Controlled Synthesis of SnO2 Nanostructures as Alloy Anode via Restricted Potential Toward Building High-Performance Dual-Ion Batteries with Graphite Cathode.

Dual-ion batteries (DIBs) are considered one of the promising energy storage devices in which graphite serves as a bi-functional electrode, i.e., anode and cathode in the aprotic organic solvents. Unlike conventional lithium-ion batteries (LIBs), DIBs reversibly store the cations and anions in the anode and cathodes during redox reactions, respectively. The electrolyte is a source for both cations and anions, so the choice of electrolyte plays a vital role. In the present work, the synthesis of SnO2 nanostructures is reported as a possible alternative for graphite anode, and the Li-storage performance is optimized in half-cell (Li/SnO2 ) assembly with varying amounts of conductive additive (acetylene black) and limited working potential (1 V vs Li). Finally, a DIB using recovered graphite (RG) fabricated from spent LIB as a cathode and SnO2 nanostructures as an anode under balanced loading conditions. Prior to the fabrication, both electrodes are pre-cycled to eliminate irreversibility. An in-situ impedance study has been employed to validate the passivation layer formation during the charge-discharge process. The high-performance SnO2 /RG-based DIB delivered a maximum discharge capacity of 380 mAh g-1 . The electrochemical performance of DIB has been assessed by varying temperature conditions to evaluate their suitability in different climatic conditions.

Boosting Thermal and Mechanical Properties: Achieving High-Safety Separator Chemically Bonded with Nano TiN Particles for High Performance Lithium-Ion Batteries.

Currently, the commercial separator (Celgard2500) of lithium-ion batteries (LIBs) suffers from poor electrolyte affinity, mechanical property and thermal stability, which seriously affect the electrochemical performances and safety of LIBs. Here, the composite separators named PVDF-HFP/TiN for high-safety LIBs are synthesized. The integration of PVDF-HFP and TiN forms porous structure with a uniform and rich organic framework. TiN significantly improves the adsorption between PVDF-HFP and electrolyte, causing a higher electrolyte absorption rate (192%). Meanwhile, XPS results further demonstrate the tight link between PVDF-HFP and TiN due to the existence of TiF bond in PVDF-HFP/TiN, resulting in a strong impediment for the puncture of lithium dendrites as a result of the improved mechanical strengths. And PVDF-HFP/TiN can effectively suppress the growth of lithium dendrites by means of uniform lithium flux. In addition, the excellent heat resistance of TiN improves the thermal stability of PVDF-HFP/TiN. As a result, the LiFePO4 ||Li cells assembled PVDF-HFP/TiN-12 exhibit excellent specific capacity, rate performance, and capacity retention rate. Even the high specific capacity of 153 mAh g-1 can be obtained at the high temperature of 80 °C. Meaningfully, a reliable modification strategy for the preparation of separators with high safety and electrochemical performance in LIBs is provided.

Carbonized Polymer Dots for Controlling Construction of MoS2 Flower-Like Nanospheres to Achieve High-Performance Li/Na Storage Devices.

Despite being one of the most promising materials in anode materials, molybdenum sulfide (MoS2 ) encounters certain obstacles, such as inadequate cycle stability, low conductivity, and unsatisfactory charge-discharge (CD) rate performance. In this study, a novel approach is employed to address the drawbacks of MoS2 . Carbon polymer dots (CPDs) are incorporated to prepare three-dimensional (3D) nanoflower-like spheres of MoS2 @CPDs through the self-assembly of MoS2 2D nanosheets, followed by annealing at 700 °C. The CPDs play a main role in the creation of the nanoflower-like spheres and also mitigate the MoS2 nanosheet limitations. The nanoflower-like spheres minimize volume changes during cycling and improve the rate performance, leading to exceptional rate performance and cycling stability in both Lithium-ion and Sodium-ion batteries (LIBs and SIBs). The optimized MoS2 @CPDs-2 electrode achieves a superb capacity of 583.4 mA h g-1 at high current density (5 A g-1 ) after 1000 cycles in LIBs, and the capacity remaining of 302.8 mA h g-1 after 500 cycles at 5 A g-1 in SIBs. Additionally, the full cell of LIBs/SIBs exhibits high capacity and good cycling stability, demonstrating its potential for practical application in fast-charging and high-energy storage.

