Development and application of phase diagrams for Li-ion batteries using CALPHAD approach

Phase diagrams provide fundamental knowledge about design map of new electrode materials for Li-ion batteries. The CALPHAD (CALculation of PHAse Diagrams) approach is widely applied to the development of phase diagrams and property diagrams in a thermodynamic language. Within the CALPHAD framework, the theoretical modeling can be performed to predict phase equilibria, thermodynamics, electrochemical and physical properties of electrodes. This review provides the successful application of high quality calculated phase diagrams and thermodynamic property diagrams in CALPHAD investigation to both cathodes and anodes of Li-ion batteries, including Li–Co–O, Li–Ni–O, Li–Co–Ni–O, Li–Mn–O, Li–Cu–O, Li–Si, Li–Sb and Li–Sn systems with. The intensive CALPHAD-type research may also predict electrochemical properties, cell performance of the Li-ion batteries to achieve more efficient development of electrode materials.     

Effect of Calcining Temperature on the Structure of Li_4Ti_5O_(12)

1 Introduction Recently there had considerable interest in Li4Ti5O12 as a potential anode for use in Li-ion batteries. Usually, it was used as an anode combined with a high voltage cathode[1-5]. It has many advantages compared to the currently used graphite. For example, it presents virtually unlimited cycle life due to zero strain or volume change when lithium intercalates into and de-intercalates from[6]. Generally, Li4Ti5O12 was prepared by a solid-state reaction from stoichiometric amounts of Li2CO3 and TiO2. However, the different calcining temperature has strong influence on the structure and electrochemical properties of Li4Ti5O12.     

Effect of Polyaniline on Electrochemical Performance of LiFePO_4

1 Introduction LiFePO4 has received much attention as a kind of next-generation cathode materials for lithium ion batteries. To improve its electrochemical performance, researchers have been working to overcome two major disadvantages of LiFePO4 such as the low electrical conductivity and the small Li-ion diffusivity. The latter can be solved by reducing the particle size while the former can be improved by coating a layer of carbon on the surface of LiFePO4 particles[1]. More researchers have carried out carbon coating[2], but there are few reports focusing on coating conductive polymer. Here we report a series of LiFePO4 composite materials coated with polyaniline (PAn) and their electrochemical properties.     

Application prospects of high-voltage cathode materials in all-solid-state lithium-ion batteries

All-solid-state lithium-ion batteries are lithiumion batteries with solid-state electrolytes instead of liquid electrolytes.They are hopeful in solving the safety problems of lithium-ion batteries,once their large capacity and long life are achieved,they will have broad application prospects in the field of electric vehicles and large-scale energy storage.The working potential window of solid electrolytes is wider than that of liquid electrolytes,so high-voltage cathode materials could be used in all-solidstate lithium-ion batteries to get higher energy density and larger capacity by elevating the working voltage of the batteries.The spinel LiNi0.5Mn1.5O4material,layered Li–Ni–Co–Mn–O cathode materials and lithium-rich cathode materials can be expected to be applied to all-solid-state lithium-ion batteries as cathode materials due to their highvoltage platforms.In this review,the electrochemical properties and structures of spinel LiNi0.5Mn1.5O4material,layered Li–Ni–Co–Mn–O cathode materials and lithiumrich cathode materials are introduced.More attentions are paid on recent research progress of conductivity and interface stability of these materials,in order to improve their compatibility with solid electrolytes as cathode materials in all-solid-state lithium-ion batteries and fully improve the properties of all-solid-state batteries.Finally,the existing problems of their application in all-solid-state lithium-ion batteries are summarized,the main research directions are put forward and their application prospects in all-solid-state lithium-ion batteries are discussed.     

The Effect of Pore Size of Nanoporous Material for Lithium Ion Batteries

1 Results 3-dimensionally ordered mesoporous materials have been used as electrode materials for lithium ion batteries to improve their electrochemical performance by decreasing the polarization during cycling.Our synthesize nanoporous TiO2 particles without substrate present enhanced cycle performance compared with that of previous reports[1]. Here we report our results referring to that nanoporous TiO2 materials with different pore sizes exhibit different electrochemical performance.The detail procedure to synthesize nanoporous TiO2 can be found in reference[1].The nanoporous titania particles with different pore sizes of 80 nm,250 nm and 1 μm were synthesized by adopting polystyrene (PS) colloidal crystal particles with average particle size of 100,600 nm and 1.7 μm as template,differently.It is obvious to find in Fig.1 that all the nanoporous titania present good cycle performance at each rate.The titania with pore size of 250 nm present the highest capacity.The surface area and dispersion of conductive additives have great impacts on the capacity of materials with different pore size.     

