Flame-synthesis limits and self-catalytic behavior of carbon nanotubes using a double-faced wall stagnation flow burner

Flame-synthesis limits of carbon nanotubes (CNTs) are measured using a double-faced wall stagnation flow (DWSF) burner that shows potential in mass production of CNTs. With nitrogen-diluted premixed ethylene-air flames established on the nickel-coated stainless steel double-faced plate wall, the limits of CNT formation are determined using field-emission scanning and transmission electron microscopies and Raman spectroscopy. Also, self-catalytic behavior of the synthesized CNTs is evaluated using the DWSF burner with a CNT-deposited stainless steel double-faced plate wall. Results show narrow fuel-equivalence ratio limits of multi-walled CNT (MWCNT)-synthesis at high flame stretch rates and substantially extended limits at low flame stretch rates. This implies that the synthesis limits are very sensitive to the fuel-equivalence ratio variation for the high stretch rate conditions, yielding a lot of impurities and soot rather than MWCNTs. The enhanced ratio of tube inner diameter to wall thickness of the MWCNTs synthesized using a CNT self-catalytic flame-synthesis process is observed, indicating that the quality of metal-catalytic, flame-synthesized MWCNTs can be much improved via the process. Thus, using a DWSF burner with the CNT self-catalytic process has potential in mass production of MWCNTs with improved quality.     

Challenges in data-based degradation models for lithium-ion batteries

This work summarizes the findings resulting from applying an aging modeling approach to four different capacity loss experimental datasets of lithium-ion batteries (LIBs). This approach assumes that the degradation trajectory of the capacity is a function of three variables: time, kinetic constant, and time-dependent factor. The analysis shows that the time-dependent factor α is cell-chemistry dependent and cannot be averaged for calendar and cycling modes and combined modes. This factor was also found to be a function of the stress factors. A quadratic model was used to obtain the kinetic constants per test, and statistical metrics were provided to evaluate the quality of the fitting, which was significantly affected when using averaged values of α and refitted kinetic constants. A set of test matrices is proposed for calendar, cycling, and mixed aging modes to overcome the challenges of data-based models developed from accelerated test approaches for modeling aging in LIBs. This work also proposes a methodology to develop these data-based aging models.     

Synthesis of carbon-coated TiO2 nanotubes for high-power lithium-ion batteries

Carbon-coated TiO₂ nanotubes are prepared by a simple one-step hydrothermal method with an addition of glucose in the starting powder, and are characterized by morphological analysis and electrochemical measurement. A thin carbon coating on the nanotube surface effectively suppresses severe agglomeration of TiO₂ nanotubes during hydrothermal reaction and post calcination. This action results in better ionic and electronic kinetics when applied to lithium-ion batteries. Consequently, carbon-coated TiO₂ nanotubes deliver a remarkable lithium-ion intercalation/deintercalation performance, such as reversible capacities of 286 and 150 mAh g⁻¹ at 250 and 7500 mA g⁻¹, respectively.     

Study of multi-walled carbon nanotubes for lithium-ion battery electrodes

The potential use of multi-walled carbon nanotubes (MWCNTs) produced by Chemical Vapor Deposition (CVD) as conductive agent for electrodes in Li-ion batteries has been investigated. LiNi_0.33Co_0.33Mn_0.33O₂ (NCM) has been chosen as the active material for positive electrodes, and a nano-sized TiO₂-rutile for the negative electrodes. Also the MWCNTs ability of reversibly inserting Li has been characterized. The electrochemical performances of the electrodes are studied by galvanostatic techniques and cyclic voltammetry. In particular the influence of the nanotubes on the rate capability is evaluated. The addition of MWCNTs significantly enhances the rate performances of NCM-based cathodes at all investigated C-rates. The 1 wt.% MWCNTs in TiO₂ rutile-based anodes accounts for an increase in the rate capability when the electrodes are cycled in the potential range 1.0-3.0 V. The range extension to more negative potentials (i.e. 0.1-3.0 V), however, causes a capacity fading especially at higher current rates. The obtained results demonstrate that the addition of MWCNTs to the electrode composition, even in low amounts, enables an increase in both energy and power densities of a Li-ion battery.     

