The feasibility for natural graphite to replace artificial graphite in organic electrolyte with different film-forming additives

The feasibility for natural graphite(NG)to replace artificial graphite(AG)in organic electrolytes with different additives are investigated.Although the strong film-forming additives contributes to form robust solid electrolyte interphase(SEI)film on graphite particle surface,great differences in gas evolution,lithium inventory loss and other side reactions are observed.Lithium bis(oxalato)borate(Li BOB)and fluoroethylene carbonate(FEC)are found more effective and the combination shows to be more promising.In the optimized electrolyte,natural graphite anode exhibits excellent long-term cycling capability.After 800 cycles at high temperature,the capacity retention is comparable to that using artificial graphite.The mechanisms for the capacity-fading of the full cells with AG and NG anode are investigated by ICP,SEM and polarization studies.The results shows that NG electrode consumes more active lithium due to the rough surface and larger volume expansion.The rapid capacity-fading in the initial 100 cycles is related to the instability of the SEI film aroused from large volume expansion.The systematic analysis is inspiriting for the development of high performance lithium ion batteries with reduced cost.

Investigations on the Performance of the Blending Natural and Artificial Graphite for Lithium ion Battery

In this work,it was found that the improved battery performance such as thermal stability and cycle performance with the blending of nature and artificial graphite.

Homogeneous distributed natural pyrite-derived composite induced by modified graphite as high-performance lithium-ion batteries anode

Natural minerals-based energy materials have attracted enormous attention because of the advantages of good materials consistency,high production,environmental friendliness,and low cost.The uniform distribution of grains can effectively inhibit the aggregation of active materials,improving lithium storage performance.In this work,natural graphite is modified by polyvinylpyrrolidone to obtain modified graphite with reduced size and better dispersion.Natural pyrite composite polyvinylpyrrolidone-modified graphite(pyrite/PG)material with uniform particle distribution is obtained by the ball milling process.The subsequent calcination process converts pyrite/PG into Fe_(1-x)Scompounded with polyvinylpyrrolidone-modified graphite(Fe_(1-x)S/PG).The homogeneous grain distributions of active material can facilitate the faster transfer of electrons and promote the efficient utilization of active materials.The as-prepared Fe_(1-x)S/PG electrode exhibits a remarkably reversible specific capacity of 613.0 mAh·g^(-1)at 0.2 A·g^(-1)after 80 cycles and an excellent rate capability of 523.0 mAh·g^(-1)at 5 A·g^(-1).Even at a higher current density of 10 A·g^(-1),it can deliver a specific capacity of 348.0 mAh·g^(-1).Moreover,the dominant pseudocapacitance in redox reactions accounts for the impressive rate and cycling stability.This work provides a low-cost and facile method to fabricate natural mineral-based anode materials and apprise readers about the impact of uniform particle distribution on lithium storage performance.

Cost-effective natural graphite reengineering technology for lithium ion batteries

Graphite tailings produced by natural graphite is usually regarded as garbage to be buried underground,which would result in a certain waste of resources.Here,in order to explore the utilization of natural graphite tailings(NGT),a liquid-polyacrylonitrile(LPAN)is used to modify the NGT fragments and aggregate them together to form secondary graphite particles with low surface area and high tap density.Moreover,the modified NGT show much better electrochemical performances than those of original one.When tested in full cells coupled with NMC532 cathode,the material achieves a high rate capability and cycle stability at the cutoff voltage of 4.25 V as well as 4.45 V,which maintains 84.32%capacity retention after 500 cycles at 1 C rate(4.25 V),higher than that of the pristine one(73.65%).The enhanced performances can be attributed to the use of LPAN to create a unique carbon layer upon graphite tailings to reconstruct surface and repair defects,and also to granulate an isotropic structure of secondary graphite particles,which can help to weaken the anisotropy of Li^(+)diffusion pathway and form a uniform,complete and stable solid-electrolyte-interface(SEI)on the surface of primary NGT fragments to promote a fast Li+diffusion and suppress lithium metal dendrites upon charge and discharge.

