Indicative Energy Technology Assessment of Advanced Rechargeable Batteries

What is it about?

Several ARBT have been appraised here, including Lithium-Ion batteries (LIB), Li-Ion Polymer (LIP) and Sodium Nickel Chloride (NaNiCl) [or ‘ZEBRA’] batteries. These are compared to the more mature Ni–Cd batteries. Specifications for the materials content of the batteries were taken from emerging, commercially available devices. An indicative energy technology assessment of such ARBTs was undertaken using energy, environmental, and economic appraisal techniques. It is ‘indicative’ in the sense of being a simplified evaluation and illustration of the performance of state-of-the-art rechargeable batteries. Nevertheless, such assessments provide a valuable evidence base for developers, policy makers, and other stakeholders. The energy analysis and environmental appraisal were conducted on a ‘cradle-to-gate’ life-cycle basis for each of the ABRTs. The suitability of these advanced rechargeable energy storage devices for different applications, such as electric vehicles (EV), consumer electronics, load levelling, and stationary power storage, has also been assessed technically. LIBs currently dominate the rechargeable battery market, and are likely to continue to do so in the short term in view of their excellent all-round performance and firm grip on the consumer electronics market. However, in view of the competition from Li-Ion Polymer their long-term future is uncertain. The high charge/discharge cycle life of Li-Ion batteries means that their use may grow in the electric vehicle (EV) sector, and to a lesser extent in load levelling, if safety concerns are overcome and costs fall significantly. LIP batteries exhibited attractive values of gravimetric energy density, volumetric energy density, and power density. Consequently, they are likely to dominate the consumer electronics market in the long-term, once mass production has become established, but may struggle to break into other sectors unless their charge/discharge cycle life and cost are improved significantly. ZEBRA batteries are presently one of the technologies of choice for EV development work. Nevertheless, compared to other ARBT, such batteries only represent an incremental step forward in terms of energy and environmental performance.

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Why is it important?

‘Advanced Rechargeable Battery Technologies’ (ARBT) can be characterised as having higher cell voltages and higher energy densities compared to more mature technologies, such as Nickel–Cadmium (Ni–Cd). Research into this new breed of batteries only began 40 years ago. One of the factors driving their recent development has been consumer demand for portable electronic equipment, such as mobile phones, mp3 players, tablets, and laptop computers. In order to produce truly portable electronic devices, higher energy density batteries are required that are thus lighter and more compact. They constitute a significant proportion of the total mass and volume of such electronic devices. In order to achieve higher energy densities, researchers have considered more reactive electrode materials, such as lithium and sodium, that exhibit higher electrode potentials and in turn higher cell voltages. Higher cell voltages mean that fewer cells need to be joined in series to reach the desired battery voltage, which reduces the volume and mass of the battery and hence increases the energy density. Lithium and sodium are also considerably lighter than more traditional cathode materials, such as lead or cadmium, which further increases their energy density benefit. However, the highly reactive nature of lithium and sodium meant that conventional aqueous electrolytes could not be used. The main alternatives to aqueous electrolytes were a metal salt dissolved in an organic solvent, which gave rise to Li-Ion batteries, and a solid macro-molecule or ceramic, which were the technologies that prompted the development Li-Ion Polymer and ‘ZEBRA’ batteries respectively. The latter term was derived from ‘ZEolites applied to Battery Research Africa’, which was a secretive collaborative project in the mid-1970s – during the ‘apartheid’ era – between the South African Council for Scientific and Industrial Research (CSIR) and the Anglo American Corporation of South Africa [16]. They are high-temperature electric batteries that use molten salts as an electrolyte.

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