FeS2@TiO2 nanorods as high-performance anode for sodium ion battery

Sodium-ion battery (SIB) is an ideal device that could replace lithium-ion battery (LIB) in grid-scale energy storage system for power because of the low cost and rich reserve of raw material. The key challenge lies in developing electrode materials enabling reversible Na⁺ insertion/desertion and fast reaction kinetics. Herein, a core-shell structure, FeS₂ nanoparticles encapsulated in biphase TiO₂ shell (FeS₂@TiO₂), is developed towards the improvement of sodium storage. The diphase TiO₂ coating supplies abundant anatase/rutile interface and oxygen vacancies which will enhance the charge transfer, and avoid severe volume variation of FeS₂ caused by the Na⁺ insertion. The FeS₂ core will deliver high theoretical capacity through its conversion reaction mechanism. Consequently, the FeS₂@TiO₂ nanorods display notable performance as anode for SIBs including long-term cycling performance (637.8 mA·h·g^-1 at 0.2 A·g^-1 after 300 cycles, 374.9 mA·h·g^-1 at 5.0 A·g^-1 after 600 cycles) and outstanding rate capability (222.2 mA·h·g^-1 at 10 A·g^-1). Furthermore, the synthesized FeS₂@TiO₂ demonstrates significant pseudocapacitive behavior which accounts for 90.7% of the Na⁺ storage, and efficiently boosts the rate capability. This work provides a new pathway to fabricate anode material with an optimized structure and crystal phase for SIBs.     

Effective enhancement of the electrochemical properties for Na2FeP2O7/C cathode materials by boron doping

In recent years, the composite materials based on polyanionic frameworks as secondary sodium ion battery electrode material have been developed in large-scale energy storage applications due to its safety and stability. The Na₂FeP₂O₇/C (theoretical capacity 97 mA·h·g^-1) is recognized as optimum Na-storage cathode materials with a trade-off between electrode performance and cost. In the present work, The Na₂FeP₂O₇/C and boron-doped Na₂FeP_2-BO₇/C composites were synthesized via a novel method of liquid phase combined with high temperature solid phase. The non-metallic element B doping not only had positive influence on the crystal structure stability, Na⁺ diffusion and electrical conductivity of Na₂FeP₂O₇/C, but also contributed to the high-value recycling of B element in waste borax. The structure and electrochemical properties of the cathode material were investigated via X-ray diffraction (XRD), scanning electron microscopy (SEM), The X-ray photoelectron spectroscopy (XPS), electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), and charge/discharge cycling. The results showed that different amounts of boron doping had positive effects on the structure and electrochemical properties of the material. The initial charge/discharge performances of born doped materials were improved in comparison to the bare Na₂FeP₂O₇/C. The cycle performance of the Na₂FeP_1.95B_0.05O₇/C showed an initial reversible capacity of 74.8 mA·h·g^-1 and the high capacity retention of 91.8% after 100 cycles at 1.0 C, while the initial reversible capacity of the bare Na₂FeP₂O₇/C was only 66.2 mA·h·g^-1. The improvement of apparent Na⁺ diffusion and electrical conductivity due to B doping were verified by the EIS test and CVs at various scan rate. The experimental results from present work is useful for opening new insight into the contrivance and creation of applicable sodium polyanionic cathode materials for high-performance.     

Lithium Storage Performance of Hollow and Core/Shell TiO2 Microspheres Containing Carbon☆

TiO2 microspheres containing carbon have been synthesized viaa one-pot hydrothermal process using CTAB as the mesoporous template and nanoparticle stabilizer and Ti(SO4)2 and sucrose as titanium and ca...     

原位合成的介孔TiO2-B/锐钛微粒:改善的锂离子电池阳极材料（英文）

Mesoporous TiO2-B/anatase microparticles have been in-situ synthesized from K2Ti2O5 without template. The TiO2-B phase around the particle surface accelerates the diffusion of charges through the interface, while the anatase phase in the core maintains the capacity stability. The heterojunction interface between the main polymorph of anatase and the trace of TiO2-B exhibits promising lithium ion battery performance. This trace of 5%(by mass) TiO2-B determined by Raman spectra brings the first discharge capacity of this material to 247 mA·h·g?1, giving 20%improvement com-pared to the anatase counterpart. Stability testing at 1 C reveals that the capacity maintains at 171 mA·h·g?1, which is better than 162 mA·h·g?1 for single phase anatase or 159 mA·h·g?1 for TiO2-B. The mesoporous TiO2-B/anatase microparticles also show superior rate performance with 100 mA·h·g?1 at 40 C, increased by nearly 25%as compared to pure anatase. This opens a possibility of a general design route, which can be applied to other metal oxide electrode materials for rechargeable batteries and supercapacitors.     

