An investigation of Li2TiO3–coke composite anode material for Li-ion batteries

Anode material Li₂TiO₃–coke was prepared and tested for lithium-ion batteries. The as-prepared material exhibits excellent cycling stability and outstanding rate performance. Charge/discharge capacities of 266 mA h g⁻¹ at 0.100 A g⁻¹ and 200 mA h g⁻¹ at 1.000 A g⁻¹ are reached for Li₂TiO₃–coke. A cycling life-time test shows that Li₂TiO₃–coke gives a specific capacity of 264 mA h g⁻¹ at 0.300 A g⁻¹ and a capacity retention of 92% after 1000 cycles of charge/discharge.

Anode material Li₂TiO₃–coke was prepared and tested for lithium-ion batteries. The as-prepared material exhibits excellent cycling stability and outstanding rate performance.     

The influence of different Si : C ratios on the electrochemical performance of silicon/carbon layered film anodes for lithium-ion batteries

With a high specific capacity (4200 mA h g⁻¹), silicon based materials have become the most promising anode materials in lithium-ions batteries. However, the large volume expansion makes the capacity reduce rapidly. In this work, a periodic silicon/carbon (Si/C) multilayer thin film was synthesized by magnetron sputtering method on copper foil. The titanium (Ti) film (about 20 nm) as the transition layer was deposited on the copper foil prior to the deposition of the multilayer film. Superior electrochemical lithium storage performance was obtained by the multilayer thin film. The initial discharge and charge specific capacity of the Si (15 nm)/C (5 nm) multilayer film anode are 2640 mA h g⁻¹ and 2560 mA h g⁻¹ with an initial coulombic efficiency of ∼97%. The retention specific capacity is about 2300 mA h g⁻¹ and there is ∼87% capacity retention after 200 cycles.

With a high specific capacity (4200 mA h g⁻¹), silicon based materials have become the most promising anode materials in lithium-ions batteries.     

Design and synthesis of graphene/SnO2/polyacrylamide nanocomposites as anode material for lithium-ion batteries

Tin dioxide (SnO₂) is a promising anode material for lithium-ion batteries owing to its large theoretical capacity (1494 mA h g⁻¹). However, its practical application is hindered by these problems: the low conductivity, which restricts rate performance of the electrode, and the drastic volume change (400%). In this study, we designed a novel polyacrylamide/SnO₂ nanocrystals/graphene gel (PAAm@SnO₂NC@GG) structure, in which SnO₂ nanocrystals anchored in three-dimensional graphene gel network and the polyacrylamide layers could effectively prevent the agglomeration of SnO₂ nanocrystals, presenting excellent cyclability and rate performance. A capacity retention of over 90% after 300 cycles of 376 mA h g⁻¹ was achieved at a current density of 5 A g⁻¹. In addition, a stable capacity of about 989 mA h g⁻¹ at lower current density of 0.2 A g⁻¹ was achieved.

Tin dioxide (SnO₂) is a promising anode material for lithium-ion batteries owing to its large theoretical capacity (1494 mA h g⁻¹).     

Bagasse as a carbon structure with high sulfur content for lithium–sulfur batteries

A bagasse-based 3D carbon matrix (BC) with high specific surface area and high conductivity was obtained by carbonization and pore-forming processes with bagasse as the carbon precursor and K₂FeO₄ as the pore-former. The microporous structure and nitrogenous functional groups were determined in the prepared carbon matrix, which could allow high sulfur loading and improve the polysulfide absorption capacity during cycling. After sulfur infusion, the S/BC composite with 68.8% sulfur content was obtained. The lithium–sulfur (Li–S) battery with the S/BC cathode shows high specific capacity and good cycling performance. It delivers a specific capacity of 1360 mA h g⁻¹ at 0.2C and remains at 790 mA h g⁻¹ after 200 cycles. At 1C, the Li–S with this composite cathode exhibits 601 mA h g⁻¹ after 150 cycles. This work offers a new kind of green material and a new method for Li–S batteries.

Bagasse-based carbon matrix with microporous structure and nitrogenous functional groups could have high sulfur loading and excellent polysulfide absorption capacity.     