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.     

Synthesis and Electrochemical Properties of Nanostructured Cathode Materials for Lithium Batteries

1 Results For electrode materials in lithium batteries,a high surface area can provide higher electrode/electrolyte contact areas,thus eventually causing the shorter diffusion paths with the particles,and provides more facile intercalation for Li ions[1-4].In addition,reduced strain of intercalation and contributions from charge storage at the surface may also contribute to Li capacity,compared with bulk counterparts.In this regard,I am going to talk about the preparation and electrochemical properties of the cathodes with various nanostructures,such as nanoplate,nanoparticle,nanowire,and hollow,mesopores.For instance,layered Li0.88[Li0.18Co0.33Mn0.49]O2 nanowires prepared by using Co0.4Mn0.6O2 nanowires as a precursor at 200 ℃ showed superior rate capability,compared with the bulk analogues,showing reversible capacity of 230 mAh/g between 2 and 4.8 V even at high rate of 3 600 mA/g.     

Synthesis of gold-doped TiO2 nanotubes

Nanostructured materials have been the focus of scientific research due to their unusual physical and chemical properties. Therein, nanoscale TiO2 is one of the most investigated materials owing to its significance for applications in heterogeneous catalysis, nonlinear optical devices, gas sensors and photoelectrochemical solar cells.Many studies have been devoted to the improvement of TiO2 activity by doping noble metals. Among them.     

Nanostructured transition metal nitride composites as energy storage material

There are growing demands for the next generation lithium ion batteries with high energy density as well as high power performance for renewable energy storage and electric vehicles application.Recently,nanoscale materials with outstanding energy storage capability have received considerable attention due to their unique effect caused by the reduced dimensions.This review describes some recent developments of our group in research of transition metal nitride nanocomposites in application of energy storage,especially for lithium ion battery and supercapacitor.The strategies of mixed conduction(electron and ion) network with a favorable charge transportation interface in the design of the nanocomposites for such devices are highlighted.     

Safety characteristics of Li-ion batteries evaluated by in situ measurement techniques

Li-ion batteries hold an important place in the field of high power batteries because of their high open circuit voltage and associated high energy density. However, the safety is less satisfactory; therefore, the study of the factors that affect the safety of Li-ion batteries has much meaning to the safety design. In this paper, a set of apparatus was developed for in situ measurements, and several commercial materials including electrolyte, separator and electrode materials for Li-ion batteries were investigated by the in situ method. The results showed： 1） The electrolyte vapor pressure is influenced significantly by the component with low boiling point and increases rapidly with the increasing of temperature; 2） the shutdown of separator occurs at around 135℃ and the impedance increases approximately by two orders of magnitude; 3） carbon anode materials affect the most the volume changes of the cell, and the change for a graphite anode is much greater than that of a glassy carbon anode.     

三维VO2(B)纳米花制备及其电化学性能研究

通过水热法制备了三维的VO₂(B)纳米材料;对其形貌结构的控制合成及其电化学性质进行了探索.实验结果表明,反应产物的形貌可以通过改变还原剂草酸的浓度及其反应的时间来改变.电化学测试结果显示,水热合成的带状VO₂(B)纳米花材料相比其片状结构具有更好的电化学性能,比容量高,循环可逆性更好,因此在锂电池的正极材料应用上有更好的前景.     

The Effect of Pore Size of Nanoporous Material for Lithium Ion Batteries

1 Results 3-dimensionally ordered mesoporous materials have been used as electrode materials for lithium ion batteries to improve their electrochemical performance by decreasing the polarization during cycling.Our synthesize nanoporous TiO2 particles without substrate present enhanced cycle performance compared with that of previous reports[1]. Here we report our results referring to that nanoporous TiO2 materials with different pore sizes exhibit different electrochemical performance.The detail procedu...     

