are further studied.The main results are as follows:(1)A flexible triboelectric nanogenerator(TP-TENG)based on the freestanding Ti3C2/PVA conductive composite film had been prepared successfully.This kind of composite film is not only hydrophobic and has excellent mechanical strength,but also can keep intact under the bending and curling state.The as prepared TP-TENG exhibits tremendous potentiality to collect mechanical energy from human motion when the Ti3C2/PVA composite film is applied as electrode material.Working under different motion frequencies,TP-TENG can generate 165 V of open-circuit voltage,60 nC of charge quantity,up to 5.9?A of short-circuit current and 12.4 ?W/cm2 power density,and this level of electrical output is able to light up LEDs directly.Moreover,the integrity of the device structure and the stability of output performance of TP-TENG can be maintained even it is bended,curled,under huge tension that is thousands larger than its own mass,wetted-dried treatment and cycling tested for over 20000 times.The as-prepared self-charging power system can effectively store the electrical energy generated from TP-TENG,then discharge to drive electronic watch.(2)A flexible triboelectric nanogenerator(PL-TENG)based on the liquid conductive polymer PEDOT:PSS electrode was fabricated.In contrast to the previous work,PEDOT:PSS has extremely low Yang's module,superior conductivity and fluidity.The PL-TENG,used PEDOT:PSS as the electrode material and silicone rubber as the triboelectrification material which have low Yang's module simultaneously,can generate 265 V of open-circuit voltage,24.9?A of short-circuit current,85 nC of charge quantity and 24.8 ?W of power output,and top to 300%of maximum elongation.The stability of PL-TENG under different circumstances was testified,including being washed in physiological saline,stored for three months,bended,stretched and twisted.All the results strongly confirmed that the PL-TEN G could work stably even in some harsh conditions,without any leakage of interior liquid electrode and crack of silicone rubber.A self-charging power system that consists PL-TENG as energy supply module is capable of spending 360 s to charge a capacitor with 22 ?F to 2 V,and then the charged capacitor can discharge and power the electronics.