新型AB5型氧化合金/碳复合材料作为锂离子电池负极性能研究

对回收的废旧镍氢(MH-Ni)电池负极材料AB5型储氢合金进行改性再利用,经过高温氧化处理和添加改性石墨制成复合材料后,用于高性能锂离子电池负极材料.通过X射线衍射(XBD)和电子显微镜(SEM)对材料进行了简单表征,采用恒电流充放电仪对材料进行电化学性能测试.实验结果表明,所制得的AB5型氧化合金/碳复合材料的首次充...     

基于树叶制备的多孔碳材料作为锂电池负极的应用试验

以树叶作为廉价易得的碳源,采用硼酸处理改善其电化学性能,并用氢氧化钾(KOH)进行活化提高材料比表面,以获得更多的储锂活性位。制备电池并对其进行测试。测试表明,活化材料作为锂电池的负极材料,具有较高的比容量,经过40次充放电循环后,仍然能够保持相当高的比容量,并且有着出色的大电流放电能力。因此,它作为锂离子电池的电极材料具有潜在的商业价值。     

烟草加热器具供能元器件的创新思考及展望

供能元器件作为烟草加热器具的核心部件，决定了烟草加热器具的续航时间、充放电速度、预热等待时间以及使用寿命等关键参数。本文综述了电加热型烟草制品加热器具的供能元器件发展现状，分析了2种供能元器件存在的不足与潜在的研究方向。结果显示，锂离子电池作为电加热型卷烟加热器具中普遍使用的供能元器件，具有体积能量密度高且电流放电量大的特点，但是存在充放电速度慢、循环稳定性差、成本高以及存在安全隐患等劣势；介电电容器是一种电加热型卷烟加热器具的潜在供能元器件，具有充放电速度快、循环稳定性好、可靠性高、价格低廉以及安全性能好等特点，但是其体积能量密度亟待提高。供能元器件是烟草加热器具中的关键单元，重视供能元器件的开发和研究、提高供能元器件的工作性能，对促进我国新型烟草的高质量发展以及提升消费者体验具有重要意义。     

碳热还原法制备锡-石墨复合材料及其性能表征

用碳热还原法制备了锡-石墨复合材料,通过XRD及SEM、恒流充放电循环、慢速扫描循环伏安和电化学阻抗测试等方法对其电化学嵌脱锂性能进行了研究. 结果表明,SnO2被石墨还原成金属Sn圆球颗粒,球粒平均尺寸4 mm,均匀分散,部分附着在片状石墨上. 该材料的首次嵌、脱锂比容量分别可以达到887和615 mA×h/g,库仑效率为69%,循环15次后的脱锂比容量为387 mA×h/g,高于石墨,容量保持率为63%,平均容量损失率为2.5%/次.     

Electrochemical performance of SiOC anodes prepared by a different silicone

SiOC is one of the most promising anodes for lithium-ion batteries, which shows the good structural stability and high capacity comparing to commercial graphite anode. In this paper, different SiOC anodes (SiOC-217, SiOC-H44, and SiOC-MK) were prepared from polymer precursors with different side groups (phenyl, methyl-phenyl, methyl) to investigate the effects of free carbon on the electrochemical performance of SiOC anodes. The results of X-ray photoelectron spectroscopy presented that SiOC was composed by different SiO_xC_4−x units and free carbon phase. The initial discharge capacity of SiOC-217 was 742.67 mA h g⁻¹. After 100 cycles, the reversible capacity of SiOC-217 reached 450.65 mA h g⁻¹ at 0.2 C, indicating a capacity retention rate of 60.68%. After cycling at high current densities, SiOC-217 exhibited a high discharge capacity of 592.88 mA h g⁻¹ at 0.1 C. SiOC-217 exhibited excellent electrochemical performance due to the high content of free carbon phase. Furthermore, the high contents of SiO₂C₂ and SiO₃C units further enhanced the improvement of electrochemical performance.     

Correlation of the irreversible lithium capacity with the active surface area of modified carbons

Negative electrodes of lithium-ion batteries are generally based on graphite. Higher storage capacities can be obtained with disordered carbons, however they demonstrate a noticeable hysteresis and irreversibility, which can preclude a practical application. In this paper, the main parameters which may affect the irreversible capacity are analyzed and we show that the irreversible lithium consumption which occurs at the negative carbon electrode during the first charge (C_irr) is proportional to the active surface area (ASA). Composites with a reduced ASA have been obtained after coating a hard carbon or milled graphite samples with a thin film of pyrolytic carbon. Deactivating the surface by pyrolytic carbon deposition allows the irreversible capacity to be noticeably reduced, being lower than in graphite, while the reversible capacity is 50% higher than in graphite. The electrochemical properties of this new C/C composite are investigated by galvanostatic cycling at various current densities and by impedance spectroscopy. The main effect of the dense carbon coating is to hinder the diffusion of solvated lithium ions to the active sites of the carbon host during the first discharge, giving rise to a moderate development of the Solid Electrolyte Interphase (SEI).     

