Facile and Scalable Synthesis of Si@void@C Embedded in Interconnected 3D Porous Carbon Architecture for High Performance Lithium-Ion Batteries

Si-based materials possess huge potential as an excellent anode material for Li-ion batteries. However, how to realize scalable synthesis of Si-based anode with a long cycling life and high-performance is still a critical challenge. Here a water-in-oil microemulsion process followed by UV illumination, calcination, and hydrothermal method to produce yolk-shell Si@void@C embedded in interconnected 3D porous carbon network architecture using silicon nanoparticles is reported. As a result, the sample Si@void@C/C-2 electrode has achieved a reversible capacity of 1160 mA h g⁻¹ at 0.2 A g⁻¹ after 300 cycles and a stable long cycling life of 480 mA h g⁻¹ at 1 A g⁻¹ after 1000 cycles. A full battery with the synthesized anode shows a capacity of 128 mA h g⁻¹ at 0.2 A g⁻¹ as well as good cycling stability after 1100th cycles. Such excellent electrochemical performance is ascribed to its unique structure, the yolk-shell void space, highly robust carbon shells and interconnected porous carbon nets that can improve the conductivity of the electrode, buffer the volume expansion, and also suppress Si nanoparticles stress variation. This water-in oil system makes it possible for mass production of environmentally friendly synthesis of core–shell structure.     

Uniform Mesoporous CoCO3 Nanospindles on Graphite Nanosheets for Highly Efficient Lithium Storage

As anodes for lithium-ion batteries, CoCO₃ has a much higher specific capacity than graphite and can meet the urgent demands of electric vehicles and portable electronics. However, reported CoCO₃ anodes are of micrometer-sized morphology (0.4–10 µm) that severely limits long-term and rate performances (in particular >2.0 A g⁻¹) due to intrinsically low conductivity and high volume expansion. Mesoporous materials have uniform open mesopores to offer sufficient solid/electrolyte contact, rapid Li⁺ transport, and large pore volume. However, it is still challenging to prepare uniform mesoporous CoCO₃ nanostructures. This work reports a urea–NH₄HCO₃–ethylene glycol (EG) solvothermal system to fabricate uniform mesoporous CoCO₃ nanospindles and concurrently composite with multilayered graphite nanosheets. The obtained mesoporous CoCO₃ has a specific surface area of 143.7 m² g⁻¹, 12.4 times that of commercial CoCO₃. The preparation mechanism is studied in-depth, where urea, NH₄HCO₃, EG, and crystal water play essential and respective roles. The synergistic effect of the mesopore and graphite nanosheets facilitates long-term cycling stability (1465 mAh g⁻¹ after 450 cycles at 200 mA g⁻¹ with 101.1% capacity retention) and high-rate performance (1033 mAh g⁻¹ at 2.0 A g⁻¹). The essential roles of mesopores and graphite nanosheets in boosting the kinetic change are investigated.     

High Rate and Long Cycle Life of a CNT/rGO/Si Nanoparticle Composite Anode for Lithium‐Ion Batteries

Si nanoparticle (Si‐NP) composite anode with high rate and long cycle life is an attractive anode material for lithium‐ion battery (LIB) in hybrid electric vehicle (HEV)/pure electric vehicle (PEV). In this work, a carbon nanotube (CNT)/reduced graphene oxide (rGO)/Si nanoparticle composite with alternated structure as Li‐ion battery anode is prepared. In this structure, rGO completely wraps the entire Si/CNT networks by different layers and CNT networks provide fast electron transport pathways with reduced solid‐state diffusion, so that the stable solid‐electrolyte interphase layer can form on the whole surface of the matrix instead of on single Si nanoparticle, which ensure the high cycle stability to achieve the excellent cycle performance. As a result, the CNT/rGO/Si‐NP anode exhibits high performances with long cycle life (≈455 mAh g^?1 at 15 A g^?1 after 2000 cycles), high specific charge capacity (≈2250 mAh g^?1 at 0.2 A g^?1, ≈650 mAh g^?1 at 15 A g^?1), and fast charge/discharge rates (up to 16 A g^?1). This nanostructure anode with facile and low‐cost synthesis method, as well as excellent electrochemical performances, makes it attractive for the long life cycles at high rate of the next generation LIB applications in HEV/PEV.     

