Electric vehicle (xEV) battery durability significantly impacts the long-term operation, consumer satisfaction, and market adoption of xEVs. As driving range diminishes over time, it affects vehicle service life and lifecycle GHG emissions. Measuring the full service life of xEV batteries in laboratory tests presents technical and logistical challenges, necessitating representative measurements for parameterizing numerical models. These models are crucial for predicting long-term performance and rely on high-quality experimental data. While performance and aging trends under extreme temperatures are documented, cell thermal contact conditions suitable for direct model input are not well characterized. This study investigates lithium-ion cells from three xEV types, cycled at constant currents from C/40 to 1C, at temperatures between −15 °C and +45 °C, over 1000 cycles in a multi-year campaign. Stable isothermal cell temperatures were achieved using custom-built liquid immersion baths with forced convection, highlighting fundamental electrochemical behaviors by decoupling complex self-heating not typically monitored in air environments. The data inform and validate physics-based models on temperature-dependent performance and durability, providing operational limits to enhance cell and battery thermal management design and educate xEV consumers about conditions affecting performance, range, and durability.

As part of an on-going research effort towards developing a comprehensive overview of contributing operational factors to lithium ion battery degradation, new analysis and results are presented here which demonstrate the durational effects of battery charge and discharge operations on cell capacity loss. A set of cell cycling tests with a range of different discharge amplitudes provided data for this analysis which led to an advance on how to quantitatively account for the degradation effects in terms of their temporal duration. A factor accounting for operational duration effects usable as a parameter in battery life models was a key result of this project. An additional set of cell cycling experiments was conducted with the aim of decoupling degradation rates attributable to either the discharge or recharge portion of the complete cycle, and some differences were observed and quantified.

•Novel 3D electrochemical model with heat generation, gives thermal field in prismatic cells.•investigated Ice plates (flush with cell face) and Cold plates (bottom surface of cell)•Thermal profiles found as function of drive cycle, cooling regime and battery case material.•Ice plates give thermal rises 5–8 K less than Cold plate, and provide narrower ΔT range•among battery case materials tested, Cold plate cooling is best with thick aluminum

This study combined a simple two-dimensional (2D) finite volume model (Kim model), which employs Ohm's law along with charge conservation over the electrodes and Butler–Volmer charge transfer kinetics for prismatic battery cells coupled with the single particle model (SPM) in order to model the thermal state of automotive battery packs. The objective here was to determine the effects of liquid cooling applied to the packs under standard driving cycles. A model developed by Kim provided a means for determining a nonuniform current distribution over the surface of the current collectors. The Kim model is based on the application of Ohm's law over a conducting medium, with empirical source terms representing current flowing into or out of an adjacent electrode layer. Here, a modeling advance is presented where empirical source terms in the Kim model were replaced with ones based on the chemistry and physics occurring inside the battery. As such, fundamental battery function was imparted to the model by integrating the SPM into the 2D finite volume Kim model. The 2D procedure described above was carried out on electrode sheets at different positions inside the cell, and determined thermal generation values that were mapped volumetrically into a heat transfer simulation, which, in turn, updated the electrochemical simulation. Capacity fade kinetics were determined by fitting experimental data to simulated results. With time-temperature profiles produced as described above for different pack cooling levels and varying degrees of cell degradation, a basic SPM simulation was then used with thermal overlays to estimate automotive cell life under various driving scenarios and various cooling levels. With these simulations, scenarios representing different thermal management regimes along with driving behavior were able to show the combined impact on automotive battery pack lifetimes.

This study combines a two-dimensional Ohm's law finite-volume approach determining the current distribution in prismatic battery cells with a simplified electrochemical model for the thermal state of automotive battery packs. The objective was to develop a simulation tool for assessing the effect of cooling effort applied to automotive battery packs under real-life usage conditions. The Ohm's law model was enhanced by imparting a chemical and physical basis to source terms previously found empirically. This simulation was applied to 2D electrode sheets, determining thermal generation values that were mapped volumetrically into a thermal simulation, which in turn, updated the electrochemical simulation. Battery parameters, along with capacity fade kinetics were determined by fitting experimental data to simulated results. Dynamometer data from tests under reference drive cycles provided current demands on battery cells. Thermal profiles simulated for 30 A h prismatic cells at different cooling levels. Passive and forced air cooling simulations both gave endpoint temperatures upwards of 40 degrees C (313 K), considered excessive for preserving the battery life. A simulation scenario which reflected a liquid cooling system kept the temperature gain for a US06 drive cycle to about 2 K. With liquid cooling, an automotive battery is better protected against thermally driven degradation.

