Composite Anode Material Research Articles

In-situ preparation of LixSn-Li2O–LiF/reduced graphene oxide composite anode material with large capacity and high initial Coulombic efficiency

Anode materials with large capacity have a growing application due to the booming electric vehicle and energy storage market. However, the low initial Coulombic efficiency (ICE) and poor cycle stability hinder their commercial development. Herein, we investigate the effective and convenient method of preparing LixSn-Li2O–LiF/reduced graphene oxide (LixSn-Li2O–LiF/RGO, Li-GFTO) composite anode material with large capacity and high ICE. Firstly, the highly-dispersed fluorine-doped tin oxide and reduced graphene oxide (F–SnO2/RGO, GFTO) composite is in-situ synthesized by one-pot reflux method. The fluorine-doped SnO2 nanocrystals are uniformly anchored on graphene sheets. Secondly, the F–SnO2/RGO was lithiated by reacting with the lithium dissolved in the solution of biphenyl and 1,2-dimethoxyethane to get LixSn-Li2O–LiF/RGO composite. The Li2O and LiF will be formed and prevent the diffusion and coarsening of Sn and LixSn during cycling. Used as the anode material, the ICE of the LixSn-Li2O–LiF/RGO composite is as high as 97%. The composite anode material also shows high cycling stability. The residual capacity is as high as 992 mAhg−1 at 0.1 Ag-1 after 100 cycles, and the charge capacity retention is 99%. Most of all, the mild preparation condition promotes the mass production and practical application of tin-lithium alloy based composite anode materials.

Porous Si@C Composite Anode Material Prepared Using Dopamine as a Carbon Source for High-Performance Lithium- Ion Batteries

Porous Si@C Composite Anode Material Prepared Using Dopamine as a Carbon Source for High-Performance Lithium- Ion Batteries

High-Performance Multi-Layers Tubular Nanostructure Anode Materials for Lithium-Ion Batteries

In order to reduce the negative volume effect of Silicon (Si) and Silica (SiO[Formula: see text] as anode materials, CNTs@SiO2/Si@C is prepared by sol–gel method and magnesiothermic reduction process. SEM and TEM results show that the surface of Carbon nanotubes (CNTs) is uniformly coated with active materials including SiO2 and Si. Active materials (SiO2/Si) closely contact with the conductive network constructed by CNTs, which greatly improves the conductivity of the composite anode material. Moreover, the large specific surface area of the tubular structure provides more Li[Formula: see text] diffusion channel. The cushion space of the hollow tube structure effectively alleviates the volume effect of SiO2/Si and enables the anode material excellent electrochemical performance in the cycling test. The initial discharge capacity of CNTs@SiO2/Si@C is 1064[Formula: see text]mAh/g at current density of 200 mA/g. The specific discharge capacity of CNTs@SiO2/Si@C is higher than 960 mAh/g after 100 cycles, and the coulomb efficiency maintains over 98% in the range from 30th to 100th cycle.

Porous N-doped carbon sheets wrapped MnO in 3D carbon networks as high-performance anode for Li-ion batteries

We develop a facile and low-cost method to construct porous N-doped carbon sheets wrapped MnO cubes with average size of 150 nm in 3D carbon networks by one-step pyrolysis strategy. The unique and novel nanostructure not only provides holes to promote fast ion transport and conductive framework to enhance the charge transfer, but also effectively supplies an elastic buffer space to accommodate volume expansion during cycling. Furthermore, kinetic analysis and other tests reveal that capacitive-controlled Li storage is a vital way and further oxidation of Mn2+ to a higher state with cycling contributes a lot of capacity. As a result, the composite electrode shows high specific capacity of 917 mAh g−1 at 0.2 A g−1 after 190 cycles, outstanding rate capability of 328 mAh g−1 at 5 A g−1, and long cycling stability (655 mAh g−1 at 1 A g−1 after 550 cycles, capacity retention of 105%). Furthermore, the composite electrode and LiFePO4 are used as anode and cathode to assemble full cell which also exhibits excellent rate capability and cycling stability, indicating great application potential. The simple and low-cost strategy of synthetizing the unique nanocomposite structure can also be applied to other composite anode materials for lithium-ion batteries.

Top-Down Synthesis of Silicon/Carbon Composite Anode Materials for Lithium-Ion Batteries: Mechanical Milling and Etching.