Carbon-coated silicon/crumpled graphene composite as anode material for lithium-ion batteries

Silicon is a promising anode material for high-capacity Li-ion batteries (LIBs). However, its insulating property and large volume change during the lithiation/delithiation process result in poor cycling stability and in pulverization of Si. In this work, glucose-derived carbon-coated Si nanoparticles (C–Si NPs) are in conjunction with crumpled graphene (cGr) particles by a spray-drying method to prepare a novel composite (C–Si/cGr) material. The prepared C–Si NPs are uniformly embedded in the ridges of the cGr particles. The carbon layer of C–Si can make a good contact with the graphene sheet, resulting in enhanced electrical conductivity and fast charge transfer. In addition, the unique crumpled structure of the cGr can buffer the large volume change upon cycling process and facilitate the diffusion of electrolyte into the composite material. When employed as an anode electrode of LIBs, the C–Si/cGr composites deliver enhanced electrochemical performance, including stable cycling with a discharge capacity of 790 mAh·g⁻¹ after 100 cycles and a rate capability of 654 mAh·g⁻¹ at 2C. The synergistic effect of the carbon layer coating of Si NPs and the crumpled structure of the cGr particles results in a composite with improved the electrochemical performance, which is likely related to its high electrical conductivity and good mechanical stability of composite material.     

Graphene‐Based Phosphorus‐Doped Carbon as Anode Material for High‐Performance Sodium‐Ion Batteries

Graphene‐based phosphorus‐doped carbon (GPC) is prepared through a facile and scalable thermal annealing method by triphenylphosphine and graphite oxide as precursor. The P atoms are successfully doped into few layer graphene with two forms of P–O and P–C bands. The GPC used as anode material for Na‐ion batteries delivers a high charge capacity 284.8 mAh g^?1 at a current density of 50 mA g^?1 after 60 cycles. Superior cycling performance is also shown at high charge?discharge rate: a stable charge capacity 145.6 mAh g^?1 can be achieved at the current density of 500 mA g^?1 after 600 cycles. The result demonstrates that the GPC electrode exhibits good electrochemical performance (higher reversible charge capacity, super rate capability, and long‐term cycling stability). The excellent electrochemical performance originated from the large interlayer distance, large amount of defects, vacancies, and active site caused by P atoms doping. The relationship of P atoms doping amount with the Na storage properties is also discussed. This superior sodium storage performance of GPC makes it as a promising alternative anode material for sodium‐ion batteries.     

Carbon‐Encapsulated Tube‐Wire Co3O4/MnO2 Heterostructure Nanofibers as Anode Material for Sodium‐Ion Batteries

This study presents a general approach for the synthesis of carbon‐encapsulated wire‐in‐tube Co₃O₄/MnO₂ heterostructure nanofibers (Co₃O₄/MnO₂@C) via electrospinning followed by calcination. The as‐synthesized Co₃O₄/MnO₂@C is investigated as the sodium‐ion batteries anode material, which not only exhibits a high reversible capacity of 306 mAh g⁻¹ at 100 mA g⁻¹ over 200 cycles, but also shows a cycling stability of 126 mAh g⁻¹ after 1000 cycles at a high current density of 800 mA g⁻¹. The excellent electrochemical performance can be ascribed to the contribution from carbon‐encapsulated outer‐tube Co₃O₄ and inner‐wire MnO₂ heterostructures, which offer a large internal space and good electrical conductivity. The present work can be helpful in providing new insights into heterostructures for sodium‐ion batteries and other applications.     

Insert Zn Nanoparticles into the 3D Porous Carbon Ultrathin Films as a Superior Anode Material for Lithium Ion Battery

A flexible strategy is exploited to insert Zn nanoparticles into the pores of highly stable 3D network of carbon ultrathin films (P‐Zn/C) that can effectively localize the postformed Zn nanoparticles, thereby solving the problem of structural degradation, and thus achieve improved anode performance. A maximum capacity of 657.3 mA h g⁻¹ at a current density of 200 mA g⁻¹ after 50 cycles is achieved for P‐Zn/C. Even at a high current density of 2 A g⁻¹, a capacity of 653 mA h g⁻¹ is maintained after 1000 cycles, indicating that it could be a promising anode for lithium ion batteries. By comparing the capacitive and diffusion contribution qualitatively and quantitatively, the result reveals that the enhanced electrochemical performance mainly originates from the pseudocapacitance storage mechanism.     

