Boosting Solar-Driven CO2 Conversion to Ethanol via Single-Atom Catalyst with Defected Low-Coordination Cu-N2 Motif.

In this paper, we report a high-performance carbon nitride supported Cu single-atom catalyst featuring defected low-coordination Cu-N2 motif (Cu-N2-V). Lead many recently reported photocatalysts and its Cu-N3 and Cu-N4 counterparts, Cu-N2-V exhibits superior photocatalytic activity for CO2 reduction to ethanol, delivering 69.8 µmol g-1 h-1 ethanol production rate, 97.8% electron-based ethanol selectivity, and a yield of ~10 times higher than Cu-N3 and Cu-N4. Revealed by the extensive experimental investigation combined with the DFT calculation, the superior photoactivity of Cu-N2-V stems from its unique defected Cu-N2 configuration. Firstly, Cu in Cu-N2-V exist in Cu+/Cu2+ dual valence states, although predominantly in Cu+. The Cu+ sites support CO2 activation and the Cu+/Cu2+ sites are conducive for strong *CO adsorption and subsequent *CO-*CO dimerization enabling C-C coupling. Secondly, the Cu sites in Cu-N2-V are rich in electrons and thus highly active. Together they dictate the rate-determining step on CO2 photoreduction to ethanol and lower the Gibbs free energy change. Furthermore, the defected configuration also promotes light adsorption and charge separation efficiency. Collectively, these make Cu-N2-V an effective and high-performance catalyst for solar-driven CO2 conversion to ethanol. This study also reveals the valence state change of Cu in Cu-N2-V during the CO2 photoreduction reaction.

Rapid Silicification of a DNA Origami with Shape Fidelity.

High-fidelity patterning of DNA origami nanostructures on various interfaces holds great potential for nanoelectronics and nanophotonics. However, distortion of a DNA origami often occurs due to the strong interface interactions, e.g., on two-dimensional (2D) materials. In this study, we discovered that the adsorption of silica precursors in rapid silicification can prevent the distortion caused by graphene and generates a high shape-fidelity DNA origami-silica composite on a graphene interface. We found that an incubation time of 1 min and silicification time of 16 h resulted in the formation of DNA origami-silica composites with the highest shape fidelity of 99%. By comparing the distortion of the DNA origami on the graphene interface with and without silicification, we observed that rapid silicification effectively preserved the integrity of the DNA origami. Statistical analysis of scanning electron microscopy data indicates that compared to bare DNA origami, the DNA origami-silica composite has an increased shape fidelity by more than two folds. Furthermore, molecular dynamics simulations revealed that rapid silicification effectively suppresses the distortion of the DNA origami through the interhelical insertion of silica precursors. Our strategy provides a simple yet effective solution to maintain the shape-fidelity DNA origami on interfaces that have strong interaction with DNA molecules, expanding the applicable interfaces for patterning 2D DNA origamis.

Optimizing potassium polysulfides for high performance potassium-sulfur batteries.

Potassium-sulfur batteries attract tremendous attention as high-energy and low-cost energy storage system, but achieving high utilization and long-term cycling of sulfur remains challenging. Here we show a strategy of optimizing potassium polysulfides for building high-performance potassium-sulfur batteries. We design the composite of tungsten single atom and tungsten carbide possessing potassium polysulfide migration/conversion bi-functionality by theoretical screening. We create two ligand environments for tungsten in the metal-organic framework, which respectively transmute into tungsten single atom and tungsten carbide nanocrystals during pyrolysis. Tungsten carbide provide catalytic sites for potassium polysulfides conversion, while tungsten single atoms facilitate sulfides migration thereby significantly alleviating the insulating sulfides accumulation and the associated catalytic poisoning. Resultantly, highly efficient potassium-sulfur electrochemistry is achieved under high-rate and long-cycling conditions. The batteries deliver 89.8% sulfur utilization (1504 mAh g-1), superior rate capability (1059 mAh g-1 at 1675 mA g-1) and long lifespan of 200 cycles at 25 °C. These advances enlighten direction for future KSBs development.

Twisted DNA Origami-Based Chiral Monolayers for Spin Filtering.

