Synthesis and electrochemical properties of bioderived silicon particles for lithium ion battery anodes

Journal of Materials Science: Materials in Electronics - Silicon is a promising high-capacity anode material for lithium ion batteries, but still suffers from the major issue of poor cyclability...     

不同粒径球形LiFePO4的制备及其性能研究

利用控制结晶法制备了粒径约为1、5、10μm球形FePO4,以此为前驱体通过碳热还原法合成不同粒径的球形LiFePO4正极材料.采用XRD、SEM以及恒流充放电测试等手段对材料的结构、形貌和电化学性能进行表征,并比较了不同粒径产物的振实密度.合成的材料较好地保持了球形形貌,大粒径的样品振实密度高达2.03 g/cm3,...     

PAA类黏结剂在锂电池中电化学性能研究进展

黏结剂是维持极片完整性必不可少的部分,对电池比容量、循环稳定等性能的提高非常重要。聚丙烯酸(PAA)因含有较多极性官能团,可溶于水,而被用作锂电池正负极黏结剂。PAA黏附性好,但极性基团使得分子链间形成的氢键导致PAA链刚性较大,不利于维持充放电过程中极片的完整性,因此,控制PAA官能团数量、改变官能团种类及PAA分子链结构,对锂电池电性能的提高势在必行。本文综述了近几年锂电池用PAA黏结剂的研究进展,重点介绍了PAA黏结剂的结构特性、改性及应用方式及其对不同种锂电池首次库伦效率、循环稳定性和阻抗性能的影响,并对PAA黏结剂的未来改性研究热点做了展望,探索PAA引入不同结构的弹性或导电聚合物后,对于黏结剂本身性能的影响,改善界面性能,以适用于不同活性材料正负极,提高锂离子传输速率,更好地提高锂电池的使用性能。     

Facile synthesis of spherical nanostructured LiCoPO4 particles and its electrochemical characterization for lithium batteries

Spherical nanostructured LiCoPO₄ (SN-LiCoPO₄) particles were facilely synthesized by citric acid assisted spray pyrolysis at 600 °C in air atmosphere. The X-ray diffraction pattern of the synthesized LiCoPO₄ samples was indexed to olivine structure with a Pnma space group. Scanning electron microscopy analysis showed that the primary particle size of LiCoPO₄ reduced due to citric acid additive into a precursor solution. This fact might indicate that the citric acid additive restricted the agglomeration and growth of primary particles in a droplet to solid particle conversion process of spray pyrolysis synthesis. The first discharge capacity of SN-LiCoPO₄ electrode was 135 mAh g⁻¹ at 0.05 C in a voltage range of 2.0–5.1 V, corresponding to approximately 81% of its theoretical capacity (167 mAh g⁻¹). Moreover, the rate capability of SN-LiCoPO₄ electrode was superior to that of bare LiCoPO₄ electrode_, delivering a discharge capacity of 73 mAh g⁻¹ even at 0.5 C. Cyclic voltammetry and electrochemical impedance spectroscopy data demonstrated that the SN-LiCoPO₄ electrode had lower polarization and faster redox reaction kinetics for the charge and discharge processes. These results were attributed to the reduced primary particle sizes that shortened the lithium ion diffusion pathway during the charge and discharge processes for lithium batteries.     

软化学法合成正交结构LiMnO_2及其电化学性能

研究以氢氧化锂和三氧化二锰为原料,用软化学法制备具有正交结构的锂离子电池正极材料LiMnO2。用X射线衍射法确定了材料的结构,用扫描电镜考察了材料形貌和反应时间的关系,观察结果显示得到的LiMnO2的粒子尺寸在300~500nm。结合循环伏安法和交流阻抗分析研究了合成条件对材料组织结构、尺寸与电化学性能的影响。材料的电化学性能测试结果表明,合成的正交扭曲结构LiMnO2(o-LiMnO2)材料在电化学过程中初期表现了较好的电化学性能。但材料在电化学过程中逐步向尖晶石结构相LiMn2O4转变,容量产生衰减,其循环寿命有待更进一步改善。     

Mesoporous SnO2@carbon core-shell nanostructures with superior electrochemical performance for lithium ion batteries

SnO2@carbon nanostructure composites are prepared by a simple hydrothermal method. The composite exhibits unique structure, which consists of a mesoporous SnO2 core assembled of very small nanoparticles and a carbon shell with 10 nm thickness. The mesoporous SnO2@carbon core-shell nanostructures manifest superior electrochemical performance as an anode material for lithium ion batteries. The reversible specific capacity of the composite is about 908 mAh g(-1) for the first cycle and it can retain about 680 mAh g(-1) after 40 charge/discharge cycles at a current density of 0.3 C. Moreover, it shows excellent rate capability even at the high rate of 4.5 C. The enhanced performance was attributed to the mesoporous structure and a suitable carbon coating.     

