球形高电压LiNi0.5Mn1.5O4的制备及其电化学性能

以化学共沉淀法制备的球形Ni0.25Mn0.75CO3为前驱体合成高电压正极材料LiNi0.5Mn1.5O4,探讨用前驱体与Li2CO3直接反应和用前驱体分解后的氧化物与Li2CO3反应两种工艺路线对LiNi0.5Mn1.5O4形貌和电化学性能的影响。用扫描电镜(SEM)和X射线衍射(XRD)对Ni0.25Mn0.75CO3前驱体和LiNi0.5Mn1.5O4样品进行表征,用充放电测试和循环伏安法对LiNi0.5Mn1.5O4样品进行电化学性能研究。结果表明:两种方法合成的LiNi0.5Mn1.5O4均具有尖晶石型结构。但以前驱体Ni0.25Mn0.75CO3直接与Li2CO3反应合成的LiNi0.5Mn1.5O4的一次粒子颗粒较大,形貌较差,性能也较差;而以前驱体分解后的氧化物与Li2CO3反应合成的LiNi0.5Mn1.5O4的形貌及性能均较好。在3.0~4.9 V的电压范围内,1C倍率下电池的放电比容量达到136.3 mA.h/g,循环100次仍有126.5 mA.h/g,且材料具有较好的倍率性能;5C倍率下的首次放电比容量高达120.7 mA.h/g。     

LixNi0.5Mn0.5O2正极材料的合成及电化学性能研究

采用草酸盐共沉淀法合成了层状LixNi0.5Mn0.5O2(x=1.00,1.05,1.10,1.15)正极材料,并研究了配锂量x为1.0,1.05,1.0和1.15时对终产物的结构及电化学性能的影响。采用X射线衍射(XRD)表征LixNi0.5Mn0.5O2材料的结构,使用充放电实验、EIS及CV研究了LixNi0.5Mn0.5O2的电化学性能。结果表明,x为1.10时材料具有良好的层状特征,且材料中锂/镍的混排程度最小。x为1.10时材料内阻小,有更好的循环稳定性和可逆性。在测试温度55℃和电压2.0～4.5V范围内,材料的首次放电比容量达到了239.6mAh/g,在循环20周后,容量保持率为98.2%。     

锂离子电池正极材料LiNi_(0.5)Co_(0.5)O_2制备与电化学性能

采用球磨湿混和旋转合成相结合的新工艺制备了锂离子电池正极材料 L i Ni0 .5Co0 .5O2 ,并对材料进行了粒度、化学成分以及电化学性能测试。球磨湿混工艺能将原料混合均匀 ,并能有效地使粒度细化。旋转合成工艺能使混合料在均匀的温度场中进行反应 ,并使反应产物粒度均匀和成分均匀。制备的 L i Ni0 .5Co0 .5O2 为单一的 α- Na Fe O2 层状结构 ,粉末粒度分布范围窄 ,平均粒径约为 8μm～ 10μm。电化学性能测试结果表明 ,在 0 .2 m A/cm2 充放电流密度和 3 .0 V～ 4 .2 V电压范围内 ,首次充电容量为 173 m Ah/g,放电容量为 14 8m Ah/g。循环次数达 3 0次时 ,放电容量还有 12 9m Ah/g,循环稳定性良好。球磨湿混和旋转合成相结合的固相合成新工艺能制备出电化学性能良好的L i Ni0 .5Co0 .5O2 正极材料。     

共沉淀法制备LiNi0.8Co0.1Mn0.1O2过程中加料速度对其性能的影响

采用共沉淀法制备Ni0.8Co0.1Mn0.1(OH)2前驱体,与LiOH.H2O混合后在氧气气氛中焙烧得到LiNi0.8Co0.1Mn0.1O2正极材料,探讨共沉淀反应过程中快速加料和慢速加料制度对前驱体形貌和LiNi0.8Co0.1Mn0.1O2正极材料性能的影响。通过X射线衍射(XRD)、扫描电镜(SEM)和电化学测试对样品进行表征。结果表明:慢速加料法减小了材料的粒径,合成了平均粒径在0.5μm左右的球形Ni0.8Co0.1Mn0.1(OH)2前驱体,且粒径分布比较集中;所合成LiNi0.8Co0.1-Mn0.1O2正极材料具有良好的层状结构,且无杂相存在;缓慢加料法得到的样品的电化学性能有很大提高,在0.1 C、0.5 C和1 C下首次放电比容量分别达到223.5、194.3和190.7 mA.h/g,循环30次后,容量保持率为80.09%、80.80%和85.84%。     

