氯化钠对锂离子电池石墨负极的修饰改性

Numerous carbonaceous materials have been studied as anodes of lithium ion batteries during the past several years[1￣4].Graphite was favored for battery applications because it exhibits a high specific capac- ity, low working potential close to that of l…     

Understanding High-Rate K+-Solvent Co-Intercalation in Natural Graphite for Potassium-Ion Batteries

Graphite shows great potential as an anode material for rechargeable metal-ion batteries because of its high abundance and low cost. However, the electrochemical performance of graphite anode materials for rechargeable potassium-ion batteries needs to be further improved. Reported herein is a natural graphite with superior rate performance and cycling stability obtained through a unique K⁺-solvent co-intercalation mechanism in a 1 m KCF₃SO₃ diethylene glycol dimethyl ether electrolyte. The co-intercalation mechanism was demonstrated by ex situ Fourier transform infrared spectroscopy and in situ X-ray diffraction. Moreover, the structure of the [K-solvent]⁺ complexes intercalated with the graphite and the conditions for reversible K⁺-solvent co-intercalation into graphite are proposed based on the experimental results and first-principles calculations. This work provides important insights into the design of natural graphite for high-performance rechargeable potassium-ion batteries.     

Understanding High‐Rate K+‐Solvent Co‐Intercalation in Natural Graphite for Potassium‐Ion Batteries

Graphite shows great potential as an anode material for rechargeable metal‐ion batteries because of its high abundance and low cost. However, the electrochemical performance of graphite anode materials for rechargeable potassium‐ion batteries needs to be further improved. Reported herein is a natural graphite with superior rate performance and cycling stability obtained through a unique K⁺‐solvent co‐intercalation mechanism in a 1 m KCF₃SO₃ diethylene glycol dimethyl ether electrolyte. The co‐intercalation mechanism was demonstrated by ex situ Fourier transform infrared spectroscopy and in situ X‐ray diffraction. Moreover, the structure of the [K‐solvent]⁺ complexes intercalated with the graphite and the conditions for reversible K⁺‐solvent co‐intercalation into graphite are proposed based on the experimental results and first‐principles calculations. This work provides important insights into the design of natural graphite for high‐performance rechargeable potassium‐ion batteries.     

Einfluß von Gitterstörungen des Graphits auf die Bildung von Graphithydrogensulfat

Influence of Lattice Defects of Graphite on the Formation of Graphite Hydrogensulfate Various natural and synthetic graphites were oxidized with chromic acid in sulfuric acid to the 1st stage of graphite hydrogensulfate with the intent of determining the inhibition of intercalation by lattice defects. More oxidant than required by stoichiometry is consumed because slow total oxidation to CO₂ is superimposed even at room temperature. The activation energy for total oxidation is reduced by lattice defects. With some graphites, separation of the intercalation reaction from total oxidation was accomplished using calorimetry. The reaction enthalpy in the oxidation of well-crystallized graphites to the graphite salt is ?3.05 kJ/mol C.     

Carbon anode materials from polysiloxanes for lithium ion batteries

Three kinds of silicon-containing disordered carbons have been prepared by pyrolysis of polysiloxanes with different amounts of phenyl side groups. X-ray powder diffraction, X-ray photoelectron spectroscopy and electrochemical capacity measurements were performed to study their behaviors. Graphite crystallites, micropores, and silicon species affect their electrochemical performances. All of them present high reversible capacities, >372 mAh/g. Since the graphite crystallites are very small, they contribute very little to reversible capacity. The number of micropores produced by gas emission during the heat-treatment process decides whether they exhibit reversible capacity. Si mainly exists in the form C–Si–O and influences the irreversible capacity. There is no evident capacity fading in the first ten cycles, indicating promising properties for these disordered carbons.     

Conversion efficiency of γ/β-MnO2 in composites with natural graphite and carbon nanotubes in a prototype lithium battery

Chemically synthesized manganese dioxide γ/β-MnO₂ was studied in composites with multi-walled carbon nanotubes and natural graphite of EUZ-M brand was studied in the redox reaction with lithium. It was shown that nanometer carbon electron-conducting filler is advantageous over the micrometer filler (EUZ-M) in the efficiency of influence exerted on power characteristics and cycling capacity of a prototype lithium battery with a cathode based on γ/β-MnO₂. The effective chemical diffusion coefficient of lithium ions in MnO₂ composites with multi-walled carbon nanotubes and EUZ-M was estimated and hodographs of electrodes based on γ/β-MnO₂ without a carbon additive and with EUZ-M, brought in contact with an electrolyte, were analyzed.     

