|Dr. Tarascon’s view of the battery landscape for the next few decades.|
In a review of the challenges facing Li-ion battery development published in an open access paper in Philosophical Transactions of the Royal Society A, materials scientist Dr. Jean-Marie Tarascon of the Laboratoire réactivité et chimie des solides (LRCS) at Université de Picardie Jules Verne, CNRS proposes a two-fold increase in energy density over the next 30 years, most likely coming from the Li–air system.
For applications from which cost and materials resources are crucial, organic Li-ion and Na-ion will play an important role in the years to come, he also projects. These predictions, he cautions, do not take into account “complete out-of-the box solutions to electrochemically store electricity, but some of the concepts related to the latter are hopefully maturing in a few laboratories.”
Although currently at Université de Picardie Jules Verne, Tarascon spent most of his career in the US, including at Bell Laboratory and Bellcore up to 1994. At the beginning of the 90s, Bellcore asked him to create a new group on energy storage, which was rapidly prolific with, in particular, the optimization of new organic electrolytes for high voltage electrodes thus allowing the achievement of the LiMn2O4/C Li-ion battery or the discovery of the plastic Li-ion battery (PLiON), which is now commercialized.
Dr. Tarascon says that the most important results to which he contributed are the stabilization of the LiMn2O4-electrolyte interface; the design of an electrochromic system resting only on the presence of electrochemically active species in solution; the pioneering role of the LRCS in the contribution of mechanical grinding to the performances optimization of the electrode materials for Li-ion batteries; and the discovery of a new reversible Li reaction mechanism in highly divided mediums.
In the paper, Tarascon notes that:
...we should be aware that a colossal task is awaiting us if we really want to compete with gasoline, as an increase by a factor of 15 is needed for the energy delivered by a battery (180 Wh kg-1) to match the one of a litre of gasoline (3000 Wh l-1; taking into account corrections from Carnot’s principle). Knowing that the energy density of batteries has only increased by a factor of five over the last two centuries, our chances to have a 10-fold increase over the next few years are very slim, with the exception of unexpected research breakthroughs.
Nevertheless, he writes, “there is room for optimism as long as we pursue paradigm shifts while keeping in mind the concept of materials sustainability”, such as new ways to prepare electrode materials via eco-efficient processes or the use of organic rather than inorganic materials or new chemistries. Achieving these concepts will require the inputs of multiple disciplines, Tarascon emphasizes.
The chances of drastically improving current Li-ion cell energy density are mainly rooted in cathode materials that could either display greater redox potentials (e.g. highly oxidizing) or larger capacity (materials capable of reversibly inserting more than one electron per 3d metal).
In the long term, improving the Li-ion technology while preserving its sustainable aspect will require out-of-the-box solutions. Metal–air systems (Zn–air, Al–air and more so Li–air) have long been recognized as great candidates for achieving staggering energy-density increases. However, despite the efforts that went into these technologies, very little progress has been made regarding their reversibility so that they rapidly fell into oblivion.
Using the most attractive Li–air system as a reversible battery must at least clear three scientific/technological hurdles: (i) designing efficient oxygen electrodes knowing that confectioning such electrodes has been a nightmare for fuel cells, (ii) ensuring the development of electrode formulations that are capable of solvating oxygen and are stable with respect to the superoxide anions, and (iii) mastering the Li–electrolyte interface that we could not solve for the last 25 years within the field of Li batteries, the reason why the presently successful Li-ion battery technology has surfaced in the first place. Solving all of these at once is a colossal task that will require several years of cooperative research.
Despite that, Tarascon notes, there is reason for optimism given the increasing number of groups becoming involved with the Li–air system. Tarascon also cited Li-Sulfur (Li-S) as a promising system. Overall, Li–air and Li–S technologies beneficially share the same problems, he writes, as any advance in Li–air can be directly implemented in Li–S and vice versa. Their penetration into the market is a few years ahead, with Li-S most likely being the first one, he predicts.
The implementation of electrodes, enlisting raw abundant elements made via eco-efficient processes or obeying the renewable concept with zero carbon footprint, together with recent advances in sustainable and green Li–air systems, is shaping a bright future for electrochemical storage over the years to come...Regardless of the fact that future predictions are very hard, it is a certainty that sustainable and greener Li-based storage technologies will no longer be science fiction in the years to come. Achieving such a next generation of storage technologies will eagerly require interdisciplinary approaches, and our success will depend on how good we are in setting cross-fertilization between these different disciplines.
Addressing energy-related issues is a worldwide problem shared by many countries. Nevertheless, while targeting similar objectives and having similar road maps, various countries have tendencies to favour national over worldwide programmes. Time is limited, and it is urgent for our politics to find means/infrastructures to enhance the cross sharing of information between national programmes dealing with energy-related matters, both at the European and international levels. Concrete actions must be rapidly taken if we want to secure a bright future for the generations to come and to our planet as a whole.
J.-M. Tarascon (2010) Key challenges in future Li-battery research. Phil. Trans. R. Soc. A vol. 368 no. 1923 3227-3241 doi: 10.1098/rsta.2010.0112