Composite Anode Material Research Articles

High‐performance electrodes for Li‐ion cell: Heteroatom‐doped porous carbon/ CoS structure and investigation of their structural and electrochemical properties

As an essential class of anode materials, the synthesis and characterization of CoS@ZIF-12-C composite anode materials are reported. The two-step synthesis of CoS nanoparticles embedded in N-doped porous carbon by using a metal-organic framework (MOF) as the template. After structural characterization of CoS@ZIF-12-C composite materials, the main phase was found as CoS with symmetry of P63mmc. Benefiting from the CoS embedded in porous carbon structure, the half Li-ion battery cell tests of CoS@ZIF-12-C composite materials were performed by a 2-electrode method using CR2032 cells, and the capacities of the cells were measured for 200 cycles using 300 mAg−1 and 500 cycles using 1000 mAg−1. The first discharge capacities of the cells for 1000 mAg−1 were found as 458, 1178, and 815 mAhg−1 for CoS@ZIF-12-C-T, T = 700, 800, and 900°C, respectively. An unexpected capacity increase was observed for the CoS@ZIF-12-C-700 and CoS@ZIF-12-C-900 half cells during the cycling. Ex-situ x-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), and cyclic voltammetry (CV) analysis were performed after cycling of the cells for explanations of the capacity increase. Ex-situ XRD analysis of these cells showed phase transitions from crystalline to amorphous type structure, and ex-situ FTIR proves the preservation of the CoS phase during the cycling. A redox reaction mechanism was suggested to explain the cells' battery performance by ex-situ XRD analysis.

Sn nanoparticles embedded into porous hydrogel-derived pyrolytic carbon as composite anode materials for lithium-ion batteries

Sn nanoparticles embedded into porous hydrogel-derived pyrolytic carbon as composite anode materials for lithium-ion batteries

(Digital Presentation) New Trends in the Formation of Composites with Desired Functional Properties

The main requirements for anode materials can be divided into two groups: i) overall operating (satisfactory electrical conductivity, availability and reasonable cost, long service life, etc.); ii) specific, due to particular target process (high electrocatalytic activity and selectivity) [1]. The lack of universal anode material requires the creation of new approaches to managing the functional properties of the catalyst. In our opinion, the optimal strategy is to choose a base material that meets the general operational requirements, followed by the creation of an active layer on its basis in accordance with the requirements of particular target processes.The regularities of formation of composites of the TiOx-Pt and TiOx-Pt-Pd systems and their physicochemical properties were studied.Composites were obtained in two stages. First, a thin non-continuous layer of Pt or successive layers of Pt-Pd was applied to the substrate by electrodeposition. Nitrite electrolyte for platinating and phosphate palladation were used. The amount of Pt and Pd on the surface ranged from 0.1 to 2.0 mg cm-2. Then the resulting material was heat treated in an air atmosphere. The surface layers of the composites were formed due to the oxidation of the substrate and the encapsulation of platinum and palladium particles into titanium oxides during this stage. The chemical composition of the bulk and surface of the electrocatalytic coatings obtained was determined by XPS, SEM and EDAX.XPS showed that Pt exists in the metallic state, while Ti is in the form of both metal and intermetallic TixPty, with low Pt content, and in oxide form in Ti(IV) compounds on the surface of non-heat treated electrode As one can see, the coating is not uniform, and the platinum content is significantly reduced from the surface to the substrate (from 92 to 67 at.%), that indicates the local nature of the coating and confirmed by SEM data. As thermal treatment contributes to a more uniform distribution of Pt on the surface, as well as its diffusion in combination with oxygen in the coating bulk, it leads to the formation of a composite of titanium-platinum oxides.The semiconductor properties of such anodes are due to the presence of TiO2, which is an n-type semiconductor. As the temperature increases, the potentials of the flat zones and the carrier concentrations increase, which may be related to the interaction of platinum (electron donor) with TiO2. The use of titanium suboxides as a substrate and increasing the processing temperature also leads to an increase in the potential of flat zones. However, this reduces the number of carriers due to the increase in the degree of stoichiometry of titanium suboxides due to oxygen uptake. The electrodes obtained at 583 K do not correspond to the general dependence. It is likely that the new Ti-O phase formed under such conditions makes an individual contribution to the semiconductor properties of such materials.Palladation of platinum titanium does not lead to a significant change in surface morphology. Platinum, according to EDAX, is fairly evenly distributed on the surface of titanium, which is not observed for palladium. Unlike platinum, the maximum amount of palladium is observed in the protruding parts of the surface, and the minimum - in the hollows, due to the uneven distribution of current on the surface of Ti/Pt during the electrodeposition of palladium. The most noticeable change in morphology occurs at a surface Pd content of 1.0 mg cm-2. The oxygen concentration increases on the surface during heat treatment of Ti/Pt-Pd, there is oxidation of Pd, the surface becomes blue. The distribution of oxygen on the surface coincides with palladium, which indicates the formation of an oxide layer. The XRD method detected the PdO phase on the surface of heat-treated samples with a surface palladium content of 0.2 to 1.0 mg cm-2. At 2θ = 33.8°, the PdO-specific reflex is manifested, the area of which increases with increasing of surface palladium content.Thus, the use of the combined electrochemical-pyrolytic method of obtaining composite anode materials allows to create materials that differ significantly in their structural parameters, composition and physicochemical properties. The main factors influencing the properties of such materials are the nature of the substrate, the amount and nature of platinum and palladium in the surface layer, the temperature and duration of heat treatment in the air. Developed anode materials are characterized by long service life. References Walsh, F.C. Modern developments in electrodes for electrochemical technology and the role of surface finishing / F.C. Walsh // Trans. Inst. Met. Finish. – 2019. – Vol. 97(1). – P. 28-42

