Construction of a high-efficiency piezoelectric nanogenerator based on in situ polarization of PVDF nanofiber films by electrospinning
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摘要: 全球化石能源危機和環境污染問題使得高效利用綠色、可再生清潔能源成為大勢所趨。機械能因其豐富、易獲取和無污染等特點被認為是理想的替代能源之一。壓電納米發電機(PENG)可以將環境中的機械能轉化為電能,為電子設備提供動力。然而,傳統的壓電材料必須通過電極化誘導偶極子排列才能獲得壓電性能,增加了器件制備的工序和能耗。同時,當去除外加電場時會發生退極化效應,致使壓電材料的性能穩定性下降。通過靜電紡絲法紡絲過程產生的強電場和機械拉伸使聚偏二氟乙烯(PVDF)納米纖維晶體中的偶極子定向排列,從而實現原位極化,獲得了高電活性β相達78.7%的PVDF納米纖維薄膜。基于該薄膜構建的PENG實現了機械能向電能的直接轉化,其開路輸出電壓為1.6 V,短路輸出電流為0.14 μA,分別是旋涂法制備薄膜的4.5和2.6倍。PVDF?PENG通過橋式整流器在人的手指敲打60 s后可將1 μF的電容器充電到2 V。在200 MΩ的外加負載下其最大輸出功率為0.03 μW。PVDF?PENG在連續2000次按壓發電后,仍能保持約100%的輸出能力,驗證了其長期穩定的服役能力。最后PVDF?PENG通過采集手指輕敲的能量可點亮LED燈和驅動電子表,證明了實際應用的能力。Abstract: Because of the global fossil energy crisis and environmental pollution problems, the efficient use of green, renewable, and clean energy has become a major trend. Mechanical energy is considered an ideal alternative energy source because of its abundance, accessibility, and non-polluting characteristics. A piezoelectric nanogenerator (PENG) can convert environmental mechanical energy into electrical energy to power electronic devices. However, conventional piezoelectric materials must induce dipole alignment by electrical polarization to obtain piezoelectric properties, which substantially increases the cost and energy consumption of device preparation. Meanwhile, depolarization occurs when the external electric field is removed, which severely affects the performance of the piezoelectric material. In this study, PVDF nanofiber film is prepared using the electrospinning method. The PVDF dipole is rearranged to achieve in situ polarization by a strong electric field and stretching force generated by the electrospinning process. The PVDF nanofiber film process has a high electroactive β-phase content of 78.7%, which is the main contributor to the piezoelectric properties. The PENG constructed based on this film achieves direct conversion of mechanical energy to electrical energy, greatly improving energy use. The open-circuit output voltage of the thin film PENG prepared based on the electrostatic spinning method is 1.6 V, and the short-circuit output current is 0.14 μA, which are 4.5- and 2.6-fold higher than those prepared using the spin-coating method, respectively. The PVDF–PENG can charge a 1-μF capacitor to 2 V through a bridge rectifier after 60 s of human finger tapping. The power density of the PVDF–PENG is analyzed by measuring the electrical parameters at both ends of the resistor. The maximum output power is 0.03 μW at an applied load of 200 MΩ. More electrical energy can be obtained based on the PVDF–PENG, which further illustrates its possibilities and reliability in practical applications. Further, the PVDF–PENG maintains approximately 100% output capacity after 2000 consecutive cycles of compression, verifying its long-term stable service capability. Finally, the energy collected from the mechanical energy of human motion by the PVDF–PENG is explored to drive low-power consumer electronics. Six commercial LEDs are lit by using a large PENG without using any storage device. In addition, a bridge rectifier is used to charge a 2.2-μF capacitor, which successfully lights up a commercial electronic watch.
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Key words:
- PVDF /
- electrospinning /
- spin-coating /
- piezoelectric property /
- in situ polarization
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圖 2 樣品在不同條件下的表面形貌. (a) 前驅體的質量分數為10%;(b) 前驅體的質量分數為12%;(c) 前驅體的質量分數為14%;(d) 前驅體的質量分數為16% (其中10、15、20 kV分別為靜電紡絲時設置的電壓值);(e) 旋涂法制備的PVDF薄膜;(f) 旋涂法制備PVDF薄膜的放大圖
Figure 2. Surface morphology of the samples: (a) the mass fraction of precursor is 10%; (b) the mass fraction of precursor is 12%; (c) the mass fraction of precursor is 14%; (d) the mass fraction of precursor is 16% (voltages of 10 kV, 15 kV, and 20 kV are used for the electrospinning setting); (e) PVDF films prepared using the spin-coating method; (f) enlarged view of PVDF film prepared by spin-coating method
圖 4 PVDF?PENG器件的壓電性能. (a) PVDF?PENG工作原理;(b) 靜電紡絲和旋涂法制備的PVDF薄膜的短路電流;(c) 靜電紡絲和旋涂法制備的PVDF薄膜的開路電壓;(d) 正接和反接時PVDF?PENG的開路電壓;(e) 不同壓力下PVDF?PENG的短路電流
Figure 4. Piezoelectric performance of PVDF?PENG devices: (a) working mechanism of PVDF?PENG; (b) short-circuit current of PVDF films prepared using the electrospinning and spin-coating methods; (c) open-circuit voltage of PVDF films prepared using the electrospinning and spin-coating methods; (d) open-circuit voltage of PVDF?PENG under forward and reverse connections; (e) the current density of PVDF–PENG under different stresses
圖 5 PVDF?PENG 的實際應用探索與穩定性測試. (a) 電容器充電的電路圖;(b) PVDF?PENG為1 μF的電容器充電曲線;(c) PVDF?PENG在不同外負載電阻下的電流;(d) PVDF?PENG在不同外負載電阻下的電流;(e) 在不同外負載電阻下,PVDF?PENG 的電流和電壓變化曲線;(f) 不同外負載電阻下,PVDF?PENG 的功率變化曲線;(g) PVDF?PENG 的穩定性測試
Figure 5. Practical application exploration and stability test of PVDF?PENG: (a) circuit diagram of a capacitor being charged; (b) the charging curve of capacitors with PVDF–PENG; (c) the current of PVDF–PENG under different external load resistances; (d) the voltage of PVDF–PENG under different external load resistances; (e) the current and voltage variation curves of PVDF–PENG under different external load resistances; (f) the power variation curve of PVDF–PENG under different external load resistances; (g) stability testing of PVDF–PENG
圖 6 PVDF?PENG 的實際應用. (a) PVDF?PENG在手指彎曲下的輸出性能; (b) PVDF?PENG在手指叩擊下的輸出性能;(c)點亮6個商用綠色LED燈;(d)點亮一個商業電子表
Figure 6. Practical application of PVDF?PENG: (a) output of PVDF–PENG under finger bending; (b) output of PVDF–PENG under finger tapping; (c) the light up of six commercially available green LEDs; (d) the light up of a commercial electronic watch
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