Designing a Magnesium/Sodium Hybrid Battery Using Hierarchical Iron Selenide Architecture as Cathode Material and Modified Dual-Ion Salts in Ether as Electrolyte.

We developed a magnesium/sodium (Mg/Na) hybrid battery using a hierarchical disk-whisker FeSe2 architecture (HD-FeSe2) as the cathode material and a modified dual-ion electrolyte. The polarizable Se2- anion reduced the Mg2+ migration barrier, and the 3D configuration possessed a large surface area, which facilitated both Mg2+/Na+ cation diffusion and electron transport. The dual-ion salts with NaTFSI in ether reduced the Mg plating/stripping overvoltage in a symmetric cell. The hybrid battery exhibited an energy density of 260.9 Wh kg-1 and a power density of 600.8 W kg-1 at 0.2 A g-1. It showed a capacity retention of 154 mAh g-1 and a Coulombic efficiency of over 99.5% under 1.0 A g-1 after 800 long cycles. The battery also displayed outstanding temperature tolerance. The findings of 3D architecture as cathode material and hybrid electrolyte provide a pathway to design a highly reliable Mg/Na hybrid battery.

A Room-Temperature Self-Healing Liquid Metal-Infilled Microcapsule Driven by Coaxial Flow Focusing for High-Performance Lithium-Ion Battery Anode.

Liquid metals have attracted a lot of attention as self-healing materials in many fields. However, their applications in secondary batteries are challenged by electrode failure and side reactions due to the drastic volume changes during the "liquid-solid-liquid" transition. Herein, a simple encapsulated, mass-producible method is developed to prepare room-temperature liquid metal-infilled microcapsules (LMMs) with highly conductive carbon shells as anodes for lithium-ion batteries. Due to the reasonably designed voids in the microcapsule, the liquid metal particles (LMPs) can expand freely without damaging the electrode structure. The LMMs-based anodes exhibit superior capacity of rete-performance and ultra-long cycling stability remaining 413 mAh g-1 after 5000 cycles at 5.0 A g-1. Ex situ X-ray powder diffraction (XRD) patterns and electrochemical impedance spectroscopy (EIS) reveal that the LMMs anode displays a stable alloying/de-alloying mechanism. DFT calculations validate the electronic structure and stability of the room-temperature LMMs system. These findings will bring some new opportunities to develop high-performance battery systems.

A Temperature-Tolerant Magnesium-Ion Battery Using Ball Cactus-like MgV2O4 as High-Performance Cathode.

Safe and high-performance secondary batteries using for all-climate conditions with different temperatures are highly required. Here, we develop a three-dimensional ball cactus-like MgV2O4 as cathode material for magnesium-ion (Mg-ion) batteries. After cycling 300 times, the capacity maintains 111.7 mAh g-1, while Coulombic efficiency stabilizes at about 100 %. Under temperatures of 45 °C and -5 °C, the capacities remain stable after 200 cycles. After three rounds of rate-performance tests, the capacity keeps quite stable. It is ascribed to the ball cactus-like morphology buffers the volumetric change during Mg2+ insertion/extraction, and provides sufficient pathways for ion diffusion, which has been verified by constant-current intermittent titration technology. It is believed that the good performance enables the Mg-ion batteries to have a all-climate capability.

Long-Cycling-Life Sodium-Ion Battery Using Binary Metal Sulfide Hybrid Nanocages as Anode.

Due to the relatively high capacity and lower cost, transition metal sulfides (TMS) as anode show promising potential in sodium-ion batteries (SIBs). Herein, a binary metal sulfide hybrid consisting of carbon encapsulated CoS/Cu2 S nanocages (CoS/Cu2 S@C-NC) is constructed. The interlocked hetero-architecture filled with conductive carbon accelerates the Na+ /e- transfer, thus leading to improved electrochemical kinetics. Also the protective carbon layer can provide better volume accommondation upon charging/discharging. As a result, the battery with CoS/Cu2 S@C-NC as anode displays a high capacity of 435.3 mAh g-1 after 1000 cycles at 2.0 A g-1 (≈3.4 C). Under a higher rate of 10.0 A g-1 (≈17 C), a capacity of as high as 347.2 mAh g-1 is still remained after long 2300 cycles. The capacity decay per cycle is only 0.017%. The battery also exhibits a better temperature tolerance at 50 and -5 °C. A low internal impedance analyzed by X-ray diffraction patterns and galvanostatic intermittent titration technique, narrow band gap, and high density of states obtained by first-principle calculations of the binary sulfides, ensure the rapid Na+ /e- transport. The long-cycling-life SIB using binary metal sulfide hybrid nanocages as anode shows promising applications in versatile electronic devices.