Effect of intercalated molybdenum atoms on structure and electrochemical properties of Mo1+xS2synthesized by hydrothermal method.

As an alternative anode to graphene, molybdenum disulfide (MoS2) has attracted much attention due to its layered structure and high specific capacity. Moreover, MoS2can be synthesized by hydrothermal method with low cost and the size of its layer spacing can be controlled. In this work, the results of experiment and calculation proved that the presence of intercalated Mo atoms, leading to the expansion of MoS2layer spacing and weakening of Mo-S bonding. For the electrochemical properties, the presence of intercalated Mo atoms causes the lower reduction potentials for the Li+intercalation and Li2S formation. In addition, the effective reduction of diffusion resistance and charge transfer resistance in Mo1+xS2leads to the acquisition of high specific capacity for battery applications.

Improved lithium-ion battery performance by introducing oxygen-containing functional groups by plasma treatment.

Metal sulfides are often used as cathode materials for lithium-ion batteries (LIBs) owing to their high theoretical specific capacity; however, excessively fast capacity decay during charging/discharging and rapid shedding during cycling limits their practical application in batteries. In this study, we proposed a strategy using plasma treatment combined with the solvothermal method to prepare cobalt sulfide (Co1-xS)-carbon nanofibers (CNFs) composite. The plasma treatment could introduce oxygen-containing polar groups and defects, which could improve the hydrophilicity of the CNFs for the growth of the Co1-xS, thereby increasing the specific capacity of the composite electrode. The results show that the composite electrode present a high discharge specific capacity (839 mAh g-1at a current density of 100 mA g-1) and good cycle stability (the capacity retention rate almost 100% at 2000 mA g-1after 500 cycles), attributing to the high conductivity of the CNFs. This study proves the application of plasma treatment and simple vulcanization method in high-performance LIBs.

Simplified Synthesis of Biomass-Derived Si/C Composites as Stable Anode Materials for Lithium-Ion Batteries.

Synthesis of silicon/carbon (Si/C) composites from biomass resources could enable the effective utilization of agricultural products in the battery industry with economical as well as environmental benefits. Herein, a simplified process was developed to synthesize Si/C from biomass, by using a low-cost agricultural byproduct "rice husk (RH)" as a model. This process includes the calcination of RH for SiO2 /C and the reduction of SiO2 /C by Al in molten salts at a moderate temperature. This process does not need the removal of carbon before thermal reduction of SiO2 , which is thought to be necessary to avoid the formation of SiC at elevated temperatures. Thus, carbon derived from biomass can be directly used for Si/C composites for anode materials. The resultant Si/C shows a high reversible capacity of 1309 mAh g-1 and long cycle life (300 cycles). This research advocates a new and simplified strategy for the synthesis of RH-based biomass-derived Si/C, which is beneficial for low-cost, environmentally friendly, and green energy storage applications.

S-Doped Carbon Fibers Uniformly Embedded with Ultrasmall TiO2 for Na+ /Li+ Storage with High Capacity and Long-Time Stability.

Building a rechargeable battery with high capacity, high energy density, and long lifetime contributes to the development of novel energy storage devices in the future. Although carbon materials are very attractive anode materials for lithium-ion batteries (LIBs), they present several deficiencies when used in sodium-ion batteries (SIBs). The choice of an appropriate structural design and heteroatom doping are critical steps to improve the capacity and stability. Here, carbon-based nanofibers are produced by sulfur doping and via the introduction of ultrasmall TiO2 nanoparticles into the carbon fibers (CNF-S@TiO2 ). It is discovered that the introduction of TiO2 into carbon nanofibers can significantly improve the specific surface area and microporous volume for carbon materials. The TiO2 content is controlled to obtain CNF-S@TiO2 -5 to use as the anode material for SIBs/LIBs with enhanced electrochemical performance in Na+ /Li+ storage. During the charge/discharge process, the S-doping and the incorporation of TiO2 nanoparticles into carbon fibers promote the insertion/extraction of the ions and enhance the capacity and cycle life. The capacity of CNF-S@TiO2 -5 can be maintained at ≈300 mAh g-1 over 600 cycles at 2 A g-1 in SIBs. Moreover, the capacity retention of such devices is 94%, showing high capacity and good stability.

