Hyderabad: A team of researchers at the Indian Institute of Technology, Hyderabad, has developed electrodes for producing rechargeable lithium ion batteries with high energy densities. Dr Surendra K. Martha and his team have developed new electrode (both cathode and anode) material with higher specific capacities than conventionally used electrodes.
They have also developed two kinds of cathode material with better capacity than existing systems. In one, they synthesised mixtures of transition metal oxide and carbon-coated lithium manganese phosphate to form ‘blends’ that showed excellent stability under repeated cycling and very little energy loss over cycle life.
Dr Martha and his team have used nanoengineering in which the material used to fabricate the cathode is a few nanometres in dimension. In comparison, a human hair is approximately 80,000-100,000 nanometre in diameter. The capacity of these electrodes is around 225 mAhg-1, higher than those of current cathode material. In a further development, the team has doped cathode material with fluorine and magnesium, to result in better capacities.
Dr Martha’s team, in collaboration with Oak Ridge National Laboratory USA, developed a unique organic-binder-less; additive-free 3D electrode architecture made of silicon and carbon in nano-dimensions and have coated it on a current collector made of carbon fibre, instead of copper foil that is used in conventional cells.
The advantage of this material is that there is enough space between silicon and the surrounding carbon coating, which allows for volume expansion and contraction without pulverisation of the silicon. Reversible capacities over 2000 mAh g-1 at C/10 rate have been obtained for these electrodes. A provisional Indian patent has been filed for this work.
Dr Martha’s new electrodes can result in better-performing lithium batteries with higher energy density than is currently possible.
Indeed, the team has already shown that combining the cathode and anode materials developed by them in coin-type lithium ion cell results in energy densities greater than 500 WH kg-1. This is more than twice the energy density seen in commercial lithium ion cells.
"I am in the process of scaling up and designing pouch and prismatic batteries from this small product", says Dr. Martha.
This, in R&D parlance, is the first step in the path of commercialisation of high energy batteries that could power future electric vehicles on the Indian road.
Dr Martha’s studies have been published in the Journal of The Electrochemical Society, Journal of Power Sources, Ionics, Journal of Energy Storage and the American Chemical Society’s open access journal, ACS-Omega.
