Lithium Cell with No Heavy Metals

NEC claims to have developed a transition-metal-free lithium-ion battery, says Electronics World UK.

Called “organic radical battery,” this is a new type of lithium-ion battery which is attractive as an environmentally friendly, high power, high energy density rechargeable battery.

In the battery, polyradicals are used as an active material in cathodes instead of a transition-metal oxide, usually cobalt or manganese oxides. The polyradical is a nitroxyl polyradical: poly 2,2,6,6-tetramethylpiperidinoxyl-4-yl methacrylate (PTMA).

Both lithium metal and a graphite intercalation compound have been tried as anode active materials with carbonate into which lithium salt is dissolved as the electrolyte solution.

“In the charge-discharge curves, there was no obvious voltage plateau. Average voltage was 3.53V for lithium and 3.44V for graphite, slightly lower than those of normal lithium-ion batteries,” said researchers. “The initial specific capacity of the PTMA was 60-100mAh/g.”

Cycle life of the PTMA electrode is claimed to be 92% after 1,000 cycles – so anode material limits the cycle life. A complete prototype cell achieved a discharge of 3.5V and over 1,000 cycles at a capacity of 70Ah/g.