Energy storage performance of cubic SrTiO3 powder/ polyvinylidene fluoride dielectric composite films
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摘要:
电介质电容器因具备超高的功率密度、超快的充放电速率等优点,成为高能脉冲功率领域的核心储能器件,广泛用于新能源汽车、智能电网等诸多领域。目前电介质电容器的储能密度较低,阻碍了储能器件与系统向小型化与高容量化发展。目前单一的电介质材料已经不能满足脉冲功率型先进电容器的要求。研究学者提出利用复合思想,制备出聚合物和无机陶瓷组成的陶瓷/聚合物复合材料,综合聚合物和陶瓷各自的优点(陶瓷填料的高介电常数和聚合物的高击穿强度),可以获得高储能密度电介质材料。本文采用混合碱法制备出立方体状SrTiO3粉体作为陶瓷填料,采用聚乙烯吡咯烷酮(PVP)表面包覆改性对立方体状SrTiO3粉体进行表面处理,利用流延法制备出了均匀的聚偏氟乙烯(PVDF)电介质复合薄膜。系统研究了表面PVP包覆改性立方体状SrTiO3粉体对PVDF电介质复合薄膜介电性能和储能密度的影响。结果表明:混合碱法制备出的SrTiO3粉体的形貌为立方体状,尺寸为 200-400 nm,粒径分布比较均匀,PVP的官能团和立方体状SrTiO3粉体的表面建立起共价的相互作用,在立方体状SrTiO3粉体表面形成PVP包覆层,可以有效防止立方体状SrTiO3粉体在PVDF电介质复合薄膜中的团聚,同时PVP包覆层可以改善立方体状SrTiO3粉体在PVDF聚合物中分散和结合情况。PVDF电介质复合薄膜具有良好的介电性能和耐击穿性能,PVDF电介质复合薄膜的介电常数随着填充量的增加而增加,当立方体状SrTiO3粉体填充量为40vol.%时,电介质复合薄膜的介电常数为34.9。PVDF电介质复合薄膜的储能密度随着填充量的增加而先增加后降低,当表面PVP包覆改性处理立方体状SrTiO3粉体的填充量为5vol%时,电介质复合薄膜的储能密度达5.3 J/cm3。 SrTiO3粉体填充量为5vol%时,未处理表面改性SrTiO3粉体/PVDF电介质复合薄膜和PVP改性SrTiO3粉体/PVDF电介质复合薄膜的储能密度和放电效率曲线关系图 Abstract: Dielectric energy storage materials with high working field strength and high energy storage efficiency have an important impact on improving the performance of power equipment and reducing the volume of power equipment. The cubic SrTiO3 powder was prepared as ceramic filler by the mixed alkali method, and the surface of the cubic SrTiO3 particles was treated by polyvinylpyrrolidone (PVP) surface modification. The uniform polyvinylidene fluoride (PVDF) flexibility composite was prepared by the casting method. The effect of surface PVP modified cubic SrTiO3 filler on the dielectric properties and energy storage density of PVDF dielectric composites was systematically studied. The results show that the morphology of the SrTiO3 powder is cubic and the size is 200-400 nm. The particle size distribution is relatively uniform. The PVP coating layer formed on the surface of the cubic SrTiO3 filler can effectively prevent the agglomeration of the cubic SrTiO3 filler in the PVDF composites. At the same time, the PVP coating layer can improve the dispersion and bonding of the cubic SrTiO3 filler in the PVDF polymer. PVDF dielectric composite has excellent dielectric properties and breakdown strength. The dielectric constant of PVDF composites increases with the increase of the filling amount. When the filling amount of cubic SrTiO3 filler is 40vol.%, the dielectric constant of the composite is 34.9. And the Maxwell-Garnett model is used to simulate the dielectric constant of the composite. The fitted value is relatively consistent with the measured value. The energy storage density of PVDF dielectric composite increases first and then decreases with the increase of the filling volume. When the filling volume of the cubic SrTiO3 filler modified by the surface PVP is 5vol%, the energy storage density of the composite reaches 5.3 J/cm3. -
图 6 填充量为5 vol.%时,PVDF电介质复合薄膜的SEM图:(a) 未表面改性SrTiO3粉体/PVDF电介质复合薄膜的SEM; (b) 为PVP表面包覆改性SrTiO3粉体/PVDF电介质复合薄膜的SEM图;(c)PVDF电介质复合薄膜的SEM界面图
Figure 6. (a) SEM images of unmodified SrTiO3 powder/PVDF composite films; (b) the SEM images of PVP surface modified SrTiO3 powder /PVDFdielectric composite films at a concentration of 5 vol.%;(c)cross-section SEM of PVP surface modified SrTiO3 powder /PVDFdielectric composite films
图 7 (a)不同填充量PVP表面包覆改性SrTiO3粉体/PVDF电介质复合薄膜与未表面改性SrTiO3粉体;/PVDF电介质复合薄膜的介电常数对比图; (b)为两种PVDF电介质复合薄膜的介电损耗对比图
Figure 7. Comparison of dielectric constants of surface modified SrTiO3 powder/PVDF composite films and unmodified SrTiO3 powder/ PVDF composite films with different filling amounts of fillers, and the comparison of dielectric loss of the PVDF composites films is shown in the inset
表 1 为前期文献报道钛酸锶钡陶瓷/PVDF复合材料的储能密度与本文实验结果对比
Table 1. Comparison of the energy storage density of PVDF-based composites and the experimental results in this paper
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