Ni/MH电池过充电过程热效应分析

论文采用二维热模型分析了圆柱型Ni/MH电池在过充电过程中的热效应.实验提供了更为精准的数据以建立精确的热模型.利用石英频率微量热仪对电池的热容量以及电池在不同电流过充电时的发热量和散热速率进行了测量,继而将散热速率曲线拟合成线性函数和三段不同的指数函数.线性阶段之后的散热过程符合数学微分表达式,这些表达式有助于理解过渡阶段和过充电阶段散热速率的变化规律.热传导方程中产热速率采用理论计算值.最后使用FEM模拟了电池在1C,3C,5C充电过程每一阶段末时刻的电池内部温度场分布,结果相对准确.     

Thermal behavior of nickel/metal hydride battery during charging and discharging

This work discusses thermal behavior of Ni/MH battery with experimental methods. The present work not only provides a new way to get more exactly parameters and thermal model, but also concentrates on thermal behavior in discharging period. With heat generation rate gained by experiments with microcalorimeter, heat transport equations are set up and solved. The solutions are compared with experiment results and used to understand the reactions inside the battery. Experiments with microcalorimeter provide more reliable data to create precise thermal model.     

A study on structure-performance relationship of overcharged 18650-size Li4Ti5O12/LiMn2O4 battery

The electrochemical properties and thermal generation behavior of 18650 Li₄Ti₅O₁₂/LiMn₂O₄ batteries were tested before and after overcharge. The experimental results showed that after overcharge, the specific capacity decreased obviously. The higher the current density was, the more obvious the capacity decreased. For instance, the overcharged battery had almost no capacity when the current density increased to 5C. At the same time, the overcharged battery presented a much more apparent thermal runaway trend compared to the normal battery. After measuring the electrochemical impedance spectroscopy of the batteries and characterizing the crystal structure/nanostructure of the electrode materials, these phenomena could be attributed to the following two reasons: (1) the decomposition of the electrolyte arisen from the overcharge process resulted in increased internal resistance; (2) the thermal runaway due to the increased internal resistance resulted in the damage to crystal structure/nanostructure and aggregation of the electrode materials, thus leading to the secondary decrease in capacity.     

Engineering Fast Ion Conduction and Selective Cation Channels for a High‐Rate and High‐Voltage Hybrid Aqueous Battery

The rechargeable aqueous metal‐ion battery (RAMB) has attracted considerable attention due to its safety, low costs, and environmental friendliness. Yet the poor‐performance electrode materials lead to a low feasibility of practical application. A hybrid aqueous battery (HAB) built from electrode materials with selective cation channels could increase the electrode applicability and thus enlarge the application of RAMB. Herein, we construct a high‐voltage K–Na HAB based on K₂FeFe(CN)₆ cathode and carbon‐coated NaTi₂(PO₄)₃ (NTP/C) anode. Due to the unique cation selectivity of both materials and ultrafast ion conduction of NTP/C, the hybrid battery delivers a high capacity of 160 mAh g^?1 at a 0.5 C rate. Considerable capacity retention of 94.3 % is also obtained after 1000 cycles at even 60 C rate. Meanwhile, high energy density of 69.6 Wh kg^?1 based on the total mass of active electrode materials is obtained, which is comparable and even superior to that of the lead acid, Ni/Cd, and Ni/MH batteries.     

镍氢电池的循环性能与活性物质微结构的研究

与循环试验大致同步, 用静态(初态和终态)或准动态(增加若干个中间态)的模式对MH/H电池循环性能、电极(包括负极和正极)材料的微结构进行了X射线衍射(XRD)研究, 发现循环性能衰减与正极材料β-Ni(OH)₂的点阵参数、平均晶粒尺度、微应变和总的层错几率均随循环周期增加而减小以及负极材料中腐蚀产物A(OH)₃和B相出现和增加有一定的对应关系, 发现MH/Ni 电池循环性能的衰减是正极材料和负极材料的结构和微结构随着循环次数的增加发生明显变化, 恶化了正负极材料的电化学性能, 同时消耗和恶化了电解液的综合结果. 为了提高电池的循环性能, 采用不同正极材料的添加剂. 结果表明, CaF₂和Lu₂O₃有明显的效果, 其中CaF₂效果最好, 并有广泛的实用性.     

