Silicon based hybrid materials for lithium-ion batteries: Synthesis, processing and characterization
Hartmut Wiggers, CENIDE and University of Duisburg-Essen, Duisburg, GermanyHans Orthner, Institute for Combustion and Gas Dynamics - Reactive Fluids, University of Duisburg-Essen , Duisburg, GermanyStefan Kuns, Institute for Combustion and Gas Dynamics - Reactive Fluids, University of Duisburg-Essen , Duisburg, GermanyLisong Xiao, Institute for Combustion and Gas Dynamics - Reactive Fluids, University of Duisburg-Essen , Duisburg, Germany
Rechargeable batteries based on lithium-ion technology are state-of-the-art for mobile electronic devices as well as electromobility and their massive utilization will continue for many more years. Therefore, it is expected that in the near future research and process technology towards batteries with higher power and capacity will be mostly based on an evolutionary development of the existing technology. It will address optimization and/or slight modification of already existing materials for anode and cathode. Concerning the anode side, experts agree that a partial and increasing replacement of graphite by silicon will take place as silicon – compared to the actually used graphite – is able to store ten times more lithium, thus enabling higher storage capacity of the entire battery. However, silicon lacks from some drawbacks that have to be overcome. Its tremendously high storage capacity is accompanied by extreme changes in volume during charge and discharge, thus leading to high mechanical stress. Moreover, the electrical connection of the active components also suffers from the dynamic processes. The paper will consider solutions that can face both, mechanical stress as well as electrical contact. A size reduction of the individual silicon particles below about 200 nm has been shown to solve the problem of mechanical disintegration. We have been able to synthesize silicon nanoparticles that meet this requirement utilizing a bottom-up approach based on the gas-phase synthesis of silicon. In addition, we are able to specifically produce either crystalline or amorphous nanoparticles while the latter show an excellent performance in lithium-ion batteries. Disintegration of the electrical contact could be overcome by synthesizing composite materials consisting of silicon and carbonaceous species, especially carbon nanotubes and graphene. The contribution will discuss the advantages and disadvantages of the different synthesis routes. Highly promising composite materials with initial Coulomb efficiencies of more than 85% and long-term stabilities over 500 charge/discharge cycles have been produced, thus meeting more than the requirements of consumer applications.