Investigation of Silicon-Based Anodes for Li-Ion Batteries Using X-Rays and Neutron 3D/4D Imaging Techniques

Silicon-based anode materials are one of the most promising approaches to further increase the energy density of lithium-ion batteries. However, current materials are limited by poor cycling stability and rapid capacity fading, mainly caused by the massive volume expansion of Si during lithiation and subsequent strain on the material composite. [1] Furthermore, this electrode swelling also results in continuous solid electrolyte interface (SEI) growth, which hinders the migration of Lithium and leads to permanent capacity loss. [2] [3]To optimize these materials, analytical techniques able to probe the local 3D morphology and Li content are necessary. By applying methods such as neutron computed tomography (NCT), X-Ray computed tomography (XCT) and synchrotron scattering micro-tomography (SMT) structural ageing and changes in the distribution of lithium in the various components can be characterized and quantified for different charging states and recharge cycle numbers.This study investigates an anode material based on a dual phase alloy system of amorphous Silicon (a-Si) with crystalline iron silicide (c-FeSi2) and graphite. [4] [5] Li-ion battery coin cells containing this silicon-graphite composite anode material were industrially produced and aged by performing 1, 300, and 700 charge-discharge cycles, corresponding to remaining capacities of 100, 70 and 50 %, respectively. NCT and XCT scans were acquired at the NeXT instrument of the ILL in Grenoble (France) [6], and SMT measurements performed at ID31 of the neighboring ESRF. These datasets were reconstructed and evaluated using specially developed data processing pipelines. By performing multi-modal registration, the NCT and XCT scans were aligned and segmented to combine the complementary datasets and create a 4D model of the Li-ion battery coin cells.Figure 1 shows a sample of the combined NCT (cyan) and XCT datasets (red). Cropped horizontal slices of Li-Ion battery coin cells are depicted side by side with the main components labelled. Comparing one of the highly cycled cells with 50% remaining capacity (top) with the reference cell without electrolyte (bottom), trapped Lithium can be observed in the anode layers, visible as cyan colored blotchy areas in the otherwise dark component. The pixel size is approximately 5 µm.The change of lithium distribution in the components between different cycle numbers and charge states in the attenuation-based tomography techniques of NCT / XCT is quantified by modelling expected attenuation parameters to the observed values. The diffraction-based tomography method of SMT was modeled using expected lattice parameters. From this information, trapped Lithium can be identified and changes in the distribution are analyzed to point out possible degradation and failure mechanisms.We acknowledge financial support from the European Union’s Horizon 2020 research and Innovation program No. 875514 (ECO2LIB) as well as No. 847439 (InnovaXN) under the Marie Skłodowska-Curie grant agreement.[1] S. Tardif et al, https://doi.org/10.1021/acsnano.7b05796 [2] T. Vorauer et al, https://doi.org/10.1038/s42004-020-00386-x [3] P. Kumar et al, https://doi.org/10.1002/smll.201906812 [4] C. Berhaut et al, https://doi.org/10.1021/acsnano.9b05055 [5] C. Berhaut et al, https://doi.org/10.1016/j.ensm.2020.04.008 [6] A. Tengattini et al, https://doi.org/10.1016/j.nima.2020.163939 Figure 1

