Sandwiched ReS2 nanocables with dual carbon coating for efficient K+/Na+ storage performance.

In this work, the nanocables of few-layered ReS2 nanosheets sandwiched between carbon nanotubes (CNTs) and nitrogen-doped amorphous carbon (NC) coating (i.e., CNT@ReS2@NC) are synthesized as high-performance anodes of both potassium-ion batteries (PIBs) and sodium-ion batteries (SIBs). The CNT@ReS2@NC nanocables with dual carbon modifications have the several advantages for efficient K+/Na+ storage. The few-layered ReS2 nanosheets with a wide interlayer spacing of 0.64 nm contribute to accelerated reaction kinetics for fast K+/Na+ intercalation/extraction. The carbon nanotube skeleton with a hollow interior can effectively relieve the volume change and serve as a robust conductive network to boost structural stability. The NC layer provides rich defects as active sites and suppresses the shuttle effect of polysulfides produced in discharge/charge processes. Consequently, the CNT@ReS2@NC nanocables possess outstanding electrochemical performance in both PIBs and SIBs owing to the synergistic effect from the different components. A long cycling lifespan of 3500 cycles with a maintained discharge capacity of 125 mAh/g is achieved for CNT@ReS2@NC at 1 A/g in PIBs. In SIBs, it can keep a high capacity of 202 mAh/g over 3000 cycles at 5 A/g. Moreover, the CNT@ReS2@NC||Na3V2(PO4)3 full cell can exhibit remarkable cycling performance, yielding a low capacity decay rate of 0.019 % per cycle over 1000 cycles at 2C.

Dual engineering of hetero-interfaces and architecture in MoSe2/VSe1.6@NC nanoflower for fast and stable sodium/potassium storage.

Rational structure design is significant for the selenide anodes in the sodium/potassium ion batteries (SIBs/PIBs). Herein, dual engineering of hetero-interfaces and architecture is proposed to design SIB/PIB anodes. Attributed to the coordination binding with Mo7O246- and VO3-, the polydopamine assembly is demonstrated as an ideal template to produce bimetallic selenide of MoSe2/VSe1.6 anchoring on the in-situ N-doped carbon matrix (MoSe2/VSe1.6@NC). This ingenious hierarchical nanoflower structure can shorten the Na+/K+ diffusion length, increase the electron conductivity and buffer the volume changes, which can promote Na+/K+ reaction kinetics and stabilize the cycling performance. Consequently, the sodium/ potassium storage performance of MoSe2/VSe1.6@NC can be boosted. In SIBs, it achieves a capacity of 202 mAh/g at 10.0 A/g for 5000 cycles. Meanwhile, stable capacities of 207.1 mAh/g can be reached at 1.0 A/g over 1000 cycles in the PIBs. Furthermore, impressive capacities of 222.1 mAh/g and 100.4 mAh/g are delivered in the full cells of MoSe2/VSe1.6@NC//Na3V2(PO4)3@C and MoSe2/VSe1.6@NC//FePBA, respectively. This proves the potential practical application for the MoSe2/VSe1.6@NC anode in SIBs/PIBs.

Confined Assembly of Hydrated Vanadium Oxide into Hollow Mesoporous Carbon Nanospheres for Fast and Stable K+ Storage Capability.

The rational structural design of the electrode materials is significant to enhance the electrochemical performance for potassium ion storage, benefiting from the shortened ion diffusion distance, increased conductivity, and pseudo-capacitance promotion. Herein, hydrated vanadium oxide (HVO) nanosheets with enriched oxygen defects are well confined into hollow mesoporous carbon spheres (HMCS), producing Od -VOH@C nanospheres through one-step hydrothermal reaction. Attributed to the restricted growth in the HMCS, the HVO nanosheets are loosely packed, generating abundant interfacial boundaries and large specific areas. As a result, Od -VOH@C nanospheres show increased reaction kinetics and well buffer the volume effects for the K+ storage. Od -VOH@C delivers stable capacities of 138 mAh g-1 at 2.0 A g-1 over 10 000 cycles in half-cells attributed to the high pseudo-capacitance contribution. The K+ storage mechanism of insertion and conversion reaction is confirmed by ex situ X-ray diffraction, Raman, and X-ray photoelectron spectroscopy analyses. Moreover, the symmetric potassium-ion capacitors of Od -VOH@C//Od -VOH@C deliver a high energy density of 139.6 Wh kg-1 at the power density of 948.3 W kg-1 .