Metal-Organic Frameworks-Derived Mesoporous Si/SiOx @NC Nanospheres as a Long-Lifespan Anode Material for Lithium-Ion Batteries.

Silicon (Si)-based anode materials with suitable engineered nanostructures generally have improved lithium storage capabilities, which provide great promise for the electrochemical performance in lithium-ion batteries (LIBs). Herein, a metal-organic framework (MOF)-derived unique core-shell Si/SiOx @NC structure has been synthesized by a facile magnesio-thermic reduction, in which the Si and SiOx matrix were encapsulated by nitrogen (N)-doped carbon. Importantly, the well-designed nanostructure has enough space to accommodate the volume change during the lithiation/delithiation process. The conductive porous N-doped carbon was optimized through direct carbonization and reduction of SiO2 into Si/SiOx simultaneously. Benefiting from the core-shell structure, the synthesized product exhibited enhanced electrochemical performance as an anode material in LIBs. Particularly, the Si/SiOx @NC-650 anode showed the best reversible capacities up to 724 and 702 mAh g-1 even after 100 cycles. The excellent cycling stability of Si/SiOx @NC-650 may be attributed to the core-shell structure as well as the synergistic effect between the Si/SiOx and MOF-derived N-doped carbon.

Low-Temperature Molten Salt Electrochemical CO2 Upcycling for Advanced Energy Materials.

One strategy for addressing the climate crisis caused by CO2 emissions is to efficiently convert CO2 to advanced materials suited for green and clean energy technology applications. Porous carbon is widely used as an advanced energy storage material because of its enhanced energy storage capabilities as an anode. Herein, we report electrochemical CO2 upcycling to solid carbon with a controlled microstructure and porosity in a ternary molten carbonate melt at 450 °C. Controlling the electrochemical parameters (voltage, temperature, cathode material) enabled the conversion of CO2 to porous carbon with a tunable morphology and porosity for the first time at such a low temperature. Additionally, a well-controlled morphology and porosity are beneficial for reversible energy storage. In fact, these carbon materials delivered high specific capacity, stable cycling performances, and exceptional rate capability even under extremely fast charging conditions when integrated as an anode in lithium-ion batteries (LIBs). The present approach not only demonstrated efficient upcycling of CO2 into porous carbon suitable for enhanced energy storage but can also contribute to a clean and green energy technology that can reduce carbon emissions to achieve sustainable energy goals.

In-situ Formation of a LiF-rich Interphase for Graphite Anode Operated at Low Temperatures.

Inorganic LiF is generally a desirable component in solid electrolyte interface (SEI) for graphite anode due to its electronic insulation, low Li+ diffusion barrier, high modulus and good chemical stability. Herein, fluorinated carbon (CFx) was incorporated into graphite material, which exhibited a high discharge potential prior to electrolyte decomposition and in-situ formed a crystalline LiF-based SEI with improved Li+ diffusion rate. The optimized graphite anode therefore demonstrated a fast-charging capability with 124 mAh g-1 at high rate of 8 C and a remarkable capacity retention of 83.8% at the low temperature of -30 oC compared to that at 25 oC. Furthermore, the optimized graphite|LiFePO4 full cell exhibited a significantly high discharge capacity of 109 mAh g-1 at -30 oC, corresponding to a notable 77.3% room-temperature capacity retention. These findings highlight a facile strategy to attain a LiF-rich SEI for high-performance lithium-ion batteries.

Application and Development of Silicon Anode Binders for Lithium-Ion Batteries.

