Modularized battery management for large lithium ion cells

A modular electronic battery management system (BMS) is described along with important features for protecting and optimizing the performance of large lithium ion (LiIon) battery packs. Of particular interest is the use of a much improved cell equalization system that can increase or decrease individual cell voltages. Experimental results are included for a pack of six series connected 60 Ah (amp-hour) LiIon cells.     

Differential pulse effects of solid electrolyte interface formation for improving performance on high-power lithium ion battery

Solid electrolyte interface (SEI) formation is a key that utilizes to protect the structure of graphite anode and enhances the redox stability of lithium-ion batteries before entering the market. The effect of SEI formation applies a differential pulse (DP) and constant current (CC) charging on charge-discharge performance and cycling behavior into brand new commercial lithium ion batteries is investigated. The morphologies and electrochemical properties on the anode surface are also inspected by employing SEM and EDS. The electrochemical impedance spectra of the anode electrode in both charging protocols shows that the interfacial resistance on graphite anodes whose SEI layer formed by DP charging is smaller than that of CC charging. Moreover, the cycle life result shows that the DP charging SEI formation is more helpful in increasing the long-term stability and maintaining the capacity of batteries even under high power rate charge-discharge cycling. The DP charging method can provide a SEI layer with ameliorated properties to improve the performance of lithium ion batteries.     

Mathematical modeling of a lithium ion battery with thermal effects in COMSOL Inc. Multiphysics (MP) software

The existing lithium ion battery model in Multiphysics (MP) software (COMSOL Inc., Palo Alto, CA) is extended to include the thermal effects. The thermal behavior of a lithium ion battery is studied during the galvanostatic discharge process with and without a pulse.     

Preparation and characterization of tin-based three-dimensional cellular anode for lithium ion battery

A three-dimensional cellular Sn-based anode has been prepared by electrodepositing tin onto 3D copper matrix under different current conditions and characterized by means of scanning electron microscope (SEM), X-ray diffraction (XRD), electrochemical cycling test. The properties of tin layer, such as particle size, porosity and shape, greatly affect cycling behavior of electrodes. Beside this, two additional factors including large bonding force and three-dimensional stress-alleviated environment are also important to the dimensional stability of electrodeposited layer. In order to improve cycling performance, a composite anode configuration is designed by casting inactive carbon black into the “valley-ridge” tin-coated architecture. Capacity fading of both anodes is remarkably suppressed with the help of mechanical compression coming from stuffing. Taking advantage of the 3D electrode configuration, CTA with stuffing experiences a more uniform diffusion process to form an intermetallic layer of Cu₆Sn₅ when heated and shows better cyclicity than 2D annealed anode.     

Thermal analysis of high‐power lithium‐ion battery packs using flow network approach

High‐power applications of lithium‐ion batteries require efficient thermal management systems. In this work, a lumped capacitance heat transfer model is developed in conjunction with a flow network approach to study performance of a commercial‐size lithium‐ion battery pack, under various design and operating conditions of a thermal management system. In order to assess the battery thermal management system, capabilities of air, silicone oil, and water are examined as three potential coolant fluids. Different flow configurations are considered, and temperature dispersions, cell‐averaged voltage distributions, and parasitic losses due to the fan/pump power demand are calculated. It is found that application of a coolant with an appropriate viscosity and heat capacity, such as water, in conjunction with a flow configuration with more than one inlet will result in uniform temperature and voltage distributions in the battery pack while keeping the power requirement at low, acceptable levels. Simulation results are presented and compared with literature for model validation and to show the superior capability of the proposed battery pack design methodology. Copyright © 2014 John Wiley & Sons, Ltd.     

Structural characterization and electrochemical properties of non-graphitizable carbons for a lithium ion battery

Structural characteristics and electrochemical properties of non-graphitizable carbons were investigated. The carbons were obtained by heat-treating the oxidized graphitizable carbon precursors with various molar ratios of aromatic compounds and cross-linking agent. The discharge profiles of the non-graphitizable carbons heat-treated at 600°C had one plateau discharge region at 1.0 V vs. Li/Li⁺, which is similar to graphitizable ones heat-treated at the temperature. However, the discharge profiles of the non-graphitizable carbons heat-treated above 800°C exhibited two plateau discharge regions at 0.2 and 1.0 V vs. Li/Li⁺. The discharge capacities of the non-graphitizable carbons increased with an increase of cavity volume, which was controlled by molar ratios of aromatic compound and cross-linking agent. The structural parameters proposed were measured to compare with each other, and it was found that they showed good correlation.     