Metal-Organic Assembly Strategy for the Synthesis of Layered Metal Chalcogenide Anodes for Na+ /K+ -Ion Batteries.

Layered transition metal chalcogenides (MX, M=Mo, W, Sn, V; X=S, Se, Te) have large ion transport channels and high specific capacity, making them promising for large-sized Na+ /K+ energy-storage technologies. Nevertheless, slow reaction kinetics and huge volume expansion will induce an undesirable electrochemical performance. Numerous efforts have been devoted to designing MX anodes and enhancing their electrochemical performance. Based on the metal-organic assembly strategy, nanostructural engineering, combination with carbon materials, and component regulation can be easily realized, which effectively boost the performance of MX anodes. In this Review, we present a comprehensive overview on the synthesis of MX nanostructure using the metal-organic assembly strategy, which can realize the design of MX nanostructures, based on self-sacrificial templates, host@guest tailored templates, post-modified layer and derivative templates. The preparation routes and structure evolution are mainly discussed. Then, Mo-, W-, Sn-, V-based chalcogenides used for Na+ /K+ energy storage are reviewed, and the relationship between the structure and the electrochemical performance, as well as the energy storage mechanism are emphasized. In addition, existing challenges and future perspectives are also presented.

Tunable Electrochemical Activity of P2-Na0.6Mn0.7Ni0.3O2-xFx Microspheres as High-Rate Cathodes for High-Performance Sodium Ion Batteries.

As an important cathode candidate for the high-performance sodium ion batteries (SIBs), P2-type oxides with layered structures are needed to balance the specific capacities and cycling stability. As a result, a cation and anion codoped strategy has been adopted to tune the electrochemical activity of the redox centers and modulate the structure properties. Herein, a series of P2-Na0.6Mn0.7Ni0.3O2-xFx (x = 0, 0.03, 0.05, and 0.07) cathodes with microsphere structures are synthesized, using a solid-state reaction in the presence of MnO2 microsphere self-templates. Compared with the cation-doped Na0.6Mn0.7Ni0.3O2, additional F-doping can affect the lattice parameters and redox centers of Na0.6Mn0.7Ni0.3O2-xFx. Comprehensively considering the specific capacities, cycling stability, and rate capability, the optimized x value in Na0.6Mn0.7Ni0.3O2-xFx is determined to be 0.05. In the half cells, Na0.6Mn0.7Ni0.3O1.95F0.05 (F-0.05) maintains a capacity of 90.5 mA h g-1 in the first cycle at 1.0 A g-1, giving a capacity retention of 78% within 900 cycles. The superior rate capability of F-0.05 is guaranteed by the larger diffusion coefficient of Na+ (DNa) combined with higher charge transfer speed. In addition, when coupled with MoSe2/PC anodes, the full cells also exhibit impressive electrochemical performance.

Cation-exchange construction of ZnSe/Sb2Se3 hollow microspheres coated by nitrogen-doped carbon with enhanced sodium ion storage capability.

Recently, anode materials with synergistic sodium storage mechanisms of conversion combined with alloying reactions for sodium ion batteries (SIBs) have received widespread attention due to their high theoretical capacities. In this work, through reacting with an appropriate concentration of Sb3+ ions and a simple carbonization process, hollow ZnSe/Sb2Se3 microspheres encapsulated in nitrogen-doped carbon (ZnSe/Sb2Se3@NC) are progressively synthesized based on a cation-exchange reaction, using polydopamine-coated ZnSe (ZnSe@PDA) microspheres as the precursor. Benefiting from the synergistic effects between the unique structure and composition characteristics, when serving as an anode material for SIBs, they result in higher sodium diffusion coefficients (8.7 × 10-13-3.98 × 10-9 cm2 s-1) and ultrafast pseudocapacitive sodium storage capability. Compared with ZnSe@NC and Sb2Se3@NCs exhibit, ZnSe/Sb2Se3@NC exhibits more stable capacity (438 mA h g-1 at a current of 0.5 A g-1 after 120 cycles) and superior rate performance (316 mA h g-1 at 10.0 A g-1). Our work provides a convenient method to construct high performance anodes with tunable composition and structure for energy storage.

Okra-Like Fe7 S8 /C@ZnS/N-C@C with Core-Double-Shelled Structures as Robust and High-Rate Sodium Anode.

