Tuning the Electrolyte and Interphasial Chemistry for All-Climate Sodium-ion Batteries.

Sodium-ion batteries (SIBs) present a promising avenue for next-generation grid-scale energy storage. However, realizing all-climate SIBs operating across a wide temperature range remains a challenge due to the poor electrolyte conductivity and instable electrode interphases at extreme temperatures. Here, we propose a comprehensively balanced electrolyte by pairing carbonates with a low-freezing-point and low-polarity ethyl propionate solvent which enhances ion diffusion and Na+-desolvation kinetics at sub-zero temperatures. Furthermore, the electrolyte leverages a combinatorial borate- and nitrile-based additive strategy to facilitate uniform and inorganic-rich electrode interphases, ensuring excellent rate performance and cycle stability over a wide temperature range from -45 °C to 60 °C. Notably, the Na||sodium vanadyl phosphate cell delivers a remarkable capacity of 105 mAh g-1 with a high rate of 2 C at -25 °C. In addition, the cells exhibit excellent cycling stability over a wide temperature range, maintaining a high capacity retention of 84.7 % over 3,000 cycles at 60 °C and of 95.1 % at -25 °C over 500 cycles. The full cell also exhibits impressive cycling performance over a wide temperature range. This study highlights the critical role of electrolyte and interphase engineering for enabling SIBs that function optimally under diverse and extreme climatic environments.

Rapid-charging aluminium-sulfur batteries operated at 85 °C with a quaternary molten salt electrolyte.

Molten salt aluminum-sulfur batteries are based exclusively on resourcefully sustainable materials, and are promising for large-scale energy storage owed to their high-rate capability and moderate energy density; but the operating temperature is still high, prohibiting their applications. Here we report a rapid-charging aluminium-sulfur battery operated at a sub-water-boiling temperature of 85 °C with a tamed quaternary molten salt electrolyte. The quaternary alkali chloroaluminate melt - possessing abundant electrochemically active high-order Al-Cl clusters and yet exhibiting a low melting point - facilitates fast Al3+ desolvation. A nitrogen-functionalized porous carbon further mediates the sulfur reaction, enabling the battery with rapid-charging capability and excellent cycling stability with 85.4% capacity retention over 1400 cycles at a charging rate of 1 C. Importantly, we demonstrate that the asymmetric sulfur reaction mechanism that involves formation of polysulfide intermediates, as revealed by operando X-ray absorption spectroscopy, accounts for the high reaction kinetics at such temperature wherein the thermal management can be greatly simplified by using water as the heating media.

Surface passivation for highly active, selective, stable, and scalable CO2 electroreduction.

Electrochemical conversion of CO2 to formic acid using Bismuth catalysts is one the most promising pathways for industrialization. However, it is still difficult to achieve high formic acid production at wide voltage intervals and industrial current densities because the Bi catalysts are often poisoned by oxygenated species. Herein, we report a Bi3S2 nanowire-ascorbic acid hybrid catalyst that simultaneously improves formic acid selectivity, activity, and stability at high applied voltages. Specifically, a more than 95% faraday efficiency was achieved for the formate formation over a wide potential range above 1.0 V and at ampere-level current densities. The observed excellent catalytic performance was attributable to a unique reconstruction mechanism to form more defective sites while the ascorbic acid layer further stabilized the defective sites by trapping the poisoning hydroxyl groups. When used in an all-solid-state reactor system, the newly developed catalyst achieved efficient production of pure formic acid over 120 hours at 50 mA cm-2 (200 mA cell current).

A solution-to-solid conversion chemistry enables ultrafast-charging and long-lived molten salt aluminium batteries.

