Martin Winter

Electrochemical energy conversion devices are pervasive in our daily lives. Batteries, fuel cells and supercapacitors belong to the same family of energy conversion devices. They are all based on the fundamentals of electrochemical thermodynamics and kinetics. All three are needed to service the wide energy requirements of various devices and systems. Neither batteries, fuel cells nor electrochemical capacitors, by themselves, can serve all applications.

Insertion electrode materials are included in the majority of ambient-temperature rechargeable batteries. The reason for their widespread application is the fact that electrochemical insertion ("electroinsertion") reactions are intrinsically simple and reversible. The term electroinsertion refers to a host/guest solid-state redox reaction involving electrochemical charge transfer coupled with insertion of mobile guest ions from an electrolyte into the structure of a solid host, which is a mixed electronic and ionic conductor. [...]

This Review covers a sequence of key discoveries and technical achievements that eventually led to the birth of the lithium-ion battery. In doing so, it not only sheds light on the history with the advantage of contemporary hindsight but also provides insight and inspiration to aid in the ongoing quest for better batteries of the future. A detailed retrospective on ingenious designs, accidental discoveries, intentional breakthroughs, and deceiving misconceptions is given: from the discovery of the element lithium to its electrochemical synthesis; from intercalation host material development to the concept of dual-intercalation electrodes; and from the misunderstanding of intercalation behavior into graphite to the comprehension of interphases. The onerous demands of bringing all critical components (anode, cathode, electrolyte, solid-electrolyte interphases), each of which possess unique chemistries, into a sophisticated electrochemical device reveal that the challenge of interfacing these originally incongruent components often outweighs the individual merits and limits in their own properties. These important lessons are likely to remain true for the more aggressive battery chemistries of future generations, ranging from a revisited Li-metal anode, to conversion-reaction type chemistries such as Li/sulfur, Li/oxygen, and metal fluorides, and to bivalent cation intercalations.