Characterization of silicon- and carbon-based composite anodes for lithium-ion batteries

In recent years development of active materials for negative electrodes has been of great interest. Special attention has been focused on the active materials possessing higher reversible capacity than that of conventional graphite. In the present work the electrochemical performance of some carbon/silicon-based materials has been analyzed. For this purpose various silicon-based composites were prepared using such carbon materials as graphite, hard carbon and graphitized carbon black. An analysis of charging-discharging processes at electrodes based on different carbon materials has shown that graphite modified with silicon is the most promising anode material. It has also been revealed that the irreversible capacity mainly depends on the content of Si. An optimum content of Si has been determined with taking into account that high irreversible capacity is not suitable for practical application in lithium-ion batteries. This content falls within the range of 8-10 wt%.The reversible capacity of graphite modified with 8 wt% carbon-coated Si was as high as 604 mAh g⁻¹. The irreversible capacity loss with this material was as low as 8.1%. The small irreversible capacity of the material allowed developing full lithium-ion rechargeable cells in the 2016 coin cell configuration. Lithium-ion batteries based on graphite modified with silicon show gravimetric and volumetric specific energy densities which are higher by approximately 20% than those for a lithium-ion battery based on natural graphite.     

Advanced surface and microstructural characterization of natural graphite anodes for lithium ion batteries

Natural graphite powders were subjected to a series of thermal treatments to improve the anode irreversible capacity loss and capacity retention during long-term cycling of lithium-ion batteries. A baseline thermal treatment in inert Ar or N₂ atmosphere was compared to cases with a proprietary additive to the furnace gas. This additive substantially altered the surface chemistry of the uncoated natural graphite powders and resulted in significantly improved long-term cycling performance of the lithium ion batteries over the commercial, carbon-coated natural graphite baseline. Different heat-treatment temperatures were investigated ranging from 950 to 2900 °C to achieve the desired long-term cycling performance with a significantly reduced thermal budget. A detailed summary of the characterization data is also presented, which includes X-ray diffraction, X-ray photoelectron spectroscopy, Raman spectroscopy, and temperature-programmed desorption-mass spectroscopy. Characterization data was correlated to the observed capacity fade improvements over the course of long-term cycling at high charge–discharge rates in full lithium-ion cells. It is believed that the long-term performance improvements are a result of forming a more stable solid electrolyte interface (SEI) layer on the anode graphite surfaces, which is directly related to the surface chemistry modifications imparted by the proprietary gas environment during thermal treatment.     

中间相炭微球在锂离子电池负极材料的应用进展

中间相炭微球(MCMB)具有良好锂离子扩散性、导电性和机械稳定性等优势,是目前应用广泛、综合性能优异的锂离子电池负极材料,但较低理论比容量是制约其发展的关键因素。为了获得性能优良的MCMB基锂离子电池负极材料,改性修饰和复合材料已然成为目前研发重点。笔者论述了碳结构、表界面和复合材料等微观结构设计对MCMB负极材料电化学性能的影响。从碳堆积结构类型、有序性、层间距以及球体粒径大小等方面,论述了碳结构微观设计对MCMB电化学性能的影响。发现具有乱层结构的MCMB在充放电过程中内部产生应力较小,且碳结构较稳定,具有优异循环稳定性;内部具有大量微孔或碳层间距较大的MCMB,在充放电过程中可提高锂离子在电极中的迁移速率,并提供更多的储锂空间,一般具有优良的充放电比容量和倍率性能;小粒径MCMB具有较短的锂离子迁移路径和随之增加的比表面积,通常具有较好倍率性能,伴随着可逆比容量和充放电效率的衰减。从表界面碳层改性、包覆和掺杂改性等方面,论述了表界面改性对MCMB电化学性能的影响。表面碳层修饰可增加MCMB与电解液的相容性及其比表面积,提高了与电解液的接触面积及贮锂容量,改善了锂离子电池负极材料的电化学性能;另外,MCMB表面包覆一层无定型碳,可避免其表面与电解液直接接触,减少电化学副反应的产生,提升其可逆比容量。从碳活性物质复合材料、非碳活性物质复合材料等方面,论述了复合材料微观结构设计对MCMB电化学性能的影响。碳活性物质可降低MCMB内部碳层结构的有序性,减少锂离子嵌入过程中的内部应力,提升MCMB循环稳定性。非碳活性物质诱导MCMB生成更加有序的碳层结构,提高MCMB的比表面积,从而改善MCMB表面与电解液分子的接触能力及其嵌锂性能,有利于提升MCMB负极材料可逆比容量、循环性能和倍率性能。MCMB具有高碳层间距和多缺陷位点等结构特征,有利于钠离子自由脱嵌,应用于钠离子电池时具有良好的可逆比容量、循环稳定性和倍率性能。MCMB的不规则定向层状结构经活化等处理具有较高比表面积,可应用于超级电容器电极材料。最后提出在高性能锂离子电池电极材料快速发展的需求下,从微观结构角度设计MCMB纳米复合材料将是MCMB负极材料的研究重点。     

