圆柱形锂离子电池模组微通道液冷热模型

针对电动汽车电堆的热管理系统,建立了包含71节18650型锂离子电池的电池模组的微通道液冷热模型。该模型集总处理单电池热过程、电池生热基于实测结果,模型还特别考虑了电池间导热。基于该模型,模拟研究了放电倍率、冷却液入口流速、电池间接触面积以及电池与水冷管外壁接触面积对电池模组热行为的影响。模拟结果证实了该微通道液冷方案对动力电池模组热管理的有效性,并且发现：放电倍率的增加会使电池模组内单电池温度增加、模组内温度一致性变差;增大冷却液流量可以显著降低电池模组的温度,并改善其温度一致性;增大电池间接触面积可略微提升电池模组温度一致性,但对控制其最高温度作用有限;增大电池与液冷管外壁接触面积可显著降低电池模组内电池的最高温度,但会使其温度一致性变差。     

Electrochemical model of a lithium-ion battery implemented into an automotive battery management system

This paper presents the development of an electrochemical model that can be implemented into automotive battery management systems (BMSs). Compared with empirical models, the electrochemical model features more accurate state estimates over a broader and longer use of the battery. In this work, model implementation schemes are devised to make the electrochemical model uncomplicated enough to be embedded into the BMS. A nonlinear system of partial differential equations in the model is discretized into a linearized system of algebraic equations (AEs). A solver selected to evaluate the resulting system of AEs is modified for its application to the BMS. As the BMS is preoccupied by its existing tasks, the reformulated equations and optimized solver are reorganized such that the limited computational resources of the BMS are appropriately exploited. The electrochemical model is consequently implemented into the BMS, predicting battery behaviors in 1 s intervals while occupying a 14 kB RAM.     

基于热管技术的锂离子动力电池散热系统

基于对大功率锂离子动力电池温升和温度场分布的研究,设计了一种基于热管技术的锂离子动力电池散热模块。实验结果表明,采用所设计的散热模块能够有效降低电池壁面温度,使其壁面最高温度低于40℃,与无热管理条件相比降幅高达10℃,满足锂离子动力电池最佳工作温度范围。对散热模块与纯热管的散热性能进行对比,发现散热模块比单纯使用热管的散热效果和均温效果更好。此外,采用有限元模拟软件Fluent分析复合风冷翅片和U型热管模块蒸发段几何尺寸对散热模块性能的影响,发现复合风冷翅片能够有效提高模块散热性能以及不同的蒸发段几何分布会影响电池壁面温度和温度场分布。当U型热管蒸发段的垂直段和水平段长度比为1时,散热模块散热性能最好。     

基于相变材料的锂离子电池热管理性能

锂离子电池（lithium-ion battery,LIB）作为目前应用最广泛的储能电池之一,在电动汽车等行业发挥着至关重要的作用。电池的温度是影响LIB性能及安全性的重要因素,因此电池热管理（battery thermal management,BTM）至关重要。目前,利用相变材料（phase change material,PCM）进行相变冷却的热管理方式因其潜热高、不需消耗额外能量的优点已成为一种很有前途的方法。本文针对8节并联18650LIB的电池组性能进行了数值模拟及实验研究,探究了石蜡基复合相变材料（composite phase change material,CPCM）物性参数（包括热导率、熔点、相变潜热和材料厚度）对本文设计的电池组热管理性能的影响。结果表明,纯石蜡用于BTM可将3C放电下的电池最高温度降低28.0%,向石蜡中添加膨胀石墨后可使CPCM的热管理性能进一步提升,CPCM的热导率为2.0W/(m·K)时可将3C放电下的电池最高温度进一步降低5.42℃,继续增大CPCM热导率对热管理性能的提升较小。在综合考虑电池组的最高温度和温度均匀性的情况下,为得到在本文所设计的锂离子电池组最佳热管理性能,CPCM的热导率为2.0W/(m·K)、熔点应在36~38℃之间、相变潜热在212J/g左右、CPCM的厚度为4mm时最优。     

