基于WOA-UKF算法的锂电池容量与SOC联合估计

锂电池的荷电状态(SOC)和有效容量是表征电池当前剩余电量和电池寿命的重要参数,提出一种锂离子电池有效容量和SOC的联合估计方法。在电池全寿命周期内,给出一种开路电压与SOC和电池有效容量非线性模型的两变量多项式描述;当电池循环使用次数超过预设值,采用鲸鱼优化算法估计当前电池容量与电池模型参数,根据模型参数与容量值采用无迹卡尔曼滤波器估计电池SOC;在SOC估计过程中,采用鲸鱼优化算法更新无迹卡尔曼滤波器的观测噪声方差和过程噪声方差,实现噪声方差的自适应调节,进而提高估计精度。实验结果验证了该方法的有效性和联合估计方案的可行性。     

高精度预测SOC的混合电动车电池管理系统的研究

研制了新型的电动汽车蓄电池组管理系统,该系统在提高采集监测电流、电压、温度等信号精度的基础上,采用了放电率、温度、自放电及容量老化等补偿的安时积分模型的估计,并考虑了自调整,从而可以以较高的精度预测电动汽车的电池荷电状态(SOC).     

混合动力汽车电池管理系统的研究

研制了用于混合动力汽车的镍氢动力电池管理系统。该系统采用分布式测量方案,具有安装简单、抗干扰能力强等优点;剩余电量的估算结合了库仑计法和开路电压法,具有较高的精度;采用了电池均衡充电方法,对电池的不一致性进行了补偿,从而延长了电池组的使用寿命。     

Co-Estimation of State of Charge and Capacity for Lithium-Ion Batteries with Multi-Stage Model Fusion Method

Lithium-ion batteries (LIBs) have emerged as the preferred energy storage systems for various types of electric transports, including electric vehicles, electric boats, electric trains, and electric airplanes. The energy management of LIBs in electric transports for all-climate and long-life operation requires the accurate estimation of state of charge (SOC) and capacity in real-time. This study proposes a multi-stage model fusion algorithm to co-estimate SOC and capacity. Firstly, based on the assumption of a normal distribution, the mean and variance of the residual error from the model at different ageing levels are used to calculate the weight for the establishment of a fusion model with stable parameters. Secondly, a differential error gain with forward-looking ability is introduced into a proportional–integral observer (PIO) to accelerate convergence speed. Thirdly, a fusion algorithm is developed by combining a multi-stage model and proportional–integral–differential observer (PIDO) to co-estimate SOC and capacity under a complex application environment. Fourthly, the convergence and anti-noise performance of the fusion algorithm are discussed. Finally, the hardware-in-the-loop platform is set up to verify the performance of the fusion algorithm. The validation results of different aged LIBs over a wide range of temperature show that the presented fusion algorithm can realize a high-accuracy estimation of SOC and capacity with the relative errors within 2% and 3.3%, respectively.     

Residual Capacity Estimation for Lead–Acid Batteries Used in Automobiles by the Method of Median Internal Resistance

The purpose of this study was to investigate the method of residual capacity estimation for lead–acid batteries used in automobiles. First, relation charts for the internal resistances of a battery at various load currents to residual capacity percentages were established, and the relation charts for all load currents were then combined to obtain the corresponding residual capacity by calculating medians. The experimental equipment included lead–acid batteries for automobiles, an electronic loader, an internal resistance tester, and test cables. The experimental procedures were discharging the battery with the electronic loader, using the internal resistance tester to record the internal resistance, voltage, and temperature of the battery, and then transmitting the data to a computer via the test cables for analysis. The experiment obtained nine sets of data, which were recorded in Excel and illustrated using charts. The medians obtained from combining the internal resistance with the residual capacity percentages were used to generate the relation charts for the internal resistances at various load currents to the residual capacity percentages. Finally, 60 Ah was used as the normal capacity to estimate the residual capacity discharging time. Furthermore, a curve-fitting approach for determining the relation equation between internal resistances and capacities was used to replace the table look-up method for residual capacity estimation. The results revealed that the estimation errors after correction were acceptable.     