锂离子电池负极材料纳米多孔硅/石墨/碳复合微球的制备与性能

以硅藻土为原料, 通过镁热还原反应得到多孔硅, 进一步利用砂磨得到纳米多孔硅, 然后通过球磨将其与片状石墨和沥青均匀混合, 采用喷雾干燥技术造粒, 高温煅烧后制备了纳米多孔硅/石墨/碳复合微球. 对所得复合微球的结构和理化性质进行了表征. 纳米多孔硅/石墨/碳复合微球作为锂离子电池负极材料展示出较高的可逆容量、 优异的循环稳定性(100次循环后容量仍为790 mA·h/g, 容量保持率可达96.7%)及较好的倍率性能.     

氟化石墨的电化学性能研究

对系列氟化石墨及其作为碱性电池正极添加剂的电化学性能进行了研究,考察了氟化石墨作为电极活性材料及用作添加剂时电池的放电行为以及氟化石墨的氟化程度和电极中氟化石墨的含量对电池的放电性能的影响.研究了MnO₂中添加氟化石墨后对电极循环性能的影响,并用XRD比较了几种不同碳材料与氟化石墨的结构特点及MnO₂电极放电前后的状态变化,初步探讨了氟化石墨改善二氧化锰电化学性能的作用机制.     

硅/石墨复合物用作锂离子电池负极材料

以石墨和纳米硅粉为原料, 利用机械球磨的方法制备了硅/石墨复合物, 用作锂离子电池负极材料. 采用XRD, SEM以及电化学测试等手段对材料进行了结构表征和性能测试. 通过球磨不同质量比的硅和石墨, 并对相应的复合物进行充放电测试, 寻找到了硅和石墨的最佳比例, 其值为1∶9. 实验结果表明, 所得材料既具备高于纯纳米硅的循环性能, 又具有比石墨高的可逆容量.     

Formation of nanocomposites of styrene and its copolymers using graphite as the nanomaterial

Graphite‐polymer nanocomposites were prepared by melt blending of various graphites (virgin graphite, expandable graphites, and expanded graphite) with polystyrene and its copolymers (acrylonitrile‐butadiene‐styrene (ABS) and high‐impact polystyrene (HIPS)). Nanocomposites were characterized by X‐ray diffraction, cone calorimetry, thermogravimetric analysis and evaluation of mechanical properties. Nanocomposite formation occurs at higher loadings (3–5%) of expandable graphites but not for virgin or expanded graphite. Copyright © 2005 John Wiley & Sons, Ltd.     

Enhanced Fe(VI) cathode conductance and charge transfer: effects on the super-iron battery

Cathodes comprising Fe(VI) salts are capable of three-electron reduction, and are useful for the formation of energetic ‘super-iron’ batteries. Material additions to the Fe(VI) cathode can be used to enhance the conductance and the efficiency of charge transfer to the cathode, and control the characteristics of the electrochemical storage. Whereas several common carbons are ineffective as conductive matrices for Fe(VI) reduction, several others such as small particle (1 μm) graphite, compressed carbon black, and fluorinated polymer graphites support efficient Fe(VI) 3e⁻ reduction. Several inorganic salts also sustain Fe(VI) reduction, but at lower current densities. Titanates and other salts added to a K₂FeO₄ cathode improve the faradaic efficiency of Fe(VI) reduction at higher (∼3 mA cm⁻²) discharge current densities. Fluorinated polymer graphites provide an unusual additive to the Fe(VI) cathode mix, and at a low level (10 wt.%) addition can support efficient Fe(VI) reduction.     

In situ X‐ray Diffraction Studies of Cation and Anion Inter­calation into Graphitic Carbons for Electrochemical Energy Storage Applications

