Lithium attracted battery researchers for an obvious reason. The metal is extremely light, and has electrochemical properties that allow batteries to store considerable energy for their size and weight. But there was good cause why early lithium batteries were not safe enough.
Lithium Metal Created a Different Safety Problem
Primary lithium batteries eventually found uses in devices such as watches, cameras and medical equipment. But lithium metal also created a difficult safety problem.
Early lithium batteries used metallic lithium as an electrode. Lithium is highly reactive, and battery designers had to control its reactions
carefully. For this reason, early lithium batteries were not entirely safe.
Primary Lithium Cells Contained Flammable Solvents
Primary lithium cells could contain flammable solvents, while unwanted reactions could generate heat. Research into lithium battery hazards has shown that both primary lithium and rechargeable lithium-ion batteries can experience dangerous reactions if they operate outside their intended conditions.
Rechargeable Lithium Batteries Were A Further Challenge
Rechargeable lithium batteries presented an additional challenge. Repeated charging could create conditions in which lithium metal formed where it was not wanted.
Internal short circuits, excessive temperatures or other faults could then produce rapid heating. Once a battery begins heating through self-reinforcing reactions, the process could develop into thermal runaway.
This Did Not Mean Lithium Batteries Were Abandoned
This did not mean lithium batteries were abandoned. Their enormous potential made solving the safety problem worthwhile. Researchers gradually moved toward rechargeable lithium-ion designs, that did not require metallic lithium at the negative electrode during normal operation.
Sony commercialized lithium-ion batteries in 1991, helping open the way to their widespread use in portable electronics.
We Cannot Judge a Battery By Energy Density Alone
The lesson was important: a battery could not be judged by energy density alone. We must also control heat, prevent internal short circuits, and ensure it remains stable during charging, discharging and storage.
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