DNA monolayers with inherent chirality play a pivotal role across various domains including biosensors, DNA chips, and bioelectronics. Nonetheless, conventional DNA chiral monolayers, typically constructed from single-stranded DNA (ssDNA) or double-stranded DNA (dsDNA), often lack structural orderliness and design flexibility at the interface. Structural DNA nanotechnology has emerged as a promising solution to tackle these challenges. In this study, we present a strategy for crafting highly adaptable twisted DNA origami-based chiral monolayers. These structures exhibit distinct interfacial assembly characteristics and effectively mitigate the structural disorder of dsDNA monolayers, which is constrained by a limited persistence length of ∼50 nm of dsDNA. We highlight the spin-filtering capabilities of seven representative DNA origami-based chiral monolayers, demonstrating a maximal one-order-of-magnitude increase in spin-filtering efficiency per unit area compared with conventional dsDNA chiral monolayers. Intriguingly, our findings reveal that the higher-order tertiary chiral structure of twisted DNA origami further enhances the spin-filtering efficiency. This work paves the way for the rational design of DNA chiral monolayers.

Reconstructing Hydrogen-Bond Network for Efficient Acidic Oxygen Evolution.

Developing highly active oxygen evolution reaction (OER) catalysts in acidic conditions is a pressing demand for proton-exchange membrane water electrolysis. Manipulating proton character at the electrified interface, as the crux of all proton-coupled electrochemical reactions, is highly desirable but elusive. Herein we present a promising protocol, which reconstructs a connected hydrogen-bond network between the catalyst-electrolyte interface by coupling hydrophilic units to boost acidic OER activity. Modelling on N-doped-carbon-layer clothed Mn-doped-Co3O4 (Mn-Co3O4@CN), we unravel that the hydrogen-bond interaction between CN units and H2O molecule not only drags the free water to enrich the surface of Mn-Co3O4 but also serves as a channel to promote the dehydrogenation process. Meanwhile, the modulated local charge of the Co sites from CN units/Mn dopant lowers the OER barrier. Therefore, Mn-Co3O4@CN surpasses RuO2 at high current density (100 mA cm-2 @ ~538 mV).

Combination of gold nanoclusters and silicon quantum dots for ratiometric fluorometry: One system, two mechanisms.

A ratiometric fluorometry based on silicon quantum dots (SiQDs) and gold nanoclusters (AuNCs) is constructed for detecting activity of butyrylcholinesterase (BChE) in human serum. By using thiobutyrylcholine iodide (BTCh) as the substrate of BChE-catalyzed hydrolysis reaction, variation of fluorescence emission from AuNCs is employed as an indicator of BChE activity since one of the hydrolysis products, thiocholine (TCh), would influence the aggregation state of AuNCs and consequently led to the change of fluorescence quantum efficiency of AuNCs. It is interesting that there are two mechanisms working for the fluorescence emission of aggregated AuNCs: aggregation-induced emission enhancement (AIEE) and aggregation-caused quenching (ACQ) with the presence of TCh at very low and higher concentration levels, respectively. Although both of these mechanisms can be utilized for sensing BChE, their opposite influence on the fluorescence emission of aggregated AuNCs should be worthy of attention, especially in the process of developing fluorescence methods for detecting trace targets by using AuNCs. In order to eliminate the fluctuation of fluorophotometer, SiQDs is chosen as the fluorophore to develop by ratiometric fluorescence methods in this work. Additionally, obvious aggregation of AuNCs induces significant decrease of inner filter effect (IFE) on the fluorescence emitted from SiQDs, while mild aggregation of AuNCs demonstrates little IFE. The linear ranges for detecting activity of BChE are 0.004 - 0.05 U/L and 0.5 - 20 U/L by ratiometric fluorometry based on the AIEE and ACQ, respectively. The very different responses originated from AIEE and ACQ of AuNCs would respectively make their own contributions to the determination of BChE activities at very low or high levels, which facilitate the developments of enhanced or quenched fluorescence methods. However, the detection of BChE activities at medium levels might suffer from the combination of AIEE and ACQ with ambiguous fractions. Therefore, it must be careful during the processes of developing and applying fluorescence methods based on the AIEE and ACQ of AuNCs, as well as the process of evaluating their analytical performance.

Ion Pre-Embedding Engineering of δ-MnO2 for Chemically Self-Charging Aqueous Zinc Ions Batteries.

