S-M(M=Al,Co)复合掺杂LiMn2O4的结构稳定性

应用量子化学电荷自洽离散变分Xα(SCC-DV-Xα)方法,研究了S-Al、S-Co复合掺杂增强尖晶石结构锂锰氧化物稳定性的作用机制.计算结果表明,S-Al复合掺杂锂锰尖晶石和S-Co复合掺杂锂锰尖晶石中的共价键强度均比未掺杂尖晶石LiMn2O4中的强,且与MnO2中的共价键强度相近;S-Al,S-Co复合掺杂尖晶石中Mn的电荷也与MnO2模型Mn6O2628-中十分接近.Mn原子的电荷密度次序是MnO2≈掺硫铝后锰锂尖晶石≈掺硫钴后的锂锰尖晶石<锰锂尖晶石.即LixMn3Co3O20S6n-和LixMn3Al3O20S6n-中Mn的状态与MnO2中的Mn相似.上述结果揭示了S和非Jahn-Teller效应阳离子(Al3 ,Co3 )复合掺杂尖晶石结构锂锰氧化物在电化学过程中不会发生Jahn-Teller畸变的内在原因.     

S-M（M=Al,Co）复合掺杂LiMn2O4的结构稳定性

应用量子化学电荷自洽离散变分Xα(SCC-DV-Xα)方法,研究了S-Al、S-Co复合掺杂增强尖晶石结构锂锰氧化物稳定性的作用机制.计算结果表明, S-Al复合掺杂锂锰尖晶石和S-Co复合掺杂锂锰尖晶石中的共价键强度均比未掺杂尖晶石LiMn2O4中的强,且与MnO2中的共价键强度相近; S-Al, S-Co复合掺杂尖晶石中Mn的电荷也与MnO2模型[Mn6O26]28－中十分接近. Mn原子的电荷密度次序是MnO2≈掺硫铝后锰锂尖晶石≈掺硫钴后的锂锰尖晶石< 锰锂尖晶石.即[LixMn3Co3O20S6]n－和[LixMn3Al3O20S6]n－中Mn的状态与MnO2中的Mn相似.上述结果揭示了S和非Jahn-Teller效应阳离子（Al3＋,Co3＋）复合掺杂尖晶石结构锂锰氧化物在电化学过程中不会发生Jahn-Teller畸变的内在原因.     

Pr6O11对ZnO压敏材料显微结构的影响

研究了在ZnO压敏材料组分中以溶液方式加入稀土氧化物Pr6O11后其微观结构的变化。结果表明，Pr6O11的加入改变了ZnO尖晶石相的生成途径，使该材料在低于700℃时生成大量焦绿石相（Bi3Zn2Sb3O14）。当烧成温度高于900℃时，焦绿石相分解生成细小的二次尖晶石相（Zn7Sb2O12）。这种二次生成的细小尖晶石使材料晶粒尺寸减小，分布均匀；此外，Pr6O11的引入能生成含Pr物相，以及Pr氧化物相也有利于材料的晶粒细化。晶粒细化结果改善了ZnO压敏材料的压敏电压和非线性特性，与掺杂前相比，压敏电压提高了约60％。     

催化裂化USY／ZnO／Al2O3脱硫添加剂的高温水热失活

 对USY／ZnO／Al2O3汽油催化裂化脱硫添加剂经高温水热老化处理前后的脱硫性能进行了考察，发现老化后添加剂的脱硫性能大幅度下降．采用XRD和IR等技术对USY／ZnO／Al2O3添加剂在高温和高温水热条件下失活的原因进行了研究．结果表明，在高温下，ZnO可与USY沸石中的铝发生固相反应生成ZnAl2O4尖晶石，从而造成USY晶体结构崩塌，转变成无定形状态．在ZnO含量较高的条件下，ZnO可继续与USY晶体结构崩塌后生成的无定形的硅和铝的氧化物反应，生成Zn2SiO4硅锌矿和ZnAl2O4尖晶石结构．这一方面使添加剂失去了可形成硫化物吸附中心的ZnO，另一方面破坏了硫化物的裂化活性组分USY，从而造成添加剂脱硫性能下降甚至失去脱硫活性．ZnO对USY的破坏作用主要与温度有关．在USY／ZnO／Al2O3体系中，ZnO被ZnO与Al2O3之间形成的锌铝尖晶石膜固定并与USY隔离，单纯的高温条件对添加剂的破坏不显著，而水蒸气可以促进ZnO的移动，有利于ZnO与USY的接触，因此在高温和有水蒸气存 在的条件下添加剂的结构易遭到破坏．     