Some studies on the phase formation and kinetics in TiO<Subscript>2</Subscript> containing lithium aluminum silicate glasses nucleated by P<Subscript>2</Subscript>O<Subscript>5</Subscript>

Lithium aluminum silicate (LAS) glasses of compositions (wt%) 10.6Li₂O–71.7SiO₂–7.1Al₂O₃–4.9K₂O–3.2B₂O₃–1.25P₂O₅–1.25TiO₂ were prepared by the melt quench technique. Crystallization kinetics was investigated by the method of Kissinger and Augis–Bennett using differential thermal analysis (DTA). Based on the DTA data, glass ceramics were prepared by single-, two-, and three-step heat treatment schedules. The interdependence of different phases formed, microstructure, thermal expansion coefficient (TEC) and microhardness (MH) was investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), thermo-mechanical analysis (TMA), and microhardness (MH) measurements. Crystallization kinetics revealed that Li₂SiO₃ is the kinetically favored phase with activation energy of 91.10 kJ/mol. An Avrami exponent of n = 3.33 indicated the dominance of bulk crystallization. Based upon the formation of phases, it was observed that the two-stage heat treatment results in highest TEC glass ceramics. The single-step heat treatment yielded glass ceramics with the highest MH.     

Thermal behavior analysis of nickel/metal hydride battery during overcharging

To analyze the thermal behavior of the cylinder Ni/MH battery during overcharging,a two-dimensional thermal model is provided in this work.More reliable data is provided to create the precise thermal model.The amount of heat of the battery during overcharging at different currents was measured using quartz frequency microcalorimeter.To obtain the heat transfer coefficient of the battery during overcharging,the heat dissipation rate was fitted into linear functions and three different exponential functions f...     

An Illumination‐Assisted Flexible Self‐Powered Energy System Based on a Li–O2 Battery

The flexible Li‐O₂ battery is suitable to satisfy the requirements of a self‐powered energy system, thanks to environmental friendliness, low cost, and high theoretical energy density. Herein, a flexible porous bifunctional electrode with both electrocatalytic and photocatalytic activity was synthesized and introduced as a cathode to assemble a high‐performance Li‐O₂ battery that achieved an overpotential of 0.19 V by charging with the aid of solar energy. As a proof‐of‐concept application, a flexible Li‐O₂ battery was constructed and integrated with a solar cell via a scalable encapsulate method to fabricate a flexible self‐powered energy system with excellent flexibility and mechanical stability. Moreover, by exploring the evolution of the electrode morphology and discharge products (Li₂O₂), the charging process of the Li‐O₂ battery powered by solar energy and solar cell was demonstrated.     

Survey of the phase formation in the Yb2O3Ga2O3MO and Yb2O3Cr2O3MO systems in air at high temperatures (M: Co,Ni, Cu,and Zn)

The phase relations in the Yb₂O₃Ga₂O₃CoO system at 1300 and 1200°C, the Yb₂O₃Ga₂O₃NiO system at 1300 and 1200°C, the Yb₂O₃Ga₂O₃CuO system at 1000°C and the Yb₂O₃Ga₂O₃ZnO system at 1350 and 1200°C, the Yb₂O₃Cr₂O₃CoO system at 1300 and 1200°C, the Yb₂O₃Cr₂O₃NiO system at 1300 and 1200°C, the Yb₂O₃Cr₂O₃CuO system at 1000°C, and the Yb₂O₃Cr₂O₃ZnO system at 1300 and 1200°C were determined in air by means of a classical quenching method. YbGaCoO₄ (a = 3.4165(1) and c = 25.081(2) Å), YbGaCuO₄ (a = 3.4601(4) and c = 24.172(6) Å), and YbGaZnO₄ (a = 3.4153(5) and c = 25.093(7) Å), which are isostructural with YbFe₂O₄ (space group: $\text{R}\text{3}\text{m, a = 3.455(1)}$ and c = 25.109(2) Å, were obtained as stable phases. In the Yb₂O₃Ga₂O₃NiO system and the Yb₂O₃Cr₂O₃MO system (M: Co, Ni, Cu, and Zn), no ternary stable phases existed.     