Self-assembled MoS2/C nanoflowers with expanded interlayer spacing as a high-performance anode for sodium ion batteries

Two-dimensional (2D) MoS₂ nanomaterials have been extensively studied due to their special structure and high theoretical capacity, but it is still a huge challenge to improve its cycle stability and achieve superior fast charge and discharge performance. Herein, a facile one-step hydrothermal method is proposed to synthetize an ordered and self-assembled MoS₂ nanoflower (MoS₂/C NF) with expanded interlayer spacing via embedding a carbon layer into the interlayer. The carbon layer in the MoS₂ interlayer can speed the transfer of electrons, while the nanoflower structure promotes the ions transport and improves the structural stability during the charging/discharging process. Therefore, MoS₂/C NF electrode exhibits exceptional rate performance (318.2 and 302.3 mA·h·g^-1 at 5.0 and 10.0 A·g^-1, respectively) and extraordinary cycle durability (98.8% retention after 300 cycles at a current density of 1.0 A·g^-1). This work provides a simple and feasible method for constructing high-performance anode composites for sodium ion batteries with excellent cycle durability and fast charge/discharge ability.     

A facile preparation of 3D flower-shaped Ni/Al-LDHs covered by β-Ni(OH)2 nanoplates as superior material for high power application

In the present study, we propose a novel electrode material of β-nickel hydroxide covering nickel/aluminum layered double hydroxides via a facile complexation-precipitation method. The as-obtained materials with 3-dimensional nanostructures are further utilized as highly capable electrode material in nickel-metal hydride batteries. The electrochemical test results demonstrated the β-nickel hydroxide covering nickel/aluminum-layered double hydroxides with 28% of β-nickel hydroxide provided a superior specific capacity value of 452 mA·h·g^-1 in a current density of 5 A·g^-1 using 6 M KOH as electrolyte as compared with other materials. In addition, the optimized sample displays an outstanding cyclic stability along with a huge specific capacity value of 320 mAh·g^-1, and very small decay rate of 3.3% at 50 A·g^-1 after 3000 cycles of charge/discharge test. These indicate that the newly designed material with nanostructures not only provides an efficient contact interface between electrolyte and active species and facilitates the transport of electrons and ions, but also protects the 3-dimensional nickel/aluminum layered double hydroxides, achieving a high specific capacity, fast redox reaction and excellent long-term cyclic stability. Therefore, the β-nickel hydroxide covering nickel/aluminum layered double hydroxides with superior electrochemical performance is predictable to be a gifted electrode material in nickel-metal hydride batteries.     

Nitrogen-doped carbon stabilized LiFe0.5Mn0.5PO4/rGO cathode materials for high-power Li-ion batteries

Exploring high ion/electron conductive olivine-type transition metal phosphates is of vital significance to broaden their applicability in rapid-charging devices. Herein, we report an interface engineered LiFe_0.5Mn_0.5PO₄/rGO@C cathode material by the synergistic effects of rGO and polydopamine-derivedN-doped carbon. The well-distributed LiFe_0.5Mn_0.5PO₄ nanoparticles are tightly anchored on rGO nanosheet benefited by the coating of N-doped carbon layer. The design of such an architecture can effectively suppress the agglomeration of nanoparticles with a shortened Li⁺ transfer path. Meantime, the high-speed conducting network has been constructed by rGO and N-doped carbon, which exhibits the face-to-face contact with LiFe_0.5Mn_0.5PO₄ nanoparticles, guaranteeing the rapid electron transfer. These profits endow the LiFe_0.5Mn_0.5PO₄/rGO@C hybrids with a fast charge-discharge ability, e.g. a high reversible capacity of 105 mAh·g^-1 at 10 C, much higher than that of the LiFe_0.5Mn_0.5PO₄@C nanoparticles (46 mA·h·g^-1). Furthermore, a 90.8% capacity retention can be obtained even after cycling 500 times at 2 C. This work gives a new avenue to fabricate transition metal phosphate with superior electrochemical performance for high-powerLi-ion batteries.     