Natural gas consumption forecasting model based on coal-to-gas project in China

Natural gas is widely used because it is environmentally friendly,particularly in reducing carbon emission and improving the Air Quality Index(AQI)around densely populated cities.China has initiated a coal-to-gas project(CGP)to improve the air quality in northern China.As a subcompany of China National Petroleum Corporation,PetroChina Natural Gas Marketing North Company has been focusing on natural gas resource allocation while considering numerous issues such as ensuring the bottom line of livelihood requirements in winter and the performance of economic indicators for an entire calendar year in the northern part of China.Therefore,the accurate prediction of natural gas consumption is important to PetroChina Natural Gas Marketing North Company.It has become a challenge to forecast natural gas consumption because the natural gas market has changed considerably because of the CGP.Natural gas consumption cannot be forecasted using conventional models.This study analyzes the characteristics of the CGP based on the data obtained from rural individual users and company users.Based on the analysis,the gas consumption in winter is predicted using two different forecasting approaches.The methods presented in this paper provide a basis for formulating effective measures for natural gas scheduling in the northern part of China.

Experimental study on the oxidation behavior and microstructural evolution of NG-CT-10 and NG-CT-20 nuclear graphite

NG-CT-10 and NG-CT-20 are newly developed grades of nuclear-grade graphite from China.In this study,their oxidation behaviors were experimentally investigated using thermal gravimetric analysis.Microstructural evolution before and after oxidation was investigated using scanning electron microscope,mercury intrusion,and Raman spectroscopy.The apparent activation energy of NG-CT-10 nuclear graphite is 161.4 kJ/mol in a reaction temperature range of 550–700℃and that of NG-CT-20 is 153.5 kJ/mol in a temperature range of 550–650℃.The activation energy in the inner diffusion control regime is approximately half that in the kinetics control regime.At high temperatures,the binder phase is preferentially oxidized over the filler particles and small pores are generated in the binder.No new large or deep pores are generated on the graphite surfaces.Oxygen can diffuse along the boundaries of filler particles and through the binder phase,but cannot diffuse into the spaces between the nanocrystallites in the filler particles.Filler particles are oxidized starting at their outer surfaces,and the sizes of nanocrystallites do not decrease following oxidation.

Modified graphite filled natural rubber composites with good thermal conductivity

The rubber composites with good thermal conductivity contribute to heat dissipation of tires. Graphite filled natural rubber composites were developed in this study to provide good thermal conductivity. Graphite was coated with polyacrylate polymerized by monomers including methyl methacrylate, n-butyl acrylate and acrylic acid. The ratios between a filler and acrylate polymerization emulsion and those between monomers were varied. Eight types of surface modification formulas were experimentally investigated. Modification formula can affect coating results and composite properties greatly. The best coating type was achieved by a ratio of1:1 between methyl methacrylate and n-butyl acrylate. The coating of graphite was thermally stable in a running tire. Filled with modified graphite, the tire thermal conductivity reached up to 0.517–0.569 W·m-1·K-1. In addition, the mechanical performance was improved with increased crosslink density, extended scorch time and short vulcanization time.

Carbide derived carbon electrode with natural graphite addition in magnesium electrolyte based cell for supercapacitor enhancements

Herein,we have presented a supercapacitor based on carbide derived carbon（CDC） electrode with natural graphite（NG） addition.The capacitor was analyzed at 22°C by cyclic voltammetry,galvanostatic charge-discharge and impedance techniques using a 0.5 mol/L of magnesium（II）bis（trifluoro methanesulfonyl） imide（Mg TFSI） in ethylene carbonate-propylene carbonate（EC ：PC = 1 ：1,v/v） as electrolyte.The results conclude that the CDC cell enhancements have been proven by the composite electrode（5%–30% NG to CDC） especially on the cell efficiency and voltage i.e.,the CDC cell around 2.5 V limit was improved.An obtainable specific capacitance,real power and energy density are 15 F g-1,1.2 k W kg-1and 15 Wh kg-1,respectively.