Sulfur-doped LaNiO3 perovskite oxides with enriched anionic vacancies and manipulated orbital occupancy facilitating oxygen electrode reactions in lithium-oxygen batteries

The rational design of effective bifunctional catalysts with enhanced activity toward oxygen reduction reaction and oxygen evolution reaction is of significance to develop high-performance lithium-oxygen (Li–O₂) batteries. Herein, sulfur-doped LaNiO₃ nanoparticles are elaborately synthesized, and their catalytic activity toward oxygen redox reactions in Li–O₂ batteries is comprehensively studied. As confirmed by the density functional theory calculations and experimental results, the substitution of oxygen atoms by sulfur atoms with lower Pauling electronegativity can enhance the covalent feature of bonds, thus increasing electrical conductivity of catalyst. In addition, abundant oxygen vacancies created after sulfur doping are capable of providing concentrated active sites. Simultaneously, sulfur dopants boost the hybridization between Ni 3d orbital and O 2p orbital and increase the covalency of Ni–O bonds due to the increase of Ni³⁺ with the near-unity occupancy of the e_g orbital, thereby increasing the adsorption strength of oxygen-containing intermediates on the surface. Eventually, lowered reaction energy barriers and accelerated reaction kinetics of oxygen electrode reactions are realized, contributing to the optimized electrochemical performance of Li–O₂ battery. The Li–O₂ battery based on sulfur-doped LaNiO₃ with the optimized S-doping level of 2.89 wt% (marked as S_2.89 wt%-LNO) delivers a high specific discharge capacity of 24067 mAh/g, an ultralow overpotential of 0.37 V and extended life of 347 cycles.     

利用过硫酸钠化学抽取制备脱锂态电极材料

介绍了一种通过常规化学反应制备锂离子电池脱锂态电极材料的方法。首先将氧化剂Na₂S₂O₈与锂离子电池电极材料混合于去离子水中,对混合液进行振荡和搅拌,使脱锂反应充分进行,获得不溶于水的脱锂态电极材料和溶于水的其他生成物,然后将溶于水的生成物过滤掉,最后对不溶于水的脱锂态电极材料进行反复清洗并干燥,便获得所需材料。此方法操作简便,容易控制,计算锂含量方便准确,并且可以得到足够量和纯净的脱锂态电极材料,克服了充放电法制备和采用其他氧化剂进行化学     

Self-discharge behavior of LaNi5-based hydrogen storage electrodes in different electrolytes

Nickel–metal hydride (Ni–MH) batteries using hydrogen storage alloys as negative electrode materials have been developed and commercialized because of their high energy density, high rate capability and long cycle life, without causing environmental pollution (Song et al. J Alloys Comp 298:254, 2000; Jang et al. J Alloys Comp 268:290, 1998). However, the self-discharge rate is relatively higher than that of the Ni–Cd batteries, which would certainly be disadvantageous in practical applications. The capacity loss of a battery during storage is often related to self-discharge in the cells. Self-discharge takes place from a highly charged state of a cell to a lower state of charge (SOC) and is typically caused by the highly oxidizing or reducing characteristic of one or both of the electrodes in the cell. This self-discharge behavior may be affected by various factors such as gases, impurities, temperature, type of alloy electrode, electrolytes, or charge/discharge methods. The loss of capacity can be permanent or recoverable, depending on the nature of the mechanism (chemical or electrochemical) and aging condition. In this paper, the effects of electrolyte composition and temperature on self-discharge behavior of LaNi₅-based hydrogen storage alloy electrodes for Ni–MH batteries have been investigated. It was found that both reversible and irreversible capacity loss of MH electrode tested at 333 K were higher than that at 298 K. When tested at 298 K and 333 K, reversible capacity loss was mainly affected by the electrolyte, while the irreversible capacity loss was not affected. The dissolution of Al from the electrode can be reduced more effectively in an electrolyte with Al addition, compared with that in normal electrolyte. This resulted in a lower reversible capacity loss for the electrode exposed in the Al³⁺-rich electrolyte. SEM analysis has shown that some needle shape and hexagonal corrosion products were formed on the surface of the alloy electrodes, especially after storage at high temperature.     