Surface structure and electrochemical characteristics of plasma-fluorinated petroleum cokes for lithium ion battery

Plasma-fluorination of petroleum coke and those heat-treated at 1860, 2300 and 2800 °C (abbreviated to PC, PC1860, PC2300 and PC2800) was conducted for 15, 30 and 60 min using CF₄ gas at 90 °C. Fluorine contents obtained by elemental analysis were negligible except PC fluorinated for 60 min (0.7 at.%). Fluorine concentration on the surface decreased with increasing heat-treatment temperature of petroleum coke, i.e. from PC to PC2800 when plasma-fluorination was made for 30 and 60 min. Transmission electron microscopic observation revealed that the closed edges of PC2800 were destroyed and opened by plasma-treatment. Plasma-fluorination increased surface disorder of heat-treated petroleum cokes, however, slightly reduced surface areas. These surface structure changes increased first coulombic efficiencies of PC2300 and PC2800 by 6–8 and 8–10% at both 60 and 150 mA g⁻¹, respectively.     

Thermal management system of lithium‐ion battery module based on micro heat pipe array

Temperature affects the performance of electric vehicle battery. To solve this problem, micro heat pipe arrays are utilized in a thermal management system that cools and heats battery modules. In the present study, the heat generation of a battery module during a charge‐discharge cycle under a constant current of 36 A (2C) was computed. Then, the cooling area of the condenser was calculated and experimentally validated. At rates of 1C and 2C, the thermal management system effectively reduced the temperature of the module to less than 40°C, and the temperature difference was controlled less than 5°C between battery surfaces of the module. A heating plate with 30‐W power effectively improved charge performance at low temperature within a short heating time and with uniform temperature distribution. Charge capacity obviously increased after heating when battery temperature was below 0°C. This study presents a new way to enhance the stability and safety of a battery module during the continuous charge‐discharge cycle at high temperatures and low temperatures accordingly.     

Electrodeposited Ni–Sn intermetallic electrodes for advanced lithium ion batteries

Various samples of Ni_xSn_y metallic alloys electrodeposited under different current and time regimes have been prepared and tested in lithium cells. The results clearly demonstrate that the electrochemical performance of these intermetallic electrodes greatly depends on the synthesis conditions which in turn reflect on the type of morphology and phase of the various samples. The best electrode cycled with a high capacity delivery, i.e. of the order of 550 mA hg⁻¹ and showed an efficient behaviour when used as anode in a lithium ion battery using LiNi_0.5Mn_1.5O₄ as cathode. These results confirm that the electrodeposition is a very promising synthesis tool for monitoring the morphological and phase conditions of Ni_xSn_y and that the approach described in this work may be used for further optimizing this intermetallic electrode.     

High-throughput quantum chemistry and virtual screening for lithium ion battery electrolyte additives

Advances in the stability and efficiency of electronic structure codes along with the increased performance of commodity computing resources has enabled the automated high-throughput quantum chemical analysis of materials structure libraries containing thousands of structures. This allows the computational screening of a materials design space to identify lead systems and estimate critical structure-property limits which should prove an invaluable tool in informing experimental discovery and development efforts. Here this approach is illustrated for lithium ion battery additives. An additive library consisting of 7381 structures was generated, based on fluoro- and alkyl-derivatized ethylene carbonate (EC). Molecular properties (e.g. LUMO, EA, μ and η) were computed for each structure using the PM3 semiempirical method. The resulting lithium battery additive library was then analyzed and screened to determine the suitability of the additives, based on properties correlated with performance as a reductive additive for battery electrolyte formulations.     