高容量锂离子电池正极材料LiNi0.5Co0.2Mn0.3O2的制备与工艺优化

采用氢氧化物共沉淀法合成前驱体Ni_0.5Cc_0.2Mn_0.3H(OH)₂,进一步用高温固相法与锂源共混煅烧得到LiNi_0.5Co_0.2Mn_0.3O₂。初步探讨了前驱体与锂源在高温煅烧过程中的质量变化及煅烧工艺对材料结构和性能的影响。热重分析(TGA)表明在煅烧过程中750℃后材料质量几乎没有变化。X射线衍射(XRD)对750℃-900℃的材料进行结构分析,结果表明所有材料具有良好的α-NaFeO₂层状结构和较小的阳离子混排度。扫描电镜(SEM)分析表明材料具有表面光滑,分布均匀的球形结构。横流充放电测试结果表明在850℃煅烧的材料具有最好的电学性能,在0.2C,2.5-4.6V测试条件下,其具有193.7mAh/g的首次放电容量,循环30次后的容量保持率为94.2%,并且具有最好的倍率性能。     

加压氧化法制备LiNi0.8Co0.15Al0.05O2正极材料

以控制结晶法合成的球形Ni0.8Co0.15Al0.05(OH)2.05为前驱体,采用加压氧化法制备锂离子电池正极材料LiNi0.8Co0.15Al0.05O2。利用X射线衍射(XRD)、扫描电镜(SEM)和恒电流充放电测试等方法对该材料的结构、形貌及电化学性能进行表征。考察氢氧化锂与前驱体物质的量之比(锂配比)、在煅烧过程中的压力、温度和时间等因素对LiNi0.8Co0.15Al0.05O2材料结构及性能的影响。结果表明:锂配比为1.02时,在0.4 MPa氧气压力下,于700℃煅烧10 h制备的材料具有最完善的结构和最好的电化学性能;在2.8~4.3 V电压范围内,以0.2 C进行充放电,首次放电比容量达到190.1 mA.h/g,50次循环后容量保持率为90.2%,同时显示出良好的倍率性能和高温性能。     

锂离子电池正极材料LiNi1-yAlyO2的制备及性能

在高温增加氧气压力的条件下 ,通过固态反应合成了锂离子电池正极材料LiNi1-yAlyO2 。讨论了合成条件对产物的电化学性能的影响 ,得到最佳的反应条件是 :2个恒温阶段的反应时间为 8h和 10h ;氧气压力为0 .2 0MPa ;反应温度 80 0℃ ;反应物Li,Ni,Al之间的摩尔比为 1.1∶0 .95∶0 .0 5。合成出具有晶型完整、电化学性能优良的LiNi0 .95Al0 .0 5O2 产品 ,其放电容量达 182 .3mA·h/g。结果表明 ,Al3 + 的添加对LiNiO2 的结构及电化学性能有较大的改善。     

锂离子电池富锂材料Li[Li0.2Ni0.2Mn0.6]O2的制备及掺杂改性

以乙酸盐为原料,采用喷雾干燥法制备层状α-NaFeO2结构的富锂正极材料Li[Li0.2Ni0.2Mn0.6]O2及掺杂Cr的Li[Li0.2Ni0.15Cr0.1Mn0.55]O2。采用X射线衍射、扫描电镜、半电池充放电和电化学阻抗谱等方法研究材料的物相、结构、形貌及电化学性能。结果表明:Cr掺杂使材料的颗粒变粗,但不改变材料的结构,而使材料的层状特征更为明显;Cr掺杂后材料的电化学性能得到明显改善,电荷转移阻抗Rct从275.0降低到105.0,循环稳定性和倍率性能均有所改善,Li[Li0.2Ni0.15Cr0.1Mn0.55]O2材料1C倍率下的放电比容量为140.0 mA.h/g,循环50次后放电比容量为133.7 mA.h/g,远高于未掺杂Cr材料的比容量,未掺杂Cr材料在1C倍率下放电比容量为107.1mA.h/g,循环50次后放电比容量为102.1 mA.h/g。     

三元锂离子正极材料LiNi0.6Co0.2Mn0.2O2的控制合成与储能特性

采用草酸共沉淀法和高温固相法相结合的方法成功合成了LiNi0.6Co0.2Mn0.2O (NCM622)三元锂离子正极材料,通过先用水热合成草酸钴锰前驱体,然后再与镍盐、锂盐进行高温固相反应,避免了Ni2+、Co2+、Mn2+在草酸中沉淀不均匀的问题.X射线衍射(XRD)分析结果表明,该材料具有典型的类似α-NaFeO2的层状结构以及低的阳离子混排.电化学性能测试结果显示,相比于商业镍钴锰酸锂(NCM-商业),NCM622表现出优良的循环稳定性和倍率性能,在0.1C下经850℃处理的NCM-850试样的初始放电容量为184.1 mAh g-1,高于NCM-商业的175mAhg-1,在0.2C循环100圈以后NCM-850的容量保持率为88.6％而NCM-商业的保持率仅为47.8％.在5C下NCM-850仍然具有98.1mAhg-1的容量.这主要归因于材料拥有更稳定的晶体结构和更宽的离子扩散通道.     