Synthesis of Chl@Ti3C2 composites as an anode material for lithium storage

Two-dimensional (2D) titanium carbide MXene Ti₃C₂ has attracted significant research interest in energy storage applications. In this study, we prepared Chl@Ti₃C₂ composites by simply mixing a chlorophyll derivative (e.g., zinc methyl 3-devinyl-3-hydroxymethyl- pyropheophorbide a (Chl)) and Ti₃C₂ in tetrahydrofuran, where the Chl molecules were aggregated among the multi-layered Ti₃C₂ MXene or on its surface, increasing the interlayer space of Ti₃C₂. The as-prepared Chl@Ti₃C₂ was employed as the anode material in the lithium-ion battery (LIB) with lithium metal as the cathode. The resulting LIB exhibited a higher reversible capacity and longer cycle performance than those of LIB based on pure Ti₃C₂, and its specific discharge capacity continuously increased along with the increasing number of cycles, which can be attributed to the gradual activation of Chl@Ti₃C₂ accompanied by the electrochemical reactions. The discharge capacity of 1 wt-% Chl@Ti₃C₂ was recorded to be 325 mA·h·g^–1 at the current density of 50 mA·g^–1 with a Coulombic efficiency of 56% and a reversible discharge capacity of 173 mA·h·g^–1 at the current density of 500 mA·g^–1 after 800 cycles. This work provides a novel strategy for improving the energy storage performance of 2D MXene materials by expanding the layer distance with organic dye aggregates.     

Facile synthesis of spinel LiNi0.5Mn1.5O4 as 5.0 V-class high-voltage cathode materials for Li-ion batteries

LiNi_0.5Mn_1.5O₄ and LiMn₂O₄ with novel spinel morphology were synthesized by a hydrothermal and post-calcination process. The synthesized LiMn₂O₄ particles (5-10 μm) are uniform hexahedron, while the LiNi_0.5Mn_1.5O₄ has spindle-like morphology with the long axis 10-15 μm, short axis 5-8 μm. Both LiMn₂O₄ and LiNi_0.5Mn_1.5O₄ show high capacity when used as cathode materials for Li-ion batteries. In the voltage range of 2.5-5.5 V at room temperature, the LiNi_0.5Mn_1.5O₄ has a high discharge capacity of 135.04 mA·h·g^-1 at 20 mA·g^-1, which is close to 147 mA·h·g^-1 (theoretical capacity of LiNi_0.5Mn_1.5O₄). The discharge capacity of LiMn₂O₄ is 131.08 mA·h·g^-1 at 20 mA·g^-1. Moreover, the LiNi_0.5Mn_1.5O₄ shows a higher capacity retention (76%) compared to that of LiMn₂O₄ (61%) after 50 cycles. The morphology and structure of LiMn₂O₄ and LiNi_0.5Mn_1.5O₄ are well kept even after cycling as demonstrated by SEM and XRD on cycled LiMn₂O₄ and LiNi_0.5Mn_1.5O₄ electrodes.     

锂离子电池负极材料Li4Ti5O12/C的制备与表征

针对Li₄Ti₅O₁₂导电性和倍率性能差的缺陷,以PEG为碳源采用溶胶-凝胶法制备出电池负极材料Li₄Ti₅O₁₂/C,考察不同分子量聚乙二醇PEG(400、600、1000)做碳源制备的Li₄Ti₅O₁₂/C复合材料电化学性能的优劣,采用热重分析仪(TG)、X射线衍射仪(XRD)、扫描电镜(SEM)、透射电镜(TEM)、恒流充放电、倍率放电、交流阻抗(EIS)等方法对材料进行了结构表征和电化学性能测试。结果表明:以PEG1000为碳源时得到的Li₄Ti₅O₁₂/C,0.1C下首次放电比容量为143.5 mA·h·g^-1,2C的倍率下仍然保持了105 mA·h·g^-1的比容量,容量保持率达到73.17%,并且此材料有最小的电阻,在大电流条件下有良好的电化学性能。     