Aluminothermic reduction synthesis of Si/C composite nanosheets from waste vermiculite as high-performance anode materials for lithium-ion batteries

The utilization of mining wastes for value-added energy applications is vitally important in a clean and sustainable society. In this work, we report the preparation of nanostructured Si/C composites from a vermiculite waste via an aluminothermic reduction reaction. During the preparation process, chitosan is employed as the carbon source which can intercalate into the interspacing between the layers of vermiculate through cation exchange, which is the key to form a layered Si/C composite. Such obtained Si/C composites exhibit layered structure, large specific surface area, abundant nanopores, and minor SiOx and N components, thus having the merits of buffering volume expansion, good structure stability and high electrical conductivity. Finally, the Si/C composites are applied as anode for lithium-ion batteries and shows excellent specific capacity of ~948 mAh g−1 after 350 cycles at 1.0 A g−1 with a capacity retention of 85%, proving the applicability of such Si/C composite as an alternative to commercial graphite anode. This work not only provides a mild route for designing nanostructured Si/C composite anode materials, but also paves an innovative way for the reutilization of waste tailings for high value-added materials applications.

Conjugated Polymer/Graphene composite as conductive Agent-Free electrode materials towards High-Performance lithium ion storage

Polymer materials containing C6 rings and CO become promising electrode materials for high-performance lithium ion batteries (LIBs). However, the poor electronic conductivity severely restricts its further application. Herein, we design and construct a pyromellitic dianhydride anhydride anthraquinone/reduced graphene oxides (PMAQ/rGO-40) composite as an anode material for LIBs. The PMAQ is uniformly wrapped by conductive rGO nanosheets. The PMAQ/rGO-40 electrode without additional conductive agents displays a discharge capacity of 253 mAh g−1 over 3000 cycles under 2A g−1, which is higher than that of the PMAQ electrode with conductive agents. Meanwhile, a capacity of 196 mAh g−1 is achieved under 5A g−1. The enhanced cycling performance and rate ability are attributed to the rGO conductive network, which promotes electronic transport capability. In addition, the lithium ion storage mechanism and kinetics in the PMAQ/rGO-40 are investigated. The excellent electrochemical performance shows the potential application of the PMAQ/rGO composite anode material for high performance LIBs.

Strategies for Controlling or Releasing the Influence Due to the Volume Expansion of Silicon inside Si-C Composite Anode for High-Performance Lithium-Ion Batteries.

Currently, silicon is considered among the foremost promising anode materials, due to its high capacity, abundant reserves, environmental friendliness, and low working potential. However, the huge volume changes in silicon anode materials can pulverize the material particles and result in the shedding of active materials and the continual rupturing of the solid electrolyte interface film, leading to a short cycle life and rapid capacity decay. Therefore, the practical application of silicon anode materials is hindered. However, carbon recombination may remedy this defect. In silicon/carbon composite anode materials, silicon provides ultra-high capacity, and carbon is used as a buffer, to relieve the volume expansion of silicon; thus, increasing the use of silicon-based anode materials. To ensure the future utilization of silicon as an anode material in lithium-ion batteries, this review considers the dampening effect on the volume expansion of silicon particles by the formation of carbon layers, cavities, and chemical bonds. Silicon-carbon composites are classified herein as coated core-shell structure, hollow core-shell structure, porous structure, and embedded structure. The above structures can adequately accommodate the Si volume expansion, buffer the mechanical stress, and ameliorate the interface/surface stability, with the potential for performance enhancement. Finally, a perspective on future studies on Si−C anodes is suggested. In the future, the rational design of high-capacity Si−C anodes for better lithium-ion batteries will narrow the gap between theoretical research and practical applications.