A Foldable Aqueous Zn-Ion Battery with Gear-Structured Composite as Freestanding Cathode.

A foldable battery with high flexibility provides great potential in various wearable electronic devices for health and fitness tracking, chronic disease management, performance monitoring, navigation tracking, and portable gears for soldiers. We report a highly flexible, self-healing Zn-ion battery with a free-standing cathode that is composed of a 3D gear-like NH4 V4 O10 @C composite on carbon paper. The battery retained a capacity of up to 102.4 mAh g-1 even after being folded 60 times with a high angle of 180°. An aqueous hydrogel consisting polyvinyl alcohol, glycerin and Zn(CF3 SO3 )2 was used as electrolyte, which showed as high as 580 % tensile strain under a loading weight of 78 N. The battery exhibited a better capacity retention of over 100 mAh g-1 and Coulombic efficiency of over 99.8 % after cutting and twisting to 90°, thereby indicating a great self-healing performance. The gear-like geometry greatly improved the volume accommodation due to the increased interval space between the blades and the outward configuration. Meanwhile the Zn2+ ionic conductivity was improved by rapid re-binding of many existing hydroxy groups from the electrolyte and the enhanced contact surface area and diffusion route from the cathode material. The highly flexible, safe aqueous Zn-ion battery opens a practical way to power various carry-on electronics under mechanical agitation.

A Pyramidal Metal-Organic Frameworks-Derived FeP@CoP Aluminium-Ion Battery Cathode Displaying Low-Temperature Tolerance and Fast Electron Transfer Kinetics.

Anhui Provincial Engineering Laboratory for Engineering appropriate cathode materials is significant for the development of high-performance aluminum-ion (Al-ion) batteries. Here, a pyramidal metal-organic frameworks (MOFs)-derived FeP@CoP composite was developed as cathode, which exhibits good stability and high capacity. FeP@CoP cathode maintains a high capacity of 168 mAh g-1 after 200 cycles, and displays a stable rate-performance at both room and low temperatures of -10 °C. After three rounds of rate-performance cycling, the FeP@CoP composite recovers 178.2 mAh g-1 at 0.3 A g-1 . Moreover, density functional theory (DFT) calculations verify improved electron-transfer kinetics with narrowed band gap and enhanced density of states. These findings inspire a broad set of studies on MOFs-derived composites for high-performance secondary batteries.

A Polysulfides-Confined All-in-One Porous Microcapsule Lithium-Sulfur Battery Cathode.

Developing emerging materials for high energy-density lithium-sulfur (Li-S) batteries is of great significance to suppress the shuttle effect of polysulfides and to accommodate the volumetric change of sulfur. Here, a novel porous microcapsule system containing a carbon nanotubes/tin dioxide quantum dots/S (CNTs/QDs/S) composite core and a porous shell prepared through a liquid-driven coaxial microfluidic method as Li-S battery cathode is developed. The encapsulated CNTs in the microcapsules provide pathways for electron transport; SnO2 QDs on CNTs immobilize the polysulfides by strong adsorption, which is verified by using density functional theory calculations on binding energies. The porous shell of the microcapsule is beneficial for ion diffusion and electrolyte penetration. The void inside the microcapsule accommodates the volumetric change of sulfur. The Li-S battery based on the porous CNTs/QDs/S microcapsules displays a high capacity of 1025 mAh g-1 after 100 cycles at 0.1 C. When the sulfur loading is 2.03 mg cm-2 , the battery shows a stable cycling life of 700 cycles, a Coulombic efficiency exceeding 99.9%, a recoverable rate-performance during repeated tests, and a good temperature tolerance at both -5 and 45 °C, which indicates a potential for applications at different conditions.

A novel free-standing metal organic frameworks-derived cobalt sulfide polyhedron array for shuttle effect suppressive lithium-sulfur batteries.