Conventional solid-to-solid conversion-type cathodes in batteries suffer from poor diffusion/reaction kinetics, large volume changes and aggressive structural degradation, particularly for rechargeable aluminium batteries (RABs). Here we report a class of high-capacity redox couples featuring a solution-to-solid conversion chemistry with well-manipulated solubility as cathodes-uniquely allowed by using molten salt electrolytes-that enable fast-charging and long-lived RABs. As a proof-of-concept, we demonstrate a highly reversible redox couple-the highly soluble InCl and the sparingly soluble InCl3-that exhibits a high capacity of about 327 mAh g-1 with negligible cell overpotential of only 35 mV at 1 C rate and 150 °C. The cells show almost no capacity fade over 500 cycles at a 20 C charging rate and can sustain 100 mAh g-1 at 50 C. The fast oxidation kinetics of the solution phase upon initiating the charge enables the cell with ultrafast charging capability, whereas the structure self-healing via re-forming the solution phase at the end of discharge endows the long-term cycling stability. This solution-to-solid mechanism will unlock more multivalent battery cathodes that are attractive in cost but plagued by poor reaction kinetics and short cycle life.

Reversible Zn Metal Anodes Enabled by Trace Amounts of Underpotential Deposition Initiators.

Routine electrolyte additives are not effective enough for uniform zinc (Zn) deposition, because they are hard to proactively guide atomic-level Zn deposition. Here, based on underpotential deposition (UPD), we propose an "escort effect" of electrolyte additives for uniform Zn deposition at the atomic level. With nickel ion (Ni2+ ) additives, we found that metallic Ni deposits preferentially and triggers the UPD of Zn on Ni. This facilitates firm nucleation and uniform growth of Zn while suppressing side reactions. Besides, Ni dissolves back into the electrolyte after Zn stripping with no influence on interfacial charge transfer resistance. Consequently, the optimized cell operates for over 900 h at 1 mA cm-2 (more than 4 times longer than the blank one). Moreover, the universality of "escort effect" is identified by using Cr3+ and Co2+ additives. This work would inspire a wide range of atomic-level principles by controlling interfacial electrochemistry for various metal batteries.

Facile preparation of a MXene-graphene oxide membrane and its voltage-gated ion transport behavior.

Two-dimensional MXenes have become a crucial topic in the field of ion transportation owing to their excellent electrochemical performance. Herein, a strategy for preparing a layered MXene-graphene oxide (GO) membrane via vacuum filtration is proposed, which endows the delaminated two-dimensional MXene-GO membrane (MGOm) with excellent electrical conductivity and chemical stability, achieving an excellent voltage-gated ion transport behavior. Owing to the presence of charges or dipoles within the membrane's channel, the movement of electrons or dipoles under the influence of membrane potential is possible. By varying the transmembrane potential, the transition between the closed and open states of the voltage-gated ion channel can be adjusted. When a negative potential is applied at osmotic pressure, the force between the charged MGOm sheet and the cation (K+) is enhanced, promoting ion permeation. Conversely, the application of positive potential attenuates electrostatic attraction, resulting in a decrease in ion permeability. In addition, the effects of MXene and GO with different modulation ratios on the voltage-gated ion transport have shown that when the modulation ratio of MXene : GO is 7 : 3, the optimal ion permeation rate is achieved. In conclusion, the conductive film with voltage-gated nanochannels is a promising alternative for ion transportation, opening up new avenues for the further exploration of MXene materials in energy storage devices.

Dense T-Nb2O5/Carbon Microspheres for Ultrafast-(Dis)charge and High-Loading Lithium-Ion Batteries.

Orthorhombic niobium pentoxide (T-Nb2O5) is regarded as a potential anode material for lithium-ion batteries (LIBs) due to ultrafast charge/discharge and high safety. However, the poor electronic conductivity and low mass loading of nanostructured T-Nb2O5 limit its practical application in LIBs. Herein, we design and construct dense microspheres consisting of nanostructured T-Nb2O5 embedded in amorphous N-doped carbon (Nb2O5@NC) via a facile method to achieve fast ionic and electronic transport as well as a high mass loading. The dense micro-sized particles with an interconnected carbon network avoid the low mass loading and volumetric energy density of conventional nanostructures. Interconnected pores in the range of a few nanometers are also formed in the Nb2O5@NC microspheres. Notably, at a high mass loading of 12.8 mg cm-2, Nb2O5@NC can achieve a high specific capacity of 171.5 mAh g-1 and an areal capacity of 2.05 mAh cm-2, showing its high lithium storage capacity. The intercalation reaction mechanism with a small volume change during cycling at both crystal lattice and microsphere levels is confirmed by in situ X-ray diffraction and in situ high-resolution transmission electron microscopy. The elegant structure and the electrochemical reaction mechanism disclosed in the work is important for designing ultrafast-(dis)charge electrode materials.

