Aprotic Li-O batteries represent promising alternative devices for electrical energy storage owing to their extremely high energy densities. Upon discharge, insulating solid LiO forms on cathode surfaces, which is usually governed by two growth models, namely the solution model and the surface model. These LiO growth models can largely determine the battery performances such as the discharge capacity, round-trip efficiency and cycling stability. Understanding the LiO formation mechanism and controlling its growth are essential to fully realize the technological potential of Li-O batteries. In this review, we overview the recent advances in understanding the electrochemical and chemical processes that occur during the LiO formation. In the beginning, the oxygen reduction mechanisms, the identification of O/LiO intermediates, and their influence on the LiO morphology have been discussed. The effects of the discharge current density and potential on the LiO growth model have been subsequently reviewed. Special focus is then given to the prominent strategies, including the electrolyte-mediated strategy and the cathode-catalyst-tailoring strategy, for controlling the LiO growth pathways. Finally, we conclude by discussing the profound implications of controlling LiO formation for further development in Li-O batteries.

Highlights Hard-carbon anode dominated with ultra-micropores (< 0.5 nm) was synthesized for sodium-ion batteries via a molten diffusion–carbonization method. The ultra-micropores dominated carbon anode displays an enhanced capacity, which originates from the extra sodium-ion storage sites of the designed ultra-micropores. The thick electrode (~ 19 mg cm−2) with a high areal capacity of 6.14 mAh cm−2 displays an ultrahigh cycling stability and an outstanding low-temperature performance. Abstract Pore structure of hard carbon has a fundamental influence on the electrochemical properties in sodium-ion batteries (SIBs). Ultra-micropores (< 0.5 nm) of hard carbon can function as ionic sieves to reduce the diffusion of slovated Na+ but allow the entrance of naked Na+ into the pores, which can reduce the interficial contact between the electrolyte and the inner pores without sacrificing the fast diffusion kinetics. Herein, a molten diffusion–carbonization method is proposed to transform the micropores (> 1 nm) inside carbon into ultra-micropores (< 0.5 nm). Consequently, the designed carbon anode displays an enhanced capacity of 346 mAh g−1 at 30 mA g−1 with a high ICE value of ~ 80.6% and most of the capacity (~ 90%) is below 1 V. Moreover, the high-loading electrode (~ 19 mg cm−2) exhibits a good temperature endurance with a high areal capacity of 6.14 mAh cm−2 at 25 °C and 5.32 mAh cm−2 at − 20 °C. Based on the in situ X-ray diffraction and ex situ solid-state nuclear magnetic resonance results, the designed ultra-micropores provide the extra Na+ storage sites, which mainly contributes to the enhanced capacity. This proposed strategy shows a good potential for the development of high-performance SIBs.

Correction for 'Recent advances in understanding of the mechanism and control of LiO formation in aprotic Li-O batteries' by Zhiyang Lyu et al., Chem. Soc. Rev., 2017, DOI: 10.1039/c7cs00255f.

Photoelectrochemical reaction is emerging as a powerful approach for biomass conversion. However, it has been rarely explored for glucose conversion into value-added chemicals. Here we develop a photoelectrochemical approach for selective oxidation of glucose to high value-added glucaric acid by using single-atom Pt anchored on defective TiO2 nanorod arrays as photoanode. The defective structure induced by the oxygen vacancies can modulate the charge carrier dynamics and band structure, simultaneously. With optimized oxygen vacancies, the defective TiO2 photoanode shows greatly improved charge separation and significantly enhanced selectivity and yield of C6 products. By decorating single-atom Pt on the defective TiO2 photoanode, selective oxidation of glucose to glucaric acid can be achieved. In this work, defective TiO2 with single-atom Pt achieves a photocurrent density of 1.91 mA cm−2 for glucose oxidation at 0.6 V versus reversible hydrogen electrode, leading to an 84.3 % yield of glucaric acid under simulated sunlight irradiation.

Li–O2 batteries, possessing the highest theoretical specific energy density among all known Li‐ion‐based batteries, demonstrate great potential as energy storage devices for powering electric vehicles. However, their battery performance is significantly limited by the insulating nature of the discharge product Li2O2, which has a wide bandgap (4–5 eV), resulting in high charge overpotential. Defect engineering of the discharge product emerges as a very promising strategy to improve the electrical conductivity and hence reduce the charge overpotential. The aim of this review is to highlight recent advances and progress in understanding and controlling the defect chemistry of discharge products in Li–O2 batteries. First, the theoretical perspectives of defects in Li2O2 are reviewed, with particular emphasis on defect design and engineering strategies to significantly improve the charge transport properties of Li2O2. Then intermediate defects in Li2O2 formed during the discharge and charge processes and materials with induced defects, including Li2− x O2, doped Li2O2, Li2O2 with surface/grain boundaries, and amorphous Li2O2, which are tailored by engineered catalysts and electrolyte additives are discussed. Finally, other alternative energy carriers for new energy storage chemistry of Li–O2 batteries, such as lithium superoxide, lithium hydroxide, and lithium carbonate, will also be discussed.

Superoxide (O 2 − ) species play a crucial role in determining the charge kinetics for aprotic lithium−oxygen (Li−O 2 ) batteries. However, the growth of O 2 − -rich lithium peroxide (Li 2 O 2 ) is challenging since O 2 − is thermodynamically unfavorable and unstable in an O 2 atmosphere. Herein, we reported the synthesis of defective Li 2 O 2 with tunable O 2 − via K + doping. The K + dopants can successfully stabilize O 2 − species and induce the coordination of Li + with O 2 − , leading to increased Li vacancies. Compared to the pristine Li 2 O 2 , the as-prepared defective Li 2 O 2 can be charged at a lower overpotential in Li−O 2 batteries, which is ascribed to further increased Li vacancies contributed by the depotassiation process at the onset of the charge process. Our findings suggest a new strategy to better control O 2 − species in Li 2 O 2 by K + dopants and provide insights into the K + effects on charge mechanism in Li−O 2 batteries.

We report the synthesis of porous CoMoO nanorods and their applications in lithium oxygen (Li-O) and lithium ion (Li-ion) batteries. The unique porous structures of CoMoO nanorods can promote the permeation of electrolyte and benefit the transport of lithium ion. When employed as the cathode catalyst for a Li-O battery, CoMoO nanorods deliver an improved discharge capacity (4680 mA h g), lower charge potential and better cycle stability (41 cycles at 500 mA h g capacity limit) compared with the bare carbon. When employed as an anode in Li-ion batteries, CoMoO nanorods can retain a capacity of 603 mA h g after 300 cycles (400 mA g) and exhibit excellent rate capability.

Co3O4 surface functionalized porous carbon nanotubes were designed as an efficient cathode catalyst for Li–O2 batteries, with p-CNT to facilitate Li+ and O2 diffusion, and with Co3O4 to achieve a low charge overpotential.