High-energy Li-rich layered cathode materials (≈900 Wh kg
) suffer from severe capacity and voltage decay during cycling, which is associated with layered-to-spinel phase transition and oxygen redox ...reaction. Current efforts mainly focus on surface modification to suppress this unwanted structural transformation. However, the true challenge probably originates from the continuous oxygen release upon charging. Here, the usage of dielectric polarization in surface coating to suppress the oxygen evolution of Li-rich material is reported, using Mg
TiO
as a proof-of-concept material. The creation of a reverse electric field in surface layers effectively restrains the outward migration of bulk oxygen anions. Meanwhile, high oxygen-affinity elements of Mg and Ti well stabilize the surface oxygen of Li-rich material via enhancing the energy barrier for oxygen release reaction, verified by density functional theory simulation. Benefited from these, the modified Li-rich electrode exhibits an impressive cyclability with a high capacity retention of ≈81% even after 700 cycles at 2 C (≈0.5 A g
), far superior to ≈44% of the unmodified counterpart. In addition, Mg
TiO
coating greatly mitigates the voltage decay of Li-rich material with the degradation rate reduced by ≈65%. This work proposes new insights into manipulating surface chemistry of electrode materials to control oxygen activity for high-energy-density rechargeable batteries.
Thermal safety issues of batteries have hindered their large‐scale applications. Nonflammable electrolytes improved safety but solvent evaporation above 100 °C limited thermal tolerance, lacking ...reliability. Herein, fire‐tolerant metal‐air batteries were realized by introducing solute‐in‐air electrolytes whose hygroscopic solutes could spontaneously reabsorb the evaporated water solvent. Using Zn/CaCl2‐in‐air/carbon batteries as a proof‐of‐concept, they failed upon burning at 631.8 °C but self‐recovered then by reabsorbing water from the air at room temperature. Different from conventional aqueous electrolytes whose irreversible thermal transformation is determined by the boiling points of solvents, solute‐in‐air electrolytes make this transformation determined by the much higher decomposition temperature of solutes. It was found that stronger intramolecular bonds instead of intermolecular (van der Waals) interactions were strongly correlated to ultra‐high tolerance temperatures of our solute‐in‐air electrolytes, inspiring a concept of non‐van der Waals electrolytes. Our study would improve the understanding of the thermal properties of electrolytes, guide the design of solute‐in‐air electrolytes, and enhance battery safety.
While the irreversible thermal transformation of electrolytes is typically attributed to solvent boiling, which disrupts solvent intermolecular interactions, our research revealed that hygroscopic solutes shift the determining factor to solute decomposition, breaking solute intramolecular bonds. As intramolecular bonds are much stronger, it enables ultrahigh thermal tolerance of non‐van der Waals solute‐in‐air electrolytes.
Solute‐in‐air electrolytes are applied in metal‐air batteries, introducing dual‐air batteries for intrinsic safe energy storage. In their Research Article (e202318369), Xiaodong Chen and co‐workers ...demonstrate that fire‐tolerant batteries are achieved, and reveal that the highest tolerance temperature of electrolytes is determined by solute intramolecular bonds instead of solvent intermolecular interactions, inspiring a concept of non‐van der Waals electrolytes for their thermal stability.
Morphologies frequently play a critical role in determining the properties of nanomaterials. In current researches, we successfully synthesized varieties of SnO
2
nanostructures from 1D to 3D via a ...facile hydrothermal method. The as-obtained samples were characterized by X-ray diffraction and scanning electron microscopy. Then the plausible growth mechanism are proposed in detail. Furthermore, PEG and CO(NH
2
)
2
may have an effect on the formation of 1D and 2D nanostructures of SnO
2
as aggregation and template, respectively. The gas sensing properties of SnO
2
nanostructures from 1D to 3D toward ethanol were investigated. Surprisingly, we noticed that SnO
2
nanosheets show the highest gas sensing response while the nanospheres is opposite, which provided a substantial promising candidate of gas sensors and further indicated that gas sensing properties can be enhanced by tailoring the morphologies of nanomaterials in practical application.
