Facile microemulsion synthesis of mesoporous ZnMn2O4 submicrocubes as high-rate and long-life anodes for lithium ion batteries

In this work, monodispersed mesoporous ZnMn₂O₄ submicrocubes constructed of interconnected nanoparticles have been fabricated by pyrolysis of the Zn_1/3Mn_2/3CO₃ precursor obtained through a precipitation reaction in the water–n-pentanol–CTAB–n-hexane microemulsion. The effects of microemulsion composition on the morphology and size of Zn_1/3Mn_2/3CO₃ are investigated. The uniform ZnMn₂O₄ cubes obtained in the optimized microemulsion system have an average edge length of ca. 250?nm, consisting of primary nanoparticles approximately 20–40?nm in size. When served as anode for lithium ion batteries, the mesoporous ZnMn₂O₄ maintains a large discharge capacity of 1138?mA?h?g^?1 at 0.5?A?g^?1 after 600 cycles as well as a stable discharge capacity of 597?mA?h?g^?1 at 6?A?g^?1 after 1000 cycles. The remarkable high-rate and long-cycle performances could be attributed to the small size of secondary/primary particles and robust 3D mesoporous structure, which are favorable for the improvement of electrochemical kinetics and the structural integrity of electrode during cycling. Additionally, this facile synthetic technique may be explored to prepare other submicron-sized metal oxides materials.     

MnCo2O4 nanospheres for improved lithium storage performance

Mesoporous MnCo₂O₄ nanospheres with an average diameter of approximately 480?nm have been synthesized by a polyvinyl pyrrolidone (PVP)-assisted solvothermal method followed by thermal annealing. MnCo₂O₄ nanospheres consist of many nanoparticles having sizes in range of 20–50?nm, the specific area of the sample being 24.4?m² g^?1. When used as the anode material for lithium ion batteries, the mesoporous MnCo₂O₄ nanospheres show not only an excellent cycling stability, but also an outstanding rate capability. More specially, the discharge capacities of 749.1 and 629.6?mA?h?g^?1 can be retained at current densities of 200 and 400?mA?g^?1 after 50 cycles, respectively. In addition, the average discharge capacities of 1013.8, 827.1, 770.6, 733.3, 697.3, 651.4 and 522.4?mA?h?g^?1 could be observed at current densities of 100, 200, 400, 600, 800, 1000 and 2000?mA?g^?1, respectively. The improved cycling stability and rate capability can be ascribed to two unique structural features of mesoporous MnCo₂O₄ nanospheres: namely, the mesoporous nature of electrode materials which can help to reduce the volume variation during repeated lithiation/delithiation processes, and the nanostructure which can provide a shortened Li⁺ transmission path. The current synthesis approach can be easily spread to prepare other binary metal oxides, including Co-free anode materials.     

Carbon-coated Bi5Nb3O15 as anode material in rechargeable batteries for enhanced lithium storage

Bismuth can alloy with lithium to generate Li₃Bi with the volumetric capacity of about 3765 mAh cm^?3 (386 mAh g^?1), rendering bismuth-based materials as attractive alloying-type electrode materials for rechargeable batteries. In this work, bismuth-based material Bi₅Nb₃O₁₅ @C is fabricated as anode material through a traditional solid-state reaction with glucose as carbon source. Bi₅Nb₃O₁₅ @C composite is well dispersed, with small particle size of 0.5–2.0?µm. The electrochemical performance of Bi₅Nb₃O₁₅ @C is reinforced by carbon-coated layer as desired. The Bi₅Nb₃O₁₅ @C exhibits a high specific capacity of 338.56 mAh g^?1 at a current density of 100?mA?g^?1. And it also presents an excellent cycling stability with a capacity of 212.06 mAh g^?1 over 100 cycles at 100?mA?g^?1. As a comparison, bulk Bi₅Nb₃O₁₅ without carbon-coating only remains 319.62 mAh g^?1 at 100?mA?g^?1, revealing poor cycle and rate performances. Furthermore, in-situ X-ray diffraction experiments investigate the alloying/dealloying behavior of Bi₅Nb₃O₁₅ @C. These insights will benefit the discovery of novel anode materials for lithium-ion batteries.     

