Improved Cycling Performance Research Articles

Enhanced Cycle Performance of NiCo2O4/CNTs Composites in Lithium-Air Batteries

The lithium-air battery is a new type of secondary battery technology that is currently receiving a lot of attention in the field of power storage technology. These batteries are known to offer high energy densities and potentially longer driving ranges. In this study, NiCo2O4 and CNTs were used to create a composite for use as the cathode of a Li-air battery. Improving the 3D needl-like structure that provides extensive transport channels for electrolyte infiltration and numerous sites facilitated charge transfer reactions and the synergistic effect of highly electrocatalytic NiCo2O4 with pronounced activity and high conductive CNTs, with the synthesized NiCo2O4@CNTs composites exhibiting active catalytic performance for both OER and ORR reactions. It also showed improved cycle performance at high current densities. NiCo2O4@CNTs composites were successfully fabricated using a hydrothermal method together with a sequential annealing treatment. The components of the completed composite were confirmed using TGA, XRD, and SEM, and the specific surface area was analyzed using BET. The composite was performed for over 120 cycles at a current density of 200 mA∙g−1, and 500 mA∙g−1 was achieved under the capacity limiting condition of 500 mAh∙g−1. The charging/discharging characteristics were compared under various current densities, exhibiting stable cyclability. The high catalytic activity of NiCo2O4 oxide supports its potential use as a cathode in Li-air batteries.

Enabling high performance all-solid-state thin films microbatteries with silicon oxycarbide/lithium-metal composites anodes

All-solid-state thin films micro-batteries (ASSTFBs) integrating thin-films technologies with solid-electrolytes are regarded as promising power sources that can inherently alleviate safety issues for the miniaturized devices for internet of things (IoT). However, poor interfacial compatibility and low ionic conductivity induced by using of solid-state electrolytes urgently demand new development of novel materials and preparation technologies. In this work, novel silicon oxycarbide/lithium-metal composites anodes for ASSTFBs of IoT micro-devices are prepared by magnetron sputtering, and the electrochemical performances are systematically investigated via experiments and first-principles. The thin films batteries systems present high first cycle discharge capacities up to 104.15 mAh/g. The sample with the highest carbon content of SiCO shows superior coulomb efficiency of 97 % after 40 cycles and retention rates of 73.29 % at 0.1 C, and sample with the optimal feature size of free carbon presents the most outstanding comprehensive electrochemical properties. First-principles calculations reveal that the optimal LiPON/SiCO interface presents the highest adhesion strength and superior lithium diffusion properties with the lowest energy barrier for lithium diffusion. The relatively larger free carbon network limit volume expansion upon insertion of lithium, and silicon tetrahedral in SiCO show large lithium storage density, leads to improved cycling performance and high lithium capacity of the system.

Improving Cycling Performance of Anode-Free Lithium Batteries by Pressure and Voltage Control

Improving Cycling Performance of Anode-Free Lithium Batteries by Pressure and Voltage Control

Lithium Bis(fluorosulfonyl)imide for Stabilized Interphases on Conjugated Dicarboxylate Electrode.

Carbonyl-based negative electrodes have received considerable interest in the domain of rechargeable lithium batteries, owing to their superior feasibility in structural design, enhanced energy density, and good environmental sustainability. Among which, lithium terephthalate (LiTPA) has been intensively investigated as a negative electrode material in the past years, in light of its relatively stable discharge plateau at low potentials (ca. 1.0 V vs Li/Li+) and high specific capacity (ca. 290 mAh g-1). However, its cell performances are severely limited owing to the poor quality of the solid-electrolyte-interphase (SEI) layer generated therein. Here, we report the utilization of lithium bis(fluorosulfonyl)imide (LiFSI) as an electrolyte salt for forming a Li-ion permeable SEI layer on the LiTPA electrode and subsequently improving the cyclability and rate performance of the LiTPA-based cells. Our results show that, differing from the reference electrolyte containing the lithium hexafluorophosphate (LiPF6) salt, the electrochemical reductions of the FSI- anions occur prior to the lithiation processes of LiTPA electrode, which is capable of building an inorganic-rich SEI layer containing lithium fluoride (LiF) and lithium sulfate (Li2SO4). Consequently, the lithium metal (Li°)||LiTPA cell shows significantly improved cycling performance than the LiPF6-based reference cell. This work provides useful insight into the reductive processes of the FSI- anions on negative electrodes, which could spur the deployment of highly sustainable and high-energy rechargeable lithium batteries.

