80 Search Results

Abstract Solid polymer electrolytes based on plastic crystals are promising for solid‐state sodium metal (Na ⁰ ) batteries, yet their practicality has been hindered by the notorious Na ⁰ ‐electrolyte interface instability issue, the underlying cause of which remains poorly understood. Here, by leveraging a model plasticized polymer electrolyte based on conventional succinonitrile plastic crystals, we uncover its failure origin in Na ⁰ batteries is associated with the formation of a thick and non‐uniform solid electrolyte interphase (SEI) and whiskery Na ⁰ nucleation/growth. Furthermore, we design a new additive‐embedded plasticized polymer electrolyte to manipulate the Na ⁰ deposition and SEImore » formulation. For the first time, we demonstrate that introducing fluoroethylene carbonate (FEC) additive into the succinonitrile‐plasticized polymer electrolyte can effectively protect Na ⁰ against interfacial corrosion by facilitating the growth of dome‐like Na ⁰ with thin, amorphous, and fluorine‐rich SEIs, thus enabling significantly improved performances of Na//Na symmetric cells (1,800 h at 0.5 mA cm ⁻² ) and Na//Na ₃ V ₂ (PO ₄ ) ₃ full cells (93.0 % capacity retention after 1,200 cycles at 1 C rate in coin cells and 93.1 % capacity retention after 250 cycles at C/3 in pouch cells at room temperature). Our work provides valuable insights into the interfacial failure of plasticized polymer electrolytes and offers a promising solution to resolving the interfacial instability issue.« less

Abstract Solid polymer electrolytes based on plastic crystals are promising for solid‐state sodium metal (Na ⁰ ) batteries, yet their practicality has been hindered by the notorious Na ⁰ ‐electrolyte interface instability issue, the underlying cause of which remains poorly understood. Here, by leveraging a model plasticized polymer electrolyte based on conventional succinonitrile plastic crystals, we uncover its failure origin in Na ⁰ batteries is associated with the formation of a thick and non‐uniform solid electrolyte interphase (SEI) and whiskery Na ⁰ nucleation/growth. Furthermore, we design a new additive‐embedded plasticized polymer electrolyte to manipulate the Na ⁰ deposition and SEImore » formulation. For the first time, we demonstrate that introducing fluoroethylene carbonate (FEC) additive into the succinonitrile‐plasticized polymer electrolyte can effectively protect Na ⁰ against interfacial corrosion by facilitating the growth of dome‐like Na ⁰ with thin, amorphous, and fluorine‐rich SEIs, thus enabling significantly improved performances of Na//Na symmetric cells (1,800 h at 0.5 mA cm ⁻² ) and Na//Na ₃ V ₂ (PO ₄ ) ₃ full cells (93.0 % capacity retention after 1,200 cycles at 1 C rate in coin cells and 93.1 % capacity retention after 250 cycles at C/3 in pouch cells at room temperature). Our work provides valuable insights into the interfacial failure of plasticized polymer electrolytes and offers a promising solution to resolving the interfacial instability issue.« less

We propose a universal solid electrolyte design that broadens the selection of ceramic LICs for solid-state lithium metal batteries, without requirements of electronic insulation or (electro)chemical stability.

Single Li⁺ ion conducting polyelectrolytes (SICs), which feature covalently tethered counter-anions along their backbone, have the potential to mitigate dendrite formation by reducing concentration polarization and preventing salt depletion. However, due to their low ionic conductivity and complicated synthetic procedure, the successful validation of these claimed advantages in lithium metal (Li⁰) anode batteries remains limited. In this study, we fabricated a SIC electrolyte using a single-step UV polymerization approach. The resulting electrolyte exhibited a high Li⁺ transference number (t₊) of 0.85 and demonstrated good Li⁺ conductivity (6.3×10^-5 S/cm at room temperature), which is comparable to that of a benchmark dualmore » ion conductor (DIC, 9.1×10^-5 S/cm). Benefitting from the high transference number of SIC, it displayed a three-fold higher critical current density (2.4 mA/cm²) compared to DIC (0.8 mA/cm²) by successfully suppressing concentration polarization-induced short-circuiting. Additionally, the t₊ significantly influenced the deposition behavior of Li⁰, with SIC yielding a uniform, compact, and mosaic-like morphology, while the low t₊ DIC resulted in a porous morphology with Li⁰ whiskers. In conclusion, using the SIC electrolyte, Li⁰||LiFePO₄ cells exhibited stable operation for 4500 cycles with 70.5 % capacity retention at 22 °C.« less