In-situ grown hierarchical ZnCo2O4 nanosheets on nickel foam as binder-free anode for lithium ion batteries

Nickle foam-supported hierarchical ZnCo₂O₄ nanosheets was prepared via a facile solution-based method. Porous ZnCo₂O₄ nanosheets were in-situ grown on current collector, forming a binder-free electrode. When evaluated as anode for Lithium ion batteries (LIB_S), the binder-free electrode showed an attractive electrochemical performance. A reversible capacity of 773?mAh?g^?1 could be stably delivered after a 500-cycle test at a current density of 0.25?A?g^?1, with a high capacity retention of 87%. The electrode could maintain a high reversible capacity of 245?mA?h?g^?1 even at an elevated current density of 8.0?A?g^?1. Integrated structure and rich porosity of the binder-free electrode were believed to contribute to the superior performance. Thus, the Nickle foam-supported ZnCo₂O₄ electrode is a promising anode for high performance LIBs in the coming future.     

Synthesis of dandelion-like V2O3/C composite with bicontinuous 3D hierarchical structures as an anode for high performance lithium ion batteries

The dandelion-like V₂O₃/C composite was synthesized by a simple and facile template-free solvothermal method followed by a suitable thermal treatment. The dandelion-like V₂O₃/C composite is constructed by bicontinuous 3D hierarchical structures, which are formed by interconnected nanoparticles and interconnected pores, respectively. Moreover, the surface of interconnected nanoparticles is uniformly coated with an ultrathin carbon layer. Upon evaluation as an anode material for LIBs, the as-synthesized product shows superior electrochemical performance. Under the current density of 0.1?A?g^?1, the specific discharge capacity of V₂O₃/C composite is 737?mA?h?g^?1 after 100 cycles. Moreover, after 1000 cycles at a high current density of 2?A?g^?1, the sample exhibits a discharge capacity of 315?mA?h?g^?1 which is 94% of the first-cycle discharge capacity. This excellent electrochemical performance can be ascribed to its unique hierarchical structure with 3D interconnected nanopores and uniform carbon coating.     

Super-thin LiV3O8 nanosheets/graphene sandwich-like nanostructures with ultrahigh lithium ion storage properties

With the thickness less than 5?nm, super-thin LiV₃O₈ nanosheets have already been successfully synthesized by transformation from super-thin V₂O₅·xH₂O nanosheets, moreover, super-thin LiV₃O₈ nanosheets@graphene (LVO/G) sandwich-like layer-by-layer nanostructures were successfully obtained via a facile self-assembly method and annealing treatment. Such interesting LVO/G nanostructures as cathodes for lithium ion batteries not only show high capacity up to 397.2?mA?h?g^?1 and outstanding rate capabilities (171?mA?h?g^?1 at 10?C, 112?mA?h?g^?1 at 15?C), but also present super-long cycle performance (301.2?mA?h?g^?1 after 500 cycles at 1?C). As far as we known, the LVO/G cathodes exhibit ultrahigh lithium storage performances even much higher than those of previously reported literatures of LiV₃O₈, which demonstrates that such sandwich-like layer-by-layer LVO/G nanostructures is a potential candidate cathode material for the next generation of batteries.     

Effect of calcination temperature on morphology and electrochemical performance of PbLi2Ti6O14

As a promising anode material, PbLi₂Ti₆O₁₄ has attracted the attention of many researchers. In this work, a series of PbLi₂Ti₆O₁₄ are prepared by solid state method at five different calcination temperatures and used as anode materials in lithium ion batteries. Through a series of tests, the results show that the phase purity, morphology and electrochemical performance of PbLi₂Ti₆O₁₄ can be seriously influenced by calcination temperature. When the calcination temperature is 900?°C, the phase-pure PbLi₂Ti₆O₁₄ can be obtained with relatively small particle size, excellent cycle performance and outstanding lithium ion diffusion behavior. It provides an initial charge capacity of 151.3?mA?h?g^?1 at 100?mA?g^?1. After 100 cycles, it shows a reversible capacity of 142.0?mA?h?g^?1 with superior capacity retention of 93.85%. In contrast, PbLi₂Ti₆O₁₄ formed at 800?°C displays an unsatisfactory performance due to the presence of impurity, even though it has the smallest particle size and the largest lithium ion diffusion coefficient among the five samples. The reversible capacity is only 82.6?mA?h?g^?1 after 100 cycles with capacity retention of 53.9%. In order to further study the lithium ion diffusion behavior of PbLi₂Ti₆O₁₄, the in-situ X-ray diffraction technique is also implemented. It is found that during the lithiation/delithiation process, the stable framework can effectively inhibit the volume change and ensures the excellent electrochemical performance of PbLi₂Ti₆O₁₄.     

