Synthesis Strategies and Applications for Pitch-Based Anode: From Industrial By-Products to Power Sources

It is significant for saving energy to manufacture superb-property batteries. Carbon is one of the most competitive anode materials in batteries, but it is hard for commercial graphite anodes to meet the increasingly higher energy-storage requirements. Moreover, the price of other better-performing carbon materials (such as graphene) is much higher than graphite, which is not conducive to massive production. Pitch, the cheap by-product in the petroleum and coal industries, has high carbon content and yield, making it possible for commercialization. Developing pitch-based anodes can not only lower raw material costs but also realize the pitch's high value-added utilization. We comprehensively reviewed the latest synthesis strategies of pitch-derived materials and then introduced their application and research progress in lithium, sodium, and potassium ion batteries (LIBs, SIBs, and PIBs). Finally, we summarize and suggest the pitch's development trend for anodes and in other fields.

Bimetallic CuSbSe2 : A Potential Anode Material for Sodium and Lithium-Ion Batteries with High-Rate Capability and Long-Term Stability

Bimetallic transition metal chalcogenides (TMCs) materials have emerged as attractive anodes for lithium-ion batteries (LIBs) and sodium-ion batteries (SIBs) because of the high intrinsic electronic conductivity, rich redox sites and unique reaction mechanism. In this work, we report the synthesis and electrochemical properties of a novel bimetallic TMCs material CuSbSe₂ . The as-prepared anode delivers a high reversible capacity of 545.6  mA h g^-1 for SIBs and 592.6  mA h g^-1 for LIBs at a current density of 0.2 A g^-1 , and an excellent rate capability of 425.9  mA h g^-1 at 20 A g^-1 for SIBs and 226.0  mA h g^-1 at 10 A g^-1 for LIBs without any common-used surface modification or carbonaceous compositing. In addition, ex situ X-ray diffraction (XRD) and High-resolution transmission electron microscopy (HRTEM) reveal a combined conversion-alloying reaction mechanism of LIBs and NIBs. Our findings suggest bimetallic CuSbSe₂ could be a potential anode material for both SIBs and LIBs.

Defective Bi2S3 Anchored on CuS/C as an Ultrafast and Long-Life Anode for Sodium-Ion Storage

Due to the high electrical conductivity and abundant redox active sites, bimetal sulfides are highly competitive anode materials for sodium storage with long-life and high-rate. Herein, a heterostructured metal sulfide (Bi₂S₃-CuS) with a carbon-based support is prepared by calcination and ion exchange methods. The synergistic effects of the heterostructure and defective structure provide facile diffusion channels, fast Na⁺ migration, and plentiful active sites for Na⁺, which reflect in the impressive electrochemical performance with a high reversible capacity of 592.2 mA h g^-1 after 1000 cycles at 8 A g^-1. Furthermore, the Na-ion full batteries exhibit an ultra-long cycling performance with a value of 216 mA h g^-1 after 4000 cycles at 10 A g^-1. Interestingly, the defective structure of Bi₂S₃ remains after cycling. Kinetic analyses and density functional theoretical calculations clarified that the heterointerfacial structure, especially on the interface containing sulfur defects in Bi₂S₃ of Bi₂S₃-CuS, could induce feasible ion adsorption and promote ion transfer, which lays the foundation for achieving ultrafast sodiation kinetics.

Molten Salt-Assisted Construction of Hollow Carbon Spheres with Outer-Order and Inner-Disorder Heterostructure for Ultra-Stable Potassium Ion Storage

The central goal of high-performance potassium ion storage is to control the function of the anode material via rational structural design. Herein, N- and S-doped hollow carbon spheres with outer-short-range-order and inner-disorder structures are constructed to achieve highly efficient and ultra-stable potassium ion storage using a low-temperature molten salt system. The ultrathin carbon walls and uniform mesoporous as well as unique heterostructure synergistically realize significant potassium storage performance via facilitating rapid diffusion of potassium ions and alleviating substantial volume expansion. Furthermore, as the anode of a potassium ion battery, the as-prepared MSTC electrode demonstrates a state-of-the-art cycling capability of 221.3 mAh g^-1 at 1 A g^-1 after 20,000 cycles. The assembled potassium ion hybrid capacitor device demonstrates a high energy of 157 Wh kg^-1 at 956 W kg^-1 and excellent reversibility at a current density of 5.0 A g^-1 after 20,000 cycles with 82.7% capacity retention. Accordingly, our work provides new ideas for designing advanced carbon anode materials and understanding the charge storage mechanism in potassium ion battery, as well as constructing high energy-power density potassium-ion hybrid capacitors (PIHCs).

