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Rechargeable sodium-based batteries are receiving increasing attention as large-scale energy storage systems, because of the abundant resource and low cost of sodium. The widely used nonaqueous liq...

Liquid metal batteries are regarded as potential electrochemical systems for stationary energy storage. Currently, all reported liquid metal batteries need to be operated at temperatures above 240 °C to maintain the metallic electrodes in a molten state. Here, an unprecedented room-temperature liquid metal battery employing a sodium-potassium (Na-K) alloy anode and gallium (Ga)-based alloy cathodes is demonstrated. Compared with lead (Pb)- and mercury (Hg)-based liquid metal electrodes, the nontoxic Ga alloys maintain high environmental benignity. On the basis of improved wetting and stabilized interfacial chemistry, such liquid metal batteries deliver stable cycling performance and negligible self-discharge. Different from the conventional interphase between a typical solid electrode and a liquid electrolyte, the interphase between a liquid metal and a liquid electrolyte is directly visualized via advanced 3D chemical analysis. Insights into this new type of liquid electrode/electrolyte interphase reveal its important role in regulating charge carriers and stabilizing the redox chemistry. With facile cell fabrication, simplified battery structures, high safety, and low maintenance costs, room-temperature liquid metal batteries not only show great prospects for widespread applications, but also offer a pathway toward developing innovative energy-storage devices beyond conventional solid-state batteries or high-temperature batteries.

Sodium batteries have been regarded as promising candidates for large-scale energy storage application, provided cathode hosts with high energy density and long cycle life can be found. Herein, we report NASICON-structured Na3MnZr(PO4)3 as a cathode for sodium batteries that exhibits an electrochemical performance superior to those of other manganese phosphate cathodes reported in the literature. Both the Mn4+/Mn3+ and Mn3+/Mn2+ redox couples are reversibly accessed in Na3MnZr(PO4)3, providing high discharge voltage plateaus at 4.0 and 3.5 V, respectively. A high discharge capacity of 105 mAh g-1 was obtained from Na3MnZr(PO4)3 with a small variation of lattice parameters and a small volume change on extraction of two Na+ ions per formula unit. Moreover, Na3MnZr(PO4)3 exhibits an excellent cycling stability, retaining 91% of the initial capacity after 500 charge/discharge cycles at 0.5 C rate. On the basis of structural analysis and density functional theory calculations, we have proposed a detailed desodiation pathway from Na3MnZr(PO4)3 where Mn and Zr are disordered within the structure. We further show that the cooperative Jahn-Teller distortion of Mn3+ is suppressed in the cathode and that Na2MnZr(PO4)3 is a stable phase.

A safe, rechargeable potassium battery of high energy density and excellent cycling stability has been developed. The anion component of the electrolyte salt is inserted into a polyaniline cathode upon charging and extracted from it during discharging while the K+ ion of the KPF6 salt is plated/stripped on the potassium-metal anode. The use of a p-type polymer cathode increases the cell voltage. By replacing the organic-liquid electrolyte in a glass-fiber separator with a polymer-gel electrolyte of cross-linked poly(methyl methacrylate), a dendrite-free potassium anode can be plated/stripped, and the electrode/electrolyte interface is stabilized. The potassium anode wets the polymer, and the cross-linked architecture provides small pores of adjustable sizes to stabilize a solid-electrolyte interphase formed at the anode/electrolyte interface. This alternative electrolyte/cathode strategy offers a promising new approach to low-cost potassium batteries for the stationary storage of electric power.

Summary The cycling performance at 60°C of a Na 2 MnFe(CN) 6 /Na cell with a ceramic solid electrolyte is compared with that of a cell with an organic-liquid electrolyte operating at room temperature. Analysis of the electrode-electrolyte interfaces after charge-discharge cycling showed that a sodium-metal anode that wets the solid electrolyte can be plated and stripped reversibly dendrite free and that the dissolution of the cyano-perovskite Na 2 MnFe(CN) 6 cathode that occurs with an organic-liquid electrolyte is eliminated with the utilization of the solid electrolyte. This demonstration indicates that a high-energy-density and low-cost sodium rechargeable battery can be competitive for large-scale electric energy storage where both the anode and cathode problems are solved in an all-solid-state battery.