Constructing three-dimensional Li-transport channels within the Fe3O4@SiO2@RGO composite to improve its electrochemical performance in Li-ion batteries

Magnetite Fe₃O₄ particles are usually pulverized when used as the anode material for Li-ion batteries and thus the solid electrolyte interface film grows on the surface progressively, leading to inferior cycling performance and poor rate capability. To solve these issues, core-shell Fe₃O₄@SiO₂ particles are wrapped by reduced graphene oxide (RGO), and meso-/micro-pores are produced not only in the SiO₂ layers but also in the RGO nanosheets by chemical etching, forming three-dimensional (3D) continuous channels for Li⁺ transportation. Benefiting from this unique structure, the as-prepared Fe₃O₄@mSiO₂@RGO composite can deliver a capacity of 1630 mA h g⁻¹ at 0.1 A g⁻¹ over the potential range of 0.01–3.00 V (vs. Li⁺/Li) in the first discharge along with an initial coulombic efficiency of 86%, and can retain the capacity of 514 mA h g⁻¹ at 5 A g⁻¹ after 1000 cycles, exhibiting an outstanding rate capability and a long-term span life. The results indicate that pseudocapacitive behavior enables this composite to charge/discharge fast while the porous SiO₂ shell and RGO nanosheets effectively accommodate the volume change of the Fe₃O₄ particles during cycling. Our findings provide a feasible strategy for improving the electrochemical properties of the Fe₃O₄ anode in Li-ion batteries.     

V2O3/rGO composite as a potential anode material for lithium ion batteries

V₂O₃ is a promising anode material and has attracted the interests of researchers because of its high theoretical capacity of 1070?mAh?g^?1, low discharge potential, inexpensiveness, abundant sources, and environmental friendliness. However, the development and application of V₂O₃ have been hindered by the low conductivity and drastic volume change of V₂O₃ composites. In this work, V₂O₃/reduced graphene oxide (rGO) nanocomposites are successfully prepared through a facile solvothermal method and annealing process. In this synthesis protocol, V₂O₃ nanoparticles (NPs) are encapsulated by rGO. This unique structure enables rGO to inhibit volume changes and improve the ion and electronic conductivity of V₂O₃. In addition, V₂O₃ NPs, which exhibit sizes of 5–40?nm, are uniformly dispersed on rGO sheets without aggregation. The Li⁺ storage behavior of V₂O₃/rGO is systematically investigated in the potential range 0.01–3.0?V. The V₂O₃/rGO nanocomposite can achieve a high reversible specific capacity of 823.4?mAh?g^?1 under the current density of 0.1?A?g^?1, and 407.3 mAh g^?1 under the high current density of 4.0?A?g^?1. The results of this study provide insight into the fabrication of rGO-based functional materials with extensive applications.     

Porous CoTiO3 microbars as super rate and long life anodes for sodium ion batteries

Porous CoTiO₃ microbars have been successfully prepared by a facile solution way followed by thermal annealing in air. When evaluated as electrode materials for sodium ion batteries, unique 1D porous structure demonstrates remarkable sodium storage properties. The resultant CoTiO₃ microbar electrodes exhibit not only higher discharge capacity (135.5?mA?h?g^?1 at 300?mA?g^?1 after 500 cycles), but also more enhanced rate performance compared to those of CoTiO₃ microparticle electrodes. The new findings reported here highlight the possibility for designing high-performance anode materials for sodium ion batteries.     