Preparation of porous-structured LiFePO4/C composite by vacuum sintering for lithium-ion battery

The LiFePO₄/C (LFP/C) composite as a cathode material for lithium-ion battery was synthesized by solid-state reaction under vacuum sintering condition (20–5 Pa). The effects of vacuum sintering temperature and time on the phase composition, morphological structure, and electrochemical performance of LFP/C composite were investigated by X-ray diffraction, scanning electron microscopy, galvanostatic charge–discharge cycling test, and electrochemical impedance spectroscopy. The synthetic LFP/C composite possessed uniform particle-size distribution with porous architecture upon sintering at 650 °C for 12 h and thus exhibited the highest discharge capacity and best cycle performance. The complete decomposition of citric acid at a suitable temperature under vacuum condition resulted in the formation of porous structure. Compared with atmospheric argon sintering, vacuum sintering method led to the formation of porous architecture, the porous sample showed excellent cycle performance with less than 2% capacity loss after 80 cycles at 0.2 C, and reached the discharge specific capacity of 87.6 mAh g⁻¹ at 10 C rate, these are better than that of atmospheric argon sintering. The LFP/C composite prepared under vacuum sintering also reduced the optimum sintering temperature by nearly 100 °C compared with that prepared under atmospheric argon sintering.     

锂离子电池电解质六氟磷酸锂市场分析

通过对未来5 a锂离子电池在动力电池、储能电池、数码电池市场的发展情况分析,预测锂离子电池生产的平均增长率将达到26%以上,到2025年对应锂离子电池电解液的需求量和六氟磷酸锂需求量将分别达到93.0万t和10.3万t。分析目前六氟磷酸锂产能情况和后期各生产企业扩产计划,预测六氟磷酸锂产能在2022年以前满足市场需求;若2025年以前各生产企业扩产到位,供需将会达到平衡,并且六氟磷酸锂价格趋于平稳,在原材料价格波动不大的情况下预计其价格在8.5万元/t左右。     

Current oscillations in anodic electrodissolution of copper in lithium-ion battery electrolyte

Current oscillations were observed during electrodissolution of copper in nonaqueous lithium-ion battery electrolyte under potentiostatic conditions using copper foil electrodes. Mixed-mode oscillations were observed over certain ranges of stir rate and applied potential. A nonlinear dynamics technique (return map) was applied to characterize the oscillations. The dynamic stir conditions of the electrolyte influenced the frequency and pattern of the oscillations. The amplitude of the oscillations increased with increasing potential. Also, cyclic voltammetry (CV) showed that the oscillatory current was correlated to the oxidation of the copper electrode.     

Facile synthesis of hierarchical nanostructured rutile titania for lithium-ion battery

A facile hydrothermal method is developed to prepare rutile titania sub-microflowers consisting of nanorods with oxalic acid and TiOSO₄ as reagents. The diameter of sub-microflowers and nanorods is found to be ca. 800 and 40 nm, respectively. Also, the shape and size of building blocks in rutile titania sub-microflowers can be considerably controlled via adjusting the reaction time and reactant amounts. Rutile titania sub-microflowers composed of nanorods display higher discharge capacity and better rate cycle stability than other rutile titania nanostructures as lithium-ion battery anode material due to enhancing the Li-ion transfer rate for small size building blocks.     

Single wall carbon nanotube paper as anode for lithium-ion battery

“Free-standing” single wall carbon nanotube (SWNT) papers have been synthesised by simple filtration method via positive pressure. A conventional SWNT slurry coated electrode was fabricated to compare with the SWNT papers. The results show that the capacity of the “Free-standing” electrode was slightly lower than that of the conventional electrode, but the “Free-standing” electrode was produced without any binder, and metal substrate, so that the weight of electrode was reduced significantly. On the other hand, the procedures for SWNT electrode preparation were simplified, so the cost of the manufacturing could be reduced.     