Aluminum has long been regarded as a promising anode for energy storage because of its high energy density and low cost, but its application is hindered by the inability of cathodes to provide reversible Al3+ insertion. In contrast, we show how the use of Al as cathode enables a rechargeable high-energy battery. The battery comprises a molten sodium anolyte and a molten NaAl2Cl7 catholyte, separated by a NaSICON solid Na+ electrolyte. It is operated at 200 °C to overcome the ceramic separator kinetics and to keep sodium and NaAl2Cl7 in the molten state. Because of the simple composition and trivalence of Al, the sodium anolyte and NaAl2Cl7 catholyte together show a high energy density of 366 Wh kg–1, although its voltage is only about 1.55 V and only 60% of the capacity can be realized. The high energy density, low-cost, and internal safety make this new cell chemistry applicable to the large-scale energy storage market.

The development of all-solid-state rechargeable batteries is plagued by a large interfacial resistance between a solid cathode and a solid electrolyte that increases with each charge–discharge cycle. The introduction of a plastic–crystal electrolyte interphase between a solid electrolyte and solid cathode particles reduces the interfacial resistance, increases the cycle life, and allows a high rate performance. Comparison of solid-state sodium cells with 1) solid electrolyte Na3Zr2(Si2PO4) particles versus 2) plastic–crystal electrolyte in the cathode composites shows that the former suffers from a huge irreversible capacity loss on cycling whereas the latter exhibits a dramatically improved electrochemical performance with retention of capacity for over 100 cycles and cycling at 5 C rate. The application of a plastic–crystal electrolyte interphase between a solid electrolyte and a solid cathode may be extended to other all-solid-state battery cells.

Potassium has as rich an abundance as sodium in the earth, but the development of a K-ion battery is lagging behind because of the higher mass and larger ionic size of K+ than that of Li+ and Na+, which makes it difficult to identify a high-voltage and high-capacity intercalation cathode host. Here we propose a cyanoperovskite KxMnFe(CN)6 (0 ≤ x ≤ 2) as a potassium cathode: high-spin MnIII/MnII and low-spin FeIII/FeII couples have similar energies and exhibit two close plateaus centered at 3.6 V; two active K+ per formula unit enable a theoretical specific capacity of 156 mAh g–1; Mn and Fe are the two most-desired transition metals for electrodes because they are cheap and environmental friendly. As a powder prepared by an inexpensive precipitation method, the cathode delivers a specific capacity of 142 mAh g–1. The observed voltage, capacity, and its low cost make it competitive in large-scale electricity storage applications.

SnSb nanoparticles are dispersed in carbon nanofibers by electrospinning technology and different SnSb precursors, including Sn0.92Sb0.08O2.04 nanoparticles, Sn(CH3COO)2/Sb(CH3COO)3, and SnCl4·5H2O/SbCl3, are used to tune the morphology of the resultant SnSb/C nanofibers. Porous SnSb/C nanofibers are formed during carbonization Sn0.92Sb0.08O2.04 nanoparticles and Sn(CH3COO)2/Sb(CH3COO)3 are used as precursors of SnSb, while solid nanofibers are observed with SnCl4·5H2O/SbCl3 as the precursor indicating the formation mechanism is closely related to the properties of SnSb precursors. Excellent cycling preference (99% capacity retention after 200 cycles) and high coulombic efficiency (above 99% after 10 cycles) are obtained for the SnSb/C nanofibers using Sn0.92Sb0.08O2.04 as precursor, due to its high surface area and stable SnSb/C structure. It is demonstrated that the uniquely designed composite nanofiber structure with excellent lithium storage performance can be realized simply by selecting precursors with appropriate dissolution and decomposition properties.

The practical use of lithium-sulfur batteries for the next-generation energy storage, especially the automobiles, was hindered by low electronic conductivity of sulfur and the resulting poor rate capabilities. Here, we report a sulfur-carbon composite by confining S into a graphene sandwiched in mesoporous carbon nanosheets with a two-dimensional ultrathin morphology, suitable mesopore size and large pore volume, and excellent electronic conductivity. Serving as cathode material for a Li-S battery, the elaborately designed S/C composite leads to "kinetically stable" transmissions of Li ions and electrons, triggering a stable electrochemistry and a record-breaking rate performance. In this way, the S/C composite has been proved a promising cathode material for high-rate Li-S batteries targeted at automobile storage.