Graphite is a redox‐amphoteric intercalation host and thus capable to incorporate various types of cations and anions between its planar graphene sheets to form so‐called donor‐type or acceptor‐type graphite intercalation compounds (GICs) by electrochemical intercalation at specific potentials. While the LiC_x/C_x donor‐type redox couple is the major active compound for state‐of‐the‐art negative electrodes in lithium‐ion batteries, acceptor‐type GICs were proposed for positive electrodes in the “dual‐ion” and “dual‐graphite” cell, another type of electrochemical energy storage system. In this contribution, we analyze the electrochemical intercalation of different anions, such as bis(trifluoromethanesulfonyl) imide or hexafluorophosphate, into graphitic carbons by means of in situ X‐ray diffraction (XRD). In general, the characterization of battery electrode materials by in situ XRD is an important technique to study structural and compositional changes upon insertion and de‐insertion processes during charge/discharge cycling. We discuss anion (X^–) and cation (M⁺) intercalation/de‐intercalation into graphites on a comparative basis with respect to the M_x⁺C_n^– and C_n⁺X_n^– stoichiometry, discharge capacity, the intercalant gallery height/gallery expansion and the M–M or X–X in‐plane distances.     

The mosaic structure design to improve the anchoring strength of SiOx@C@Graphite anode

Silicon oxide (SiO_x)-based anodes have aroused great interest as the most promising alternative anode in the practical application of high-performance lithium-ion batteries. However, the electrochemical performance is inhibited because of the large volume change, and the electrode structure deteriorates during the cycling process, which hinders their practical application. In this article, a novel fabrication method for the synthesis of high-performance SiO_x@C@Graphite composites is presented. SiO_x particles are anchored on the graphite surface by chemical vapor deposition and compression molding. This structure makes up the shortcomings of poor electrical conductivity and poor bonding strength between SiO_x and graphite particles. It is beneficial to form a stable solid electrolyte interface and helps to maintain the structural integrity of electrode materials. As a result, the synthetic SiO_x@C@Graphite anode shows a high reversible capacity (2698.8 mA h), excellent cycle stability (about 76.9% capacity retention for 500 cycles) and a superior rate ability. Our research hopes to provide a new idea for improving the bonding strength of the surface coating.     

The preparation of porous graphite and its application in lithium ion batteries as anode material

Graphite is the most widely used anode material for lithium ion batteries (LIBs). However, the performance of graphite is limited by its slow charging rates. In this work, porous graphite was successfully prepared by nickel-catalyzed gasification. The existence of the pores and channels in graphite particles can greatly increase the number of sites for Li-ion intercalation-deintercalation in graphite lattice and reduce the Li-ion diffusion distance, which can greatly facilitate the rapid diffusion of lithium ions; meanwhile, the pores and channels can act as buffers for the volume change of the graphite in charging-discharging processes. As a result, the prepared graphite with pores and channels exhibits excellent cycling stability at high rate as anode materials for LIBs. The porous graphite offers better cycling performance than pristine graphite, retaining 81.4 % of its initial reversible capacity after 1500 cycles at 5 C rates. The effective synthesis strategy might open new avenues for the design of high-performance graphite materials. The porous graphite anode material is proposed in applications of high rate charging Li-ion batteries for electric vehicles.     

NCA三元锂离子电池分荷电状态循环的热特性和容量衰退研究

层状三元材料LiNi_0.8Co_0.15Al_0.05O₂（NCA）具有高能量密度和高比容量,在电动汽车领域占据重要地位.但是较差的容量保持率和热安全问题限制了其应用. 本文研究了18650型NCA/graphite（2.4 Ah）锂电池分区间循环容量衰退机理和热行为. 所考虑的荷电状态（state of charge,SOC）区间有0% ~ 20%（低）、20% ~ 70%（中）、70% ~ 100%（高）及0% ~ 100%（全）四个区间. 为了获得电池在不同SOC区间循环后衰减状况,以100个循环为一个周期,每个循环周期结束后,在25 ^oC下测试四个电池的基础特性,包括容量、容量增量（incremental capacity,IC）、电阻及电化学阻抗谱(electrochemical impedance spectroscopy, EIS),同时监测电池放电时的温度来讨论电池不同区间循环后的热行为. 测试结果表明,电池在全区间循环会降低电池寿命,而在非全区间循环的电池都能一定程度上减缓电池衰老的速度. 另外,全区间循环热特性最差而中端循环则表现出较好的热性能,对容量增量曲线分析发现,在高中低区间的性能衰退的主要原因是活性锂离子的损失,而在全区间还包括活性材料的损失和反应内阻的增大.     