High-pressure and high-temperature synthesis of black phosphorus-graphite anode material for lithium-ion batteries

Phosphorus-based materials with a high theoretical specific capacity and a fast charge-discharge rate are considered as promising anode materials for high energy density lithium-ion batteries (LIBs). Red phosphorus (RP) and black phosphorus (BP) are two main allotropes to be used as anode materials. However, huge volume expansion during charge-discharge processes hinders the application of RP and BP in LIBs. Composites of phosphorus and carbon-based materials have been extensively fabricated to withstand volume expansion of phosphorus and improve cycle performance. Here, composites of BP and graphite (BP-G) with three P-G mass ratios (8 : 2, 7 : 3, and 6 : 4) have been synthesized by a facile and scalable high-pressure and high-temperature (HPHT) method using RP and graphite composites (RP-G) prepared by ball milling as precursors. Their microstructure and bonding configurations have been analyzed by various characterization techniques. Among three RP-G composites, 7RP-3G exhibits the most excellent cycling stability, a high reversible capacity of 1331 mAh/g after 200 cycles at a current density of 0.78 A/g. However, RP-G composites show poor stability at high current densities. Among three BP-G composites, 6BP-4G shows the best cycle stability at high current densities, a reversible capacity of 634.6 mAh/g after 500 cycles at a current density of 2.6 A/g. Although, the reversible specific capacities of BP-G composites after long cycles are lower than those of RP-G, BP-G composites show more stable cycle performance than RP-G, especially at high current densities. The present work illustrates a direct and facile method to synthesize BP-G composites, and sheds light to explore new synthetic route of BP-based composites.

Effect of Al-doping on structural and cyclic stability of NiCoFe layered double hydroxides as electrode material in supercapacitors

Supercapacitors are an effective energy storage device can address the issue of storing renewable energy sources. Layered double hydroxides (LDHs) have been identified as a promising electrode material for supercapacitors due to their diverse constituent elements and adjustable structure. However, LDHs tend to experience mechanical deformation during charging and discharging, which results in poor cycle performance. In this study, an Al substitution strategy for Fe was employed to adjust the interlaced structure assembled by one-dimensional nanorods and two-dimensional nanosheets in NiCoFe-LDH, which led to an enhanced stability and electrochemical performance for supercapacitors. Excessive Al doping prompted nanorods to evolve into nanosheets, resulting in loss of the interlaced structure. When the ratio of Fe and Al is 0.75:0.25, the resulted Ni2Co1Fe0.75Al0.25-LDH maintained a much more perfect interlaced structure while exhibiting the best specific capacitance reaching 2367.39 F·g−1 at 1 A·g−1 as well as a 89.79% retention rate at 20 A·g−1 in a three-electrode unit; when paired with activated carbon (AC), it exhibited a specific capacitance of 394.14 F·g−1 at 1 A·g−1 with an energy density up to 140.14 Wh·kg−1 at a high power density level of 811.46 W·kg−1 in Ni2Co1Fe0.75Al0.25-LDH//AC unit. Moreover, after undergoing rigorous testing involving 5000 cycles at 5 A·g−1, Ni2Co1Fe0.75Al0.25-LDH//AC demonstrated a 55.31% retention rate, significantly higher than that observed for Ni2Co1Fe1-LDH//AC (17.58%). The Al doping strengthened the stability of host layer structure and further improved the interlaced structure of LDH, resulted in a significant improvement in specific capacitance, energy density and cycle performance. This improved material will exhibit better application prospects in supercapacitors.