Core-multishelled structures with controlled chemical composition have attracted great interest due to their fascinating electrochemical performance. Herein, a metal-organic framework (MOF)-on-MOF self-templated strategy is used to fabricate okra-like bimetal sulfide (Fe7 S8 /C@ZnS/N-C@C) with core-double-shelled structure, in which Fe7 S8 /C is distributed in the cores, and ZnS is embedded in one of the layers. The MOF-on-MOF precursor with an MIL-53 core, a ZIF-8 shell, and a resorcinol-formaldehyde (RF) layer (MIL-53@ZIF-8@RF) is prepared through a layer-by-layer assembly method. After calcination with sulfur powder, the resultant structure has a hierarchical carbon matrix, abundant internal interface, and tiered active material distribution. It provides fast sodium-ion reaction kinetics, a superior pseudocapacitance contribution, good resistance of volume changes, and stepwise sodiation/desodiation reaction mechanism. As an anode material for sodium-ion batteries, the electrochemical performance of Fe7 S8 /C@ZnS/N-C@C is superior to that of Fe7 S8 /C@ZnS/N-C, Fe7 S8 /C, or ZnS/N-C. It delivers a high and stable capacity of 364.7 mAh g-1 at current density of 5.0 A g-1 with 10 000 cycles, and registers only 0.00135% capacity decay per cycle. This MOF-on-MOF self-templated strategy may provide a method to construct core-multishelled structures with controlled component distributions for the energy conversion and storage.

NiSe2/Ni(OH)2 Heterojunction Composite through Epitaxial-like Strategy as High-Rate Battery-Type Electrode Material.

Constructing heterojunction is a promising way to improve the charge transfer efficiency and can thus promote the electrochemical properties. Herein, a facile and effective epitaxial-like growth strategy is applied to NiSe2 nano-octahedra to fabricate the NiSe2-(100)/Ni(OH)2-(110) heterojunction. The heterojunction composite and Ni(OH)2 (performing high electrochemical activity) is ideal high-rate battery-type supercapacitor electrode. The NiSe2/Ni(OH)2 electrode exhibits a high specific capacity of 909 C g-1 at 1 A g-1 and 597 C g-1 at 20 A g-1. The assembled asymmetric supercapacitor composed of the NiSe2/Ni(OH)2 cathode and p-phenylenediamine-functional reduced graphene oxide anode achieves an ultrahigh specific capacity of 303 C g-1 at 1 A g-1 and a superior energy density of 76.1 Wh kg-1 at 906 W kg-1, as well as an outstanding cycling stability of 82% retention for 8000 cycles at 10 A g-1. To the best of our knowledge, this is the first example of NiSe2/Ni(OH)2 heterojunction exhibiting such remarkable supercapacitor performance. This work not only provides a promising candidate for next-generation energy storage device but also offers a possible universal strategy to fabricate metal selenides/metal hydroxides heterojunctions.

"HOT" Alkaline Hydrolysis of Amorphous MOF Microspheres to Produce Ultrastable Bimetal Hydroxide Electrode with Boosted Cycling Stability.

Nickel/cobalt hydroxide is a promising battery-type electrode material for supercapacitors. However, its low cycle stability hinders further applications. Herein, Ni0.7 Co0.3 (OH)2 core-shell microspheres exhibiting extreme-prolonged cycling life are successfully synthesized, employing Ni-Co-metal-organic framework (MOF) as the precursor/template and a specific hydrolysis strategy. The Ni-Co-MOF and KOH aqueous solution are separated and heated to 120 °C before mixing, rather than mixing before heating. Through this hydrolysis strategy, no MOF residual exists in the product, contributing to close stacking of the hydroxide nanoflakes to generate Ni0.7 Co0.3 (OH)2 microspheres with a robust core-shell structure. The electrode material exhibits high specific capacity (945 C g-1 at 0.5 A g-1 ) and unprecedented cycling performance (100% after 10 000 cycles). The fabricated asymmetric supercapacitor delivers an energy density of 40.14 Wh kg-1 at a power density of 400.56 W kg-1 and excellent cycling stability (100% after 20 000 cycles). As far as is known, it is the best cycling performance for pure Ni/Co(OH)2 .

Controlled Hydrolysis of Metal-Organic Frameworks: Hierarchical Ni/Co-Layered Double Hydroxide Microspheres for High-Performance Supercapacitors.

