NiCoO2 nanosheets grown on nitrogen-doped porous carbon sphere as a high-performance anode material for lithium-ion batteries

NiCoO₂ nanosheets grown on nitrogen-doped porous carbon spheres (NiCoO₂@N-PCs) have been synthesized via a facile approach using gelatin nanospheres (GNSs) as the template, carbon and nitrogen sources. Due to the synergistic effect between the NiCoO₂ nanosheets and N-PCs, the NiCoO₂@N-PCs composite exhibits an ultrahigh discharge capacity of 978 mAh g^?1 at a current density of 200 mA g^?1 with minimal capacity loss even after 80 cycles. The superior properties of NiCoO₂@N-PCs illustrate that amorphous carbon matrix could significantly improve the electrochemical performance of high-capacity metal oxide anode nanomaterials. Findings from this study suggest that these GNSs may be used to synthesize functional metal oxides, including MnO₂, Fe₂O₃, CoO and NiO@N-PCs nanostructures.     

Fabrication of carbon nanofiber-driven electrodes from electrospun polyacrylonitrile/polypyrrole bicomponents for high-performance rechargeable lithium-ion batteries

Carbon nanofibers were prepared through electrospinning a blend solution of polyacrylonitrile and polypyrrole, followed by carbonization at 700 °C. Structural features of electrospun polyacrylonitrile/polypyrrole bicomponent nanofibers and their corresponding carbon nanofibers were characterized using scanning electron microscopy, differential scanning calorimeter, thermo-gravimetric analysis, wide-angle X-ray diffraction, and Raman spectroscopy. It was found that intermolecular interactions are formed between two different polymers, which influence the thermal properties of electrospun bicomponent nanofibers. In addition, with the increase of polypyrrole concentration, the resultant carbon nanofibers exhibit increasing disordered structure. These carbon nanofibers were used as anodes for rechargeable lithium-ion batteries without adding any polymer binder or conductive material and they display high reversible capacity, improved cycle performance, relatively good rate capability, and clear fibrous morphology even after 50 charge/discharge cycles. The improved electrochemical performance of these carbon nanofibers can be attributed to their unusual surface properties and unique structural features, which amplify both surface area and extensive intermingling between electrode and electrolyte phases over small length scales, thereby leading to fast kinetics and short pathways for both Li ions and electrons.     

Hierarchical porous TiNb2O7@N-doped carbon microspheres as superior anode materials for lithium ion storage

TiNb₂O₇ is considered to be one of the ideal candidate anode materials for lithium-ion batteries (LIBs) because of its safe working potential and high theoretical capacity. However, its low intrinsic conductivity and poor ionic diffusion rate hinder its practical application. In this study, an ultrathin N-doped carbon coating was uniformly deposited onto hierarchical porous TiNb₂O₇ microspheres by combining a solvothermal route with a carbonization process using ionic liquid. The TiNb₂O₇@N-doped carbon microspheres exhibited an ultra-high rate performance (208 mA h g^?1 at 30 C) and excellent cycling stability (specific capacity retention of 79% after 500 cycles at 10 C), and showed excellent electrochemical performance in a full cell using LiNi_0·5Mn_0·3Co_0·2O₂ as a cathode. The superior performance can be attributed to the synergistic effects between the ultrathin N-doped carbon coating and unique microstructure. Therefore, TiNb₂O₇@N–C is a promising negative electrode for high-power LIBs.     

MnO/C core-shell nanorods as high capacity anode materials for lithium-ion batteries

MnO/C core-shell nanorods were synthesized by an in situ reduction method using MnO₂ nanowires as precursor and block copolymer F127 as carbon source. Field emission scanning electron microscopy and transmission electron microscopy analysis indicated that a thin carbon layer was coated on the surfaces of the individual MnO nanorods. The electrochemical properties were evaluated by cyclic voltammetry and galvanostatic charge-discharge techniques. The as-prepared MnO/C core-shell nanorods exhibit a higher specific capacity than MnO microparticles as anode material for lithium ion batteries.     