Effect of MgO on electrochemical properties of silicon-based anode composite material

A silicon (Si)/magnesia (MgO)/graphite composite (denoted as SMG@C) was synthesized by high-energy ball milling (HEBM) via the reduction of silica (SiO) by magnesium (Mg) and subsequent addition of graphite, followed by pitch pyrolysis for carbon coating. The particles of MgO in the SMG@C were removed by hydrogen chloride (HCl) leaching to form the Si/graphite composite (denoted as SG@C). The microstructural characteristics of the two composite materials were analyzed by X-ray diffraction and transmission electron microscopy and their electrochemical properties were evaluated by cyclic voltammetry, electrochemical impedance spectroscopy, and capacity cycling tests. Results indicated that the a homogeneous mixture of nanoscale Si and MgO was fabricated by HEBM, and some of the Si and MgO formed a specific crystallographically coherent interface which was determined as Si(220)//MgO(200). The values of Warburg coefficient for SMG@C and SG@C were determined to be 1.84 Ω/S1/2 and 203.42 Ω/S1/2, respectively. When the SMG@C anode composite material was cycled for 440 cycles at a current density of 200 mA/g, its reversible capacity retention rate was 87.8%, showing excellent long-cycle performance compared to the SG@C. The presence of MgO in the anode composite material greatly improved the electrochemical properties.

Disproportionated SiOx/C composite anode materials for lithium-ion batteries

A facile method to synthesize silicon oxide/graphite (SiOx/C) composite anode materials for high-capacity Li-ion batteries (LIBs) is proposed. In order to solve the problems of volume expansion and poor conductivity of silicon-based materials, ball milled disproportionate silicon oxide/graphite (m-d-SiOx/C) composite was successfully synthesized by combining high-temperature annealing and high-energy ball milling. LIBs with SiOx/C as anode material exhibit stable cycling performance at a current density of 100 mA g−1, with an initial reversible capacity of 1213.9 mA h g−1 and coulombic efficiency of 65.7 %. After 100 cycles, their reversible capacity is up to 1292.4 mA h g−1 with a coulombic efficiency of 99.7 %. The excellent electrochemical performance is attributed to the following facts: first, the disproportionated silicon oxide generates silicon and silicon dioxide, in which silicon plays a role in increasing the capacity, and silicon dioxide can irreversibly react with the electrolyte to form a buffer matrix, thereby alleviating the volume effect. Second, the high-energy ball milling not only greatly reduces the size of the commercially available silicon oxide, but also makes the disproportionated silicon oxide evenly adhere to the graphite surface. Graphite can make a partial capacity contribution while providing a conductive matrix for the composite.

Reduced Graphene Oxide (rGO)-Supported and Pyrolytic Carbon (PC)-Coated γ-Fe2 O3 /PC-rGO Composite Anode Material with Enhanced Li Storage Performance.

As a high-capacity anode material for lithium ion batteries, γ-Fe2 O3 is a promising alternative to conventional graphite among multifarious transition metal oxides owing to its high theoretical specific capacity (1007 mAh g-1 ), abundant reserves, good safety and low cost. However, improving the electrical conductivity and overcoming the morphological damage caused by the severe volume expansion during cycling are still the tricky problems to be solved. Herein, a three-dimensional heterostructure composite (γ-Fe2 O3 /PC-rGO60 ) was prepared by a facile solvothermal reaction followed by heat treatment in inert atmosphere. This composite material exhibits a reversible charge specific capacity of 1035 mAh g-1 at the current density of 0.1 A g-1 . After 100 cycles at 0.2 A g-1 , the capacity is increased from 966.2 to 1091.1 mAh g-1 . Even cycled for 200 cycles at 1 A g-1 , the capacity is only decreased from 751.4 to 670.6 mAh g-1 , giving capacity retention of 89.3%. The rGO network supported flexible composite architecture is beneficial for accommodating the volume expansion of the γ-Fe2 O3 active material during the lithiation/delithiation process. Besides, the conductive rGO network and the in-situ formed pyrolytic carbon (PC) can provide a smooth electron transmission path and a favorable lithium ion transport channel.

