高活性Mn_2O_3制备尖晶石LiMn_2O_4及其性能研究

尖晶石LiMn_2O_4是当前最具研究价值的锂离子电池正极材料之一。采用碳酸锰热解法制备高活性Mn_2O_3粉末作为尖晶石LiMn_2O_4的前驱体,探究锰锂比对高温固相法合成尖晶石LiMn_2O_4的影响。利用热重分析(TG-DSC)及热力学分析确定碳酸锰热解制备前驱体高活性Mn_2O_3的最佳热解条件:热解温度为600℃时,制备出结晶性能良好、无杂质、分散均匀的Mn_2O_3粉末。通过X射线衍射(XRD)、扫描电镜(SEM)和电化学测试对尖晶石LiMn_2O_4的结构、形貌和电化学性能进行表征。结果表明,随着锂锰比增加,产物的结构、形貌和电化学性能均有所改善和提高。锂源的添加量决定了尖晶石LiMn_2O_4结构、形貌,当Mn∶Li=2. 0∶1. 2时,尖晶石LiMn_2O_4样品的结晶形态完善,表面光滑,颗粒均匀,且无杂质;在0. 5C下,其首次充电比容量达到117. 6 mAh·g~(-1),放电比容量为114. 8 mAh·g~(-1)。循环100周后容量保持率达到91. 8%。在高倍率放电下,仍保持较高的放电比容量和较好的循环性能。     

由无定形Li-Mn-Co-Ti-O前驱体制备改性尖晶石锰酸锂

对水热法合成的无定形Li-Mn-Me-O前驱体(Me=0、Co或Co-Ti)进行热处理,制备了Co掺杂及Co-Ti复合掺杂的尖晶石型LiMn_2O_4正极材料。通过XRD、SEM对Co-Ti复合掺杂的LiMn_2O_4的结构和微观形貌进行分析与表征,并测试了其电化学性能。研究结果表明:所制备的粉体材料具有良好的立方尖晶石结构,无杂相峰存在;Co-Ti复合掺杂使LiMn_2O_4颗粒变小;其在3.0~4.3 V电压范围内,0.5C倍率条件下,首次放电比容量为116.5 m Ah/g,循环100圈后容量保持率为93.5%;与不掺杂样品相比,其初始容量提高,100次循环的容量保持率提高,且高倍率循环性能也明显得到改善。     

原料粒度对固相合成锰酸锂正极电化学性能研究

近年来锂离子电池飞速发展已被广泛应用于便携式电子设备、新能源汽车和储能等领域。具有三维通道的尖晶石LiMn_2O_4材料由于其丰富的资源、低廉的价格和环境友好性,被认为是锂离子电池理想的正极材料。材料的形貌和尺寸决定了其物理化学性能,文中研究了不同粒度MnO_2原材料固相合成LiMn_2O_4材料及其电化学性能。研究结果表明原料粒径最小合成的LiMn_2O_4正极具有最佳的电化学性能,在0.2 C倍率下,首次放电比容量达到141 mAh/g,在1 C倍率下,循环100次,容量保持率为80.9%。     

尖晶石型LiMn_2O_4研究现状与发展

文章介绍了锂离子电池正极材料尖晶石锰酸锂的一些结构特性,重点描述了尖晶石LiMn_2O_4正极材料的制备方法及其优缺点,以及关于尖晶石LiMn_2O_4正极材料的最新改性研究,根据尖晶石LiMn_2O_4现有的状况展望了其发展前景。     

超声空化联合机械活化制备尖晶石LiMn_2O_4及其电化学性能

采用超声空化联合机械活化法合成一系列微观形貌不同的锂离子电池正极材料LiMn_2O_4,采用X射线衍射仪(XRD)、扫描电子显微镜(SEM)、电池充放电测试仪对制备的LiMn_2O_4正极材料的相组成特性、微观形貌和电化学性能进行相关测试。结果表明,本方法制备的LiMn_2O_4正极材料具有良好的尖晶石结构,延长机械活化时间可以得到致密的类球形结构的尖晶石材料,其中经过机械活化4 h后烧结得到的样品具有良好的电化学性能,在6 C放电倍率下放电比容量为88.2 mAh·g~(-1),返回0.5 C时容量恢复效率达到91.3%。     