Single Li⁺ ion conducting polyelectrolytes (SICs), which feature covalently tethered counter-anions along their backbone, have the potential to mitigate dendrite formation by reducing concentration polarization and preventing salt depletion. However, due to their low ionic conductivity and complicated synthetic procedure, the successful validation of these claimed advantages in lithium metal (Li⁰) anode batteries remains limited. In this study, we fabricated a SIC electrolyte using a single-step UV polymerization approach. The resulting electrolyte exhibited a high Li⁺ transference number (t₊) of 0.85 and demonstrated good Li⁺ conductivity (6.3×10^-5 S/cm at room temperature), which is comparable to that of a benchmark dualmore » ion conductor (DIC, 9.1×10^-5 S/cm). Benefitting from the high transference number of SIC, it displayed a three-fold higher critical current density (2.4 mA/cm²) compared to DIC (0.8 mA/cm²) by successfully suppressing concentration polarization-induced short-circuiting. Additionally, the t₊ significantly influenced the deposition behavior of Li0, with SIC yielding a uniform, compact, and mosaic-like morphology, while the low t₊ DIC resulted in a porous morphology with Li⁰ whiskers. Using the SIC electrolyte, Li⁰||LiFePO₄ cells exhibited stable operation for 4500 cycles with 70.5 % capacity retention at 22 °C.« less

The increasing demand for lithium-ion battery-powered electric vehicles (EVs) has led to a surge in recent prices of strategic battery materials such as cobalt (Co) and nickel (Ni). While all EV makers are eager to eliminate Co usage, Ni has rapidly become another ‘pain point’ for the industry, as its price is nearing half that of Co. The sustainability issue facing both Ni and Co puts forward a grand materials challenge, that is, to reduce Ni content and eliminate Co while maintaining high specific energy and stability. Here in this work, a complex concentrated doping strategy is used to eliminatemore » Co in a commercial NMC-532 cathode. The LiNi_0.5Mn_0.43Ti_0.02Mg_0.02Nb_0.01Mo_0.02O₂ cathode shows potential cost advantage with relatively high specific energy and significantly improved overall performance (~95% capacity retained after 1,000 cycles in pouch-type cells, 2.8–4.3 V vs graphite, at 1 C, 1.5 mA cm^-2). Combining X-ray techniques and electron microscopy, we uncover the origins of the superior stability.« less

High-Ni-content layered materials are promising cathodes for next-generation lithium-ion batteries. However, investigating the atomic configurations of the delithiation-induced complex phase boundaries and their transitions remains challenging. Here, in this study, by using deep-learning-aided super-resolution electron microscopy, we resolve the intralayer transition motifs at complex phase boundaries in high-Ni cathodes. We reveal that an O3 → O1 transformation driven by delithiation leads to the formation of two types of O1–O3 interface, the continuous- and abrupt-transition interfaces. The interfacial misfit is accommodated by a continuous shear-transition zone and an abrupt structural unit, respectively. Atomic-scale simulations show that uneven in-plane Li+ distribution contributesmore » to the formation of both types of interface, and the abrupt transition is energetically more favourable in a delithiated state where O1 is dominant, or when there is an uneven in-plane Li⁺ distribution in a delithiated O3 lattice. Moreover, a twin-like motif that introduces structural units analogous to the abrupt-type O1–O3 interface is also uncovered. The structural transition motifs resolved in this study provide further understanding of shear-induced phase transformations and phase boundaries in high-Ni layered cathodes.« less

Abstract The electrochemical nitrogen (N ₂ ) reduction reaction (N ₂ RR) under mild conditions is a promising and environmentally friendly alternative to the traditional Haber‐Bosch process with high energy consumption and greenhouse emission for the synthesis of ammonia (NH ₃ ), but high‐yielding production is rendered challenging by the strong nonpolar N≡N bond in N ₂ molecules, which hinders their dissociation or activation. In this study, disordered Au nanoclusters anchored on two‐dimensional ultrathin Ti ₃ C ₂ T _x MXene nanosheets are explored as highly active and selective electrocatalysts for efficient N ₂ ‐to‐NH ₃ conversion, exhibitingmore » exceptional activity with an NH ₃ yield rate of 88.3±1.7 μg h ⁻¹  mg _cat. ⁻¹ and a faradaic efficiency of 9.3±0.4 %. A combination of in situ near‐ambient pressure X‐ray photoelectron spectroscopy and operando X‐ray absorption fine structure spectroscopy is employed to unveil the uniqueness of this catalyst for N ₂ RR. The disordered structure is found to serve as the active site for N ₂ chemisorption and activation during the N ₂ RR process.« less

Not provided.

Interfacial segregation and chemical short-range ordering influence the behavior of grain boundaries in complex concentrated alloys. In this study, we use atomistic modeling of a NbMoTaW refractory complex concentrated alloy to provide insight into the interplay between these two phenomena. Hybrid Monte Carlo and molecular dynamics simulations are performed on columnar grain models to identify equilibrium grain boundary structures. Here our results reveal extended near-boundary segregation zones that are much larger than traditional segregation regions, which also exhibit chemical patterning that bridges the interfacial and grain interior regions. Furthermore, structural transitions pertaining to an A2-to-B2 transformation are observed within thesemore » extended segregation zones. Both grain size and temperature are found to significantly alter the widths of these regions. An analysis of chemical short-range order indicates that not all pairwise elemental interactions are affected by the presence of a grain boundary equally, as only a subset of elemental clustering types are more likely to reside near certain boundaries. The results emphasize the increased chemical complexity that is associated with near-boundary segregation zones and demonstrate the unique nature of interfacial segregation in complex concentrated alloys.« less