Role of Crystalline Si and SiC Species in the Performance of Reduced Hybrid C/Si Gels as Anodes for Lithium-Ion Batteries

In recent years, the research on lithium-ion batteries (LIBs) to improve their lifetime, efficiency and energy density has led to the use of silicon-based materials as a promising anode alternative to graphite. Specifically, crystalline silicon (cSi) and silicon carbide (SiC) obtained from deposition or reduction processes (e.g., magnesiothermal reduction) stand out for their electrochemical properties. However, the synthesis routes proposed until now have limitations that make them difficult to afford or operate on a large scale. For this reason, in this work, carbon-silicon (C-Si) hybrid materials synthesized through an efficient route are evaluated as the potential precursor for the obtention of both cSi and SiC species in a single material. The feasibility and influence of the magnesiothermal reduction process were evaluated, and materials with 10 wt.% of reduced Si and 10-26 wt.% of SiC were obtained. Both species play a role in the improvement of the performance of silicon-based materials as anodes in lithium-ion batteries. In comparison with materials obtained by the reduction of silica gels and composites, the reduced C-Si hybrid gels stand out thanks to the homogeneous distribution and stability of the species developed.

Carbon Quantum Dots-Derived Carbon Nanosphere Coating on Ti3C2 MXene as a Superior Anode for High-Performance Potassium-Ion Batteries

Potassium-ion batteries (PIBs) are receiving increasing attention at present because of their cheap and lithium-like charge/discharge processes. Nevertheless, the large potassium-ion radius leads to poor potassium intercalation/depotassium kinetics and unstable structure, hindering their development. Here, we synthesized a novel carbon quantum dot-derived carbon nanosphere-encapsulated Ti₃C₂ MXene (CNS@Ti₃C₂) composite by polymer pyrolysis, while carbon nanospheres were derived from carbon quantum dots. The composites can suppress the layer stacking of Ti₃C₂ and prevent oxidation, thereby stabilizing the layered structure of Ti₃C₂ MXene and improving the cycle life. Besides, carbon nanospheres can increase the specific surface area and active sites, and then more potassium ions can enter the electrode material and boost the reversible capacity. Further, carbon nanospheres are embedded between the Ti₃C₂ layers, which can increase the interlayer spacing, and the potassium ions are more easily inserted and extracted, thereby improving the potassium storage power and rate performance. The CNS@Ti₃C₂ composite possesses an excellent synergy, resulting in a high reversible capacity of 229 mAh g^-1 at 100 mA g^-1 after 200 repeated cycles and a long cycle life of 205 mAh g^-1 at 500 mA g^-1 after 1000 repeated cycles with high coulombic efficiency (above 99%). This work offers a novel strategy to utilize carbon with MXene in energy storage.

Nanocapsule of MnS Nanopolyhedron Core@CoS Nanoparticle/Carbon Shell@Pure Carbon Shell as Anode Material for High-Performance Lithium Storage

