Lithium-oxygen batteries with ultrahigh energy density have received considerable attention as of the future energy storage technologies. The development of effective electrocatalysts and a corresponding working mechanism during cycling are critically important for lithium-oxygen batteries. Here, a single cobalt atom electrocatalyst is synthesized for lithium-oxygen batteries by a polymer encapsulation strategy. The isolated moieties of single atom catalysts can effectively regulate the distribution of active sites to form micrometre-sized flower-like lithium peroxide and promote the decomposition of lithium peroxide by a one-electron pathway. The battery with single cobalt atoms can operate with high round-trip efficiency (86.2%) and long-term stability (218 days), which is superior to a commercial 5 wt% platinum/carbon catalyst. We reveal that the synergy between a single atom and the support endows the catalyst with excellent stability and durability. The promising results provide insights into the design of highly efficient catalysts for lithium-oxygen batteries and greatly expand the scope of future investigation.

Li-O 2) batteries with high theoretical energy densities offer considerable potential for a new generation of energy storage technology. [1] In 1996, the first nonaqueous Li-O 2 battery was introduced with a polymer organic electrolyte and a carbon-cobalt composite cathode by Abraham and Jiang. [2] This was followed by the verification of the rechargeability of Li-O 2 batteries with manganese dioxide-super S cathodes for over 50 cycles by Bruce and co-workers, [3] after which nonaqueous Li-O 2 batteries received substantial research attention worldwide. A typical nonaqueous Li-O 2 battery includes a Li metal anode, an aprotic electrolyte and an O 2 cathode. It operates according to the reaction 2Li + O 2 ↔ Li 2 O 2 (2.96 V vs Li/Li +), in which O 2 is reduced to form Li 2 O 2 on the cathode during discharging and Li 2 O 2 is decomposed to O 2 and Li + through a reversible charging process. In this way, the battery delivers exceptional theoretical energy density of ≈3600 Wh kg −1. [4] This report is centered on nonaqueous Li-O 2 batteries, and the use of the term "Li-O 2 batteries" mentioned below represents "nonaqueous Li-O 2 batteries." To date, enormous progress has been achieved in the understanding and application of high-performance Li-O 2 batteries, however, their low practical discharge capacity, poor rate capability, low round-trip efficiency, and inferior cycling stability have greatly blocked their practical applications. The current major scientific and technical challenges of Li-O 2 batteries can be summarized as follows. 1) The slow kinetics of formation and decomposition of the discharge products lead to poor rate capability and low round-trip efficiency. 2) Cathode corrosion and electrolyte decomposition due to the attack by the discharge intermediates such as superoxide species, giving rise to poor cycling stability. 3) Pore clogging on the cathode arising from the stacking of insulated, insoluble discharge products blocks the mass transfer and oxygen/Li + diffusion, limiting the capacity and degrading the cycling performance. 4) The inevitable side reactions between the highly reactive Li anode and the organic electrolyte, crossover O 2 , CO 2 , etc., and the redox mediators (RMs), give rise to premature battery death. [1a,5] 5) The unavoidable Li dendrites caused by uncontrollable deposition of lithium, as well as the risk of collapse of the lithium anode due to the volume change during iterative plating/stripping processes, increase the probability of safety problems. [6] Consequently, the slow kinetics of Li 2 O 2 Porous materials possessing high surface area, large pore volume, tunable pore structure, superior tailorability, and dimensional effect have been widely applied as components of lithium-oxygen (Li-O 2) batteries. Herein, the theoretical foundation of the porous materials applied in Li-O 2 batteries is provided, based on the present understanding of the battery mechanism and the challenges and advantageous qualities of porous materials. Furthermore, recent progress in porous material...

At present, photoassisted Li–air batteries are considered to be an effective approach to overcome the sluggish reaction kinetics of the Li–air batteries. And, the organic liquid electrolyte is generally adopted by the current conventional photoassisted Li–air batteries. However, the superior catalytic activity of photoassisted cathode would in turn fasten the degradation of the organic liquid electrolyte, leading to limited battery cycling life. Herein, we tame the above limitation of the traditional liquid electrolyte system for Li-CO2 batteries by constructing a photoassisted all-solid-state Li-CO2 battery with an integrated bilayer Au@TiO2/Li1.5Al0.5Ge1.5(PO4)3 (LAGP)/LAGP (ATLL) framework, which can essentially improve battery stability. Taking advantage of photoelectric and photothermal effects, the Au@TiO2/LAGP layer enables the acceleration of the slow kinetics of the carbon dioxide reduction reaction and evolution reaction processes. The LAGP layer could resolve the problem of liquid electrolyte decomposition under illumination. The integrated double-layer LAGP framework endows the direct transportation of heat and Li+ in the entire system. The photoassisted all-solid-state Li-CO2 battery achieves an ultralow polarization of 0.25 V with illumination, as well as a high round-trip efficiency of 92.4%. Even at an extremely low temperature of −73 °C, the battery can still deliver a small polarization of 0.6 V by converting solar energy into heat to achieve self-heating. This study is not limited to the Li–air batteries but can also be applied to other battery systems, constituting a significant step toward the practical application of all-solid-state photoassisted Li–air batteries.