Aqueous zinc ion batteries (ZIBs), especially those with self-charging properties, have been promisingly developed in recent years. Yet, most inorganic materials feature high redox potential, which limit their development in the self-charging field. To achieve this target, by pre-embedding potassium ions into δ-MnO2 to reduce the energy barrier in oxygen adsorption, the first application of MnO2 in self-charging ZIBs is realized. The design features a facile two-electrode configuration with no excessively complex component to allow for energy storage and conversion. Due to the voltage difference between the oxygen in the air and the discharge products, a redox reaction can be carried out spontaneously to realize the self-charging process. After the chemical self-charging process, the Zn-K0.37 MnO2 ·0.54H2 O/C cell achieves an open circuit voltage of around 1.42 V and a discharge capacity of 201 mAh g-1 , reflecting the promising self-charging capability. Besides, the chemically self-charging ZIBs operate well in multiple modes of constant current charge/discharge/chemical charging. And decent cycling capability can also be achieved at extreme temperatures and high mass loading. This work promotes the development of ZIBs and further broadens the application of inorganic metal oxides in the self-charging systems.

Designing Breathing Air-electrode and Enhancing the Oxygen Electrocatalysis by Thermoelectric Effect for Efficient Zn-air Batteries.

The sluggish kinetics and mutual interference of oxygen evolution and reduction reactions in the air electrode resulted in large charge/discharge overpotential and low energy efficiency of Zn-air batteries. In this work, we designed a breathing air-electrode configuration in the battery using P-type Ca3 Co4 O9 and N-type CaMnO3 as charge and discharge thermoelectrocatalysts, respectively. The Seebeck voltages generated from thermoelectric effect of Ca3 Co4 O9 and CaMnO3 synergistically compensated the charge and discharge overpotentials. The carrier migration and accumulation on the cold surface of Ca3 Co4 O9 and CaMnO3 optimized the electronic structure of metallic sites and thus enhanced their intrinsic catalytic activity. The oxygen evolution and reduction overpotentials were enhanced by 101 and 90 mV, respectively, at temperature gradient of 200 °C. The breathing Zn-air battery displayed a remarkable energy efficiency of 68.1 %. This work provides an efficient avenue towards utilizing waste heat for improving the energy efficiency of Zn-air battery.

A device-independent method for the colorimetric quantification on microfluidic sensors using a color adaptation algorithm.

A general and adaptable method is proposed to reliably extract quantitative information from smartphone images of microfluidic sensors. By analyzing and processing the color information of selected standard substances, the influence of light conditions, device differences, and human factors could be significantly reduced. Machine learning and multivariate fitting methods were proved to be effective for chroma correction, and a key element was the training of sample size and the fitting form, respectively. A custom APP was developed and validated using a high-sensitivity chromium ion quantification paper chip. The average chroma deviations under different conditions were reduced by more than 75% in RGB color space, and the concentration test error was reduced by more than half compared with the commonly used method. The proposed approach could be a beneficial supplement to existing and potential colorimetry-based detection methods.

Activating RuOCo Interaction on the a-Co(OH)2 @Ru Interface for Accelerating the Volmer Step of Alkaline Hydrogen Evolution.

The state-of-the-art active hydrogen evolution reaction (HER) catalysts in acid electrolytes generally lose considerable catalytic performance in alkaline electrolytes mainly due to the additional water dissociation step. Designing composite materials is an effective strategy to accelerate alkaline water electrolysis by optimizing the electronic structure of materials. Here, different phases of Co(OH)2 -supported Ru clusters (α/ß-Co(OH)2 @Ru) are prepared for enabling a highly efficient electrocatalytic HER performance in alkaline solution. The prepared α-Co(OH)2 nanosheets facilitate the loading of uniform and high-density Ru clusters and the formed highly active RuOCo bonds at the interface. The synergistic interaction endows the hybrid catalyst with low overpotential of 33 mV at 10 mA cm-2 . Moreover, the homemade anion exchange membrane water electrolysis cell based on α-Co(OH)2 @Ru affords a cell voltage of 2 V to drive a current density of 270 mA cm-2 and performs stably during continuous operation for over 100 h. Density functional theory calculations demonstrate that active RuOCo bonds in α-Co(OH)2 @Ru optimize the energy barriers for H2 O dissociation and OH- desorption to facilitate the Volmer reaction step. This work offers a strategy for designing interfacial chemical bonds for high electrocatalytic activity.