Hybrid CuO-Co3O4 nanosphere/RGO sandwiched composites as anode materials for lithium-ion batteries

Hybrid CuO-Co₃O₄ nanosphere building blocks have been embedded between the layered nanosheets of reduced graphene oxides with a three dimensional (3D) hybrid architecture (CuO-Co₃O₄-RGO), which are successfully applied as enhanced anodes for lithium-ion batteries (LIBs). The CuO-Co₃O₄-RGO sandwiched nanostructures exhibit a reversible capacity of~847 mA·h·g^-1 after 200 cycles' cycling at 100 mA·g^-1 with a capacity retention of 79%. The CuO-Co₃O₄-RGO compounds show superior electrochemical properties than the comparative CuO-Co₃O₄, Co₃O₄ and CuO anodes, which may be ascribed to the following reasons:the hybridizing multicomponent can probably give the complementary advantages; the mutual benefit of uniformly distributing nanospheres across the layered RGO nanosheets can avoid the agglomeration of both the RGO nanosheets and the CuO-Co₃O₄ nanospheres; the 3D storage structure as well as the graphene wrapped composite could enhance the electrical conductivity and reduce volume expansion effect associated with the discharge-charge process.     

Carbon-coated lithium titanate: effect of carbon precursor addition processes on the electrochemical performance

In this paper,two carbon-coated lithium titanate(LTO-C1 and LTO-C2)composites were synthesized using the ball-milling-assisted calcination method with different carbon precursor addition processes.The physical and electrochemical properties of the as-synthesized negative electrode materials were characterized to investigate the effects of two carbon-coated LTO synthesis processes on the electrochemical performance of LTO.The results show that the LTO-C2 synthesized by using Li2CO3 and TiO2 as the raw materials and sucrose as the carbon source in a one-pot method has less polarization during lithium insertion and extraction,minimal charge transfer impedance value and the best electrochemical performance among all samples.At the current density of 300 mA·h·g^-1,the LTO-C2 composite delivers a charge capacity of 126.9 mA·h·g^-1,and the reversible capacity after 300 cycles exceeds 121.3 mA·h·g^-1 in the voltage range of 1.0–3.0 V.Furthermore,the electrochemical impedance spectra show that LTO-C2 has higher electronic conductivity and lithium diffusion coefficient,which indicates the advantages in electrode kinetics over LTO and LTO-C1.The results clarify the best electrochemical properties of the carbon-coated LTO-C2 composite prepared by the one-pot method.     

Assembly of N- and P-functionalized carbon nanostructures derived from precursor-defined ternary copolymers for high-capacity lithium-ion batteries

Synthesis of new carbon nanostructures with tunable properties is vital for precisely regulating electrochemical performance in the wide applications. Herein, we report a novel approach for the oxidative polymerization of N- and P-bearing copolymers from the self-assembly of three different monomers (aniline, pyrrole, and phytic acid), and further prepare the respective carbon nanostructures with relatively consistent N dopant (6.2%–8.0%, atom) and varying P concentrations (0.4%–2.8%, atom) via controllable pyrolysis. The impacts of phytic acid addition on the compositional, structural, and morphological evolution of the copolymers and the resulting nanocarbons are well studied through a spectrum of characterizations including N₂ sorption, Fourier transform infrared spectroscopy, gel permeation chromatograph, scanning/transmission electron microscopy, and X-ray photoelectron spectroscopy. Gradual fragmentation of the nanosphere structures is evidenced with increasing addition of phytic acid, leading to different nanostructures from hollow nanospheres to 3D aggregates. Nanocarbons decorated with N and P dopants from pyrolysis are further utilized as anode materials in lithium-ion batteries, demonstrating enhanced electrochemical performance, i.e., a reversible capacity of 380 mA·h·g^-1 at 2 A·g^-1 for NPC-0.5 during 200 cycles. The superior performance originates from the balanced porosity, and appropriate concentrations of P and pyrrolic N, thus pointing the direction for designing high-performance anode materials.     