Ultrahigh Stable Methanol Oxidation Enabled by a High Hydroxyl Concentration on Pt Clusters/MXene Interfaces.

Anchoring platinum catalysts on appropriate supports, e.g., MXenes, is a feasible pathway to achieve a desirable anode for direct methanol fuel cells. The authentic performance of Pt is often hindered by the occupancy and poisoning of active sites, weak interaction between Pt and supports, and the dissolution of Pt. Herein, we construct three-dimensional (3D) crumpled Ti3C2Tx MXene balls with abundant Ti vacancies for Pt confinement via a spray-drying process. The as-prepared Pt clusters/Ti3C2Tx (Ptc/Ti3C2Tx) show enhanced electrocatalytic methanol oxidation reaction (MOR) activity, including a relatively low overpotential, high tolerance to CO poisoning, and ultrahigh stability. Specifically, it achieves a high mass activity of up to 7.32 A mgPt-1, which is the highest value reported to date in Pt-based electrocatalysts, and 42% of the current density is retained on Ptc/Ti3C2Tx even after the 3000 min operative time. In situ spectroscopy and theoretical calculations reveal that an electric field-induced repulsion on the Ptc/Ti3C2Tx interface accelerates the combination of OH- and CO adsorption intermediates (COads) in kinetics and thermodynamics. Besides, this Ptc/Ti3C2Tx also efficiently electrocatalyze ethanol, ethylene glycol, and glycerol oxidation reactions with comparable activity and stability to commercial Pt/C.

Fast-charging aluminium-chalcogen batteries resistant to dendritic shorting.

Although batteries fitted with a metal negative electrode are attractive for their higher energy density and lower complexity, the latter making them more easily recyclable, the threat of cell shorting by dendrites has stalled deployment of the technology1,2. Here we disclose a bidirectional, rapidly charging aluminium-chalcogen battery operating with a molten-salt electrolyte composed of NaCl-KCl-AlCl3. Formulated with high levels of AlCl3, these chloroaluminate melts contain catenated AlnCl3n+1- species, for example, Al2Cl7-, Al3Cl10- and Al4Cl13-, which with their Al-Cl-Al linkages confer facile Al3+ desolvation kinetics resulting in high faradaic exchange currents, to form the foundation for high-rate charging of the battery. This chemistry is distinguished from other aluminium batteries in the choice of a positive elemental-chalcogen electrode as opposed to various low-capacity compound formulations3-6, and in the choice of a molten-salt electrolyte as opposed to room-temperature ionic liquids that induce high polarization7-12. We show that the multi-step conversion pathway between aluminium and chalcogen allows rapid charging at up to 200C, and the battery endures hundreds of cycles at very high charging rates without aluminium dendrite formation. Importantly for scalability, the cell-level cost of the aluminium-sulfur battery is projected to be less than one-sixth that of current lithium-ion technologies. Composed of earth-abundant elements that can be ethically sourced and operated at moderately elevated temperatures just above the boiling point of water, this chemistry has all the requisites of a low-cost, rechargeable, fire-resistant, recyclable battery.

Enhanced ion transport in nanochannels of MXenes by Mg2+ pre-intercalation.

How to enhance the ion transport between MXene layers is a critical topic in the fields of electrochemical storage (especially supercapacitors) and water treatment. Vertical structure design of MXene nanosheets and single-molecule organic pre-intercalation are proposed, but the methods to enhance the ion transport through MXene nanochannels by modulating MXene's surface state have not been investigated yet. The interaction mechanism between Mg2+ and MXene 2D nanochannels during the transport process has not been thoroughly explored. In our work, we used a facile infiltration method to immerse the Ti3C2Tx membranes in MgCl2 solution for ion pre-intercalation. We found that the pre-intercalation of Mg2+ has a significant effect on the increase of the ion transport rate of Ti3C2Tx membranes, especially for Li+ which reached 268.49% compared with those of non-intercalation membranes. Through multiple characterization methods, we discovered that the enhancement of ion transport rate by pre-intercalation of Mg2+ mainly originated from the fact that the pre-intercalation of Mg2+ increased the layer spacing of MXene films as the channel support between layers while Mg2+ increased the work function (WF) of 2D nanochannels thereby reducing the interaction of other ions with the channel surface. The acceleration phenomenon of ion transport by surface state modulation proposed in our work will provide new strategies for the design of structure and regulation of surface states, revealing the mechanism of capacity improvement.

