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Owing to the advantages of high operating voltage, environmental benignity, and low cost, potassium-based dual-ion batteries (KDIBs) have been considered as a potential candidate for large-scale energy storage. However, KDIBs generally suffer from poor cycling performance and unsatisfied capacity, and inactive components of conductive agents, binders, and current collector further lower their overall capacity. Herein, we prepare coral-like carbon nanowires (CCNWs) doped with nitrogen as a binder-free anode material for K+-ion storage, in which the unique coral-like porous nanostructure and amorphous/short-range-ordered composite feature are conducive to enhancing the structural stability, to facilitating the ion transfer and to boosting the full utilization of active sites during potassiation/de-potassiation process. As a result, the CCNW anode possesses a hybrid K+-storage mechanism of diffusive behavior and capacitive adsorption, and stably delivers a high capacity of 276 mAh g-1 at 50 mA g-1, good rate capability up to 2 A g-1, and long-term cycling stability with 93 % capacity retention after 2000 cycles at 1 A g-1. Further, assembling this CCNW anode with an environmentally benign expanded graphite (EG) cathode yields a proof-of-concept KDIB, which shows a high specific capacity of 134.4 mAh g-1 at 100 mA g-1, excellent rate capability of 106.5 mAh g-1 at 1 A g-1, and long-term cycling stability over 1000 cycles without negligible capacity loss. This study provides a feasible approach to developing high-performance anodes for potassium-based energy storage devices.

Aqueous zinc metal batteries (AZMBs) directly utilizing Zn metal anode have been regarded as a promising candidate for the next generation commercial batteries featuring high safety, high theoretical capacity, and appealing chemical stability. However, narrow electrochemical stability windows of aqueous electrolytes, uncontrolled dendrite and limited reversibility still plague its practical applications. Herein, we present a strategy via engineering dilute aqueous Zn(OTf)2 solutions electrolytes with a polyethylene glycol (PEG) network, which substantially decreases the activity of water molecules, and simultaneously enables smooth Zn deposition with a (002) textured and a favorable ZnF2-rich SEI. As a result, symmetric cells with PEG-H2O system show record high cyclic performance (9000 h and 8000 h at current densities of 1 and 2 mA cm−2, respectively), superior interfacial stability and dendrite-free morphology after repeated plating/stripping. Additionally, Zn||70%PEG||V2O5 full batteries also deliver a remarkable energy density of 324.3 W h Kg−1 at a power density of 466.9 W Kg−1 and maintain 84.3% of the capacity over 500 cycles at a high current density of 15 A g−1. All these comprehensive results demonstrate that this electrolyte structural engineering can provide a promising direction for designing high reversibility, long-cycling life aqueous Zn metal batteries.

Funding: Authors acknowledge support from Shenzhen Key Laboratory of Energy Materials for Carbon Neutrality (China). The authors acknowledge support from the National Natural Science Foundation of China (52125105, 22005329, 51972329, 52061160484), the Shenzhen Science and Technology Planning Project (JCYJ20190807172001755, JCYJ20210324101016039, JCYJ20210324101203009), and the Science and Technology Planning Project of Guangdong Province (2019A1515110975, 2021A1515010184, 2019TX05L389). We report the first example of a perovskite sulfate [Na3(H2O)]Fe(SO4)3. Further structure modulation, by dimensional reduction or ligand extension, has resulted in two related layered perovskite-like compounds Na6Fe(SO4)4 and Na12Fe3(SO4)6F8. Taken together, these results open up a more general strategy for the future design of more complex perovskite-related materials. Postprint

Electrochromic batteries (EBs) have been developed as a technical breakthrough to solve the energy issues of storage and saving. Multivalent-ions (Zn2+, Mg2+ and Al3+) have recently demonstrated attractive properties for EBs due to their multiple-electron redox nature. However, still now, reported multivalent-ion EBs are typically assembled with a small-area metallic anode and a large-area electrochromic cathode. Non-uniformity of coloration and unstable metal plating/stripping hinder the developments of these devices. Additionally, insufficient energy/power density of EBs is a huge technical challenge needed to be overcome. In this work, we demonstrated a new aqueous aluminum-ion electrochromic full battery (AIEFB) to overcome the challenges. Systematic studies of density functional theory calculation, molecular dynamics simulation, electrochemical analysis, and mechanical measurements were conducted to optimize electrode materials and electrolyte. A water-in-salt (WIS) Al(OTF)3 electrolyte and a new electrochromic material couple of anodic amorphous WO3 (a-WO3) and cathodic indium hexacyanoferrate (InHCF) were exploited for AIEFB. The AIEFB demonstrated advantages of a high average discharge potential (1.06 V), an attractive energy density of 62.8 mWh m−2 at a power density of 2433.8 mW m−2, a high transmittance modulation of 63% at 600 nm, and a distinct transparent-to-deep blue coloration during the Al-ion shuttling processes.