Effect of binders on performances of ceramic coated separators for lithium-ion batteries

为优化陶瓷涂敷隔膜热稳定性,提高锂离子电池的安全性和电化学性能,本工作选用热稳定性优异的聚酰亚胺和电化学稳定的聚偏氟乙烯六氟丙烯作为复合黏结剂,将Al₂O₃无机颗粒涂敷于商品级聚烯烃隔膜两侧。通过调控两种黏结剂组分含量,测试隔膜性能发现,增加聚酰亚胺的含量可以明显提高涂覆隔膜的热稳定性,但隔膜的电化学性能不理想;在黏结剂中引入适量的聚偏氟乙烯六氟丙烯组分,涂覆隔膜可在保持其热稳定性的同时,获得良好的离子电导率、电化学稳定性和金属锂电极兼容性等性能。最后选用电化学性能表现最为优异且热稳定性良好的黏结剂组分制备陶瓷涂敷隔膜,在Li|LiCoO₂电池中,比聚烯烃隔膜表现出更优异的电化学性能,在8 C倍率下的放电比容量为109.3 mA/g,容量保持率为66.1%,而使用PE隔膜的电池的放电比容量和容量保持率仅为88.7 mA/g和54.7%。     

Patent application of silicon-based anode for lithium-ion batteries

本文通过对锂离子电池硅基负极技术领域的专利申请态势进行分析,揭示该技术领域当前的专利活动特点,为我国在该领域的科技创新和产业化提供参考。本文从国际专利申请数量年度分布、主要竞争国家/地区、专利技术来源国和目标国、主要专利申请人等方面,对硅基负极技术领域的专利申请态势进行分析,在此基础上,对世界范围内的主要竞争国家及重要申请人的专利申请特点进行重点分析。分析结果表明,硅基负极专利申请主要集中在中国、美国、日本和韩国。国外申请人注重同时在上述四国进行专利布局,并且已经在我国进行大量专利布局,而我国申请人主要在国内进行专利布局,在国外申请较少。最后,就我国未来的锂离子电池硅基负极技术的研发和专利申请与保护工作提出一些建议。     

Thermal explosion hazards of lithium-ion batteries in hermetic space

使用扩展容积加速度量热仪（extend volume accelerating rate calorimeter,EV-ARC）及耐压罐,开展了密闭空间中不同荷电状态（SOC）下18650型锂离子电池的热爆炸实验。实验发现,SOC=0%时电池不会发生热爆炸,而在其它工况下均发生了热爆炸;电池发生热爆炸时,电池表面最高温度、耐压罐内部最大压力都随着SOC的增加而增大。利用实验中电池发生热爆炸时的初始温度和最高温度,通过计算得到了不同SOC下电池发生热爆炸时的爆炸当量,当SOC=100%时,爆炸当量值最大,为5.45 gTNT,约是SOC=25%时的2.5倍,并在耐压罐中产生40.69 bar的峰值压力。锂离子电池在密闭中的热爆炸危险性随着电池SOC的增加而增大。     

Applications of ultrasound technique in characterization of lithium-ion batteries

锂离子电池由于其在能量密度、循环寿命、能量效率、安全性等方面的综合优势,成为了应用最广泛的电化学储能器件,然而其性能仍有进一步提升的必要。大量的先进表征技术应用在锂电池研究中,有力推动了锂离子电池基础理论的进步。超声作为一种无损表征手段,具有灵敏度高、成本低、使用方便、速度快等优点,在电池特性表征领域具有巨大的应用潜力。本文总结概述了现有超声检测技术在电池表征领域的应用,包括内部气体检测、电解液浸润测试、电池析锂检测、电池荷电状态测量、电池寿命预测等,对其发展前景进行了展望。     

Multiporous core-shell structured MnO@N-Doped carbon towards high-performance lithium-ion batteries