Novel synthesis of SiOx/C composite as high-capacity lithium-ion battery anode from silica-carbon binary xerogel

Micro/nanostructured SiO_x/C composite was firstly synthesized by carbothermal reduction of silica-carbon binary xerogel. The homogeneous dispersion feature of the two components in binary xerogel contributes to effectively carbothermally reduce the O/Si atomic ratio, enhancing the electrochemical activity of the SiO_x component.The micron-sized SiO_x/C spheres are composed of many near-spherical nanoparticles. The synthesized SiO_x/C exhibits a stable and high reversible capacity of 830 m A·h·g~(-1) for 100 cycles, and excellent rate-capability. The homogeneous dispersion structure of phases, the micro/nanostructure and the high electrochemical activity of SiO_x component combinedly contribute the excellent electrochemical performance.     

Three-dimensional oxygen-doped porous graphene: Sodium chloride-template preparation,structural characterization and supercapacitor performances

Supercapacitor is a new type of energy storage device, which has the advantages of high-power property and long cycle life. In this study, three-dimensional graphene (3D-GN) with oxygen doping and porous structure was prepared from graphene oxide (GO) by an inexpensive sodium chloride (NaCl) template, as a promising electrode material for the supercapacitor. The structure, morphology, specific surface area, pore size, of the sample were characterized by XRD, SEM, TEM and BET techniques. The electrochemical performances of the sample were tested by CV and CDC techniques. The 3D-GE product is a three-dimensional nano material with hierarchical porous structures, its specific surface area is much larger than that of routine stacked graphene (GN), and it contains a large number of mesoporous and macropores, a small amount of micropores. The capacitance characteristics of the 3D-GN electrode material are excellent, showing high specific capacitance (173.5 F·g^-1 at 1 A·g^-1), good rate performance (109.2 F·g^-1 at 8 A·g^-1) and long cycle life (88% capacitance retention after 10,000 cycles at 8 A·g^-1)     

Enhanced electrochemical performance of garnet-based solid-state lithium metal battery with modified anodic and cathodic interfaces

Due to high ionic conductivity and wide electrochemical window, the garnet solid electrolyte is considered as the most promising candidate electrolyte for solid-state lithium metal batteries. However, the high contact impedance between metallic lithium and the garnet solid electrolyte surface seriously hampers its further application. In this work, a Li-(ZnO)_x anode is prepared by the reaction of zinc oxide with metallic lithium and in situ coated on the surface of Li_6.8La₃Zr_1.8Ta_0.2O₁₂(LLZTO). The anode can be perfectly bound to the surface of LLZTO solid electrolyte, and the anode/electrolyte interfacial resistance was reduced from 2319 to 33.75 Ω·cm². The Li-(ZnO)_0.15|LLZTO|Li-(ZnO)_0.15 symmetric battery exhibits a stable Li striping/plating process during charge-discharging at a constant current density of 0.1 mA·cm^-2 for 100 h at room temperature. Moreover, a Li-(ZnO)_0.15|LLZTO-SPE|LFP full battery, comprised of a polyethylene oxide-based solid polymer electrolyte (SPE) film as an interlayer between LiFePO₄ (LFP) cathode and LLZTO solid electrolyte, presents an excellent performance at 60 ℃. The discharge capacity of the full battery reaches 140 mA·h·g^-1 at 0.1 C and the capacity attenuation is less than 3% after 50 cycles.     

响应面法优化碳热还原合成LiFePO4/C的工艺参数（英文）

A statistically based optimization strategy is used to optimize the carbothermal reduction technology for the synthesis of LiFePO4/C using LiOH,FePO4 and sucrose as raw materials.The experimental data for fitting the response are collected by the central composite rotatable design(CCD).A second order model for the discharge ca-pacity of LiFePO4/C is expressed as a function of sintering temperature,sintering time and carbon content.The ef-fects of individual variables and their interactions are studied by a statistical analysis(ANOVA).The results show that the linear effects and the quadratic effects of sintering temperature,carbon content and the interactions among these variables are statistically significant,while those effects of sintering time are insignificant.Response surface plots for spatial representation of the model illustrate that the discharge capacity depends on sintering temperature and carbon content more than sintering time.The model obtained gives the optimized reaction parameters of sinter-ing temperature at 652.0 ℃,carbon content of 34.33 g?mol-1 and 8.48 h sintering time,corresponding to a dis-charge capacity of 150.8 mA·h·g-1.The confirmatory test with these optimum parameters gives the discharge ca-pacity of 147.2 and 105.1 mA·h·g-1 at 0.5 and 5 C,respectively.     