3Ah高镍/硅氧碳软包电池循环容量衰减分析EI北大核心CSCD

随着电动汽车的发展,对电池能量密度提出了更高的要求,具有高能量密度的高镍/硅氧碳软包电池成为长续航电动汽车的首选,但是高镍/硅氧碳电池在实际使用中存在容量快速衰减的问题。采用无损电化学分析和事后拆解分析对循环过程中电池容量和内阻的变化进行检测,通过对比电池循环前后正负极结构、材料形貌和表面成分的变化,揭示高镍/硅氧碳电池循环失效机制。结果表明:电池容量衰减呈现平稳期、快速衰减期和急速衰减期3个阶段。循环后电池极化更加严重,电池极化内阻、负极表面膜阻抗和电荷转移阻抗明显增加。通过微分曲线分析结合拆解分析发现,高镍正极材料衰减较少,硅氧碳负极材料衰减和活性锂离子损失较多。硅氧颗粒膨胀开裂,负极活性物质损失,负极表面膜连续生长消耗过多的活性锂为电池容量快速衰减的主要原因。     

基于改进型能量守恒SOC估算法的电动汽车三段式智能充电方式研究

为研究电动汽车安全、快速的智能充电方式,基于传统能量守恒法,考虑电池容量衰减和电池内阻损失对荷电状态(state of charge,SOC)估算的影响,提出改进型能量守恒SOC估算方法。对比分析几种传统充电方式,根据马斯定理确定最佳充电电流,提出以改进型能量守恒SOC估算法得到的SOC值作为判断依据的电动汽车三段式(小电流充电、脉冲充电、恒压充电)智能充电方式,并建立其仿真模型。结果表明:改进型能量守恒SOC估算法得到的SOC值要小于传统能量守恒法,其更加接近真实SOC值;三段式智能充电方式能根据电池组SOC值的变化智能地选择具体充电方式,实现了对电池的安全、快速充电。提出的基于改进型能量守恒SOC估算的三段式智能充电方式对当前电动汽车充电方式的研究提供了一定的参考价值,为智能充电方式研究效能的提升提供了一种可行方法,也为智能充电理论应用于工程实践打下基础。     

High‐Capacity Cathode Material with High Voltage for Li‐Ion Batteries

Electrochemical energy storage devices with a high energy density are an important technology in modern society, especially for electric vehicles. The most effective approach to improve the energy density of batteries is to search for high‐capacity electrode materials. According to the concept of energy quality, a high‐voltage battery delivers a highly useful energy, thus providing a new insight to improve energy density. Based on this concept, a novel and successful strategy to increase the energy density and energy quality by increasing the discharge voltage of cathode materials and preserving high capacity is proposed. The proposal is realized in high‐capacity Li‐rich cathode materials. The average discharge voltage is increased from 3.5 to 3.8 V by increasing the nickel content and applying a simple after‐treatment, and the specific energy is improved from 912 to 1033 Wh kg^?1. The current work provides an insightful universal principle for developing, designing, and screening electrode materials for high energy density and energy quality.     

High‐Performance Integrated Self‐Package Flexible Li–O2 Battery Based on Stable Composite Anode and Flexible Gas Diffusion Layer