MnS has been explored as an anode material for lithium-ion batteries due to its high theoretical capacity, but low electronic conductivity and severe volume change induce low reversible capacity and poor cycling performance. In this work, the nanocapsule consisting of MnS nanopolyhedrons confined in independent, closed and conductive hollow polyhedral nanospheres is prepared by embedding MnCO₃ nanopolyhedrons into ZIF-67, followed by coating of RF resin and gaseous sulfurization/carbonization. Benefiting from the unique nanocapsule structure, especially inner CoS/C shell and outer pure C shell, the MnS@CoS/C@C composite as anode material presents excellent cycling performance (674 mAh g^-1 at 1 A g^-1 after 300 cycles; 481 mAh g^-1 at 5 A g^-1 after 300 cycles) and superior rate capability (1133.3 and 650.6 mAh g^-1 at 0.1 and 4 A g^-1), compared to the control materials (MnS and MnS@CoS/C) and other MnS composites. Kinetics measurements further reveal a high proportion of the capacitive effect and low reaction impedance of MnS@CoS/C@C. SEM and TEM observation on the cycled electrode confirms superior structural stability of MnS@CoS/C@C during long-term cycles. Excellent lithium storage performance and the convenient synthesis strategy demonstrates that the MnS@CoS/C@C nanocapsule is a promising high-performance anode material.

Selectivity of Oxygen Evolution Reaction on Carbon Cloth-Supported δ-MnO2 Nanosheets in Electrolysis of Real Seawater

Electrolysis of seawater using solar and wind energy is a promising technology for hydrogen production which is not affected by the shortage of freshwater resources. However, the competition of chlorine evolution reactions and oxygen evolution reactions on the anode is a major obstacle in the upscaling of seawater electrolyzers for hydrogen production and energy storage, which require chlorine-inhibited oxygen evolution electrodes to become commercially viable. In this study, such an electrode was prepared by growing δ-MnO₂ nanosheet arrays on the carbon cloth surface. The selectivity of the newly prepared anode towards the oxygen evolution reaction (OER) was 66.3% after 30 min of electrolyzer operation. The insertion of Fe, Co and Ni ions into MnO₂ nanosheets resulted in an increased number of trivalent Mn atoms, which had a negative effect on the OER selectivity. Good tolerance of MnO₂/CC electrodes to chlorine evolution in seawater electrolysis indicates its suitability for upscaling this important energy conversion and storage technology.

A Study on High-Rate Performance of Graphite Nanostructures Produced by Ball Milling as Anode for Lithium-Ion Batteries

Graphite, with appealing features such as good stability, high electrical conductivity, and natural abundance, is still the main commercial anode material for lithium-ion batteries. The charge-discharge rate capability of graphite anodes is not significant for the development of mobile devices and electric vehicles. Therefore, the feasibility investigation of the rate capability enhancement of graphite by manipulating the structure is worthwhile and of interest. In this study, an effective ball-milling process has been set up by which graphite nanostructures with a high surface area are produced. An in-depth investigation into the effect of ball milling on graphite structure as well as electrochemical performance, particularly rate capability, is conducted. Here, we report that graphite nanoflakes with 350 m² g^-1 surface area deliver retained capacity of ~75 mAh g^-1 at 10 C (1 C = 372 mA g^-1). Finally, the Li⁺ surface-storage mechanism is recognised by associating the structural characteristics with electrochemical properties.

Rational Development of IT-SOFC Electrodes Based on the Nanofunctionalization of La0.6Sr0.4Ga0.3Fe0.7O3 with Oxides. Part 2: Anodes by Means of Manganite Oxide

To promote the diffusion on the market of solid oxide fuel cell (SOFC) devices, the use of fuels other than the most appealing hydrogen and also decreasing the working temperature could show the way forward. In the first part, we concentrated our efforts on cathodes; hereby, we focused on anodes and concentrated our efforts to develop a sustainable multifuel anode. We decided to develop LSGF (La_0.6Sr_0.4Ga_0.3Fe_0.7O₃)-based nanocomposites by depositing manganite oxide to enhance the performance toward propane. MnO_x has been deposited by a wet impregnation method, and the powders have been largely characterized by X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray analysis, X-ray photoelectron spectroscopy, hydrogen temperature-programmed reduction, oxygen temperature-programmed desorption, and N₂ adsorption. Cell performances were first collected in hydrogen as a function of both the temperature and hydrogen content. EIS measurements were studied using Nyquist and Bode plots, and they show two processes at high frequency, assigned to charge transfer at the electrode/electrolyte interface, and at low frequency due to the dissociative adsorption of hydrogen. The Arrhenius plot of area specific resistance suggests two different trends, and the activation energy decreases from 117 kJ/mol at 750 °C to 46 kJ/mol above that temperature. This behavior is often connected to chemical modification of the catalyst or changes in the limiting step processes. Power densities in hydrogen and propane were determined at 744 °C after 1 h of operation, achieving 70 mW/cm² in H₂ and 67 mW/cm² in C₃H₈. The open-circuit voltage increases from 1.10 V in hydrogen to 1.13 V in propane.