The use of silicon (Si) as a lithium-ion battery's (LIBs) anode active material has been a popular subject of research, due to its high theoretical specific capacity (4200 mAh g-1). However, the volume of Si undergoes a huge expansion (300%) during the charging and discharging process of the battery, resulting in the destruction of the anode's structure and the rapid decay of the battery's energy density, which limits the practical application of Si as the anode active material. Lithium-ion batteries' capacity, lifespan, and safety can be increased through the efficient mitigation of Si volume expansion and the maintenance of the stability of the electrode's structure with the employment of polymer binders. The main degradation mechanism of Si-based anodes and the methods that have been reported to effectively solve the Si volume expansion problem firstly are introduced. Then, the review demonstrates the representative research work on the design and development of new Si-based anode binders to improve the cycling stability of Si-based anode structure from the perspective of binders, and finally concludes by summarizing and outlining the progress of this research direction.

Structure regulated 3D flower-like lignin-based anode material for lithium-ion batteries and its storage kinetics.

As a green sustainable material, lignin-derived porous carbon (LPC) exhibits great application potential when used as the anode material in lithium-ion batteries (LIBs), but the applications are limited by the heterogeneity of the lignin precursor. Therefore, it is crucial to reveal the relationship among lignin properties, porous carbon structure and the kinetics of lithium-ion storage. Herein, LPCs from fractionated lignin have been prepared by an eco-friendly and recyclable activator. The structure of the LPCs was regulated by adjusting the molecular weight, linkage abundance and glass transition temperature (Tg) of lignin macromolecules. As the anode material of LIBs, the prepared 3D flower-like LPCE70 could achieve a reversible capacity of 528 mAh g-1 at a current density of 0.2 A g-1 after 200 cycles, 63 % higher than that of commercial graphite. Furthermore, kinetic calculations of lithium-ion storage behavior of LPCs were firstly used to confirm the contribution ratio of diffusion-controlled behavior and capacitive effect. Lignin with a high linkage abundance could yield LPCE70 with the largest interlayer spacing and specific surface area to maximize lithium-ion storage from both diffusion-controlled and capacitive contributions of specific capacities. This work provides a green, facile and effective pathway for value-added utilization of lignin in LIBs.

Carbon-Free Conversion of SiO2 to Si via Ultra-Rapid Alloy Formation: Toward the Sustainable Fabrication of Nanoporous Si for Lithium-Ion Batteries.

Silicon has the potential to improve lithium-ion battery (LIB) performance substantially by replacing graphite as an anode. The sustainability of such a transformation, however, depends on the source of silicon and the nature of the manufacturing process. Today's silicon industry still overwhelmingly depends on the energy-intensive, high-temperature carbothermal reduction of silica─a process that adversely impacts the environment. Rather than use conventional thermoreduction alone to break Si-O bonds, we report the efficient conversion of SiO2 directly to Mg2Si by a microwave-induced Mg plasma within 2.5 min at merely 200 W under vacuum. The underlying mechanism is proposed, wherein electrons with enhanced kinetics function readily as the reductant while the "bombardment" from Mg cations and electrons promotes the fast nucleation of Mg2Si. The 3D nanoporous (NP) Si is then fabricated by a facile thermal dealloying step. The resulting hierarchical NP Si anodes deliver stable, extended cycling with excellent rate capability in Li-ion half-cells, with capacities several times greater than graphite. The microwave-induced metal plasma (MIMP) concept can be applied just as efficiently to the synthesis of Mg2Si from Si, and the chemistry should be extendable to the reduction of multiple metal(loid) oxides via their respective Mg alloys.

Polynitrosoarene Radical as an Efficient Cathode Material for Lithium-Ion Batteries.

Organic radical batteries (ORBs) with radical-branched polymers as cathode materials represent a valuable alternative to meet the continuously increasing demand on energy storage. However, the low theoretical capacities of current radical-contained compounds strongly hamper their practical applications. To address this issue, a chemically robust polynitrosoarene (tris(4-nitrosophenyl)amine) with a pronounced radical property is rationally designed as an efficient cathode for ORBs. Its unique multi-nitroso structure displays remarkably reversible charge/discharge capability and a superior capacity up to 300 mA h g-1 (93% theoretical capacity) after 100 cycles at 100 mA g-1 within a broad potential window of 1.3-4.3 V (vs Li+/Li). Moreover, the ultra-long cycle life is also achieved at 1000 mA g-1 with 85% preservation of the capacity after 1000 cycles, making it the best-reported organic radical cathode material for lithium-ion batteries.