Lattice oxygen activation in disordered rocksalts for boosting oxygen evolution.

The recent development of some special oxygen evolution reaction (OER) electrocatalysts shows that the lattice oxygen could participate in the catalysis process via the lattice oxygen oxidation mechanism (LOM), which the provides good possibility of exploring advanced electrocatalysts that could overcome the scaling relationship in conventional catalysis processes through a traditional adsorbate evolution mechanism. In this work, we theoretically predict that, benefiting from the unhybridized O-Li orbitals and the resulting metastable Li-O-Li ligands, the lattice oxygen could be easily activated and oxidized at relatively high oxidation voltages. Thus, lithium-excess disordered rocksalts (DRX) should possess the potential for acting as active OER electrocatalysts, which catalyze through the LOM pathway. The isotope labelling experimental results show that the lattice oxygen in the DRX was activated and participated in the OER process through the LOM pathway. The typical DRX of Li1.2Fe0.4Ti0.5O2 displays obviously pH-dependent OER activity under the LOM process and shows a low overpotential of 263 mV to reach 10 mA cm-2 with long-term stability for 100 hours. The turnover frequency of Li1.2Fe0.4Ti0.5O2 is nearly 9 times that of LiFePO4 at the overpotential of 300 mV. This work opens a new chemical space for exploring efficient electrocatalysts to enhance the OER performance through the LOM pathway.

Functionalized Nanocomposite Gel Polymer Electrolyte with Strong Alkaline-Tolerance and High Zinc Anode Stability for Ultralong-Life Flexible Zinc-Air Batteries.

Increasing pursuit of next-generation wearable electronics has put forward the demand of reliable energy devices with high flexibility, durability, and enhanced electrochemical performances. Flexible aqueous zinc-air batteries (FAZABs) have attracted great interests owing to the high energy density, safety, and environmental benignity, for which quasi-solid-state gel polymer electrolytes (QSGPEs) are state-of-the-art electrolytes with high ionic conductivity, flexibility, and resistance to leakage problems of traditional liquid electrolytes. Compared to commonly used PVA-KOH electrolyte with poor electrolyte retention capability and cycling stability, a new type of sulfonate functionalized nanocomposite QSGPE is applied in FAZABs with high ionic conductivity, strong alkaline tolerance, and high zinc anode stability. Notably, the existence of (1) strong anionic sulfonate groups of QSGPEs, contributing to the exposure of preferred Zn (002) plane that is more resistant to zinc dendrite formation, and (2) nano-attapulgite electrolyte additives, beneficial for the enhancement of ionic conductivity, electrolyte uptake, and retention capability, endows a ultralong cycling life of 450 h for the fabricated FAZAB. Furthermore, flexible energy belts and knittable energy wires fabricated with a series/parallel unit of several FAZABs can be used to power various wearable electronics.

Amorphous Mo-doped NiS0.5 Se0.5 Nanosheets@Crystalline NiS0.5 Se0.5 Nanorods for High Current-density Electrocatalytic Water Splitting in Neutral Media.

It is vitally important to develop highly active, robust and low-cost transition metal-based electrocatalysts for overall water splitting in neutral solution especially at large current density. In this work, amorphous Mo-doped NiS0.5 Se0.5 nanosheets@crystalline NiS0.5 Se0.5 nanorods (Am-Mo-NiS0.5 Se0.5 ) was synthesized using a facil one-step strategy. In phosphate buffer saline solution, the Am-Mo-NiS0.5 Se0.5 shows tiny overpotentials of 48 and 209 mV for hydrogen evolution reaction (HER), 238 and 514 mV for oxygen evolution reaction (OER) at 10 and 1000 mA cm-2 , respectively. Moreover, Am-Mo-NiS0.5 Se0.5 delivers excellent stability for at least 300 h without obvious degradation. Theoretical calculations revealed that the Ni sites in the defect-rich amorphous structure of Am-Mo-NiS0.5 Se0.5 owns higher electron state density and strengthened the binding energy of H2 O, which will optimize H adsorption/desorption energy barriers and reduce the adsorption energy of OER determining step.

Pumping and sliding of droplets steered by a hydrogel pattern for atmospheric water harvesting.