KxCo1.5-0.5xFe(CN)6/rGO with Dual-Active Sodium Ion Storage Site as Superior Anode for Sodium Ion Battery

The unique and open large frame structures of prussian blue analogues (PBA) enables it for accommodating a large number of cations (Na⁺, K⁺, Ca²⁺, etc.), thus, PBA are considered as promising electrode materials for the rechargeable battery. However, due to the chemical composition, there are still many alkaline metal ions in the gap within the framework, which puts multivalent metals in PBA in a low valence state and affects the sodium storage performance. To improve the valence of metal ions in PBA materials, precursors prepared by co-precipitation method and hydrothermal method are used to synthesis K_xCo_1.5-0.5xFe(CN)₆ through further chemical oxidation. Through the introducing of reduced graphene oxide (rGO) with excellent conductivity by a simple physical mixing method, the cycle stability and rate performance of the PBA material can be further improved. The K_0.5Co_1.2Fe(CN)₆·2H₂O/rGO anode prepared with 2 h hydrothermal time and further chemical oxidation, named as KCoHCP-H2-EK/rGO, exhibits a super electrochemical performance, delivering initial charge/discharge capacities of 846.7/1445.0 mAh·g^-1, and a capacity retention of 58.2% after 100 cycles at a current density of 100 mA·g^-1. The KCoHCP-H2-EK/rGO outstanding electrochemical behaviors are attributed to the unique dual-active site structure properties and the improved surface conductance of materials by rGO components.

Effect of Calcination Temperature on the Physicochemical Properties and Electrochemical Performance of FeVO4 as an Anode for Lithium-Ion Batteries

Several electrode materials have been developed to provide high energy density and a long calendar life at a low cost for lithium-ion batteries (LIBs). Iron (III) vanadate (FeVO₄), a semiconductor material that follows insertion/extraction chemistry with a redox reaction and provides high theoretical capacity, is an auspicious choice of anode material for LIBs. The correlation is investigated between calcination temperatures, morphology, particle size, physicochemical properties, and their effect on the electrochemical performance of FeVO₄ under different binders. The crystallite size, particle size, and tap density increase while the specific surface area (S_BET) decreases upon increasing the calcination temperature (500 °C, 600 °C, and 700 °C). The specific capacities are reduced by increasing the calcination temperature and particle size. Furthermore, FeVO₄ fabricated with different binders (35 wt.% PAA and 5 wt.% PVDF) and their electrochemical performance for LIBs was explored regarding the effectiveness of the PAA binder. FV500 (PAA and PVDF) initially delivered higher discharge/charge capacities of 1046.23/771.692 mAhg^-1 and 1051.21/661.849 mAhg^-1 compared to FV600 and FV700 at the current densities of 100 mAg^-1, respectively. The intrinsic defects and presence of oxygen vacancy along with high surface area and smaller particle sizes efficiently enhanced the ionic and electronic conductivities and delivered high discharge/charge capacities for FeVO₄ as an anode for LIBs.

