二次包覆法制备煤沥青基硅/碳复合物及其锂离子电池性能

本文采用市售纳米硅为硅源,以软化点低、得碳率高、价格便宜的煤沥青作为碳源,通过两步包覆法制备了煤沥青基硅/碳(Si/C/C)复合物,并研究其作为锂离子电池负极材料的电化学性能。 结果表明,所得复合物的粒径在300~350 nm间,Si纳米粒子被C包覆并相互连结成C-Si-C网络结构,其中Si含量为27%的硅/碳复合物(Si/C/C-27%)作为锂电池电极材料表现了良好的储锂性能。 在0.1 A/g的小电流密度下,Si/C/C-27%的放电比容量为1281 mA·h/g;在3 A/g的大电流密度下,其放电比容量仍能保持在582 mA·h/g,表现了良好的倍率性能。Si/C/C-27%在2 A/g的电流密度下经过100次的循环后其比容量保持率为76.61%,表现了良好的循环稳定性。 相比于煤沥青基碳的一次包覆所得的硅/碳复合材料(Si/C),Si/C/C有效提高了Si纳米粒子的导电性并抑制了其在嵌锂和脱锂过程中的体积膨胀。 本文提出的二次包覆的新方法为制备具有优异电化学性能的锂离子电池负极材料提供了新的研究思路。

Two-Step Coating Synthesis of Silicon/Carbon Composite Based on Coal Tar Pitch and Its Lithium Battery Performance

Silicon/carbon (Si/C/C) composites based on the coal pitch was successfully prepared by a two-step method. Commercially available nano-silicon and coal pitch with low softening point, high carbon ratio and low price were used as the silicon and carbon sources, respectively. The electrochemical properties of the as-obtained composites as the negative electrode of the lithium ion batteries were systematically investigated. The results show that the obtained composite has a particle size in the range of 300 to 350 nm. The Si nanoparticles coated with C are bonded to each other to form a C-Si-C network structure, in which the silicon(27% mass fraction)/carbon composite (Si/C/C-27%) exhibits good lithium storage performance as a lithium battery electrode material. In addition, the Si/C/C-27% composite has a specific discharge capacity of 1281 mA·h/g at a current density of 0.1 A/g; at a current density of 3 A/g, the composite has a specific discharge capacity of 582 mA·h/g, showing good rate performance. The cycle efficiency retention of the product is 76.61% after 100 cycling times at the current density of 2 A/g , which also demonstrates its high stability. Compared with the one-step carbon-coated silicon(Si/C) material, Si/C/C material not only effectively improves the conductivity but inhibits the volume expansion of Si particles during lithiation and de-lithiation. This new proposed method provides a new research idea for preparing lithium ion battery anode materials with excellent electrochemical performance.