Superior sodiophilicity and molecule crowding of crown ether boost the electrochemical performance of all-climate sodium-ion batteries.

Sodium-ion batteries (SIBs) as one of the promising alternatives to lithium-ion batteries have achieved remarkable progress in the past. However, the all-climate performance is still very challenging for SIBs. Herein, 15-Crown-5 (15-C-5) is screened as an electrolyte additive from a number of ether molecules theoretically. The good sodiophilicity, high molecule rigidity, and bulky size enable it to reshape the solvation sheath and promote the anion engagement in the solvated structures by molecule crowding. This change also enhances Na-ion transfer, inhibits side reactions, and leads to a thin and robust solid-electrolyte interphase. Furthermore, the electrochemical stability and operating temperature windows of the electrolyte are extended. These profits improve the electrochemical performance of SIBs in all climates, much better than the case without 15-C-5. This improvement is also adopted to µ-Sn, µ-Bi, hard carbon, and MoS2. This work opens a door to prioritize the potential molecules in theory for advanced electrolytes.

Site-Selective Adsorption on ZnF2/Ag Coated Zn for Advanced Aqueous Zinc-Metal Batteries at Low Temperature.

Metallic Zn as a promising anode material of aqueous batteries suffers from severe parasitic reactions and notorious dendrite growth. To address these issues, the desolvation and nucleation processes need to be carefully regulated. Herein, Zn foils coated by ZnF2-Ag nanoparticles (ZnF2-Ag@Zn) are used as a model to modulate the desolvation and nucleation processes by hybrid surfaces, where Ag has a strong affinity to Zn adatoms and ZnF2 shows an intense adsorption to H2O. This selective adsorption of different species on ZnF2 and Ag reduces the mutual interference between two species. Therefore, ZnF2-Ag@Zn exhibits the electrochemical performance much better than ZnF2@Zn or Ag@Zn. Even at -40 °C, the full cells using ZnF2-Ag@Zn demonstrate an ultralong lifespan of 5000 cycles with a capacity retention of almost 100%. This work provides new insights to improve the performance of Zn metal batteries, especially at low temperatures.

Microsized Gray Tin as a High-Rate and Long-Life Anode Material for Advanced Sodium-Ion Batteries.

Sodium-ion batteries (SIBs) are developed to address the serious concern about the limited resources of lithium. To achieve high energy density, anode materials with a large specific capacity and a low operation voltage are highly desirable. Herein, microsized particles of gray Sn (α-Sn) are explored as an anode material of SIBs for the first time. The distinct structure of α-Sn endows it the reduced volume change, the improved interaction with polymer binders and the in situ formation of amorphous Sn, as supported by in situ XRD, TEM and DFT calculations. Therefore, α-Sn exhibits an excellent electrochemical performance, much better than ß-Sn widely used before. Even microsized particles of α-Sn without any treatments deliver a capacity of ∼451 mAh g-1 after 3500 cycles at 2 A g-1 or ∼464 mAh g-1 at 4 A g-1 in a rate test. The results indicate the promising potential of α-Sn in SIBs.

Integrating Chemical Pre-Potassiation with Pre-Modulated KF-Rich Electrolyte Interfaces for Dual-Carbon Potassium Ion Hybrid Capacitor.

Herein, a chemical pre-potassiation strategy via simultaneously treating both glucose derived carbon (GDC) anode and commercial activated carbon (CAC) cathode in potassium-naphthalene-tetrahydrofuran solution is developed for potassium ion hybrid capacitor (PIHC). Combined with in situ and ex situ characterizations, a radical reaction between pre-potassiation reagent and carbon electrodes is confirmed, which not only deactivates electrochemical irreversible sites, but also promotes to pre-form a uniform and dense KF-rich electrolyte film on the electrodes. As a result, the pre-potassiation treatment presents multiple advantages: (I) the initial Coulombic efficiency (CE) of the GDC anode increases from 45.4 % to 84.0 % with higher rate capability; (II) the CAC cathode exhibits the improved cycling CEs and stability due to the enhanced resistance to electrolyte oxidation at 4.2 V; (III) the assembled PIHC achieves a high energy density of 172.5 Wh kg-1 with cycling life over 10000 cycles.