掺杂型尖晶石LiMn_(2-x)Mg_xO_(3.97)F_(0.03)(x=0.05,0.1)的合成与性能研究

采用"熔融浸渍法"合成了Mg和F共掺杂的不同温度下的锂离子电池正极材料Li Mn2-xMgxO3.97F0.03(x=0.05,0.1);煅烧温度为700,750和800°C。通过XRD对样品进行测试,样品为单一尖晶石结构的物相;并用SEM测试,对样品进行了形貌研究。用所制备的材料作为正极材料组装了模拟锂离子电池;在室温下进行恒电流充-放电性能测试,测试条件为3.3~4.3 V和0.2mA/cm2电流密度。随着材料制备温度的升高,电池的初始放电容量有逐渐增加的趋势,但充放电循环的容量损失也逐渐增加;氟掺杂量一定,镁掺杂量较多时,对应温度下煅烧的样品的结晶程度较好,样品的电化学性能也较好。在800下°C样品Li Mn1.9Mg0.1O3.97F0.03初始容量高达108 mAh/g,60次充放电循环后,其容量保持率高达81%,具有优良的循环稳定性能。     

Electrochemical characteristics of copper silicide-coated graphite as an anode material of lithium secondary batteries

Copper silicide-coated graphite as an anode material was prepared by the sequential employments of plasma enhanced chemical vapor deposition (PECVD) and radio frequency magnetron sputtering (RFMS) method at 300 °C. The silicon-coated graphite exhibited an initial discharge capacity of 540 mAh/g with 76% coulomb efficiency, and the discharge capacity was sharply decreased down to 50% of initial capacity after 30 cycles, probably due to large volume changes during the charge-discharge cycling. Copper silicide-coated graphite, however, exhibited an initial discharge capacity of 480 mAh/g with higher retention capacity of 87% even after 30 cycles, probably due to the enhanced interfacial conductivity. The copper silicide film on the graphite surface played as the active anode material of lithium secondary batteries via the reduction of interfacial resistance and mitigation of volume changes during repeated cycles.     

Rate capability of graphite materials as negative electrodes in lithium-ion capacitors

The lithium-ion exchange rate capability of various commercial graphite materials are evaluated using galvanostatic charge/discharge cycling in a half-cell configuration over a wide range of C-rates (0.1-60 C). The results confirm that graphite is capable of de-intercalating stored charge at high rates, but has a poor intercalating rate capability. Decreasing the graphite coating thickness leads to a limited rate performance improvement of the electrode. Reducing the graphite particle size shows enhanced C-rate capability but with increased irreversible capacity loss (ICL). It is demonstrated that the rate of intercalation of lithium-ions into the graphite is significantly limited compared with the corresponding rate of de-intercalation at high C-rates. For the successful utilisation of commercially available conventional graphite as a negative electrode in a lithium-ion capacitor (LIC), its intercalation rate capability needs to be improved or oversized to accommodate high charge rates.     

