ACS Materials Letters最新文献

The role of anharmonic effects on the phase stability of VNbMoTaW high-entropy alloy (HEA) is evaluated by extensive ab initio molecular dynamics simulations (AIMD) combined with the phonon quasiparticle theory. We find that the anharmonic effects have a positive effect on the phase stability of the HEAs. The study of subsystem alloys reveals that the strong interactions between W and Nb or Ta promote positive contributions of anharmonic effects. Further studies also reveal that the anharmonic effects are an important driving factor of the ordered B2(MoW, TaNb) phase transformation. These findings provide novel insights into the phase stability of HEAs.

The unbefitting binding energy for H*/OH* with Ni sites greatly restrains the electrochemical activity of Ni for the hydrogen evolution reaction (HER). Herein, Ni nanograins incorporated with trace Rh (denoted as 3D RhNi) are synthesized through combining a facile ion-absorption and subsequent thermal reduction treatment, in which Rh increases the local charge density of Ni sites, dramatically accelerating the electrochemical kinetics of HER. Experimentally, the Rh–Ni catalyst with only 0.1 at. % Rh element exhibits superior HER activity among the reported Ni-based materials, whose overpotential is only 37 mV and 18 mV at 10 mA/cm² in 1.0 M KOH and 0.5 M H₂SO₄, respectively. DFT calculations further identify that the resultant catalyst possesses appropriate intermediate binding energy in both acidic and alkaline conditions toward HER. This study provides a strategy to manipulate the local electronic structure for significantly improving the activity in surface catalysis.

Lithium garnet (Li₇La₃Zr₂O₁₂, LLZO) based solid electrolytes are leading candidate materials for all-solid-state batteries with lithium metal anodes because of their high ionic conductivity, high mechanical toughness, and superior electrochemical stability. While doping LLZO with Al and Ga increases its ionic conductivity by stabilizing the cubic phase, the impact of dopants on its (electro)chemical stability at the interfaces with Li metal is critical. Our study of differences between Al- and Ga-doped LLZO when interfaced with lithium metal using X-ray photoelectron spectroscopy and density functional theory shows a higher propensity of Ga to move across LLZO interface with Li metal and form Ga–Li alloy. Neutron diffraction reveals loss of cubic phase resulting from the loss of dopant that explains electrochemical behavior differences between Ga- and Al-doped LLZO. Overall, our study reveals the key role of dopant chemistry in enabling stable solid electrolyte materials for all-solid-state batteries.

Bipolar membranes (BPMs) enable isolated acidic/alkaline regions in electrochemical devices, facilitating optimized environments for electrochemical separations and catalysis. For economic viability, BPMs must attain stable, high current density operation with low overpotentials in a freestanding configuration. We report an asymmetric, graphene oxide (GrOx)-catalyzed BPM capable of freestanding electrodialysis operation at 1 A cm^–2 with overpotentials <250 mV. Use of a thin anion-exchange layer improves water transport while maintaining near unity Faradaic efficiency for acid and base generation. Voltage stability exceeding 1100 h with an average drift of 70 μV/h at 80 mA cm^–2 and 100 h with an average drift of −300 μV/h at 500 mA cm^–2 and implementation in an electrodialysis stack demonstrate real-world applicability. Continuum modeling reveals that water dissociation in GrOx BPMs is both catalyzed and electric-field enhanced, where low pK_a moieties on GrOx enhance local electric fields and high pK_a moieties serve as active sites for surface-catalyzed water dissociation. These results establish commercially viable BPM electrodialysis and provide fundamental insight to advance design of next-generation devices.