SnS@C nanoparticles anchored on graphene oxide as high-performance anode materials for lithium-ion batteries

Tin (II) sulfide (SnS) has been regarded as an attractive anode material for lithium-ion batteries (LIBs) owing to its high theoretical capacity. However, sulfide undergoes significant volume change during lithiation/delithiation, leading to rapid capacity degradation, which severely hinders its further practical application in lithium-ion batteries. Here, we report a simple and effective method for the synthesis of SnS@C/G composites, where SnS@C nanoparticles are strongly coupled onto the graphene oxide nanosheets through dopamine-derived carbon species. In such a designed architecture, the SnS@C/G composites show various advantages including buffering the volume expansion of Sn, suppressing the coarsening of Sn, and dissolving Li₂S during the cyclic lithiation/delithiation process by graphene oxide and N-doped carbon. As a result, the SnS@C/G composite exhibits outstanding rate performance as an anode material for lithium-ion batteries with a capacity of up to 434 mAh g^-1 at a current density of 5.0 A g^-1 and excellent cycle stability with a capacity retention of 839 mAh g^-1 at 1.0 A g^-1 after 450 cycles.

Polypyrrole-Coated Low-Crystallinity Iron Oxide Grown on Carbon Cloth Enabling Enhanced Electrochemical Supercapacitor Performance

It is highly attractive to design pseudocapacitive metal oxides as anodes for supercapacitors (SCs). However, as they have poor conductivity and lack active sites, they generally exhibit an unsatisfied capacitance under high current density. Herein, polypyrrole-coated low-crystallinity Fe₂O₃ supported on carbon cloth (D-Fe₂O₃@PPy/CC) was prepared by chemical reduction and electrodeposition methods. The low-crystallinity Fe₂O₃ nanorod achieved using a NaBH₄ treatment offered more active sites and enhanced the Faradaic reaction in surface or near-surface regions. The construction of a PPy layer gave more charge storage at the Fe₂O₃/PPy interface, favoring the limitation of the volume effect derived from Na⁺ transfer in the bulk phase. Consequently, D-Fe₂O₃@PPy/CC displayed enhanced capacitance and stability. In 1 M Na₂SO₄, it showed a specific capacitance of 615 mF cm^-2 (640 F g^-1) at 1 mA cm^-2 and still retained 79.3% of its initial capacitance at 10 mA cm^-2 after 5000 cycles. The design of low-crystallinity metal oxides and polymer nanocomposites is expected to be widely applicable for the development of state-of-the-art electrodes, thus opening new avenues for energy storage.

Rationally Tailoring Superstructured Hexahedron Composed of Defective Graphitic Nanosheets and Macropores: Realizing Durable and Fast Potassium Storage

Multipores engineering composed of micro/mesopores is an effective strategy to improve potassium storage performance via providing enormous adsorption sites and shortened ions diffusion distance. However, a detailed exploration of the role played by macropores in potassium storage is still lacking and has been barely reported until now. Herein, a superstructure carbon hexahedron (DGN-900) is synthesized using poly tannic acid (PTA) as precursor. Due to the spatially confined two-step local contraction of PTA along different directions and dimensions during pyrolysis, defective nanosheets with macropores are formed, while realizing a balance between defects content and graphitization degree by regulating temperature. The presence of macropores is conducive to accelerating electrolyte ions rapid infiltration within electrode, and its pore volume can accommodate electrode structure fluctuation upon cycling, while the most suitable ratio of defects to graphitic provides rich ions adsorption sites and sufficient electrons transfer channels, simultaneously. These advantages enable a prominent electrochemical performance in DGN-900 electrode, including high rate (202.9 mAh g^-1 at 2 A g^-1 ) and long cycling stability over 2000 cycles. This unique fabrication strategy, that is, defects engineering coupled with macropores structure, makes fast and durable potassium storage possible.

Sulfur-Doped Carbon for Potassium-Ion Battery Anode: Insight into the Doping and Potassium Storage Mechanism of Sulfur

The sulfur doping strategy has been attracting extensive interest in potassium-ion battery carbon anodes for the dual potential of improving the capacity and kinetics of carbon anodes. Understanding the doping and potassium storage mechanism of sulfur is crucial to guide the structural design and optimization of high-performance sulfur-doped carbon anodes. Herein, presenting a laboratory-synthesized sulfur-doped hard carbon (SHC) with a sulfur content of 6.4 at. % as an example, we clarify the sulfur doping mechanism and reveal the role of sulfur in potassium storage. The high sulfur content of SHC stems from the selective substitution of sulfur for carbon and the residual trace of sulfur molecular fragments after sulfurization. As a result, thanks to the multifaceted roles of doped sulfur in potassium storage, about twice as much capacity, rate capability, and cycling stability is achieved for SHC against S-free hard carbon at the same test conditions. Furthermore, potassium-ion hybrid capacitors assembled based on an SHC anode demonstrate high energy/power density (139 Wh kg^-1/7.3 kW kg^-1), along with an extraordinary cycling stability.