Lithium-ion batteries (LIBs) providing high energy and power densities as well as long cycle life are in high demand for various applications. Benefitting from its high theoretical specific charge capacity of ≈4200 mAh g-1 and natural abundance, Si is nowadays considered as one of the most promising anode candidates for high-energy-density LIBs. However, its huge volume change during cycling prevents its widespread commercialization. Si/C-based electrodes, fabricated through top-down mechanical-milling technique and etching, could be particularly promising since they can adequately accommodate the Si volume expansion, buffer the mechanical stress, and ameliorate the interface/surface stability. In this Review, the current progresses in the top-down synthesis of Si/C anode materials for LIBs from inexpensive Si sources via the combination of low-cost, simple, scalable, and efficient ball-milling and etching processes are summarized. Various Si precursors as well as etching routes are highlighted in this Review. This review would be a guide for fabricating high-performance Si-based anodes.

Structural, mechanical and electrical properties of NiO - GDC20 composite anodes for low or intermediate temperature solid oxide fuel cells

Nano Composites NiO and 20 mol% gadolinium doped ceria (GDC20) were synthesized as X (NiO) +1-X (Ce0.8 Gd0.2 O2-δ) where (X = 40& 45 wt. %) for intermediate or low temperature operating solid oxide fuel cells (SOFC). For composite anode materials, NiO and GDC20 nano powders were mechanically mixed and calcined from 600 °C to 750 °C. Samples were pelletized and sintered at 1300°C. Systematic study of structure, purity, phase and structural parameters of anode samples were carried out by XRD and SEM. Mechanical strength of anode composites were estimated by Vickers micro-hardness and observed that microhardness of composites are varying from 9.37 GPa to 11.25GPa. Electrical properties D.C conductivity and A.C conductivity of anode composites were computed using four probe method and impedance analyser respectively. The A.C conductivity and their activation energies of the anode samples (compositions X = 40 & 45 wt. %) were computed from RT to 500°C with the impedance spectrosopy data and the conductivities are found 2.95 x 10−3 S/cm and 7.53 x 10−2 S/cm respectively at 500°C (frequency 1.33 MHz). The activation energies of A.C conductivity have observed that decrease with increase in frequencies.

Synthesis of double core-shell carbon/silicon/graphite composite anode materials for lithium-ion batteries

In this study, we propose a double core-shell carbon/silicon/graphite composite anode for Li ion batteries. We choose two different sorts of carbon, including crystalline mesocarbon microbeads (MCMB) and amorphous pitch to construct a highly stable carbon matrix to stabilize structural stability of Si during charge and discharge processes. MCMB serves as the core material, by adding nano-sized silicon on the surface to increase reversible capacity and then make a pitch coating as the shell via a high-temperature carbonization process. We try to optimize the content of silicon by 10%, 20%, 30% and 40% onto MCMB. With the increase of silicon content, the reversible capacity is significantly improved. When the silicon content increases to 40%, the reversible capacity begins to decline rapidly. The optimal silicon content in Si/MCMB composite is 30%. The composition-optimized Si/C composite deliver a reversible capacity of 847 mAh/g with a columbic efficiency of 87.8%. After 500 cycles, the capacity still remains at 650 mAh/g with >79% capacity retention. The results indicate that we demonstrate a silicon/carbon composite with high reversible capacity and good cycle stability.

Rational Design of Core‐Shell Structured C@SnO2@CNTs Composite with Enhanced Lithium Storage Performance

AbstractSnO2 is considered to be a potential anode material in lithium‐ion batteries (LIBs) owing to its high specific capacity of 1494 mAh g−1. Herein, we reported the unique core‐shell structured C@SnO2@CNTs composite with controllable outer carbon thickness, which was synthesized by a simple hydrothermal method and subsequent annealing process. Results show that the C@SnO2@CNTs with outer carbon layer around 1.8 nm displays high reversible capacity and long‐term cycling performance. It maintains a capacity of 850 mAh g−1 should be at current density of 200 mA g−1 up to 100 cycles. Further analysis found that the C@SnO2@CNTs composite exhibits excellent structural stability even after 100 cycles, which contributes to provide a highway for charge transmission. These results give rise to superior electrochemical performance of C@SnO2@CNTs composite and provide new insight for design metal oxide composite anode materials in LIBs field.