无定形Li-Mn-Al-Co-O前驱体制备改性尖晶石锰酸锂

采用水热法合成了无定形Li-Mn-Al-Co-O前驱体,经过后续热处理制备了Al-Co复合掺杂LiMn_2O_4正极材料Li_(1.035)Co_(0.02)Al_(0.025)Mn_(1.92)0O_4,并对其物理及电化学性能进行了测试。SEM、XRD结果表明:Al-Co的掺入对尖晶石锰酸锂的形貌和晶体结构会有微弱影响。电化学测试结果表明:Al-Co掺杂后,材料的循环性能和倍率性能都获得了显著的改善,其在0.5 C下的首次放电容量为113.9 m A.h/g,经过100次循环后比容量保持率仍然有92.4%,8 C下容量依然高达85.5 m A·h/g。     

以煅烧二氧化锰制备尖晶石型锰酸锂研究

研究了电解二氧化锰粉体经850℃煅烧后的物相、形貌和比表面积,并分别以煅烧二氧化锰和未煅烧二氧化锰为锰源采用固相法制备了尖晶石型锰酸锂,比较了2种锰酸锂在物相、形貌、比表面和电性能方面的差异。结果表明:电解二氧化锰经850℃煅烧10 h后,产物为多孔的Mn2O3颗粒,比表面为1.250 m2/g;与用普通二氧化锰制备的锰酸锂相比,用煅烧二氧化锰制备的锰酸锂晶粒较大且尺寸均一、比表面积较小(0.677 m2/g)、循环性能较好,25℃下1 C循环50次后容量保持率为97.11%。     

富锂量对掺铝型锰酸锂性能的影响

研究了不同富锂量对锰酸锂性能的影响.对合成的材料进行了XRD、SEM、全电池充放电测试.结果表明,在热处理温度为920℃时,合成材料均为尖晶石相,随着富锂量的增加,颗粒的一次粒子粗化明显,比容量减小,倍率性能和循环性能提高;当富锂量为0.20 mol时,样品综合电化学性能最佳,1C放电比容量为90.4 mA·h/g,25℃和55℃下的1C充放50次,循环保持率分别为97.9％和94.1％.     

以金属铁粉为原料磷酸铁锂的制备和性能研究

以1~3μm金属铁粉和磷酸二氢锂为原料,采用高温固相法合成了无碳磷酸铁锂。通过X射线衍射(XRD),扫描电镜(SEM)和电化学测试等方法对合成的磷酸铁锂材料的结构、形貌和电化学性能进行了表征。研究结果表明,采用1~3μm的金属铁粉和磷酸二氢锂为原料,高温固相法合成了具有橄榄石晶体结构的磷酸铁锂材料,粉末近似球形,振实密度较高,一次颗粒200~300 nm。600℃合成的磷酸铁锂存在杂质相,650~750℃下合成的磷酸铁锂具有完整的橄榄石晶体结构,产物为纯相。无碳的磷酸铁锂呈浅灰色,600~750℃下合成的磷酸铁锂材料0.1C充放电存在平台,显示两相充放电特性,比容量均在100 mAh·g-1左右,且极化较大。用蔗糖对其进行包覆改性得到碳包磷酸铁锂,其颜色呈黑色,改性后的磷酸铁锂电化学性能有了较大的提高,0.1C比容量达到了154 mAh·g-1,充电平台和放电平台之间的极化明显降低,具有较好的循环稳定性。     