Stable Operation Induced by Plastic Crystal Electrolyte Used in Ni-Rich NMC811 Cathodes for Li-Ion Batteries.

The LiNi0.8Mn0.1Co0.1O2 (NMC811) cathode material has been of significant consideration owing to its high energy density for Li-ion batteries. However, the poor cycling stability in a carbonate electrolyte limits its further development. In this work, we report the excellent electrochemical performance of the NMC811 cathode using a rational electrolyte based on organic ionic plastic crystal N-ethyl-N-methyl pyrrolidinium bis(fluorosulfonyl)imide C2mpyr[FSI], with the addition of (1:1 mol) LiFSI salt. This plastic crystal electrolyte (PC) is a thick viscous liquid with an ionic conductivity of 2.3 × 10-3 S cm-1 and a high Li+ transference number of 0.4 at ambient temperature. The NMC811@PC cathode delivers a discharge capacity of 188 mA h g-1 at a rate of 0.2 C with a capacity retention of 94.5% after 200 cycles, much higher than that of using a carbonate electrolyte (54.3%). Moreover, the NMC811@PC cathode also exhibits a superior high-rate capability with a discharge capacity of 111.0 mA h g-1 at the 10 C rate. The significantly improved cycle performance of the NMC811@PC cathode can be attributed to the high Li+ conductivity of the PC electrolyte, the stable Li+ conductive CEI film, and the maintaining of particle integrity during long-term cycling. The admirable electrochemical performance of the NMC811|C2mpyr[FSI]:[LiFSI] system exhibits a promising application of the plastic crystal electrolyte for high voltage layered oxide cathode materials in advanced lithium-ion batteries.

Solid Electrolyte Interface Film-Forming and Surface-Stabilizing Bifunctional 1,2-Bis((trimethylsilyl)oxy) Benzene as Novel Electrolyte Additive for Silicon-Based Lithium-Ion Batteries.

The application of Si-based anodes in lithium-ion batteries (LIBs) has garnered significant attention due to their high theoretical specific capacity yet is still challenged by the substantial volume expansion of silicon particles during the lithiation process, resulting in the instability of the electrode-electrolyte interphase and deteriorative battery performance. Herein, an ortho(trimethylsilyl)oxybenzene electrolyte additive, 1,2-bis((trimethylsilyl)oxy) benzene (referred to as BTMSB), has been investigated as a bifunctional electrolyte additive for Si-based LIBs. The BTMSB can form a uniform and robust LiF-rich solid electrolyte interphase (SEI) on the surface of Si-based material particles, adapting the huge volume expansion of the Si-based electrode and facilitating lithium-ion transport. Additionally, the BTMSB demonstrates the ability to scavenge hydrofluoric acid (HF) to stabilize the electrode-electrolyte interphase. The SiOx/C∥Li batteries with 2% BTMSB exhibit improved cycle performance and current-rate capabilities, of which the capacity retention retains 69% after 400 cycles. Furthermore, Si-based anode cells with higher theoretical specific capacities (1C = 550 mAh g-1) and NCM523∥SiOx/C pouch cells are constructed and evaluated, displaying superior cycle performance. This work provides valuable insights for the development of effective electrolyte additives and the commercialization of high energy density LIBs with Si-based anodes.

