Super Hydrous Solvated Structure of Chaotropic Ca2+ Contributes Superior Anti-Freezing Aqueous Electrolytes and Stabilizes the Zn anode.

The further development of aqueous zinc (Zn)-ion batteries (AZIBs) is constrained by the high freezing points and the instability on Zn anodes. Current improvement strategies mainly focus on regulating hydrogen bond (HB) donors (H) of solvent water to disrupt HBs, while neglecting the environment of HB-acceptors (O). Herein, we propose a mechanism of chaotropic cation-regulated HB-acceptor via a "super hydrous solvated" structure. Chaotropic Ca2+ can form a solvated structure via competitively binding O atoms in H2O, effectively breaking the HBs among H2O molecules, thereby reducing the glass transition temperature of hybrid 1 mol L-1 (M) ZnCl2+4 M CaCl2 electrolyte (-113.2 °C). Meanwhile, the high hydratability of Ca2+ contributes to the water-poor solvated structure of Zn2+, suppressing side reactions and uneven Zn deposition. Benefiting from the anti-freezing electrolyte and high reversible Zn anode, the Zn||Pyrene-4,5,9,10-tetraone (PTO) batteries deliver an ultrahigh capacity of 183.9 mAh g-1 at 1.0 A g-1 over 1600-time stable cycling at -60 °C. This work presents a cheap and efficient aqueous electrolyte to simultaneously improve low-temperature performances and Zn stability, broadening the design concepts for antifreeze electrolytes.

"Anions-in-Colloid" Hydrated Deep Eutectic Electrolyte for High Reversible Zinc Metal Anodes.

Zn metal suffers from severe zinc dendrites, anion-related side reactions, hydrogen evolution reaction (HER) and narrow electrochemical stable window (ESW). Herein, an"anions-in-colloid" hydrated deep eutectic electrolyte (ACDE-3) is designed to improve the stability of zinc anode. The ACDE-3 reconfigures the hydrogen-bond (HB) network and regulates the solvation shell. More importantly, the hydroxyl-rich ß-cyclodextrins (ß-CDs) in ACDE-3 self-assemble into micelles, in which the steric effect between the adjacent ß-CDs restricts the movement of anions. This unique "anions-in-colloid" structure enables the eutectic system with a high Zn2+ transference number (tZn2+) of 0.84.  Thus, ACDE-3 inhibits the formation of dendrite, prevents the anion-involved side reactions, suppresses the HER, and enlarges the ESW to 2.32 V. The Zn//Zn symmetric cell delivers a long lifespan of 900 hours at 0.5 mAh cm-2, and the Zn//Cu half cells have a high average columbic efficiency (ACE) of 97.9% at 0.5 mAh cm-2 with a uniform and compact zinc deposition. When matched with a poly(1,5-naphthalenediamine) cathode, the full battery with a low negative/positive capacity ratio of 2 can still cycle steadily for 200 cycles at a current density of 1.0 A g-1. Additionally, this electrolyte can operative over a wide temperature range from -40 °C to 40 °C.

Surface-Oxygen-Rich Bi@C Nanoparticles for High-Efficiency Electroreduction of CO2 to Formate.

The electrochemical CO2 reduction reaction (CO2RR) is a promising strategy to alleviate excessive CO2 levels in the atmosphere and produce value-added feedstocks and fuels. However, the synthesis of high-efficiency and robust electrocatalysts remains a great challenge. This work reports the green preparation of surface-oxygen-rich carbon-nanorod-supported bismuth nanoparticles (SOR Bi@C NPs) for an efficient CO2RR toward formate. The resultant SOR Bi@C NPs catalyst displays a Faradaic efficiency of more than 91% for formate generation over a wide potential range of 440 mV. Ex situ XPS and XANES and in situ Raman spectroscopy demonstrate that the Bi-O/Bi (110) structure in the pristine SOR Bi@C NPs can remain stable during the CO2RR process. DFT calculations reveal that the Bi-O/Bi (110) structure can facilitate the formation of the *OCHO intermediate. This work provides an approach to the development of high-efficiency Bi-based catalysts for the CO2RR and offers a unique insight into the exploration of advanced electrocatalysts.

Hydrogen Bond Networks Stabilized High-Capacity Organic Cathode for Lithium-Ion Batteries.