Synthesis and electrochemical characterization of Si-Mn alloy anode materials for high energy lithium secondary batteries

The Si-Mn alloys as anode active materials were prepared by mechanical milling and calcination at three different temperatures like 600, 700, and 800 degrees C. The alloys were characterized by X-ray diffraction, field emission-scanning electron microscopy, field emission-transmission electron microscopy, and electrochemical cycling within a range of 2.5 V to 0.01 V versus Li/Li+. We found that the Si-Mn alloy calcined at 800 degrees C exhibited (i) an enhanced reversible capacity during the intercalation and de-intercalation process and (ii) a reduction in fading capacity characteristic due to modified structural and interfacial properties. Increasing the calcination temperature could improve the electrochemical performance of these materials, especially at 800 degrees C. Hence this alloy possibly suited to apply for lithium rechargeable batteries. The reversible capability after fourth cycling increases in the range of 95% to nearly 99% coulombic efficiency during the following intercalation and de-intercalation process. The Si-Mn alloy has the potential to be suitable for use as an anode active material in lithium rechargeable batteries.     

Structural and electrochemical properties of Ag nano-dots combined amorphous Si electrodes for thin-film lithium rechargeable batteries

We have one-pot fabricated Si-based nanocomposite electrodes containing Ag nano-dots for thin-film Li rechargeable batteries by a co-sputtering method. The structural and electrochemical properties of the Si/Ag nanocomposite electrodes are investigated via transmission electron microscopy (TEM), field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), and cycler. The TEM and XRD results show that crystalline Ag nano-dots (approximately 5-9 in size) are well-dispersed within an amorpohous Si matrix. It is shown that the Si/Ag nanocomposite electrode shows much better structural stability than the Si only sample. It is also shown that the Si/Ag nanocomposite electrode shows superior capacity retention compared to the Si only electrode. The results indicate that the presence of the Ag nano-dots is important minimizing the formation of cracks in the electrode, so leading to the better life-time for thin-film Li rechargeable batteries.     

Synthesis of titania photocatalysts dispersed with nickel nanosized particles

Titania super fine particle photocatalysts containing dispersed nickel nanosized particles were synthesized. The synthesis method was as follows. First, an W/O type emulsion was made with non-ion surfactant. Titania powder with dispersed nickel oxide or nickel hydroxide was synthesized using a solution of nitric acid, nickel and titanium tetra butoxide (TIB). The titania photocatalyst was formed by reduction caused by heat treatment under a suitable reduction condition. Nickel nano-sized particles were distributed in the titania photocatalysts and the amount of hydrogen generated increased in proportion to the surface area of the distributed nickel. The nickel particles dispersed in titania photocatalysts accelerated the generation of rutile as compared to the photocatalyst without nickel.     

Preparation,structure, and electrochemical performance of anodes from artificial graphite scrap for lithium ion batteries

Artificial graphite scrap prepared from petroleum coke with low degree of graphitization was further graphitized under various conditions. Different categories of coke were also treated with the optimum technology. The prepared samples were characterized with X-ray diffraction, ash content determination, morphology observation, and galvanostatic charge and discharge. It was shown in the experiments that the heat treatment temperature should be increased to 2800 °C to remove impurities. Slow heating rate and evacuation technology were beneficial to the growth of graphite crystallite and the improvement of discharge capacity. And the latter condition possessed the larger influences, especially on the growth of crystallite dimension in the b axis direction, degree of graphitization, and discharge capacity. The sample D-3000 prepared from pure needle coke possessed the maximum discharge capacity of 342.1 mAhg⁻¹ among all prepared samples. The linear regression equations between the volume of graphite crystallite and discharge capacity were established.     

纳米二氧化锰的可控制备及其电化学储能机理研究

通过添加十二烷基溴化氨(CTAB)利用液相沉淀法制备了不同形貌的纳米二氧化锰,用扫描电镜、X射线衍射、孔结构以及循环伏安法等分析研究了CTAB添加量对二氧化锰形貌和电化学性能的影响.结果表明,随着CTAB添加量的增加,二氧化锰形貌从长棒状到均匀球状发生规律变化,此外随着颗粒尺寸变小,二氧化锰比容量从162F/g提高到了...     

Synthesis and electrochemical properties of LiNi0.9Co0.1O2 cathode material for lithium secondary battery

Layered LiNi_0.9Co_0.1O₂ cathode material has been successfully synthesized with a calcination time of 0.5 h by a rheological phase reaction method. The obtained powder was characterized by X-ray diffraction (XRD), particle size and particle size distribution, scanning electronic microscope (SEM) and electrochemical measurements. The powder is confirmed to be α-NaFeO₂ structure. Cyclic voltammetry (CV) studies imply that the phase transitions from hexagonal to monoclinic exist during charge–discharge cycling. The LiNi_0.9Co_0.1O₂ cathode demonstrated a good electrochemical property with an initial discharge capacity of 193 mAh g^?1 and capacity retention of 88.6% after 15 cycles.     