NASICON (Na+ super ionic conductor) structures of NaxMV(PO4)3 (M = Mn, Fe, Ni) were prepared, characterized by aberration-corrected STEM and synchrotron radiation, and demonstrated to be durable cathode materials for rechargeable sodium-ion batteries. In Na4MnV(PO4)3, two redox couples of Mn3+/Mn2+ and V4+/V3+ are accessed with two voltage plateaus located at 3.6 and 3.3 V and a capacity of 101 mAh g–1 at 1 C. Furthermore, the Na4MnV(PO4)3 cathode delivers a high initial efficiency of 97%, long durability over 1000 cycles, and good rate performance to 10 C. The robust framework structure and stable electrochemical performance makes it a reliable cathode materials for sodium-ion batteries.

Sodium batteries have been regarded as promising candidates for large-scale energy storage application, provided cathode hosts with high energy density and long cycle life can be found. Herein, we report NASICON-structured Na

The Na-K alloy is a liquid at 25 °C over a large compositional range. The liquid alloy is also immiscible in the organic-liquid electrolytes of an alkali-ion rechargeable battery, providing dendrite-free liquid alkali-metal batteries with a liquid-liquid anode-electrolyte interface at room temperature. The two liquids are each immobilized in a porous matrix. In previous work, the porous matrix used to immobilize the alloy was a carbon paper that is wet by the alloy at 420 °C; the alloy remains in the paper at room temperature. Here we report a room-temperature vacuum infiltration of the alloy into a porous Cu or Al membrane and a reversible stripping/plating of the liquid alloy with the immobilized organic-liquid electrolyte; no self-diacharge is observed since the liquid Na-K does not dissolve into the liquid carbonate electrolytes. The preparation and stripping/plating of the liquid alkali-metal anode can both now be done safely at room temperature.

Garnet-structured Li7La3Zr2O12 is a promising solid Li-ion electrolyte for all-solid-state Li-metal batteries and Li-redox-flow batteries owing to its high Li-ion conductivity at room temperature and good electrochemical stability with Li metal. However, there are still three major challenges unsolved: (1) the controversial electrochemical window of garnet, (2) the impractically large resistance at a garnet/electrode interface and the fast lithium-dendrite growth along the grain boundaries of the garnet pellet, and (3) the fast degradation during storage. We have found that these challenges are closely related to a thick Li2CO3 layer and the Li–Al–O glass phase on the surface of garnet materials. Here we introduce a simple method to remove Li2CO3 and the protons in the garnet framework by reacting garnet with carbon at 700 °C; moreover, the amount of the Li–Al–O glass phase with a low Li-ion conductivity in the grain boundary on the garnet surface was also reduced. The surface of the carbon-treated garnet...

Solid-oxide Li+ electrolytes of a rechargeable cell are generally sensitive to moisture in the air as H+ exchanges for the mobile Li+ of the electrolyte and forms insulating surface phases at the electrolyte interfaces and in the grain boundaries of a polycrystalline membrane. These surface phases dominate the total interfacial resistance of a conventional rechargeable cell with a solid-electrolyte separator. We report a new perovskite Li+ solid electrolyte, Li0.38 Sr0.44 Ta0.7 Hf0.3 O2.95 F0.05 , with a lithium-ion conductivity of σLi =4.8×10-4 S cm-1 at 25 °C that does not react with water having 3≤pH≤14. The solid electrolyte with a thin Li+ -conducting polymer on its surface to prevent reduction of Ta5+ is wet by metallic lithium and provides low-impedance dendrite-free plating/stripping of a lithium anode. It is also stable upon contact with a composite polymer cathode. With this solid electrolyte, we demonstrate excellent cycling performance of an all-solid-state Li/LiFePO4 cell, a Li-S cell with a polymer-gel cathode, and a supercapacitor.

Safety and high energy density are the two focus issues for current lithium ion batteries. For safety, it has been demonstrated that sulfone electrolytes are much less flammable than the prevailing all-carbonate type, and they are also promising for high voltage batteries due to the high oxidization resistance. However, the high melting points and viscosities greatly restricted their application. Based on our previous work on use of fluidity-enhancing cosolvents to make binary sulfone-carbonate electrolytes, we report here a three-component system that is more conductive and should be even less flammable while additionally having better low temperature stability. The conductivity–viscosity relations have been determined for this electrolyte and are comparable to those of the “standard” carbonate electrolyte. The additional component also produces much improved capacity retention for the LiNi0.5Mn1.5O4 cathode. As with carbonate electrolytes, increase of temperature to 55 °C leads to rapid capacity decrease during cycling, but the capacity loss is due to the salt, not the solvent. The high discharge capacity observed at 25 °C when LiBF4 replaces LiPF6, is fully retained at 55 °C.