A Novel Modification Approach for Natural Graphite Anode of Li-ion Batteries

To improve the rate capability and cyclability of natural graphite anode for Li-ion batteries,a novel modification approach was developed.The modification approach included two steps:(a)high-energy ball milling in a rotary autoclave containing alumina balls,H_3PO_4 and ethanol;(b)coating with pyrolytic carbon from phenlic resin.The treated graphite shows obvious improvement compared with the original natural graphite in electrochemical properties such as cyclability and rate capability,especially at high current density.The primary reasons leading to the improvement in rate capability and cyclability are that the diffusion impedance of Li^+ in graphite is reduced due to the fact that P filtered into graphite layers can mildly increase interlayer distances,and the fact that the structural stability of graphite surface is enhanced since the coated pyrolytic carbon can depress the co-intercalation of solvated lithium ion.

The influence of composition of asphaltenes of different genesis on the properties of carbon materials manufactured from them by plasma processing

The results of experimental studies of carbon materials, which are formed in the plasma of a direct current (DC) arc discharge initiated in open air from the asphaltenes of different origins, extracted from the natural asphaltite and from the oil of the Sredne-Ugutskoye Oilfield, are presented. The influence of the initial asphaltene composition on the composition and properties of the resulting carbon materials is analyzed. The initial asphaltenes and the samples of the carbon materials are characterized by the methods of X-ray diffraction, differential thermal analysis, X-ray fluorescence analysis, IR-Fourier spectroscopy, laser diffraction, transmission and scanning electron microscopy. The changes in the composition and structure of the asphaltenes are determined before and after their plasma treatment and the hypotheses are put forward concerning the chemical processes causing the changes in the molecular structure of the samples. As a result of plasma treatment of asphaltenes (100 A, 30 s), it was shown that graphitization occurs, as well as oxidation, and a decrease in sulfur content. Moreover, nanotubes and nano-onions have been detected using electron microscopy. Petroleum asphaltenes after plasma treatment give a less thermostable carbon material, but with a lower content of heteroatoms, and with a large amount of sulfur in the composition of sulfoxide structural fragments. This method is shown to be a promising technology for processing the petroleum feedstock enriched with heavy asphaltene components for the manufacture of carbon nanomaterials: nanotubes, nano-onions and polyhedral graphite.

2025-2035年中国天然石墨资源需求预测

天然石墨广泛应用于传统工业和战略性新兴产业,是支撑我国高新技术发展的重要原材料。本文论述了我国天然石墨资源现状,并通过分析天然石墨主要消费部门需求,预测了未来耐火材料、铸造、铅笔、密封材料、摩擦材料、润滑吸附材料、锂电池负极材料等产业对天然石墨的需求。研究发现:我国天然石墨资源丰富,未来需求量将快速增长,预计到2025年、2030年、2035年我国天然石墨的需求量将分别达到109.0万t、188.3万t和278.3万t。全球天然石墨供给侧正在重塑,我国在全球天然石墨产业链供应链中的地位正在下降。我国石墨消费重心正从传统产业向战略性新兴产业转移,高端石墨产业发展面临机遇,为天然石墨产业发展带来新的增长点。通过健全天然石墨产业链和加强天然石墨资源保护力度,使我国从石墨资源大国发展成为石墨资源强国,支撑我国未来在新能源、关键装备密封润滑材料、高温材料等高端领域的石墨产品需求发展。

不同地区天然石墨球形化制备负极材料

天然鳞片石墨是制备锂离子电池负极材料的优质原料,本试验以鸡西、内蒙古、萝北3个地区固定碳含量(质量分数)约为95%的石墨精矿为原料,依次进行球形化整形和化学提纯,制备高纯球形石墨,并对高纯球形石墨进行了电化学性能测试。结果表明,经过球形化后,3个地区球形石墨振实密度分别为0.96 g/cm^(3)、0.94 g/cm^(3)、0.98 g/cm^(3),其中萝北石墨振实密度最高,成球率为41.44%。较优混酸提纯工艺为:混酸与石墨的液固比为3 mL/g,HF体积分数为30%,反应时间为6 h,反应温度为70℃,经混酸提纯处理后,3个地区球形石墨固定碳含量分别提高至99.90%、99.88%、99.97%。电化学性能测试结果表明,3个地区石墨负极材料的首次充放电效率均大于90%,首次放电容量均高于360 mAh/g,是制备天然石墨负极材料的理想原料。

