Next-gen batteries could bring electric cars closer to market

Research chemists at BASF are developing next-generation lithium-ion batteries that will have significantly improved energy densities and lower material costs than existing products.

It is hoped the technology will increase the range of the current crop of hybrid vehicles and bring long-distance all-electric cars closer to mainstream production.

Company research director Dr Andreas Kreimeyer said: ‘Existing batteries are too expensive, their range is too limited and their weight is still much too high.

‘We must develop innovative concepts for more efficient electric cars if we are to convince potential users. Our activities must therefore be focused on guaranteeing a range of 400km for a battery weight of less than 200kg.’

The first stage in this process will focus on producing new materials for the positive electrode, or cathode, of the battery.

The cathode is usually composed of a metal oxide, generally cobalt-based, while the negative anode is made of carbon, generally graphite. Cathode materials must be able to accept and release lithium ions repeatedly (for recharging) and quickly (for high current) — making them ripe for development.

‘To put it simply… we have to come up with a means of transport that ensures the fast transfer from the anode to cathode and back,’ said Prof Jürgen Janek, of Justus Liebig University Giessen, who heads the Scientific Network on Batteries, an academic research group supported by BASF.

BASF and its research partners have been developing cathodes with various combinations of nickel, cobalt and manganese — so-called NCM cathodes that offer improved energy density and lower costs relative to current li-ion batteries.

‘Cobalt is very expensive and in the future we would like to offer materials with a low cobalt content but with the same performance,’ said Andreas Fischer, head of electrochemistry research at BASF.

The company recently announced that they will be building a plant dedicated to producing NCM cathode material at Elyria, Ohio, with additional state funding from the US Department of Energy. Production will begin on a range of NCM products in 2012 with a view to seeing the cathode technology in cars by 2015.

Even with firm commitments such as the Elyria plant, the challenges facing the industry remain considerable. Kreimeyer estimated that, at most, 10 per cent of the worldwide fleet of automobiles will be electromobility-based by 2030.

BASF is already looking further ahead at what it calls third- and fourth-generation lithium-ion batteries. It nows has a working prototype lithium-sulphur battery, which, according to Fischer, blurs the boundary between fuel cell and battery.

‘The beauty of a lithium-sulphur battery is that you have a high gravimetric energy density, low costs for raw materials and low operational temperature,’ he said.

However, Fischer admitted there are potential safety issues relating to lithium-sulphur batteries and also that the cycle life is relatively low, meaning the earliest production will probably be around 2020.

Another potentially fruitful line of research is in the chemistry of the battery electrolyte, which is a gel-like material that facilitates the migration of ions from the anode to the cathode. BASF has been investigating various alternatives based on membranes, polymers and solid-state ceramics that achieve better conductivity with less toxicity than the gels.