Lithium-ion battery is currently the dominant energy storage technology for electronic devices and electric vehicles. However, the predictable rising cost of lithium raw materials has attracted increasing interest in less expensive rivals, such as sodium-ion battery. In this work, a tin antimony (SnSb) alloy-filled porous carbon nanofiber composite was prepared as a sodium-ion battery anode material by a simple electrospinning method with subsequent thermal treatment. The spinning solution contained antimony tin oxide nanoparticles as the SnSb alloy precursor, polyacrylonitrile as the carbon precursor, and polymethyl methacrylate (PMMA) as the pore generator. The resultant SnSb@C nanofiber composite formed a continuous conductive network, which was favorable for enhancing its electrochemical performance. The presence of the SnSb alloy significantly increased the energy storage capacity of the composite due to its high theoretical capacity. The porous structure created by the decomposition of the PMMA polymer provided a free space to buffer the volume change of the SnSb alloy during the sodiation–desodiation process. The resultant SnSb@C nanofiber composite exhibited high capacity and a stable rate capability, and it was demonstrated to be a promising anode candidate for sodium-ion batteries.

highlights g rap hical a bstract � 99% coulomb efficiency at LiNi0.5M1.5O4 cathode with sulfone ecarbonate electrolyte. � This electrolyte also yields 97% capacity retention at LiNi0.5M1.5O4 over 100 cycles. � Also reported is ideal capacity retention and efficiency at Li4Ti5O12 anode. � So Li4Ti5O12/(this electrolyte)/ LiNi0.5M1.5O4 full cells offer safe, efficient, long life with reduced fire risk.

Si/C–C core–shell nanofiber structure was designed by dual nozzle coaxial electrospinning and subsequent carbonization. This core–shell nanofiber structure has Si/C composite as the core and carbon as the shell. Used as an anode in lithium-ion batteries, the carbon shell can help buffer the large volume expansion/contraction of the Si/C core during charge/discharge and restrain the capacity fading caused by the mechanical failure of the active material. Results showed that after 50 cycles, the discharge capacity of Si/C–C core–shell composite nanofibers was 63% higher than that of Si/C composite nanofibers and the capacity retention increased from 48.6 to 72.4%. It is, therefore, demonstrated that Si/C–C core–shell composite nanofibers are promising anode material with large reversible capacity and good cycling stability.

For tin-based anode materials that suffer from poor cycling stability due to severe volume changes upon lithiation/delithiation processes, the morphology control method might provide a solution. Today, coaxial core-shell structure has attracted wide attention due to its ability to accommodate the volume changes of tin (core), which is well encapsulated in the carbon matrix (shell). Coaxial electrospinning is a simple and effective method to prepare this kind of material. In this work, tin was dispersed in the carbon core and then coated a carbon shell to form Sn@C/C nanofibers by coaxial electrospinning. Flow ratio and tin content were investigated as two main critical factors for controlling the core/shell structure, so as to improve the cycling preference of tin anodes. When tested as a lithium-ion battery anode, the material not only showed higher reversible specific capacity (626 mAh g −1 ) than pure carbon nanofibers, but also exhibited better cycling performance (50 cycles with 73% capacity retention), indicating that the volume change problem of tin anodes has been well resolved by this morphology control.

Potassium manganese hexacyanoferrate (KMHCF) is a low-cost Prussian blue analogue (PBA) having a rigid and open framework that can accommodate large alkali ions. Herein, the synthesis of KMHCF and its application as a high-performance cathode in sodium-ion batteries (NIBs) is reported. High-quality KMHCF with low amounts of crystal water and defects and with homogeneous microstructure is obtained by controlling the nucleation and grain growth by using a high-concentration citrate solution as a precipitation medium. The obtained KMHCF exhibits superior cycling and rate performance as a NIB cathode, showing 80% capacity retention after 1000 cycles at 1 C and a high capacity of 95 mA h g-1 at 20 C. Unlike conventional single-cation batteries, the hybrid NIB with KMHCF as cathode and Na as anode in Na-ion electrolyte displays three reversible plateaus that involve stepwise insertion/extraction of both K+ and Na+ in the PBA framework. In later cycling, the K+ -Na+ cointercalated phase is partially converted into a cubic sodium manganese hexacyanoferrate (NaMHCF) phase due to the increasing replacement of Na+ for K+ .