Preparation and electrochemical properties of high capacity silicon-based composites for lithium-ion batteries

Magnesium (Mg) and silicon monoxide (SiO) were subjected to an in situ oxidation-reduction reaction by high-energy ball milling (HEBM) to form a composite of silicon (Si) and magnesia (MgO) followed by mixing with graphite (G). The Si/MgO/G (denoted as SMG) composite powder was then coated with carbon via high-temperature carbonization of pitch to fabricate a carbon-coated composite structure of SMG@C as anode composite material for lithium-ion batteries. X-ray diffraction analysis (XRD), scanning electron microscopy (SEM), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS) were carried out to study the phase, morphology, structure, and the electrochemical properties of the silicon-based anode composite materials. It has been found that the prepared SMG@C anode composite material showed a core-shell structure composed of Si, MgO, graphite, and amorphous carbon. Electrochemical testing indicated that SMG@C exhibited good electrochemical performance, including not only a low impedance but also good cycle stability and rate performance. At a current density of 100 mA/g, SMG@C maintained a capacity of 1124 mAh/g at 75 cycles, and the cycle performance remained relatively stable. After cycling at different current density, the capacity of SMG@C was restored to its initial state when it was tested at 100 mA/g current density. The SMG@C anode material prepared by the simple process of HEBM plus high temperature calcination of a carbon coating is promising to replace conventional graphite anode material for high energy density lithium ion batteries.

High-rate lithium storage and kinetic investigations of a cubic Mn2SnO4@Carbon nanotube composite anode

To solve battery performance problems, the development of novel materials with excellent electrochemical properties is urgently needed. In this study, a facile hydrothermal method was used to synthesize tri-component Mn2SnO4 anchored on carbon nanotubes (Mn2SnO4@MWCNTs) composite materials with cubic particles and high porosity. The structure and composition of the composite materials were analyzed using microscopic techniques. The composite anode material has a high lithium storage capacity of 1120 mAh g−1 (@ 0.05 C) and good stability at high rates of up to 10.0 C. The kinetic properties during the electrochemical reaction were also investigated. The synergistic effects of the composite anode enable faster charge transfer as evidenced by impedance spectroscopy, which shows that the composite electrode has a charge transfer resistance of 56 Ω, whereas that of the bare Mn2SnO4 electrode is 88 Ω. The enhanced electrochemical performance of the Mn2SnO4@MWCNTs anode is attributed to the mesoporous structure and the addition of MWCNTs, which enable faster insertion/extraction of Li+ ions into/from the material.

Fabrication of Attapulgite/Multi-walled Carbon Nanotube Aerogels As Anode Material for Lithium Ion Batteries

Porous silica-based anode materials with high theoretical specific capacity and abundant reserves have attracted popular attention for application in lithium ion batteries (LIBs). However, poor electrochemical conductivity and mechanical performance hinder the development of silica-based anode materials. In this work, attapulgite/multi-walled carbon nanotube (AT/CNT) composite anode materials were prepared. The structural features of AT/CNT composite aerogels were characterized by field emission scanning electron microscopy (FESEM), energy dispersive spectroscopy (EDS), x-ray diffraction (XRD) and Brunauer–Emmett–Teller (BET). because of the excellent conductivity and porous pathways of AT/CNT anode material, the reversible specific capacity of AT/CNTs containing 0.5 wt.% CNTs (AT-0.5) with a mass loading of 0.67 mg cm−2 was 303.6 mAh g−1 at 0.1 A g−1 after 50 cycles, and a coulombic efficiency of AT-0.5 was 99.1%. The green LEDs were lit by the assembled battery of AT-0.5. The electrochemical results demonstrated that AT/CNT anode materials possessed practical application values for energy storage. Moreover, the preparation method of AT/CNT anode materials is efficient and environmentally friendly.

Decoration of hollow nitrogen-doped carbon nanofibers with tapered rod-shaped NiCo2S4 as a 3D structural high-rate and long-lifespan self-supported anode material for potassium-ion batteries

Although potassium ion batteries (KIBs) have been invested in development as an emerging low-cost, high-content energy storage system at present. However, the large ionic radius of K+-ion lead to poor rate performance and low cycle life. Therefore, it is extremely necessary to develop a new type of potassium storage material. Here, we report a novel three-dimensional (3D) structural self-supported anode composite material for KIBs, which consists of tapered rod-shaped nanomaterial NiCo2S4 and nitrogen-doped hollow carbon nanofibers (NiCo2S4@N-HCNFs). Then, the composite material was obtained by high temperature carbonization and hydrothermal reaction process. The prepared electrode materials were used to assemble K half-cells for electrochemical performance measurement, achieved the capacity of 263.7 mAh g−1 after 200 cycles at a current density of 100 mA g−1 and an outstanding stability of retaining 134.3 mAh g−1 at 3200 mA g−1 after 600 cycles. It has superior performance and convenient synthesis process over other reported metal sulfides self-supported anode materials for KIBs so far. The novel structure not only shorten the ion transmission distance, but also increase the contact area with the electrolyte. It can improve electrochemical performance effectively.

