![]() It is also worth noting that many early studies should be interpreted with caution, because many of the cell electrochemistries reported were mainly based on parasitic reactions (e.g., where a carbonate electrolyte is used, and the major product on charge is CO 2). Since Bruce et al.’s work and also driven by the advances of materials science and the increased need for renewable energies, research on lithium–air batteries has increased substantially. Most of this review will be dedicated to discussing nonaqueous lithium–air batteries. As a result, much less research is done on the aqueous system compared to the aprotic one. H 2O rather than LiOH (as in the nonaqueous system) is the product, the specific energy of the aqueous system is lower, around 2170 Wh/kg.H 2O then precipitates and deposits on the positive electrode.(13,14) During discharge, the generated LiOH is dissolved in the electrolyte until reaching its saturation solubility LiOH H 2O, the forward reaction characterizing discharge and the backward one charge.On the other hand, the aqueous lithium–air cell (e.g., at alkaline conditions) is described by the following reaction: 4Li + 6H 2O + O 2 ↔ 4LiOH For instance, the formation of Li 2O 2 (2Li + O 2 ↔ Li 2O 2), Li 2O (4Li + O 2 ↔ 2Li 2O), and LiOH (4Li + 2H 2O + O 2 ↔ 4LiOH) lead to theoretical capacities of 1165, 1787, and 1117 mAh/g, respectively hence the corresponding specific energies, assuming a voltage of around 3 V for them, would be 3495, 5361, and 3350 Wh/kg, clearly several times higher than those of typical LIBs (500–800 Wh/kg). (9−12) The nonaqueous lithium–air batteries will have varied theoretical specific energies (defined as Wh/kg of the redox active material), depending on the type of lithium–oxygen product formed during discharge. There are two types of lithium–air batteries, one based on aqueous electrolytes and the other using nonaqueous electrolytes. In the long term, much more energy-dense batteries that can significantly reduce battery cost and weight and afford long driving ranges is a critical goal. While Tesla’s performance highlights the importance and necessity of re-engineering the car, their strategy increases the cost and reduces the effective loading capacity of the car. Nevertheless, in 2017, the Tesla Model 3 successfully demonstrated a driving range of more than 300 miles based on current LIB technologies, and a new Tesla model to be released soon is claimed to achieve 400 miles/charge these improvements in driving ranges are mainly obtained by loading more batteries on board (478 kg for battery packs of 80.5 kWh accounting for 30% of vehicle weight in the Model 3). (4) This idea certainly drives more fundamental research activities in the so-called beyond Li-ion battery chemistries (such as Si-, S-, and O 2-based Li redox chemistries). Therefore, the LIB, unless it is large and thus extremely costly, is unlikely to allow a driving range of 500 miles/charge to be achieved, this range being offered by a single refill of a petrol tank. ![]() Around 5 years ago, one opinion evolved in the battery community that LIBs may not be the energy storage technology that can realize mass EV adoption, because scientists estimate that the scope for energy density improvement in LIBs is at most another 30%. ![]() Current EVs are predominantly based on lithium ion batteries (LIBs), and active R&D efforts are still being devoted to further optimizing the LIB chemistry. ![]() The core issue facing complete electrification of transportation is the development of a good battery, that is, a long-lived, safe, affordable battery with sufficient power and energy densities to cover most driving range scenarios for a day. Recently established cell chemistries based on the superoxide, hydroxide, and oxide phases are also summarized and discussed. We introduce the fundamental principles and critically evaluate the effectiveness of the different strategies that have been proposed to mitigate the various issues of this chemistry, which include the use of solid catalysts, redox mediators, solvating additives for oxygen reaction intermediates, gas separation membranes, etc. By drawing attention to reports published mainly within the past 8 years, this review provides an updated mechanistic picture of the lithium peroxide based cell reactions and highlights key remaining challenges, including those due to the parasitic processes occurring at the reaction product–electrolyte, product–cathode, electrolyte–cathode, and electrolyte–anode interfaces. Significant advances have been achieved both in the mechanistic understanding of the cell reactions and in the development of effective strategies to help realize a practical energy storage device. Nonaqueous lithium–air batteries have garnered considerable research interest over the past decade due to their extremely high theoretical energy densities and potentially low cost. ![]()
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