MoSe2 nanosheets confined in N-doped carbon fibers as robust and capacitive anode of high performance Na-ion capacitors

Enhancing the rate and cycle performance of anode materials is the key in developing high performance Li/Na/K-ion capacitors. Molybdenum selenide (MoSe2) has been well studied as a potential high rate anode material for Na-ion capacitors based on its lamellar structure and large interlayer space. However, the MoSe2 anode usually suffers from inferior cycling stability especially when directly exposing to electrolyte. Herein, a composite anode material with MoSe2 nanosheets confined in N-doped carbon fibers is prepared by electrospinning and post-selenization process, which exhibits highly capacitive Na ion storage behavior and stable cycle performance in Na-metal half cells. When it is coupled with a pomelo peel-derived porous carbon cathode that is pre-mixed with sodium oxalate as the pre-sodiation additive, the assembled Na-ion capacitors display outstanding energy-power performance, including ultrahigh energy densities of 116 and 79 Wh kg−1 achieved at 197 and 8318 W kg−1, respectively, and a quite good stability in a long term cycle test. These results convincingly demonstrate that the composite with MoSe2 nanosheets confined in N-doped carbon fibers can be promising high capacitive and stable anode material for high performance Na-ion capacitors.

Lithium-ion transfer strengthened by graphite tailings and coking coal for high-rate performance anode

Due to the anisotropy of natural graphite crystal structure, the lithium-ion transfer efficiency is poor at large current density for graphite anode. To solve this problem, the composite anode was prepared by co-pyrolysis of coking coal and graphite tailings. Results showed that the liquid plastic mass produced by coking coal pyrolysis not only realized the lamellar reconstruction of graphite tailings, but also strengthened the isotropy of the composite anode material, and the N and S heteroatoms in semi-coke strengthened the transmission of lithium ions. Compared with anode of graphite tailings (SGD), the rate capacity retention of the anode from the co-pyrolysis of oxidized graphite tailings and coking coal (OSGD-GLM) demonstrated superior rate performance (capacity retention increased from 13.98% to 32.00% at current density of 5.0 A g−1compared to 0.1 A g−1), long-term stability and excellent full cell rate performance. More importantly, the lithium-ion diffusion coefficient of OSGD-GLM under charging state was measured by galvanostatic intermittent titration (GITT), which was in the range between 6.26 × 10−10 and 1.71 × 10−8 cm2 s−1, significantly higher than that of commercial graphite anode.

Correction to: Research progress of nano‑silicon‑based materials and silicon‑carbon composite anode materials for lithium‑ion batteries

Correction to: Research progress of nano‑silicon‑based materials and silicon‑carbon composite anode materials for lithium‑ion batteries

Unique CNTs-chained Li4Ti5O12 nanoparticles as excellent high rate anode materials for Li-ion capacitors

Composite anode materials with a unique architecture of carbon nanotubes (CNTs)-chained spinel lithium titanate (Li4Ti5O12, LTO) nanoparticles are prepared for lithium ion capacitors (LICs). The CNTs networks derived from commercial conductive slurry not only bring out a steric hindrance effect to restrict the growth of Li4Ti5O12 particles but greatly enhance the electronic conductivity of the CNTs/LTO composites, both have contributed to the excellent rate capability and cycle stability. The capacity retention at 30 C (1 C = 175 mA g−1) is as high as 89.7% of that at 0.2 C with a CNTs content of 11 wt%. Meanwhile, there is not any capacity degradation after 500 cycles at 5 C. The LIC assembled with activated carbon (AC) cathode and such a CNTs/LTO composite anode displays excellent energy storage properties, including a high energy density of 35 Wh kg−1 at 7434 W kg−1, and a high capacity retention of 87.8% after 2200 cycles at 1 A g−1. These electrochemical performances outperform the reported data achieved on other LTO anode-based LICs. Considering the facile and scalable preparation process proposed herein, the CNTs/LTO composites can be very potential anode materials for hybrid capacitors towards high power-energy outputs.