With the rising development of flexible and wearable electronics, corresponding flexible energy storage devices with high energy density are required to provide a sustainable energy supply. Theoretically, rechargeable flexible Li–O₂ batteries can provide high specific energy density; however, there are only a few reports on the construction of flexible Li–O₂ batteries. Conventional flexible Li–O₂ batteries possess a loose battery structure, which prevents flexibility and stability. The low mechanical strength of the gas diffusion layer and anode also lead to a flexible Li–O₂ battery with poor mechanical properties. All these attributes limit their practical applications. Herein, the authors develop an integrated flexible Li–O₂ battery based on a high‐fatigue‐resistance anode and a novel flexible stretchable gas diffusion layer. Owing to the synergistic effect of the stable electrocatalytic activity and hierarchical 3D interconnected network structure of the free‐standing cathode, the obtained flexible Li–O₂ batteries exhibit superior electrochemical performance, including a high specific capacity, an excellent rate capability, and exceptional cycle stability. Furthermore, benefitting from the above advantages, the as‐fabricated flexible batteries can realize excellent mechanical and electrochemical stability. Even after a thousand cycles of the bending process, the flexible Li–O₂ battery can still possess a stable open‐circuit voltage, a high specific capacity, and a durable cycle performance.     

Atomic Fe–Nx Coupled Open‐Mesoporous Carbon Nanofibers for Efficient and Bioadaptable Oxygen Electrode in Mg–Air Batteries

The recently emerging metal–air batteries equipped with advanced oxygen electrodes have provided enormous opportunities to develop the next generation of wearable and bio‐adaptable power sources. Theoretically, neutral electrolyte‐based Mg–air batteries possess potential advantages in electronics and biomedical applications over the other metal–air counterparts, especially the alkaline‐based Zn–air batteries. However, the rational design of advanced oxygen electrode for Mg–air batteries with high discharge voltage and capacity under neutral conditions still remains a major challenge. Inspired by fibrous string structures of bufo‐spawn, it is reported here that the scalable synthesis of atomic Fe–N_x coupled open‐mesoporous N‐doped‐carbon nanofibers (OM‐NCNF‐FeN_x) as advanced oxygen electrode for Mg–air batteries. The fabricated OM‐NCNF‐FeN_x electrodes present manifold advantages, including open‐mesoporous and interconnected structures, 3D hierarchically porous networks, good bio‐adaptability, homogeneously coupled atomic Fe–N_x sites, and high oxygen electrocatalytic performances. Most importantly, the assembled Mg–air batteries with neutral electrolytes reveal high open‐circuit voltage, stable discharge voltage plateaus, high capacity, long operating life, and good flexibility. Overall, the discovery on fabricating atomic OM‐NCNF‐FeN_x electrode will not only create new pathways for achieving flexible, wearable, and bio‐adaptable power sources, but also take a step towards the scale‐up production of advanced nanofibrous carbon electrodes for a broad range of applications.     

Charge equalization circuit for discharging series‐connected batteries with regulated output

Abstract

Charge equalization during the charging process has been extensively discussed for series‐connected batteries. However, charge inequality may also happen to batteries during discharging. The imbalance among batteries may result in over‐discharging and consequently damage to the batteries. To solve the problem, a balanced discharging method for a series‐connected battery bank is proposed. A flyback conversion circuit is designed with a pulse‐width‐modulation controller to achieve output voltage regulation as well as balanced discharging. The applicability of the proposed method is confirmed by experiments.     

基于改进Thevenin模型的混合动力镍氢电池SOC估算研究

基于混合动力汽车用NiMH电池实验数据,对Thevenin电池等效电路模型进行了改进,分充放电两个不同的方向来辨识模型参数,在Matlab/Simulink中建立电池模型,并基于此模型,研究了卡尔曼滤波法在估算电池荷电状态(SOC)中的应用.仿真结果与电池实验数据的对比表明,改进后的模型能更真实地模拟电池特性,所研究的方法能有效解决SOC 初值估算不准和累积误差的问题.     

Potassium‐Based Dual Ion Battery with Dual‐Graphite Electrode

A potassium ion battery has potential applications for large scale electric energy storage systems due to the abundance and low cost of potassium resources. Dual graphite batteries, with graphite as both anode and cathode, eliminate the use of transition metal compounds and greatly lower the overall cost. Herein, combining the merits of the potassium ion battery and dual graphite battery, a potassium‐based dual ion battery with dual‐graphite electrode is developed. It delivers a reversible capacity of 62 mA h g^?1 and medium discharge voltage of ≈3.96 V. The intercalation/deintercalation mechanism of K⁺ and PF₆^? into/from graphite is proposed and discussed in detail, with various characterizations to support.     