化学杂质对尖晶石LiMn_2O_4 电化学性能的影响

采用去离子水清洗以及添加不同Na_2SO_4杂质含量的方法研究了化学杂质对尖晶石LiMn_2O_4材料电化学性能的影响. 电感耦合等离子体发射光谱(ICP-AES)和离子色谱测试表明, 水洗后材料主要杂质元素Na, S均得到有效去除; 电化学测试表明, 水洗后材料放电比容量得到提高, 与含Na_2SO_4杂质LiMn_2O_4材料相比, 水洗后材料在2C常温循环及倍率性能上都明显优于含杂质LiMn_2O_4材料. 通过扫描电子显微镜(SEM)及能量色散谱(EDS)研究了Na, S化学杂质在电池体系中的存在形式及对材料电化学性能的影响. 结果表明, Na_2SO_4溶解于电解液中以及由Na离子在负极还原所引起的副反应将导致电池倍率及循环性能恶化.     

China's Major Non-ferrous Metals Imports & Exports

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Zinc Production by Province in 2014

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80% of Chinese Firms Purchasing Overseas Mines Ended up in the Red

<正>Minmetals Resources acquired the world’s largest copper mine under construction for USD5.85 billion.One after another,listed companies Jien Nickle,China Molybdenum and Chihong Zinc and Germanium raised money to get involved in overseas mining projects…SOEs and private enterprises are engaged in a frenzy of overseas mine purchasing.A reporter with Economic     

Copper Processing Profit Dropped Sharply,Copper Consumption Will Face Impact in the Second Half of the Year

正Judging from China’s copper consumption field,the biggest consumption unit is electric power,which accounts for 47%of total consumption;it is followed by light industry sector,including household electrical appliance,machinery,durable goods and hardware etc,which accounts for 22%of total consumption;followed by transportation field,     

Central Geological Prospecting Fund Newly Added 16.47 Million Tonnes of Bauxite in 2013

正In 2013,the Central Geological Prospecting Fund(CGPF)Project newly discovered 15 ore fields,including 3 large above ore fields,and 5medium sized ore fields.The reporter learned from the recently published"Annual Report of Central Geological Prospecting Fund Project(2013)"that,from 2006 to 2013 the CGPF     

Manufacturers of Copper Tube for Central Air Conditioner Use Face Mounting Pressure in the Final Quarter of the Year

正This year,the investment growth rate of real estate industry continued to slow down,sold area of commercial housing also dropped significantly,which brought huge pressure to the domestic air conditioning manufactures.In the first half of the year,by relying on high growth in national financial expenditure,along with investment in public infrastructure     

Xinjiang Ranks No.1 in Production of Primary Aluminum in China

正Kang Yi,Honorary Chairman of China Nonferrous Metals Industry Association,said recently at the Forum on Development of the Non-ferrous Metals Industry in Central and Western China held in Zhengzhou that,as more and more electrolytic aluminum factories in Xinjiang came into operation,the electrolytic aluminum output of Xinjiang had reached2,275,000 tons in the first 7 months this year,     

Shenhuo Coal Industry and Electricity Power Completed800,000 t/a Aluminum Project in Xinjiang

正"Xinjiang project has been completed according to schedule,but total completion and total start of production are two different concepts,after completion it still needs a gradual process of reaching production target."On the morning of November 3,Shenhuo Coal Industry and Electricity Power told investors the above statement on the investor interaction platform.     

Guangdong Metal Transaction Center has Become the Second Largest Precious Metal Transaction Platform Nationwide

正The reporter learned from Guangdong Province Precious Metal Transaction Center that in 2013the Center maintained healthy development momentum,and had become the second largest precious metal transaction platform in China in terms of market size;currently Guangdong is quickening steps of financial innovation for the Center,aiming to build a transaction center with international core competitiveness.     

Seven Rare Earth Projects Involving Close to 3 Billion Yuan Investment Landed In the HighTech Zone

正On May 22,Baotou Rare Earth Industry Cooperation Consultation MeetingProject Agreement-signing Ceremony was held in Ningbo,nearly 40 enterprises from Ningbo,Guangdong,Hunan,and Shanxi participated in project consultation.After multi-lateral communication,agreements were signed for a total of 7 rare earth projects successfully.