A novel 3D porous pseudographite/Si/Ni composite anode material fabricated by a facile method.

A novel 3D porous pseudographite/Si/Ni (PG/Si/Ni) composite was prepared by a facile low-temperature calcination method using saturable starch and NiCl2·6H2O as precursors. The pseudographite matrix of PG/Si/Ni was obtained from the reaction between starch and NiCl2·6H2O during the calcination process. Compared to the C/Si electrode, the PG/Si/Ni electrode delivers a high reversible specific capacity of 659.66 mA h g-1 at a current density of 1 A g-1 even after 2000 cycles. In addition, the PG/Si/Ni electrode shows superior rate performance and still maintains a high specific capacity of 1324.01 mA h g-1 when the cycle current density returns to 0.1 A g-1. The porous pseudographite structure is able to improve Li+ diffusion efficiency, reduce pulverization and lead to the formation of stable SEI layers during the cycling process. Therefore, these results suggest that the 3D porous pseudographite/Si/Ni composite is a promising novel anode material. Besides, the low-temperature synthesis method of the pseudographite matrix can be applied for further modification of carbon-based Si anode materials.

A novel strategy for synthesis of Si@N doped carbon anode material with enhanced electrochemical performance for lithium-ion batteries

To relieve the volume expansion of Si, a new strategy for synthesis of Si@N doped Carbon (Si@N-C) anode composite material with the core-shell structure is designed via heat treatment process of silicon@polyaniline (Si@PANI) as the precursor, whose synthesis approach was on the basis of mixed solution of ethanol and water as the solvent. Benefiting from the structural stability of the core-shell structure, the cell assembled with the Si@N-C anode material shows outstanding electrochemical performance, its capacity decreases little with the current density increasing and a high discharge capacity of 1053.42 mAh g−1 can still be obtained when the current density sets back to 200 mA g−1.

In Situ Mechanistic Elucidation of Superior Si‐C‐Graphite Li‐Ion Battery Anode Formation with Thermal Safety Aspects

AbstractA composite anode material synthesized using silicon nanoparticles, micrometer sized graphite particles, and starch‐derived amorphous carbon (GCSi) offers scalability and enhanced electrochemical performance when compared to existing graphite anodes. Mechanistic elucidation of the formation steps of tailored GCSi composite are achieved with environmental transmission electron microscopy (ETEM) and thermal safety aspects of the composite anode are studied for the first time using specially designed multimode calorimetry for coin cell studies. Electrochemical analysis of the composite anode demonstrates a high initial discharge capacity (1126 mAh g−1) and yields a high coulombic efficiency of 83% in the first charge cycle. Applying a current density of 500 mA g−1, the anode composite retains 448 mAh g−1 specific capacity after 100 cycles. Cycling stability is a result of improved interfacial binding made possible by the interconnected architecture of wheat derived amorphous carbon, enhancing the electrochemical kinetics and decreasing the inherent issues associated with volume expansion and pulverization of pristine Si electrodes. Comparing the energy released during thermal runaway, per specific capacity for the full‐cell, the GCSi composite releases less heat than the conventional graphitic anode, suggesting a synergistic effect of each ingredient of the GCSi composite, providing a safer and higher performing anode.

Initiation Process of Vacuum Breakdown Between Cu and CuCr Electrodes

During the breakdown process in a vacuum, plasma flares initiated on cathode and anode surfaces expand and collide. The plasma flare behavior is quite important for the optimization of the spark conditioning of vacuum interrupters. Here, copper–chromium alloys are widely used as an electrode material in the large-capacity vacuum circuit breakers. In this article, high-speed spectroscopy is conducted on the plasma flares generated between a CuCr (Cr-35wt%) anode and a Cu cathode in order to elucidate the plasma temperature, particle composition, and electron density. The experimental results show that the anode flare has 1024–1025m−3 electron, and its temperature is approximately 13 000 K. The composition ratio of vapor atoms consisting the anode flare is Cu:Cr = 6:4–7:3, which is almost the same with that of anode material composition.