The effect of graphitization degree of carbonaceous material on the electrochemical performance for aluminum-ion batteries

Aluminum-ion batteries are currently regarded as the most promising energy storage batteries. The recent development of aluminum-ion batteries has been greatly promoted based on the use of graphitic carbon materials as a positive electrode. However, it remains unclear whether all carbonaceous materials can achieve excellent electrochemical behaviour similar to graphite. In this study, the correlation between the graphitization degree and capacity of a graphite electrode is systematically investigated for aluminum-ion batteries. The results show that the higher the graphitization degree, the larger the charge/discharge capacity and the better the cycling stability. Moreover, graphite nanoflakes with the highest graphitization degree deliver an initial discharge capacity of 66.5 mA h g⁻¹ at a current density of 100 mA g⁻¹, eventually retaining 66.3 mA h g⁻¹ after 100 cycles with a coulombic efficiency of 96.1% and capacity retention of 99.7%, exhibiting an ultra-stable cycling performance. More importantly, it can be concluded that the discharge capacity of different kinds of graphite materials can be predicted by determining the graphitization degree.

The discharge capacity of graphitic carbon from non-graphitizable carbon strongly depends on the graphitization degree when used for aluminum-ion batteries.     

Suppressing self-discharge of Li–B/CoS2 thermal batteries by using a carbon-coated CoS2 cathode

Thermal batteries with molten salt electrolytes are used for many military applications, primarily as power sources for guided missiles. The Li–B/CoS₂ couple is designed for high-power, high-voltage thermal batteries. However, their capacity and safe properties are influenced by acute self-discharge that results from the dissolved lithium anode in molten salt electrolytes. To solve those problems, in this paper, carbon coated CoS₂ was prepared by pyrolysis reaction of sucrose at 400 °C. The carbon coating as a physical barrier can protect CoS₂ particles from damage by dissolved lithium and reduce the self-discharge reaction. Therefore, both the discharge efficiency and safety of Li–B/CoS₂ thermal batteries are increased remarkably. Discharge results show that the specific capacity of the first discharge plateau of carbon-coated CoS₂ is 243 mA h g⁻¹ which is 50 mA h g⁻¹ higher than that of pristine CoS₂ at a current density of 100 mA cm⁻². The specific capacity of the first discharge plateau at 500 mA cm⁻² for carbon-coated CoS₂ and pristine CoS₂ are 283 mA h g⁻¹ and 258 mA h g⁻¹ respectively. The characterizations by XRD and DSC indicate that the carbonization process has no noticeable influence on the intrinsic crystal structure and thermal stability of pristine CoS₂.

Suppressing self-discharge of Li–B/CoS₂ thermal batteries through modifying the CoS₂ cathode with a protective carbon coating layer.     

Hierarchical porous ZnMnO3 yolk–shell microspheres with superior lithium storage properties enabled by a unique one-step conversion mechanism

ZnMnO₃ has attracted enormous attention as a novel anode material for rechargeable lithium-ion batteries due to its high theoretical capacity. However, it suffers from capacity fading because of the large volumetric change during cycling. Here, porous ZnMnO₃ yolk–shell microspheres are developed through a facile and scalable synthesis approach. This ZnMnO₃ can effectively accommodate the large volume change upon cycling, leading to an excellent cycling stability. When applying this ZnMnO₃ as the anode in lithium-ion batteries, it shows a remarkable reversible capacity (400 mA h g⁻¹ at a current density of 400 mA g⁻¹ and 200 mA h g⁻¹ at 6400 mA g⁻¹) and excellent cycling performance (540 mA h g⁻¹ after 300 cycles at 400 mA g⁻¹) due to its unique structure. Furthermore, a novel conversion reaction mechanism of the ZnMnO₃ is revealed: ZnMnO₃ is first converted into intermediate phases of ZnO and MnO, after which MnO is further reduced to metallic Mn while ZnO remains stable, avoiding the serious pulverization of the electrode brought about by lithiation of ZnO.

ZnMnO₃ has attracted enormous attention as a novel anode material for rechargeable lithium-ion batteries due to its high theoretical capacity.     