Sodium vanadium fluorophosphate (NaVPO4F), a material candidate for sodium-ion battery cathodes, was synthesized via a high-temperature solid-state reaction approach. Different amounts of carbon coating were introduced in NaVPO4F to improve its electrochemical performance. The structure and morphology of the resultant cathode materials were examined by scanning electron microscopy and X-ray diffraction. The effects of carbon coating on the electrochemical performance were evaluated by cyclic voltammetry, charge–discharge curve, cycling performance and electrochemical impedance spectroscopy. The highest capacity achieved for this material was 97.8 mAh g−1 and the best capacity retention was 89% at the 20th cycle. Results demonstrated that appropriate amount of carbon coating could effectively improve the electrochemical performance of NaVPO4F, and carbon-coated NaVPO4F could offer promising future for sodium-ion battery cathode materials.

Si-based anode materials were prepared by electrospinning and carbonization using polyacrylonitrile as the spinning medium and carbon precursor. The effects of atomic layer deposition (ALD) alumina coatings with different thicknesses on the electrochemical performance of Si/C composite nanofiber anodes were investigated. Results show that when the ALD alumina coating cycle number is 28, the capacity retention at 100th cycle increases significantly from 36.1% to 82.3% and the coulombic efficiency increases from 98.4% to 99.9%, compared to those of the uncoated Si/C nanofiber anode. This demonstrates the excellent stability of ALD alumina-coated Si/C composite nanofiber anodes. The enhanced electrochemical performance is mainly due to the protective effect of conformal ALD alumina coating, which could improve the mechanical integrity of the electrode structure and prevent the side reactions between the electrode and the electrolyte.

Alloy anodes (Si, Ge and Sn) electrospun into carbon nanofibers as binder-free electrodes were synthesized and studied for rechargeable lithium-ion batteries. Alloy anode materials suffer from serious volume changes and nanoparticle aggregations during lithium insertion and extraction, resulting in rapid pulverization and capacity loss. Carbon nanofibers could help preserve the alloy anode materials during repeated cycling, and consequently maintain the cycling stability. In this work, it was found that with the increase in the amount of Si, Ge and Sn, the cycling stability was decreased due to the formation of large clusters within the carbon nanofiber matrix. Compared with Si/carbon nanofibers, Ge/carbon and Sn/carbon exhibited better cycling performance due to their improved nanoparticle distribution and smaller volume changes. The failure mechanism of the Si/carbon structure was explained in this article. It is believed that this study on Si/carbon, Ge/carbon and Sn/carbon composite nanofiber electrodes could help in designing alloy-based carbon composites with various structures for advanced lithium-ion batteries.

Various x Li 2 MnO 3 ·(1 − x )LiCo 1/3 Ni 1/3 Mn 1/3 O 2 ( x = 0.1, 0.2, 0.3, 0.4, and 0.5) cathode materials were prepared by the one-step sol–gel route. The structure of x Li 2 MnO 3 ·(1 − x )LiCo 1/3 Ni 1/3 Mn 1/3 O 2 composites was determined by X-ray diffraction analysis. The surface morphology and microstructure of x Li 2 MnO 3 ·(1 − x )LiCo 1/3 Ni 1/3 Mn 1/3 O 2 composites were characterized using scanning electron microscopy and transmission electron microscopy. Electrochemical performance of x Li 2 MnO 3 ·(1 − x )LiCo 1/3 Ni 1/3 Mn 1/3 O 2 composites was evaluated in terms of capacity, cycling performance and rate capability. Although the morphology and structure were found to be affected by the Li 2 MnO 3 content, all composites showed an α-NaFeO 2 structure with R3m space group. Electrochemical results showed that cells using 0.3Li 2 MnO 3 ·0.7LiCo 1/3 Ni 1/3 Mn 1/3 O 2 composites had good performance, in terms of large reversible capacity, prolonged cycling stability, and excellent rate capability.