Polarity‐Switchable Symmetric Graphite Batteries with High Energy and High Power Densities

Multifunctional batteries with enhanced safety performance have received considerable attention for their applications at extreme conditions. However, few batteries can endure a mix‐up of battery polarity during charging, a common wrong operation of rechargeable batteries. Herein, a polarity‐switchable battery based on the switchable intercalation feature of graphite is demonstrated. The unique redox‐amphoteric intercalation behavior of graphite allows a reversible switching of graphite between anode and cathode, thus enabling polarity‐switchable symmetric graphite batteries. The large potential gap between anion and cation intercalation delivers a high midpoint device voltage (≈average voltage) of ≈4.5 V. Further, both the graphite anode and cathode are kinetically activated during the polarity switching. Consequently, polarity‐switchable symmetric graphite batteries exhibit a remarkable cycling stability (96% capacity retention after 500 cycles), a high power density of 8.66 kW kg^?1, and a high energy density of 227 Wh kg^?1 (calculated based on the total weight of active materials in both anode and cathode), which are superior to other symmetric batteries and recently reported dual‐graphite or dual‐carbon batteries. This work will inspire the development of new multifunctional energy‐storage devices based on novel materials and electrolyte systems.     

A novel approach for electrical circuit modeling of Li-ion battery for predicting the steady-state and dynamic I–V characteristics

A novel approach for electrical circuit modeling of Li-ion battery is proposed in this paper. The model proposed in this paper is simple, fast, not memory intensive and does not involve any look-up table. The model mimics the steady-state and dynamic behavior of battery. Internal charge distribution of the battery is modeled using two RC circuits. Self-discharge characteristic of the battery is modeled using a leakage resistance. Experimental procedure to determine the internal resistance, leakage resistance and the value of RC elements is explained in detail. The variation of parameters with state of charge (SOC) and magnitude of current is presented. The internal voltage source of the battery model varies dynamically with SOC to replicate the experimental terminal voltage characteristics of battery. The accuracy of model is validated with experimental results.     

基于放电过程信息的锂电池剩余寿命预测

容量或内阻是衡量锂离子电池健康状态的重要指标,但在锂电池实际运行中,其容量和内阻很难实时获取。为此,提出了基于放电过程信息获取新健康指标的方法,并对锂电池的剩余寿命进行预测。主要研究了锂电池放电过程中电压变化的规律,提出两种可在线测量的新健康指标,并通过Box-Cox变换修正了新健康指标的准确性。比较分析表明,所提取的健康指标与容量之间存在着强相关性,在某种程度上可以解决锂电池容量难以在线测量的问题。此外还基于新健康指标建立了锂电池退化过程模型,并利用相关向量机算法进行锂电池的剩余寿命预测。实验结果表明,在寿命预测性能上相关向量机算法优于其他算法,并且预测时间越晚,预测结果就越准确,所提取的健康指标也能够很好地描述锂电池的退化过程,并在剩余寿命预测结果上表现优越。     

Bottom-Up Design of a Green and Transient Zinc-Ion Battery with Ultralong Lifespan

Transient batteries are expected to lessen the inherent environmental impact of traditional batteries that rely on toxic and critical raw materials. This work presents the bottom-up design of a fully transient Zn-ion battery (ZIB) made of nontoxic and earth-abundant elements, including a novel hydrogel electrolyte prepared by cross-linking agarose and carboxymethyl cellulose. Facilitated by a high ionic conductivity and a high positive zinc-ion species transference number, the optimized hydrogel electrolyte enables stable cycling of the Zn anode with a lifespan extending over 8500 h for 0.25 mA cm⁻² – 0.25 mAh cm⁻². On pairing with a biocompatible organic polydopamine-based cathode, the full cell ZIB delivers a capacity of 196 mAh g⁻¹ after 1000 cycles at a current density of 0.5 A g⁻¹ and a capacity of 110 mAh g⁻¹ after 10 000 cycles at a current density of 1 A g⁻¹. A transient ZIB with a biodegradable agarose casing displays an open circuit voltage of 1.123 V and provides a specific capacity of 157 mAh g⁻¹ after 200 cycles at a current density of 50 mA g⁻¹. After completing its service life, the battery can disintegrate under composting conditions.     