Pseudomorphic conversion of metal-organic frameworks (MOFs) enables the fabrication of nanomaterials with well-defined porosities and morphologies for enhanced performances. However, the commonly reported calcination strategy usually requires high temperature to pyrolyze MOF particles and often results in uncontrolled growth of nanomaterials. Herein, we report the controlled alkaline hydrolysis of MOFs to produce layered double hydroxide (LDH) while maintaining the porosity and morphology of MOF particles. The preformed trinuclear M3(µ3-OH) (M = Ni2+ and Co2+) clusters in MOFs were demonstrated to be critical for the pseudomorphic transformation process. An isotopic tracing experiment revealed that the 18O-labeled M3(µ3-18OH) participated in the structural assembly of LDH, which avoided the leaching of metal cations and the subsequent uncontrolled growth of hydroxides. The resulting LDHs maintain the spherical morphology of MOF templates and possess a hierarchical porous structure with high surface area (BET surface area up to 201 m2·g-1), which is suitable for supercapacitor applications. As supercapacitor electrodes, the optimized LDH with the Ni:Co molar ratio of 7:3 shows a high specific capacitance (1652 F·g-1 at 1 A·g-1) and decent cycling performance, retaining almost 100% after 2000 cycles. Furthermore, the hydrolysis method allows the recycling of organic ligands and large-scale synthesis of LDH materials.

TiO2-Coated Interlayer-Expanded MoSe2/Phosphorus-Doped Carbon Nanospheres for Ultrafast and Ultralong Cycling Sodium Storage.

Based on multielectron conversion reactions, layered transition metal dichalcogenides are considered promising electrode materials for sodium-ion batteries, but suffer from poor cycling performance and rate capability due to their low intrinsic conductivity and severe volume variations. Here, interlayer-expanded MoSe2/phosphorus-doped carbon hybrid nanospheres coated by anatase TiO2 (denoted as MoSe2/P-C@TiO2) are prepared by a facile hydrolysis reaction, in which TiO2 coating polypyrrole-phosphomolybdic acid is utilized as a novel precursor followed by a selenization process. Benefiting from synergistic effects of MoSe2, phosphorus-doped carbon, and TiO2, the hybrid nanospheres manifest unprecedented cycling stability and ultrafast pseudocapacitive sodium storage capability. The MoSe2/P-C@TiO2 delivers decent reversible capacities of 214 mAh g-1 at 5.0 A g-1 for 8000 cycles, 154 mAh g-1 at 10.0 A g-1 for 10000 cycles, and an exceptional rate capability up to 20.0 A g-1 with a capacity of ≈175 mAh g-1 in a voltage range of 0.5-3.0 V. Coupled with a Na3V2(PO4)3@C cathode, a full cell successfully confirms a reversible capacity of 242.2 mAh g-1 at 0.5 A g-1 for 100 cycles with a coulombic efficiency over 99%.

Robust Micron-Sized Silicon Secondary Particles Anchored by Polyimide as High-Capacity, High-Stability Li-Ion Battery Anode.

Silicon is an attractive high-capacity anode material for lithium-ion battery. With the help of nanostructures, cycling performance of silicon anode has improved significantly in the past couple of years. However, three major shortcomings associated with nanostructures still need to be addressed, namely, their high surface area, low tap density, and poor scalability. Herein, we present a facile and practical method to produce micron-sized Si secondary particle cluster (SiSPC) with a high tap density and a low surface area from bulk Si by high-energy ball-milling. By coupling SiSPC with a mechanically robust polyimide binder, more than 95% of the initial capacity is retained after 500 cycles at 3500 mA g-1 (1C rate). Reversibility of electrode thickness change is confirmed by in situ dilatometry. In addition, the polyimide binder suppresses the surface reaction of the particles with electrolyte, resulting in a high Coulombic efficiency of 99.7%. Excellent cycling performance is obtained even for thick electrodes with an areal capacity of 3.57 mAh cm-2, similar to those in commercial lithium-ion batteries. The presented Si electrode system has a high volumetric capacity of 598 mAh cm-3, which is higher than that of the commercial graphite anode materials.

Bimetallic-MOF Derived Accordion-like Ternary Composite for High-Performance Supercapacitors.

Supercapacitors are regarded to be highly probable candidates for next-generation energy storage devices. Herein, a bimetallic Co/Ni MOF is used as a sacrificial template through an alkaline hydrolysis and selective oxidation process to prepare an accordion-like ternary NiCo2O4/ß-Ni xCo1- x(OH)2/α-Ni xCo1- x(OH)2 composite, which is composed of Co/Ni(OH)2 nanosheets with large specific surface as the frame and NiCo2O4 nanoparticles with high conductivity as the insertion, for supercapacitor application. This material exhibits both high specific capacitance (1315 F·g-1 at 5 A·g-1) and excellent cycle performance (retained 90.7% after 10 000 cycles). This hydrolysis-oxidation process, alkali hydrolysis followed by oxidation with H2O2, offers a novel approach to fabricate the Ni/Co-based electrode materials with enhanced supercapacitor performance.