We report on the thermal stability of lithium iron phosphate (LiFePO4) cathode material as investigated by accelerating rate calorimetry (ARC). LiFePO4 (LFP) was prepared using three different synthetic methods, namely, solid state (P1), hydrothermal (P2) and molten state (P3) and have different particle sizes (in the range of similar to 100 nm-3 mu m) and different surface areas (in the range of similar to 6-14 m(2) g(-1)). The thermal stability was evaluated, prior and after charging LiFePO4, in the presence of either carbonate solvents (ethylene carbonate (EC): diethyl carbonate (DEC) (1:2 v/v)) or electrolyte (1 M LiPF6 in the same solvent). In the presence of the electrolyte, LiFePO4 is shown to be stable up to 280 degrees C or 220 degrees C for uncharged or charged cathode materials, respectively. The surface area of LiFePO4 is found to affect the initial self-heating rate (SHR) of the charged materials reaction with the electrolyte, while the presence of the LiPF6 salt reduces significantly the SHR of the combustion reaction of carbonates solvent initiated by the oxygen released from the cathodes; forming Fe2P2O7 at elevated temperatures. (C) 2016 The Electrochemical Society. All rights reserved.

The thermal stability of a high-voltage spinel cathode (LiMn1.5Ni0.5O4), synthesized via a sol-gel method, was investigated using Accelerating Rate Calorimetry (ARC) and compared to that of LiMn2O4. Both cathode materials crystallize in the Fd (3) over barm space group with nearly identical surface areas (similar to 0.65 m(2) g(-1)), but they show different microstructures and morphologies that affect their reactivity. In the presence of 1 M LiPF6 in ethylene carbonate (EC): diethyl carbonate (DEC) (1: 2 v/v) electrolyte, both materials show an exothermic surface reaction that is dependent on the cathode morphology, at relatively low temperatures (below 200 degrees C). The onset temperature of the self-heating reaction for Li1-xMn1.5Ni0.5O4 sample is found to be as low as 60 degrees C (compared to 140 degrees C for Li1-xMn2O4), significantly affecting the thermal stability of a whole battery containing LiMn1.5Ni0.5O4 as the cathode. The decomposition of the spinel material takes place at 195 degrees C for Li1-xMn1.5Ni0.5O4 and at 215 degrees C for Li1-xMn2O4, with significantly higher self-heating rates for Li1-xMn1.5Ni0.5O4 than for LiMn2O4. Our results show that, above 200 degrees C, Ni4+ is reduced to the more stable Ni2+ oxidation state and the oxygen released from the cathode during this reaction fuels the combustion of carbonate solvents. (C) 2016 The Electrochemical Society. All rights reserved.

Energy storage units have become important components in residential micro-cogeneration (MCG) systems. As MCG systems are often connected to single residences or buildings in a wide variety of settings, they are frequently unique and highly customized. Lithium-ion batteries have recently gained some profile as energy storage units of choice, because of their good capacity, high efficiency, robustness and ability to meet the demands of typical residential electrical loads. In the present work, modeled scenarios are explored which examine the performance of a MCG system with an internal combustion engine, photovoltaic input and a Li-ion storage battery. An electricity demand profile from new data collected in Ottawa, Canada is used to provide a full year energy use context for the analyses. The demands placed on the battery are examined to assess the suitability of the battery size and performance, as well as control related functionalities which reveal significantly varying battery use, and led to a quantitative expression for equivalent cycles. The energy use simulations are derived from electrochemical fundamentals adapted for a larger battery pack. Simulation output provides the basis for techno-economic commentary on how to assess large-scale Li-ion batteries for effective electrical storage purposes in MCG systems, and the impact of the nature of the control strategy on the battery service life. Crown Copyright (C) 2014 Published by Elsevier Ltd. All rights reserved.