Hierarchical porous Co-CoO@NC hollow microspheres with capacity growth by reactivation of solid-electrolyte interface films.

Transition metal oxide (TMO)-based electrodes exhibit increased capacities, yet the mechanism behind the true cause of capacity in such materials remains unclear. Herein, hierarchical porous and hollow Co-CoO@NC spheres assembled by nanorods with refined nanoparticles and amorphous carbon have been synthesized by a two-step annealing approach. A temperature gradient-driven mechanism is revealed for the evolution of the hollow structure. Compared with the solid CoO@NC spheres, the novel hierarchical of Co-CoO@NC can fully utilize the interior active material by exposing both ends of each nanorod into electrolyte. The hollow interior provides extra space for the volume variation, leading to an up-trend capacity of 919.3 mAh g-1 at 200 mA g-1 over 200 cycles. Differential capacity curves disclose that solid electrolyte interface (SEI) films reactivation partly contributes to increasing reversible capacity. The introduction of nanosized Co particles benefits the process by participating in the transformation of SEI components. This study provides a guide for constructing anodic material with exceptional electrochemical performance.

Enhanced microstructure stability of LiNi0.8Co0.1Mn0.1O2 cathode with negative thermal expansion shell for long-life battery.

With high specific energy density, Ni-rich layered LiNi0.8Co0.1Mn0.1O2 (NCM) material has become one promising cathode candidate for advanced lithium-ion batteries (LIBs). However, severe capacity fading induced by microstructure degradation and deteriorated interfacial Li+ transportation upon repeated cycling makes the commercial application of NCM cathode in dilemma. To address these issues, LiAlSiO4 (LASO), one unique negative thermal expansion (NTE) composite with high ionic conductivity, is utilized as a coating layer to improve the electrochemical performances of NCM material. Various characterizations demonstrate that LASO modification can endow NCM cathode with significantly enhanced long-term cyclability, through reinforcing the reversibility of phase transition and restraining lattice expansion, as well as depressing microcrack generation during repeated delithiation-lithiation processes. The electrochemical results indicate that LASO-modified NCM cathode can deliver an excellent rate capability of 136 mAh g-1 at a high current rate of 10 C (1800 mA g-1), larger than that of the pristine cathode (118 mAh g-1), especially higher capacity retention of 85.4% concerning the pristine NCM cathode (65.7%) over 500 cycles under 0.2 C. This work provides a feasible strategy to ameliorate the interfacial Li+ diffusion and suppress the microstructure degradation of NCM material during long-term cycling, which can effectively promote the practical application of Ni-rich cathode in high-performance LIBs.

Thermal Expansion Neutralization Enhancing the Cycling Stability of Ni-Rich LiNi0.6Co0.2Mn0.2O2 Cathode Material.

As promising cathode candidates with advantageous capacity and price superiority for lithium-ion batteries, Ni-rich materials are severely impeded in the practical application due to their poor microstructural stability induced by the intrinsic Li+/Ni2+ cation mixing and mechanical stress accumulation upon cycling. In this work, a synergetic approach is demonstrated to improve the microstructural and thermal stabilities of Ni-rich LiNi0.6Co0.2Mn0.2O2 (NCM622) cathode material through taking advantage of the thermal expansion offset effect of the LiZr2(PO4)3 (LZPO) modification layer. The optimized NCM622@LZPO cathode exhibits a significantly enhanced cyclability with a capacity retention of 67.7% after 500 cycles at 0.2 C and delivers a specific capacity of 115 mAh g-1 with a capacity retention of 64.2% after 300 cycles under 55 °C. Exploiting the chemical environment analysis of the Ni element detected by the synchrotron radiation technique, it is found that the mixing degree of Li+/Ni2+ cations in the bulk Ni-rich material can be effectively depressed through interfacial Zr4+ doping during the preparation of the LZPO-modified material. Additionally, time- and temperature-dependent powder diffraction spectra were collected to monitor the structure evolutions of pristine NCM622 and NCM622@LZPO cathodes in the initial cycles and under various temperatures, revealing the contribution of negative thermal expansion LZPO coating in promoting microstructural stability of the bulk NCM622 cathode. The introduction of NTE functional compounds might provide a universal strategy to address the stress accumulation and volume expansion issues of various cathode materials for advanced secondary-ion batteries.