Electrochemical studies of LiB compound as anode material for lithium-ion battery

Electrochemical studies of LiB compound were carried out for its application as anode for lithium-ion battery. The compound exhibited a reversible discharge-charge behavior between 0 and 0.75 V versus Li/Li⁺ with a first discharge capacity of 293 mA h g⁻¹. Discharging to 1.0 V, the first discharge capacity of LiB compound was 660 mA h g⁻¹, but a part of this capacity was irreversible. Impedance spectra were measured at several potentials corresponding to different discharge plateaus. The impedance spectra obtained below and above 0.8 V presented significantly different features. The solid electrolyte interphase layer (SEI) was formed below 0.8 V and assumed a good performance of LiB electrode in this potential range. The SEI was found to deteriorate above 0.8 V, which might be associated with the irreversible discharge capacity.     

锂离子电池负极材料中国专利分析

通过对中国发明专利数据进行挖掘和计量分析,总结了锂离子电池负极材料的专利申请情况、行业发展现状、地域分布及重点创新主体的专利技术布局。结果表明,锂离子电池负极材料经过几年的持续增长后,专利申请趋势放缓。通过对专利进行地域分析,了解到中国本土申请人和日本申请人申请了大量的专利;国内申请人主要集中在广东、上海、北京及浙江。通过分析一些重点企业申请的专利技术布局可以了解目前市场上的负极材料技术热点。     

MnO2 prepared by hydrothermal method and electrochemical performance as anode for lithium-ion battery

Two α-MnO₂ crystals with caddice-clew-like and urchin-like morphologies are prepared by the hydrothermal method, and their structure and electrochemical performance are characterized by scanning electron microscope (SEM), X-ray diffraction (XRD), galvanostatic cell cycling, cyclic voltammetry, and electrochemical impedance spectroscopy (EIS). The morphology of the MnO₂ prepared under acidic condition is urchin-like, while the one prepared under neutral condition is caddice-clew-like. The identical crystalline phase of MnO₂ crystals is essential to evaluate the relationship between electrochemical performances and morphologies for lithium-ion battery application. In this study, urchin-like α-MnO₂ crystals with compact structure have better electrochemical performance due to the higher specific capacity and lower impedance. We find that the relationship between electrochemical performance and morphology is different when MnO₂ material used as electrochemical supercapacitor or as anode of lithium-ion battery. For lithium-ion battery application, urchin-like MnO₂ material has better electrochemical performance.     

Supercritical carbon dioxide extraction of lithium-ion battery electrolytes

Two different separator materials (polyethylene fleece – Freudenberg 2190 and porous glass fiber – Whatman^® GF/D) and two different lithium-ion battery electrolytes have been investigated regarding their behavior in an autoclave extraction with supercritical helium head pressure carbon dioxide (sc HHPCO₂). Mixtures of dimethyl carbonate (DMC)/ethylene carbonate (EC) and ethylmethyl carbonate (EMC)/EC, each with 1 mol/L LiPF₆ were used.In addition to these proof of principle experiments, the developed extraction method was further applied to real battery samples. Commercial 18650 cells (after formation and aging) were opened and the jelly roll was extracted with sc HHPCO₂. Extracts were analyzed with gas and ion chromatography (GC, IC). Recovery rates and extract compositions strongly depend on the material of which the electrolyte is extracted. Further structure determination of electrolyte aging products was performed with different ionization modes in GC–mass spectrometry (GC–MS) experiments. Diethyl carbonate (DEC), dimethyl-2,5-dioxahexane dicarboxylate (DMDOHC), ethylmethyl-2,5-dioxahexane dicarboxylate (EMDOHC) and diethyl-2,5-dioxahexane dicarboxylate (DEDOHC) are aging products of electrolyte degradation which were successfully extracted and identified. Their concentrations correlate with solid electrolyte interphase (SEI) growth on the negative electrode which was investigated with scanning electron microscopy (SEM).     