Lithium-ion batteries have been wildly used in various portable electronic devices and the application targets are currently moving from small-sized mobile devices to large-scale electric vehicles and grid energy storage. Therefore, lithium-ion batteries with higher energy densities are in urgent need. For high-energy cathodes, Li2MnO3–LiMO2 layered–layered (M = Mn, Co, Ni) materials are of significant interest due to their high specific capacities over wide operating potential windows. Here, three Li2MnO3-based cathode materials with α-NaFeO2 structure were prepared by a facile co-precipitation method and subsequent heat treatment. Among these three materials, 0.3Li2MnO3·0.5LiMn0.5Ni0.5O2·0.2LiCoO2 shows the best lithium storage capability. This cathode material is composed of uniform nanosized particles with diameters ranging from 100 to 200 nm, and it could be charged to a high cutoff potential to extract more lithium, resulting in a high capacity of 178 mAh g−1 between 2.0 and 4.6 V with almost no capacity loss over 100 cycles.

Lithium-ion battery (LIB) anodes with high capacity and binder free structure were synthesized from carbon nanofibers that contained silicon nanoparticles (Si@CNF). The particle filled nonwoven structures were produced by an electrospinning and subsequent carbonization process. Pristine Si@CNF composites had Si nanoparticles exposed on the fiber surface. As produced, the Si nanoparticles could become detached from the nanofiber surface during cycling, causing severe structural damage and capacity loss. In order to prevent Si from detaching from the nanofiber surface, the Si@CNF composite was then treated with a thermal chemical vapor deposition (CVD) technique to make Si completely coated with a carbon matrix. The carbon coated Si@CNF (Si@CNF-C) composites were synthesized with different Si contents (10, 30, and 50 wt%) for different CVD treatment times (30, 60, and 90 min). It was found that the initial coulombic efficiency of Si@CNF-C could be increased via the amorphous carbon by stabilizing solid-electrolyte-interface (SEI) formation on surface. The capacity and cyclic stability were improved by the CVD carbon coating, especially for the 30 wt% Si@CNF-C composite with 90 min CVD coating, a CVD amorphous carbon coating of less than 1% by weight on Si@CNF composites contributed to more than 200% improvement in cycling performance. Results indicate that the CVD carbon coating is an effective approach to improve the electrochemical properties of Si@CNF composites making this a potential route to obtain high-energy density anode materials for LIBs.

Aligned carbon nanotube sheets provide an engineered scaffold for the deposition of a silicon active material for lithium ion battery anodes. The sheets are low-density, allowing uniform deposition of silicon thin films while the alignment allows unconstrained volumetric expansion of the silicon, facilitating stable cycling performance. The flat sheet morphology is desirable for battery construction.

Sn/carbon composite nanofibers with various compositions were prepared from Sn(II) acetate/polyacrylonitrile (PAN) precursors by a combination of electrospinning and carbonization methods, and their potential use as anode materials for rechargeable lithiumion batteries was investigated. The composite electrode derived from 20 wt% Sn(II) acetate/PAN precursor showed excellent electrochemical properties, including a large reversible capacity of 699 mAh g-1 and a high capacity retention of 83% in 50 cycles. Sn/carbon composite nanofibers exhibited enhanced electrochemical performance ascribing to the combination of the properties of both Sn nanoparticles (large Li storage capability) and carbon matrices (long cycle life), and therefore could be potentially used in high-energy rechargeable lithium-ion batteries.

Si/C composite nanofibers were prepared by electrospinning and carbonization using polyacrylonitrile as the spinning medium and carbon precursor. The effect of electrolyte additive succinic anhydride (SA) on the electrochemical performance of Si/C composite nanofiber anodes was investigated. Results show that after 50 cycles, the discharge capacity of Si/C composite nanofiber anode with the SA-added electrolyte is 34 % higher than that with additive-free electrolyte. At 150th cycle, the capacity retention of Si/C composite nanofiber anode with SA-added electrolyte is 82 % under 70 % state-of-charge. It is demonstrated that adding additive SA in the electrolyte is an effective and economic way to improve the cyclability of high-capacity Si/C composite nanofibers for next-generation high-energy lithium-ion batteries.