Ultrafast transformation of natural graphite into self-supporting graphene as superior anode materials for lithium-ion batteries

Graphite possesses remarkable potential as an anode material for lithium-ion batteries, thanks to its superb electrical conductivity and eco-friendliness. Nevertheless, challenging issues persist, such as its low maximum theoretical lithium storage capacity and constraints associated with the regular layered structure, which impede its practical application and advancement. In this regard, we proposed a novel approach to enhance the energy storage performance of lithium-ion batteries, involving the modification of natural graphite through irradiation with a high-current pulsed electron beam (HCPEB). Microscopic observations revealed that during the in-situ transformation of graphite particles into self-supporting graphene nanosheets, the high temperature generated by HCPEB irradiation led to the formation of structural defects, including Stone Wales and double vacancy defects. Consequently, the modified natural graphite electrode (particle size 12 μm) exhibited a reversible capacity of 420.4 mAh/g at 0.2C and maintained 94.5% of its reversible capacity after 500 cycles. In comparison to unmodified graphite (particle size 12 μm), the SEI film displayed enhanced stability, significantly improving cycling performance. These findings demonstrated that the defective graphene nanosheet structure enhances lithium storage activity sites, enlarges layer spacing, and enhances lithium storage performance. This study presents an efficient and environmentally friendly method for producing superior anode materials for lithium-ion batteries.

Performance evaluation of a solar-assisted ejector-enhanced vapor injection heat pump cycle

In this study, a solar-assisted ejector-enhanced flash tank vapor injection heat pump cycle (SEE-FVIC) is proposed. Compare to the flash tank vapor injection heat pump cycle (FVIC), the modified cycle introduces solar energy and ejector. On the one hand, the heat from the solar energy is used. On the other hand, the booster function of the ejector effectively reduces the refrigerant mass flowing into the low-pressure stage of the compressor, leading to reducing power consumption of the compressor and improving cycle performance. The cycle performance is studied under typical operating conditions. In particular, a comprehensive analysis of the optimum intermediate pressure Pio of the compressor is also carried out. The results show that the optimum Pio of the SEE-FVIC is higher than that of FVIC for the same operating conditions, which is 1100 kPa and 1300 kPa, respectively. Compared to the FVIC, the heating coefficient of performance (COPh) and volumetric heat capacity (Qcv) of the SEE-FVIC are increased by 38.4 % and 89.2 %, respectively, at the corresponding optimum Pio. Besides, the change of Pio has a significant effect on the volume ratio (β) and vapor injection ratio (δ) of the compressor. It is indicated that the δ varies from 0.48 to 0.67 and the corresponding β from 0.90 to 1.16 when the COPh of the SEE-FVIC reaches its maximum value for a given operating conditions.

Hybrid ionic/electronic interphase enabling uniform nucleation and fast diffusion kinetics for stable lithium metal anode

Lithium (Li) dendrite issue, which is usually caused by inhomogeneous Li nucleation and fragile solid electrolyte interphase (SEI), impedes the further development of high-energy Li metal batteries. However, the integrated construction of a high-stable SEI layer that can regulate uniform nucleation and facilitate fast Li-ion diffusion kinetics for Li metal anode still falls short. Herein, we designed an artificial SEI with hybrid ionic/electronic interphase to regulate Li deposition by in-situ constructing metal Co clusters embedded in LiF matrix. The generated Co and LiF both enable fast Li-ion diffusion kinetics, meanwhile, the lithiophilic properties of Co clusters can serve as Li-ion nucleation sites, thereby contributing to uniform Li nucleation and non-dendritic growth. As a result, a dendrite-free Li deposition with a low overpotential (16.1 mV) is achieved, which enables an extended lifespan over 750 h under strict conditions. The full cells with high-mass-loading LiFePO4 (11.5 mg/cm2) as cathodes exhibit a remarkable rate capacity of 84.1 mAh/g at 5 C and an improved cycling performance with a capacity retention of 96.4% after undergoing 180 cycles.