Metal-organic-frameworks-derived nanostructures have received broad attention for secondary batteries. However, many strategies focus on the preparation of dispersive materials, which need complicated steps and some additives for making electrodes of batteries. Here, we develop a novel free-standing Co9S8polyhedron array derived from ZIF-67, which grows on a three-dimensional carbon cloth for lithium-sulfur (Li-S) battery. The polar Co9S8provides strong chemical binding to immobilize polysulfides, which enables efficiently suppressing of the shuttle effect. The free-standing S@Co9S8polyhedron array-based cathode exhibits ultrahigh capacity of 1079 mAh g-1after cycling 100 times at 0.1 C, and long cycling life of 500 cycles at 1 C, recoverable rate-performance and good temperature tolerance. Furthermore, the adsorption energies towards polysulfides are investigated by using density functional theory calculations, which display a strong binding with polysulfides.

A novel spring-structured coaxial hierarchical SiO2@Co3O4 nanowire as a lithium-ion battery anode and its in situ real-time lithiation.

High capacity and stable anodes are demanded since the current graphite-based anode does not meet the high-performance requirements of emerging Li-ion battery systems. Herein, we present a novel spring-shaped hierarchical SiO2@Co3O4 nanowire composite, which exhibits good Li-storage performance. The special structure is able to effectively accommodate the change in structure during charge-discharge, and the coaxial hierarchical morphology enables rapid Li+ ion and electron transfer. The spring-shaped SiO2@Co3O4 anode exhibits a capacity of 770 mAh g-1, along with a high Coulombic efficiency of 99.8% after 400 cycles. A stable rate performance even after three rounds of measurements is also achievable. In addition, the real-time lithiation of the SiO2@Co3O4 composite is investigated through an in situ transmission electron microscopy technology, which demonstrates the stable structure of the spring-shaped SiO2@Co3O4 composite during the rapid lithiation process.

A novel silicon nanoparticles-infilled capsule prepared by an oil-in-water emulsion strategy for high-performance Li-ion battery anodes.

Conventional approaches for preparing yolk-shell nanostructures require complicated procedures such as multi-step coatings and template removal. Herein, we present a new and general strategy for making yolk-shell nanocomposites based on an oil-in-water emulsion system. As a demonstrating case, silicon nanoparticles were dispersed in an oil phase which was in an oil-in-water emulsion; then the oil/water interface was in-situ polymerized to form microcapsules. After carbonization, the shell of microcapsules was formed. The Li-ion battery anodes based on the microcapsules exhibit a good electrochemical performance including stable capacity and high rate-performance. The capacity remains 1100 mAh g-1 after 500 cycles at a current density of 1.9 A g-1, along with a Coulombic efficiency of ≈ 99.9%. In addition, the method presented here is general, which is applicable for the synthesis of many yolk shell-structured nanocomposites.

A novel sulfur@void@hydrogel yolk-shell particle with a high sulfur content for volume-accommodable and polysulfide-adsorptive lithium-sulfur battery cathodes.

High-energy-density secondary batteries are required for many applications such as electric vehicles. Lithium-sulfur (Li-S) batteries are receiving broad attention because of their high theoretical energy density. However, the large volume change of sulfur during cycling, poor conductivity, and the shuttle effect of sulfides severely restrict the Li-storage performance of Li-S batteries. Herein, we present a novel core-shell nanocomposite consisting of a sulfur core and a hydrogel polypyrrole (PPy) shell, enabling an ultra-high sulfur content of about 98.4% within the composite, which greatly exceeds many other conventional composites obtained by coating sulfur onto some hosts. In addition, the void inside the core-shell structure effectively accommodates the volume change; the conductive PPy shell improves the conductivity of the composite; and PPy is able to adsorb polysulfides, suppressing the shuttle effect. After cycling for 200 cycles, the prepared S@void@PPy composite retains a stable capacity of 650 mAh g-1, which is higher than the bare sulfur particles. The composite also exhibits a fast Li ion diffusion coefficient. Furthermore, the density functional theory calculations show the PPy shell is able to adsorb polysulfides efficiently, with a large adsorption energy and charge density transfer.

A quasi-solid-state self-healing flexible zinc-ion battery using a dual-crosslinked hybrid hydrogel as the electrolyte and Prussian blue analogue as the cathode material.