催化裂化USY／ZnO／A12O3脱硫添加剂的高温水热失活

对USY／ZnO／A12O3汽油催化裂化脱硫添加剂经高温水热老化处理前后的脱硫性能进行了考察，发现老化后添加剂的脱硫性能大幅度下降．采用XRD和IR等技术对USY／ZnO／A12O3添加剂在高温和高温水热条件下失活的原因进行了研究．结果表明，在高温下，ZnO可与USY沸石中的铝发生因相反应生成ZnAl2O4尖晶石，从而造成USY晶体结构崩塌，转变成无定形状态．在ZnO含量较高的条件下，ZnO可继续与USY晶体结构崩塌后生成的无定形的硅和铝的氧化物反应，生成Zn2SiO4硅锌矿和ZnAl2O4尖晶石结构．这一方面使添加剂失去了可形成硫化物吸附中心的ZnO，另一方面破坏了硫化物的裂化活性组分USY，从而造成添加剂脱硫性能下降甚至失去脱硫活性．ZnO对USY的破坏作用主要与温度有关．在USY／ZnO／Al2O3体系中，ZnO被ZnO与Al2O3之间形成的锌铝尖晶石膜固定并与USY隔离，单纯的高温条件对添加剂的破坏不显著，而水蒸气可以促进ZnO的移动，有利于ZnO与USY的接触，因此在高温和有水蒸气存在的条件下添加剂的结构易遭到破坏．     

CuZnAl水滑石衍生催化剂上甲醇水蒸气重整制氢Ⅰ. 催化剂焙烧温度的影响

 以类层柱CuZnAl水滑石为前体,经不同温度焙烧制备了一系列甲醇水蒸气重整制氢催化剂. 在250 ℃、 水/甲醇比1.3和重时空速2.5 h-1下的反应结果表明, 600 ℃焙烧的催化剂具有优异的活性和稳定性,而≤500 ℃和≥700 ℃焙烧后的催化剂活性较差. 热重、 X射线衍射、 傅里叶变换红外光谱和程序升温还原分析结果表明, 600 ℃焙烧时水滑石分解较为完全,析出纳米CuO粒子的同时伴生CuAl2O4尖晶石相,进而在反应过程中对金属Cu纳米粒子和ZnO起到良好的隔离和稳定作用. 焙烧温度≥700 ℃时CuO纳米粒子发生二次团聚,同时CuAl2O4尖晶石相大量生成,造成催化活性位减少,活性较低; 而焙烧温度≤500 ℃时水滑石分解不完全,生成 (Cu,Zn)AlxOy(CO3)z复合物且无尖晶石相伴生,造成反应中金属Cu纳米粒子和ZnO聚集,导致催化剂活性较低.     

富锂锂锰氧化物的制备及其在溶液中的抽Li+/吸Li+性能

采用柠檬酸配合法合成了系列尖晶石富锂锂锰氧化物Li2O.nMnO2(n=1.75,2.0,2.25,2.5,3.0)。通过X射线衍射(XRD)和酸浸实验发现,350℃合成的Li2O.2.25MnO2具有纯相尖晶石锂锰氧化物结构,且在弱酸性介质中具有较高的锂溶出率和较低的锰溶损率。Li2O.2.25MnO2在酸浸之后转型为锂离子筛。XRD和扫描电子显微镜(SEM)分析发现锂离子筛能够保持尖晶石锂锰氧化物的结构和形貌。吸附实验表明,该锂离子筛在碱性含锂溶液中对Li+具有吸附性能,且吸附容量随着溶液温度和pH值的升高而增大,最高能达到40.14 mg.g-1。通过傅立叶红外光谱(FTIR)研究了锂离子筛的吸附机理,并用Langmuir模型描述了其在LiCl+LiOH溶液中的吸附行为。     

催化剂活性测定实验的改进

为了改善流动法测定催化剂活性的实验,采用浸渍-煅烧法和共沉淀．煅烧法分别制备了CuO—ZnO／Al2O3和CuO—ZnO—NiO／Al2O3催化剂,并与传统的ZnO／Al2O3进行了比较。发现采用浸渍一煅烧法制备的CuO—ZnO—NiO／Al2O3催化剂的低温催化活性最高。实验表明,采用新型CuO．ZnO—NiO／Al2O3催化剂可将甲醇分解的实验温度降低100％,且实验效果得到明显改善。     