Insights on the mechanism of Na-ion storage in expanded graphite anode

Currently,Na-ion battery(NIB) has become one of the most potential alternatives for Li-ion batteries due to the safety and low cost.As a promising anode for Na-ion storage,expanded graphite has attracted considerable attention.However,the sodiation-desodiation process is still unclear.In our work,we obtain expanded graphite through slight modified Hummer's method and subsequent thermal treatment,which exhibits excellent cycling stability.Even at a high current density of 1 A g^-1,our expanded graphite still remains a high reversible capacity of 100 mA h g^-1 after 2600 cycles.Furthermore,we also investigate the electrochemical mechanism of our expanded graphite for Na-ion storage by operando Raman technique,which illuminate the electrochemical reaction during different sodiation-desodiation processes.     

Exploiting Mechanistic Solvation Kinetics for Dual‐Graphite Batteries with High Power Output at Extremely Low Temperature

Improving the extremely low temperature operation of rechargeable batteries is vital to the operation of electronics in extreme environments, where systems capable of high‐rate discharge are in short supply. Herein, we demonstrate the holistic design of dual‐graphite batteries, which circumvent the sluggish ion‐desolvation process found in typical lithium‐ion batteries during discharge. These batteries were enabled by a novel electrolyte, which simultaneously provides high electrochemical stability and ionic conductivity at low temperature. The dual‐graphite cells, when compared to industry‐type graphite ∥ LiCoO₂ full‐cells demonstrated an 11 times increased capacity retention at ?60 °C for a 10 C discharge rate, indicative of the superior kinetics of the “dual‐ion” storage mechanism. These trends are further supported by galvanostatic intermittent titration technique (GITT) and electrochemical impedance spectroscopy (EIS) measurements at reduced temperature. This work provides a new design strategy for extreme low‐temperature batteries.     

四丁基六氟磷酸铵作为锂离子电池阻燃添加剂的研究

近年来关于锂离子电池造成的安全问题甚至事故的报道屡见不鲜,锂离子电池的安全问题已经成为人们关注的焦点. 我们用四丁基六氟磷酸铵（TBAPF₆）作为锂离子电池电解液阻燃添加剂,研究发现添加了TBAPF₆的电解液具有明显的阻燃效果,同时电解液电导率下降并不明显. LiCoO₂/Graphite全电池在添加了TBAPF₆的电解液中可逆容量会略有降低,但具有更优异的循环稳定性. 主要是由于TBAPF₆添加量的增加会影响石墨电极的库伦效率,延长活化时间. 通过对LiCoO₂/Graphite全电池绝热加速量热仪（ARC）测试,表明添加TBAPF₆对电池的燃烧有明显的抑制作用. 在TBAPF₆添加量至5%时,电池在300 ^oC内自放热速率不超过0.1^oC/min,电池的安全性显著提高.     

Untersuchungen zum Mechanismus der Intercalation von Antimonpentachlorid in das Graphitgitter

Studies on the Mechanism of the Antimony Pentachloride Intercalation in Graphite The SbCl₅ intercalation in graphite in liquid media (immersion in SbCl₅ and in SbCl₅/CCl₄-mixtures, respectively) reveals an induction period ranging from 0,25 up to 8 hours. Graphite intercalation by liquid SbCl₄F, SbCl₂F₃ and SbF₅ does not exhibit any induction period. The induction time of synthetic graphites is shorter than that of natural graphites. The decrease of graphite particle sizes as well as the increase of SbCl₅ concentration in CCl₄ solution and the presence of co-reagents (e.g. SbCl₃) reduce the induction time. Increasing the SbCl₅ concentration in CCl₄, an increase of SbCl₅ quantity in graphite and of identity period along c-axis in stage 2 have been found. Gase phase intercalation of SbCl₅ is a reaction of successive lowering of the stage index without any induction period. Using EPMA investigations it have been stated that nucleation at the prismatic edges (opening of galleries) controls the intercalation kinetics. An explanation of induction period and ?autocatalytic”? reaction after the induction period is given on basis of interaction of electrostatic forces, connected with adsorption of guest molecules, and elastic forces, resulting from dilatation during intercalation. Formation of complexes between SbCl₅ and co-reagents (e. g. SbCl₃) strengthens the electrostatic effect.     

Research progress of tunnel-type sodium manganese oxide cathodes for SIBs

Among the large energy storage batteries, the sodium ion batteries（SIBs） are attracted huge interest due to the fact of its abundant raw materials and low cost, and has become the most promising secondary battery. Tunnel-type sodium manganese oxides（TMOs） are industrialized cathode materials because of their simple synthesis method and proficient electrochemical performance. Na_0.44MnO₂（NMO） is considered the best candidate material for all tunnel-type structural materials. ...