Fabrication and characterization of three-dimensional carbon electrodes for lithium-ion batteries

This paper presents fabrication and testing results of three-dimensional carbon anodes for lithium-ion batteries, which are fabricated through the pyrolysis of lithographically patterned epoxy resins. This technique, known as Carbon-MEMS, provides great flexibility and an unprecedented dimensional control in shaping carbon microstructures. Variations in the pattern density and in the pyrolysis conditions result in anodes with different specific and gravimetric capacities, with a three to six times increase in specific capacity with respect to the current thin-film battery technology. Newly designed cross-shaped Carbon-MEMS arrays have a much higher mechanical robustness (as given by their moment of inertia) than the traditionally used cylindrical posts, but the gravimetric analysis suggests that new designs with thinner features are required for better carbon utilization. Pyrolysis at higher temperatures and slower ramping up schedules reduces the irreversible capacity of the carbon electrodes. We also analyze the addition of Meso-Carbon Micro-Beads (MCMB) particles on the reversible and irreversible capacities of new three-dimensional, hybrid electrodes. This combination results in a slight increase in reversible capacity and a big increase in the irreversible capacity of the carbon electrodes, mostly due to the non-complete attachment of the MCMB particles.     

Autogenic reactions for preparing carbon-encapsulated, nanoparticulate TiO2 electrodes for lithium-ion batteries

We report an anhydrous, autogenic technique for synthesizing electronically interconnected, carbon-encapsulated, nanoparticulate anatase anode materials (TiO₂-C) for lithium-ion batteries. The TiO₂-C nanoparticles provide a reversible capacity of ∼200 mAh g⁻¹, which exceeds the theoretical capacity of the commercially attractive spinel anode, Li₄Ti₅O₁₂ (175 mAh g⁻¹) and is competitive with the capacity reported for other TiO₂ products. The processing method is extremely versatile and has implications for preparing, in a single step, a wide variety of electrochemically active compounds that are coated, in situ, with carbon.     

3D CNTs networks enable core-shell structured Si@Ni nanoparticle anodes with enhanced reversible capacity and cyclic performance for lithium ion batteries

Silicon, to be a potential anode material of LIBs, possesses a pretty high lithium storage capacity. However, the structural integrity can be destructed by its huge volume expansion through cycles, which results in a large capacity attenuation. Meanwhile, the poor electrochemical performance of silicon-based anodes can be attributed to its poor conductance which reduces the reaction kinetics. According to the above challenges, core-shell structured silicon-nickel nanoparticles have been dispersed on 3D intertwined carbon nanotube networks (Si@Ni-NP/CNTs) via nitric acid pre-treatment and amino functionalization. The nickel-plated shell outside silicon core nanoparticles (Si@Ni-NP) can play a certain supporting role to prevent the volume expansion of silicon, which finally brings down the degree of powdering. Especially, the 3D framework composed of intertwined carbon nanotubes can efficiently provide not only an ample buffer space during intercalation/deintercalation but also a more stable conductive network to increase ion/electron transfer rate. Due to the above improvements in structural stability and reaction kinetics, Si@Ni-NP/CNTs reveal a reversible capacity of 1008 mAh g^?1 with a 98% capacity retention over 100 cycles at a current density of 100 mA g^?1. Under different current densities in rate test, the specific capacity recovery rate can reach 92%. The novel structure enables Si@Ni-NP/CNTs excellent stability under cycles and various rates, as a promising anode material of LIBs.     

Ordered CoO/CMK-3 nanocomposites as the anode materials for lithium-ion batteries

A novel ordered mesoporous carbon hybrid composite, CoO/CMK-3, is prepared by an infusing method using Co(NO₃)₂·6H₂O as the cobalt source. The products are characterized by X-ray diffraction, transmission electron microscopy and N₂ adsorption-desorption analysis techniques. It is observed that the CoO nanoparticles are loaded in the channels of mesoporous carbon. The mesopore structure of CMK-3 is destroyed gradually with increasing of the CoO content. The electrochemical properties of samples as the anode materials for lithium-ion batteries are studied by galvanostatic method. The results show that the CoO/CMK-3 composites have higher reversible capacities (more than 700 mAh g⁻¹) and better cycle performance in comparison with the pure mesoporous carbon (CMK-3). Based on the above results, a mechanism is proposed to explain the reason of such a substantial improvement of electrochemical performance in the CoO/CMK-3 composites.     