Layered ternary oxides LiNixMnyCozO2 are promising cathode candidates for high‐energy lithium‐ion batteries (LIBs), but they usually suffer from the severe interfacial parasitic reactions at voltages ...above 4.3 V versus Li+/Li, which greatly limit their practical capacities. Herein, using LiNi1/3Mn1/3Co1/3O2 (NMC111) as the model system, a novel high‐temperature pre‐cycling strategy is proposed to realize its stable cycling in 3.0−4.5 V by constructing a robust cathode/electrolyte interphase (CEI). Specifically, performing the first five cycles of NMC111 at 55 °C helps to yield a uniform CEI layer enriched with fluorine‐containing species, Li2CO3 and poly(CO3), which greatly suppresses the detrimental side reactions during extended cycling at 25 °C, endowing the cell with a capacity retention of 92.3% at 1C after 300 cycles, far surpassing 62.0% for the control sample without the thermally tailored CEI. This work highlights the critical role of temperature on manipulating the interfacial properties of cathode materials, opening a new avenue for developing high‐voltage cathodes for Li‐ion batteries.
Performing a high‐temperature pre‐cycling process for the LiNixMnyCozO2 (NMC) cathode materials helps to yield a uniform and robust cathode/electrolyte interphase, which could suppress parasitic interfacial reactions in subsequent cycling, enabling Li‐ion battery operation in high voltage conditions with good cyclic stability.
A new strategy for incorporating oxygen vacancies into electrodes under aerobic conditions is realized by Shuzhou Li, Xiaodong Chen, and co‐workers, as described in article number 1906156, by ...applying interfacial lattice strain via surface coating, using TiO2(B) as a model system. The obtained oxygen‐deficient electrode exhibits an impressively high level of capacitive charge storage and significantly enhanced rate capability.
Oxygen vacancies play crucial roles in defining physical and chemical properties of materials to enhance the performances in electronics, solar cells, catalysis, sensors, and energy conversion and ...storage. Conventional approaches to incorporate oxygen defects mainly rely on reducing the oxygen partial pressure for the removal of product to change the equilibrium position. However, directly affecting reactants to shift the reaction toward generating oxygen vacancies is lacking and to fill this blank in synthetic methodology is very challenging. Here, a strategy is demonstrated to create oxygen vacancies through making the reaction energetically more favorable via applying interfacial strain on reactants by coating, using TiO
(B) as a model system. Geometrical phase analysis and density functional theory simulations verify that the formation energy of oxygen vacancies is largely decreased under external strain. Benefiting from these, the obtained oxygen-deficient TiO
(B) exhibits impressively high level of capacitive charge storage, e.g., ≈53% at 0.5 mV s
, far surpassing the ≈31% of the unmodified counterpart. Meanwhile, the modified electrode shows significantly enhanced rate capability delivering a capacity of 112 mAh g
at 20 C (≈6.7 A g
), ≈30% higher than air-annealed TiO
and comparable to vacuum-calcined TiO
. This work heralds a new paradigm of mechanical manipulation of materials through interfacial control for rational defect engineering.
Abstract
Molybdenum disulfide (MoS
2
) is a promising high‐capacity anode for lithium‐ion batteries. However, the conversion reaction mechanism of MoS
2
(the delithiation pathway in particular) has ...been controversial, which limits the rational optimization of its electrochemical performance. The main challenge is how to precisely identify the amorphous nanomaterials generated during lithiation/delithiation. Here, the structural evolutions of MoS
2
during lithiation/delithiation are systematically investigated using synchrotron X‐ray absorption spectroscopy at Mo K‐edge and S K‐edge and Raman spectroscopy. It is revealed that amorphous MoS
2
nanograins rather than sulfur as previously suggested, are formed after delithiation, and that the fully lithiated MoS
2
electrode contains additional Mo‐S related phases besides the known Mo and Li
2
S. Density functional theory simulations suggest that the Mo nanoparticles formed during lithiation are very reactive with Li
2
S, thus enabling the regeneration of MoS
2
upon delithiation. These findings deepen the understanding of the lithiation/delithiation mechanism of MoS
2
, which will pave the way for the rational design of advanced MoS
2
‐based electrodes.
Inside Back Cover
In article number 2100920, Xiaodong Chen and co‐workers propose a novel high‐temperature pre‐cycling approach to construct in‐situ a uniform and robust cathode/electrolyte ...interphase on LiNixMnyCozO2 cathode materials, which helps to suppress parasitic interfacial reactions in subsequent cycling and thus enables Li‐ion battery operation in high voltage conditions with good cyclic stability.
PDF