High-capacity small organic materials are plagued by their high solubility. Here we proposed constructing hydrogen bond networks (HBN) via intermolecular hydrogen bonds to suppress the solubility of active material. The illustrated 2, 7- diamino-4, 5, 9, 10-tetraone (PTO-NH2 ) molecule with intermolecular hydrogen (H) bond between O in -C=O and H in -NH2 , which make PTO-NH2 presents transverse two-dimensional extension and longitudinal π-π stacking structure. In situ Fourier transform infrared spectroscopy (FTIR) has tracked the reversible evolution of H-bonds, further confirming the existence of HBN structure can stabilize the intermediate 2-electron reaction state. Therefore, PTO-NH2 with HBN structure has higher active site utilization (95 %), better cycle stability and rate performance. This study uncovers the H-bond effect and evolution during the electrochemical process and provides a strategy for materials design.

Bifunctional Interphase with Target-Distributed Desolvation Sites and Directionally Depositional Ion Flux for Sustainable Zinc Anode.

Aqueous zinc batteries (AZBs) feature high safety and low cost, but intricate anodic side reactions and dendrite growth severely restrict their commercialization. Herein, ethylenediaminetetraacetic acid (EDTA) grafted metal organic framework (MOF-E) is proposed as a dually-functional anodic interphase for sustainable Zn anode. Specifically, the target-distributed EDTA serves as an ion-trapped tentacle to accelerate the desolvation and ionic transport by powerful chemical coordination, while the MOFs offer suitable ionic channels to induce oriented deposition. As a result, MOF-E interphase fundamentally suppresses side reactions and guides horizontally arranged Zn deposition with (002) preferred orientations. The Zn|MOF-E@Cu cell exhibits a markedly improved Coulombic efficiency of 99.7 % over 2500 cycles, and the MOF-E@Zn|KVOH (KV12 O30-y ⋅ nH2 O) cell yields a steady circulation of 5000 cycles@90.47 % at 8 A g-1 .

Reversible Solid-Solid Conversion of Sulfurized Polyacrylonitrile Cathodes in Lithium-Sulfur Batteries by Weakly Solvating Ether Electrolytes.

Despite carbonate electrolytes exhibiting good stability to sulfurized polyacrylonitrile (SPAN), their chemical incompatibility with lithium (Li) metal anode leads to poor electrochemical performance of Li||SPAN full cells. While the SPAN employs conventional ether electrolytes that suffer from the shuttle effect, leading to rapid capacity fading. Here, we tailor a dilute electrolyte based on a low solvating power ether solvent that is both compatible with SPAN and Li metal. Unlike conventional ether electrolytes, the weakly solvating ether electrolyte enables SPAN to undergo reversibly "solid-solid" conversion. It features an anion-rich solvation structure that allows for the formation of a robust cathode electrolyte interphase on the SPAN, effectively blocking the dissolution of polysulfides into the bulk electrolyte and avoiding the shuttle effect. What's more, the unique electrolyte chemistry endowed Li ions with fast electroplating kinetics and induced high reversibility Li deposition/stripping process from 25 °C to -40 °C. Based on tailored electrolyte, Li||SPAN full cells matched with high loading SPAN cathodes (≈3.6 mAh cm-2 ) and 50 µm Li foil can operate stably over a wide range of temperatures. Additionally, Li||SPAN pouch cell under lean electrolyte and 5 % excess Li conditions can continuously operate stably for over a month.

Regulating Frozen Electrolyte Structure with Colloidal Dispersion for Low Temperature Aqueous Batteries.

Electrolyte freezing under low temperatures is a critical challenge for the development of aqueous batteries (ABs). While lowering the freezing point of the electrolyte has caught major research efforts, limited attention has been paid to the structural evolution during the electrolyte freezing process and regulating the frozen electrolyte structure for low temperature ABs. Here, we reveal the formation process of interconnected liquid regions for ion transport in frozen electrolytes with various in situ variable-temperature technologies. More importantly, the low-temperature performance of ABs was significantly improved with the colloidal electrolyte design using graphene oxide quantum dots (GOQDs), which effectively inhibits the growth of ice crystals and expands the interconnected liquid regions for facial ion transport. This work provides new insights and a promising strategy for the electrolyte design of low-temperature ABs.

Hydrogen Bond Shielding Effect for High-Performance Aqueous Zinc Ion Batteries.