Atmospheric water harvesting is an emerging strategy for decentralized and potable water supplies. However, water nucleation and microdroplet coalescence on condensing surfaces often result in surface flooding owing to the lack of a sufficient directional driving force for shedding. Herein, inspired by the fascinating properties of lizards and catfish, we present a condensing surface with engineered hydrogel patterns that enable rapid and sustainable water harvesting through the directional pumping and drag-reduced sliding of water droplets. The movement of microscale condensed droplets is synergistically driven by the surface energy gradient and difference in Laplace pressure induced by the arch hydrogel patterns. Meanwhile, the superhydrophilic hydrogel surface can strongly bond inner-layer water molecules to form a lubricant film that reduces drag and facilitates the sliding of droplets off the condensing surface. Thus, this strategy is promising for various water purification techniques based on liquid-vapor phase-change processes.

Mesoporous Ti4O7 Spheres with Enhanced Zinc-Anchoring Effect for High-Performance Zinc-Nickel Batteries.

Zinc-nickel batteries are promising competitors for next-generation power supply due to their benefits of high safety, high working voltage, and attractive rate performance. However, their practical applications are plagued by their poor cycling performance, stemming from uneven redistribution of zinc during cycling that results in dendrite formation and shape changes of the electrode. In this work, mesoporous Ti4O7 microspheres are prepared and are employed as additives of a zinc anode. Notably, the presence of mesopores provides abundant chemisorption sites for Zn(OH)42- ions, inhibiting severe zinc redistribution in the electrode. Moreover, due to the good electrical conductivity and mesopores that serve as ion diffusion channels, the reaction reactivity and reversibility of the zinc electrode are greatly facilitated. As a result, the fabricated zinc-nickel battery with mesoporous Ti4O7 additives (ms-Ti4O7) exhibits an enhanced discharge capacity and a significantly prolonged cycling life. Even at a current of 10 A (∼138 mA cm-2), the ms-Ti4O7-modified anode demonstrates stable operation for longer than 718 h (700 cycles) with a discharge voltage of 1.2 V, which is much longer than those of a ZnO anode (192 h, 117 cycles) and a Ti4O7-particle (p-Ti4O7)-modified battery (590 h, 443 cycles). Furthermore, due to the anchoring effect for Zn(OH)42- and the uniform electric field, the effect of mesoporous Ti4O7 on inhibiting dendrite formation and shape change of the zinc electrode is highlighted.

Porosity Engineering towards Nitrogen-Rich Carbon Host Enables Ultrahigh Capacity Sulfur Cathode for Room Temperature Potassium-Sulfur Batteries.

Potassium-sulfur batteries (KSBs) are regarded as a promising large-scale energy storage technology, owing to the high theoretical specific capacity and intrinsically low cost. However, the commercialization of KSBs is hampered by the low sulfur utilization and notorious shuttle effect. Herein, we employ a porosity engineering strategy to design nitrogen-rich carbon foam as an efficient sulfur host. The tremendous micropores magnify the chemical interaction between sulfur species and the polar nitrogen functionalities decorated carbon surface, which significantly improve the sulfur utilization and conversion. Meanwhile, the abundant mesopores provide ample spaces, accommodating the large volume changes of sulfur upon reversible potassation. Resultantly, the constructed sulfur cathode delivers an ultrahigh initial reversible capacity of 1470 mAh g-1 (87.76% of theoretical capacity) and a superior rate capacity of 560 mAh g-1 at 2 C. Reaching the K2S phase in potassiation is the essential reason for obtaining the ultrahigh capacity. Nonetheless, systematic kinetics analyses demonstrate that the K2S involved depotassiation deteriorates the charge kinetics. The density functional theory (DFT) calculation revealed that the nitrogen-rich micropore surface facilitated the sulfur reduction for K2S but created a higher energy barrier for the K2S decomposition, which explained the discrepancy in kinetics modification effect produced by the porosity engineering.

Mechanistic Insight into Hydrocarbon Synthesis via CO2 Hydrogenation on χ-Fe5C2 Catalysts.