Electrochemical properties of cross-linked polymer electrolyte by electron beam irradiation and application to lithium ion batteries

A polymer electrolyte was successfully fabricated for a room temperature operation lithium battery by cross-linking the mixture of oligomeric poly (ethylene glycol) dimethylether (PEGDME) and poly (ethylene glycol) diacrylate (PEGDA) with Li(CF₃SO₂)₂N using electron beam irradiation. The maximum ionic conductivity achieved for the cross-linked solid polymer electrolyte (c-SPE) at room temperature was 2.1 × 10⁻⁴ S cm⁻¹ and the lithium transport number of the electrolyte was around 0.2. The c-SPE showed no reaction heat with lithium metal up to 300 °C. The interface resistance of Li/c-SPE/Li at room temperature was about 45 Ω cm², which is considerable lower than that of 210 Ω cm² for Li/PEO₁₀Li(CF₃SO₂)₂N/Li. The electrochemical window of the polymer electrolyte was above 4 V (versus Li⁺/Li). The initial discharge capacity for the Li/SPE/LiFePO₄-C cell was approximately 90 mAh g⁻¹ for LiFePO₄-C at 1/10 °C rate at room temperature and showed a good cyclability and a high coulombic efficiency of 99.2%.     

Preparation and application of bamboo-like carbon nanotubes in lithium ion batteries

CNTs with bamboo-like structure (B-CNTs) has been prepared via a CVD process with novel carbon precursor. The potential application of B-CNTs as electric conductive additive and anode materials for lithium ion batteries was explored. The EIS spectra prove that it is better electric conductive additive than multiwalled CNTs and traditional carbon black (CB). The electric resistance of the electrode is decreased around 20 Ω when B-CNTs is used instead of CB. The cycle stability is also enhanced. However, the test cell with B-CNTs as anode material shows low reversible capacity of 135 mAh g⁻¹ and very low initial cycle efficiency of 17.3%, which indicates that so-prepared B-CNTs is not suitable for anode material.     

Patent analysis of lithium ion power battery recycling technology

锂离子动力电池的回收是当前储能产业关注的焦点之一,为了解锂离子动力电池的回收现状,以CNABS和DWPI专利数据库中的检索结果为分析样本,对锂离子动力电池回收技术的专利申请量趋势、全球分布区域、国内外主要申请人、全球重点技术分布以及国内重点技术进行全面分析,结果表明,虽然锂离子动力电池回收技术是目前全球尤其是中国争相布局的产业对象,但目前各个企业的专利申请量均较小且技术布局零散,总体来说锂离子动力电池回收技术仍处于摸索阶段,产业前景不明,本文以期给锂离子动力电池回收技术未来的布局和发展提供一定的借鉴。     

Performance assessment of a passive core cooling design for cylindrical lithium‐ion batteries

Battery thermal management (BTM) system is an indispensable component for large‐sized lithium‐ion battery packs used in aerospace and automotive applications. Besides providing a proper temperature range for batteries to operate, thus improving their efficiency, lifespan, and safety, the BTM system also needs to be well designed with considering the cost, weight, and practicability. In this paper, an internal passive BTM system is proposed for the cylindrical Li‐ion batteries. The design embeds a phase change material (PCM) filled mandrel inside the battery to achieve the cooling effect. A thermal test cell is first fabricated and tested in a wind tunnel under different cooling scenarios, and it is also used to verify a numerical thermal model. The proposed BTM system is further examined through the model and found to be able to create a preferable environment for batteries to operate. Specifically, the core BTM system consumes less PCM and achieves lower temperature rises and more uniform temperature distributions than an external BTM system. The proposed design can also exert its full latent heat to manage the heat generated from the battery without having a thermally conductive matrix, which is usually composite with PCM in external BTM systems. In addition, experiments show that the battery equipped with the proposed BTM system is ready for intensive cycling tests.     

