Failure mechanism of bulk silicon anode electrodes for lithium-ion batteries

Silicon has been investigated extensively as a promising anode material for rechargeable lithium-ion batteries. Understanding the failure mechanism of silicon-based anode electrodes for lithium-ion batteries is essential to solve the problem of low coulombic efficiency and capacity fading on cycling and also to further commercialize this very new energetic material in cells. To reach this goal, the structure changes of bulk silicon particles and electrode after cycling were studied using ex-situ scanning electron microscopy (SEM) and X-ray diffraction (XRD) techniques. The SEM images indicated that the microstructural changes of the bulk silicon particles during cycling led to a layer rupture of the electrode and then the breakdown of the conductive network and the failure of the electrode. The result contributes to the basic understanding of the failure mechanism of a bulk silicon anode electrode for lithium-ion batteries.     

Electronic structure of LiSi

Silicon is of special interest in lithium-ion batteries (LIBs) since it has large theoretical specific capacity or volumetric capacity. The crystal structure, charge distribution and density of states of LiSi as the Li-poorest side compound at the start of Li intercalation mechanism for Si anode in LIBs has been studied by using density functional theory (DFT) calculations. The triangular pyramids are formed by four Li atoms in LiSi. Compared to the charge density of crystalline Si, the SiSi covalent bonds in LiSi become weak due to Li intercalation. On the other hand, the electrons around the Li atoms in LiSi increase compared to those in metallic Li. The Li atoms in LiSi have negative charge of 0.83–0.84. These electrons, which are transferred from p electrons in the Si atoms, are mainly made of p electrons of the Li atoms. When considering the lithium intercalation reaction from crystalline Si to LiSi, the average intercalation voltage is about 0.4 V.     

In-situ Synthesis of Coral-Like Molybdenum Phosphide (MOP) Microspheres for Lithium-Ion Battery

Molybdenum phosphide (MoP) has attracted extensive attention as promising anode candidates for lithium-ion batteries owing to its high specific capacity,low potential range and low polarization.However,severe volume changes and intrinsic low conductivity are major challenges for further application of MoP electrode materials.In this work,a coral-like MoP microsphere encapsulated by N-doped carbon (MoP@NDC) was successfully prepared through annealing the precursor derived from self-polymerization of dopamine with phosphomolybdic acid.The introduction of carbon framework not only serves as matrix to confine MoP nanocrystals from aggregations,but also improves the electrochemical conductivity and facilitates lithium ion or electron transport on the surface of MoP.Such hierarchical structure delivered high discharge capacity of 495 mAh g-1 after 300 cycles with 90.1％ capacity retention,which could be attributed to the synergistic effects of MoP nanoparticles and conductive carbon network.This design strategy shows MoP@NDC electrode with applicable application as anode in lithium-ion battery.     

可充锂电池的锂金属电极枝晶的抑制

全固态可充锂二次电池的循环性能受到负极锂金属表面形成的枝晶影响。研究了一种能够有效抑制金属锂电极表面枝晶形成的方法。利用等离子体处理隔膜表面,在表面接枝上磺酸基,可以有效地稳定金属锂/隔膜界面,抑制枝晶形成,有效提高锂金属电极的循环稳定性。基于局域微电池模型提出了这种枝晶形成被有效抑制的机理。     

Electrochemical lithium storage performance of ternary Zn-Co-Ni alloy thin film as negative electrodes by electrodeposition method

Ternary Zn-Co-Ni alloy film electrode as an anode has been investigated, for the first time, for the purpose of electrochemical lithium storage in lithium-ion batteries. In this study, the ternary Zn-Co-Ni alloy film electrode is prepared by electroplating method. The electrodes were examined using X-ray diffraction (XRD), FE-SEM with EDX, and impedance studies. The electrochemical results demonstrate that the Zn-Co-Ni alloy film electrode delivers an initial discharge capacity of 281 mAh g⁻¹ and improves to 650 mAh g⁻¹ at the end of 30th cycling with no capacity fading at 0.1 C rate. The charge-discharge properties of the Zn-Co-Ni alloy film electrode are as follows: insertion capacity of 650 mAh g⁻¹ and delithiation capacity of 512 mAh g⁻¹ in the 30th cycling, coulombic efficiency of about 80.0% and good cycling behavior. The results suggest that the ternary Zn-Co-Ni alloy thin film electrode obtained via electroplating shows a good candidate anode material for lithium-ion batteries.     