Research progress of nano-silicon-based materials and silicon-carbon composite anode materials for lithium-ion batteries

Research progress of nano-silicon-based materials and silicon-carbon composite anode materials for lithium-ion batteries

Constructing highly stable lithium storage materials by improving the bond strength of MoS2 to graphene via chitosan

MoS2 is considered a promising substitute anode for lithium-ion batteries (LIBs) due to its two-dimensional layered structure and large theoretical specific capacity. However, the low conductivity and poor structural stability of MoS2 limit its practical applications. Here, a simple self-assembly strategy is adopted to successfully synthesize MoS2/C@G with a 3D porous hybrid nanosheet structure. By utilizing the chitosan can effectively bonding the layered MoS2 with N-doped graphene to construct a layered sandwich-like structure, which ensures the uniform and non-agglomeration distribution of the synthesized few-layer MoS2 nanosheets between graphene sheets. In addition, the strong bond between MoS2 and graphene makes these two components tightly bonded, which greatly improves the electronic conduction and guarantees structural stability. Based on the above advantages, MoS2/C@G as the electrode for LIBs exhibits high reversible capacity and superior cycling stability, with a capacity of 667.7 mAh g−1 at a high current density of 0.5 A g−1 after ultra-long 1000 cycles, even without significant capacity decay. This method also provides an advanced perspective for the fabrication of high-performance graphene composite anode materials.

A multifunctional polyimide enabled high performance silicon composite anode materials for Li-Ion batteries

Herein, a conjugate carbonyl polyimide (MF-PI) and nano-silicon composite (MF-PI/Si) is designed and synthesized through a simple one-pot method to confront rapid capacity fading and complicated electrode material preparation in silicon-based electrodes for lithium ion battery. This composite can be directly used to prepare electrode without the need of further adding of binding materials. In this composite, MF-PI acts as binder for powder electrode, active reversible lithiation material, buffering media to alleviate volume change of silicon particles, and coating shell to avoid the direct contact between silicon particles and electrolyte. These functions from MF-PI collectively assigned the MF-PI/Si composite anode material a relative high specific capacity and excellent cycling stability. The electrode prepared by this as-synthesized MF-PI/Si shows preferable electrochemical interface and surface area, further enhancing the electrode kinetics and then electrochemical performance. The improved ionic and electronic conductivity compared to other binder materials also contributes the excellent performance.

Anode material for all-solid-state battery based on solid electrolyte CsAg4Br2.5I2.5: Theory and experiment

In this work the optimum composition of anode material for all-solid-state batteries based on silver and solid electrolyte CsAg4I2.5Br2.5 was determined. For this, electronic conductivity of the mixture of the solid electrolyte and carbon black was studied. The percolation behavior of systems was studied. Percolation thresholds were determined for each system theoretically and experimentally. It was shown that the electrochemically accessible silver surface in the anode material has non–monotonic dependence on the silver content. As a consequence, the exchange current in the cell also has a maximum.

Application of a Cross-linked Polyacrylic Acid- Polyethylene Oxide (PAA-PEO) Copolymer as a Binder for Si@C@PDA Composite Anode Materials in Li-ion Batteries

Application of a Cross-linked Polyacrylic Acid- Polyethylene Oxide (PAA-PEO) Copolymer as a Binder for Si@C@PDA Composite Anode Materials in Li-ion Batteries

Carbon-coated Si/N-doped porous carbon nanofibre derived from metal–organic frameworks for Li-ion battery anodes

In order to more effectively alleviate the volume extension and shrinkage of the Si anode during Li intercalation/deintercalation processes, and also to improve the electron and ion transport dynamics, carbon coated Si-porous carbon composite fibres with a sandwich structure were prepared using a sacrificial template (ZIF-8) to construct mesoporous carbon, combined with electrospinning technology and subsequent hydrothermal carbon coating. The carbon fibre skeleton and carbon-coated sandwich structure provide support for the volume extension and shrinkage of Si, avoiding Si from directly contacting with the electrolyte, and forming a stable solid electrolyte interphase film. Furthermore, the polyvinylpyrrolidone spinning solution assists ZIF-8 to obtain a mesoporous structure inside the carbon fibre, which improves the specific surface area and pore volume of the composite material. In this case, the mesoporous structure also helps to alleviate the volume extension and shrinkage of Si during the charging /discharging processes and improves the transmission dynamics of lithium ions and electrons. Benefit from the unique structural features, this anode composite material exhibits enhanced electrochemical properties for Li-ion batteries, with a reversible specific capacity of 1114 mAh g−1 at 1 A g−1, and demonstrates a capacity retention rate of 66% with a specific capacity of 740 mAh g−1 after 400 cycles.