Applications of carbon nanotubes in the lithium-ion batteries

碳纳米管因具有优异的电导率、热导率、力学性能以及独特的结构形貌,被用于改进锂离子电池性能。该文总结了近年来碳纳米管作为锂离子电池的添加剂、电极材料复合基体以及集流体的最新研究进展,重点介绍了最新的碳纳米管作为电极材料添加剂的使用方法、碳纳米管与电极材料的不同复合方法及其对锂离子电池容量性能、倍率性能以及循环寿命的影响。同时指出了碳纳米管在锂离子电池中大规模应用时需要克服的问题,如降低碳纳米管的制备成本、开发适用于工业生产的复合技术、改善碳纳米管的分散性能等。     

A simple and low-cost charger for lithium-ion batteries

A simple low-cost battery charger based on a saturated controller is proposed for charging of lithium-ion (Li-ion) batteries. When the reference voltage of the closed-loop process is set to 4.2 V, the charging process resembles a constant-current and constant-voltage (CC-CV) charging strategy. The charging process can easily be shortened by raising the limit on the saturated controller. Experimental results are included to demonstrate the effectiveness of the charger. It is anticipated that the charger can be a low-cost high-performance replacement of existing Li-ion battery chargers.     

Recent progress in rechargeable nickel/metal hydride and lithium-ion miniature rechargeable batteries

VARTA is searching for alternative battery solutions for memory back-up and bridging applications, and for this, it is developing nickel/metal hydride and lithium-ion button cells. Presented are the results on different sizes and forms of lithium-ion cells (621, 1216 and 2025) containing different electrode materials and shapes. Presently, the most favoured cathode material is lithiated manganese dioxide. The electrodes are made from both solid and porous materials and, together with an organic electrolyte, result in a cell system with a voltage level of approximately three. Included are results, both from these lithium-ion cells, and also from ones using the nickel/metal hydride system.     

Improvement of cyclic behavior of a ball-milled SiO and carbon nanofiber composite anode for lithium-ion batteries

The cyclic performance of a composite SiO and carbon nanofiber (CNF) anode was examined for lithium-ion batteries. SiO powder of several micrometers was pulverized using high energy mechanical milling. The SiO was ball-milled for 12 h with CNF to produce a composite electrode material that exhibited excellent cycling performance. A reversible capacity of approximately 700 mAh g⁻¹ was observed after 200 cycles. The excellent cyclic performance was discussed with respect to the change of the valence state of Si by ball-milling. A large irreversible capacity at the first cycle for the SiO/CNF composite electrode was reduced to 2% by chemically pre-charging with a lithium film attached to the rim of the electrode.     

Future cathode materials for lithium rechargeable batteries

Lithium rechargeable batteries are now well established as power sources for portable equipment, such as portable telephones or computers. Future applications include electric vehicles. However before they can be used for this, or other price-sensitive applications, new cathode materials of much lower cost are needed. Possible cathode materials are reviewed.     

Self-discharge behavior and its temperature dependence of carbon electrodes in lithium-ion batteries

Self-discharging characteristics of negative electrodes with different carbon materials have been investigated by monitoring the open circuit potential (OCP), the capacity loss and the ac impedance change during the storage at different temperatures. The OCP change with the storage time reflected state-of-charge (SOC), which depended on both the carbon material and the storage temperature. Higher specific surface area of the material and higher storage temperature lead to higher self-discharging rate. The activation energy for self-discharging was estimated from the temperature dependence of the self-discharging rate. Although small difference was observed among the materials, the value of the activation energy suggests that the self-discharging reaction at each electrode is controlled by a diffusion process. Changes in the interfacial resistance with the storage time reflected the growth of so-called Solid Electrolyte Interphase (SEI) at carbon surface. The rate of SEI formation at lower temperature does not depend on the carbon material, but at higher storage temperature the rate on spherical graphite was much higher than those on the other carbon materials.     

Dimethyl methylphosphonate-based nonflammable electrolyte and high safety lithium-ion batteries

Dimethyl methylphosphonate (DMMP) was used as a cosolvent to reformulate the nonflammable electrolyte of 1 M LiPF₆/EC + DEC + DMMP (1:1:2 wt.) in order to improve the safety characteristics of lithium-ion batteries. The flammability, cell performance, low-temperature performance and thermal stability of the DMMP-based electrolyte were compared with the electrolyte of 1 M LiPF₆/EC + DEC (1:1 wt.). The nonflammable electrolyte exhibits good oxidation stability at the LiCoO₂ cathode and poor reduction stability at the mesocarbon microbead (MCMB) and surface-modified graphite (SMG) anodes. The addition of vinyl ethylene carbonate (VEC) to the DMMP-based electrolyte provided a significant improvement in the reduction stability at the carbonaceous electrodes. Furthermore, it was found that the addition of DMMP resulted in optimized low-temperature performance and varied thermal stability of the electrolytes. All of the results indicated the novel DMMP-based electrolyte is a promising nonflammable electrolyte to resolve the safety concerns of lithium-ion batteries.     