Solvation Modulation Enhances Anion-Derived Solid Electrolyte Interphase for Deep Cycling of Aqueous Zinc Metal Batteries.

Stable Zn anodes with a high utilization efficiency pose a challenge due to notorious dendrite growth and severe side reactions. Therefore, electrolyte additives are developed to address these issues. However, the additives are always consumed by the electrochemical reactions over cycling, affecting the cycling stability. Here, hexamethylphosphoric triamide (HMPA) is reported as an electrolyte additive for achieving stable cycling of Zn anodes. HMPA reshapes the solvation structures and promotes anion decomposition, leading to the in situ formation of inorganic-rich solid-electrolyte-interphase. More interestingly, this anion decomposition does not involve HMPA, preserving its long-term impact on the electrolyte. Thus, the symmetric cells with HMPA in the electrolyte survive ≈500 h at 10 mA cm-2 for 10 mAh cm-2 or ≈200 h at 40 mA cm-2 for 10 mAh cm-2 with a Zn utilization rate of 85.6 %. The full cells of Zn||V2 O5 exhibit a record-high cumulative capacity even under a lean electrolyte condition (E/C ratio=12 µL mAh-1 ), a limited Zn supply (N/P ratio=1.8) and a high areal capacity (6.6 mAh cm-2 ).

Cation-Dependent Hydrogel Template-Activation Strategy: Constructing 3D Anode and High Specific Surface Cathode for Dual-Carbon Potassium-Ion Hybrid Capacitor.

Here, a universal template-activation strategy is proposed to prepare two different types of porous carbonaceous materials for potassium ion hybrid capacitor (PIHC) anode and cathode, which is realized by only changing the type of cation (Na+ and K+ ) in the polysilicic acid-organic mixed hydrogel precursor originating from adding organic acid into Na2 SiO3 and K2 SiO3 solution, respectively. TG-IR data demonstrate that K+ exhibits a stronger etching ability for activating carbonaceous materials during the annealing process. Accordingly, a 3D carbon anode obtained with the assistance of NaOH (NPC-500) exhibits abundant edge-N doping (8.14 at%), displaying a high K-storage capacity of 314.1 mA h g-1 at 0.2 A g-1 and a capacity of 219.3 mA h g-1 at 10 A g-1 after 10000 cycles. A porous carbon particles cathode prepared in the presence of KOH (KCP-800) shows a high specific surface area (1326.8 m2 g-1 ), contributing to high PF6- (de)adsorb capacity of 103.0 mA h g-1 at 1 A g-1 . Remarkably, the assembled NPC//KCP PIHC delivers a high energy density of 137.7 W h kg-1 at a power density of 275.4 W kg-1 even over 20 000 cycles.

Constructing Reactive Micro-Environment in Basal Plane of MoS2 for pH-Universal Hydrogen Evolution Catalysis.

MoS2 represents a promising catalyst for the hydrogen evolution reaction (HER) in water splitting, but the inefficient catalytic activity in a pH-universal environment is an obstacle to developing practical applications. Boosting and balancing the water dissociation and hydrogen desorption kinetics is crucial in designing high-performance catalysts for the overall pH range. Herein, it is experimentally demonstrated that cobalt single-atom doping can effectively construct a reactive CoMoS micro-environment on the basal plane of MoS2 and thus alter the uniformity of surface electron density, which is further confirmed by the theoretical results. The reactive micro-environment consisting of single-atom Co with the surrounding Mo and S atoms possesses excellent water dissociation and hydrogen desorption kinetics, exhibiting a superior performance of 36 mV at 10 mA cm-2 with a Tafel slope of 33 mV dec-1 in the alkaline condition. Meanwhile, it also shows worthy activity in the acidic (97 mV) and neutral (117 mV) environments. This work provides a facile strategy to improve the HER catalysis of MoS2 in pH-universal environments.