Double-layer carbon protected CoS2 nanoparticles as an advanced anode for sodium-ion batteries

Cobalt disulfides with high theoretical capacity are regarded as appropriate anode materials for sodium ion batteries (SIBs), but their intrinsically low conductivity and large volume expansion lead to a poor electrochemical performance. In this work, graphitic carbon coated CoS₂ nanoparticles are encapsulated in bamboo-like carbon nanotubes by pyrolysis and sulfidation process. Graphitic carbon can improve the electrical conductivity and prevent the agglomeration of CoS₂ nanoparticles. Meanwhile, bamboo-like carbon nanotubes can serve as conductive skeleton frames to provide rapid and constant transport pathways for electrons and offer void space to buffer the volume change of CoS₂ nanoparticles. The advanced anode material exhibits a long-term capacity of 432.6 mA h g⁻¹ at 5 A g⁻¹ after 900 cycles and a rate capability of 419.6 mA h g⁻¹ even at 10 A g⁻¹ in the carbonate ester-based electrolyte. This avenue can be applicable for preparing other metal sulfide/carbon anode materials for sodium-ion batteries.

The outstanding electrochemical performance is ascribed to the novel structure design of CoS₂@GC@B-CNT.     

Hard carbon spheres prepared by a modified Stöber method as anode material for high-performance potassium-ion batteries

The Stöber method is a highly efficient synthesis strategy for homogeneous monodisperse polymer colloidal spheres and carbon spheres. This work delivers an extended Stöber method and investigates the synthesis process. By calcining the precursor under appropriate conditions, solid secondary particles of amorphous carbon (SSAC) and hollow secondary particles of graphitized carbon (HSGC) can be directly synthesized. The two materials have a nano-primary particle structure and a closely-packed sub-micron secondary particle structure, which can be used in energy storage. We find that SSAC and HSGC have high potassium-ion storage capacity with reversible capacities of 274 mA h g⁻¹ and 283 mA h g⁻¹ at 20 mA g⁻¹ respectively. Significantly, SSAC has better rate performance with a specific capacity of 107 mA h g⁻¹ at 1 A g⁻¹.

A modified Stöber method synthesizes resorcinol-formaldehyde resin-based secondary particle hard carbon spheres as anode material for high-performance potassium-ion batteries.     

Preparation and lithium storage of core–shell honeycomb-like Co3O4@C microspheres

Core–shell honeycomb-like Co₃O₄@C microspheres were synthesized via a facile solvothermal method and subsequent annealing treatment under an argon atmosphere. Owing to the core–shell honeycomb-like structure, a long cycling life was achieved (a high reversible specific capacity of 318.9 mA h g⁻¹ was maintained at 5C after 1000 cycles). Benefiting from the coated carbon layers, excellent rate capability was realized (a reversible specific capacity as high as 332.6 mA h g⁻¹ was still retained at 10C). The design of core–shell honeycomb-like microspheres provides a new idea for the development of anode materials for high-performance lithium-ion batteries.

The reversible specific capacity of CSHCo₃O₄@C microspheres was as high as 332.6 mA h g⁻¹ at 10C, which was significantly higher than that of SCo₃O₄ microspheres (68.7 mA h g⁻¹).     

Highly crystalline nickel hexacyanoferrate as a long-life cathode material for sodium-ion batteries

Prussian blue analogs (PBAs) are attractive cathode candidates for high energy density, including long life-cycle rechargeable batteries, due to their non-toxicity, facile synthesis techniques and low cost. Nevertheless, traditionally synthesized PBAs tend to have a flawed crystal structure with a large amount of [Fe(CN)₆]⁴⁻ openings and the presence of crystal water in the framework; therefore the specific capacity achieved has continuously been low with poor cycling stability. Herein, we demonstrate low-defect and sodium-enriched nickel hexacyanoferrate nanocrystals synthesized by a facile low-speed co-precipitation technique assisted by a chelating agent to overcome these problems. As a consequence, the prepared high-quality nickel hexacyanoferrate (HQ-NiHCF) exhibited a high specific capacity of 80 mA h g⁻¹ at 15 mA g⁻¹ (with a theoretical capacity of ∼85 mA h g⁻¹), maintaining a notable cycling stability (78 mA h g⁻¹ at 170 mA g⁻¹ current density) without noticeable fading in capacity retention after 1200 cycles. This low-speed synthesis strategy for PBA-based electrode materials could be also extended to other energy storage materials to fabricate high-performance rechargeable batteries.

A low-speed synthesis strategy was designed to fabricate Prussian blue analog based electrode materials for high-performance rechargeable batteries.     