Characterization of high-power lithium-ion batteries by electrochemical impedance spectroscopy. I. Experimental investigation

The influence of the operation conditions temperature and state of charge (SOC) on the performance of a commercial high-power lithium-ion cell is investigated by electrochemical impedance spectroscopy. Based on the results of several preliminary tests, measurements were run covering the complete range of automotive applications.The cell impedance is presented and analyzed. A strong nonlinear temperature correlation is shown for all frequency ranges. Although the ohmic resistance is nearly unaffected by variation in SOC, the mass transport impedance reduces from 100% to 60% SOC and increases significantly again for lower SOCs.     

High-power LiFePO4 cathode materials with a continuous nano carbon network for lithium-ion batteries

To meet the requirements of high-power products (ex. electric scooters, hybrid electric vehicles, pure electric vehicles and robots), high-energy safe lithium-ion batteries need to be developed in the future. This research will focus on the microstructures and electrochemical properties of olivine-type LiFePO₄ cathode materials. The morphologies of LiFePO₄/C composite materials show spherical-type particles and have good carbon conductive networks. From the TEM bright field image and EELS mapping, the LiFePO₄/C powder shows continuous, dispersive nano-carbon network. These structures will improve electron transfer and lithium-ion diffusion for LiFePO₄ cathode materials, and increase their conductivity from 10⁻⁹ S cm⁻¹ to 10⁻³ S cm⁻¹. The electrochemical properties of LiFePO₄/C cathode material in this work demonstrated high rate capability (≥12 C) and long cycle life (≥700 cycles at a 3 C discharge rate).     

Facile synthesis of efficient core-shell structured iron-based carbon catalyst for oxygen reduction reaction

Controlled synthesis of efficient core-shell non-precious metal catalysts for oxygen reduction reaction (ORR) is undoubtedly crucial but challenging for the extensive application of fuel cells and metal-air batteries. Herein, we prepared a core-shell structured Fe/FeC_x nanoparticles and porous carbon composited catalyst (Fe/FeC_x@NC) via a facile two-step heat treatment strategy. The Fe/FeC_x@NC-800_?0.5 prepared with secondary anneal at 800 °C for 0.5 h exhibits superior ORR performance to the commercial Pt/C in terms of comparable onset potential, higher half-wave potential, and outstanding long-term durability in alkaline media. Through combining the physical and electrochemical characterizations of Fe/FeC_x@NC-T_?t with different anneal temperature and precursors, the outstanding ORR performance of Fe/FeC_x@NC-800_?0.5 is caused by the synergistic effect between Fe/FeC_x core and enriched pyridinic N- and graphitic N-doped carbon shell as well as porous carbon with large specific surface area. The structure-activity relationship of core-shell structured Fe–N–C catalysts for ORR provides directions for the development of advanced nonprecious metals catalysts.     

Cresyl diphenyl phosphate as flame retardant additive for lithium-ion batteries

To improve the safety of lithium-ion batteries, cresyl diphenyl phosphate (CDP) was used as a flame retardant additive in a LiPF₆ electrolyte solution. The flammability of the electrolytes containing CDP and the electrochemical performances of the cells, LiCoO₂/Li, graphite/Li and the battery LiCoO₂/graphite with these electrolytes, were studied by measuring the self-extinguishing time of the electrolytes, the variation of surface temperature of the battery and the charge/discharge curve of the cells or battery. It is found that the addition of CDP to the electrolyte provides a significant suppression in the flammability of the electrolyte and an improvement in the thermal stability of battery. On the other hand, the electrochemical performances of the cells become slightly worse due to the application of CDP in the electrolyte. This alleviated trade-off between the flammability and thermal stability and cell performances provides a possibility to formulate a nonflammable electrolyte by using CDP.     

A review of processes and technologies for the recycling of lithium-ion secondary batteries

The purpose of this paper is to review the current status of the recycling technologies of spent lithium-ion secondary batteries. It introduced the structure and components of the lithium-ion secondary batteries, summarized all kinds of single recycling processes from spent lithium-ion secondary batteries and presented some examples of typical combined recycling processes. Also, the problems and prospect of the studies of their recycling technologies have been put forward.