It is imminently to seek for high energy density in addition to a sensational lifetime of lithium-ion batteries (LIBs) to meet growing requisition in the energy storage application. Anode containing metal oxide composite is being thoroughly investigated for their higher capacity than that of the commercial graphite. A multiporous core-shell structured metal oxide composite anode possessing the excellent capacity and superb lifespan for LIBs is designed. In detail, metal oxide (i.e., MnO) is encapsulated in N-doped carbon shell (MnO@N–C) via coprecipitation-annealing technique. During annealing, abundant void space among MnO cores/between MnO cores and N–C shells is obtained. This space can efficaciously buffer volume changes of MnO upon cycles. Benefiting from the unique structure and heteroatom doping, the capacity of MnO@N–C microcube anode exhibits 576 mAh g⁻¹ at 5 A g⁻¹ with an ultra-long lifespan more than 3500 cycles. The connection between the electrode characteristics and structure is concurrently examined by adopting kinetic analysis. Finally, a full lithium-ion battery is presented, applying the MnO@N–C (anode) and Nick-rich layered oxide (cathode). It is believed that structural designing with heteroatom doping can be utilized in vaster fields for superior capabilities.     

The progress in fault diagnosis techniques for lithium-ion batteries

实施精准、可靠的故障诊断,是确保电池系统安全、稳定、可靠运行的关键,并为电池系统的精准运营维护提供理论、方法与技术支撑。本文首先在总结电池系统故障类型与表现形式的基础上,重点分析了在电池制造、成组筛选和使用各个阶段的本体故障引发机制。其次,对现有研究发展的电池系统故障诊断方法进行了分类,大致分为基于电池模型的故障诊断方法和无模型的故障诊断方法。之后,针对不一致故障诊断、短路故障诊断、热故障诊断、传感器故障诊断、连接组件故障诊断和多故障联合诊断,对现有文献提出的解决策略及应用案例进行了全面综述。最后,以全面文献调研为基础,提出了电池系统故障诊断研究面临的主要挑战和未来的研究方向。     

Improvement of cycle property of sulfur-coated multi-walled carbon nanotubes composite cathode for lithium/sulfur batteries

A novel sulfur-coated multi-walled carbon nanotubes composite material (S-coated-MWCNTs) was prepared through capillarity between the sulfur and multi-walled carbon nanotubes. The results of the TEM and XRD measurements reveal that S-coated-MWCNTs have a typical core-shell structure, and the MWCNTs serve as the cores and are dispersed individually into the sulfur matrices. The charge–discharge experiments of the lithium/sulfur cells demonstrated that the S-coated-MWCNTs cathode could maintain a reversible capacity of 670 mAh g⁻¹ after 60 cycles, showing a greatly enhanced cycle ability as compared with the sulfur cathode with simple MWCNTs addition (S/MWCNTs) and the cathode using sulfur-coated carbon black composite (S-coated-CB). The EIS and SEM techniques were used to define and understand the impact of the microstructure of the composite electrode on its electrochemical performance. Derived from these studies, the main key factors to the improvement in the cycle life of the sulfur cathode were discussed.     

Construction and preparation of nitrogen-doped porous carbon material based on waste biomass for lithium-ion batteries

Biomass derived carbon materials have been widely studied as electrodes in energy storage devices due to their renewable nature, low-cost and tunable physical/chemical properties. However, the influences of different treatments for biomass derived carbon materials are still lack of in-depth discussion. In this work, we investigate the effects of the treatment for biomass on the structure and composition of the resulted carbon materials. Especially, the optimal N-doped porous carbon (NPCCS), which was fabricated by H₂SO₄-assisted hydrothermal treatment and subsequent pyrolysis process using corn silk as raw material, shows a unique interconnected layered nanostructure with ultra-high nitrogen content (18.79 at%). As a result, the NPCCS electrode displays excellent cycling stability and outstanding rate performance in lithium-ion half-cell test and shows high first reversible specific capacity of 523.6 mAh g^?1 in full-cell test. This work provides some guidance for preparing biomass derived carbon materials with superior electrochemical performance for the applications in advanced energy storage devices.     

