Preface

The thought of writing a book on electrolytes has been lingering in my mind since 2015. While the idea of such a book project has always appeared tantalizing, the reality of my day job prevented me from starting. The folder I created for this project remained on my desktop untouched for 5 years. This was also the 5 year period when research on electrochemical energy storage (aka batteries) witnessed exponential growth around the world. Although I never started writing, I also never stopped planning its chapters and contents.

Then, in the spring of 2020, the whole world ground to a sudden halt due to the Covid 19 pandemic. Like most people, I was forced to telework, to attend and speak at tiresome online meetings and seminars, while having only occasional privileges to visit the laboratory and office physically. After a few weeks, I decided that it was the time to start this book.

The time could not have been more perfect. As scientists from around the world were forced away from their benches, experimental advances in electrochemical energy storage materials and chemistry research were bound to slow down compared with the previous hectic decade. This relative tranquility gifted us a precious opportunity to look back and think.

Meanwhile, there has not been a book of this kind available that links fundamental knowledge in ionics and electrodics to the basic applications of electrolytes in energy storage devices.

On the one hand, research papers, reviews, perspectives and monographs are being published in such record numbers that the individual researcher often finds it impossible to follow them all, but all of these publications are almost exclusively intended for veteran researchers in the field, providing little or no introductory ramp for readers new to the field, such as students and postdocs.

On the other hand, in basic electrochemistry, there are many excellent books that teach fundamental knowledge, among which are the three “Bibles”: (1) Modern Electrochemistry by Bockris and Reddy, (2) Electrochemical Methods: Fundamentals and Applications by Bard and Faulkner, and (3) Electrochemical Systems by Newman and co-authors, which have been published in several editions. These three exceptional treatises laid out the rigorous mathematical and thermodynamic foundations of the basic principles in electrochemistry, ionics and modern electrodics. However, in the fast-evolving fields of energy storage science and technology, especially lithium-ion batteries and the emerging battery chemistries and materials, one often has difficulty in establishing direct lineage and relevance from the fundamental knowledge taught in these books.

One example is Modern Electrochemistry. In its most recent edition, published in 2000, the authors predicted the hydrogen fuel cell to be the prevalent power source for future vehicles, with only fleeting mention of batteries, and the lithium-ion battery, although already commercialized and in extensive use for nearly a decade by then, was not even mentioned in the book. Needless to say, the interphases and the associated chemistries and kinetics in those advanced batteries went beyond what the classical ionics and electrodics can describe.

The world has changed significantly in this new millennium, and the lithium-ion battery has played an indisputable role in this. The recognition of Professors Stanley M. Whittingham, John B. Goodenough and Dr Akira Yoshino by the award of the Nobel Prize in Chemistry in 2019 marked the apex of this great invention, and research on new energy storage chemistries and mechanisms is becoming ever more important in the new era after the pandemic of 2020–2022.

This book aims to fill the gap mentioned above. It intends to be a friendly yet authoritative “textbook” that will help beginners to overcome the learning curve, and bring them to an eventually sophisticated stage by the end of it. These “beginners” could be students or postdocs who want to enter the fields of electrochemical energy storage, electrochemistry, and materials science and engineering, or any researchers new to these subjects.

The book assumes that readers have a chemistry or materials background, already armed with a knowledge of basic thermodynamics and chemistry. It starts with fundamental knowledge before moving on to applications. Emphasis is placed on established knowledge, but new findings important to the field are also discussed. Special efforts are made to link the fundamentals to the actual problems encountered with real-life devices. Given the success of lithium-ion batteries in shaping our mobile life, and the research on diverse battery materials and chemistries being pursued as an essential part of our energy future, an unsymmetrical emphasis will inevitably be placed on the electrolytes and interphases in batteries.

Some mathematics is presented order to show the beauty of the fundamental knowledge of electrolytes in bulk and at interfaces, but one could completely skip the derivations and jump directly to the conclusions without losing comprehension of the overall storyline.

This book is not intended to be a comprehensive review of past work or a monograph covering recent advances, hence for well-established facts I do not see the necessity of providing all the available literature references. Instead, only selected classic and seminal works that constitute the foundational knowledge are cited.

All illustrations in the book, with the exception of Figures 12.6, 12.7 and 14.11, were created by me. In 1977, when China was still struggling to exit the suffocating shadow of the Cultural Revolution, my grandmother bought me a special book that suddenly opened my horizons: the Chinese translation of One Two Three … Infinity: Facts and Speculations of Science by Professor George Gamow. In that masterpiece, all the cartoons were drawn by the author. Looking back, the impact of these artistic, humorous, yet inspiring drawings on a boy who was first touched by modern science can never be overestimated. I possess talents neither in science nor arts that can be comparable to those of Professor Gamow, but I hope that, with my humble efforts with the illustrations in this book, I pay homage to him for his influence on me.

Kang Xu