A Lignin-Based Carbon Anode with Long-Cycle Stability for Li-Ion Batteries

Due to its wide source and low cost, biomass-based hard carbon is considered a valuable anode for lithium-ion batteries (LIBs). Lignins, as the second most abundant source in nature, are being intensively studied as candidate anode materials for next generation LIBs. However, direct carbonization of pure lignin usually leads to low specific surface area and porosity. In this paper, we design a porous carbon material from natural lignin assisted by sacrificing a metal-organic framework (MOF) as the template. The MOF nanoparticles can disperse the lignin particles uniformly and form abundant mesopores in the composites to offer fast transfer channels for Li⁺. The as-prepared carbon anode shows a high specific capacity of 420 mAh g^-1 with the capacity retention of 99% after 300 cycles at 0.2 A g^-1. Additionally, it keeps the capacity retention of 85% after long cycle of 1000 cycles, indicating the good application value of the designed anode in LIBs. The work provides a renewable and low-cost candidate anode and a feasible design strategy of the anode materials for LIBs.

Lithium Vanadium Oxide/Graphene Composite as a Promising Anode for Lithium-Ion Batteries

Lithium vanadium oxide (Li₃VO₄, LVO) is a promising anode material for lithium-ion batteries (LIBs) due to its high theoretical capacity (394 mAh g^-1) and safe working potential (0.5-1.0 V vs. Li⁺/Li). However, its electrical conductivity is low which leads to poor electrochemical performance. Graphene (GN) shows excellent electrical conductivity and high specific surface area, holding great promise in improving the electrochemical performance of electrode materials for LIBs. In this paper, LVO was prepared by different methods. SEM results showed the obtained LVO by sol-gel method possesses uniform nanoparticle morphology. Next, LVO/GN composite was synthesized by sol-gel method. The flexible GN could improve the distribution of LVO, forming a high conductive network. Thus, the LVO/GN composite showed outstanding cycling performance and rate performance. The LVO/GN composite can provide a high initial capacity of 350.2 mAh g^-1 at 0.5 C. After 200 cycles, the capacity of LVO/GN composite remains 86.8%. When the current density increased from 0.2 C to 2 C, the capacity of LVO/GN composite only reduced from 360.4 mAh g^-1 to 250.4 mAh g^-1, demonstrating an excellent performance rate.

MgAl Saponite as a Transition-Metal-Free Anode Material for Lithium-Ion Batteries

Transition-metal compounds (oxides, sulfides, hydroxides, etc.) as lithium-ion battery (LIB) anodes usually show extraordinary capacity larger than the theoretical value due to the transformation of LiOH into Li₂O/LiH. However, there has rarely been a report relaying the transformation of LiOH into Li₂O/LiH as the main reaction for LIBs, due to the strong alkalinity of LiOH leading to battery deterioration. In this work, layered silicate MgAl saponite (MA-SAP) is applied as a -OH donor to generate LiOH as the anode material of LIBs for the first time. The MA-SAP maintains a layered structure during the (dis)charging process and has zero-strain characteristic on the (001) crystal plane. In the discharging process, Mg, Al, and Si in the saponite sheets become electron-rich, while the active hydroxyl groups escape from the sheets and combine with lithium ions to form LiOH in the "caves" on sheets, and the LiOH continues to decompose into Li₂O and LiH. Consequently, the MA-SAP delivers a maximum capacity of 536 mA h·g^-1 at 200 mA·g^-1 with a good high-current discharging ability of 155 mA h·g^-1 after 1000 cycles under 1 A·g^-1. Considering its extremely low cost and completely nontoxic characteristics, MA-SAP has great application prospects in energy storage. In addition, this work has an enlightening effect on the development of new anodes based on extraordinary mechanisms.