Enlarging Surface/Bulk Ratios of NiO Nanoparticles toward High Utilization and Rate Capability for Supercapacitors

Reasonable design and delicate control of microstructures are critical to achieve high energy density of active materials for pseudocapacitors that seriously depend on usable reaction interface. This work shows the effect of ultrasmall particle size on enhancing utilization and rate performance of active materials. Three types of NiO nanocrystals with different sizes of 3.36, 6.24, and 7.18 nm in average diameter are uniformly distributed on mesoporous carbon nanosheets derived from corn straw piths. The nanosheets with 3.36 nm NiO particles present an extremely high NiO utilization of 93.4% (2404 F g⁻¹ at 0.5 A g⁻¹), which is 2–2.5-fold higher than materials with large sizes (6.24 and 7.18 nm). This enhancement is ascribed to more complete conversion and higher ionic/electronic conductivity from a preferable surface/bulk ratio of NiO. By coupling with commercial activated carbon, the asymmetric supercapacitors present high energy and power densities (28.53 Wh kg⁻¹ at 375 W kg⁻¹), with 78.3% capacitance retention after 10 000 cycles at 10 A g⁻¹.     

Structural Strategies for Germanium‐Based Anode Materials to Enhance Lithium Storage

Recently, germanium (Ge) has been arousing increasing interest as an anode for lithium‐ion batteries (LIBs) and other energy storage devices due to its high theoretical capacity (1600 mAh g^?1) and low operating voltage. There are still some critical problems to be solved before Ge can meet the high requirements for practical applications. In this Review, a series of attempts on rational design and synthesis of Ge‐based anode materials during the past few years are summarized. Structural and composition strategies that could resolve the issue of vast volume changes in Ge during cycling and enhance their electrochemical properties are focused on. The main strategies include designing nanostructures and forming Ge‐based composites and Ge‐based alloys. Lastly, the challenges for practical implementation of Ge anodes within the context of current LIB systems are discussed.     

Sulfur cloaked with different carbonaceous materials for high performance lithium sulfur batteries

Carbon matrices have attracted the attention enthusiastically as the improver materials of sulfur for rechargeable lithium-sulfur battery. In this work, various morphologies (sphere, fiber, tube and layer) based carbon materials have been used for preparing the sulfur-carbon binary composites via melt diffusion method for lithium-sulfur battery application. The prepared binary composites have been characterized for its structural and morphological information using X-ray diffraction, Fourier transform infrared spectroscopy, Raman spectroscopy, and, Scanning and Transmission electron microscopy. The electrochemical studies are characterized by cyclic voltammetry, charge-discharge and cycle life after being assembled as lithium-sulfur cell. The S-prGO composite exhibits the initial discharge capacity of 893 mAh g⁻¹ and it sustains over 50 cycles (598 mAh g⁻¹) at 0.1C, with low capacity fading rate when compared to the other composites studied. A remarkable electrochemical performance indicates that the sheet like morphology can accommodate the volume expansion of sulfur and the oxygen groups containing GO minimize the dissolution of lithium polysulfides.     

Ge Nanoparticles Encapsulated in Interconnected Hollow Carbon Boxes as Anodes for Sodium Ion and Lithium Ion Batteries with Enhanced Electrochemical Performance

A carbothermal reaction route to Ge nanoparticle homogeneously encapsulated hollow carbon boxes from NH₄H₃Ge₂O₆/resorcinol formaldehyde precursors is designed, using NH₄H₃Ge₂O₆ as a Ge precursor from commercial GeO₂ and NH₄OH. The Ge/C hybrid anode for sodium ion battery displays a higher Na⁺ storage capacity of 346 mA h g^?1 after 500 cycles at a current density of 100 mA h g^?1, almost approaching the theoretical capacity of Ge. Furthermore, Ge/C anode shows significantly improved electrochemical performance for Li⁺ storage, showing a higher initial Coulombic efficiency of 85.1% and a superior reversible capacity of 1336 mA h g^?1 at a high current density of 200 mA g^?1 after 150 cycles. An excellent rate capability with a capacity of 825 mA h g^?1 at a current density of 4.0 A g^?1 can be obtained based on Ge/C anodes. The enhanced electrochemical performance can be attributed to the unique microstructures of Ge/C hybrid anode. The internal void space of hollow carbon boxes can accommodate the volume expansion of Ge during lithiation or sodiation process, thus preserving the structural integrity of electrode material. The interconnected carbon shell can increase the electronic conductivity of the electrode, resulting in the high rate capability and cycling stability.     