Mesoporous Ti2Nb10O29 microspheres constructed by interconnected nanoparticles as high performance anode material for lithium ion batteries

Mesoporous Ti₂Nb₁₀O₂₉ microspheres are prepared through a solvothermal method in isopropanol-glycerol solvent followed by calcination treatment. The Ti₂Nb₁₀O₂₉ microspheres with diameter in the range between 1.0 and 2.0?µm are assembled from nanoparticles. The special hierarchical mesoporous structure of Ti₂Nb₁₀O₂₉ microspheres can reduce the Li⁺ ions diffusion distance and supply large interfacial area between electrolyte and electrode, endowing them with better electrochemical properties compared to Ti₂Nb₁₀O₂₉ nanoparticles. At different current densities of 1, 5, 10, 20 and 30?C, the first discharge capacity of mesoporous microspheres is respectively 268.9, 218.5, 205.3, 180.5, and 158.1 mA?h g^?1. By contrast, the corresponding values of Ti₂Nb₁₀O₂₉ nanoparticles are quickly reduced from 254.6, 196.3, 159.4, 127.5, to 99.0 mA?h g^?1. It worth noting that Ti₂Nb₁₀O₂₉ microspheres exhibit excellent rate capacities. Furthermore, at a current density of 10?C, the specific capacity of Ti₂Nb₁₀O₂₉ microspheres can be maintained at 173.5 mA?h g^?1 after 500 cycles, with 86.8% retention of the first discharge capacity. These results suggest that the Ti₂Nb₁₀O₂₉ mesoporous microspheres would be developed as potential anodic materials for high performance lithium-ion batteries.     

Microwave-assisted one-pot synthesis of SnC2O4/graphene composite anode material for lithium-ion batteries

Currently, SnC₂O₄ is considered as one of the most promising anode materials for high-energy lithium-ion batteries (LIBs) because its charge capacity is higher than that of metal oxides. Herein, a facile microwave-assisted solvothermal method was employed to obtain SnC₂O₄/GO composites within only 30?min, which is time-efficient. The amount of SnC₂O₄ was increased to 95.3?wt% to improve the capacity of the composite. Pure SnC₂O₄ with a high specific surface area of 19.6?m² g^?1 without any other tin compound was used for fabrication. The SnC₂O₄/GO composite exhibited excellent electrochemical performance, with reversible discharge/charge capacity of 657/659?mA?h?g^?1 after 100 cycles at 0.2?A?g^?1. Furthermore, at high current densities of 1.0 and 2.0?A?g^?1, the SnC₂O₄/GO composite anode exhibited high reversible discharge/charge capacities of 553/552 and 418/414?mA?h?g^?1, respectively, after 200 cycles at room temperature. These improvements were likely obtained because SnC₂O₄ was well composited with graphene, which not only offered rapid electron transfer but also released the tension produced by the volumetric effect during repeated lithiation/delithiation. Cyclic voltammetry (CV) was also performed to further study the electrochemical reactions of SnC₂O₄/GO. The facile microwave-assisted solvothermal method used herein is considered as a highly efficient method to fabricate metal oxalate/graphene composites for use as anode materials in LIBs.     

Facile synthesis of hierarchical polycystic iron-nitride/phosphide hybrids microsphere constructed by CNTs for stable and enhanced lithium storage

Diverse Fe-based nitrides and phosphides have drawn considerable attention owing to their abundant source, high theoretical capacities, and environment benignity. However, it still remains a crucial challenge to develop a facile preparation approach of robust Fe-based anode materials for the next-generation durable lithium-ion batteries. Herein, we constructed two type polycystic microsphere anode materials (Fe₂N@C/CNTs and FeP@C/CNTs) through a scalable industrial spray-drying technology combined with following chemical nitridation/phosphorization conversion strategy. Both the resultant Fe₂N@C/CNTs and FeP@C/CNTs materials exhibit unique hierarchical polycystic microsphere structure and improved conductive network caused by the incorporation of amorphous carbon and dense CNTs coating layers. The unique structure merits endow these capabilities of facilitating electrons/ions transport and accommodating notorious volume change during charge-discharge cycling. Consequently, the Fe₂N@C/CNTs and FeP@C/CNTs anode materials deliver enhanced rate capability (216 and 232?mA?h?g^?1, respectively, at a high current density of 5?A?g^?1) and durable cycling stability with reversible capacities of 489 and 571?mA?h?g^?1 at 0.5?A?g^?1 after 500 cycles, respectively. In addition, this work also provides a transplantable preparation strategy for other conversion-type anode materials with poor electrical conductivity and large volume effect.     

