Tin in Energy Technologies
Tin in Energy Technologies
Global demand for novel energy-related technologies is set to expand markedly in the years ahead. The unique properties of tin have led to a number of interesting opportunities in energy development, storage and efficient usage. Although the quantities of tin currently involved are small, potential future markets are very large and, as a portfolio, energy-related technology represents a field that clearly justifies close monitoring.
Lithium ion batteries
The global market for lithium ion batteries (LIBs) is expected to grow dramatically over the next decade, particularly if they can be successfully implemented in electric vehicles. Opportunities for tin have arisen primarily in the anode material, where tin-based composite systems are found to exhibit significantly higher capacities than conventional graphite anodes. Leading LIB manufacturers, including Sony, 3M and Mitsubishi are all now utilising tin-based anodes in their commercial batteries and a new tin usage of around 17,000 tonnes per annum is not unreasonable in the next 5 years.
Current research indicates that tin may also find use in the cathode material (where tin can be introduced into conventional phases such as lithium – cobalt oxide or lithium – manganese oxide) and in the electrolyte itself (where tin may feature in lithium ion composite electrolyte systems), although research in these areas is still at an early stage and additional tin consumption is unlikely to materialise in the short term.
Solar cell technology (often referred to as 'photovoltaics') is advancing rapidly and is recognised as being the leading alternative energy source. Conventional bulk silicon modules are being superseded by thin film photovoltaic assemblies and this new technology is expected to dominate the solar cell market in the years ahead. Opportunities for tin usage are in transparent conducting oxide top layers (used extensively in current thin film cells) and as potential replacement materials for cadmium telluride (CdTe) and copper – indium – gallium – selenide (CIGS) in the light absorbing layer itself.
Although current tin usage in solar cells is limited to a few tonnes per annum, primarily in indium – tin oxide (ITO) conductive films, gradual replacement of ITO by fluorine-doped tin oxide, and possible introduction of the tin-containing quaternary material, kesterite (copper – zinc – tin sulphide) as a substitute for expensive CdTe and CIGS layer materials, could lead to annual tin consumption of at least 500 tonnes over the next decade.
A fuel cell is an electrochemical cell that converts a source of fuel into electrical energy without combustion. Like batteries, fuel cells can be recharged while operating and they already compete with other types of energy conversion devices such as gas turbines in power plants, petrol engines in vehicles, and batteries in laptop computers. As such, they have the potential to become the dominant technology for automotive engines, power stations and power packs for portable electronics.
Current use of tin in commercial fuel cells is negligible. However, significant opportunities exist in (a) solid oxide fuel cells, where the use of a liquid tin anode allows cells to operate on a wide range of hydrocarbon fuels, including biodiesel and coal, and (b) direct ethanol fuel cells, where a tin-containing electro-catalyst has been found to exhibit high efficiency for oxidising ethanol to CO2 at room temperature.
Of these two distinct technologies, the former appears to offer greater volume potential for tin, particularly since it employs tin as a bulk material rather than as a component of a catalyst, which itself tends to be used in rather small quantities. It is conceivable that the successful development of the liquid tin anode fuel cell for large biomass / coal power generation plants in the longer term (maybe 2020 and beyond) could lead to annual tin requirements running into thousands of tonnes.
Fuel catalysts based on tin alloy pellets have been marketed for over 25 years as low tech fuel-saving devices with the added benefit of significantly reducing toxic emissions. At least 10 manufacturers currently operate globally and sales have mainly been in the automotive and marine sectors.
However, widespread scepticism of the claims made for the technology has severely hampered market penetration. ITRI is actively working in this field, both with regard to substantiating performance benefits and elucidating the mechanism of action of the catalyst on the fuel.
Although current tin usage is only a few tens of tonnes per annum, a successful outcome to ITRI's studies and further improvement of catalytic efficiency by radical re-design of the product could realistically lead to annual tin consumption in the 5,000 – 10,000 tonne range.