Gas-Phase Synthesis of Silicon-Rich Silicon Nitride Nanoparticles for High Performance Lithium–Ion Batteries

The practical application of silicon-based anodes is severely hindered by continuous capacity fade during cycling. A very promising way to stabilize silicon in lithium–ion battery (LIB) anodes is the utilization of nanostructured silicon-rich silicon nitride (SiN_x), a conversion-type anode material. Here, SiN_x with structure sizes in the sub-micrometer range have been synthesized in a hot-wall reactor by pyrolysis of monosilane and ammonia. This work focusses on understanding process parameter–particle property correlations. Further, a model for the growth of SiN_x nanoparticles in this hot–wall–reactor design is proposed. This synthesis concept is of specific interest regarding simplicity, flexibility, and scalability: A way utilizing any mixtures of precursor gases to build multi-functional nanoparticles that can be directly used for LIBs instead of focusing on modification of nanostructures after they have been formed. Lab-scale production rates as high as 30 g h⁻¹ can be easily achieved and further scaled. SiN_0.7 nanoparticles provide a first cycle coulombic efficiency of 54%, a specific discharge capacity of 1367 mAh g⁻¹, and a capacity retention over 80% after 300 cycles at 0.5 C (j = 0.68 mA cm⁻²). These results imply that silicon-rich silicon nitrides are promising candidates for high-performance LIBs with very high durability.     

Porous NiO hollow quasi-nanospheres derived from a new metal-organic framework template as high-performance anode materials for lithium ion batteries

Porous hollow metal oxides derived from nanoscaled metal-organic framework (MOF) have drawn tremendous attention due to their high electrochemical performance in advanced Li-ion batteries (LIBs). In this work, porous NiO hollow quasi-nanospheres were fabricated by an ordinary refluxing reaction combination of a thermal decomposition of new nanostructured Ni-MOF, i.e., {Ni₃(HCOO)₆·DMF}_n. When evaluated as an anode material for lithium ion batteries, the MOF derived NiO electrode exhibits high capacity, good cycling stability and rate performance (760 mAh g^?1 at 200 mA g^?1 after 100 cycles, 392 mAh g^?1 at 3200 mA g^?1). This superior lithium storage performance is mainly attributed to the unique hollow and porous nanostructure of the as-synthesized NiO, which offer enough space to accommodate the dramstic volume change and alleviate the pulverization problem during the repeated lithiation/delithiation processes, and provide more electro-active sites for fast electrochemical reactions as well as promote lithium ions and electrons transfer at the electrolyte/electrode interface.     

Converting of the 2D graphene to its 3D by chicken red blood cells as sheets separator for construction supercapacitor electrode

Here, we report on a facile green and scalable method for the fabrication of porous 3D graphene as a well-known carbon-based material used in many energy storage devices. Chicken red blood cells were used as sheets spacer and heteroatom sources in the construction of 3D graphene. First, the red blood cells were separated from the blood and mixed with graphene oxide. Then, the mixture was freeze-dried and carbonized at 700 °C. The resulted 3D graphene containing heteroatoms was used as a supercapacitor electrode modifier on a glassy carbon electrode and tested with various electrochemical techniques. The supercapacitor electrode showed a specific capacitance of 330 F g⁻¹ at a current density of 1 A g⁻¹, maximum power density of 1958 W kg⁻¹, and maximum energy density of 85 Wh kg⁻¹. Furthermore, the supercapacitive performances were tested in a two-electrode symmetrical system which exhibited a specific capacitance of 238 F g⁻¹ for 1 A g⁻¹. It also showed a power density of 2200 W kg⁻¹ and an appreciable energy density of 160 Wh kg⁻¹. The excellent electrochemical behavior of 3D graphene indicates the promising abilities of the composite for other applications such as biosensors, batteries, electrocatalysts, etc.     

Shape-controlled porous carbon from calcium citrate precursor and their intriguing application in lithium-ion batteries

Porous carbon nanosheets (PCNSs), porous carbon nanofibers (PCNFs), and flowerlike porous carbon microspheres (FPCMs) were successfully synthesized through a carbonization method combined with a simple acid pickling treatment using calcium citrate as the precursor. The as-prepared products show uniform morphologies, in which the FPCMs are self-assembled from PCNSs. As anodes of lithium-ion (Li-ion) batteries, these carbon materials deliver a stable reversible capacity above 515 mAh g^?1 after 50 cycles at 100 mA g^?1. Compared with PCNSs and PCNFs, FPCMs demonstrate preferable rate capability (378 mAh g^?1 at 1 A g^?1) and cyclability (643 mAh g^?1 at 100 mA g^?1). These results suggest that an appropriate select of morphology and structure will significantly improve the lithium storage capacity. The study also indicates that the novel shape-controlled porous carbon materials have potential applications as electrode materials in electronic devices.     