Practical development and challenges of garnet-structured Li7La3Zr2O12 electrolytes for all-solid-state lithium-ion batteries: A review

All-solid-state Li-ion batteries (ASSLIBs) have been widely studied to achieve Li-ion batteries (LIBs) with high safety and energy density. Recent reviews and experimental papers have focused on methods that improve the ionic conductivity, stabilize the electrochemical performance, and enhance the electrolyte/electrode interfacial compatibility of several solid-state electrolytes (SSEs), including oxides, sulf-ides, composite and gel electrolytes, and so on. Garnet-structured Li7La3Zr2O12 (LLZO) is highly regarded an SSE with excellent application potential. However, this type of electrolyte also possesses a number of disadvantages, such as low ionic conductivity, unstable cubic phase, and poor interfacial compatibility with anodes/cathodes. The benefits of LLZO have urged many researchers to explore effective solutions to over-come its inherent limitations. Herein, we review recent developments on garnet-structured LLZO and provide comprehensive insights to guide the development of garnet-structured LLZO-type electrolytes. We not only systematically and comprehensively discuss the preparation, ele-ment doping, structure, stability, and interfacial improvement of LLZOs but also provide future perspectives for these materials. This review expands the current understanding on advanced solid garnet electrolytes and provides meaningful guidance for the commercialization of ASSLIBs.     

Synthesis and Electrochemical Properties of Nanostructured Cathode Materials for Lithium Batteries

1 Results For electrode materials in lithium batteries,a high surface area can provide higher electrode/electrolyte contact areas,thus eventually causing the shorter diffusion paths with the particles,and provides more facile intercalation for Li ions[1-4].In addition,reduced strain of intercalation and contributions from charge storage at the surface may also contribute to Li capacity,compared with bulk counterparts.In this regard,I am going to talk about the preparation and electrochemical properties o...     

琼脂含量对Li2TiO3陶瓷微球制备工艺的影响

Li2TiO3陶瓷具有Li原子密度较高、化学稳定性好、氚滞留量低、与结构材料的相容性好、低温下氚的释放性能优异等优点,已经成为聚变反应堆包层用氚增殖剂候选材料之一。以琼脂为凝胶剂、Li2CO3和TiO2粉体为原料,探讨了直接湿法制备Li2TiO3陶瓷微球的成球机理,研究了琼脂和水的含量对陶瓷微球球形度和显微结构的影响。结果表明,琼脂质量分数为Li2TiO3粉体质量的3%、水浴温度为85℃时所制备的陶瓷微球具有较高的球形度。1 300℃烧结的Li2TiO3陶瓷微球具有较高的烧结密度,可达理论密度的84.9%。陶瓷微球富含微孔结构,孔径尺寸主要分布在0.03～0.20μm。     

以竹纤维为模板制备微米管状Li4Ti5O12负极材料

以竹纤维为模板,Ti(OC4H9)4和Li(Ac).2H2O为原料,用模板法制备锂离子电池微米管状Li4Ti5O12负极材料。采用XRD,SEM,BET,充放电实验和交流阻抗等对合成材料的结构、形貌和电化学性能进行表征。研究结果表明:制备的微米管状Li4Ti5O12负极材料由尖晶石型纳米Li4Ti5O12颗粒构成,具有较大的比表面积,该材料具有良好的电化学性能,在0.5~3.0 V,0.1C倍率下的首次放电比容量为178 mA.h/g,充放电循环100次后放电比容量仍保留162 mA.h/g,且倍率性能优异。     

新型高能化学电源电极过程及其研究方法的进展

简要介绍国际上新型高能化学电源的一些研究现状,并主要结合课题组的研究工作,就锂离子电池纳米相电极材料,金属氢化物电极表面电化学性能及其相关电极过程和化学电源研究中谱学电化学方法的应用等进行了总结和回顾。     

A deformable spinel-type chloride cathode with high ionic conductivity for all-solid-state Li batteries

All-solid-state Li batteries (ASSLBs) are now considered to be next-generation energy storage devices due to their advantages in safety and energy density. With liquid electrolytes replaced by solid electrolytes, novel cathode active materials (CAMs) with different characteristics are needed. The solid-solid contact in ASSLBs requires CAMs to have good deformability. In addition, higher ionic conductivity is also essential to reduce the mass of the Li-ion conductive agent, thus accessing a higher overall capacity. Herein, we report a spinel-type chloride cathode Li_2?2xMn_1?xZr_xCl₄, which has good deformability and high ionic conductivity (up to 0.16 mS?cm?1 at 25 °C). The ASSLB using the optimal composition of LiMn_0.5Zr_0.5Cl₄ as the cathode exhibits promising cycling stability for 200 cycles at room temperature.