用于锂离子电池负极的多孔硅材料制备

Preparation of Porous Silicon Materials as Anode for Lithium Ion Batteries

多孔硅具有大量孔洞,能有效缓解体积膨胀带来的压力,有望成为锂离子硅基负极材料的一个研究方向.采用光助电化学腐蚀、二次化学腐蚀制备高孔隙率n型多孔硅材料,通过优化后的光助电化学腐蚀,样品的孔径约为800～1 000nm,多孔层厚度(平均孔深)约为155μm,孔隙率约74%.二次腐蚀后,样品孔径增加到1.1μm,多孔层厚度减小到110μm,孔隙率增加到84%,表明二次腐蚀增加了样品的孔径和孔隙率.以二次腐蚀的多孔硅材料为负极的锂离子半电池在0.05C的恒流充放电循环测试下,循环20次后充放电比容量保持在188和198mAh/g,效率保持90%以上.实验结果表明,多孔硅锂电极比单晶硅锂电极具有更长的循环寿命,可有效提高锂电池的性能.

Porous silicon can incorporate large amounts of Li and relieve the stress during lithiation with large superficial area and high porosity. N-porous silicon was produced by photoelectrochemical etching and chemical over-etching. The SEM images shows：the porous silicon materials produced by photoelectrochemical etching have 155 gm-long and 1μm-wide macropores. After chemical over- etching carried out in porous silicon, the materials had 220 nm-wide walls and pores with diameter of 1.1μm,respectively. The thick- ness of porous layer is 110μm. Chemical over-etching enlarged diameters of holes,which increased poriness of the materials. At a rate of 0.05 C, the charged/discharge capacity of the cell with porous silicon materials as anode was 1 191,2 036 mAh/g in the first and dropped to 188,198 mAh/g after 20 cycles with the efficiency above 90;. The result shows that the porous silicon materials has lon- ger cycle life than single-crystal silicon,which can improve lithium;s profermance.