After Gutenberg

At the recent, Energy 2.0 Conference at MIT, an A123Systems employee shows off a plug-in hybrid. A123Systems has agreed to supply HyMotion with advanced lithium batteries. The converted, Toyota Prius is an example of HyMotion making use of A123Systems batteries.

There is considerable research into electrochemistry in nonaqueous media, and specifically in the area of advanced lithium batteries. Two U.S. companies — A123Systems (recently purchased by Cobasys) and Altairnano (recently receiving a 2.2 million dollar order from Phoenix Motorcars) — have promoted large format battery modules recently that feature such development. And, A123Systems is just one example of the development underway at one major research institution — the Massachusetts Institute of Technology.

Now Electrifying Times Remy Chevalier relays an advertisement in TechBrief for an inorganic additive that “appears to act as a superior SEI (Solid Electrolyte Interface) promoter.”

Lithium dinitramide, LiN(NO2)2 has shown promise as an additive to nonaqueous electrolytes in rechargeable and non-rechargeable lithium-ion-based electrochemical power cells. Such non-aqueous electrolytes consist of lithium salts dissolved in mixtures of organic ethers, esters, carbonates, or acetals. The benefits of adding lithium dinitramide (which is also a lithium salt) include lower irreversible loss of capacity on the first charge/discharge cycle, higher cycle life, lower self-discharge,
greater flexibility in selection of electrolyte solvents, and greater charge capacity.

The need for a suitable electrolyte additive arises as follows: The metallic lithium in the anode of a lithium-ion-based power cell is so highly reactive that in addition to the desired main electrochemical reaction, it engages in side reactions that cause formation of resistive films and dendrites, which degrade performance as quantified in terms of charge capacity, cycle life, shelf life, first-cycle irreversible capacity loss, specific power, and specific energy. The incidence of side reactions can be reduced through the formation of a solid-electrolyte interface (SEI) – a thin film that prevents
direct contact between the lithium anode material and the electrolyte. Ideally, an SEI should chemically protect the anode and the electrolyte from each other while exhibiting high conductivity for lithium ions and little or no conductivity for electrons. A suitable additive can act as an SEI promoter.

Heretofore, most SEI promotion was thought to derive from organic molecules in electrolyte solutions. In contrast, lithium dinitramide is inorganic. Dinitramide compounds are known as oxidizers in rocket-fuel chemistry and until now, were not known as SEI promoters in battery chemistry. Although the exact reason for the improvement afforded by the addition of lithium dinitramide is not clear, it has been hypothesized that lithium dinitramide competes with other electrolyte constituents to react with lithium on the surface of the anode to form a beneficial SEI. Apparently, nitrides and oxides that result from reduction of lithium dinitramide on the anode produce a thin, robust SEI different from the SEIs formed from organic SEI promoters. The SEI formed from lithium dinitramide is more electronically insulating than is the film formed in the presence of an otherwise identical electrolyte that does not include lithium dinitramide. SEI promotion with lithium dinitramide is useful in batteries with metallic lithium and lithium alloy anodes.

On May 11 Masatami Takimoto, executive vice president in charge of powertrain development, announced that an advanced lithium-ion battery was technically ready. Matsushita Electric Industrial Co. developed the batteries that Toyota has been testing for some time, mainly in Japan, but also in Europe.

Particularly with an expanding market for HEVs (Hybrid Electric Vehicles) — the sales leader is the Toyota Prius — it would seem that a market is developing for lithium battery components, which is a good indicator. Even key players, like European giants Robert Bosch and Continental, U.S.-based Delphi and Cobasys, and Japanese giants Hitachi and Denso are working to integrate battery modules into a total energy-storage system. All of this development is exciting because electric vehicles need batteries and advanced lithium batteries are the smallest and lightest means of rechargeable electrical storage currently becoming available for transportation applications. However, as previously noted, the Big Oil interest in such development is disconcerting.