NASICON (Na

A solid electrolyte with a high Li-ion conductivity and a small interfacial resistance against a Li metal anode is a key component in all-solid-state Li metal batteries, but there is no ceramic oxide electrolyte available for this application except the thin-film Li-P oxynitride electrolyte; ceramic electrolytes are either easily reduced by Li metal or penetrated by Li dendrites in a short time. Here, we introduce a solid electrolyte LiZr 2 (PO4) 3 with rhombohedral structure at room temperature that has a bulk Li-ion conductivity σ Li = 2 × 10 −4 S⋅cm −1 at 25 °C, a high electrochemical stability up to 5.5 V versus Li + /Li, and a small interfacial resistance for Li + transfer. It reacts with a metallic lithium anode to form a Li + -conducting passivation layer (solid-electrolyte interphase) containing Li 3 P and Li 8 ZrO 6 that is wet by the lithium anode and also wets the LiZr 2 (PO 4 ) 3 electrolyte. An all-solid-state Li/LiFePO 4 cell with a polymer catholyte shows good cyclability and a long cycle life.

Li7La3Zr2O12-based Li-rich garnets react with water and carbon dioxide in air to form a Li-ion insulating Li2CO3 layer on the surface of the garnet particles, which results in a large interfacial resistance for Li-ion transfer. Here, we introduce LiF to garnet Li6.5La3Zr1.5Ta0.5O12 (LLZT) to increase the stability of the garnet electrolyte against moist air; the garnet LLZT-2 wt % LiF (LLZT-2LiF) has less Li2CO3 on the surface and shows a small interfacial resistance with Li metal, a solid polymer electrolyte, and organic-liquid electrolytes. An all-solid-state Li/polymer/LLZT-2LiF/LiFePO4 battery has a high Coulombic efficiency and long cycle life; a Li-S cell with the LLZT-2LiF electrolyte as a separator, which blocks the polysulfide transport towards the Li-metal, also has high Coulombic efficiency and kept 93 % of its capacity after 100 cycles.

A K-Na liquid alloy allows a dendrite-free high-capacity anode; its immiscibility with an organic liquid electrolyte offers a liquid-liquid anode-electrolyte interface. Working with a sodiated Na2 MnFe(CN)6 cathode, the working cation becomes K+ to give a potassium battery of long cycle life with an acceptable capacity at high charge/discharge rates.

Si has the highest theoretical capacity among all known anode materials, but it suffers from the dramatic volume change upon repeated lithiation and delithiation processes. To overcome the severe volume changes, Si nanoparticles were first coated with a polymer-driven carbon layer, and then dispersed in a CNT network. In this unique structure, the carbon layer can improve electric conductivity and buffer the severe volume change, whereas the tangled CNT network is expected to provide additional mechanical strength to maintain the integrity of electrodes, stabilize the electric conductive network for active Si, and eventually lead to better cycling performance. Electrochemical test result indicates the carbon-coated Si nanoparticles dispersed in CNT networks show capacity retention of 70% after 40 cycles, which is much better than the carbon-coated Si nanoparticles without CNTs.

A simple approach is proposed to prepare C-SiO2 composites as anode materials for lithium ion batteries. In this novel approach, nano-sized silica is soaked in sucrose solution and then heat treated at 900 °C under nitrogen atmosphere. Transmission electron microscopy (TEM) and X-ray diffraction (XRD) analysis shows that SiO2 is embedded in amorphous carbon matrix. The electrochemical test results indicate that the electrochemical performance of the C-SiO2 composites relates to the SiO2 content of the composite. The C-SiO2 composite with 50.1% SiO2 shows the best reversible lithium storage performance. It delivers an initial discharge capacity of 536 mAh g−1 and good cyclability with the capacity of above 500 mAh g−1 at 50th cycle. Electrochemical impedance spectra (EIS) indicates that the carbon layer coated on SiO2 particles can diminish interfacial impedance, which leads to its good electrochemical performance.