Morphology effect on the electrochemical performance of NiO films as anodes for lithium ion batteries

NiO films were prepared by chemical bath deposition and electrodeposition method, respectively, using nickel foam as the substrate. The films were characterized by scanning electron microscopy (SEM) and the images showed that their morphologies were distinct. The NiO film prepared by chemical bath deposition was highly porous, while the film prepared by electrodeposition was dense, and both of their thickness was about 1 μm. As anode materials for lithium ion batteries, the porous NiO film prepared by chemical bath deposition exhibited higher coulombic efficiency and weaker polarization and its specific capacity after 50 cycles was 490 mAh g⁻¹ at the discharge–charge current density of 0.5 A g⁻¹, and 350 mAh g⁻¹ at 1.5 A g⁻¹, higher than the electrodeposited film (230 mAh g⁻¹ at 0.5 A g⁻¹, and 170 mAh g⁻¹ at 1.5 A g⁻¹). The better electrochemical performances of the film prepared by chemical bath deposition are attributed to its highly porous morphology, which shorted diffusion length of lithium ions, and relaxed the volume change caused by the reaction between NiO and Li⁺.     

A study of lithium ion intercalation induced fracture of silicon particles used as anode material in Li-ion battery

The fracture of Si particles due to internal stresses formed during the intercalation of lithium ions was described by means of a thermal analogy model and brittle fracture damage parameter. The stresses were calculated following the diffusion equation and equations of elasticity with an appropriate volumetric expansion term. The results were compared with the acoustic emission data from the experiments on electrochemical cycling of Li ion half-cells with silicon electrodes. A good correlation between experiment and prediction was observed. The results of computations with different particle sizes show the existence of a critical size below which fracture during the lithiation is not expected to occur. Such a critical size appears to be within micrometer scale.     

Strategic dispersion of carbon black and its application to ink-jet-printed lithium cobalt oxide electrodes for lithium ion batteries

The effects of surface-modified carbon black induced by UV/ozone and triethylenetetramine on the microstructure and electrochemical properties of ink-jet-printed LiCoO₂ electrodes for lithium ion batteries are observed. The dispersion properties of surface-modified carbon black and LiCoO₂ ink are evaluated using particle size distribution measurements, surface pressure calculations, and scanning electron microscopy. Modifications to the surface of carbon black result in improved dispersion properties, which in turn enhance the compactness and homogeneity of the microstructure of ink-jet-printed LiCoO₂ electrodes compared to those printed with as-received carbon black. Electrochemical experiments indicate that LiCoO₂ electrodes ink-jet-printed with surface-modified carbon black exhibit improved initial specific discharge capacities compared to those printed with as-received carbon black due to the better electrical contact between the carbon black and the LiCoO₂, as evidenced by the analysis of the area-specific impedance of the electrode as a function of the depth of discharge.     

Application of cyclohexyl benzene as electrolyte additive for overcharge protection of lithium ion battery

The electrochemical characterization and overcharge protection mechanism of cyclohexyl benzene as an additive in electrolyte for lithium ion battery was studied by microelectrode cyclic voltammetry, Galvanostatic charge–discharge measurements and SEM observation on both the cathode and separator of the overcharged cells. It was found that when the battery is overcharged, cyclohexyl benzene electrochemically polymerized to form polymer between separator and cathode at the potentials lower than that for electrolyte decomposition. The polymer blocks the overcharging process of the battery. The additive causes a small capacity loss and impedance increase in a real cell, but that can be mitigated if the operating voltage is much lower than the polymerization voltage.     

Preparation of hierarchical porous carbon and its rate performance as anode of lithium ion battery

A hierarchical porous carbon with low oxygen content has been prepared by using polystyrene (PS) spheres as template and its structure, composition and performances as anode of lithium ion battery are characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, element analysis (EA), electrochemical impedance spectroscopy (EIS), and galvanostatic charge/discharge test. The results obtained from SEM, TEM, XRD, FTIR, and EA indicate that the prepared sample has a well-interconnected pore structure with a pore size of 170 nm and has an oxygen content of 3.3 ± 0.2 wt.%. The low oxygen content of the prepared sample can be ascribed to the low decomposition temperature of the template that was determined by thermal analysis. EIS shows that the prepared sample has lower electrochemical impedance for the lithium insertion/de-insertion than commercial natural graphite and charge/discharge tests show that the battery using the prepared sample as anode exhibits better rate performance than that using the graphite.