As a potential low-cost and high energy density energy storage technology, rechargeable Mg batteries (RMBs) have shown renaissance in the last decade, since the first realization of Mg electrochemical deposition nearly a century ago. Based on the Chervel phase Mo6S8 cathode, metal Mg anode, and organohaloaluminate electrolyte, the first RMB prototype was constructed, and more and more investigations are being committed to advance RMB system after that. In this review, we first overview the current status and challenges of Mg-ion techniques. Recent developments on critical components of RMBs, i.e., cathode and anode materials, are then analyzed systematically. Based on these understandings on the state-of-the-art RMBs, potential improving strategies are proposed to provide insights on future development of RMBs.

Vast bulk recombination of photo-generated carriers and sluggish surface oxygen evolution reaction (OER) kinetics severely hinder the development of photoelectrochemical water splitting. Herein, through constructing a vertically ordered ZnInS nanosheet array with an interior gradient energy band as photoanode, the bulk recombination of photogenerated carriers decreases greatly. We use the atomic layer deposition technology to introduce Fe-In-S clusters into the surface of photoanode. First-principles calculations and comprehensive characterizations indicate that these clusters effectively lower the electrochemical reaction barrier on the photoanode surface and promote the surface OER reaction kinetics through precisely affecting the second and third steps (forming processes of O* and OOH*) of the four-electron reaction. As a result, the optimal photoanode exhibits the high performance with a significantly enhanced photocurrent of 5.35 mA cm−2 at 1.23 VRHE and onset potential of 0.09 VRHE. Present results demonstrate a robust platform for controllable surface modification, nanofabrication, and carrier transport., The sluggish oxygen evolution reaction kinetics severely hinder the development of photoelectrochemical water splitting. Here the authors introduce Fe-In-S clusters onto the surface of photoanode to effectively lower the electrochemical reaction barrier.

Potassium-ion (K+) batteries (PIBs) show great potential in large-scale energy storage applications owing to their low-cost and high-operating voltage. However, the development of practical PIBs re...

Organic electrode materials (OEMs) can deliver remarkable battery performance for metal-ion batteries (MIBs) due to their unique molecular versatility, high flexibility, versatile structures, sustainable organic resources, and low environmental costs. Therefore, OEMs are promising, green alternatives to the traditional inorganic electrode materials used in state-of-the-art lithium-ion batteries. Before OEMs can be widely applied, some inherent issues, such as their low intrinsic electronic conductivity, significant solubility in electrolytes, and large volume change, must be addressed. In this review, the potential roles, energy storage mechanisms, existing challenges, and possible solutions to address these challenges by using molecular and morphological engineering are thoroughly summarized and discussed. Molecular engineering, such as grafting electron-withdrawing or electron-donating functional groups, increasing various redox-active sites, extending conductive networks, and increasing the degree of polymerization, can enhance the electrochemical performance, including its specific capacity (such as the voltage output and the charge transfer number), rate capability, and cycling stability. Morphological engineering facilitates the preparation of different dimensional OEMs (including 0D, 1D, 2D, and 3D OEMs) via bottom-up and top-down methods to enhance their electron/ion diffusion kinetics and stabilize their electrode structure. In summary, molecular and morphological engineering can offer practical paths for developing advanced OEMs that can be applied in next-generation rechargeable MIBs. Graphical abstract

Zinc-ion batteries (ZIBs) are promising alternative energy storage devices to lithium-ion batteries owing to the merits of large abundance, high theoretical capacity, and environmental friendliness. However, critical challenges including low working voltage (below 2 V), low energy density as well as dendrites formation during long cycling caused by aqueous ZIB systems still hinder their practical applications. Herein, a high-voltage Zn-graphite battery (ZGB) based on a non-zinc ion single-salt electrolyte (2.5 M LiPF6 in carbonate solvent) is developed. Moreover, we surprisingly found that Zn2+ is dissolved in the LiPF6 single-salt electrolyte during resting and discharging processes, thus enabling reversible Zn plating/stripping mechanism on the Zn foil anode in the ZGB over the voltage window of 1.0–3.1 V. As a result, the ZGB achieves long-term cycling performance with a capacity retention of ~100% for over 1200 cycles at 3C and high Coulombic efficiency of ~100% in 1.0–3.1 V with no dendrites formation. Moreover, the ZGB exhibits a high working voltage of up to 2.2 V, thus contributing to both high energy density (up to 210 Wh kg−1) and high power density (up to 1013 W kg−1), superior than most reported ZIBs.

Aluminum is a promising anode material for lithium-ion batteries owing to its high theoretical capacity, excellent conductivity, and natural abundance. An anomalous size effect was observed for micron-sized aluminum powder electrodes in this work. Experimental and theoretical investigations reveal that the insulating oxide surface layer is the underlying cause, which leads to poor electrical conductivity and limited capacity utilization when the particle is too small. Additionally, poor electrolyte wettability also accounts for the hindered reaction kinetics due to the weak polarity feature of the oxide layer. Surface grafting of polar amino groups was demonstrated to be an effective strategy to improve electrolyte wettability. The present work revealed the critical limitations and underlying mechanisms for the aluminum anode, which is crucial for its practical application. Our results are also valuable for other metallic anodes with similar issues.