Research progress on electrolyte additives for high voltage lithium-ion batteries

普通锂离子电池在高电压下的氧化分解限制了高压锂离子电池的发展,为了解决这一问题,可以设计、合成新型的耐高压电解液;寻找合适的电解液添加剂,然而从经济效益考虑,发展合适的电解液添加剂来稳定电极/电解液界面更加受到研究者们的青睐。本文综述了最近几年在高压锂离子电池电解液添加剂方面的研究进展,并按照添加剂的种类将其分为6部分进行探讨：含硼类添加剂、有机磷类添加剂、碳酸酯类添加剂、含硫添加剂、离子液体添加剂及其它类型添加剂。分别对这些添加剂的作用机理、作用效果进行了阐述,展望了添加剂在高压锂离子电池中的发展前景及未来研究方向。     

Research progress of high safety flame retardant electrolytes for lithium-ion batteries

商品锂离子电池在机械冲击、热冲击和过充短路等滥用条件下易发生起火燃烧甚至爆炸。为了解决这一安全性问题,需要开发高安全性阻燃电解液取代传统易燃烧的碳酸酯电解液。本文综述了高安全性阻燃电解液的研究进展,首先介绍了燃烧机理、阻燃机理和阻燃测试方法,再阐述锂离子电池对阻燃电解液的性质要求,并对阻燃电解液进行分类探讨,包括阻燃添加剂、阻燃溶剂（共溶剂）、高浓度阻燃电解液、离子液体和阻燃型凝胶聚合物电解质。重点对这些高安全性阻燃电解液的配方、阻燃效果、适用的电池体系进行详细阐述。最后对高安全性阻燃电解液未来的研究方向进行展望。     

Overview of research on thermal safety of lithium-ion batteries

随着锂离子电池在生活和工作中的普及,锂离子电池的安全事故逐年增加,锂离子电池的安全研究逐渐引起学术界的关注。研究锂离子电池的热安全性,可以有效分析锂离子电池发生起火和爆炸的内在原因,指导锂离子电池安全性研究的开展。本文介绍了锂离子电池工作过程中产热的来源和影响因素,以及锂离子电池热失控发生时的内部反应和反应对应的温度,并对电池热失控时的热特性参数进行了总结。     

Review on state of health estimation of retired lithium-ion batteries

由于电池组中电池单体之间存在性能差异,退役锂离子电池在投入梯次利用前需要借助健康状态（SOH）评估技术进行电池单体的分类与配组。健康状态评估系统的构建涉及电池建模、电池测试、数据处理、算法开发等各种技术问题。目前通过基于模型的参数识别与直接提取健康因子是构建SOH评估体系的两种主要思路。在电池模型的简化、测试工况的设计、健康因子的选择和算法的应用与优化等方面已经有了很多研究。如何在缩短电池测试时间的同时提高评估系统的泛化能力是目前该研究领域的主要问题,这些问题的解决对于SOH评估系统真正在梯次利用锂离子电池的产业化中发挥作用至关重要。在未来的研究中通过优化测试工况和数据融合等技术,有望开发出性能更好的SOH评估系统。     

Freestanding graphitic carbon nitride-based carbon nanotubes hybrid membrane as electrode for lithium/polysulfides batteries