高导热多孔石墨预制体的制备及其性能

以天然鳞片石墨、酚醛树脂以及中间相碳微球为主要原料,制备多孔石墨预制体,经石墨化处理后再与环氧树脂复合,获得高导热石墨/环氧树脂复合材料。研究了素坯成形密度和粉末组成对多孔石墨预制体X-Y方向的导热性能与孔隙率的影响。结果表明:预制体内部石墨片定向排列,酚醛树脂与中间相碳微球连接其间,形成定向多孔网络结构,实现高导热、高孔隙与大孔径的协同。当素坯成形密度为1.4 g/cm^(3),天然鳞片石墨、酚醛树脂、中间相碳微球的含量分别为67.5 mass%、17.5 mass%和15 mass%时,多孔石墨预制体X-Y方向导热性能达到286.97 W/(m·K),气孔率达到44.56%;此时,石墨/环氧树脂复合材料X-Y方向导热性能达到116.81 W/(m·K)、抗压强度为26 MPa,在电子封装领域具有潜在的应用前景。

水热法制备碳纳米球修饰天然石墨材料CNS@NG

为改善石墨作为电极材料的性能,以葡萄糖和球形天然石墨为原料,采用水热法合成了碳纳米球修饰天然石墨材料CNS@NG。应用X射线衍射、扫描电子显微镜和拉曼光谱对样品的微观结构、形貌和组成进行表征。结果表明,由葡萄糖水热及碳化处理后形成的碳纳米球均匀地分布在球形天然石墨表面,所制备的合成材料样品较好地保持了天然石墨的晶体结构,表现出碳与石墨复合材料的拉曼特征,具有较好的稳定性。

利用SSR标记对家蚕卵非胶着性基因(Ng)的定位分析

家蚕卵非胶着性基因(No-glue,Ng)位于第12染色体,Ng突变体的雌性成虫生殖器的粘液腺只分泌极少量的粘性物质,因此产下的卵不能粘着而成为天然散卵,是研究家蚕粘液蛋白分泌机制的重要材料。利用雌性家蚕的W染色体和Z染色体间不发生交换的特点,采用产胶着卵的家蚕品系KY和产非胶着卵的家蚕品系巴格达特(Ba)组配正反交群体(Ba×KY)F1♀×KY♂和KY♀×(Ba×KY)F1♂2种材料,分别记作BC1F和BC1M,根据已经构建的家蚕SSR分子标记连锁图谱对Ng基因进行连锁分析及定位。BC1F群体中的所有产非胶着卵的个体均表现出与(Ba×KY)F1相同的杂合型带型;而所有产胶着卵个体的带型与亲本KY一致,为纯合型。筛选出4个与Ng基因连锁的SSR标记,并利用BC1M群体构建Ng基因的SSR标记遗传连锁图,连锁图的遗传距离为51.9cM,与Ng基因最近的引物为S1213,图距为0cM。

表面包覆碳层孔隙对石墨负极材料倍率性能的影响

为了研究表面包覆碳层孔隙对石墨负极材料倍率性能的影响,引入少量硼酸,在包覆沥青软化阶段形成硼酸气化逸出效应,再通过碳化工艺在天然石墨尾料表面形成具有一定孔隙的包覆碳层,得到具有不同比例孔隙的石墨负极材料。结果表明,硼酸在材料颗粒表面形成了含有孔隙的碳层,其孔隙类型为介孔和大孔;表面碳层中的介孔比例越高,碳层L_(C)中形成Li^(+)的扩散通道数量越多,Li^(+)的扩散阻抗越低,材料倍率性能及循环性能得以改善。

The evolution of coal, examining the transitions from anthracite to natural graphite: a spectroscopy and optical microscopy evaluation