Green Fabrication of Ultrathin Co3O4 Nanosheets from Metal-Organic Framework for Robust High-Rate Supercapacitors.

Two-dimensional cobalt oxide (Co3O4) is a promising candidate for robust electrochemical capacitors with high performance. Herein, we use 2,3,5,6-tetramethyl-1,4-diisophthalate as a recyclable ligand to construct a Co-based metal-organic framework of UPC-9, and subsequently, we obtain ultrathin hierarchical Co3O4 hexagonal nanosheets with a thickness of 3.5 nm through a hydrolysis and calcination process. A remarkable and excellent specific capacitance of 1121 F·g-1 at a current density of 1 A·g-1 and 873 F·g-1 at a current density of 25 A·g-1 were achieved for the as-prepared asymmetric supercapacitor, which can be attributed to the ultrathin 2D morphology and the rich macroporous and mesoporous structures of the ultrathin Co3O4 nanosheets. This synthesis strategy is environmentally benign and economically viable due to the fact that the costly organic ligand molecules are recycled, reducing the materials cost as well as the environmental cost for the synthesis process.

Metal-Organic Framework Derived Porous Hollow Co3O4/N-C Polyhedron Composite with Excellent Energy Storage Capability.

Metal-organic frameworks (MOFs) derived transition metal oxides exhibit enhanced performance in energy conversion and storage. In this work, porous hollow Co3O4 with N-doped carbon coating (Co3O4/N-C) polyhedrons have been prepared using cobalt-based MOFs as a sacrificial template. Assembled from tiny nanoparticles and N-doped carbon coating, Co3O4/N-C composite shortens the diffusion length of Li+/Na+ ions and possesses an enhanced conductivity. And the porous and hollow structure is also beneficial for tolerating volume changes in the galvanostatic discharge/charge cycles as lithium/sodium battery anode materials. As a result, it can exhibit impressive cycling and rating performance. At 1000 mA g-1, the specific capacities maintaine stable values of ∼620 mAh g-1 within 2000 cycles as anodes in lithium ion battery, while the specific capacity keeps at 229 mAh g-1 within 150 cycles as sodium ion battery anode. Our work shows comparable cycling performance in lithium ion battery but even better high-rate cycling stability as sodium ion battery anode. Herein, we provide a facile method to construct high electrochemical performance oxide/N-C composite electrode using new MOFs as sacrificial template.

Conversion of 1T-MoSe2 to 2H-MoS2xSe2-2x mesoporous nanospheres for superior sodium storage performance.

S-Doped 2H-MoSe2 (i.e., 2H-MoS2xSe2-2x) mesoporous nanospheres assembled from several-layered nanosheets are synthesized by sulfurizing freshly-prepared 1T-MoSe2 nanospheres, and they serve as a robust host material for sodium storage. The sulfuration treatment is found to be beneficial for removing surface/interface insulating organic contaminants and converting the 1T phase to the 2H phase with improved crystallinity and electrical conductivity. These result in significantly enhanced sodium storage performance, including charge/discharge capacity, first Coulombic efficiency, cycling stability, and rate capability. Coupled with benefits from in situ carbon modification and its mesoporous morphology, the 2H-MoS2xSe2-2x (x = 0.22) nanosphere anode can maintain a reversible capacity of 407 mA h g-1 after 100 cycles with no observable capacity fading at a high current density of 2.0 A g-1. This value is much higher than those of the anode fabricated with the freshly-prepared 1T-MoSe2 (95 mA h g-1) and the annealed 2H-MoSe2 (144 mA h g-1) samples. As the current density rises from 0.05 to 5.0 A g-1 (100-fold increase), the discharge capacity retention is significantly increased from 39% before sulfuration to 65% after sulfuration. This superior electrochemical performance of the 2H-MoS2xSe2-2x electrode suggests a promising way to design advanced sodium host materials by surface/interface engineering.

P2-Type NaxCu0.15Ni0.20Mn0.65O2 Cathodes with High Voltage for High-Power and Long-Life Sodium-Ion Batteries.