Electrolytic Co,Ni-bimetalsulfide composites with hydrophilizated multi-wall carbon nanotubes in a prototype lithium accumulator

Electrolytic Co, Ni-bimetalsulfide composites with hydrophilizated multiwall carbon nanotubes (Co, Ni-S, C) appear to be more promising electrode materials in the redox reaction with lithium than the composites of the transition metal sulfides with graphites. The discharge capacity of Co, Ni-S, C-composites in the prototype lithium accumulator (550–725 mA h/g) exceeds the theoretic discharge capacity of graphite (372 mA h/g) used in commercial lithium-ion batteries.     

锂离子电池用石墨负极材料改性研究进展

石墨是目前商业化锂离子电池应用最广的负极材料,日益增长的市场需求对石墨负极材料的储锂性能提出了更高的要求。概述了锂离子电池的工作原理和石墨嵌锂机制,针对石墨负极材料理论比容量(372 mA.h/g)较低和电解液兼容性较差等问题,总结了近年来石墨负极材料的改性手段,主要分为表面改性和结构调控等2类,其中表面改性技术包括氧化和卤化处理,特点是通过调控界面化学性质,可增强石墨结构的稳定性,促进稳定SEI膜的形成,但对于石墨储锂容量的提升非常有限;结构调控包括剥层法和缺陷构筑法,特点是通过扩大石墨层间距、降低石墨维度及在石墨结构上构筑缺陷,从而增加锂离子的活性位点,提供更多锂离子扩散通道,缓解循环过程中的体积变化,改善石墨与电解液的相容性,显著提升石墨的储锂性能。最后对石墨负极材料的未来发展趋势进行了展望。     

LiPON固体电解质膜对金属锂电极的保护作用

制备LiPON固体电解质薄膜,通过电沉积手段获得由LiPON膜保护的金属锂电极,测试该电极在有机电解液体系中的电化学性质。结果表明：LiPON膜的存在,抑制了锂电极和电解液之间的非法拉第反应,使锂电极具有更加稳定的电极/电解液界面。由于LiPON膜的保护作用,金属锂电极在充放电循环中也表现出优越的界面稳定性,从而获得更高的库伦循环效率和更好的电池循环寿命。     

1,3-dioxolane pretreatment to improve the interfacial characteristics of a lithium anode

1,3-dioxolane （DOL） was originally used to pretreat a lithium metal electrode to improve its interfacial characteristics. Electrochemical impedance spectra （EIS） meastLrements revealed that, after the DOL pretreatment, the lithium electrode had better interfacial stability during immersion in electrolyte and as repeated charge/discharge cycles. It was proved by SEaM that the pretreated one has smoother morphology and less dendrite after repeated charge/discharge cycles. Consequentially, benefiting from the better interface characteristics of the lithium electrode, the rechargeable lithium cell with a DOL-pretreated lithium anode had the obviously enhanced discharging performance and better cyclability.     

锂离子电池电解液过充添加剂的行为

制备了3种1 mol/L LiPF6电解液,溶剂组成分别为:1)碳酸乙烯酯,碳酸二甲酯和碳酸甲乙酯;2)碳酸乙烯酯,碳酸二甲酯,碳酸甲乙酯和4%联苯;3)碳酸乙烯酯,碳酸二甲酯,碳酸甲乙酯和4%环己基苯.采用线性电压扫描法、锂循环效率法、锂离子电池的循环性能法和3 C倍率过充的方法测试了联苯与环己基苯电解液过充添加剂的行为.结果表明:环己基苯是一种较实用的锂离子电池电解液过充添加剂,环己基苯的电化学稳定性比联苯的高,环已基苯的氧化电势为4.72 V(vs Li/Li ),联苯的为4.54 V(vs Li/Li );以1 mA电流循环20次后,联苯的铂电极锂循环效率为15.7%,环己基苯的为59.3%;锂离子电池以1 C循环150次后,环己基苯的容量保持率为88%,联苯的为76.3%.环己基苯与联苯添加剂都改善了锂离子电池的耐过充性能,且两者的效果十分接近.     

