硅碳合金(Si/C)因其超高的比容量和合适的工作电压,更容易满足未来新能源汽车和储能设备对于电池高能量密度的要求.但其实际应用却受制于导电性差、反应动力学缓慢和体积效应明显(最高可达300％)等缺点.本文巧妙地利用硅负极在充放电循环中的"体积膨胀"特性构建了一种"序构"材料.通过在Si/C复合材料表面引入"主动参与、主动作为"的功能化压电修饰层钛酸铋钠(Bi0.5Na0.5TiO3,BNT),利用合金化反应产生的机械应力诱导压电材料产生局域电场,实现机械能转化为电能,来获得一定的功能性,更加有效地促进界面锂离子输运能力,同时缓解合金化反应引起的体积膨胀,从而维持良好的界面接触.协同效果驱动下的Si/C@CNTs@BNT复合电极材料在0.2Ag-1电流密度下,循环200圈之后,依然可以保持911.2 mAh g-1的可逆比容量,容量保持率为90.74％.
Abstract
Construction of ordered structures that respond rapidly to environmental stimuli has fascinating possibilities for utilization in energy storage.Silicon/carbon(Si/C)anodes with extremely high energy densities have sparked widespread interest for lithium-ion batteries(LIBs),while their implementation is constrained via mechanical structure deterioration,continued growth of the solid electrolyte interface(SEI),and cycling instability.In this study,a piezoelectric Bi0.5Na0.5TiO3(BNT)layer is facilely deposited onto Si/C@CNTs anodes to drive piezoelectric fields upon large volume expansion of Si/C@CNTs electrode materials,resulting in the modulation of interfacial Li+kinetics during cycling and providing an electrochemical reaction with a mechanically robust and chemically stable substrate.When evaluating as an anode,the Si/C@CNTs@BNT anode displays exceptional cycling performance(911.2 mAh g-1 at 0.2 A g-1 for 200 cycles with a retention of 90.74％).
维普
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