Magneli phase Ti n O2n − 1 as corrosion-resistant PEM fuel cell catalyst support

Magneli phase titanium suboxide, Ti _n O_{2n ? 1}, with Brunauer–Emmett–Teller surface area up to 25 m² g^?1 was prepared using the heat treatment of titanium oxide (rutile) mixed with polyvinyl alcohol in ratios from 1:3 to 3:1. XRD patterns showed Ti₄O₇ as the major phase formed during the heat treatment process. The Ti _n O_{2n ? 1} showed excellent electrochemical stability in the potential range of ?0.25 to 2.75 V vs. standard hydrogen electrode. The Ti _n O_{2n ? 1} was employed as a polymer electrolyte membrane fuel cell catalyst support to prepare 20 wt% platinum (Pt)/Ti _n O_{2n ? 1} catalyst. A fuel cell membrane electrode assembly was fabricated using the 20 wt% Pt/Ti _n O_{2n ? 1} catalyst, and its performance was evaluated using H₂/O₂ at 80 °C. A current density of 0.125 A?cm^?2 at 0.6 V was obtained at 80 °C.     

Oxygen Evolution in Overcharged LixNi1/3Co1/3Mn1/3O2 Electrode and Its Thermal Analysis Kinetics

The oxygen evolution behavior in overcharged LiNi_1/3Co_1/3Mn_1/3O₂‐based electrode was investigated by differential scanning calorimetry and thermal gravimetric (DSC/TG). Meantime, its thermal kinetic parameters were calculated by Kissinger's and Ozawa's method. As observed by DSC/TG, two exothermic peaks at 239 and 313°C in washed cathode (4.6 V), were attributed to two steps of oxygen evolution. More importantly, the temperature of its oxygen release processes decreased obviously compared with that charged to 2.8 V. Activation energy (E) for the first and second oxygen evolution, both of which were assumed closely to be the first order reaction, between 200 and 350°C in Li_0.204Ni_1/3Co_1/3Mn_1/3O₂‐based electrode were calculated as 113.63 and 158.13 kJ·mol⁻¹, respectively and the corresponding Arrhenius pre‐exponential factors (A) of 1.05×10¹¹ and 6.46×10¹³s⁻¹ were also obtained. The different energy barrier of such two steps of oxygen evolution should probably be ascribed to the different bond energy of M–O (M=Mn, Co, Ni).     

Effect of Lorentz force on the electrochemical performance of lithium-ion batteries

Lorentz force theory demonstrates that electric current density and magnetic force are proportional, indicating that they compensate each other. In a battery operated at high magnetic forces, the electrons in the active material move fast in a specific magnetic field. γ-Fe₂O₃, a highly magnetic material, is used to prepare LiFePO₄ electrodes to study the effect of the Lorentz force on lithium-ion battery performance. The magnetic field created by γ-Fe₂O₃ induces magnetic forces on the charged LiFePO₄ particles, accelerating electron movement. Superconducting quantum interference measurements reveal that saturation magnetization and remanence are prominent when γ-Fe₂O₃ is added to the LiFePO₄ electrodes. The LiFePO₄ electrode containing 15 wt% γ-Fe₂O₃ led to superior battery capacity (69.8 mAh g^− 1 at 10C) compared with the pure LiFePO₄ electrode (1.8 mAh g^− 1 at 10C). In this study, Lorentz force theory is applied to improve the specific capacity and cycle life at high current rates of a battery containing LiFePO₄ cathode materials, suggesting that incorporating γ-Fe₂O₃ into the cathode is an easy and cheap strategy for increasing the power density and cycle life of lithium-ion batteries.     

Experimental study of the heat generations of Li/SOCl2 and Li/SO2 batteries using a phase-change measurement method

A paraffin phase-change measurement method for the heat generation of spirally wound cylindrical Li/SOCl₂ and Li/SO₂ batteries at different ambient temperatures and discharge currents is proposed. The electrical and thermal insulations of the measurement system have been greatly improved, and the accuracy of the measurement system is 4.6 % based on calibration experiments. Compared with accelerated rate calorimetry, isothermal microcalorimetry, and radiation calorimetry methods, the phase-change measurement method is simpler, but with a high accuracy. The experimental results reveal that the heat generation of the batteries during discharge is weakly dependent on the ambient temperature in the range of 38–50 °C, but strongly affected by the discharge current. As the discharge current increases, the heat generated by the Li/SOCl₂ and Li/SO₂ batteries increases as a quadratic polynomial function. The Li/SO₂ battery generates more heat than the Li/SOCl₂ battery at the same discharge current, which is demonstrated by the qualitative analysis of the internal resistance. Furthermore, the phase-change measurement method for heat generation has a strong universality, and can be applicable for heat generation measurement of various battery types.     