磷酸铁锂正极墨水配制及其电化学性能研究

磷酸铁锂(LiFePO₄, LFP)作为锂离子电池正极材料因其放电容量大、价格低廉和对环境无污染受到广泛关注。本研究旨在制备出适用于微电子打印机的性能优良的磷酸铁锂及相应复合材料正极墨水。通过配制不同浓度的磷酸铁锂墨水并制备成电极,研究最优浓度墨水制备成电极的电化学性能。研究表明,倍率为0.1 C时,打印浓度为10%的磷酸铁锂电极放电比容量高达142 mAh·g^-1,基于磷酸铁锂具有较差的导电性,选择加入少量还原氧化石墨烯提高其导电性。还原氧化石墨烯质量分数为0.6%时,磷酸铁锂和还原氧化石墨烯复合材料放电比容量达152.1 mAh·g^-1,库伦循环效率为99.2%,说明引入还原氧化石墨烯有利于提高材料整体性能。     

Effect of sulfur electrode composition on the electrochemical property of lithium/PEO/sulfur battery

The lithium/sulfur cell is very attractive because of its high theoretical specific capacity and low production cost. The sulfur electrode is prepared from sulfur, with carbon as an electronic conductor and PEO as an ionic conductor. We changed the carbon content of a 50 wt.% sulfur electrode from 10 wt.% to 40 wt.%. The lithium/PEO/sulfur cell showed two plateau potential regions (2.4 V, 2.1 V) and high discharge capacity, i.e., 1484 mAh/g (88% utilization) for optimum composition. The discharge capacity decreased drastically by charge-discharge cycling. The degradation rate as well as the first discharge capacity depended on the composition of the sulfur electrode. The optimum composition of the 50 wt.% sulfur electrode was 30 wt.% carbon and 20% PEO.     

Effect of n-Al2O3 on electrochemical nucleation and chemical binding interaction in nickel electrodeposition

The electrochemical nucleation mechanism of nickel on the vitreous carbon electrode from n-Al2 Os/Ni composite brush plating system was investigated using potential step method. The interaction between nano-alumina and matrix metal was researched by X-ray photoelectron spectrometry. The results show that the nano-alumina leads to the increasing of the nuclei density, nucleation rate constant and crystal growth rate during nickel electrocrystallization. Nano-alumina is found to be beneficial for nucleation and growth of nickel. During the electrodeposition process, some nanoparticles are captured effectively on the growing metal surface. As the absorbed nickel atoms are diffusing on electrode surface, some of them arrive at the interface between the captured nano-alumina and the growing metal surface. The unsaturated bond of oxygen on nano-alumina surface can capture some of the absorbed nickel atoms and form nickel-oxygen chemical bond. The new nucleation and growth sites of nickel atoms appear at the interfaces between nanoparticles and metal growing surface. Nanoparticles are embedded gradually in the newly deposited nickel atoms, which leads to the formation of the composite coating. The results indicate that the nano-alumina takes part in the electrode reaction and the unsaturated chemical bond of oxygen on nanoparticle surface can combine with the absorbed nickel atoms by way of chemical bond.     

阀控密封铅酸蓄电池反应机理分析

作为电动车用电池，铅酸蓄电池仍然存在着比能量低、充电接受能力差、活性物质利用率低等缺点，板栅的腐蚀、负极硫酸盐化、析氢、析氧等现象会引起充放电过程中不必要的副反应，这将导致电池容量的损失及衰减。总结了阀控密封铅酸蓄电池（VRLA）及其正负极的反应机理，并对各种反应机理做了比较和评价。详细介绍了负极反应中溶解沉淀机理、固相反应机理和固相反应-溶解沉淀机理，以及正极反应中胶体结构上的PbO2形成机理、液相生成机理和固相生成机理。最后提出了提高铅酸蓄电池性能的几种方法，并对铅酸蓄电池的发展做出了展望。     

Electrochemical performance of mechanochemically prepared polyaniline doped with lithium salt

Oxides and phosphates of transition metals are now predominant cathode materials of lithium-ion batteries. Organic redox active materials, conducting polymers in particular, could be a more environmentally friendly alternative. But their electrochemical characteristics were of insufficient level as to the charge capacity, rate capability and cyclability. Here, electrochemical performance of lithium salt doped polyaniline samples prepared by mechanochemical and chemical methods is comparatively analyzed as an active component of cathode masses of lithium batteries. It is shown that mechanochemically prepared polyaniline possesses specific capacity close to the theoretical limit as well as high rate capability and cyclability during prolonged charge–discharge.     

