外部载荷对硅电极锂电池循环性能的影响

Influence of external loads on the cycling performance of silicon anode lithium-ion batteries

硅具有高比容量和低电压平台等优点,被认为是最有前途的锂离子电池负极材料之一。然而,硅电极在锂化/脱锂过程中巨大的体积膨胀以及伴随的材料破裂和粉化,限制了其倍率性能和循环性能。现有研究表明,在循环过程中对硅电极施加外部载荷能有效提高电池的循环性能。本研究提出了一种宏观调控方法,即通过施加外部机械载荷以提高硅电极锂离子电池的容量保持率。采用设计定制的原位充放电加压实验设备,以CR2032纽扣电池为对象开展实验,通过充放电循环测试验证了该方法的有效性。实验结果显示,在CR2032电池表面施加0.2 MPa大小的轴向外部载荷,可以有效抑制硅电极在充放电过程中的膨胀,并调节电池内部状态。经过50个充放电循环后,电池容量保持率将从无外部载荷时的59%提升至70%。同时,由于硅电极活性物质颗粒在锂化和脱锂过程中存在不同的应力状态,提出了一种新的调控方法,即在循环过程中在电极材料的锂化阶段施加0.1 MPa大小的外部载荷,并在脱锂阶段施加0.2 MPa的载荷。实验结果证明,该方法可以进一步提高硅电极锂离子电池的循环性能。此外,电极表面的扫描电子显微镜成像结果也支持了这一结论。本研究采用的外部机械载荷施加方法,为从宏观角度提高硅负极锂离子电池性能提供重要的借鉴。

Silicon,which has high specific capacity and low voltage characteristics,is considered one of the most promising anode materials for lithium-ion batteries.However,the significant volume expansion of silicon electrodes during lithiation/delithiation processes,along with the associated material fracturing and pulverization processes,limits its rate performance and cycling stability.Existing studies have demonstrated that applying external loads to silicon electrodes during cycling can effectively enhance the cycling performance of silicon-based batteries.This study proposes a macroscopic control method by applying external mechanical loads to enhance the capacity retention of silicon-electrode lithium-ion batteries.We employed a custom-designed,in situ loading device connected with a battery cycling tester and CR2032 button cells as the experimental objects,and the effectiveness of this method was evaluated using cycling tests.The experimental results demonstrate that applying a 0.2 MPa axial external load on the surface of the CR2032 cells effectively suppress the expansion of the silicon electrodes during the charge-discharge processes and regulates the internal state of the battery.After 50 charge-discharge cycles,the capacity retention rate increases from 59%without external loads to 70%.Additionally,considering the different stress states of the silicon electrode active material particles during the lithiation and delithiation processes,we propose a novel control method by applying a 0.1 MPa external load during the lithiation stage and a 0.2 MPa load during the delithiation stage in the cycling process.The experimental results demonstrate that this method can further improve the cycling performance of silicon-based lithium-ion batteries.Moreover,the scanning electron microscopy imaging results of the electrode surface also support this conclusion.The method of applying external mechanical loads used in this study provides important insights for improving the performance of silicon-based electrodes in lithium-ion batteries from a macroscopic perspective.