Enhancing lithium-air battery performance through CoPc@CNT composites: Electrochemical analysis and insights

Cobalt-phthalocyanine (CoPc) catalysts have shown great promise for enhancing the performance of lithium‑oxygen (Li-O2) batteries, offering benefits such as efficient lithium storage, high reversible capacity, improved cycle performance, and enhanced charge and discharge capacity. In this study, we focused on the synthesis of CoPc‑carbon nanotube (CNT) composites with porous structure. The composites were prepared by synthesizing CoPc compounds and interacting them with CNTs using a 3D ball mill shaker. Comprehensive spectroscopic techniques including NMR, FTIR, and UV were employed to characterize the newly synthesized phthalonitrile and phthalocyanine compounds. The surface morphologies of the composite materials were investigated using SEM, EDX, mapping and TEM analysis, enabling the determination of particle sizes and chemical compositions. XRD and XPS analyses confirmed that the composite structures were consistent with the existing literature. BET analysis revealed multilayer isotherm for the composites, indicating their favorable properties. The composite catalysts were incorporated into batteries and their performance was evaluated through various electrochemical tests. Notably, the CoPc1-CNT composite exhibited a remarkable discharge capacity of 3400 mAh g−1catalyst in the prepared battery.

Improved cycling performance of silicon-based nanocomposites with pyrolytic polyacrylonitrile for lithium-ion batteries

The Si/FeSi2@C composite material offers several advantages due to its unique design. It effectively combines the high capacity and safety features of the Si negative electrode with FeSi2’s stabilizing properties. By incorporating a homogeneous carbon layer, the composite material enhances electrical conductivity and provides structural support, thereby mitigating the detrimental effects of significant volume expansion resulting from repeated insertion and extraction of lithium ions. Furthermore, the composite material contributes to stabilizing the solid-electrolyte interphase (SEI) film, which is a critical factor in battery performance. The improved SEI film stability, combined with the overall enhancement in electronic conductivity, significantly enhances the performance of the negative electrode. Test results demonstrate that the composite, consisting of pyrolyzed polyacrylonitrile and Si/FeSi2 nanoparticles, exhibits excellent electrochemical properties. During the first charging cycle, the composite material achieves a specific capacity of 1280 mAh g−1. Impressively, after 200 cycles, the specific capacity of the composite doubles compared to that of the raw material, indicating a remarkable improvement in cycling stability. These findings highlight the positive impact of rational material design on the performance of the Si/FeSi2@C composites.

Preparation of manganese-doped cubic carbon electrode based on ZIF-8 and its capacitive deionization performance for fluoride removal

Fluoride pollution will cause serious harm to the human ecological environment. The capacitive deionization method for fluoride removal has the advantages of low cost, low energy consumption, and convenient operation. Electrode material is crucial for desalination performance. In this study, a novel manganese doped hollow cubic carbon material (MHCC) was prepared by constructing ZIF-8 with hollow cubic morphology as a precursor and carbonizing it with manganese acetate as a manganese source. Then, the derived MHCC material was characterized and tested for capacitive fluoride removal. The adsorption capacity of MHCC10 (the mass ratio of carbon material to manganese acetate tetrahydrate was 10:1) reached 6.2 mg/g and 25.5 mg/g at the initial NaF concentration of 30 mg/L and 150 mg/L respectively. It could maintain 85.5% of the initial capacity after 10 adsorption–desorption cycles. The CDI defluoridation mechanism of MHCC was analyzed. The hollow porous structure inherited from etched ZIF-8 can promote the formation of electric double layers. An appropriate amount of manganese doping has a pseudocapacitive effect, which helps to increase adsorption capacity and improve cycling performance. This work provides a new approach for the design and preparation of novel capacitive fluoride removal electrode materials.