ZnCr基催化剂煅烧温度对异丁醇合成性能的影响

研究了煅烧温度对ZnCr基催化剂合成异丁醇性能的影响。结果表明,随着煅烧温度的升高,催化剂的活性和产物分布都发生了较大的变化。催化剂在较低的温度下煅烧,液相产物中醇主要是甲醇和异丁醇;在较高的温度下煅烧,液相产物醇的分布符合A-S-F方程。用BET、XRD、H₂-TPR、XPS等技术手段对催化剂织构参数、体相结构、还原性能、表面组成进行表征。结果表明,在300℃煅烧时,催化剂中的ZnO和Cr₂O₃未完全形成非计量尖晶石Zn_xCr_2/3(1-x)O;400℃煅烧时,催化剂中形成了最多量非计量尖晶石Zn_xCr_2/3(1-x)O;当煅烧温度高于400℃时,随着煅烧温度进一步升高,非计量尖晶石Zn_xCr_2/3(1-x)O逐步发生了分解,生成了更多量的ZnO和Cr₂O₃,导致催化剂的活性随之下降。进一步证明了非计量尖晶石Zn_xCr_2/3(1-x)O是该催化反应活性相。     

Mn_(1-x)(Li,Ti)_xCo_2O_4尖晶石型复合氧化物的制备、表征与催化性能

用柠檬酸配位燃烧法合成了Mn1-x(Li,Ti)xCo2O4系列尖晶石型复合氧化物催化剂,使用FTIR和XRD方法对催化剂结构进行表征,通过程序升温氧化反应(TPO)技术对这些催化剂在模拟柴油机尾气条件下进行同时消除NOx和柴油碳黑反应的活性评价。结果表明,掺杂Li或Ti后的Mn1-x(Li,Ti)xCo2O4系列催化剂仍然保持了完整的尖晶石型复合氧化物结构,这些催化剂对同时消除柴油机尾气中的碳黑颗粒和NOx具有良好的催化性能,其中Li或Ti的掺杂量为x=0.05较佳,结合碳黑燃烧与NOx还原总的催化效果,Mn0.95Li0.05Co2O4具有最好的催化活性。     

Regenerable Fe-Mn-ZnO/SiO2 sorbents for room temperature removal of H2S from fuel reformates: performance, active sites, Operando studies

Fe- and Mn-promoted H(2)S sorbents Fe(x)-Mn(y)-Zn(1-x-y)O/SiO(2) (x, y = 0, 0.025) for desulfurization of model fuel reformates at room temperature were prepared, tested and characterized. Sulfur uptake capacity at 25 °C significantly exceeds that of both commercial unsupported ZnO sorbents and un-promoted supported ZnO/SiO(2) sorbents. Sulfur capacity and breakthrough characteristics remain satisfactory after multiple (～10) cycles of adsorption/regeneration, with regeneration performed by a simple and robust heating in air. XRD shows that both "calcined" and "spent" sorbents contain nano-dispersed ZnO, and XPS confirms conversion of ZnO to ZnS. "Calcined" sorbent contains Fe(3+) and Mn(3+) that are reduced to Mn(2+) upon reaction with H(2)S, but not with H(2). Operando ESR is used for the first time to study dynamics of reduction of Mn(3+) promoter sites simultaneously with measuring sulfidation dynamics of the Fe(x)-Mn(y)-Zn(1-x-y)O/SiO(2) sorbent. Fe cations are believed to occupy the surface of supported ZnO nanocrystallites, while Mn cations are distributed within ZnO.     