A Hierarchical SnO2@Ni6MnO8 Composite for High-Capacity Lithium-Ion Batteries

Semiconductor-based composites are potential anodes for Li-ion batteries, owing to their high theoretical capacity and low cost. However, low stability induced by large volumetric change in cycling restricts the applications of such composites. Here, a hierarchical SnO₂@Ni₆MnO₈ composite comprising Ni₆MnO₈ nanoflakes growing on the surface of a three-dimensional (3D) SnO₂ is developed by a hydrothermal synthesis method, achieving good electrochemical performance as a Li-ion battery anode. The composite provides spaces to buffer volume expansion, its hierarchical profile benefits the fast transport of Li⁺ ions and electrons, and the Ni₆MnO₈ coating on SnO₂ improves conductivity. Compared to SnO₂, the Ni₆MnO₈ coating significantly enhances the discharge capacity and stability. The SnO₂@Ni₆MnO₈ anode displays 1030 mAh g^-1 at 0.1 A g^-1 and exhibits 800 mAh g^-1 under 0.5 A g^-1, along with high Coulombic efficiency of 95%. Furthermore, stable rate performance can be achieved, indicating promising applications.

Reduced Graphene Oxide-Wrapped Novel CoIn2S4 Spinel Composite Anode Materials for Li-ion Batteries

In this study, we proposed a novel CoIn₂S₄/reduced graphene oxide (CoIn₂S₄/rGO) composite anode using a hydrothermal method. By introducing electronic-conductive reduced graphene oxide (rGO) to buffer the extreme volume expansion of CoIn₂S₄, we prevented its polysulfide dissolution during the lithiation/de-lithiation processes. After 100 cycles, the pristine CoIn₂S₄ electrode demonstrated poor cycle performance of only 120 mAh/g at a current density of 0.1 A/g. However, the composition-optimized CoIn₂S₄/rGO composite anode demonstrated a reversible capacity of 580 mAh/g for 100 cycles, which was an improvement of 4.83 times. In addition, the ex situ XRD measurements of the CoIn₂S₄/rGO electrode were conducted to determine the reaction mechanism and electrochemical behavior. These results suggest that the as-synthesized CoIn₂S₄/rGO composite anode is a promising anode material for lithium ion batteries.

High Performance and Long-cycle Life Rechargeable Aluminum Ion Battery: Recent Progress, Perspectives and Challenges

The rising energy crisis and environmental concerns caused by fossil fuels have accelerated the deployment of renewable and sustainable energy sources and storage systems. As a result of immense progress in the field, cost-effective, high-performance, and long-life rechargeable batteries are imperative to meet the current and future demands for sustainable energy sources. Currently, lithium-ion batteries are widely used, but limited lithium (Li) resources have caused price spikes, threatening progress toward cleaner energy sources. Therefore, post-Li, batteries that utilize highly abundant materials leading to cost-effective energy storage solutions while offering desirable performance characteristics are urgently needed. Aluminum-ion battery (AIB) is an attractive concept that uses highly abundant aluminum while offering a high theoretical gravimetric and volumetric capacity of 2980 mAh g^-1 and 8046 mAh cm^-3 , respectively. As a result, intensified efforts have been made in recent years to utilize numerous electrolytes, anodes, and cathode materials to improve the electrochemical performance of AIBs, and potentially create high-performance, low-cost, and safe energy storage devices. Herein, recent progress in the electrolyte, anode, and cathode active materials and their utilization in AIBs and their related characteristics are summarized. Finally, the main challenges facing AIBs along with future directions are highlighted.