Converting CO2 into value-added chemicals and fuels is one of the promising approaches to alleviate CO2 emissions, reduce the dependence on nonrenewable energy resources, and minimize the negative environmental effect of fossil fuels. This work used density functional theory (DFT) calculations combined with microkinetic modeling to provide fundamental insight into the mechanisms of CO2 hydrogenation to hydrocarbons over the iron carbide catalyst, with a focus on understanding the energetically favorable pathways and kinetic controlling factors for selective hydrocarbon production. The crystal orbital Hamiltonian population analysis demonstrated that the transition states associated with O-H bond formation steps within the path are less stable than those of C-H bond formation, accounting for the observed higher barriers in O-H bond formation from DFT. Energetically favorable pathways for CO2 hydrogenation to CH4 and C2H4 products were identified which go through an HCOO intermediate, while the CH* species was found to be the key C1 intermediate over χ-Fe5C2(510). The microkinetic modeling results showed that the relative selectivity to CH4 is higher than C2H4 in CO2 hydrogenation, but the trend is opposite under CO hydrogenation conditions. The major impact on C2 hydrocarbon production is attributed to the high surface coverage of O* from CO2 conversion, which occupies crucial active sites and impedes C-C couplings to C2 species over χ-Fe5C2(510). The coexistence of iron oxide and carbide phases was proposed and the interfacial sites created between the two phases impact CO2 surface chemistry. Adding potassium into the Fe5C2 catalyst accelerates O* removal from the carbide surface, enhances the stability of the iron carbide catalyst, thus, promotes C-C couplings to hydrocarbons.

Zn-Metal-Organic Framework Derived Ordered Mesoporous Carbon-Based Nanostructure for High-Performance and Universal Multivalent Metal Ion Storage.

Metal-organic framework (MOF) derivatives promise great potential in energy storage and conversion because of their excellent tunability in both the active metal sites, organic links, and the overall structures down to atomic and up to mesoscale. Nevertheless, a big challenge is to precisely control and thoroughly understand the actual MOF-to-derivative conversion process to realize the template-free synthesis of the MOF-derived ordered mesoporous materials. Here, a class of ordered mesoporous N-doped carbon nanoflakes is presented with slit-shaped pores synthesized by one-step pyrolysis of Zn1 Cux -MOF, where the Cu doping plays a critically important direction-inducing function on the dissociation of organic ligands during the pyrolysis. Benefiting from the uniquely ordered mesoporous structure and large specific surface area (910 m2 g-1 ), the Zn1 Cux -MOF-derived ordered mesoporous carbon nanoflakes present outstanding electrochemical storage performance for multivalent metal ions, such as Mg2+ , Ca2+ , Co2+ , Ni2+ , Al3+ , and Zn2+ , demonstrating the universal nature of the slit-shaped pores in enabling the multivalent metal ions for energy storage. Moreover, the assembled flexible Zn-ion hybrid supercapacitor (ZHSC) delivers a high specific capacity of 134 mAh g-1 at 0.5 A g-1 , excellent cycling and mechanical stability, showing great application potential in the new generation energy storage devices.

Atomically Dispersed Indium-Copper Dual-Metal Active Sites Promoting C-C Coupling for CO2 Photoreduction to Ethanol.

Photoreduction of CO2 to C2+ solar fuel is a promising carbon-neutral technology for renewable energy. This strategy is challenged by its low productivity due to low efficiency in multielectron utilization and slow C-C coupling kinetics. This work reports a dual-metal photocatalyst consisting of atomically dispersed indium and copper anchored on polymeric carbon nitride (InCu/PCN), on which the photoreduction of CO2 delivered an excellent ethanol production rate of 28.5 µmol g-1 h-1 with a high selectivity of 92 %. Coupled experimental investigation and DFT calculations reveal the following mechanisms underpinning the high performance of this catalyst. Essentially, the In-Cu interaction enhances the charge separation by accelerating charge transfer from PCN to the metal sites. Indium also transfers electrons to neighboring copper via Cu-N-In bridges, increasing the electron density of copper active sites. Furthermore, In-Cu dual-metal sites promote the adsorption of *CO intermediates and lower the energy barrier of C-C coupling.

An ultrasonication-aided self-assembly strategy toward a PTCDA/RGO film cathode for organic K-ion full batteries.

A free-standing PTCDA/RGO film was synthesized by an ultrasonication-aided self-assembly strategy to alleviate the solubility of PTCDA in organic electrolytes. The PTCDA/RGO-50% film cathode exhibits a high capacity of 135.1 mA h g-1 at 0.05 A g-1 and excellent cycling stability (capacity retention of 85% after 200 cycles) for potassium ion batteries.