In situ production of a two-dimensional molybdenum disulfide/graphene hybrid nanosheet anode for lithium-ion batteries

A solvent-free, low-cost, high-yield and scalable single-step ball milling process is developed to construct 2D MoS₂/graphene hybrid electrodes for lithium-ion batteries. Electron microscopy investigation reveals that the obtained hybrid electrodes consist of numerous nanosheets of MoS₂ and graphene which are randomly distributed. The MoS₂/graphene hybrid anodes exhibit excellent cycling stability with high reversible capacities (442 mA h g⁻¹ for MoS₂/graphene (40 h); 553 mA h g⁻¹ for MoS₂/graphene (20 h); 342 mA h g⁻¹ for MoS₂/graphene (10 h)) at a high current rate of 250 mA g⁻¹ after 100 cycles, whereas the pristine MoS₂ electrode shows huge capacity fading with a retention of 37 mA h g⁻¹ at 250 mA g⁻¹ current after 100 cycles. The incorporation of graphene into MoS₂ has an extraordinary effect on its electrochemical performance. This work emphasises the importance of the construction of the 2D MoS₂/graphene hybrid structure to prevent capacity fading issues with the MoS₂ anode in lithium-ion batteries.

A solvent-free, low-cost, high-yield and scalable single-step ball milling process is developed to construct 2D MoS₂/graphene hybrid electrodes for lithium-ion batteries.     

MoS2/carbon composites prepared by ball-milling and pyrolysis for the high-rate and stable anode of lithium ion capacitors

Lithium ion capacitors (LICs), bridging the advantages of batteries and electrochemical capacitors, are regarded as one of the most promising energy storage devices. Nevertheless, it is always limited by the anodes that accompany with low capacity and poor rate performance. Here, we develop a versatile and scalable method including ball-milling and pyrolysis to synthesize exfoliated MoS₂ supported by N-doped carbon matrix derived from chitosan, which is encapsulated by pitch-derived carbon shells (MoS₂/CP). Because the carbon matrix with high nitrogen content can improve the electron conductivity, the robust carbon shells can suppress the volume expansion during cycles, and the sufficient exfoliation of lamellar MoS₂ can reduce the ions transfer paths, the MoS₂/CP electrode delivers high specific capacity (530 mA h g⁻¹ at 100 mA g⁻¹), remarkable rate capability (230 mA h g⁻¹ at 10 A g⁻¹) and superior cycle performance (73% retention after 250 cycles). Thereby, the LICs, composed of MoS₂/CP as the anode and commercial activated carbon (21 KS) as the cathode, exhibit high power density of 35.81 kW kg⁻¹ at 19.86 W h kg⁻¹ and high energy density of 87.74 W h kg⁻¹ at 0.253 kW kg⁻¹.

MoS₂/carbon composites prepared by ball-milling and pyrolysis for the high-rate anode of lithium ion capacitors.     

NaV6O15 microflowers as a stable cathode material for high-performance aqueous zinc-ion batteries

Reversible aqueous zinc-ion batteries (ZIBs) have great potential for large-scale energy storage owing to their low cost and safety. However, the lack of long-lifetime positive materials severely restricts the development of ZIBs. Herein, we report NaV₆O₁₅ microflowers as a cathode material for ZIBs with excellent electrochemical performance, including a high specific capacity of ∼300 mA h g⁻¹ at 100 mA g⁻¹ and 141 mA h g⁻¹ maintained after 2000 cycles at 5 A g⁻¹ with a capacity retention of ∼107%. The high diffusion coefficient and stable tunneled structure of NaV₆O₁₅ facilitate Zn²⁺ intercalation/extraction and long-term cycle stability.

NaV₆O₁₅ microflowers were synthesized as a stable cathode material for aqueous zinc ion batteries, which show a high specific capacity and excellent long-term cycling performance.     

