硅酸盐学报

多孔硅基负极材料因其在硅脱嵌锂过程中能缓解体积膨胀的优势，在电池技术中展现出巨大的应用潜力。但在长期循环使用时，电极在脱嵌锂过程中不可避免的出现容量下降和结构被破坏等问题。随着研究的深入和技术的进步，保证多孔型电极在循环过程不发生开裂，并具有更高的比容量和倍率性能，成为了多孔型硅基负极材料的新突破口。本实验分别以葡萄糖和蔗糖为碳的前驱体进行分阶段碳化，使用预氧化的聚乙烯吡咯烷酮(PVP)作为骨架，运用微电子打印技术构建了新型Si@PVP/葡萄糖和Si@PVP/蔗糖多孔碳骨架结构的Si@C复合电极。分析结果表明：Si@PVP/葡萄糖结构电极循环后电极表面开裂明显更小。以0.1 A·g^–1的电流密度放电，Si@PVP/葡萄糖结构电极首圈比容量为1655 m A·h·g^–1,100圈后比容量为1095 m A·h·g^–1，可逆容量保持为97.4%;Si@PVP/蔗糖结构电极首圈比容量为1455 m A·h·g^–1,100圈后比容量为970 m A·h·g^–1，可逆容量保持为91%。

Introduction Porous silicon-based anode materials with their high theoretical specific capacity (i.e.,approximately 4200 mA·h·g^-1)and unique porous structure have a promising application potential in the field of lithium-ion batteries.Their porous structure provides effective buffering space for the significant volume change (i.e.,300%) of silicon during charging and discharging,effectively mitigating material pulverization and maintaining the integrity of the electrode structure,thereby enhancing battery cycle stability and Coulombic efficiency,and greatly increases the utilization rate and conductivity of active materials,thus enhancing the energy density of lithium-ion batteries.However,despite the enormous application prospects of porous silicon-based anode materials,their high preparation costs,low initial Coulombic efficiency,and capacity fade after long-term cycling remain some critical factors restricting their commercialization.To address these issues,recent studies mainly focus on nanostructure design,composite material development,electrolyte optimization,and large-scale preparation techniques.The emergence of silicon-carbon composite materials,which embed silicon nanoparticles into a porous carbon matrix,can construct a good conductive network,effectively improving material conductivity,and further enhance the buffering capacity for silicon volume changes,significantly improving battery cycle stability and rate performance.In this paper,a porous silicon-carbon layered silicon-based composite was prepared as an anode material.In addition,the electrochemical performance of this material was also investigated.Method In the preparation process,silicon nanopowder was first uniformly dispersed with a mixed solvent of deionized water and anhydrous ethanol,and then sonicated under ultrasound to ensure uniform dispersion of silicon nanopowder.Subsequently,PVP(polyvinylpyrrolidone) and glucose/sucrose were added to the dispersed suspension as a pore-forming agent and two carbon sources,and stirred at room temperature to form a uniform precursor sol.The two precursor sols,i.e.,Si/PVP/glucose and Si/PVP/sucrose,were placed into the ink cartridges of a microelectronic printer,and the gels were uniformly printed onto copper foil by a 3D printing technology.Finally,the carbon-containing substances in the electrode were completely reduced to amorphous carbon after vacuum drying and carbonization treatment.Note that different carbon sources (i.e.,glucose and sucrose) released different amounts of gas during the carbonization process,leading to subtle changes in the electrode structure and subsequently affecting its electrochemical performance.The prepared electrode materials were analyzed by scanning electron microscopy (SEM),transmission electron microscopy(TEM) and other characterization techniques.Results and discussion The results show that larger pores with a uniform pore distribution exist in Si@PVP/glucose structure,and the electrode exhibits minimal cracking after charging and discharging cycles,demonstrating the superior mechanical stability and resistance to expansive internal stresses.In contrast,the pore distribution of Si@PVP/sucrose is relatively uneven,and the electrode exhibits greater cracking after cycling,leading to a decrease in cycle stability and electrochemical performance.These results demonstrate that the Si@PVP/glucose structure electrode exhibits a greater ability to withstand expansive internal stresses and has a higher cycle retention rate.The electrochemical performance tests further validate the superiority of the Si@PVP/glucose composite material.After 100 cycles of charging and discharging,the specific capacity of the Si@PVP/glucose electrode reaches 1095 mA·h·g^-1,with a reversible capacity retention rate of 97.4%,while the specific capacity of the Si@PVP/sucrose electrode is only 970 mA·h·g^-1,with a reversible capacity retention rate of 91.0%.It is indicated that the Si@PVP/glucose composite material has significant advantages in optimizing the performance of porous silicon-based anode materials,particularly in improving cycle stability and rate performance.Conclusions This study prepared a porous silicon-carbon layered silicon-based composite (i.e.,Si@PVP/glucose) as an anode material,and the performance was optimized.The results showed that the Si@PVP/glucose electrode material exhibited a greater ability to withstand expansive internal stresses and had a higher cycle retention rate.The electrochemical performance tests further validated the superiority of the Si@PVP/glucose material.It is indicated that this porous silicon-based anode material could have a promising application potential in the field of energy storage and conversion for high-energy-density and long-life batteries.