Adding Metal Carbides to Suppress the Crystalline Li15Si4 Formation: A Route toward Cycling Durable Si-Based Anodes for Lithium-Ion Batteries

In addition to large volume change and sluggish kinetics, the capacity decay of silicon anodes is also related to the formation of a crystalline Li15Si4 phase during cycling. Herein, we have demonstrated that refining cheap coarse-grained Si by ball milling with metal carbides (Mo2C, Cr2C3, etc.) can reduce the Si crystallite size significantly and can thus suppress the formation of the crystalline Li15Si4 during cycling, which increases the life of Si-based anode materials significantly. Si-Cr3C2@few-layer graphene (SC@G) composite anode materials were designed and prepared by plasma milling (P-milling) to achieve a considerable capacity of 881.8 mA h g-1 after 300 cycles at 1 A g-1. A study of the microstructure of the SC@G indicated that the refined amorphous-nanocrystal Si grains were distributed uniformly around multiscale Cr3C2 particles, which were covered by few-layer graphenes. The rigid Cr3C2 skeleton, which acts as a good conductive material, can increase the conductivity of the SC@G composite, avoid the agglomeration of refined Si, and regenerate Si nanosized grains during lithiation and delithiation. These results showed that the SC@G anode material exhibited an excellent overall performance based on its high capacity and long cycle stability, as well as excellent lithium-ion diffusion kinetics for lithium storage.

Improvement of Hard Carbon Electrode Performance by Manipulating SEI Formation at High Charging Rates

There is a growing demand for high-rate rechargeable batteries for powering electric vehicles and portable electronics. Here, we demonstrate a strategy for improving electrode performance by controlling the formation of solid electrolyte interphase (SEI). A composite electrode consisting of hard carbon (HC) and carbon nanotubes (CNTs) was used to study the formation of the SEI at different charging rates in an electrolyte consisting of 1 M NaClO4 in a mixed solvent with ethylene carbonate (EC) and propylene carbonate (PC), as well as fluoroethylene carbonate (FEC) additive. The half-cell method was used to form the SEI at different charging rates (e.g., 1, 10, and 100 A/g). Symmetric capacitor cells were employed to study ion transport properties through the SEI. It was found that the SEI is a primary factor responsible for limiting the capacity of the composite anode material in conventional ester-based electrolytes. The electrode with the SEI formed at 100 A/g exhibited the lowest impedance and delivered nearly twice the capacity of the electrode with the SEI formed at 1 A/g. This significant difference is due to a thin SEI formed at the fast charging rate, as has been observed with ether-based electrolytes. An identical decay rate (0.11 mA h/g per cycle) was observed on the electrodes with SEIs formed at different charging rates in an ester electrolyte. No chemical difference among the three SEI layers was found. However, morphological differences of the SEI layers were observed. This difference is believed to account for the different electrochemical behaviors of the electrodes. This work shows that high charging rates can result in the formation of an optimal SEI layer, contradicting the widely accepted practice of using low charging rates during the SEI formation in alkali-ion batteries.

Effect of different oxidants on properties of tin-graphite composite anode material for lithium-ion battery

In this paper, oxidation doping modification of tin-graphite composite anode material, discussing the effect of doping different oxidants on the properties of composites. The structure and morphology were measured by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The electrochemical properties of the samples were investigated by electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), and galvanostatic charge and discharge tests. The results showed that the oxidation effect of H2SO4 was better than HNO3 and H2O2. When the tin-graphite composite was oxidized by H2SO4, the material had better electrochemical properties, of which initial specific discharge capacity reached 859 mAh·g−1 at the rate of 0.1C, increasing by 113 and 76 mAh·g−1 compared with the HNO3 and H2O2. The initial discharge specific capacities at rates of 0.2, 0.5, and 1C were 809, 761, and 627 mAh·g−1.

Novel method for preparation of metal-sulfide@reduced-graphene-oxide with high energy storage performance

Transition-metal sulfide with high theoretical capacity is a promising anode material. However, the poor conductivity and pulverization of the transition-metal sulfide caused by huge volume changes lead to a fast decay in specific capacity. In this study, we prepared a three-dimensional sandwich-structured anode material consisting of metal sulfides and reduced graphene oxide (rGO), which can address the above problems. The anode material is composed of Ni7S6/MnS2 micro/nanosheets uniformly attached on the rGO synthesized by an in-situ sulfuration of a NiMn2O3(OH)4@rGO precursor. The Ni7S6/MnS2@rGO composite exhibited a high electrochemical performance, which is mainly ascribed to the three-dimensional sandwich-structures, because it can well relieve the volume change and promote electron mobility and ion diffusion in the discharge/charge process. Furthermore, this method can be used to prepare other sulfides such as NiS2@rGO and Ni7S6/CoS2@rGO. The proposed universal preparation method and excellent electrochemical performance of Ni7S6/MnS2@rGO make the composite attractive anode material.