Synthesis, characterization and electrochemical studies of LiNi0·8M0·2O2 cathode material for rechargeable lithium batteries

LiNiO₂ and substituted nickel oxides, LiNi_0·8M_0·2O₂ and LiCo_0·8M_0·2O₂ (M = Mg²⁺, Ca²⁺, Ba²⁺), have been synthesized using simple solid state technique and used as cathode active materials for lithium rechargeable cells. Physical properties of the synthesized products are discussed in the structural (XRD, TEM, SEM with EDAX) and spectroscopic (FTIR) measurements. XRD results show that the compounds are similar to LiNiO₂ in structure. TEM and SEM analyses were used to examine the particle size, nature and morphological aspects of the synthesized oxides. The composition of the materials was explored by EDAX analysis. Electrochemical studies were carried out in the range 3–4·5 V (vs Li metal) using 1 M LiBF₄ in ethylene carbonate/dimethyl carbonate as the electrolyte. The doping involving 20% Mg resulted in a discharge capacity of 185 mAhg⁻¹ at 0·1 mA/cm² and remained stable even after 25 cycles. Discharge capacity retention for Mg doped lithium nickelate at 25th cycle was noted to be nearly 7% higher than for the undoped material.     

锂离子电池正极材料LiFePO4的合成及电化学性能

固相反应法合成了新型锂离子电池正极材料LiFePO4,组装成电池后,室温下(23℃)初始比容量为110mAh/g.以蔗糖分解在LiFePO4电池材料的颗粒间覆碳的方法制备了改性的LiFePO4,对LiFePO4进行表面覆碳改性后其电化学性能包括比容量和充放电效率两方面都得到提高.覆碳后正极材料的初始比容量在室温下达到了140mAh/g,比覆碳前增加了30mAh/g,在循环20周后比容量仍维持在125mAh/g左右;覆碳后正极材料的平均充放电效率在23℃和50℃下分别为91%和93%.     

Synthesis and electrochemical properties of nanostructured LiMn2O4 for lithium-ion batteries

Spinel LiMn₂O₄ crystal with the grain sizes of about 15 nm is firstly synthesized by hydrothermal route at 180 °C using MnO₂ as a precursor. The LiMn₂O₄ powders synthesized by hydrothermal technique and sol-gel reaction were investigated by X-ray diffraction (XRD) and Transmission electron microscopy (TEM). The LiMn₂O₄ samples were used as cathode materials for lithium-ion battery, whose electrochemical properties were investigated. The results show that the sample obtained by hydrothermal route has higher capacity than that prepared by sol-gel method.     

锂离子电池斜方锰酸锂阴极材料的合成与表征

用一步固相法合成了斜方锰酸锂,对其进行了表征并确定了前驱体化合物烧结中的转变过程,以及相互化合间的烧结机制．结果表明,随着煅烧温度的升高,杂相减少,生长出主体相斜方锰酸锂．在700℃以上可以生成均一相的层状斜方类球状和棒状锰酸锂颗粒．两种颗粒的粒度分别为1～5μm和5～15μm．在充放电循环中,斜方锰酸锂结构易于向尖晶石结构转变．在2．5～4．5V范围内以20mA／g电流进行充放电循环,斜方锰酸锂的初始充电容量达到247mAh／g,放电容量为133mAh／g,50次循环后,容量保持率为92％．     

Improved electrochemical performance of LiCoPO4 nanoparticles for lithium ion batteries

Single phase LiCoPO4 nanoparticles were synthesized by solid-state reaction. LiCoPO4/Li batteries were fabricated in an argon-filled glove box, and their electrochemical properties were analyzed by cyclic voltammetry (CV) and charge-discharge tests. The structural performance of LiCoPO4 nanoparticles was investigated by X-ray diffraction (XRD) and scanning electron microscope (SEM). The XRD result demonstrated that LiCoPO4 nanoparticles had an orthorhombic olivine-type structure with a space group of Pmnb. The charge-discharge tests indicated that the initial discharge capacity and coulombic efficiency of LiCoPO4/Li batteries were 110 mA h/g and 48% in cut-off voltage range of 3.0-5.3 V, 90 mA h/g and 54% in cut-off voltage range of 3.0-5.1 V, 70 mA h/g and 60% in cut-off voltage range of 3.0-5.0 V, respectively. After 30 cycles, the coulombic efficiency was 78% for 3.0-5.3 V, 88% for 3.0-5.1 V, 91% for 3.0-5.0 V, respectively. These results indicated that the coulombic efficiency of LiCoPO4/Li battery increased upon cycling and upon decreasing in charge upper limit voltage, respectively.