Amine-Wetting-Enabled Dendrite-Free Potassium Metal Anode.

Considered as an imperative alternative to the commercial LiFePO4 battery, the potassium metal battery possesses great potential in grid-scale energy storage systems due to the low cost, low standard redox potential, and high abundance of potassium. The potassium dendrite growth, large volume change, and unstable solid electrolyte interphase (SEI) on the potassium metal anode have, however, hindered its applications. Although conductive scaffolds coupling with potassium metal have been widely proposed to address the above issues, it remains challenging to fabricate a uniform composite with uncompromised capacity. Herein, we propose a facile and efficient strategy to construct dendrite-free and practical carbon-based potassium composite anodes via amine functionalization of the carbon scaffolds that enables fast molten potassium infusion within several seconds. On the basis of experiments and theoretical calculations, we show that highly potassiophilic amine groups immediately transform carbon scaffolds from nonwetting to wetting to postassium. Our carbon-cloth-based potassium composite anode (K@CC) can accommodate volume fluctuation, provide abundant nucleation sites, and lower the local current density, achieving nondendritic morphology with a stable SEI. The fabricated K0.7Mn0.7Ni0.3O2|K@CC full cell displays excellent rate capability and an ultralong lifespan over 8000 cycles (68.5% retention) at a high current of 1 A g-1.

Ligand Modulation of Active Sites to Promote Electrocatalytic Oxygen Evolution.

Rationally designed catalysts hold the key to address the sluggish kinetics of oxygen evolution reaction (OER). However, engineering the active sites of such catalysts still faces grand challenges. This study proposes a feasible ligand modulation strategy to boost the OER catalytic activity of cobalt-iron oxyhydroxide ((Fe,Co)OOH). The 2-methylimidazole (MI) ligand coordination on (Fe,Co)OOH reduces the orbital overlap between the Fe/Co 3d and O 2p, which weakens the adsorption to oxygen-containing intermediates and thus facilitates the unfavorable O2 desorption. As a result, the MI ligand modulated (Fe,Co)OOH achieves an excellent OER performance with low overpotentials (230/290 mV at 10/100 mA cm-2 ) and excellent durability (>155 h). This study provides a novel ligand modulation strategy for the design of OER catalysts.

Sub-Nanometer Confined Ions and Solvent Molecules Intercalation Capacitance in Microslits of 2D Materials.

The ion intercalation behavior in 2D materials is widely applied in energy storage, electrocatalysis, and desalination. However, the detailed effect of ions on the performance, combining the influence of interlayer force and the change of solvent shell, is far less well understood. Here the solvated alkali metal ions with different sizes are intercalated into the lattice of 2D materials with different spacings (Ti3 C2 Tx , δ-MnO2 , and reduced graphene oxide) to construct the intercalation model related with sub-nanometer confined ions and solvent molecules to further understand the intercalation capacitance. Based on electrochemical methods and density functional theory calculation, the ions lose the electrostatic shielding solvent shell or shorten the distance between the layers, resulting in a significant increase in capacitance. It is found that the intercalation capacitance arises from the diffusion of solvated ions and is controlled by quantum and electrochemical capacitance for desolvated ions. This effect of solvation structure on performance can be applied in a variety of electrochemical interface studies and provides a new research view for energy storage mechanisms.

Quicker and More Zn2+ Storage Predominantly from the Interface.