高温煤气铁钙基脱硫剂再生研究

在固定床装置上考察了温度和氧浓度对铁钙基脱硫剂再生率以及二次脱硫活性的影响，同时还考察了此脱硫剂用于模拟的脱硫除尘一体化条件下，黏附于表面的粉尘对脱硫剂再生行为以及二次脱硫行为的影响。结果表明，该脱硫剂在480 ℃下再生效果良好，650℃再生率下降，在考察的温度区间内（400 ℃～650 ℃）温度对二次脱硫活性影响较小，在以后的循环中，温度对再生率以及脱硫活性的影响也小，再生气氛中氧浓度对再生率以及二次脱硫活性的影响不明显；研究发现加入粉尘虽然会降低脱硫剂的再生率，但基本不影响二次脱硫活性。     

Co-K-Mo/γ-Al2O3催化剂的合成低碳醇性能及其结构研究

氧化态Ｋ－ＭｏＯ３／γ－Ａｌ２Ｏ３催化剂中添加Ｃｏ（ＮＯ３）２后在空气中四个不同温度下焙烧再硫化,制得Ｃｏ－Ｋ－ＭｏＯ３／γＡｌ２Ｏ３催化剂,对其ＣＯ加氢合成低碳醇的催化反应性能进行了评价,运用ＸＲＤ,ＬＲＳ及ＥＸＡＦＳ等手段对催化剂及其氧化态前躯体的结构进行了表征,活性测试结果表明加Ｃｏ后于５００－６５０℃焙烧制得的催化剂活性较高,且使Ｃ２＋醇比例增加,结构分析结果显示加Ｃｏ后３５０℃焙烧时,Ｃ     

Mn/beta与Mn/ZSM-5催化剂对氨选择性催化还原NO的低温催化活性比较: 锰前驱体的影响

氮氧化物(NOx)作为主要的大气污染物之一,给环境和人类带来一定危害,其主要源于汽车、轮船以及工厂中液态(汽油和柴油)或固态(煤)化石原料的燃烧.目前,选择性催化还原法(SCR)因技术相对成熟且经济有效,被广泛应用于氮氧化物脱除.催化剂是该技术的关键,而典型的商业钒系催化剂(V2O5-WO3/TiO2和V2O5-MoO3/TiO2)存在工作窗口温度窄(300–400 ℃)、V2O5的生物毒性以及较高的SO2氧化性能等缺点,因此开展高效且环境友好催化剂的研究工作迫在眉睫.近年来,锰基催化剂因其丰富的价态变化以及氧化形态而受到科研工作者的广泛关注.研究者已经对锰前驱体做了大量研究,但是关于不同锰前驱体制备得到的催化剂的活性物种组成以及催化活性往往存在着不同观点.因此进一步开展对锰前驱体研究仍有必要.同时,二氧化钛载体比表面积较小,并不是制备锰基催化剂的理想载体.分子筛载体因其比表面积大、特殊的孔道结构以及丰富的酸位等特点引起了研究者的关注.用于制备锰基催化剂的分子筛载体主要有ZSM-5,Beta,USY和SAPO等,其中ZSM-5系列催化剂是研究热点.另一方面,研究发现Beta分子筛具有良好的水热稳定性,被认为是理想的NH3-SCR催化剂载体.研究者对比了不同金属负载的Beta分子筛与ZSM-5分子筛的催化活性,结果表明,Fe/beta的催化活性高于Fe/ZSM-5和Fe/ZSM-11; Cu/beta的催化活性与Cu/ZSM-5相当,均表现出较高的活性.而关于Mn/ZSM-5的研究已有大量文献报道,但关于Mn/beta的研究相对较少.另外,关于不同锰前驱体在Beta以及ZSM-5分子筛载体表面的物化性质差异也少有报道.本文以H/beta和H/ZSM-5分子筛作为载体,采用硝酸锰、乙酸锰和氯化锰三种前驱体,通过湿法浸渍制备了Mn/beta和Mn/ZSM-5两类NH3-SCR催化剂,并在固定床管式反应器中对比评价了两类催化剂的催化活性.凭借氮气等温吸附/脱附(BET)、X射线衍射(XRD)、X射线荧光(XRF)、氢气程序升温还原(H2-TPR)、氨气程序升温脱附(NH3-TPD)以及X射线光电子能谱(XPS)等技术对催化剂进行了表征,系统分析了不同前驱体在两种载体表面形成的活性组分以及理化性质对催化性能的影响.催化剂活性评价结果表明,对于Mn/beta和Mn/ZSM-5催化剂,在220–350 ℃反应温度区间内,乙酸锰和硝酸锰制备的催化剂NO脱除率均在80%以上.其中Mn/beta-Ac在240 °C时达到最高的NO脱除率97.5%,并且在220–350 ℃温度区间内保持着90%以上的活性,具有最宽的活性温度窗口.同时,在两系列锰基催化剂中,乙酸锰制备的催化剂均表现出最佳的催化活性,且对于同一种前驱体制备的催化剂,Mn/beta催化剂的NH3-SCR活性优于Mn/ZSM-5.BET数据显示,负载锰物种之后,催化剂的比表面积和孔体积均明显减小,但相对于Mn/ZSM-5催化剂,Mn/beta催化剂仍保持着优良的织构性质.XRD、XRF及H2-TPR结果表明,氯化锰前驱体主要产生少量的结晶Mn3O4并且大部分保持以MnCl2的形式存在,这也是此类催化剂表现出较差的低温催化活性的原因.结合XPS表征分析了催化剂的表面性质.结果表明,硝酸锰前驱体主要产生结晶MnO2和少量未分解的硝酸锰,乙酸锰前驱体主要产生高度分散的无定形MnO2和Mn2O3混合物以及结晶Mn3O4.进一步结合NH3-TPD分析结果以及活性评价结果可以得出: 丰富的无定形MnOx(MnO2和Mn2O3)物种、较高的表面锰含量和表面活性氧基团以及适当含量的弱酸位有利于提升催化剂的低温NH3-SCR催化活性.     