Decorating ZnO nanoflakes on carbon cloth: Free-standing,highly stable lithium-ion battery anodes

A facile chemical bath deposition method to grow 10-nm-thick ZnO nanoflakes (NFs) on carbon cloth (CC) was developed; further, free-standing, flexible lithium-ion -battery (LIB) anodes with good electrical contact between current collector and the active substance were prepared. The as-prepared ZnO NFs/CC-based LIB anodes showed a high specific capacity of 1754 mAh g⁻¹ at a current density of 0.1 A g⁻¹, a capacity retention of almost 52.9% at a current density of 2 A g⁻¹, as well as high rate capability. Moreover, the anodes demonstrated a high capacity with reversiblity of approximately 1650 mAh g⁻¹ and only 6% capacity fading at a current density of 0.1 A g⁻¹, even after 100 cycles. These results imply that the synthesized, unique ZnO NFs/CC nanostructures can be employed as high-efficiency anode materials for flexible LIBs.     

Synthesis and electrochemical performance of Li4Ti5O12 submicrospheres coated with TiN as anode materials for lithium-ion battery

The TiN coated Li₄Ti₅O₁₂ (LTO) submicrospheres with high electrochemical performance as anode materials for lithium-ion battery were synthesized successfully by solvothermal method and subsequent nitridation process in the presence of ammonia. The XRD results revealed that the crystal structure of LTO did not change after thermal nitridation process. The submicrospheres morphology of LTO and TiN film on the surface of LTO submicrospheres were characterized by FESEM and HRTEM, respectively. XPS result confirmed that a small amount of Ti changed from Ti⁴⁺ to Ti³⁺ after nitridation process, which will increase the electronic conductivity of LTO. Electrochemical results showed that electrochemical performance of TiN coated LTO anode materials compared favorably with that of pure LTO. Also its rate capability and cycling performance were apparently superior to those of pure LTO. The reversible capacity of TiN-LTO is 105.2 mA h g⁻¹ at a current density of 10 C after 100 cycles and maintain 92.9% of its initial discharge capacity, while that of pure LTO is only 83.6 mA h g⁻¹ with a capacity retention of 90.3%. Even at 20 C, the discharge capacity of TiN coated LTO sample is 101.3 mA h g⁻¹, compared with 77.3 mA h g⁻¹ for pristine LTO in the potential range 1.0–2.5 V (vs. Li/Li⁺).     

Vanadium trioxide nanowire arrays as a cathode material for lithium-ion battery

This paper reports a study on the electrochemical performance of vanadium trioxide (V₂O₃) nanowire arrays as a cathode material for Li-ion battery. V₂O₃ nanowire arrays are formed via thermal treatment of ammonium vanadium bronze (NH₄V₄O₁₀) nanowires in a 5% H₂ and 95% Ar atmosphere. X-ray diffraction confirms the thermal reduction. The V₂O₃ nanowire arrays as an electrode of lithium-ion battery exhibit high reversible capacity and excellent long-term cycling stability. The discharge capacity increases from 243 to 428?mA?h?g^?1 at the first 20 cycles. After 100 cycles, a stable capacity of 444?mA?h?g^?1 is retained at a current density of 30?mA?g^?1.     

A peapod-like ZnO@C design with internal void space to relieve its large-volume-change as lithium-ion battery anode

Peapod-like ZnO@C with internal void space has been synthesized by calcination of ZnO/ZnOHF@polydopamine nanorods. By designing both the large void space between particles and external elastic carbon shell, the large volume change of ZnO during charge-discharge process could be effectively relieved. Moreover, the carbon shell functioned as an electronic conductor and elastic barrier, could accelerate the reaction kinetics and confine stable SEI films formation on the outer protective layer to further improve the structural integrity. Benefiting from these structure advantages, the peapod-like ZnO@C presents a prominent electrochemical performance with a retained discharge capacity of 565.1 mA h g^?1 at 0.2 A g^?1 and high rate capacity of 246.6 mA h g^?1 even at 4 A g^?1.     

