Precision Silicon Surface Chemistry for Energy Storage Applications

太阳能和风能虽然是加拿大丰富的能源（NRCan统计数据），但其本质上是间歇性的。对于个性化能源应用，如移动电子设备，以及固定微电网和大型电网，储能是绝对必要的。锂离子电池（lib）广泛用于便携式电子应用，我们正在全球范围内看到电网规模（千兆瓦级）电池存储的第一个例子。这些商业lib使用所谓的“传统”石墨阳极，其理论重量容量为372 mAhg-1。另一方面，由于硅的理论重量容量要大一个数量级，约为4200 mag -1，因此引起了人们的极大兴趣。想象一下这样一个世界：电池的寿命是原来的十倍，但重量不变。获得高容量硅基阳极的关键是多方面的，几个关键方面取决于硅表面的界面化学。需要非常高表面积的纳米结构硅（例如，非晶纳米颗粒硅，晶体硅纳米颗粒）才能使锂离子在材料中循环进出，同时伴随着体积的膨胀和收缩而不损坏。大块硅不能适应这些体积变化的应力，导致粉碎和暴露于电解液的新切割和高活性表面；然后，这些界面与电解质原位反应形成对电池性能有深远影响的表面物质。***我们的团队已经在硅表面化学领域工作了20多年，我们将把我们的专业知识应用到纳米结构硅阳极的研究和应用中，以生产模块化的表面涂层，这些涂层被设计成选择性地传输离子，保持电荷传输，并在电化学循环的膨胀和收缩过程中保护硅。这些涂层将在硅集成到阳极之前制备，并在循环过程中通过原位化学反应。为了平衡高容量的硅阳极，在全电池配置中需要一个高容量的伙伴阴极，因为电池的整体性能受到最低容量电极的限制。一个标准的商用金属氧化物阴极只会导致容量比普通石墨阳极小一点的增加。为了克服这一限制，并利用硅阳极，硫系阴极，例如硫和硒，将在一个完整的电池配置中使用。再一次，对硅表面化学的控制是至关重要的，因此功能化将是开发高可逆、长寿命高容量硅电池的关键。最终目标是发展硅表面化学，从而生产出用于大规模电池应用的高容量、稳定的硅电极。**

Solar and wind energy, while abundant sources of energy in Canada (NRCan statistics), are by their very nature intermittent. For personalized energy applications such as mobile electronics, as well as stationary microgrid- and large grid-scale considerations, energy storage is absolutely necessary. Lithium ion batteries (LIBs) are widespread for portable electronics applications, and we are seeing the first examples of grid-scale (gigawatt scale) battery storage, worldwide. These commercial LIBs use what are called 'conventional' graphite anodes that have a theoretical gravimetric capacity of 372 mAhg-1. Silicon, on the other hand, is of great interest due to its theoretical gravimetric capacity that is an order of magnitude larger, ~4200 mAhg-1. Imagine for a moment a world where batteries last ten times longer, and yet are the same weight. The keys to accessing high capacity silicon-based anodes are multifold, and several critical aspects depend exquisitely upon the interfacial chemistry of the silicon surface. Very high surface area nanostructured silicon (e.g. amorphous nanoparticulate silicon, crystalline silicon nanoparticles) is needed to enable the lithium ions to cycle in and out of the material with accompanying volume expansion and contraction without damage. Bulk silicon cannot accommodate the stress of these volume changes, leading to pulverization and exposure of freshly cleaved and highly reactive surfaces to the electrolyte; these interfaces then react in-situ with the electrolyte to form surface species that have profound effects on battery performance. *** Our group has been working on silicon surface chemistry for over two decades, and we will apply our expertise to the study and application of nanostructured silicon anodes, to produce surface coatings that are modular, and are designed to transport ions selectively, maintain charge transport, and protect the silicon during expansion and contraction of electrochemical cycling. These coatings will be prepared before the silicon is integrated within the anode, and via in-situ chemical reactivity during cycling. To balance the high capacity silicon anode, a high capacity partner cathode is needed in a full cell configuration, since the overall battery performance is restricted by the electrode with the lowest capacity. A standard commercial metal oxide cathode would only result in a small increase in capacity over a regular graphite anode. To overcome this limitation, and take advantage of the silicon anode, chalcogenide cathodes, for instance sulfur and selenium, will be used in a full cell configuration. Again, control over the silicon surface chemistry is critical, and thus functionalization will be the key to the development of highly reversible, long-lived high capacity silicon batteries. The final goal is the development of silicon surface chemistry that leads to the production of high capacity, stable silicon electrodes for large-scale batter applications. **