Rational Design of Tungsten Selenide @ N-Doped Carbon Nanotube for High-Stable Potassium-Ion Batteries.

Potassium-ion batteries (PIBs) are deemed as one of the most promising energy storage systems due to their high energy density and low cost. However, their commercial application is far away from satisfactory because of limited suitable electrode materials. Herein, core-shell structured WSe2 @N-doped C nanotubes are rationally designed and synthesized via selenizing WO3 @ polypyrrole for the first time. The large interlayer spacing of WSe2 can facilitate the intercalation/deintercalation of K+ . Meanwhile, the core-shell structured nanotube provides favorable interior void space to accommodate the volume expansion of WSe2 during cycling. Thus, the obtained electrode exhibits superb electrochemical performance with a high capacity of 301.7 mAh g-1 at 100 mA g-1 over 120 cycles, and 122.1 mAh g-1 can remain at 500 mA g-1 even after 1300 cycles. Ex-situ X-ray diffraction analysis reveals the K-ion storage mechanism of WSe2 @N-doped C includes intercalation and conversion reaction. Density function theory (DFT) calculation demonstrates the reasonable diffusion pathway of K+ . In addition, the obtained WSe2 @N-doped C nanotubes have been used as anode material for lithium-ion batteries, which also show good rate performance and high cycle stability. Therefore, this work offers a new methodology for the ration design of new structure electrode materials with long cycle stability.

Chemical Buffer Layer Enabled Highly Reversible Zn Anode for Deeply Discharging and Long-Life Zn-Air Battery.

Rechargeable alkaline Zn-air batteries (ZABs) are attracting extensive attention owing to their high energy density and environmental friendliness. However, the dilemma of Zn anode, composed of ineluctable passivation and dissolution problems, severely hinders the discharge and cycling performance of the battery. Herein, the authors propose a chemical buffer layer coated on Zn metal (CBL@Zn) anode, in which ZnO nanorods are uniformly dispersed in graphene oxide (GO), to improve the reversibility of Zn↔ZnO electrochemical conversion process. Benefiting from the cooperative effect of ZnO nanorods' nuclei role and GO's adsorption affinity, the electrochemical precipitation-dissolution behavior of insulated ZnO is chemically regulated and the Zn(OH)4 2- ions are effectively confined in the chemical buffer layer. Therefore, the symmetrical CBL@Zn-CBL@Zn coin cell achieves a superior stability of 100 cycles with quite low overpotential (30 mv). When paired with commercial catalysts to assemble alkaline ZABs for practical use, an ultra high depth of discharge (DODZn ) >98% and excellent 450-h long-term cycling performance are realized. This chemical buffer strategy can potentially provide a new insight for developing other highly reversible alkaline Zn-metal batteries.

Synergistic Chaotropic Effect and Cathode Interface Thermal Release Effect Enabling Ultralow Temperature Aqueous Zinc Battery.

Although rechargeable zinc-ion batteries are promising candidates for next-generation energy storage devices, their inferior performance at subzero temperatures limits their practical application. Here, a strategy to destroy the H-bond network by adding synergistic chaotropic regents is reported, thus reducing the freezing point of the aqueous electrolyte below -90 °C. Owing to the synergistic chaotropic effect between urea and Zn(ClO4 )2 and the thermal release effect on the cathode interface during charging, Zn//VO2 batteries feature a specific capacity of 111.4 mAh g-1 and stability after ≈1000 cycles with 81.9% capacity retention at -40 °C. This work demonstrates that the synergistic chaotropic effect and the thermal effect on the interface can effectively widen the operation range of temperature of aqueous electrolytes and maintain fast kinetics, which provides a new design strategy for all-weather aqueous zinc batteries.