Aqueous zinc-ion batteries are highly desirable for large-scale energy storage because of their low cost and high-level safety. However, achieving high energy and high power densities simultaneously is challenging. Herein, a VOx sub-nanometer cluster/reduced graphene oxide (rGO) cathode material composed of interfacial VOC bonds is artificially constructed. Therein, a new mechanism is revealed, where Zn2+ ions are predominantly stored at the interface between VOx and rGO, which causes anomalous valence changes compared to conventional mechanisms and exploits the storage ability of non-energy-storing active yet highly conductive rGO. Further, this interface-dominated storage triggers decoupled transport of electrons/Zn2+ ions, and the reversible destruction/reconstruction allows the interface to store more ions than the bulk. Finally, an ultrahigh rate capability (174.4 mAh g-1 at 100 A g-1 , i.e., capacity retention of 39.4% for a 1000-fold increase in current density) and a high capacity (443 mAh g-1 at 100 mA g-1 , exceeding the theoretical capacities of each interfacial component) are achieved. Such interface-dominated storage is an exciting way to build high-energy- and high-power-density devices.

Constructing Three-Dimensional Macroporous TiO2 Microspheres with Enhanced Pseudocapacitive Lithium Storage under Deep Discharging/Charging Conditions.

TiO2 has been intensively investigated as an anode material for lithium-ion batteries (LIBs) in 1.0-3.0 V (vs Li+/Li). However, it is a challenge to realize its theoretical capacity (336 mAh g-1) in this limited potential range. Extending the potential range below 1.0 V would increase its capacity but usually at the expense of its cyclic stability owing to the sluggish ionic diffusion and unsatisfactory structural stability. Here, three-dimensional (3D) macroporous TiO2 microspheres with interconnected pores and nanocrystalline thin walls have been constructed through a scalable template-assisted spray drying method to overcome these obstacles. When applied to LIBs, high and stable discharge capacity (300 mAh g-1 at 0.1 A g-1) as well as superior cyclic stability (242 mAh g-1 after 1000 cycles at 1.0 A g-1) can be achieved under deep discharging/charging conditions (0.01-3.0 V vs Li+/Li). Furthermore, the 3D macroporous structure is well preserved under deep discharging/charging and the in situ X-ray diffraction (XRD) patterns and Raman spectra reveal the dominant pseudocapacitive contribution at low potentials (0.01-1.0 V). This work not only develops a facile method to synthesize macroporous metal oxides but also provides insight into the lithium storage mechanism of TiO2 under deep discharging/charging conditions.

Regulating Lattice-Water-Adsorbed Ions to Optimize Intercalation Potential in 3D Prussian Blue Based Multi-Ion Microbattery.

Miniaturized energy storage device (MESD) is the core module in microscale electronic equipment, yet its electrochemical performance is far away from the actual requirements. The extensive research efforts have improved the performance of MESD via the fabrication techniques and material construction, while ignoring the expansion of optimization strategy in the combination of energy storage mechanism. Herein, the Prussian blue/Zn microbattery is reported with the regulation of lattice-water-adsorbed intercalated ion. The optimal charge transport of cathode is achieved via the optimization of 3D structure of microelectrode to maximize the electrochemical performance. Also, lattice-water-adsorbed ion storage mechanism is further investigated to guide the design of differential energy storage for cathode and anode. The Cu3 (Fe(CN)6 )2 /Zn microbattery, with K+ inter/deintercalation in the cathode and Zn2+ deplating/plating in the anode, displays high capacity (0.281 mAh cm-2 at 2.5 mA cm-2 ), rate performance (0.181 mAh cm-2 at 25 mA cm-2 ), and cycling stability (77.6% capacity retention after 1500 cycles) enhanced by Cu2+ in the electrolyte. This highly efficient combination of fabrication process, active material, and multi-ion storage for microelectrode shows a high tolerance for optimization strategies, expanding the compatibility of optimization path for high-performance MESD.

Recent Advances in High-Performance Microbatteries: Construction, Application, and Perspective.

High-performance miniaturized energy storage devices have developed rapidly in recent years. Different from conventional energy storage devices, microbatteries assume the main responsibility for micropower supply, functionalization, and characterization platforms. Evolving from the essential goals for battery design of high power density, high energy density, and long lifetime, further practical demands for microbatteries (MBs) have been raised for the microfabrication technique and device design. Numerous studies have generally focused on specific aspects of the microelectrode structures or certain microfabrication techniques, while the connection from techniques to functional applications is rarely involved. This Review generally fills such blanks from an application-oriented perspective. First, some basic micromachining techniques with different compatible features are summarized. Afterward, device designs including diversified battery reaction types, configuration, and assembly are highlighted, as well as microbatteries serving powering resources or further complicated functional systems. Finally, through providing the overall design concept based on requirements in application, this Review offers innovative insights for further development of microbatteries.