High reversible capacity of SnO2/graphene nanocomposite as an anode material for lithium-ion batteries

A gas–liquid interfacial synthesis approach has been developed to prepare SnO₂/graphene nanocomposite. The as-prepared nanocomposite was characterized by X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, and Brunauer–Emmett–Teller measurements. Field emission scanning electron microscopy and transmission electron microscopy observation revealed the homogeneous distribution of SnO₂ nanoparticles (2–6 nm in size) on graphene matrix. The electrochemical performances were evaluated by using coin-type cells versus metallic lithium. The SnO₂/graphene nanocomposite prepared by the gas–liquid interface reaction exhibits a high reversible specific capacity of 1304 mAh g⁻¹ at a current density of 100 mA g⁻¹ and excellent rate capability, even at a high current density of 1000 mA g⁻¹, the reversible capacity was still as high as 748 mAh g⁻¹. The electrochemical test results show that the SnO₂/graphene nanocomposite prepared by the gas–liquid interfacial synthesis approach is a promising anode material for lithium-ion batteries.     

One-step electrosynthesis of MnO2/rGO nanocomposite and its enhanced electrochemical performance

We present a facile one-step electrochemical approach to generate MnO₂/rGO nanocomposite from a mixture of Mn₃O₄ and graphene oxide (GO). The electrochemical conversion of Mn₃O₄ into MnO₂ through potential cycling is expedited in the presence of GO while the GO is reduced into reduced graphene oxide (rGO). The MnO₂ nanoparticles are evenly distributed on the rGO nanosheets and act as the spacer to prevent rGO nanosheets from restacking. This unique structure provides high electroactive surface area (1173?m² g^?1) that improves ions diffusion within the MnO₂/rGO structure. As a result, the MnO₂/rGO nanocomposite exhibits high specific capacitance of 473?F?g^?1 at 0.25?A?g^?1, which is remarkably higher (3 times) than the Mn₃O₄/GO prior conversion. In addition, the electrosynthesized nanocomposite shows higher conductivity and excellent potential cycling stability of 95% at 2000 cycles.     

High capacity ZnFe2O4 anode material for lithium ion batteries

A nanostructured ternary transition metal oxide, ZnFe₂O₄, is synthesized via the simple polymer pyrolysis method. The characteristics of the material are examined by thermogravimetry, Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The electrochemical test results show that this method of ZnFe₂O₄ synthesis produces high specific capacities and good cycling performance, with an initial specific capacity as high as 1419.6 mAh g⁻¹ at first discharge that is maintained at over 800 mAh g⁻¹ even after 50 charge–discharge cycles. The electrode also presents a good rate capability, with a high rate of 4C (1C = 928 mA g⁻¹), a reversible specific capacity that can be as high as 400 mAh g⁻¹. ZnFe₂O₄ is a potential alternative to high-performance nanostructured anode material in lithium ion batteries.     

In-situ synthesis of reduced graphene oxide wrapped Mn3O4 nanocomposite as anode materials for high-performance lithium-ion batteries

We report a novel in-situ symbiosis method to prepare reduced graphene oxide wrapped Mn₃O₄ nanoparticles (rGO/Mn₃O₄) with uniform size about 50 nm as anodes for lithium-ion batteries (LIBs), which can simplify the preparation process and effectively reduce pollution. The rGO/Mn₃O₄ nanocomposite exhibited a reversible specific capacity of 795.5 mAh g^?1 at 100 mA g^?1 after 200 cycles (capacity retention: 87.4%), which benefits from the unique structural advantages and the synergistic effect of rGO and Mn₃O₄. The Mn₃O₄ nanoparticles encapsulated among the rGO nanosheets exhibited good electrochemical activity, and the multilayer wrinkled rGO sheets provided a stable 3D conduction channel for Li⁺/e^? transport. The rGO/Mn₃O₄ nanocomposite is a promising anode candidate for advanced LIBs with excellent cycling performance and rate performance. Furthermore, this new preparation method can be extended to green and economical synthesis of advanced graphene/manganese-based nanocomposites.     

