A novel manufacturing approach to graphene-encapsulated sulfur and silicon nanoparticles for battery applications via freeze-drying micro-emulsion

通过冷冻干燥微乳液制造用于电池应用的石墨烯封装硫和硅纳米颗粒的新颖方法

• 批准号: 389154849
• 负责人: Dr. Chuyen Van Pham, Ph.D.
• 金额: --
• 依托单位: Helmholtz-Institut Erlangen-Nürnberg für Erneuerbare Energien (HI ERN)
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2017
• 资助国家: 德国
• 起止时间: 2016-12-31 至 2021-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/389154849?language=en
• 关键词: novel; manufacturing; approach; graphene; encapsulated

Sulfur and silicon have recently been considered as the most promising alternative cathodic and anodic materials, respectively for the next generation of Li-batteries. However, currently required performances of the known S/Si based Li cells are not sufficient. For S-based cells: this is due to: (i) the loss of sulfur during cycling due to the solubility of sulfur intermediate in the electrolytes; (ii) the 76% volume expansion/contraction which leads to disintegration of the electrodes; (iii) the low electrical conductivity (10^(-30) S/cm) of S. For the Si: Si anodes face material intrinsic challenges such as the large volume expansion (400%) and the chemical reaction of Si with electrolyte, leading to material pulverization and surface passivation, respectively. This project introduces a novel manufacturing approach to encapsulate both S and Si-nanoparticles (NPs) in reduced graphene oxide (rGO) nanostructures for Li battery applications via three steps: (i) fabrication of a micro-emulsion of S/Si dissolved in organic solvents as dispersed phase (S/Si-micelles) and GO aqueous solution as continuous phase (S/Si@GO micro-emulsion); (ii) freeze-drying of the S/Si@GO micro-emulsion; (iii) reduction of GO to rGO. During the micro-emulsion formation (step i), by using a cationic surfactant, the surface of S/Si-micelles becomes positive. Therefore, negatively charged GO flakes will attach to the positively charged surface of the spherical micelles, forming spherical GO-shells wrapping S/Si-micelles in a self-assembly manner. The freeze-drying (step ii) will evaporate both organic solvents in the micelles forming S/Si-NPs attached inside on GO-shells and frozen water in the continuous phase to create GO-nanoscaffolds. As a result, S/Si-NPs encapsulated in GO-shells integrated within GO-nanoscaffolds (S/Si@GO) are obtained. In step (iii), GO will be reduced to rGO to form S/Si@rGO. The reduction degree that determines the conductivity of rGO is controllable by reaction temperature and time.Scientific target is to demonstrate: (i) the formation of novel micro-emulsions comprising of S or Si-containing micelles encapsulated in GO-shells; (ii) the formation of GO-shells, on the basis of the static electrical attraction of negatively charged GO nanoflakes on positively charged surface of the micelles is obtained by using cationic surfactants.Technological significance: This project aims on achieving size control from molecular scale to nanoscale for efficiently encapsulating S/Si NPs in rGO shells, integrated within rGO-nanoscalfolds (S/Si@rGO). The S-loading and the rGO-nanostructured pores is controlled for an efficient sulfur utilization and confinement when used as cathodes in lithium/sulfur (Li-S) batteries (LSBs) . The final target is to overcome the challenges in LSB Technology. Also, this novel approach targets to achieve highly conformal rGO-encapsulated Si-NPs as anodic materials for Li-ion batteries.

硫和硅最近被认为是最有前途的替代阴极和阳极材料，分别用于下一代锂电池。然而，已知的S/Si基Li电池目前所需的性能是不够的。对于基于S的细胞：这是由于：（i）由于硫中间体在电解质中的溶解度，在循环过程中硫的损失;（ii）76%的体积膨胀/收缩，这导致电极的分解;（iii）S的低电导率（10^（-30）S/cm）。对于Si：硅阳极面临材料固有的挑战，如大体积膨胀（400%）和硅与电解质的化学反应，分别导致材料粉碎和表面钝化。该项目介绍了一种新的制造方法，通过三个步骤将S和Si纳米颗粒（NPs）封装在用于锂电池应用的还原氧化石墨烯（rGO）纳米结构中：（i）制造溶解在有机溶剂中的S/Si微乳液作为分散相（ii）将S/Si @ GO微乳液冷冻干燥;（iii）将GO还原成rGO。在微乳液形成（步骤i）期间，通过使用阳离子表面活性剂，S/Si-胶束的表面变为正性。因此，带负电荷的GO薄片将附着到球形胶束的带正电荷的表面，以自组装方式形成包裹S/Si胶束的球形GO壳。冷冻干燥（步骤ii）将蒸发胶束中的有机溶剂和连续相中的冷冻水，以形成附着在GO-壳上的S/Si-NP，从而产生GO-纳米支架。结果，获得了封装在集成在GO-纳米支架内的GO-壳中的S/Si-NP（S/Si@GO）。在步骤（iii）中，GO将被还原成rGO以形成S/Si@rGO。通过反应温度和反应时间可以控制还原程度，从而决定rGO的导电性。科学目标是证明：（i）形成由GO壳中包裹的含S或Si胶束组成的新型微乳液;（ii）GO壳的形成，基于带负电荷的GO纳米片在胶束的带正电荷的表面上的静电吸引，通过使用技术意义：该项目旨在实现从分子尺度到纳米尺度的尺寸控制，以有效地将S/Si NP包封在rGO壳中，整合在rGO纳米折叠（S/Si@rGO）内。当用作锂/硫（Li-S）电池（LSB）中的阴极时，控制S负载和rGO纳米结构孔以实现有效的硫利用和限制。最终目标是克服LSB技术的挑战。此外，这种新方法的目标是实现高度共形的rGO封装的Si-NP作为锂离子电池的阳极材料。