Manganese oxides are highly desirable for the cathode of rechargeable aqueous zinc ion batteries (AZIBs) owing to their low cost and high abundance. However, the terrible structure stability of manganese oxide limits its practical application. Here, it is demonstrated that the hydrogen-bond shielding effect can improve the electrochemical performance of manganese oxide. Briefly, (NH4 )0.125 MnO2 (NHMO) is prepared by introducing NH4 + into the tunnel structure of α-MnO2 . The robust hydrogen bonds between N-H and host O atoms can stabilize the lattice structure of α-MnO2 and suppress the dissolution of Mn element. More importantly, it can also accelerate ions mobility kinetics by weakening the electrostatic interaction of host O atoms. Thus, the fabricated Zn||NHMO battery possesses impressive cycling life (99.5% of capacity retention over 10 000 cycles) and rate capability (109 mA h g-1 of discharge capacity at 6000 mA g-1 ). Comprehensive analyses reveal the essences of interfacial charge and bulk ions transfer. This finding opens new opportunities for the development of high-performance AZIBs.

Orthoquinone-Based Covalent Organic Frameworks with Ordered Channel Structures for Ultrahigh Performance Aqueous Zinc-Organic Batteries.

Elaborate molecular design on cathodes is of great importance for rechargeable aqueous zinc-organic batteries' performance elevation. Herein, we design a novel orthoquinone-based covalent organic framework with an ordered channel structures (BT-PTO COF) cathode for an ultrahigh performance aqueous zinc-organic battery. The ordered channel structure facilitates ions transfer and makes the COF follow a redox pseudocapacitance mechanism. Thus, it delivers a high reversible capacity of 225 mAh g-1 at 0.1 A g-1 and an exceptional long-term cyclability (retention rate 98.0 % at 5 A g-1 (≈18 C) after 10 000 cycles). Moreover, a co-insertion mechanism with Zn2+ first followed by two H+ is uncovered for the first time. Significantly, this co-insertion behaviour evolves to more H+ insertion routes at high current density and gives the COF ultra-fast kinetics thus it achieves unprecedented specific power of 184 kW kg-1 (COF) and a high energy density of 92.4 Wh kg-1 (COF) . Our work reports a superior organic material for zinc batteries and provides a design idea for future high-performance organic cathodes.

Optimize Lithium Deposition at Low Temperature by Weakly Solvating Power Solvent.

For lithium (Li) metal batteries, the decrease in operating temperature brings severe safety issues by more disordered Li deposition. Here, we demonstrate that the solvating power of solvent is closely related to the reversibility of the Li deposition/stripping process under low-temperature conditions. The electrolyte with weakly solvating power solvent shows lower desolvation energy, allowing for a uniform Li deposition morphology, as well as a high deposition/stripping efficiency (97.87 % at -40 °C). Based on a weakly solvating electrolyte, we further built a full cell by coupling the Li metal anode with a sulfurized polyacrylonitrile electrode at a low anode-to-cathode capacity ratio for steady cycling at -40 °C. Our results clarified the relationship between solvating power of solvent and Li deposition behavior at low temperatures.

Layered Ca0.28 MnO2 ·0.5H2 O as a High Performance Cathode for Aqueous Zinc-Ion Battery.

Aqueous zinc-ion batteries are promising candidates for grid-scale energy storage because of their intrinsic safety, low cost, and high energy intensity. However, lack of suitable cathode materials with both excellent rate performance and cycling stability hinders further practical application of aqueous zinc-ion batteries. Here, a nanoflake-self-assembled nanorod structure of Ca0.28 MnO2 ·0.5H2 O as Zn-insertion cathode material is designed. The Ca0.28 MnO2 ·0.5H2 O exhibits a reversible capacity of 298 mAh g-1 at 175 mA g-1 and long-term cycling stability over 5000 cycles with no obvious capacity fading, which indicates that the per-insertion of Ca ions and water can significantly improve reversible insertion/extraction stability of Zn2+ in Mn-based layered type material. Further, its charge storage mechanism, especially hydrogen ions, is elucidated. A comprehensive study suggests that the intercalation of hydrogen ions in the first discharge plat is controled by both pH value and type of anion of electrolyte. Further, it can stabilize the Ca0.28 MnO2 ·0.5H2 O cathode and facilitate the following insertion of Zn2+ in 1 m ZnSO4 /0.1 m MnSO4 electrolyte. This work can enlighten and promote the development of high-performance rechargeable aqueous zinc-ion batteries.

Aqueous Batteries Operated at -50 °C.

Insufficient ionic conductivity and freezing of the electrolyte are considered the main problems for electrochemical energy storage at low temperatures (low T). Here, an electrolyte with a freezing point lower than -130 °C is developed by using dimethyl sulfoxide (DMSO) as an additive with molar fraction of 0.3 to an aqueous solution of 2 m NaClO4 (2M-0.3 electrolyte). The 2M-0.3 electrolyte exhibits sufficient ionic conductivity of 0.11 mS cm-1 at -50 °C. The combination of spectroscopic investigations and molecular dynamics (MD) simulations reveal that hydrogen bonds are stably formed between DMSO and water molecules, facilitating the operation of the electrolyte at ultra-low T. Using DMSO as the electrolyte additive, the aqueous rechargeable alkali-ion batteries (AABs) can work well even at -50 °C. This work provides a simple and effective strategy to develop low T AABs.