Coal-derived natural graphite(CDNG)has multiple industrial applications.Here,ten metamorphic coals from anthracite to CDNG were obtained from Lutang and Xinhua in the Hunan Province and Panshi in the Jilin Province.Bulk characterization(proximate and ultimate analyses,X-Ray powder diffraction(XRD),and powder Raman spectroscopy),along with optical microscopy,scanning electron microscope(SEM)and micro-Raman spectroscopy were utilized to examine the transitions from anthracite to semi-graphite to CDNG.The XRD and Raman spectroscopy data indicate that from anthracite to highly ordered graphite the average crystal diameter(La)and height(Lc)increased from 6.1 and 4.6 nm to 34.8 and 27.5 nm,respectively.The crystalline parameters of the CDNG samples from Panshi and Lutang varied slightly when closer to the intrusive body.Optical microscopy and SEM indicated that in the anthracite samples there were thermoplastic vitrinite,devolatilized vitrinite,and some“normal”macerals.In the meta-anthracite,pyrolytic carbon,mosaic structure,and crystalline tar were present.In the CDNG there were flake graphite,crystalline aggregates,and matrix graphite.The crystalline aggregates show the highest structural ordering degree as determined from Raman spectral parameters(full-width at half maxima(G-FWHM)~20 cm^(−1),D1/(D1+D2+G)area ratio(R2)value<0.5).The flake graphite is less ordered with G-FWHM~28 cm^(−1) and 0.5<R2<1,but a larger grain size(up to 50μm).The mosaic structures were likely the precursors of the matrix graphite through in situ solid-state transformation.The pyrolytic carbon and crystalline tars are the transient phase of gas-state and liquid-state transformations.This study is beneficial to realize the rational utilization of CDNG.

Processing Compressed Expanded Natural Graphite for Phase Change Material Composites

Phase change materials(PCMs)are used in various thermal energy storage applications but are limited by their low thermal conductivity.One method to increase conductivity involves impregnating organic PCMs into highly porous conductive matrix materials.Of these materials,compressed expanded natural graphite(CENG)matrices have received the most attention.Despite this attention,the effect that CENG processing has on PCM saturation and overall matrix thermal conductivity has not been fully investigated.Therefore,the effect of the heat treatment process used to expand intercalated graphite flakes is evaluated here.Higher heat treatment temperatures yielded higher saturation rates and overall saturation at similar matrix porosities.For example,increasing temperature from 300℃to 700℃resulted in approximately 60%-70%increase in pore saturation after 100 minutes of soaking.The exposure time to heat treatment had less of an effect on PCM saturation.The exposure time had negligible effect above 30 min and above 500℃heating temperatures.However,because the expanded graphite was found to oxidize around 700℃,the use of longer exposure time in manufacturing applications can be beneficial if a shortened impregnation time is needed.Heat treatment conditions did not impact thermal conductivity.The composite latent heat of fusion was also reduced approximately proportionally to the PCM mass fraction.A local maximum in axial thermal conductivity was observed at around 83%porosity,which is similar to previous studies.The observed conductivity at this maximum was a factor of 81 times greater than the conductivity of the PCM.

Technical and Economic Aspects and Experience from 6 Years of Operating the Technology Using the Waste Heat from the Exhaust Gases of Heat Sources and 3 Years of Operating a Heating Plant in an Autonomous, Island Regime

This article is focused on technical and economic evaluation of more than 6-years experiences of operating the Waste Heat Recovery technology—the manner and system of flue gas processing generated in the combustion process in heat & power plants, cogeneration units, etc., which burn the gaseous fuel, primarily natural gas, or methane, biogas, geothermal gas, or other gaseous mixtures containing hydrogen. The solution proposes a more effective and non-traditional use of gaseous fuel for heating, the flue gases of which are processed in order to extract additional utilisable heat, with potential elimination of CO2 from them. Deploying of the heating plant in an island regime (OFF-GRID) enables definition of the benefits brought by the 3 years of operational experience and presents visions for the future offering the possibility to utilise the support energy services at the municipal as well as regional level.

Influence of particle structure on electrochemical character of composite graphite

The natural graphite has been used as the anode material for Lithium-Ion batteries, because of its low cost, chemical stability and excellent reversibility for Li+ insertion. However, the slow diffusion rate of lithium ion and poor compatibility with electrolyte solutions make it difficult to use in some conditions. In order to solve these problems, an epoxy-coke/graphite composite has been manufactured. The particle of composite carbonaceous material coated on non-graphitizable (hard) carbon matrix. Due to the disordered structure, the diffusion rate of lithium species in the non-graphitzable carbon is remarkably fast and less anisotropic. The process for preparing a composite carbon powder provides a promising new anode material with superior electrochemical properties for Li-ion batteries. The unique structure of epoxy-coke/graphite composite electrodes results in much better kinetics, also better recharge ability and initial charge/discharge efficiency.