Enhancing the Electrochemical Stability of LiNi0.8Co0.1Mn0.1O2 Compounds for Lithium-Ion Batteries via Tailoring Precursors Synthesis Temperatures.

LiNi0.8Co0.1Mn0.1O2 (LNCMO) cathode materials for lithium-ion batteries (LIBs) were prepared by the hydrothermal synthesis of precursors and high-temperature calcination. The effect of precursor hydrothermal synthesis temperature on the microstructures and electrochemical cycling performances of the Ni-rich LNCMO cathode materials were investigated by SEM, XRD, XPS and electrochemical tests. The results showed that the cathode material prepared using the precursor synthesized at a hydrothermal temperature of 220 °C exhibited the best charge/discharge cycle stability, whose specific capacity retention rate reached 81.94% after 50 cycles. Such enhanced cyclic stability of LNCMO was directly related to the small grain size, high crystallinity and structural stability inherited from the precursor obtained at 220 °C.

Synergistic dual electrolyte additives for fluoride rich solid-electrolyte interface on Li metal anode surface: Mechanistic understanding of electrolyte decomposition.

Improving the quality of the solid-electrolyte interphase (SEI) layer is highly imperative to stabilize the Li-metal anodes for the practical application of high-energy-density batteries. However, controllably managing the formation of robust SEI layers on the anode is challenging in state-of-the-art electrolytes. Herein, we discuss the role of dual additives fluoroethylene carbonate (FEC) and lithium difluorophosphate (LiPO2F2, LiPF) within the commercial electrolyte mixture (LiPF6/EC/DEC) considering their reactivity with Li metal anodes using density functional theory (DFT) and ab initio molecular dynamics (AIMD) simulations. Synergistic effects of dual additives on SEI formation mechanisms are explored systematically by invoking different electrolyte mixtures including pure electrolyte (LP47), mono-additive (LP47/FEC and LP47/LiPF), and dual additives (LP47/FEC/LiPF). The present work suggests that the addition of dual additives accelerates the reduction of salt and additives while increasing the formation of a LiF-rich SEI layer. In addition, calculated atomic charges are applied to predict the representative F1s X-ray photoelectron (XPS) signal, and our results agree well with the experimentally identified SEI components. The nature of carbon and oxygen-containing groups resulting from the electrolyte decompositions at the anode surface is also analyzed. We find that the presence of dual additives inhibits undesirable solvent degradation in the respective mixtures, which effectively restricts the hazardous side products at the electrolyte-anode interface and improves SEI layer quality.

Application of Thermally Fluorinated Multi-Wall Carbon Nanotubes as an Additive to an Li4Ti5O12 Lithium Ion Battery.

In this study, multi-walled carbon nanotubes (MWCNTs) were modified by thermal fluorination to improve dispersibility between MWCNTs and Li4Ti5O12 (LTO) and were used as additives to compensate for the disadvantages of LTO anode materials with low electronic conductivity. The degree of fluorination of the MWCNTs was controlled by modifying the reaction time at constant fluorination temperature; the clear structure and surface functional group changes in the MWCNTs due to the degree of fluorination were determined. In addition, the homogeneous dispersion in the LTO was improved due to the strong electronegativity of fluorine. The F-MWCNT conductive additive was shown to exhibit an excellent electrochemical performance as an anode for lithium ion batteries (LIBs). In particular, the optimized LTO with added fluorinated MWCNTs not only exhibited a high specific capacity of 104.8 mAh g-1 at 15.0 C but also maintained a capacity of ~116.8 mAh g-1 at a high rate of 10.0 C, showing a capacity almost 1.4 times higher than that of LTO with the addition of pristine MWCNTs and an improvement in the electrical conductivity. These results can be ascribed to the fact that the semi-ionic C-F bond of the fluorinated MWCNTs reacts with the Li metal during the charge/discharge process to form LiF, and the fluorinated MWCNTs are converted into MWCNTs to increase the conductivity due to the bridge effect of the conductive additive, carbon black, with LTO.