Synthesis of nanosized Si composite anode material for Li-ion batteries

A simple method was proposed to prepare nanosized Si composite anode materials for lithium-ion (Li-ion) batteries. The preparation started with the shock-type ball milling of silicon in liquid media of polyacrylonitrile (PAN)/dimethylformamide (DMF) solution, forming slurry where the nano-Si particles were uniformly dispersed, followed by the drying of the slurry to remove DMF. The nanosized Si composite anode material was obtained after the pyrolysis of the mixture at 300 °C where the pyrolyzed PAN provided a conductive matrix to relieve the morphological change of Si during cycling. As-prepared composite presented good cyclability for lithium storage. The proposed process paves an effective way to prepare high performance Si, Sn, Sb and their alloys based composite anode materials for Li-ion batteries.     

Design and fabrication of a TiO2/nano-silicon composite visible light photocatalyst

Nano-silicon (nc-Si) was utilized as the charges generator to promote the photocatalytic and super-hydrophilic reactivity of TiO₂ film under visible light irradiation. The photocatalytic ability of TiO₂/nc-Si composite photocatalyst was evaluated by a set of experiments to photodecompose 100 ppm methylene blue (MB) in aqueous solution. And the super-hydrophilic property was characterized by measuring the water droplet contacts angle, under visible light irradiation in atmospheric air and at room temperature. Under 100 mW/cm² visible light irradiation, the droplet contact angles were reduced to 0° within 4 h with nc-Si charge generator. Additionally, the rate constant of MB photo-degradation was promoted 6.6 times.     

Rational design of robust nano-Si/graphite nanocomposites anodes with strong interfacial adhesion for high-performance lithium-ion batteries

The nano-Si/graphite nanocomposites are the promising anodes candidates for high-energy lithium-ion batteries because of their high theoretical capacities and low volume variations.However,the nano-Si has a severe tendency to separate from the graphite substrate due to the inherently weak bonding between them,thus leading to the deteriorated cycling performance and low Coulombic efficiency.Herein,we design a robust nano-Si/graphite nanocomposite structure with strong interfacial adhesion caused by the Si—Ti and Ti—C covalent bonds.The abundant Si—Ti and Ti—C bonds formed between nano-Si and graphite greatly enhance the interfacial adhesion force,resulting in the highly stabilized and integrated electrode structure during battery cycling.Consequently,the as-obtained nano-Si/graphite anodes deliver a high capacity retention of 90.0% after 420 cycles at 0.5 C with an average Coulombic efficiency of 99.5%;moreover,a high initial Coulombic efficiency of 90.2% is achieved.Significantly,this work provides a novel strategy to address the poor interfacial adhesion between nano-Si and graphite,which can be applied to other nano-Si based composites anodes.     

亲水纳米二氧化硅修饰丝网印刷碳糊电极的改进性能研究

研究了以铁氰化钾为电子传递剂,亲水纳米二氧化硅为固定化酶的载体与高分子成膜材料掺杂制作的生物敏感膜修饰丝网印刷碳糊电极葡萄糖生物传感器的改进特性,并从机理上分析了形成这种优化的原因。实验采用柠檬酸作为缓冲液,在高分子成膜材料、铁氰化钾、稳定剂、葡萄糖氧化酶中掺杂均相处理后的纳米二氧化硅制备生物敏感膜,并制成腔体,将其与未经过纳米二氧化硅掺杂制备的生物传感器进行对比实验。实验证明:用掺杂纳米二氧化硅制作的生物敏感膜修饰的丝网印刷碳糊电极与未修饰电极相比,灵敏度提高了2.6倍,线性检测范围为1.1~33.3 mmol/L,对测试范围内不同浓度的葡萄糖样本,相对标准偏差<5%,重现性和稳定性良好,具有较高的研究价值和应用前景。     

聚酰胺改性纳米二氧化硅的作用机理

探讨了≡Si⁺离子(客体) 同以NH₂为末端的聚酰胺胺(PAMAM)大分子(主体)在液相条件下的作用机制,利用密度泛函理论研究了主客体所形成的复合物的结构和能量性质,并考察了溶剂对结构和能量的影响. 通过对复合物的几种可能构型进行优化分析,得出两种构型最稳定,类型A(≡Si⁺键合在酰胺活性点)和类型C(≡Si⁺键合在亚胺活性点). 类型A和C之所以最稳定是因为它们各自形成了Si-No和Si-O化学键. 通过对最稳定构型红外计算分析发现理论值和实验值比较相符.     

Interaction Mechanism of Nano-silicon Dioxide Modified by Poly(amidoamine) Dendrimers

To gain insight into the attachment of ≡Si⁺ (SC) ion (regarded as guest) to the lowest generation, NH₂-terminated poly(amidoamine) (PAMAM) dendrimers (regarded as host) in the liquid phase, density functional theory is used to investigate the structures and energetics of the host-guest complex. The effect of solvent on the structures and energetics is also investigated. Various initial configurations of the ion bound to PAMAM are tested, and two stable conformers are found, i.e, types A (≡Si⁺ is bound to the amine site) and C (≡Si⁺ is bound to the amide site). Types A and C are the most stable due to the chemical bond formations of Si-No(amine nitrogen atoms) and Si-O, respectively. The IR spectra for the lowest energy conformers are thoroughly analyzed and compared with the available experimental data.