Exploration of artificial neural network [ANN] to predict the electrochemical characteristics of lithium-ion cells

CoO anode, as an alternate to the carbonaceous anodes of lithium-ion cells has been prepared and investigated for electrochemical charge-discharge characteristics for about 50 cycles. Artificial neural networks (ANNs), which are useful in estimating battery performance, has been deployed for the first time to forecast and to verify the charge-discharge behavior of lithium-ion cells containing CoO anode for a total of 50 cycles. In this novel approach, ANN that has one input layer with one neuron corresponding to one input variable, viz., cycles [charge-discharge cycles] and a hidden layer consisting of three neurons to produce their outputs to the output layer through a sigmoid function has been selected for the present investigation. The output layer consists of two neurons, representing the charge and discharge capacity, whose activation function is also the sigmoid transfer function. In this ever first attempt to exploit ANN as an effective theoretical tool to understand the charge-discharge characteristics of lithium-ion cells, an excellent agreement between the calculated and observed capacity values was found with CoO anodes with the best fit values corresponding to an error factor of <1%, which is the highlight of the present study.     

锂在负极材料中的扩散行为对其大倍率充放电性能的影响

采用恒电位阶跃的方法,对锂在锂离子电池负极材料中的扩散系数进行测量,对天然石墨和中间相炭微球两种负极材料进行了大倍率充放电性能测试。结果表明,锂在两种负极材料中的扩散系数是不同的,锂在天然石墨中的扩散系数较小,只有1.90×10-11cm2/s,而锂中间相炭微球中的扩散系数较大,达4.25×10-9cm2/s,扩散系数大,电极的大电流充放电性能好,天然石墨在5 C放电下放电平台升高到0.3 V,放电容量急剧减小,而中间相炭微球在5 C放电下仍能保持0.2 V左右的放电平台,放电容量保持在234 mA.h/g。     

铁锗合金负极的限域封装及锂离子存储性能

锂离子电池商用负极石墨由于低的理论比容量（372 mA·h/g）无法满足日益增长的高能量密度需求。锗负极材料凭借更高的理论比容量（约为1 600 mA·h/g）被认为是一种很有前途的材料。但锗基负极材料在充放电过程中存在巨大的体积变化,使得其电化学性能差。因此,设计并制备了一种独特的锗基复合材料,该材料的合成首先采用溶剂热法制备有机-无机杂化Ge-Fe-O_x/EDA纳米线,接着进行多巴胺包覆,随后通过高温焙烧在内部原位生成FeGe/FeGe₂合金相和表面形成碳包覆,从而制得了限域封装的Ge/FeGe/FeGe₂@C纳米线铁锗合金负极。这种独特的结构有效提升锗负极材料的导电性和抑制体积变化,因此复合材料展现出优异的倍率性能（当电流密度为5 A/g时,放电比容量为450 mA·h/g）和良好的长循环稳定性（在电流密度为1 A/g条件下循环400圈后,放电比容量为547 mA·h/g）。     

Strategy for improving the capacity and rate performance of LiNixCoyMn1−x−y electrode using Ti3C2Tx MXene additives

With the expanding range of applications for lithium-ion batteries, a great deal of research is being conducted to improve their capacity, stability, and charge/discharge rates. This study was performed to investigate the effects of MXene, which has a large surface area and metallic conductivity, as a conductive additive to the cathode, on electrochemical performance. The two-dimensional material MXene constructs a conductive network with zero-dimensional carbon black in plane-to-point mode to improve conductivity and contact area with active materials, thereby facilitating fast charge transfer. The conductive network reduces the internal resistance and polarization of the cathode and aids the diffusion of electrons. The electrode containing an appropriate amount of MXene showed improved rate performance, high discharge capacity (123.9 mAh g⁻¹ at 4 C), and excellent cycle stability at a high scan rate (125.8 mAh g⁻¹ at 2 C after 150 cycles) compared to pristine electrodes. Based on these results, Ti₃C₂T_x MXene is a promising conductive additive in the battery field.     

Graphene/nanosized silicon composites for lithium battery anodes with improved cycling stability

Graphene/nanosized silicon composites were prepared and used for lithium battery anodes. Two types of graphene samples were used and their composites with nanosized silicon were prepared in different ways. In the first method, graphene oxide (GO) and nanosized silicon particles were homogeneously mixed in aqueous solution and then the dry samples were annealed at 500 °C to give thermally reduced GO and nanosized silicon composites. In the second method, the graphene sample was prepared by fast heat treatment of expandable graphite at 1050 °C and the graphene/nanosized silicon composites were then prepared by mechanical blending. In both cases, homogeneous composites were formed and the presence of graphene in the composites has been proved to effectively enhance the cycling stability of silicon anode in the lithium-ion batteries. The significant enhancement on cycling stability could be ascribed to the high conductivity of the graphene materials and absorption of volume changes of silicon by graphene sheets during the lithiation/delithiation process. In particular, the composites using thermally expanded graphite exhibited not only more excellent cycling performance, but also higher specific capacity of 2753 mAh/g because the graphene sheets prepared by this method have fewer structural defects than thermally reduced GO.     