Facile synthesis of N-doped carbon-coated Li<Subscript>4</Subscript>Ti<Subscript>5</Subscript>O<Subscript>12</Subscript> anode for application in high-rate lithium ion batteries

A facile sol-gel approach for the synthesis of lithium titanate composite decorated with N-doped carbon material (LTO/NC) is proposed. Urea is used as a nitrogen source in the proposed approach. The LTO/NC exhibits superior electrochemical performances as an electrode material for lithium-ion batteries, delivering a discharge capacity of as high as 103 mAh g^?1 at a high rate of 20 C and retaining a stable reversible capacity of 90 mAh g^?1 after 1000 cycles, corresponding to 100% capacity retention. These excellent electrochemical performances are proved by the nanoscale structure and N-doped carbon coating. NC layers were uniformly dispersed on the surface of LTO, thus preventing agglomeration, favoring the rapid migration of the inserted Li ion, and increasing the Li⁺ diffusion coefficient and electronic conductivity. LTO with the appropriate amount of NC coating is a promising anode material with applications in the development of high-powered and durable lithium-ion batteries.     

Synthesis of hollow silica-sulfur composite nanospheres towards stable lithium-sulfur battery

Herein, porous hollow silica nanospheres were prepared via a facile sol-gel process in an inverse microemulsion, using self-assemblies of chiral amphiphile as a soft template and fine water droplets as a hard template. The shells of the hollow silica nanospheres are composed of flake-like nanoparticles with dense big holes on the surface. After covering a layer of sulfur on the silica nanospheres, followed by hydrothermal treatment in a D-glucose aqueous solution, silica-sulfur and silica-sulfur-carbon nanospheres were successfully fabricated. The silica-sulfur composites exhibit a stable capacity of 454 mAh g^?1 at current density of 335 mA g^?1 after 100 cycles with capacity retention of 85%, demonstrating a promising cathode material for rechargeable lithium-sulfur batteries. We believe that the approach for synthesis of porous hollow silica nanospheres and its carbon spheroidal shell can also be applicable for designing other electrode materials for energy storage.     

Preparation of Si-PPy-Ag composites and their electrochemical performance as anode for lithium-ion batteries

The nanosilicon connected by polypyrrole (PPy) and silver (Ag) particles was simply synthesized by a chemical polymerization process in order to prepare Si-based anodes for Li-ion batteries. The phase structure, surface morphology, and electrochemical properties of the as-synthesized powders were analyzed by X-ray diffraction, FT-IR, scanning electron microscopy, and galvanostatic charge/discharge measurements. The cycle stability of the Si-PPy-Ag composites was greatly enhanced compared with the pure nanosilicon. A high capacity of more than 823 mA h g^?1 was maintained after 100 cycles. The improved electrochemical characteristics are attributed to the volume buffering effect as well as effective electronic conductivity of the polypyrrole and silver in the composite electrode.     

Effect of pyrolytic polyacrylonitrile on electrochemical performance of Si/graphite composite anode for lithium-ion batteries

The silicon/graphite (Si/G) composite was prepared using pyrolytic polyacrylonitrile (PAN) as carbon precursor, which is a nitrogen-doped carbon that provides efficient pathway for electron transfer. The combination of flake graphite and pyrolytic carbon layer accommodates the large volume expansion of Si during discharge-charge process. The Si/G composite was synthesized via cost-effective liquid solidification followed by carbonization process. The effect of PAN content on electrochemical performance of composites was investigated. The composite containing 40 wt% PAN exhibits a relatively better rate capability and cycle performance than others. It exhibits initial reversible specific capacity of 793.6 mAh g^?1 at a current density of 100 mA g^?1. High capacity of 661 mAh g^?1 can be reached after 50 cycles at current density of 500 mA g^?1.     

Improving the cycle stability and rate performance of LiNi0.91Co0.06Mn0.03O2 Ni-rich cathode material by La2O3 coating for Lithium-ion batteries

In this wok, a uniform layer of La₂O₃ is coated on the surface of LiNi_0.91Co_0.06Mn_0.03O₂ Ni-rich cathode material by using a wet coating process. The XPS and EDX analysis confirms the presence of La₂O₃ coating on the surface of NCM. The coated samples deliver the superior electrochemical performance, 0.2 wt % La₂O₃ (LaO-0.2) NCM exhibits discharge capacity of 202.7 mAh g⁻¹ in 1^st cycle and delivered the cycle stability of 87.2% after 100 cycles. Besides, the enhanced capacity retention, LaO-0.2 has delivered very high discharge capacity of 80.3 mAh g⁻¹ at very high C-rate of 5C while the pristine sample shows very low discharge capacity (33.4 mAh g⁻¹). CV results shows the significant suppression in the intensity of H2–H3 which indicates the superior electrochemical stability of LaO-0.2 NCM. Thus, we can confirm that La₂O₃ coating is promising technique to achieve superior electrochemical performance in the long term cycling process.