Understanding the Capacity Decay of Si/NMC622 Li-Ion Batteries Cycled in Superconcentrated Ionic Liquid Electrolytes: A New Perspective

Silicon-containing Li-ion batteries have been the focus of many energy storage research efforts because of the promise of high energy density. Depending on the system, silicon generally demonstrates stable performance in half-cells, which is often attributed to the unlimited lithium supply from the lithium (Li) metal counter electrode. Here, the electrochemical performance of silicon with a high voltage NMC622 cathode was investigated in superconcentrated phosphonium-based ionic liquid (IL) electrolytes. As a matter of fact, there is very limited work and understanding of the full cell cycling of silicon in such a new class of electrolytes. The electrochemical behavior of silicon in the various IL electrolytes shows a gradual and steeper capacity decay, compared to what we previously reported in half-cells. This behavior is linked to a different evolution of the silicon morphology upon cycling, and the characterization of cycled electrodes points toward mechanical reasons, complete disconnection of part of the electrode, or internal mechanical stress, due to silicon and Li metal volume variation upon cycling, to explain the progressive capacity fading in full cell configuration. An extremely stable solid electrolyte interphase (SEI) in the full Li-ion cells can be seen from a combination of qualitative and quantitative information from transmission electron microscopy, X-ray photoelectron spectroscopy, electrochemical impedance spectroscopy, and magic angle spinning nuclear magnetic resonance. Our findings provide a new perspective to full cell interpretation regarding capacity fading, which is oftentimes linked almost exclusively to the loss of Li inventory but also more broadly, and provide new insights into the impact of the evolution of silicon morphology on the electrochemical behavior.

Operando X-ray Studies of Ni-Containing Heteropolyvanadate Electrode for High-Energy Lithium-Ion Storage Applications

Ni-containing heteropolyvanadate, Na₆[NiV₁₄O₄₀], was synthesized for the first time to be applied in high-energy lithium storage applications as a negative electrode material. Na₆[NiV₁₄O₄₀] can be prepared via a facile solution process that is suitable for low-cost mass production. The as-prepared electrode provided a high capacity of approximately 700 mAh g^-1 without degradation for 400 cycles, indicating excellent cycling stability. The mechanism of charge storage was investigated using operando X-ray absorption spectroscopy (XAS), X-ray diffraction (XRD), transition X-ray microscopy (TXM), and density functional theory (DFT) calculations. The results showed that V⁵⁺ was reduced to V²⁺ during lithiation, indicating that Na₆[NiV₁₄O₄₀] is an insertion-type material. In addition, Na₆[NiV₁₄O₄₀] maintained its amorphous structure with negligible volume expansion/contraction during cycling. Employed as the negative electrode in a lithium-ion battery (LIB), the Na₆[NiV₁₄O₄₀]//LiFePO₄ full cell had a high energy density of 300 W h kg^-1. When applied in a lithium-ion capacitor, the Na₆[NiV₁₄O₄₀]//expanded mesocarbon microbead full cell displayed energy densities of 218.5 and 47.9 W h kg^-1 at power densities of 175.7 and 7774.2 W kg^-1, respectively. These findings reveal that the negative electrode material Na₆[NiV₁₄O₄₀] is a promising candidate for Li-ion storage applications.

α-graphyne as a promising anode material for Na-ion batteries: a first-principles study

Lithium-ion batteries (LIBs) have emerged as a technological game-changer. Due to the rising price of lithium and the environmental concerns LIBs pose, their use is no longer viable. Sodium (Na) may be the best contender among the alternatives for replacing lithium. Conventional graphite has a limited capacity for Na storage. Hence,α-graphyne, an allotrope of carbon, was studied here as a potential anode material for Na-ion batteries (NIBs), employing density functional theory. In-plane Na atom adsorption results in a semi-metallic to metallic transition ofα-graphyne. Electronic transport calculations show an increase in current after Na adsorption in graphyne. The successive adsorption of Na atoms on the surface of graphyne leads to a theoretical capacity of 1395.89 mA h g^-1, which is much greater than graphite. The average open circuit voltage is 0.81 V, which is an ideal operating voltage for NIBs. Intra- and inter-hexagon Na diffusions have very low energy barriers of 0.18 eV and 0.96 eV, respectively, which ensure smooth operation during charge/discharge cycles. According to this study, theα-graphyne monolayer thus has the potential to be employed as an anode in NIBs.