Dissolution-regrowth synthesis of SiO2 nanoplates and embedment into two carbon shells for enhanced lithium-ion storage

In this work, SiO_2 nanoplates with opened macroporous structure on carbon layer(C-mSiO_2) have been obtained by dissolving and subsequent regrowing the outer solid SiO_2 layer of the aerosol-based C-SiO_2 double-shell hollow spheres. Subsequently, triple-shell C-mSiO_2-C hollow spheres were successfully prepared after coating the Cm SiO_2 templates by the carbon layer from the carbonization of sucrose. When being applied as the anode material for lithium-ion batteries, the C-mSiO_2-C triple-shell hollow spheres deliver a high capacity of 501 mA ·h·g~(-1) after100 cycles at 500 m A·g~(-1)(based on the total mass of silica and the two carbon shells), which is higher than those of C-mSiO-12(391 m A·h·g~(-1)) spheres with an outer porous SiO_2 layer, C-SiO_2-C(370 m A·h·g) hollow spheres with a middle solid SiO_2 layer, and C-SiO_2(319.8 m A·h·g~(-1)) spheres with an outer solid SiO_2 layer. In addition,the battery still delivers a high capacity of 403 m A·h·g~(-1) at a current density of 1000 m A·g~(-1) after 400 cycles.The good electrochemical performance can be attributed to the high surface area(246.7 m~2·g~(-1)) and pore volume(0.441 cm~3·g~(-1)) of the anode materials, as well as the unique structure of the outer and inner carbon layer which not only enhances electrical conductivity, structural stability, but buffers volume change of the intermediate SiO_2 layer during repeated charge–discharge processes. Furthermore, the SiO_2 nanoplates with opened macroporous structure facilitate the electrolyte transport and electrochemical reaction.     

Electrochemical properties of heat-treated polymer-derived SiCN anode for lithium ion batteries

Silicon-carbon-nitrogen material (SiCN) is pyrolyzed from polysilylethylenediamine (PSEDA) derivation, followed by a heat-treating process at 1000 °C in Ar atmosphere. This heat-treated SiCN material has an excellent electrochemical performance as an anode for lithium ion batteries. Charge-discharge cycle measurements show that the heat-treated SiCN material exhibits a high first cycle discharge capacity of 829.0 mAh g⁻¹ and stays between 400 and 370 mAh g⁻¹ after 30 cycles. The discharge capacity remains above 300 mAh g⁻¹ at the high current density of 80 and 160 mA g⁻¹. These values are higher than untreated SiCN and commercial graphite anodes, which indicates that the heat-treating process improves the charge-discharge capacity, cycle stability and high-rate ability of SiCN anode. It is seemed that changes of SiCN structure, the formation of loose nano-holes on material surface and the formation of graphitic carbon phase in heat-treating process contribute to the improvement of electrochemical properties for SiCN anode.     

钇掺杂钛酸锂/石墨烯纳米复合材料的合成与电化学性能

以氧化石墨烯（GO）为基底，钛酸四丁酯、一水合氢氧化锂、六水合硝酸钇为原料，十六烷基三甲基溴化铵为表面活性剂，采用溶剂热法合成前驱体，在N2气氛保护下高温煅烧合成了钇掺杂钛酸锂/氧化石墨烯纳米复合材料。采用SEM、XRD、EDS、Raman对复合材料进行了形貌、结构和成分表征。将复合材料用作锂离子电池负极材料，采用循环伏安法、恒流充放电循环法研究了其电化学性能。结果表明，片状钛酸锂包覆在氧化石墨烯片上形成了钇掺杂钛酸锂/氧化石墨烯纳米复合材料。在100 mA/g的电流密度下，钇掺杂量为8%（以钛酸锂的物质的量为基准，下同）的纳米复合材料的首次放电比容量为145.5mA·h/g，经过100圈充放电循环后容量衰减几乎为0，经过200圈循环后容量衰减1.59%，经过300圈循环后容量衰减3.24%，与目前容量保持率只有80%左右的石墨负极相比有明显的改进。钇元素的掺杂和钛酸锂包覆氧化石墨烯形式的复合材料可以减小钛酸锂电极在充放电循环中的极化程度，从而改善了材料的循环性能。