Silica from diatom frustules as anode material for Li-ion batteries

In spite of its insulating nature, SiO₂ may be utilized as active anode material for Li-ion batteries. Synthetic SiO₂ will typically require sophisticated synthesis and/or activation procedures in order to obtain a satisfactory performance. Here, we report on diatom frustules as active anode material without the need for extensive activation procedures. These are composed primarily of silica, exhibiting sophisticated porous structures. Various means of optimizing the performance were investigated. These included carbon coating, the addition of fluoroethylene carbonate (FEC) and vinylene carbonate (VC) to the carbonate-based electrolyte, as well as activation by an initial potentiostatic hold step. The highest capacity (723 mA h g⁻¹) was obtained with composite electrodes with pristine diatom frustules and conventional carbon black as additive, with the capacity still increasing after 50 cycles. The capacity was around 624 mA h g⁻¹ after subtraction of the contributions from the carbon black. Carbon coated diatom frustules showed a slightly lower but stable capacity after 50 cycles (600 mA h g⁻¹ after subtraction of contributions from the carbon coating and the carbon black). By the use of electrochemical characterization methods, as well as post-mortem studies, differences in reaction mechanisms could be identified and attributed to the operating and processing parameters.

Silica derived from algae was used as anode material in Li-ion batteries, giving a capacity of more than 700 mA h g⁻¹.     

Enhanced storage behavior of quasi-solid-state aluminum–selenium battery

The current aluminum batteries with selenium positive electrodes have been suffering from dramatic capacity loss owing to the dissolution of Se₂Cl₂ products on the Se positive electrodes in the ionic liquid electrolyte. For addressing this critical issue and achieving better electrochemical performances of rechargeable aluminum–selenium batteries, here a gel-polymer electrolyte which has a stable and strongly integrated electrode/electrolyte interface was adopted. Quite intriguingly, such a gel-polymer electrolyte enables the solid-state aluminum–selenium battery to present a lower self-discharge and obvious discharging platforms. Meanwhile, the discharge capacity of the aluminum–selenium battery with a gel-polymer electrolyte is initially 386 mA h g⁻¹ (267 mA h g⁻¹ in ionic liquid electrolyte), which attenuates to 79 mA h g⁻¹ (32 mA h g⁻¹ in ionic liquid electrolyte) after 100 cycles at a current density of 200 mA g⁻¹. The results suggest that the employment of a gel-polymer electrolyte can provide an effective route to improve the performance of aluminum–selenium batteries in the first few cycles.

A quasi-solid-state aluminum–selenium battery has been established using gel-polymer electrolyte between the Se positive electrode and Al negative electrode which increasing the utilization of the active materials.     

Performance optimization of freestanding MWCNT-LiFePO4 sheets as cathodes for improved specific capacity of lithium-ion batteries

The typical lithium-ion-battery positive electrode of “lithium-iron phosphate (LiFePO₄) on aluminum foil” contains a relatively large amount of inactive materials of 29 wt% (22 wt% aluminum foil + 7 wt% polymeric binder and graphitic conductor) which limits its maximum specific capacity to 120.7 mA h g⁻¹ (71 wt% LiFePO₄) instead of 170 mA h g⁻¹ (100 wt% LiFePO₄). We replaced the aluminum current-collector with a multi-walled carbon nanotube (MWCNT) network. We optimized the specific capacity of the “freestanding MWCNT-LiFePO₄” positive electrode. Through the optimization of our unique surface-engineered tape-cast fabrication method, we demonstrated the amount of LiFePO₄ active materials can be as high as 90 wt% with a small amount of inactive material of 10 wt% MWCNTs. This translated to a maximum specific capacity of 153 mA h g⁻¹ instead of 120.7 mA h g⁻¹, which is a significant 26.7% gain in specific capacity compared to conventional cathode design. Experimental data of the freestanding MWCNT-LiFePO₄ at a low discharge rate of 17 mA g⁻¹ show an excellent specific capacity of 144.9 mA h g⁻¹ which is close to its maximum specific capacity of 153 mA h g⁻¹. Furthermore, the freestanding MWCNT-LiFePO₄ has an excellent specific capacity of 126.7 mA h g⁻¹ after 100 cycles at a relatively high discharge rate of 170 mA g⁻¹ rate.

We optimized the specific capacity of freestanding MWCNT-LiFePO₄ positive electrode. We demonstrated as high (low) as 90 wt% LiFePO₄ active material (10 wt% MWCNTs inactive material). This corresponded to a maximum specific capacity of 153 mA h g⁻¹.     