High-Capacity and Ultrafast Na-Ion Storage of a Self-Supported 3D Porous Antimony Persulfide-Graphene Foam Architecture.

The key challenge for high-performance sodium-ion batteries is the exploitation of appropriate electrode materials with a long cycling stability and high rate capability. Here, we report Sb2S5 nanoparticles (∼5 nm) uniformly encapsulated in three-dimensional (3D) porous graphene foam, which were fabricated by a facile hydrothermal coassembly strategy, as a high-performance anode material for sodium-ion batteries. The as-prepared composite can be directly used as electrodes without adding a binder or current collector, exhibiting outstanding electrochemical performance with a high reversible capacity (845 mA h g-1 at 0.1 A g-1), ultralong cycling life (91.6% capacity retention after 300 cycles at 0.2 A g-1), and exceptional rate capability (525 mA h g-1 at 10.0 A g-1). This is attributed to fast Na+ ion diffusion from the ultrasmall nanoparticles and excellent electric transport between the active material and 3D porous graphene, which also provide an effective strategy for anchoring the nanoparticles. Experimental results show that the Sb2S5 undergoes a reversible reaction of Sb2S5 + 16Na ↔ 5Na2S + 2Na3Sb during sodiation/desodiation. Moreover, a full cell with Na3(VO0.5)2(PO4)2F2/C cathode and the as-prepared composite anode was assembled, displaying high output voltage (∼2.2 V) with a stable capacity of 828 mA h g-1 for anode material (with 100 cycles at 0.1 A g-1), showing the potential for practical application.

Capillary-Induced Ge Uniformly Distributed in N-Doped Carbon Nanotubes with Enhanced Li-Storage Performance.

Germanium (Ge) is a prospective anode material for lithium-ion batteries, as it possesses large theoretical capacity, outstanding lithium-ion diffusivity, and excellent electrical conductivity. Ge suffers from drastic capacity decay and poor rate performance, however, owing to its low electrical conductivity and huge volume expansion during cycling processes. Herein, a novel strategy has been developed to synthesize a Ge@N-doped carbon nanotubes (Ge@N-CNTs) composite with Ge nanoparticles uniformly distributed in the N-CNTs by using capillary action. This unique structure could effectively buffer large volume expansion. When evaluated as an anode material, the Ge@N-CNTs demonstrate enhanced cycling stability and excellent rate capabilities.

Nanostructured Mn-based oxides for electrochemical energy storage and conversion.

Batteries and supercapacitors as electrochemical energy storage and conversion devices are continuously serving for human life. The electrochemical performance of batteries and supercapacitors depends in large part on the active materials in electrodes. As an important family, Mn-based oxides have shown versatile applications in primary batteries, secondary batteries, metal-air batteries, and pseudocapacitors due to their high activity, high abundance, low price, and environmental friendliness. In order to meet future market demand, it is essential and urgent to make further improvements in energy and power densities of Mn-based electrode materials with the consideration of multiple electron reaction and low molecular weight of the active materials. Meanwhile, nanomaterials are favourable to achieve high performance by means of shortening the ionic diffusion length and providing large surface areas for electrode reactions. This article reviews the recent efforts made to apply nanostructured Mn-based oxides for batteries and pseudocapacitors. The influence of structure, morphology, and composition on electrochemical performance has been systematically summarized. Compared to bulk materials and notable metal catalysts, nanostructured Mn-based oxides can promote the thermodynamics and kinetics of the electrochemical reactions occurring at the solid-liquid or the solid-liquid-gas interface. In particular, nanostructured Mn-based oxides such as one-dimensional MnO2 nanostructures, MnO2-conductive matrix nanocomposites, concentration-gradient structured layered Li-rich Mn-based oxides, porous LiNi0.5Mn1.5O4 nanorods, core-shell structured LiMnSiO4@C nanocomposites, spinel-type Co-Mn-O nanoparticles, and perovskite-type CaMnO3 with micro-nano structures all display superior electrochemical performance. This review should shed light on the sustainable development of advanced batteries and pseudocapacitors with nanostructured Mn-based oxides.

Rechargeable Lithium-Iodine Batteries with Iodine/Nanoporous Carbon Cathode.