Heterostructure construction of layered metal chalcogenides can boost their alkali-metal storage performance, where the charge transfer kinetics can be promoted by the built-in electric fields. However, these heterostructures usually undergo interface separation due to severe layer expansion, especially for large-size potassium accommodation, resulting in the deconstruction of heterostructures and battery performance fading. Herein, first a stable interface design strategy where two metal chalcogenides with totally different layer-morphologies are stacked to form large K

Alloy-type anodes are one of the most promising classes of next-generation anode materials due to their ultrahigh theoretical capacity (2-10 times that of graphite). However, current alloy-type anodes have several limitations: huge volume expansion, high tendency to fracture and disintegrate, an unstable solid-electrolyte interphase (SEI) layer, and low Coulombic efficiency. Efforts to overcome these challenges are ongoing. This Review details recent progress in the research of batteries based on alloy-type anodes and discusses the direction of their future development. We conclude that improvements in structural design, the introduction of a protective interface, and the selection of suitable electrolytes are the most effective ways to improve the performance of alloy-type anodes. Furthermore, future studies should direct more attention toward analyzing their synergistic promoting effect.

Redox-active organics are investigation hotspots for metal ion storage due to their structural diversity and redox reversibility. However, they are plagued by limited storage capacity, sluggish ion diffusion kinetics, and weak structural stability, especially for K+ ion storage. Herein, we firstly reported the lamellar tetrapotassium pyromellitic (K4 PM) with four active sites and large interlayer distance for K+ ion storage based on a design strategy, where organics are constructed with the small molecular mass, multiple active sites, fast ion diffusion channels, and rigid conjugated π bonds. The K4 PM electrode delivers a high capacity up to 292 mAh g-1 at 50 mA g-1 , among the best reported organics for K+ ion storage. Especially, it achieves an excellent rate capacity and long-term cycling stability with a capacity retention of ≈83 % after 1000 cycles. Incorporating in situ and ex-situ techniques, the K+ ion storage mechanism is revealed, where conjugated carboxyls are reversibly rearranged into enolates to stably store K+ ions. This work sheds light on the rational design and optimization of organic electrodes for efficient metal ion storage.

Dual-ion batteries (DIBs) are one of the promising candidates to meet the low-cost requirements of commercial applications because of their high working voltage, excellent safety, and environmental...

Dual-ion batteries (DIBs) inherently suffer from limited energy density due to insufficient anion storage capacity of typical graphite cathodes. Herein, we propose a new design strategy to effectively tackle this issue via employing locally ordered graphitized carbon (LOGC) cathodes. Quantum mechanical modeling suggests that strong anion-anion repulsion and severe expansion at the deep-charging stage raise the anion intercalation voltage, therefore only part of the theoretical anion storage sites in graphite is accessible. The LOGC interconnected with disordered carbon is predicted to weaken the interlaminar van der Waals interaction, while disordered carbons not only interconnect the dispersed nano-graphite but also partially buffer severe anion-anion repulsion and offer extra capacitive anion storage sites. As a proof-of-concept, ketjen black (KB) with the typical feature of LOGC is selected as a model cathode for a potassium-based DIB (KDIB). The KDIB delivers an unprecedentedly high specific capacity of 232 mAh g -1 at 50 mA g -1 , a good rate capability of 110 mAh g -1 at 2000 mA g -1 and excellent cycling stability of 1000 cycles without obvious capacity fading.

Anatase TiO2 is a promising anode material for sodium-ion batteries (SIBs). However, its sodium storage mechanisms in terms of crystal structure transformation during sodiation/de-sodiation processes are far from clear. Here, by analyzing the redox thermodynamics and kinetics under near-equilibrium states, we observe, for the first time, that upon Na-ion uptake, the anatase TiO2 undergoes a phase transition and then an irreversible crystal structure disintegration. Additionally, unlike previous theoretical studies which investigate only the two end points of the sodiation process (i.e., TiO2 and NaTiO2), we study the progressive crystal structure changes of anatase TiO2 upon step-by-step Na-ion uptake (NaxTiO2, x = 0.0625, 0.125, 0.25, 0.5, 0.75, and 1) for the first time. It is found that the anatase TiO2 goes through a thermodynamically unstable intermediate phase (Na0.25TiO2) before reaching crystalline NaTiO2, confirming the inevitable crystal structure disintegration during sodiation. These combined experimental and theoretical studies provide new insights into the sodium storage mechanisms of TiO2 and are expected to provide useful information for further improving the performance of TiO2-based anodes for SIB applications.

In nature, the oxygen reduction reaction (ORR) is catalyzed by cytochrome P450 (CYP) enzymes containing heme iron centers with an axial thiolate ligand (FeN