Charge‐discharge properties of composites of polypyrrole and vanadium oxide powder

Composite of polypyrrole and crystalline V₂O₅ powder was prepared by chemical oxidation of pyrrole with use of V₂O₅ powder itself as an oxidizing agent. The V₂O₅ content was changed from 0 to 94 wt% by changing the amount of V₂O₅ dispersed in the preparation bath. The pellet electrodes could be prepared by pressing the composite powder alone even if amount of polypyrrole in the composite was only 6 wt%. The resulting pellet electrode exhibited good charge‐discharge performance as a positive electrode of Li rechargeable battery in an electrolyte solution as well as in a quasi‐solid cell fabricated by using a gel electrolyte sheet of poly(methyl methacrylate).     

High effects of smoke suppression and char formation of Ni?Mo/Mg(OH)2 for polypropylene

The Ni? Mo/Mg(OH)₂ (NMM) hybrid as an efficient flame retardancy and smoke suppression composite for polypropylene (PP) was synthesized through Ni? Mo co‐precipitation on the surface of Mg(OH)₂ (MH) hexagonal nanosheets. Compared to PP/MH, PP/NMM exhibited excellent smoke suppressing and flame retardancy on the heat release rate, total heat release, smoke production rate, total smoke production, CO production rate and total CO production with the same loading. The reduced hazard of PP/NMM was mainly attributed to the high physical barrier effect of compact char residues on heat, smoke and combustible gas. The mechanism study indicated that multiwalled carbon nanotubes (MWCNTs) generated from the catalytic carbonization of PP by the Ni? Mo compound could play the role of “rebar” to strengthen the char residues, avoid the generation of cracks and form highly compact char layer. Furthermore, MgO could facilitate the production of MWCNTs through changing the pyrolysis process of PP and increasing the reaction time between pyrolysis gas and Ni? Mo compound. Hence, the new Ni? Mo/MH catalyst hybrid may explore the potential for solving the tough problem of the flammability and heavy smoke of the polyolefins system.     

One‐Step Pyro‐Synthesis of a Nanostructured Mn3O4/C Electrode with Long Cycle Stability for Rechargeable Lithium‐Ion Batteries

A nanostructured Mn₃O₄/C electrode was prepared by a one‐step polyol‐assisted pyro‐synthesis without any post‐heat treatments. The as‐prepared Mn₃O₄/C revealed nanostructured morphology comprised of secondary aggregates formed from carbon‐coated primary particles of average diameters ranging between 20 and 40 nm, as evidenced from the electron microscopy studies. The N₂ adsorption studies reveal a hierarchical porous feature in the nanostructured electrode. The nanostructured morphology appears to be related to the present rapid combustion strategy. The nanostructured porous Mn₃O₄/C electrode demonstrated impressive electrode properties with reversible capacities of 666 mAh g^?1 at a current density of 33 mA g^?1, good capacity retentions (1141 mAh g^?1 with 100 % Coulombic efficiencies at the 100^th cycle), and rate capabilities (307 and 202 mAh g^?1 at 528 and 1056 mA g^?1, respectively) when tested as an anode for lithium‐ion battery applications.     

The standard free energy of formation of YbFe2O4, Yb2Fe3O7, YbFeO3, and Yb3Fe5O12 at 1200°C

The standard free energy of formation of YbFe₂O₄, Yb₂Fe₃O₇, YbFeO₃, and Yb₃Fe₅O₁₂ from metallic iron, Yb₂O₃, and oxygen was determined to be ?100.38, ?158.38, ?58.17, and ?283.40 kcal/mole, respectively, at 1200°C on the basis of the phase equilibria in the FeFe₂O₃Yb₂O₃ system. The FeFe₂O₃-Lanthanoid sesquioxide systems were classified into four types with respect to the assemblage of the ternary compounds in stable existence at 1200°C, and the standard free energy of formation of YbFeO₃ was compared with those of the other lanthanoid-iron perovskites.