Iron Selenide-Based Heterojunction Construction and Defect Engineering for Fast Potassium/Sodium-Ion Storage.

Suitable anode materials with high capacity and long cycling stability, especially capability at high current densities, are urgently needed to advance the development of potassium ion batteries (PIBs) and sodium ion batteries (SIBs). Herein, a porous Ni-doped FeSe2 /Fe3 Se4 heterojunction encapsulated in Se-doped carbon (NF11 S/C) is designed through selenization of MOFs precursor. The porous composite possesses enriched active sites and facilitates transport for both ion and electron. Ni-doping is adopted to enrich the lattice defects and active sites. The Se-C bond and carbon framework endow integrity of the composite and hamper aggregation of selenide nano-particles during potassiation/de-potassiation. The NF11 S/C exhibits exceptional rate performance and ultra-long cycling stability (177.3 mA h g-1 after 3050 cycles at 2 A g-1 for PIBs and 208.8 mA h g-1 after 2000 cycles at 8 A g-1 for SIBs). The potassiation/de-potassiation mechanism is investigated via ex-situ X-ray powder diffraction, high-resolution transmission electron microscopy, X-ray photoelectron spectrocopy and Raman analysis. PTCDA//NF11 S/C full cell stably cycles for 1200 cycles at 200 mA g-1 with a capacity of 103.7 mA h g-1 , indicating the high application potential of the electrode for highly stable rechargeable batteries.

In Situ Formation of Nitrogen-Rich Solid Electrolyte Interphase and Simultaneous Regulating Solvation Structures for Advanced Zn Metal Batteries.

Zn metal as one of promising anode materials for aqueous batteries suffers from notorious dendrite growth, serious Zn corrosion and hydrogen evolution. Here, a bifunctional electrolyte additive, N-methyl pyrrolidone (NMP), is developed to improve the electrochemical performance of Zn anode. NMP not only alters the solvation structure of Zn2+ , but also in situ produces a dense N-rich solid-electrolyte-interphase layer on Zn foils. This layer protects Zn foils from corrosive electrolytes and benefits the uniform plating/stripping of Zn. Hence, the asymmetrical cells with NMP in the electrolyte retain a high coulombic efficiency of 99.8 % over 1000 cycles. The symmetric cells survive ≈200 h for 10 mAh cm-2 at a high Zn utilization of 85.6 %. The full cells of Zn||MnO2 show an impressive cumulative capacity even with lean electrolyte (E/C ratio=10 µL mAh-1 ), limited Zn supply (N/P ratio=2.3) and high areal capacity (5.0 mAh cm-2 ).

Regulating Surface Reaction Kinetics through Ligand Field Effects for Fast and Reversible Aqueous Zinc Batteries.

Designing water-deficient solvation sheath of Zn2+ by ligand substitution is a widely used strategy to protect Zn metal anode, yet the intrinsic tradeoff between Zn nucleation/dissolution kinetics and the side hydrogen evolution reaction (HER) remains a huge challenge. Herein, we find boric acid (BA) with moderate ligand field interaction can partially replace H2 O molecules in the solvation sheath of Zn2+ , forming a stable water-deficient solvation sheath. It enables fast Zn nucleation/dissolution kinetics and substantially suppressed HER. Crucially, by systematically comparing the ligand field strength and solvation energies between BA and the ever-reported electrolyte additives, we also find that the solvation energy has a strong correlation with Zn nucleation/dissolution kinetics and HER inhibition ability, displaying a classic volcano behavior. The modulation map could provide valuable insights for solvation sheath design of zinc batteries and beyond.

Boosting Zinc-Ion Storage Capability by Effectively Suppressing Vanadium Dissolution Based on Robust Layered Barium Vanadate.