Rechargeable Li-iodine batteries are attractive electrochemical energy storage systems because iodine cathode provides the possibility of high energy density, wide abundance and low cost. However, the safety risk caused by low thermostability of iodine and the self-discharge reaction due to high solvency of iodine in aprotic solvent are target issues to be considered. Herein, we designed a room-temperature "solution-adsorption" method to prepare a thermostable iodine-carbon cathode by utilizing the strong adsorption of nanoporous carbon. Meanwhile, Li-iodine batteries constructed by the as-prepared cathode and ether-based electrolyte with the addition of LiNO3 showed negligible self-discharge reaction, high rate and long cycling performance. The reversible reactions of I2/LiI3 and LiI3/LiI in Li-iodine batteries were also proved with in situ Raman measurement. For the demonstration of application, soft-package batteries with Al-plastic film were assembled, displaying energy densities of 475 Wh/kg by mass of Li and iodine, and 136 Wh/kg by total mass of the battery. The use of nanoporous carbon to adsorb iodine at room-temperature represents a new and promising direction for realizing high-performance cathode for rechargeable Li-iodine batteries.

All-solid-state lithium organic battery with composite polymer electrolyte and pillar[5]quinone cathode.

The cathode capacity of common lithium ion batteries (LIBs) using inorganic electrodes and liquid electrolytes must be further improved. Alternatively, all-solid-state lithium batteries comprising the electrode of organic compounds can offer much higher capacity. Herein, we successfully fabricated an all-solid-state lithium battery based on organic pillar[5]quinone (C35H20O10) cathode and composite polymer electrolyte (CPE). The poly(methacrylate) (PMA)/poly(ethylene glycol) (PEG)-LiClO4-3 wt % SiO2 CPE has an optimum ionic conductivity of 0.26 mS cm(-1) at room temperature. Furthermore, pillar[5]quinine cathode in all-solid-state battery rendered an average operation voltage of ∼2.6 V and a high initial capacity of 418 mAh g(-1) with a stable cyclability (94.7% capacity retention after 50 cycles at 0.2C rate) through the reversible redox reactions of enolate/quinonid carbonyl groups, showing favorable prospect for the device application with high capacity.

Organic Li4C8H2O6 nanosheets for lithium-ion batteries.

Organic tetralithium salts of 2,5-dihydroxyterephthalic acid (Li4C8H2O6) with the morphologies of bulk, nanoparticles, and nanosheets have been investigated as the active materials of either positive or negative electrode of rechargeable lithium-ion batteries. It is demonstrated that, in the electrolyte of LiPF6 dissolved in ethylene carbonate (EC) and dimethyl carbonate (DMC), reversible two-Li-ion electrochemical reactions are taking place with redox Li4C8H2O6/Li2C8H2O6 at ~2.6 V for a positive electrode and Li4C8H2O6/Li6C8H2O6 at ~0.8 V for a negative electrode, respectively. In the observed system, the electrochemical performance of high to low order is nanosheets > nanoparticles > bulk. Remarkably, Li4C8H2O6 nanosheets show the discharge capacities of 223 and 145 mAh g(-1) at 0.1 and 5 C rates, respectively. A capacity retention of 95% is sustained after 50 cycles at 0.1 C rate charge/discharge and room temperature. Moreover, charging the symmetrical cells with Li4C8H2O6 nanosheets as the initial active materials of both positive and negative electrodes produces all-organic LIBs with an average operation voltage of 1.8 V and an energy density of about 130 Wh kg(-1), enlightening the design and application of organic Li-reservoir compounds with nanostructures for all organic LIBs.

MoS2 nanoflowers with expanded interlayers as high-performance anodes for sodium-ion batteries.

MoS2 nanoflowers with expanded interlayer spacing of the (002) plane were synthesized and used as high-performance anode in Na-ion batteries. By controlling the cut-off voltage to the range of 0.4-3 V, an intercalation mechanism rather than a conversion reaction is taking place. The MoS2 nanoflower electrode shows high discharge capacities of 350 mAh g(-1) at 0.05 A g(-1) , 300 mAh g(-1) at 1 A g(-1) , and 195 mAh g(-1) at 10 A g(-1) . An initial capacity increase with cycling is caused by peeling off MoS2 layers, which produces more active sites for Na(+) storage. The stripping of MoS2 layers occurring in charge/discharge cycling contributes to the enhanced kinetics and low energy barrier for the intercalation of Na(+) ions. The electrochemical reaction is mainly controlled by the capacitive process, which facilitates the high-rate capability. Therefore, MoS2 nanoflowers with expanded interlayers hold promise for rechargeable Na-ion batteries.