Despite the high specific capacity and low redox potential of alkali metals, their practical application as anodes is still limited by the inherent dendrite-growth problem. The fusible sodium-potassium (Na-K) liquid metal alloy is an alternative that detours this drawback, but the fundamental understanding of charge transport in this binary electroactive alloy anode remains elusive. Here, comprehensive characterization, accompanied with density function theory (DFT) calculations, jointly expound the Na-K anode-based battery working mechanism. With the organic cathode sodium rhodizonate dibasic (SR) that has negligible selectivity toward cations, the charge carrier is screened by electrolytes due to the selective ionic pathways in the solid electrolyte interphase (SEI). Stable cycling for this Na-K/SR battery is achieved with capacity retention per cycle to be 99.88% as a sodium-ion battery (SIB) and 99.70% as a potassium-ion battery (PIB) for over 100 cycles. Benefitting from the flexibility of the liquid metal and the specially designed carbon nanofiber (CNF)/SR layer-by-layer cathode, a flexible dendrite-free alkali-ion battery is achieved with an ultrahigh areal capacity of 2.1 mAh cm-2 . Computation-guided materials selection, characterization-supported mechanistic understanding, and self-validating battery performance collectively promise the prospect of a high-performance, dendrite-free, and versatile organic-based liquid metal battery.

A binder-free three-dimensional (3D) porous Cu6Sn5 anode was prepared for lithium-ion batteries. In this novel approach, tin was deposited by electroless-plating on copper foam which was served as anode current collector as well as the source of copper for Cu6Sn5 alloy formation. With optimized post-treatment condition, Cu6Sn5 alloy with thickness of 1.2 μm was formed on the surface of copper foam network. 3D porous Sn–Cu6Sn5 and Cu3Sn–Cu10Sn3–Cu6Sn5 composite anodes were also prepared for comparison. Electrochemical tests showed that 3D porous Cu6Sn5 anode exhibits the best electrochemical performance in terms of specific capacitance and cycleability, which delivers a rechargeable capacity of 404 mAh g−1 over 100 cycles.

A hierarchical porous MnO2-based electrode was prepared and its electrochemical performance for electrochemical capacitors was investigated. In this work, porous MnO2 film with pore size of 2–3 nm in diameter was deposited on a three-dimensional porous current collector by cathodic electrodeposition associated with subsequent controlled heat treatment at 200°C for 2 h. Transmission electron microscopy and X-ray photoelectron spectroscopy showed that the heat treatment has a great effect on the formation of the porous structure of MnO2 layer, and the disordered porous structure was caused by dehydration during the heat treatment. Cyclic voltammetry and galvanostatic charge–discharge tests showed that both energy and power densities are enhanced due to the unique hierarchical porous structure. The electrode delivers a high specific capacitance of 385 F g−1 at a high current density of 5 A g−1 within a potential window of −0.05 ∼ 0.85 V, and also exhibits excellent rate capability and electrochemical stability.

Poor crystallined α-MnO2 grown on multi-walled carbon nanotubes (MWCNTs) by reducing KMnO4 in ethanol are characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) and Brunauer–Emmett–Telle (BET) surface area measurement, which indicate that MWCNTs are wrapped up by poor crystalline MnO2 and BET areas of the composites maintain the same level of 200 m2 g−1 as the content of MWCNTs in the range of 0–30%. The electrochemical performances of the MnO2/MWCNTs composites as electrode materials for supercapacitor are evaluated by cyclic voltammetry (CV) and galvanostatic charge–discharge measurement in 1 M Na2SO4 solution. At a scan rate of 5 mV s−1, rectangular shapes could only be observed for the composites with higher MWCNTs contents. The effect of additional conductive agent KS6 on the electrochemical behavior of the composites is also studied. With a fixed carbon content of 25% (MWCNTs included), MnO2 with 20% MWCNTs and 5% KS6 has the highest specific capacitance, excellent cyclability and best rate capability, which gives the specific capacitance of 179 F g−1 at a scan rate of 5 mV s−1, and remains 114.6 F g−1 at 100 mV s−1.

PtRuMoOx and PtRuWOx catalysts supported on multi-wall carbon nanotubes (MWCNTs) are prepared by ultrasonic-assisted chemical reduction method. XRD measurements indicate that Pt exists as face-centered cubic structure, Ru is alloyed with platinum, and the metal oxides exist as an amorphous structure. TEM pictures show that PtRuMoOx and PtRuWOx catalysts are well dispersed on the surface of MWCNTs with the particle size of about 3 nm and a narrow particle size distribution. The electrochemical properties of the catalysts for methanol electrooxidation are studied by cyclic voltammetry (CV), chronoamperometry (CA) and chronopotentiometry (CP). The onset potentials for methanol oxidation on PtRuMoOx and PtRuWOx are more negative than that of pure Pt catalyst, shifting negatively by about 0.20 V and have better electrocatalytic activities than PtRu/MWCNTs.