Lithium sulfur batteries have drawled worldwide attention in recent years, which benefit of its high-density energetic, low cost, and environmental benignity. Nevertheless, the shuttle effect of polysulfides and resulting self-discharge lead to capacity fade loss and poor electrochemical performance. Herein, graphitic-carbon nitride/carbon nanotubes (g-C₃N₄/CNTs) hybrid membrane is fabricated by the flow-direct vacuum filtration process. The as-prepared 3-D freestanding g-C₃N₄/CNTs membrane employed as positive current collector containing Li₂S₆ catholyte solution for lithium/polysulfides batteries. The fabricated g-C₃N₄/CNTs provide a physical barriers and chemisorption resist polysulfide shuttling. Moreover, the conductive network constructed by CNTs can empower sulfur to be evenly distributed in the cathode and accelerates electron transport. Thus, to further prove the cooperative effect of g-C₃N₄ and CNTs, the freestanding g-C₃N₄/CNTs/Li₂S₆ electrode exhibits more stable electrochemical performance than CNTs/Li₂S₆ electrode, deliver the first discharge capacity of 876 mAh g⁻¹ at 0.5 C and maintained at 633 mAh g⁻¹ after 300 cycles. The sulfur mass in electrode was increased to 7.11 mg, and the g-C₃N₄/CNTs/Li₂S₆ electrode also possess a high capacity retention of 75.5%. Meanwhile, g-C₃N₄ modified CNTs can not only trap polysulfides by strong adsorption but also effectively inhibit the self-discharge behavior of lithium/polysulfides batteries. As a consequence, the g-C₃N₄/CNTs composites for lithium/polysulfides batteries are indicating an excellent electrochemical stability with a long-term storage without obvious capacity degradation.     

Application of biphenyl additive in electrolyte for liquid state Al-plastic film lithium-ion batteries

In order to investigate the influence of the biphenyl (BH) as a polymerizable electrolyte additive on the properties of Al-plastic film lithium-ion batteries, we examined the electrochemical properties of batteries which containing different amounts of BH. The main analysis tools were overcharge tests, linear sweep voltammetry, cycling tests, rate capability, thermal stability, AC impedance, etc. The results showed that the BH can electrochemically polymerize at the overcharge potential of 4.5–5.5 V to form a layer on the cathode surface, the internal resistance was increased rapidly after the electrode covered with the black electro-polymerization production, and the internal short-circuit was occurred with enough polymerization product, all of these caused to low overcharge current and good overcharge performance, meanwhile, the overcharge performance was increased with the increasing of BH content. However, the cycling performance was deteriorated with an increase in BH content, but not seriously, so the content of additive is ought to be adjusted to practical need in production.     

Electrochemical hydrogen storage behavior of single-walled carbon nanotubes (SWCNTs) coated with Ni nanoparticles

The electrochemical hydrogen storage properties of Ni nanoparticle coated SWCNT electrodes were investigated. A surface modification technique enabled different amounts of Ni nanoparticles to be deposited on the SWCNT surface, which was first chemically oxidized by 6 N HNO₃. The characteristic properties of the SWCNT samples coated with 4–12 wt.%Ni nanoparticles were examined using a scanning electron microscope with energy dispersive spectroscopy (SEM/EDX); micro-Raman spectroscopy; thermal analysis techniques consisting of both thermogravimetric analysis (TGA) and differential thermal analysis (DTA), and Brunauer–Emmett–Teller (BET) measurements. It was found that all of the SWCNT samples coated with 4–12 wt.%Ni nanoparticles possessed a similar pore-size distribution. According to the electrochemical test results, the highest electrochemical discharge capacity of 1404 mA h g⁻¹ was obtained for the SWCNT electrode coated with 8 wt.%Ni nanoparticles, which corresponded to 5.27 wt.% hydrogen storage. This enhancement of electrochemical hydrogen storage capacity was ascribed to the fact that the Ni nanoparticles act as a redox site, thus leading to an improved electrochemical hydrogen storage capacity. The results indicated that the SWCNT coated with Ni nanoparticles are a potential material for hydrogen storage.     

Preparation and application of bamboo-like carbon nanotubes in lithium ion batteries

CNTs with bamboo-like structure (B-CNTs) has been prepared via a CVD process with novel carbon precursor. The potential application of B-CNTs as electric conductive additive and anode materials for lithium ion batteries was explored. The EIS spectra prove that it is better electric conductive additive than multiwalled CNTs and traditional carbon black (CB). The electric resistance of the electrode is decreased around 20 Ω when B-CNTs is used instead of CB. The cycle stability is also enhanced. However, the test cell with B-CNTs as anode material shows low reversible capacity of 135 mAh g⁻¹ and very low initial cycle efficiency of 17.3%, which indicates that so-prepared B-CNTs is not suitable for anode material.