Ag nanoparticles modified (K0.5Na0.5)NbO3/PVDF flexible energy harvester and its performance
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摘要: 将机械能转换为电能的压电能量收集器可为便携式可穿戴电子器件提供持续、独立的供电方案,促进柔性电子技术向智能化、集成化、多功能化方向发展。本文采用光还原法制备了Ag纳米颗粒修饰的铌酸钾钠(KNN)颗粒并将其与聚偏氟乙烯(PVDF)复合,得到Ag-KNN/PVDF压电复合薄膜。采用热压法在两层PVDF中复合Ag-KNN/PVDF薄膜,得到三明治结构的柔性复合压电薄膜(PAKP)及压电柔性能量收集器。研究结果表明:当Ag摩尔分数为1%时,PAKP柔性复合薄膜的极性β相最大,且压电输出性能最佳,输出电压可达6.39 V,是无Ag修饰样品的1.43倍,器件的最大瞬时功率为150.5 nW。经过3000次循环测试后,器件的电压输出幅度无明显变化。将其固定于自行车车架上,收集自行车行进中的机械能可使220 nF电容在200 s内充电至1.2 V,表明其在低功耗电子器件自供电领域具有良好的应用前景。Abstract: The piezoelectric energy harvester which can convert mechanical energy into electrical energy provides a continuous and independent power supply scheme for portable wearable electronic devices, and promotes the development of flexible electronic technology in the direction of intelligence, integration and multi-function. In this paper, Ag nanoparticles decorated potassium sodium niobate (KNN) particles were synthesized by the method of photoreduction, which were compounded with polyvinylidene fluoride (PVDF) to obtain Ag-KNN/PVDF piezoelectric composite films. Then, the flexible composite piezoelectric films with sandwich structure (PAKP) and piezoelectric flexible energy collectors were prepared by thermal pressing Ag-KNN/PVDF film with upper and lower layers of PVDF. The results show that when the amount of Ag nanoparticle is 1% mole fraction, the piezoelectric output performance of PAKP flexible composite film is the best, the output voltage can reach 6.39 V, which is 1.43 times that of the sample without Ag decoration, and the maximum instantaneous power of the device is 150.5 nW. After 3000 cycle tests, the voltage output amplitude of the device has no obvious decline. The 220 nF capacitor can be charged to 1.2 V in 200 s by fixing it on the bicycle frame and collecting the mechanical energy of the bicycle, which shows that it has a good application prospect in the field of self-power supply of low-power electronic devices.
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图 1 三明治结构的柔性复合压电薄膜(PAKP)的制作工艺流程
Figure 1. Manufacturing process of flexible piezoelectric energy harvester based on flexible composite piezoelectric films with sandwich structure (PAKP) composite film
PVDF—Polyvinylidene fluoride; KNN—Potassium sodium niobate; PET—Polyethylene terephthalate; DMF—N,N-dimethylformamide
图 2 (a) 水热法制备铌酸钾钠(KNN)的SEM图像;(b) 球磨KNN的SEM图像;(c) Ag含量为摩尔分数1%的Ag-KNN颗粒的低倍TEM图像; (d) 高倍TEM图像(插图为相应区域的高分辨TEM图像)
Figure 2. SEM images potassium sodium niobate (KNN) samples of prepared by hydrothermal method (a) and after ball milling (b); TEM images of Ag-KNN particles with 1% mole fraction Ag in low magnification (c) and high magnification (d) (The insert is the high-resolution TEM images)
图 7 不同Ag含量的PAKP复合薄膜的漏电流测试 ((a) 0-PAKP;(b) 0.5-PAKP;(c) 1-PAKP;(d) 2-PAKP;(e) 3-PAKP);320 kV/cm、1 Hz条件下电滞回线图 (f)
Figure 7. Leakage current test of PAKP film with different Ag amount ((a) 0-PAKP; (b) 0.5-PAKP; (c) 1-PAKP; (d) 2-PAKP; (e) 3-PAKP); Ferroelectric hysteresis loops (P-E) with 320 kV/cm, 1 Hz (f)
图 9 不同结构PAKP复合压电能量收集器(PEH):(a) 开路电压;(b) 短路电流;(c) 1-PAKP复合压电能量收集器在加速度为1g~5g作用时的电压输出;(d) 1-PAKP压电能量收集器在正反接测试时的电压输出
Figure 9. PAKP piezoelectric energy harvester (PEH) with different structures: (a) Open-circuit voltage; (b) Short-circuit current; (c) Voltage output of 1-PAKP PEH by 1g-5g acceleration; (d) Voltage output of 1-PAKP PEH in forward and backward connection mode
g—Acceleration of gravity
图 11 (a) 1-PAKP压电能量收集器安装于单车的实物照片;(b) 自然状态照片;(c) 磁铁斥力作用下弯曲状态照片;(d) 220 nF瓷片电容在单车运动过程中电容两端电压随时间变化关系图;(e) 单车在运动过程中压电能量收集器的电压随时间变化图谱
Figure 11. (a) Photos of 1-PAKP PEH fixed on the bicycle; (b) Photos of natural state; (c) Photos of bending state by magnet repulsion; (d) Voltage-time relation of 220 nF ceramic chip capacitor while the bicycle is moving; (e) Voltage-time relation of PEH while the bicycle is moving
表 1 样品制备条件
Table 1. List of specimens with different films and Ag amount
Sample Structure Ag mole
fraction/%S-AKP Ag-KNN/PVDF (monolayer) 1 0-PAKP PVDF/S-AKP/PVDF (three layers) 0 0.5-PAKP PVDF/S-AKP/PVDF (three layers) 0.5 1-PAKP PVDF/S-AKP/PVDF (three layers) 1 2-PAKP PVDF/S-AKP/PVDF (three layers) 2 3-PAKP PVDF/S-AKP/PVDF (three layers) 3 -
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