铁钙氧化物高温脱硫过程中H_2和H_2O(g)效应

研究了高温煤气中的H2 和H2 O(g)对铁钙氧化物高温脱硫行为的影响。结果表明 ,对还原态和非还原态脱硫剂 ,气氛中的H2 的影响有所不同。对前者 ,硫化气体中的H2 不利于脱硫 ;对后者 ,由于H2 首先会部分还原脱硫剂 ,提高其活性 ,因而有利于脱硫。H2 O(g)的存在对硫化和还原过程均起阻碍作用。     

CeO2掺杂的Mn/Al催化剂的物化、表面及催化性能

Pure and CeO2-doped Mn/Al mixed oxides were prepared by the wet impregnation method using finely powdered alumina, manganese, and cerium nitrates. The physicochemical, surface, and catalytic properties of the thermally treated solids (at 500, 800, and 900 ℃) were investigated using XRD, nitrogen adsorption at -196 ℃, and hydrogen peroxide decomposition in an aqueous solution at 30 - 50 ℃. The Mn oxidation state changed from Mn4 to Mn2 on increasing the calcination temperature. There were two unique features associated with CeO2 that are of interest. The first was that it favored the dispersion of manganese oxides deposited on the γ-Al2O3 catalyst calcined at 500 ℃. The second was that it enhanced the formation of Mn3O4 species from Mn2O3 deposited initially on the alumina support calcined at 800 and 900 ℃. Consequently, the specific surface area of the Mn/Al mixed oxides calcined at 500 ℃ was increased by increasing the amount of dopant added. An opposite effect was observed by increasing the calcination temperature from 500 to 900 ℃. The doping followed by calcination at different temperatures brought about an increase in the catalytic activity of mixed oxides. Pretreatments did not modify the mechanism of the catalyzed reaction but changed the number of catalytically active sites without changing the nature of these sites.     

负载型La0.8Sr0.2MnO3燃烧催化剂的载体效应

Combustion catalysts La0.8Sr0.2MnO3 supported on γ-Al2O3, α-Al2O3, cordierite (2MgO•2Al2O3•5SiO2) and ZrO2 were compared. Further investigation was focused on LSM/ γ-Al2O3 catalyst. It was observed that LSM/γ－Al2O3 catalyst loaded with 20% (mass fraction) LSM (La0.8Sr0.2MnO3 or corresponding oxides), heated at 750℃ or above, perovskite-type oxides were found by XRD examination, whereas, the same catalyst loaded with 10% or less LSM, perovskite oxides were absent, calcination temperature about 750℃ is necessary for the formation of perovskite structure in LSM/γ-Al2O3 catalysts. High activity of complete oxidation of xylen will be obtained when perovskite-type oxides.
Investigation of TPR showed that neat LSM or LSM/γ-Al2O3(20%) was reduced by H2-N2 mixed gas. Two degradation processes took place. In the first, reduced temperature peak was about 350 - 450℃. If reduction ended at 400℃, perovskite structure was retained, which may be due to the reduction of Mn3+to Mn2+ on the surface of LSM only. In the second process, perovskite structure was destroied, and La2O3, Mn2O3, Mn - Sr - O oxides could be obtained, which took place in the temperature range 685 - 750℃ and ended at 800℃. This was proved by TPR experiments (Fig. 3, 5) and XRD patterns (Fig. 4)
Catalysts LSM/γ-Al2O3(10% or 20%) heated at 500℃ have only one TPR peak, i. e. lower temperature peak. This is due to the absence of perovskite-type oxides in the catalysts. However, neat LSM or LSM/γ-Al2O3(20%) heated 750℃ or above, not only the first low temperature TPR peak but also the second peak, which is contributed by the perovskite-type oxides in these catalysts appeared. Therefore, the second TPR peak, i. e. the higher temperatue peak is a characteristic peak for perovskite-type oxides in the reduced process. When LSM/ γ-Al2O3 (10%) catalys is heated at 750℃, no perovskite-type oxides were detected by XRD, and the second reduction peak was absent also in TPR process. \
The order of the second reduction peak temperature(characteristic peak of perovskite - type ox- ides) is: neat LSM(750℃）> LSM/γ-Al2O3 20% (685-698℃) -deposited LSM/γ-Al2O3 (698℃) > LSM/γ-Al2O3 15% (677 - 680℃) >(LSM/γ-AL2O3 10% 620 - 630℃, for Mn - Al - O medium oxides on surface). It is correleted with the increasing of the effect of support sequentially.
When LSM/γ-Al2O3 catalysts were heated at 900℃, more stable phase, spinel MnAl2O4 appeared, which could be proved by TPR of model catalyst MnAl2O4/γ-Al2O3.     