Confining Ultrafine MoO2 in a Carbon Matrix Enables Hybrid Li Ion and Li Metal Storage.

Poor cycle and rate performance caused by volume effects and sluggish kinetics is the main bottleneck for most lithium-ion battery (LIB) anode materials run on the conversion reaction. Although nanostructure engineering has shown to be an effective method to reduce the undesirable volume effects, cycling instability usually remains in nanostructured electrodes owning to particle aggregation in discharge and loss of active materials in charge. Here, to make these kinds of materials practical, we have developed a structure of ultrafine MoO2 nanoparticles (<3 nm) confined by a conductive carbon nanosheet matrix (MoO2/C). Instead of running on the conversion mechanism, the Li storage in the MoO2/C composite is through a two-step mechanism in discharge: intercalation followed by the formation of metallic Li, acting as a hybrid host for both Li ion intercalation and metallic Li plating. The Li-storage mechanism has been revealed by in situ X-ray diffraction analysis and in situ scanning transmission electron microscopy with corresponding electron energy loss spectrum analysis, which explains the natural origin of such high capacity along with good cyclability. This unique MoO2/C structure exhibits an excellent discharge capacity (810 mAh g-1 at 200 mA g-1) and cyclability (75% capacity retention over 1000 cycles). The carbon sheet plays a vital role in both a conductive network and a structure supporter with a robust confining effect that keeps the size of MoO2 uniformly under 3 nm even after high-temperature calcination. Our finding provides insights for the design of next-generation LIB anode materials with high capacity and longevity.

Three-dimensional graphene-supported nickel disulfide nanoparticles promise stable and fast potassium storage.

Nickel sulfide (NiS2) is generally regarded as an appropriate anode for manufacturing new-type potassium-ion batteries (PIBs), while the development and application of NiS2 are hampered by poor intrinsic electrical conductivity and huge volumetric change during potassiation/de-potassiation. Herein, we construct self-adaptive NiS2 nanoparticles confined to a three-dimensional graphene oxide (NiS2/3DGO) electrode via in situ sulfurization and self-assembly processes. The as-obtained NiS2/3DGO exhibits high reversible capacity (391 mA h g-1) and outstanding rate behavior (stable cycling at 1000 mA g-1) for PIBs. Furthermore, in situ X-ray diffractometry and ex situ Raman test results elucidate partially reversible transformation from the cubic NiS2 phase to the KxNiS2 intermediate, followed by generating a Ni0 and K2S4 product. This phenomenon is caused by the conversion reaction mechanism of NiS2 nanocrystals along with an amorphous phase transition during the initial cycle. Such understandings may shed new light on the application of metal sulfides and give directions to design novel electrodes with desirable structural stability and lifespan.

Wearable Textile-Based Co-Zn Alkaline Microbattery with High Energy Density and Excellent Reliability.

Wearable in-plane Zn-based microbatteries are considered as promising micropower sources for wearable electronics due to their high capacity, low cost, high safety, and easy integration. However, their applications are severely impeded by inadequate energy density arising from unsatisfactory capacity of cathode and poor cycling stability caused by degradation of electrode materials and Zn dendrite. Additionally, the short-circuit induced safety issue caused by Zn dendrite is still a roadblock for Zn-based microbatteries. Herein, a textile-based Co-Zn microbattery with ultrahigh energy density and excellent cycling stability is demonstrated. Benefiting from the fast electron transport of three-dimensional (3D) porous Ni-coated textile and synergistic effect from the hierarchical Co(OH)2 @NiCo layered double hydroxide (LDH) core-shell electrode, the fabricated Co-Zn microbattery with high flexibility delivers superior energy/power densities of 0.17 mWh cm-2 /14.4 mW cm-2 , outperforming most reported micro energy storage devices. Besides, the trench-type configuration as well as the 3D porous Zn@carbon clothes can avoid the short-circuit-induced safety issues, resulting in excellent cycling stability (71% after 800 cycles). The unique core-shell structure and novel configuration provide a brand-new design strategy for high-performance wearable in-plane microdevices.