安时-卡尔曼交叉运行的电池荷电状态估算策略及其微控制器在环验证

为了提高电池管理系统(BMS)的性能,研究了电池荷电状态(SOC)的估算方法,并根据SOC估算算法精度和系统实时性要求,提出了安时(AH)积分算法-卡尔曼(Kalman)算法(AH-Kalman)交叉运行的SOC估算策略。该策略用开路电压(OCV)法确定SOC初值,以实时性较强的AH积分法为主,采用间歇运行的Kalman滤波法修正安时计量法积分误差。建立了系统仿真模型,验证了卡尔曼滤波算法对安时积分法积累误差的修正作用。将控制算法生成C代码下载到目标控制器,搭建微控制器在环测试验证(PILS)平台,进行了与传统卡尔曼滤波算法的复杂度对比分析。结果表明,所提出AHKalman交叉运行的SOC估算策略在保证了SOC估算精度的同时也具有较好的实时性,便于实际应用。     

A Novel Potassium‐Ion‐Based Dual‐Ion Battery

In this work, combining both advantages of potassium‐ion batteries and dual‐ion batteries, a novel potassium‐ion‐based dual‐ion battery (named as K‐DIB) system is developed based on a potassium‐ion electrolyte, using metal foil (Sn, Pb, K, or Na) as anode and expanded graphite as cathode. When using Sn foil as the anode, the K‐DIB presents a high reversible capacity of 66 mAh g^?1 at a current density of 50 mA g^?1 over the voltage window of 3.0–5.0 V, and exhibits excellent long‐term cycling performance with 93% capacity retention for 300 cycles. Moreover, as the Sn foil simultaneously acts as the anode material and the current collector, dead load and dead volume of the battery can be greatly reduced, thus the energy density of the K‐DIB is further improved. It delivers a high energy density of 155 Wh kg^?1 at a power density of 116 W kg^?1, which is comparable with commercial lithium‐ion batteries. Thus, with the advantages of environmentally friendly, cost effective, and high energy density, this K‐DIB shows attractive potential for future energy storage application.     

Defect Engineering toward Atomic Co–Nx–C in Hierarchical Graphene for Rechargeable Flexible Solid Zn‐Air Batteries

Rechargeable flexible solid Zn‐air battery, with a high theoretical energy density of 1086 Wh kg^?1, is among the most attractive energy technologies for future flexible and wearable electronics; nevertheless, the practical application is greatly hindered by the sluggish oxygen reduction reaction/oxygen evolution reaction (ORR/OER) kinetics on the air electrode. Precious metal‐free functionalized carbon materials are widely demonstrated as the most promising candidates, while it still lacks effective synthetic methodology to controllably synthesize carbocatalysts with targeted active sites. This work demonstrates the direct utilization of the intrinsic structural defects in nanocarbon to generate atomically dispersed Co–N_x–C active sites via defect engineering. As‐fabricated Co/N/O tri‐doped graphene catalysts with highly active sites and hierarchical porous scaffolds exhibit superior ORR/OER bifunctional activities and impressive applications in rechargeable Zn‐air batteries. Specifically, when integrated into a rechargeable and flexible solid Zn‐air battery, a high open‐circuit voltage of 1.44 V, a stable discharge voltage of 1.19 V, and a high energy efficiency of 63% at 1.0 mA cm^?2 are achieved even under bending. The defect engineering strategy provides a new concept and effective methodology for the full utilization of nanocarbon materials with various structural features and further development of advanced energy materials.