Research On Self-charging Power Cell Based On Piezo-Electrochemical Composite Energy Conversion And Storage

The fabrication of self-charging power cell（SCPC）provides an innovative method of self-charging,in which the mechanical energy is directly converted and simultaneously stored as chemical energy,so as to supply continuous power from the environment without an external power source.PVDF based piezo-separator is the key component in SCPC on realizing its self-charging function.It is found that an excellent piezo-separator required both good porous structure and high piezopotential.In this case,more pores in the nanocomposite film would increase the ionic conduction paths,leading to the enhanced transport of Li ions.Thus,a good storage capacity could also be obtained.Meanwhile,the high piezopotential could result in more Li ions to migrate from cathode to anode,leading to good energy conversion/storage efficiency.In order to improve the performance of the SCPC and promote its practical application,this paper focuses on the modification of the PVDF based piezo-separator from the above two aspects.The specific contents are as follows:（1）ZnO particles was introduced to act as nucleating agents to induce the formation of the piezoelectricβ-form and impart good solubility in acidic solution,which makes the PVDF piezo-separator have better pore structure,thereby increasing the Li⁺diffusion channel and promoting the continuous and rapid transmission.Meanwhile,to overcome the problems of serious mechanical energy loss and low flexibility in the structure of coin steel shell,a new type of SCPC with flexible structure was packaged by PET film,in order to improve the mechanical energy utilization of the battery.（2）A new type of lead-free piezoelectric fiber Ba_0.7Ca_0.3TiO₃-Ba(Ti_0.8Zr_0.2)O₃（BCT-BZT）has been prepared by electrospinning,served as an enhanced piezoelectric phase of nanocomposite films.Through the intensive study of the preparation process,the optimum length and diameter range of BCT-BZT fibers and the concrete composite method with PVDF matrix have been determined.The piezopotential of PVDF/BCT-BZT nanocomposite film was greatly improved.The output voltage of nanocomposite film with 30 wt.%BZT-BCT reached around 8.0V under the potential energy of 588mJ on average,which was more than two times as much as the pure PVDF.（3）The influence of different content of BCT-BZT nanofibers on the properties of SCPC is systematically investigated.The presence of appropriate content of lead-free piezoelectric fibers BCT-BZT would not only intensify the piezoelectric potential but also provide a porous structure in the nanocomposite film,the creation of the pores can be attributed to the contraction of PVDF during the solidification process and the stacking between BCT-BZT short fibers,which can result in a smaller interpore distance,rapid pathways for ionic/electronic transport,lower the contact resistance and keep the overall electrode highly conductive and active in lithium storage.Moreover,exploring the practical application of the SCPC,we believe that such a development of the SCPC with environmental friendliness,facile synthesis,high potential and high stability could have broad application prospects.