热处理过程中钛层对钛钢爆炸复合板钢侧组织转变的影响

利用光学显微镜、扫描电子显微镜研究了不同温度下钛层对钛钢爆炸复合板钢侧组织转变的影响。结果表明:有钛层时,钢侧结合界面上会形成脱碳层。当850℃及以下温度加热时,在波头的漩涡处产生粗大的铁素体晶粒,而在950℃保温时,在波峰处产生粗大的铁素体。剥离钛层时,只在波头的漩涡处产生铁素体区,随着温度的升高,铁素体区减小。产生这种现象的主要原因是钛层的存在,碳元素向结合界面扩散形成TiC,在结合界面附近形成铁素体区。     

Study of the corrosion behaviour of Cu-10Sn bronze in aerated Na2SO4 aqueous solution

Investigation of the electrochemical behaviour of Cu-10Sn (wt.%) alloy has been conducted in aerated aqueous sulphate solution and compared to that of pure Cu and Sn. Eoc versus time and cathodic and anodic polarizations have been performed as a function of the initial sulphate concentration, the rotation speed of the electrode and the immersion time. The surface layer have been characterized by scanning electron microscopy (SEM) and analyzed by energy dispersive spectrometry (EDS) and Fourier transform infrared spectroscopy (FTIR). The anodic behaviour evidences a Cu dissolution phenomenon on the corrosion layer limited by migration process rather than diffusion. The corrosion process conducts to preserve the original surface of the electrode and conducts to an internal growth at the layer/alloy interface, from the initial surface towards the unaltered substrate. The interphase behaviour is governed by the layer formed at Eoc under the experimental conditions and its evolution during the time. Hydroxyl-oxy and sulphate Cu and Sn compounds recover the surface and confer to the interface a blocking behaviour mainly due to the presence of the tin compounds in the layer. The global interphase behaviour matches the Type-I model of blocking adherent layer with decuprification phenomenon evidenced on archaeological bronzes.     

锡电极嵌锂过程的交流阻抗谱

采用交流阻抗谱研究锡电极的首次嵌锂和第二次嵌锂过程,对比锡纳米阵列电极、锡薄膜电极和锡箔3种不同材料微观结构对电极交流阻抗谱特征的影响。用等效电路模型分析交流阻抗谱,得到嵌锂过程电化学特征参数与电位关系。结果表明:锡纳米阵列电极与锡薄膜、锡箔电极具有不同交流阻抗谱特征,锡纳米阵列电极在中频区出现双电层阻抗;首次嵌锂时在1.6~0.8 V之间形成固体电解质膜(SEI);电极材料微观结构显著影响锡电极的SEI膜电阻、Warburg阻抗和锂离子扩散速率;锡纳米阵列电极上的SEI膜电阻和Warburg阻抗最小,锂离子扩散能力最强;锡纳米阵列电极上锂的扩散系数为4.4×10-15~1.4×10-11 cm2/s;锂扩散系数随电位变化显著。     

液态锂锡合金中氚解吸行为的模拟

液态锂锡合金是很有前途的聚变-裂变混合堆(FFHR)包层产氚材料。为完成FFHR包层氘-氚燃料循环系统的概念设计,以金属与氢的作用理论为基础,建立了液态Li25Sn75中氚解吸行为的动力学模型,模拟和分析了合金温度、氚分压、氦流量对解吸气中氚分压的影响以及氚在液态Li25Sn75中的传质系数、解吸率和吸附率。计算结果表明：在673~873 K的温度范围内,氚从液态Li25Sn75到气相的整个解吸过程,虽然包含了氚在熔融合金气泡中的扩散与对流、氚通过与气-液界面相连合金层的扩散、在界面发生的氚原子重组多相反应、氚通过气相边界层的扩散和气相中氚的扩散与对流5个子过程,但起决定作用的是氚在合金内的扩散和气-液界面的多相反应重组     

Effect of π-Al_2O_3 on electrochemical nucleation and chemical binding interaction in nickel electrodeposition

1 INTRODUCTION In recent years , nanometer composite electric brush plating technology has been developed.It is a kind of novel surface repairingtechnology ,which can prepare excellent surface coating[1 7]. The technology is at the stage of development , its foundational theory and application field must be expended. Up to now, investigations have been mainly focused on preparing coating,testing per- formance and developing new brush-plating solu- tion,little attentionis paidto the study …