高容量正极材料Li[Li0.2Ni0.2Mn0.6]O2的合成及电化学性能

以LiOH.H2O、Ni(OH)2和Mn3O4为原料,采用固相法合成锂离子电池正极材料Li[Li0.2Ni0.2Mn0.6]O2。通过X射线衍射(XRD)、扫描电子显微镜(SEM)对所得样品的结构和形貌进行表征,并测试了该材料的倍率性能和高低温性能。结果表明:900℃下烧结10 h后可获得晶粒细小均匀的层状Li[Li0.2Ni0.2Mn0.6]O2材料,并具有良好的电化学性能,放电容量最高可达235.9 mA.h/g;在50℃下测试时该材料的放电容量高达284.4 mA.h/g,并表现出良好的循环性能,其倍率性能和低温性能还有待进一步改善。     

Cr3+掺杂LiNi0.5Mn1.5O4材料的制备及性能研究

采用高温固相法合成了Cr₃₊掺杂的LiNi_0.5Mn_1.5O₄正极材料,研究了掺杂量对材料物理性能和电化学性能的影响。利用XRD、SEM对材料的结构和形貌进行了表征,结果显示样品具有棱边清晰的尖晶石形貌。讨论了不同Cr₃₊掺杂量对LiCr_xNi_0.5-0.5xMn_1.5-0.5xO₄(x=0,0.05,0.1,0.15,0.2)正极材料性能的影响。充放电测试、循环伏安和交流阻抗测试结果表明：当Cr₃₊的掺杂量为x=0.1时(LiCr_0.1Ni_0.45Mn_1.45O₄)正极材料的性能最好,0.1C、0.5C、1C、2C及5C的首次放电比容量依次为131.54mAh g_-1、126.84mAh g_-1、121.28mAh g_-1、116.49mAh g_-1和96.82mAh g_-1,1C倍率下循环50次,容量保持率仍为96.5%。     

Synthesis and electrochemical performance of Li(Ni0.8Co0.15Al0.05)0.8(Ni0.5Mn0.5)0.2O2 with core-shell structure as cathode material for Li-ion batteries

The core-shell structure cathode material Li(Ni_0.8Co_0.15Al_0.05)_0.8(Ni_0.5Mn_0.5)_0.2O₂ (LNCANMO) was synthesized via a co-precipitation method. Its applicability as a cathode material for lithium ion batteries was investigated. The core-shell particle consists of LiNi_0.8Co_0.15Al_0.05O₂ (LNCAO) as the core and a LiNi_0.5Mn_0.5O₂ as the shell. The thickness of the LiNi_0.5Mn_0.5O₂ layer is approximately 1.25 μm, as estimated by field emission scanning electron microscopy (FE-SEM). The cycling behavior between 2.8 and 4.3 V at a current rate of 18 mA g⁻¹ shows a reversible capacity of about 195 mAh g⁻¹ with little capacity loss after 50 cycles. High-rate capability testing shows that even at a rate of 5 C, a stable capacity of approximately 127 mAh g⁻¹ is retained. In contrast, the capacity of LNCAO rapidly decreases in cyclic and high rate tests. The observed higher current rate capability and cycle stability of LNCANMO can be attributed to the lower impedance including charge transfer resistance and surface film resistance. Differential scanning calorimetry (DSC) indicates that LNCANMO had a much improved oxygen evolution onset temperature of approximately 251 °C, and a much lower level of exothermic-heat release compared to LNCAO. The improved thermal stability of the LNCANMO can be ascribed to the thermally stable outer shell of LiNi_0.5Mn_0.5O₂, which suppresses oxygen release from the host lattice and not directly come into contact with the electrolyte solution. In particular, LNCANMO is shown to exhibit improved electrochemical performance and is a safe material for use as an electrode for lithium ion batteries.     