TiO2-decorated porous carbon nanofiber interlayer for Li–S batteries

Lithium–sulfur (Li–S) batteries are the most promising energy storage systems owing to their high energy density. However, shuttling of polysulfides detracts the electrochemical performance of Li–S batteries and thus prevents the commercialization of Li–S batteries. Here, TiO₂@porous carbon nanofibers (TiO₂@PCNFs) are fabricated via combining electrospinning and electrospraying techniques and the resultant TiO₂@PCNFs are evaluated for use as an interlayer in Li–S batteries. TiO₂ nanoparticles on PCNFs are observed from SEM and TEM images. A high initial discharge capacity of 1510 mA h g⁻¹ is achieved owing to the novel approach of electrospinning the carbon precursor and electrospraying TiO₂ nanoparticles simultaneously. In this approach TiO₂ nanoparticles capture polysulfides with strong interaction and the PCNFs with high conductivity recycle and re-use the adsorbed polysulfides, thus leading to high reversible capacity and stable cycling performance. A high reversible capacity of 967 mA h g⁻¹ is reached after 200 cycles at 0.2C. The cell with the TiO₂@PCNF interlayer also delivers a reversible capacity of around 1100 mA h g⁻¹ at 1C, while the cell without the interlayer exhibits a lower capacity of 400 mA h g⁻¹. Therefore, this work presents a novel approach for designing interlayer materials with exceptional electrochemical performance for high performance Li–S batteries.

Lithium–sulfur (Li–S) batteries are the most promising energy storage systems owing to their high energy density.     

A facile synthesis of CuSe nanosheets for high-performance sodium-ion hybrid capacitors

Due to the low price and abundant reserves of sodium resources, sodium-ion batteries have become the main candidate for the next generation of energy storage equipment, particularly for large-scale grid storage and low-speed electric vehicles. Transition metal selenides have attracted considerable attention because of their high reversible capacity, superior electrical conductivity and versatile structures. In this study, two-dimensional CuSe nanosheets are synthesized via a simple hydrothermal reaction. When acting as an electrode material for sodium-ion batteries, the CuSe electrode exhibits an initial coulombic efficiency of 96.7% at a current density of 0.1 A g⁻¹ and a specific capacity of 330 mA h g⁻¹ after 100 operation cycles, as well as retains a specific capacity of 211 mA h g⁻¹ even at a high current density of 10 A g⁻¹. Moreover, the anode delivers a specific capacity of 236 mA h g⁻¹ after 3300 cycles at 5 A g⁻¹ with a capacity retention of 91.2%. In sodium-ion hybrid capacitors (SHICs) with the two-dimensional CuSe nanosheets and Ti₃C₂T_x MXene as the negative and positive materials, respectively, the nanosheets without any pre-sodiation present a lifespan of up to 2000 cycles at 2 A g⁻¹ and a capacity retention of about 77.7%.

Due to the low price and abundant reserves of sodium resources, sodium-ion batteries have become the main candidate for the next generation of energy storage equipment, particularly for large-scale grid storage and low-speed electric vehicles.     

Ultrafine MoO2 nanoparticles encapsulated in a hierarchically porous carbon nanofiber film as a high-performance binder-free anode in lithium ion batteries

Flexible free-standing hierarchically porous carbon nanofibers embedded with ultrafine (∼3.5 nm) MoO₂ nanoparticles (denoted as MoO₂@HPCNFs) have been synthesized by electrospinning and subsequent heat treatment. When evaluated as a binder-free anode in Li-ion batteries, the as-obtained MoO₂@HPCNFs film exhibits excellent capacity retention with high reversible capacity (≥1055 mA h g⁻¹ at 100 mA g⁻¹) and good rate capability (425 mA h g⁻¹ at 2000 mA g⁻¹), which is much superior to most of the previously reported MoO₂-based materials. The synergistic effect of uniformly dispersed ultrasmall MoO₂ nanoparticles and a three-dimensionally hierarchical porous conductive network constructed by HPCNFs effectively improve the utilization rate of active materials, enhance the transport of both electrons and Li⁺ ions, facilitate the electrolyte penetration, and promote the Li⁺ storage kinetics and stability, thus leading to a greatly enhanced electrochemical performance.

A novel binder-free LIB anode made of ultrafine MoO₂ nanoparticles encapsulated in hierarchically porous carbon nanofibers exhibits high Li-storage performance.