Influence of synergistic effect of LiNi0.8Co0.15Al0.05O2@Cr2O5 composite on the electrochemical properties

LiNi_(0.8)Co_(0.15)Al_(0.05)O_2@Cr_2O_5(NCA)@Cr_2 O_5 composite electrode combines the high rate-capability characteristics of NCA with the stability of Cr_2 O_5, playing a synergistic role in improving the cyclic stability, initial discharge capacity and the security of low cut-off voltage(2.0 V). When the mass ratio of Cr_2 O_5 in NCA is 45%(mass), the capacity retention rate increases from 58.5% without Cr_2 O_5 to 69.3% in the range of 2.0–4.3 V.The initial discharge capacity of NCA@Cr_2 O_5 composite material is 211.4 m A·h·g~(-1), its first coulombic efficiency is 94.2%, and the charging capacity remains approximately constant when mixed with 15%(mass)Cr_2 O_5. The reason for the improvement of the initial charge–discharge efficiency(ICDE) was explained.Impedance and cyclic voltammetry analysis reveal more detailed reasons of the observed improvements.Compared with NCA cathode material, the NCA@Cr_2 O_5 composite material can provide not only additional stable sites and channels for Li+insertion/extraction to make up for the loss of active Li+sites and prevent the accumulation of Li+in the circulation process, but also protect the NCA electrode from the corrosion of the electrolyte decomposition by the Cr_2 O_5 nanoparticles adhering to NCA interface.     

FeS2@TiO2 nanorods as high-performance anode for sodium ion battery

Sodium-ion battery (SIB) is an ideal device that could replace lithium-ion battery (LIB) in grid-scale energy storage system for power because of the low cost and rich reserve of raw material. The key challenge lies in developing electrode materials enabling reversible Na⁺ insertion/desertion and fast reaction kinetics. Herein, a core-shell structure, FeS₂ nanoparticles encapsulated in biphase TiO₂ shell (FeS₂@TiO₂), is developed towards the improvement of sodium storage. The diphase TiO₂ coating supplies abundant anatase/rutile interface and oxygen vacancies which will enhance the charge transfer, and avoid severe volume variation of FeS₂ caused by the Na⁺ insertion. The FeS₂ core will deliver high theoretical capacity through its conversion reaction mechanism. Consequently, the FeS₂@TiO₂ nanorods display notable performance as anode for SIBs including long-term cycling performance (637.8 mA·h·g⁻¹ at 0.2 A·g⁻¹ after 300 cycles, 374.9 mA·h·g⁻¹ at 5.0 A·g⁻¹ after 600 cycles) and outstanding rate capability (222.2 mA·h·g⁻¹ at 10 A·g⁻¹). Furthermore, the synthesized FeS₂@TiO₂ demonstrates significant pseudocapacitive behavior which accounts for 90.7% of the Na⁺ storage, and efficiently boosts the rate capability. This work provides a new pathway to fabricate anode material with an optimized structure and crystal phase for SIBs.     

One-step synthesis of recoverable CuCo2S4 anode material for high-performance Li-ion batteries

A facile one-step hydrothermal method has been adopted to directly synthesize the CuCo₂S₄ material on the surface of Ni foam. Due to the relatively large specific surface area and wide pore size distribution, the CuCo₂S₄ material not only effectively increases the reactive area, but also accommodates more side reaction products to avoid the difficulty of mass transfer. When evaluated as anode for Li-ion batteries, the CuCo₂S₄ material exhibits excellent electrochemical performance including high discharge capacity, outstanding cyclic stability and good rate performance. At the current density of 200 mA·g⁻¹, the CuCo₂S₄ material shows an extremely high initial discharge capacity of 2510 mAh·g⁻¹, and the cycle numbers of the material even reach 83 times when the discharge capacity is reduced to 500 mAh·g⁻¹. Furthermore, the discharge capacity can reach 269 mAh·g⁻¹ at a current of 2000 mA·g⁻¹. More importantly, when the current density comes back to 200 mA·g⁻¹, the discharge capacity could be recovered to 1436 mAh·g⁻¹, suggesting an excellent capacity recovery characteristics.