Due to their excellent safety and lower cost, aqueous Zn-ion batteries (AZIBs) have garnered extensive interest among various energy-storage systems. Here we report a quasi-solid-state self-healing AZIB by using a hybrid hydrogel which consists of dual-crosslinked polyacrylamide and polyvinyl alcohol as a flexible electrolyte and a cobalt hexacyanoferrate (K3.24Co3[Fe(CN)6]2·12.6H2O) Prussian blue analogue as the cathode material. The obtained hybrid hydrogel showed a superhigh fracture strain of up to 1490%, which was almost 15 times higher than that of the original size. Due to the fast formation of hydrogen bonds, the self-healed hydrogel from two pieces still displayed 1165% strain upon failure. As a result, the self-healed battery delivered stable capacities of 119.1, 108.6 and 103.0 mA h g-1 even after being completely cut into 2, 3 and 4 pieces, respectively. The battery capacity recovery rates for each bending cycle exceeded 99.5%, 99.8%, 98.6% and 98.9% during four continuous bending cycles (30 times bending at 90° for each cycle), which indicates outstanding flexibility and self-healing capability. In parallel, the hydrogel electrolyte displayed a broader electrochemically stable window of 3.37 V due to the suppression of water splitting and low overvoltage during the 500 h cycling in a symmetric cell. Zinc dendrites were also suppressed as evidenced in symmetric cell measurements. The assembled AZIB exhibited an initial capacity of 176 mA h g-1 upon vertical bending. The battery showed a reliable capacity of 140.7 mA h g-1 at 0.2 A g-1 after 100 cycles along with a coulombic efficiency of >99%. A reliable capacity of nearly 100 mA h g-1 was retained after 300 cycles at 1.0 A g-1. The highly flexible and self-healing AZIB demonstrates great potential in various wearable electronic devices.

SnS2 quantum dots-coated VO2@carbon nanorods for secondary battery displaying high capacity and rate-performance.

Electrode materials optimization is one of the keys to improving the energy storage characteristics of secondary batteries. Herein, a VO2@carbon@SnS2 composite is developed by coating SnS2 quantum dots (QDs) on lamellar VO2@carbon nanorods, yielding a high-performance aluminum-ion battery cathode. SnS2 QDs embedded in VO2@carbon accelerate electron transport, while the in situ coating of carbon improves cycling stability. When cycling at 0.5 A g-1, capacity is maintained at 157.6 mA h g-1 after 200 cycles. Even at 1.0 A g-1, the cathode can be stably cycled 1000 times. Capacity remains at 176.3 mA h g-1 and coulombic efficiency is 99.1% at temperatures below -10 °C after 100 cycles. These findings provide new ideas for the development of QD-modified composites for application in secondary batteries.

Ultralong-life and high-capacity magnesium/sodium hybrid-ion battery using a ternary CoSe/NiSe2/CuSe2 cathode and dual-ion electrolyte.

An ultrahigh-performance magnesium/sodium hybrid-ion battery (MNHB) is developed using ternary CoSe/NiSe2/CuSe2 (CNCS) "micro-flowers" as cathode materials, working with a coordinative [Mg2Cl2][AlCl4]2 and bis(trifluoroethylsulfonyl)imide anionic sodium salt in triglyme electrolyte. After 2000 cycles at 2.0 A g-1, the MNHB shows a stable capacity of 115.5 mA h g-1 and a high Coulombic efficiency exceeding 99.8%. The battery shows very rapid charging, and good stability in extreme environments, providing new opportunities to develop other hybrid-ion systems.

A blade-like CoZn metal organic framework-based flexible quasi-solid Zn-ion battery.

Wearable flexible electronics has become more and more significant and popular in daily life. Here, a flexible quasi-solid Zn-ion battery consisting of CoZn-metal organic frameworks (MOFs) grown on carbon cloth as an all-in-one cathode working with a hydrogel electrolyte is developed. CoZn MOFs display a blade-like morphology, which is significant for rapid transfer of ions and electrons. The battery bending at angles from 0° to 180° displays high capacities and good capacity retention, and the capacity remains stable as the flexible battery twists to 90°. In addition, the capacity exceeds 101.4 mA h g-1 as the battery is folded to 180° for 30 times, which indicates that the developed Zn-ion batteries would be applicable for a large variety of wearable devices such as foldable cellphones and pads.