Improved Cycle Performance of Li-CO2 Batteries with Nickel Manganite Supported Carbon Nanotube NiMn2O4 @CNT Cathode

Rechargeable Li-CO2 batteries have emerged as promising candidates for next generation batteries due to their low cost, high theoretical capacity, and ability to capture the greenhouse gas CO2. However, these batteries still face challenges such as slow reaction kinetic and short cycle performance due to the accumulation of discharge products. To address this issue, it is necessary to design and develop high efficiency electrocatalysts that can improve CO2 reduction reaction. In this study, we report the use of NiMn2O4 electrocatalysts combined with multiwall carbon nanotubes as a cathode material in the Li-CO2 batteries. This combination proved effective in decomposing discharge products and enhancing cycle performance. The battery shows stable discharge–charge cycles for at least 30 cycles with a high limited capacity of 1000 mAh g−1 at current density of 100 mA g−1. Furthermore, the battery with the NiMn2O4@CNT catalyst exhibits a reversible discharge capacity of 2636 mAh g−1. To gain a better understanding of the reaction mechanism of Li-CO2 batteries, spectroscopies and microscopies were employed to identify the chemical composition of the discharge products. This work paves a pathway to increase cycle performance in metal-CO2 batteries, which could have significant implications for energy storage and the reduction of greenhouse gas emissions.

Nitrogen-sodium co-doping improves cycle performance of lithium titanate anode materials at high rate

Li4Ti5O12 is a lithium-ion battery cathode material with great potential for development because of its “zero-strain” characteristics, but its low lithium ion diffusion and conductivity rate lead to poor rate and cycling performance. NaN-LTO, a nanorod-like material with oxygen vacancies on the surface, was prepared by calcination after hydrothermal reaction using sodium molybdate as the sodium source and L-cysteine as the nitrogen source and structural guiding agen, while achieving co-doping of N and Na at the O and Li positions in situ respectively. The effects of N and Na co-doping on the crystal and electronic structures were revealed. The electrochemical test results show that rate and cycle performance of NaN-LTO are greatly improved, which can reach 126.0 mAh/g at 20C (1C = 175 mAh/g), 126.9 mAh/g after 1000 cycles with a capacity retention rate of 100.7% and the capacity retention rate is 74.0% after 3000 cycles. The co-doping strategy of Li-site and O-site provides a new modification idea to enhance the electrochemical performance of lithium titanate. Meanwhile, the preparation cost of lithium titanate can be reduced by the partial replacement of Li by inexpensive Na.

Experimental and Computational Study on SEI Composition and Electrochemical Performance of Lithium-Ion Battery with Silicon Oxide-Graphite Composite Electrode

Demand on batteries with high energy density is surging. Conventionally, carbon materials have been used as an anode active material, but recently silicon materials are likely to be incorporated to form a composite anode in lithium-ion batteries (LIBs) for higher energy density. However, LIBs which include silicon materials in anode tend to show a low cycle performance especially the ratio of silicon materials in the anode increases. Commercial LIBs still have difficulty in incorporating large amount of silicon materials especially under the requirements where multiple aspects like safety, charging rate and energy density should be totally met.One potential pathway to improve the cycle performance in LIBs with silicon materials is to tune the nature of solid electrolyte interphase (SEI), a thin film which forms at the interface between anode active material and electrolyte. The nature of SEI is particularly important for LIBs with silicon materials because such silicon active materials show large volume changes during battery operation and SEI is dynamically reconstructed. It has been qualitatively reported so far that LiF is an important component for better battery performance. Our work suggests that the ratio of LiF in initially formed SEI is a crucial factor to realize improved cycle performance in such LIBs.In our work, anode with silicon oxide (SiOx)-graphite composite is considered. We investigated the relationship between electrochemical performance of the cell with such composite electrode and the nature of the film estimated by characterization and molecular simulation. We systematically changed the composition of liquid electrolyte to form various types of SEI on anode surface. For characterization, both fresh and aged cells with different electrolytes were dismantled, and SEI components were extracted by designated solvents, then NMR (nuclear magnetic resonance) was applied to identify the SEI species and quantify the amounts of major SEI components. Comparison between the evolution of SEI amount and an impedance element in electrochemical impedance spectroscopy during aging indicates that degradation of the cells is closely related to the growth of SEI. To further deepen understanding the role of LiF, molecular dynamics simulation was carried out, where the mixture of LiF and typical organic SEI was modelled. Correlation between calculated mechanical property and measured electrochemical performance of the cells were revealed. In our presentation, the requirements that SEI should satisfy will be discussed from the insight of electrochemical measurements, NMR characterization and modeling approaches.