Advances in electrolyte chemistry and the development of electrolyte systems have revealed that electrolyte concentration significantly affects battery performance. However, the relationship between electrolyte concentration, polysulfide formation, and lithium–sulfur (Li–S) battery performance remains unclear, which hinders the developmental progress of practical Li–S batteries. In this study, we compared the electrolyte structures and performance of Li–S batteries with various electrolyte concentrations and developed a method that links microscopic interactions, apparent electrolyte parameters, and battery performance. The relationship between polysulfides and the electrolyte system was analyzed at various concentrations, which revealed that systems with a low lithium-salt concentration, especially below 1 M, are better suited to practical Li–S batteries and that polysulfides play crucial roles in ion-transport processes under practical conditions. This study supports the development of electrolytes for practical Li–S batteries and provides guidance for controlling ion-transport processes in liquid electrolytes for other secondary batteries.

Herein, we deliberately used substoichiometric amounts of lithium hydroxide for preparing layered Ni-rich oxide cathode materials with minor or even no residual lithium being present on the particle surface. This approach allows record capacities with LiNiO₂ to be achieved while using up to 7% less lithium and avoiding tedious postprocessing steps, thus facilitating synthesis and improving battery performance.

The field of CO₂ reduction has identified several challenges that must be overcome to realize its immense potential to simultaneously close the carbon cycle, replace fossil-based chemical feedstocks, and store renewable electricity. However, frequently cited research targets were set without quantitatively analyzing their impact on economic viability. Through a physics-informed techno-economic assessment, we offer guidance on top priorities for CO₂ reduction. Although separations dominate capital cost, increasing single-pass conversion is unnecessary because it leads to selectivity loss in current membrane electrode assemblies. Decoupling selectivity and single-pass conversion by moving away from a plug flow reactor design would reduce the base case levelized cost from $1.22/kg_CO to $0.97/kg_CO, as impactful as eliminating CO₂R overpotential. Operating at high current densities (>500 mA/cm²) is undesirable unless cell voltages can be lowered. We confirm that levelized product cost is dominated by the cost of electricity to drive electrolysis. Although wholesale wind and solar electricity are cheaper than retail electricity, their capacity factors are too low for economical operation. Adding energy storage to increase the capacity factor of solar electricity triples the capital cost of the process. By updating research priorities based on fundamental electrolyzer behavior, we hope this work accelerates the practical application of CO₂ reduction.

The efficiencies of dimer-based devices still lag those of their small molecule-based counterparts. This is primarily due to the considerable dihedrals in the dimer skeleton, which compromises the molecular packing, thus influencing the charge generation and nonradiative voltage loss (ΔV_oc,_nr). Herein, we developed two dimeric acceptors with varied π-linkers to investigate the influence of linker-induced conformational lock on ΔV_oc,_nr. We find that the helically lapped O-shaped dimer delivers better intermolecular packing than the planar S-shaped one that incorporates a bulkier π-linker. However, its planar skeleton is instead more favorable for forming a compact and ordered stacking with the host acceptor in ternary blend. This possibly promotes exciton dissociation, thus reducing the nonradiative decay of excited states. Moreover, its longer exciton lifetime could offer additional charge-transfer channels. These contributions effectively minimize ΔV_oc,_nr to 0.195 eV, while delivering a high efficiency approaching 20% in the derived ternary device.

Sulfide-based Li-argyrodites (Li_5.5PS_4.5Cl_1.5) are considered as promising solid-state electrolytes for all-solid-state Li–S batteries (ASSLSBs) due to their high ionic conductivity and suitable mechanical properties. However, their hygroscopic nature and intense decomposition behavior when combined with conductive additives at the sulfur cathode introduce many variables that can affect cell performance. This study demonstrates that an optimized amount of ambient air contamination during cycling can enhance cell performance. Multiple spectroscopic analyses reveal that the hydrolysis of Li_5.5PS_4.5Cl_1.5 can incorporate oxygen into the argyrodite structure, thereby increasing the oxidative stability and generating additional redox active sulfur species. Methods, such as monitoring cell impedance growth, open-circuit voltage changes, and ³¹P NMR spectroscopic analysis, are proposed to determine the air-tightness of cell configurations. The research findings suggest that verifying the air-tightness of cell configurations is critical for ASSLSBs research to prevent misleading results.