Compared to nanomaterials exposing nonpolar facets, polar-faceted nanocrystals often exhibit unexpected and interesting properties. The electrostatic instability arising from the intrinsic dipole moments of polar facets, however, leads to different surface configurations in many cases, making it challenging to extract detailed structural information and develop structure-property relations. The widely used electron microscopy techniques are limited because the volumes sampled may not be representative, and they provide little chemical bonding information with low contrast of light elements. With ceria nanocubes exposing (100) facets as an example, here we show that the polar surface structure of oxide nanocrystals can be investigated by applying 17O and 1H solid-state NMR spectroscopy and dynamic nuclear polarization, combined with DFT calculations. Both CeO4-termination reconstructions and hydroxyls are present for surface polarity compensation and their concentrations can be quantified. These results open up new possibilities for investigating the structure and properties of oxide nanostructures with polar facets.

Solid electrolytes are highly important materials for improving safety, energy density, and reversibility of electrochemical energy storage batteries. However, it is a challenge to modulate the coordination structure of conducting ions, which limits the improvement of ionic conductivity and hampers further development of practical solid electrolytes. Here, we present a skeleton-retained cationic exchange approach to produce a high-performance solid electrolyte of Li 3 Zr 2 Si 2 PO 12 stemming from the NASICON-type superionic conductor of Na 3 Zr 2 Si 2 PO 12 . The introduced lithium ions stabilized in under-coordination structures are facilitated to pass through relatively large conduction bottlenecks inherited from the Na 3 Zr 2 Si 2 PO 12 precursor. The synthesized Li 3 Zr 2 Si 2 PO 12 achieves a low activation energy of 0.21 eV and a high ionic conductivity of 3.59 mS cm −1 at room temperature. Li 3 Zr 2 Si 2 PO 12 not only inherits the satisfactory air survivability from Na 3 Zr 2 Si 2 PO 12 but also exhibits excellent cyclic stability and rate capability when applied to solid-state batteries. The present study opens an innovative avenue to regulate cationic occupancy and make new materials.

Investigation of LiOH decomposition in nonaqueous electrolytes not only expands the fundamental understanding of four-electron oxygen evolution reactions in aprotic media but also is crucial to the development of high-performance lithium−air batteries involving the formation/decomposition of LiOH. In this work, we have shown that the decomposition of LiOH by ruthenium metal catalysts in a wet DMSO electrolyte occurs at the catalyst−electrolyte interface, initiated via a potential-triggered dissolution/reprecipitation process. The in situ UV−vis methodology devised herein provides direct experimental evidence that the hydroxyl radical is a common reaction intermediate formed in several nonaqueous electrolytes; this method is applicable to study other battery systems. Our results highlight that the reactivity of the hydroxyl radical toward nonaqueous electrolyte represents a major factor limiting O 2 evolution during LiOH decomposition. Coupling catalysts restraining hydroxyl reactivity with electrolytes more resistant to hydroxyl radical attack could help improve the reversibility of this reaction.

Solid polymer electrolytes (SPEs), which are favorable to form intimate interfacial contacts with electrodes, are promising electrolyte of choice for long-cycling lithium metal batteries (LMBs). However, typical SPEs with easily oxidized oxygen-bearing polar groups exhibit narrow electrochemical stability window (ESW), making it impractical to increase specific capacity and energy density of SPE based LMBs with charging cut-off voltage of 4.5 V or higher. Here, we apply a polyfluorinated crosslinker to enhance oxidation resistance of SPEs. The crosslinked network facilitates transmission of the inductive electron-withdrawing effect of polyfluorinated segments. As a result, polyfluorinated crosslinked SPE exhibits a wide ESW, and the Li|SPE|LiNi0.5Co0.2Mn0.3O2 cell with a cutoff voltage of 4.5 V delivers a high discharge specific capacity of ~164.19 mAh g−1 at 0.5 C and capacity retention of ~90% after 200 cycles. This work opens a direction in developing SPEs for long-cycling high-voltage LMBs by using polyfluorinated crosslinking strategy.

Both atomic geometry and the influence of surroundings (e.g., exogenously coordinated water) are key issues for determining the chemical environment of oxide surfaces, whereas the latter is usually ignored and should be considered in future studies.

Recent advances in applying 17O solid-state NMR spectroscopy for catalytic oxides have provided valuable information on the surface structure, active sites, and reaction mechanisms. Here we present a short introduction to 17O solid-state NMR spectroscopy before discussing recent methodological developments related to its applications. After that, a brief review on the applications of 17O NMR for elucidating the structure of oxide catalysts and related mechanisms is given. Specifically, we focus on recent research results in the investigations of oxide nanomaterials and zeolites. Finally, some opinions on remaining challenges and future directions of this emerging field are provided.

Solid polymer electrolytes (SPEs), which are favorable to form intimate interfacial contacts with electrodes, are promising electrolyte of choice for long-cycling lithium metal batteries (LMBs). However, typical SPEs with easily oxidized oxygen-bearing polar groups exhibit narrow electrochemical stability window (ESW), making it impractical to increase specific capacity and energy density of SPE based LMBs with charging cut-off voltage of 4.5 V or higher. Here, a polyfluorinated crosslinker has been applied to enhance oxidation resistance of SPEs via inductive electron-withdrawing effect of polyfluorinated segments transmitted through crosslinked networks. As a result, polyfluorinated crosslinked SPE exhibits a wide ESW, and the Li|SPE|LiNi0.5Co0.2Mn0.3O2 cell with a cutoff voltage of 4.5 V delivers a high discharge specific capacity of ~ 164.19 mAh g− 1 at 0.5 C and capacity retention of ~ 90% after 200 cycles. This work opens a new direction in developing SPEs for long-cycling high-voltage LMBs by using polyfluorinated crosslinking strategy.

Inductive effect, although originally proposed in the field of organic chemistry, has long been regarded as an effective way to increase the working potential of inorganic lithium-ion battery cathodes. A classic example is the LiFePO 4 cathode, where introduction of the highly electronegative P 5+ raises the redox potential of Fe 3+ /Fe 2+ as in conventional oxides by 1.0 V. Recently, some of us have reported a substantially reduced redox potential of Ti 4+ /Ti 3+ in Li 2 TiSiO 5 compared with lithium titanium oxides, suggesting the presence of a reversed inductive effect imposed by polyanions (Energy Environ. Sci., 2017, 10, 1456−1464. In this work, through characterizing the electronic structure of pristine Li 2 TiSiO 5 and following the crystallographic structure evolution during lithium insertion in Li 2 TiSiO 5 , we propose that the reversed inductive effect is likely linked with the square-pyramid coordination of Ti. The reversed inductive effect offers new possibilities in tuning the potentials of anode materials, presenting a promising avenue to further increase the energy density of batteries based on polyanion electrodes.