Conversion of the energy landscape from fossil fuels to renewables strongly depends on the availability of cheap and reliable energy storage solutions. At present, rechargeable batteries is the most appealing option. Among those, Li-ion batteries (LIBs) represent the most developed technology, which delivers not only the highest energy density, but also demonstrates long-term durability and high capacity. Such properties positioned LIB technology as a primary solution for portable electronics, electric vehicles and in-house stationary energy storage. Besides the current dominant position of LIBs, such technology at its present stage has almost reached its ceiling, while the modern world’s activities require wider deployment of energy storage solutions. Therefore, new improvements and innovations are necessary to satisfy the rapidly growing demands of the energy storage market.
Several approaches are represented in the scientific literature and are directed towards improvement of energy density of LIBs while maintaining long-term performance. Among these solutions, the replacement of the battery anode was found to be potentially the simplest and the most economical pathway for the technology improvement without major investments into infrastructure. Silicon (Si) was found to be a material of choice for LIB anodes due to its abundancy, low price, stability and wide deployment in the semiconductor industry.
Si has demonstrated a remarkable storage capacity for the Li ions, which could improve the anode capacity by almost an order of magnitude. However, substantial structural changes during operation results in fast degradation of the batteries fabricated with Si. Therefore, the primary aim of this project is to develop a screening platform for the new Si-based materials with improved stability. The main product of this work will be an extensive library of tested materials which will allow future investigations of new and industry relevant battery materials.
In addition to the further analysis of the silicon-nitride system of anode materials, which was pioneered at IFE, the silicon-carbon system has received the most attention till now in the project. In this work, refining reliable procedures for deposition and characterization of thin films of these materials have been of paramount importance. In parallel, we have developed methods for production of nanoparticulate materials with equivalent characteristics, in order to evaluate the transferability of thin film results to more application relevant particle based composite electrodes. Preliminary results of this work have been presented at the International Meeting on Lithium Batteries in Sydney, Australia, the leading forum for research on lithium-based batteries. Additionally, preliminary experiments within the silicon-phosphorous system have been begun.
Development of high-performance energy storage technologies is recognized as the key element needed for transition to environmentally friendly future. Currently, Li-ion batteries are considered to be the most promising while mature technology for implementation. While there has been a significant progress in improvement of most of the components in the battery, anodes remained unchanged. Large effort was devoted to develop silicon as a next generation anode material, due to its extremely high lithium storage capacity. However, silicon has challenges with stability, currently preventing the material from maintaining this high capacity during battery cycling. Recently there has been an emergence of convertible alloy anode materials. Those undergo a phase separation during initial lithiation resulting in stable silicon nanoparticles embedded in a matrix. Despite a clear scientific and commercial potential associated with the development of the such materials, the knowledge base for those is far away from being comprehensive.
In this project, we propose to develop a streamlined screening and optimization procedure for new silicon-based anode materials using nanostructured thin films. Such electrodes can be prepared with a large range of compositions and element combinations using effective and reproducible thin film deposition methods, such as PECVD. These will provide the basis for a comprehensive and comparable electrochemical testing to determine the key performance characteristics for each system and their dependence on the material composition. A combination of electrochemical testing with advanced characterization will be used to determine lithiation mechanisms allowing classification of materials and extending the prediction of performance characteristics. The main product of this work will be an extensive library of comparable test data, the availability of which would allow targeted investigations of promising and industry relevant battery materials.