Comparison of reduction behavior of Fe2O3, ZnO and ZnFe2O4 by TPR technique

Advanced integrated gasification combined cycle (IGCC) power generation systems require the development of high-temperature,regenerable,desulfurization sorbents capable of removing hydrogen sulfide from coal gasifier gas to very low levels.As a sort of effective desufurizer,such as Fe2O3,ZnO and ZnFe2O4,it will endure strong reducing atmosphere in desulfurization process.The reduced degree of desufurizer can have an effect on its desulfurization reactivity.In this paper,Fe2O3,ZnO and ZnFe2O4 were synthesized by precipitation or co-precipitation at constant pH.After aging,washing and drying,the solids were calcined at 800℃.The reduction behaviors of sample were characterized by temperature-programmed reduction (TPR).It is found that there are two reduction peaks for Fe203 in TPR,and whereas no reduction peaks for ZnO are found.The reduction process of ZnFe2O4 prepared by co-precipitation is different from that of Fe2O3.ZnFe2O4 is easier to be reduced than Fe2O3.The activation energy of reduction process for Fe2O3 and ZnFe2O4 is obtained at different reduction periods.     

活性炭（焦）低温吸附催化脱除H2S的基础研究

以活性炭、活性焦作为脱硫剂,并应用BET、XPS等测试手段对其进行分析表征。结果表明,活性炭（焦）的脱硫能力与其表面酸碱性有着密切的关系,增加表面上起碱性作用的π-π^﹡键,羰基官能团（C-O和醚基官能团（C-O）的浓度,可增加其表面催化作用,特别是C-O官能团;反应温度对活性炭（焦）的脱硫性能有很大的影响,脱硫剂在150℃～180℃活性高,硫容大,副反应少;水蒸气对活性炭（焦）脱除H₂S有促进作用。     

Li2CO3、NiO和电解MnO2合成高容量LiNi0.5Mn1.5O4及其表征

Well-developed crystalline LiNi_0.5Mn_1.5O₄ was prepared by solid-state reaction using Li₂CO₃, NiO and electrolytic MnO₂ at high heating and cooling rate. X-ray diffraction (XRD) patterns and scanning electron microscopic (SEM) images showed that LiNi_0.5Mn_1.5O₄ synthesized at 900 ℃ and 950 ℃ had cubic spinel structure with clearly defined shape. LiNi_0.5Mn_1.5O₄ spinel phase decomposed at 1 000 ℃ accompanying with structural and morphological degradation. TG measurement revealed that the weight loss during heating process could be mostly gained in cooling process, and the upward tendency of weight loss during heating process decreased, while that of irreversible weight loss rapidly increased with the increase of temperature. LiNi_0.5Mn_1.5O₄ powders prepared at 900 ℃ for 12 h delivered the maximum discharge capacity of 134 mAh·g^-1 with good cyclic performance at 2/7 C. In addition, by adjusting the calcination time at 900 ℃, the capacity and cycling performance of LiNi_0.5Mn_1.5O₄ were further enhanced.