Cu-Ni-Mn-based ternary P2-type NaxCu0.15Ni0.20Mn0.65O2 (x = 0.50, 0.67, and 0.75) cathodes for sodium-ion batteries (SIBs) are synthesized by a co-precipitation method. We find that Na content plays a key role on the structure, morphology, and the charge-discharge performances of these materials. For x = 0.67 and 0.75, superstructure from Na+-vacancy ordering is observed, while it is absent in the x = 0.50 sample. Despite the same synthesis conditions, materials with x = 0.67 and 0.75 show smaller particle sizes compared to that of the x = 0.50 sample. In addition, redox potentials of the materials differ significantly even though they have the same transition metal ratios. These differences are attributed to the changes in local structures of the as-prepared materials arising from the different amount of Na and possibly oxygen in the lattice. Materials with x = 0.67 and 0.75 show excellent rate performance and cycle stability when tested as cathode material of SIBs. Average discharge potential is as high as 3.41 V versus Na-Na+ with capacity of 87 mAh g-1 at 20 mA g-1. Excellent capacity and cycle stability are maintained even when they are tested with higher current rates. For instance, a capacity of 62.3 mAh g-1 is obtained from the x = 0.67 sample at 1000 mA g-1 after 1000 cycles between 3.0 and 4.2 V without any decrease in capacity.

In Situ Carbon-Doped Mo(Se0.85 S0.15 )2 Hierarchical Nanotubes as Stable Anodes for High-Performance Sodium-Ion Batteries.

Sodium-ion batteries (SIBs) are promising energy storage devices, but suffer from poor cycling stability and low rate capability. In this work, carbon doped Mo(Se0.85 S0.15 )2 (i.e., Mo(Se0.85 S0.15 )2 :C) hierarchical nanotubes have been synthesized for the first time and serve as a robust and high-performance anode material. The hierarchical nanotubes with diameters of 300 nm and wall thicknesses of 50 nm consist of numerous 2D layered nanosheets, and can act as a robust host for sodiation/desodiation cycling. The Mo(Se0.85 S0.15 )2 :C hierarchical nanotubes deliver a discharge capacity of 360 mAh g(-1) at a high current density of 2000 mA g(-1) and keep a 81.8% capacity retention compared to that at a current density of 50 mA g(-1) , showing superior rate capability. Comparing with the second cycle discharge capacities, the nanotube anode can maintain capacities of 102.2%, 101.9%, and 97.8% after 100 cycles at current densities of 200, 500, and 1000 mA g(-1) , respectively. This work demonstrates the best cycling performance and high-rate sodium storage capabilities of MoSe2 for SIBs to date. The hollow interior, hierarchical organization, layered structure, and carbon doping are beneficial for fast Na(+) -ion and electron kinetics and are responsible for the stable cycling performance and high rate capabilities.

Nanostructured porous manganese carbonate spheres with capacitive effects on the high lithium storage capability.

In this paper, nanostructured porous MnCO3 spheres are facilely synthesized, which can simultaneously provide an increased surface for conversion reaction and capacitive storage as the anode material for lithium ion batteries. This material gives a superior specific capacity and excellent long-term cycling performance even at a high current density. It can deliver a stable capacity of 1049 mA h g(-1) after 200 cycles at a current density of 1000 mA g(-1), which is much higher than the theoretical capacity of 466 mA h g(-1). After 2000 cycles at a high current density of 5000 mA g(-1), a capacity of 510 mA h g(-1) can still be maintained. Their high rating performance at 5000 mA g(-1) is among the best-reported performances of anode materials. From the in situ or ex situ SEM observation, the porous MnCO3 nanostructure can provide a stable template for reversible lithium insertion and extraction without significant morphology change and accommodate the volume change during the charge-discharge process. Also this structure increases the capacitive contribution to the total capacity compared with other MnCO3 samples.

High interfacial storage capability of porous NiMn2O4/C hierarchical tremella-like nanostructures as the lithium ion battery anode.

Porous hierarchical NiMn2O4/C tremella-like nanostructures are obtained through a simple solvothermal and calcination method. As the anode of lithium ion batteries (LIBs), porous NiMn2O4/C nanostructures exhibit a superior specific capacity and an excellent long-term cycling performance even at a high current density. The discharge capacity can stabilize at 2130 mA h g(-1) within 350 cycles at a current density of 1000 mA g(-1). After a long-term cycling of 1500 cycles, the capacity is still as high as 1773 mA h g(-1) at a high current density of 4000 mA g(-1), which is almost five times higher than the theoretical capacity of graphite. The porous NiMn2O4/C hierarchical nanostructure provides sufficient contact with the electrolyte and fast three-dimensional Li(+) diffusion channels, and dramatically improves the capacity of NiMn2O4/C via interfacial storage.