锂离子电池正极材料LiNi0.8Co0.15Al0.05O2的制备及电化学性能

首先以AlO2-为铝源,采用三元共沉淀法制备前驱体Ni_(0.8)Co_(0.15)Al_(0.05)(OH)_2。对前驱体进行500℃高温处理,随后与过量的锂盐混合均匀,在氧气气氛下700℃煅烧12 h制得LiNi_(0.8)Co_(0.15)Al_(0.05)O_2(NCA)材料。采用X射线衍射仪(XRD)测试可知,所得的NCA材料呈典型的α-NaFeO_2层状结构,属于R-3m空间群。扫描电子显微镜(SEM)测试显示,NCA为粒径5～6μm的球状颗粒。材料在电流倍率为0.1C下首次放电容量为167.1mAh/g,循环200次以后容量保持率为96.2%。倍率测试表明,0.1、10 C下NCA的容量分别为184.0、112.7 mAh/g,到恢复到0.1 C时,容量仍可达179.7mAh/g,具有比较好的倍率性能。     

Electrolyte perspective on stabilizing LiNi0.8Co0.1Mn0.1O2 cathode for lithium-ion batteries

Nickel-rich LiNi_0.8Co_0.1Mn_0.1O₂(NCM811) is regarded as the promising cathode for lithium-ion batteries(LIBs).However,the challenges such as safety issues and poor cycling performance have seriously hindered its commercial applications.In order to overcome these difficulties,there has been extensive research and development of electrolyte modifications for high-energy-density LIBs with Ni-rich cathodes.Herein,this review introduces the research progress...     

Study of synthesis and electrochemical properties of spinel LiNi0.5Mn1.2Ti0.3O4 by different methods

Two spinel LiNi_0.5Mn_1.2Ti_0.3O₄ samples were successfully synthesized by the sol-gel method using chemicals LiAc·2H₂O, Mn(Ac)₂·2H₂O, Ni(Ac)₂·4H₂O and Ti(OCH₃)₄ as reactants. When reactants are calcined in air, a sample of LiNi_0.5Mn_1.2Ti_0.3O₄ (1), which contains Mn³⁺ and Mn⁴⁺ ions, is obtained. The sample of LiNi_0.5 Mn_1.2Ti_0.3O₄ (2), which contains only Mn⁴⁺ ions, is obtained when reactants are calcined in an oxygen atmosphere. X-ray diffraction (XRD), scanning electron microscopy (SEM), galvanostatic charge-discharge test and cyclic voltammogram test were employed to investigate the two samples. XRD results show that there is a small shift towards a larger diffraction angle for peaks of the LiNi_0.5Mn_1.2Ti_0.3O₄ (2) sample. SEM indicates that the two samples exhibit polyhedral shapes. The cyclic voltammogram test demonstrates that reduction-oxidation reactions take place at different voltages for the two samples. The prepared sample of LiNi_0.5Mn_1.2Ti_0.3O₄ with Mn³⁺ ions exhibits excellent cycle performance at different current rates. Its discharge capacity is 133.9 mAh/g at 0.1C.     

Mechanism exploration of enhanced electrochemical performance of single-crystal versus polycrystalline LiNi0.8Mn0.1Co0.1O2

Single-crystal LiNi_0.8Mn_0.1Co_0.1O₂(SC-811),which offers better cycle performance compared to the polycrystalline counterpart,has received great attention.We report herein the synthesis of SC-811 with a grain size of 2-4 μm by washing and reheating method,which compares with conventional polycrystalline LiNi_0.8-Co_0.1Mn_0.1O₂(PC-811).The discharge capacity of SC-811 reaches 152.1 mAh·g^-1 after 100 cyc...     

Effects of synthesis conditions on the structural and electrochemical properties of layered LiNi1/3Co1/3Mn1/3O2 cathode material via oxalate co-precipitation method

The uniform layered LiNi_1/3Co_1/3Mn_1/3O₂ cathode material for lithium ion batteries was prepared by using (Ni_1/3Co_1/3Mn_1/3)C₂O₄ as precursor synthesized via oxalate co-precipitation method in air. The effects of calcination temperature and time on the structure and electrochemical properties of the LiNi_1/3Co_1/3Mn_1/3O₂ were systemically studied. XRD results revealed that the optimal calcination conditions to prepare the layered LiNi_1/3Co_1/3Mn_1/3O₂ were 950°C for 15 h. Electrochemical measurement showed that the sample prepared under the such conditions has the highest initial discharge capacity of 160.8 mAh/g and the smallest irreversible capacity loss of 13.5% as well as stable cycling performance at a constant current density of 30 mA/g between 2.5 and 4.3 V versus Li at room temperature.