A novel approach to explore Zn based anodes for lithium-ion battery applications

As an approach to investigate upon the electrochemical property of Zn as a possible lithium battery anode material, an ever first attempt to explore two types of Zn based alloy anodes, viz., Zn_0.9Ni_0.075In_0.025 (nickel rich) and Zn_0.9Ni_0.025In_0.075 (indium rich) was made. Citric acid assisted modified sol-gel method [CAM sol-gel] has been adopted to synthesize the anode materials at 500 °C and characterized further by XRD and SEM for phase purity and preferred surface morphology, respectively. An average crystallite size of 800 nm-1.2 μm has been calculated from the PXRD pattern and the compounds were found to exist in the cubic phase. A discharge capacity of 936 and 1155 mAh/g were exhibited by Zn_0.9Ni_0.075In_0.025 and Zn_0.9Ni_0.025In_0.075 anodes respectively, with an excellent capacity retention (>85%) and enhanced coulombic efficiency (95-98%). It is further understood that the Zn_0.9Ni_0.025In_0.075 anode with increased In content has exhibited promising electrochemical property with a steady state reversible capacity of ∼490 mAh/g even after 25 cycles, compared to the corresponding nickel rich counterpart, viz., Zn_0.9Ni_0.075In_0.025.     

Multi-functional Al2O3-coated separators for high-performance lithium-ion batteries: Critical effects of particle shape

The technology of coating polyolefin-type separators with ceramics is gradually developing as an effective method to improve the safety of lithium-ion batteries (LIBs). However, the powder properties of ceramics can adversely affect the surface structure and ionic conductivity of separators; therefore, a new approach is required regarding the powder properties that affect the performance of the separator. Herein, the effect of the Al₂O₃ particle shape on the physical properties of Al₂O₃-coated separators and the performance of LIBs is investigated. In the separator coated with angular-shaped Al₂O₃ particles (Al₂O₃-A), the pores in the coating layer are uniformly distributed, improving physical properties such as porosity and wettability. The thermal shrinkage of separator is <10% when exposed to 150 °C for 1 h, considerably smaller than that of the commercial polyethylene separator (approximately 83%) under the same conditions. Moreover, the Al₂O₃-A-coated separator shows the highest ionic conductivity (0.531 mS cm⁻¹), and the LiNi_0.8Mn_0.1Co_0.1O₂/Al₂O₃-A-coated separator/Li battery displays improved stability than using the polyethylene separator under a current density of 5C. This proposes approach to improve the separator's performance through the shape control of ceramic particles paves the way for separators to contribute to the high-temperature safety and long cycle life of batteries.     

High rate capability of carbonaceous composites as anode electrodes for lithium-ion secondary battery

Anode materials with high rate capability for Li-ion secondary batteries were investigated by using the mixture of graphite, cokes, and petroleum pitch. Since obvious potential plateaus were obtained at graphite contents above 40 wt.%, which would cause difficulties in perceiving the capacity variations as a function of electrical potential, the graphite content were determined at 20–30 wt.%. The composites with a given content of graphite and remaining content of petroleum pitch/cokes mixtures at 1:4, 1:1, and 4:1 mass ratios were heated at a temperature range of 800–1200 °C. For a given composition of carbonaceous composite, the discharge rate capability improved but the reversible capacity decreased with increasing the heat treatment temperature. Although the reversible capacity increased with increasing content of the petroleum pitch for given graphite content and heat treatment temperature, the discharge rate capability decreased. The carbonaceous composites prepared by the mixture of 30 wt.% graphite and 70 wt.% petroleum pitch/cokes mixture at 1:4 mass ratio with the heat treatment at 800 °C showed relatively high electrochemical properties, of which reversible capacity, initial efficiency, discharge rate capability (retention of discharge capacity in 5 C/0.2 C) and charge capacity at 5 C were 312 mAh/g, 79%, 89% and 78 mAh/g, respectively.