Enhancing the lithium storage capabilities of TiO2 nanoparticles using delaminated MXene supports

MXenes, an emerging family of two-dimensional materials, were promising electrode materials due to their excellent electronic conductivity and hydrophilicity. MXenes exhibit extraordinary rate performance and cycling stability when serving as the anode materials for Li-ion batteries, but they have relatively low capacities. We thus prepared Ti₃C₂T_x/TiO₂ composites using a simple route to coat TiO₂ nanoparticles onto the delaminated few-layered MXenes, which functioned as spacers in the composite to suppress the restacking of MXene layers. The sample demonstrated excellent performance in the galvanostatic charge-discharge test, where a reversible capacity of 143?mA?h?g^?1 could still be maintained after 200 cycles at 0.5?A?g^?1 and a distinct plateau region could be clearly observed in the charge-discharge profiles. Density Theory Function calculation revealed that the hybridization of few-layered MXene was able to improve the structural stability of the composite during the insertion/de-insertion of Li atoms.     

Highly reversible Co3O4/graphene hybrid anode for lithium rechargeable batteries

A Co₃O₄/graphene hybrid material was fabricated using a simple in situ reduction process and demonstrated as a highly reversible anode for lithium rechargeable batteries. The hybrid is composed of 5 nm size Co₃O₄ particles uniformly dispersed on graphene, as observed by transmission electron microscopy, atomic force microscopy, Raman spectroscopy and X-ray diffraction analysis. The Co₃O₄/graphene anode can deliver a capacity of more than 800 mA h g⁻¹ reversibly at a 200 mA g⁻¹ rate in the voltage range between 3.0 and 0.001 V. The high reversible capacity is retained at elevated current densities. At a current rate as high as 1000 mA g⁻¹, the Co₃O₄/graphene anode can deliver more than 550 mA h g ⁻¹, which is significantly higher than the capacity of current commercial graphite anodes. The superior electrochemical performance of the Co₃O₄/graphene is attributed to its unique nanostructure, which intimately combines the conductive graphene network with uniformly dispersed nano Co₃O₄ particles.     

Novel high-capacity hybrid layered oxides NaxLi1.5-xNi0.167Co0.167Mn0.67O2 as promising cathode materials for rechargeable sodium ion batteries

Relatively low capacity is a technological bottleneck of the development of sodium ion batteries. Herein, we present a series of hybrid layered cathode materials Na_xLi_1.5-xNi_0.167Co_0.167Mn_0.67O₂ (x?=?0.5, 0.6, 0.7, 0.8, 0.9, 1) with composite crystalline structures, which are prepared by co-precipitation method. The combined analysis of XRD, SEM and TEM reveals that the materials are composed of P2 structure, α-NaFeO₂ structure and small amount of Li₂MnO₃. Among the as-prepared materials, Na_0.6Li_0.9Ni_0.167Co_0.167Mn_0.67O₂ delivers an initial reversible capacity of 222?mA?h?g^?1 at 20?mA?g^?1. Even at 100?mA?g^?1, it shows a remarkable discharge capacity of 125?mA?h?g^?1 in the first cycle and remains 60?mA?h?g^?1 after 300 cycles. Such high capacity is achieved by the specific composite structure and sodium ions are proved to be able to intercalate/deintercalate in Li_1.5Ni_0.167Co_0.167Mn_0.67O₂ with α-NaFeO₂ structure. The Ex-situ XRD results of Na_0.6Li_0.9Ni_0.167Co_0.167Mn_0.67O₂ in the first cycle show that the P2 structure is well maintained along with irreversible phase transition of α-NaFeO₂ structure, which is responsible for the long-term capacity fading. Owing to the high discharge capacity, the novel hybrid layered oxides Na_xLi_1.5-xNi_0.167Co_0.167Mn_0.67O₂ with composite structures can be considered as promising cathode materials to promote progress toward sodium-ion batteries.