A nanowire-on-microrod polyaniline@FeS2 hybrid as the cathode in high-performance Al-ion batteries.

A nanowire-on-microrod structured polyaniline (PANI)@FeS2 hybrid was developed via a facile metal-organic framework (MOF)-derived chemical method. The in situ grown PANI nanowires on the surface of pyramidal FeS2 microrods displayed better mechanical flexibility and improved Al-storage performance. The PANI nanowires not only enhanced electron transfer during the electrochemical reaction, but also accommodated the volume expansion of FeS2 during discharge. The PANI@FeS2 hybrid as the cathode in AIBs delivered a reliable battery capacity of 152.8 mA h g-1 along with a Coulombic efficiency of >96.5% after 500 cycles at a current density of 1.5 A g-1. In addition, a high capacity retention of 160.2 mA h g-1 after 150 cycles at 0.5 A g-1 at -10 °C was achieved. These findings provide a feasible strategy by constructing a nanowire-on-microrod hybrid that can be applied in high-performance secondary batteries.

A nanowire-assembled Co3S4/Cu2S@carbon binary metal sulfide hybrid as a sodium-ion battery anode displaying high capacity and recoverable rate-performance.

A binary metal sulfide hybrid consisting of nanowire-assembled and polypyrrole-coated Co3S4/Cu2S spheres after nitrogen-doped carbon coating (Co3S4/Cu2S@NC) is developed as an anode, which displays a capacity exceeding 412.3 mA h g-1 after 550 cycles under 1.0 A g-1. Recoverable rate-performance and good temperature tolerance under 50 °C and -10 °C are achievable; a full cell delivers 339.5 mA h g-1, indicating promising potential for applications in various conditions.

A single-crystalline Co3O4 nanoparticle-assembled three-dimensional chain as an ultra-stable magnesium-ion battery cathode at different temperatures.

Engineering optimal cathode materials is significant for developing stable magnesium-ion (Mg-ion) batteries. Here, we present a single-crystalline Co3O4 nanoparticle-chain three-dimensional (3D) micro/nanostructure as an Mg-ion battery cathode. The hierarchical morphology is composed of radial nanochains self-assembled by single-crystalline nanoparticles, thus significantly facilitating the transfer of electrons and ions. 3D single-crystalline Co3O4 as an Mg-ion battery cathode displays a stable capacity of 111.7 mA h g-1 after 200 cycles with a decay rate per cycle as low as 0.037%. After four rounds of testing, the rate performance remains stable with a tiny decrease from 125.94 to 124.78 mA h g-1. At temperatures of 45 °C and -5 °C, the cathode still displays good stability and rate-performance. Galvanostatic intermittent titration technique (GITT) results verify a low energy barrier of the Co3O4 cathode. It is expected that the single-crystalline nanoparticle-assembled 3D structure and the stable Mg-storage performance will find broad applications for developing other stable energy-storage materials and their batteries.

A foldable self-healing rocking chair zinc-ion battery using a three-dimensional zinc metal-free anode.

We developed H2Ti5O11·xH2O on carbon cloth (HTO·xH2O/CC) as a binder-free Zn metal-free anode. This 'rocking chair' battery incorporated a ZnMn2O4/CC cathode, HTO·xH2O/CC anode, and a polyacrylamide-based electrolyte, and exhibited satisfactory flexibility and self-healing. It displayed recoverable capacities after four repetitions of cutting and healing, indicating a potential using as a foldable and wearable battery.

A metal organic framework-derived octahedral Cu1.95S@CoS2 for secondary batteries displaying long cycle life and stable temperature tolerance.

Low-cost and safe batteries are considered to be promising energy-storage systems. Here, a metal organic framework (MOF)-derived octahedral Cu1.95S@CoS2 composite is developed as a high-performance cathode of aluminium-ion (Al-ion) batteries. CoS2 nanoparticles on Cu1.95S provide active sites, making AlCl4- intercalation/deintercalation highly reversible, and reducing polarization. Cycling at 0.5 A g-1, Cu1.95S@CoS2 maintains stable capacities of 136.6 and 122.4 mA h g-1 after 200 cycles at room temperature and -10 °C, respectively. Stable rate-performance is also achieved. These findings will accelerate the application of Al-ion batteries and MOF-derived energy-storage composites.