Vanadium-based compounds with an open framework structure have become the subject of much recent investigation into aqueous zinc-ion batteries (AZIBs) due to high specific capacity. However, there are some issues with vanadium dissolution from a cathode framework as well as the generation of byproducts during discharge that should not be ignored, which could cause severe capacity deterioration and inadequate cycle life. Herein, we report several barium vanadate nanobelt cathodes constructed of two sorts of architectures, i.e., Ba1.2V6O16·3H2O and BaV6O16·3H2O (V3O8-type) and BaxV2O5·nH2O (V2O5-type), which are controllably synthesized by tuning the amount of barium precursor. Benefiting from the robust architecture, layered BaxV3O8-type nanobelts (Ba1.2V6O16·3H2O) exhibit superior rate capability and long-term cyclability owing to fast zinc-ion kinetics, enabled by efficiently suppressing cathode dissolution as well as greatly eliminating the generation of byproduct Zn4SO4(OH)6·xH2O, which provides a reasonable strategy to engineer cathode materials with robust architectures to improve the electrochemical performance of AZIBs.

Nanoribbon Superstructures of Graphene Nanocages for Efficient Electrocatalytic Hydrogen Evolution.

Two-dimensional carbon architectures are attracting tremendous interests for various promising applications due to their outstanding electronic and mechanical properties, although it is a great challenge to rationally devise facile and operative methodologies to engineer their structural traits owing to complex synthetic processes. Herein, for the first time, we fabricate two-dimensional carbon nanoribbons via direct thermal exfoliation of one-dimensional Ni-based metal-organic framework (MOF) nanorods, in which interconnected graphitic carbon nanocages are self-assembled into a belt-like superstructure with carbon-encapsulated Ni nanoparticles immobilized on the surface. Due to the unparalleled structural superiority, the MOF-derived carbon nanobelts exhibit excellent catalytic performances in electrocatalytic hydrogen evolution. Importantly, the practical synthetic strategy may trigger the rapid development of carbon-based superstructures in many frontier fields.

Aqueous Rechargeable Li+ /Na+ Hybrid Ion Battery with High Energy Density and Long Cycle Life.

The practical application of aqueous rechargeable batteries is hampered by the low energy density and poor cycle stability, which mostly arises from the corrosion of cathode current collector, exfoliation of active material, and narrow electrochemical stability window of aqueous electrolyte. A light-weight and low-cost cathode current collector composed of graphite and carbon nanotube coated on nylon membrane exhibiting corrosion resistance and strong adhesion is developed. Also, a modified aqueous electrolyte with the addition of urea whose window is expanded to ≈3.2 V is developed that contributes to the formation of solid-electrolyte interphase on surfaces of electrodes. LiMn2 O4 /NaTi2 (PO4 )3 Li+ /Na+ hybrid ion battery using such aqueous electrolyte and current collector is demonstrated to cycle up to 10 000 times with low cost (60 dollars per kWh) and high energy density (100 Wh kg-1 ) for stationary energy storage and electronic vehicles applications.

A High-Energy and Long-Life Aqueous Zn/Birnessite Battery via Reversible Water and Zn2+ Coinsertion.

Aqueous rechargeable Zn/birnessite batteries have recently attracted extensive attention for energy storage system because of their low cost and high safety. However, the reaction mechanism of the birnessite cathode in aqueous electrolytes and the cathode structure degradation mechanics still remain elusive and controversial. In this work, it is found that solvation water molecules coordinated to Zn2+ are coinserted into birnessite lattice structure contributing to Zn2+ diffusion. However, the birnessite will suffer from hydroxylation and Mn dissolution with too much solvated water coinsertion. Through engineering Zn2+ primary solvation sheath with strong-field ligand in aqueous electrolyte, highly reversible [Zn(H2 O)2 ]2+ complex intercalation/extraction into/from birnessite cathode is obtained. Cathode-electrolyte interface suppressing the Mn dissolution also forms. The Zn metal anode also shows high reversibility without formation of "death-zinc" and detrimental dendrite. A full cell coupled with birnessite cathode and Zn metal anode delivers a discharge capacity of 270 mAh g-1 , a high energy density of 280 Wh kg-1 (based on total mass of cathode and anode active materials), and capacity retention of 90% over 5000 cycles.