Improving Cycling Performance of Anode-Free Lithium Batteries by Pressure Control

For the anode-free Lithium (Li) batteries (AFLBs), an uniform/dense Li deposition is ideal to stabilize the interface with a solid electrolyte interface (SEI) layer between copper current collector and liquid electrolyte, and minimize the electrolyte/lithium consumption for long-term cell operation. Unlike in the case of Li-ion or Li-metal battery systems where Li metal foil and graphite anode can serve as a cushion to uniformly distribute the pressure, the deposited Li in AFLB is much more sensitive to the pressures and current distribution applied on the copper foil electrode in the AFLBs. We found that the commercial coin cell components lead to a non-uniform/porous Li deposition and further a brittle SEI layer after the cell was charged to 4.5V and discharged to 3.5V, respectively. This non-uniform interface results in poor cycling performance of AFLB coin cells. In this work, we optimized the internal pressure in the coin cells and revealed the internal pressure effect on stabilizing a SEI layer and improving AFB cycling performance.

Li2So4 Coating of Co-Free, Li-Rich Layered Oxide Cathodes through a Carbonate Coating Method for Improving Cycle Performance

In the continued evolution toward high-performance lithium-ion batteries, cobalt has presented itself as a major obstacle due to its price and accessibility. Thus, Co-Free, Li-rich Layered Oxide Cathodes (CF-LLC) have become a promising cathode candidate for their exclusion of Cobalt and high theoretical capacity. Nevertheless, CF-LLC suffers from LLC issues such as phase transformation and voltage fade. Due to high overpotential from sluggish kinetics, the oxygen plateau of CF-LLC occurs at a higher-than-normal potential, leading to a shortened first cycle charge and lower discharge capacity. To mitigate this, we implemented a sulfate coating of the carbonate precursor; which upon lithiation, presents a Li2SO4 coated LLC (S-CF-LLC). The Li-sulfate coating prevents agglomeration of the primary particles during lithiation, leading to a larger surface area and thus, faster kinetics. The coating also prevents increased degradation from the increased surface area by acting as a protective barrier. The S-CF-LLC was successfully synthesized using a hydrothermal synthesis method with a wet chemical coating step and the synthesis was confirmed using XRD, SEM, XPS, and HR-TEM techniques. Galvanostatic cycling showed that the first cycle improved from 236.1mAhg-1 to 263.5mAhg-1 after coating, owing to the improved kinetics. GITT analysis of the increased diffusion coefficient further confirmed the overall improved kinetics. Moreover, the efficacy of the coating was shown through cycle data after 100 cycles, which showed good coulombic efficiency with a high average of >99%, good capacity retention, and good voltage fade per cycle improvement. Overall, the successfully synthesized S-CF-LLC opens up the possibility of practical cobalt-free high-performance batteries.

Controlled synthesis of hollow Si-C microspheres and its potential as an anode material in lithium-ion batteries

Hollow structure has great potential in lithium-ion batteries, especially in Si-based anode materials. Unlike the usual templating process, here, we report a template-free synthetic strategy to build hollow microspheres of Si-C hybrid materials, which combines an in-situ polymerization process to form precursor and magnesiothermic reduction towards the inner cavity. As a result, the hollow Si-C microspheres exhibit improved cycling performance (768.7 mA h g−1 after 100 cycles at 0.84 A g−1) and good rate capability (497.1 mA h g−1 at 8.4 A g−1) when used as an anode material in lithium-ion batteries. This work provides a controllable and industrially-scalable operation based on cheap source to synthesize hollow Si-C hybrid materials, which combines the advantage of hollow structure and carbon matrix to achieve better electrochemical performance than the solid one.