Amidation-Dominated Re-Assembly Strategy for Single-Atom Design/Nano-Engineering: Constructing Ni/S/C Nanotubes with Fast and Stable K-Storage.

An amidation-dominated re-assembly strategy is developed to prepare uniform single atom Ni/S/C nanotubes. In this re-assembly process, a single-atom design and nano-structured engineering are realized simultaneously. Both the NiO5 single-atom active centers and nanotube framework endow the Ni/S/C ternary composite with accelerated reaction kinetics for potassium-ion storage. Theoretical calculations and electrochemical studies prove that the atomically dispersed Ni could enhance the convention kinetics and decrease the decomposition energy barrier of the chemically-absorbed small-molecule sulfur in Ni/S/C nanotubes, thus lowering the electrode reaction overpotential and resistance remarkably. The mechanically stable nanotube framework could well accommodate the volume variation during potassiation/depotassiation process. As a result, a high K-storage capacity of 608 mAh g-1 at 100 mA g-1 and stable cycling capacity of 330.6 mAh g-1 at 1000 mA g-1 after 500 cycles are achieved.

Room-Temperature Liquid Metal Confined in MXene Paper as a Flexible, Freestanding, and Binder-Free Anode for Next-Generation Lithium-Ion Batteries.

Exploring flexible lithium-ion batteries is required with the ever-increasing demand for wearable and portable electronic devices. Selecting a flexible conductive substrate accompanying with closely coupled active materials is the key point. Here, a lightweight, flexible, and freestanding MXene/liquid metal paper is fabricated by confining 3 °C GaInSnZn liquid metal in the matrix of MXene paper without any binder or conductive additive. When used as anode for lithium-ion cells, it can deliver a high discharge capacity of 638.79 mAh g-1 at 20 mA g-1 . It also exhibits satisfactory rate capacities, with discharge capacities of 507.42, 483.33, 480.22, 452.30, and 404.47 mAh g-1 at 50, 100, 200, 500, and 1000 mA g-1 , respectively. The cycling performance is obviously improved by slightly reducing the charge-discharge voltage range. The composite paper also has better electrochemical performance than liquid metal coated Cu foil. This study proposes a novel flexible anode by a clever combination of MXene paper and low-melting point liquid metal, paving the way for next-generation lithium-ion batteries.

New Insights into the Electrochemistry Superiority of Liquid Na-K Alloy in Metal Batteries.

The significant issues with alkali metal batteries arise from their poor electrochemical properties and safety problems, limiting their applications. Herein, TiO2 nanoparticles embedded into N-doped porous carbon truncated ocatahedra (TiO2 ⊂NPCTO) are engineered as a cathode material with different metal anodes, including solid Na or K and liquid Na-K alloy. Electrochemical performance and kinetics are systematically analyzed, with the aim to determine detailed electrochemistry. By using a galvanostatic intermittent titration technique, TiO2 ⊂NPCTO/NaK shows faster diffusion of metal ions in insertion and extraction processes than that of Na-ions and K-ions in solid Na and K. The lower reaction resistance of liquid Na-K alloy electrode is also examined. The higher b-value of TiO2 ⊂NPCTO/NaK confirms that the reaction kinetics are promoted by the surface-induced capacitive behavior, favorable for high rate performance. This superiority highly pertains to the distinct liquid-liquid junction between the electrolyte and electrode, and the prohibition of metal dendrite growth, substantiated by symmetric cell testing, which provides a robust and homogeneous interface more stable than the traditional solid-liquid one. Hence, the liquid Na-K alloy-based battery exhibits to better cyclablity with higher capacity, rate capability, and initial coulombic efficiency than solid Na and K batteries.