In this work, we designed two redox shuttles with high solubility (up to 1 M) in conventional carbonate-based lithium-ion battery (LIB) electrolytes. At this high concentration, redox shuttles ensure improved overcharge protection than lower concentrations. We developed electroactive imidazolium salts by modifying imidazolium with 2,5-di-tert-butyl-1,4-dimethoxybenzene. Two salts with the cation 1-(3-(2,5-di-tert-butyl-1,4-methoxyphenoxy) propyl)-3-methyl-1H-imidazol-3-ium (EMIm) were synthesized using either hexafluorophosphate (DDB-EMIm-PF6) or bis(trifluromethanesulfonyl) amide (DDB-EMIm-TFSI)) anions. The electrochemical properties of DDB-EMIm-PF6 and DDB-EMIm-TFSI dissolved in ethylene carbonate : diethyl carbonate (EC:DEC), in the presence of either LiPF6 or LiTFSI, were evaluated. Cyclic voltammetry showed a compatible potential (similar to 3.85 V vs. Li/Li+) for use in LIBs using LiFePO4 as cathodes. Electrolytes using 0.1 M of DDB-EMIm-PF6 or 0.3, 0.7 and 1 M of DDB-EMIm-TFSI were prepared and evaluated in Li/LiFePO4 (LFP) test cells to demonstrate overcharge protection. Electrochemical cycling at C/10 showed an overcharge protection for all concentrations of the redox ionic salts under 100% overcharge conditions. Among these salts, DDB-EMIm-TFSI, at a concentration of 0.7 M, was effective in shuttling excess current for over 200 cycles, representing over 6000 operating hours, while maintaining nominal values for the discharge capacity of LiFePO4. (C) 2015 The Electrochemical Society.

In this work, the high voltage LiMn1.5Ni0.5O4 cathode material has been synthesized as octadecahedron crystals with a disordered spinel structure and has been coated with a carbon layer from two different precursors (sucrose and Xerogel carbon) to improve its performance in Li-ion batteries. The effect of carbon coating on the physical and electrochemical properties of the crystals has been evaluated using X-ray diffraction (XRD), Infrared (IR) and Raman spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), elemental and surface area (BET) analyses and battery cycling at different charge/discharge rates and temperatures. It was found that the amount of carbon, present as a thin layer (5-10 nm) and estimated at <1 w.t.%, causes an increase in electronic conductivity with no effect on crystal structure. Battery results of the cathode material in half cells show that carbon coating greatly improves the discharge capacity, rate capability at room temperature and 60 degrees C as well as cycling stability. Moreover, the material coated from Xerogel carbon shows the highest capacity at 10 C rate and 60 degrees C. Crown Copyright (C) 2014 Published by Elsevier B.V. All rights reserved.

Lithium-ion batteries (LIBs) have revolutionized society by extending the portability of personal electronic devices. They have high energy density and good cycle life compared to other energy storage systems. The properties of the first generation of LIBs aroused the interest of scientists to improve upon them while expanding their applications. As a result, there have been a variety of chemistries in development for LIB.1 Due to this multitude of chemistries, LIBs can be tuned to suit a wide number of applications. Currently, they are not only limited to small portable electronic devices but include large-scale applications as well. Smart grids, electric vehicles can be powered by LIB packs.2 To make electric vehicles as popular as cellular phones amongst consumers, their LIBs must provide high energy without compromising the users’ safety. This energy can be increased by either raising the operating potential or the specific capacity. For safety, two levels should be considered; the single LIB cell and the pack design. The former implies the intrinsic thermal stability of the active material itself and its interaction with the other cell components, whereas the latter is associated to issues originating from differences in the state of charge (SOC) in each cell within the pack as well as the pack design itself. A difference in the SOC of individual cells may lead to an overcharge abuse condition causing local chemical and electrochemical reactions that might be extended to the whole pack. As a result, gas release or temperature increase can generate an out-of-control accelerated reaction. The consequences of such situations are more complicated in systems that dissipate heat inefficiently like LIB packs. To protect LIBs against overcharge, the use of safety mechanisms like redox-shuttles has been proposed.3 Redox-shuttles act electrochemically by carrying the excess current between the two electrodes in a cell during overcharge. Several redox-shuttles used as additives in common LIBs’ electrolytes have been reported.3 Moreover, when the benefit of redox shuttle protection can be incorporated into ionic liquids by functionalizing the ions with an electroactive moiety, the LIB’s safety is expected to be improved.4 The fundamental parameters identified above can be evaluated by Accelerating Rate Calorimetry (ARC). It consists of simulating the same conditions of heat dissipation in an actual LIB pack where the heat generated from an eventual exothermic reaction is not very well dissipated from the initiation point, resulting in heat build-up in a small area. This can generate an out of control reaction. The ARC allows the investigation of these reactions under adiabatic conditions in order to understand and improve the thermal properties of the studied samples. In this presentation, a study of the thermal stability of different cathode materials will be reported. The investigated materials represent different chemistries, (LiCoO2, LiFePO4 and LiMn2-x NixO4), in order to understand the relationship between the structure and the thermal behaviour of cathode materials. Additionally, two imidazolium (EMIm)-based ionic liquids incorporating 2,5-di-tert-butyl-1,4-dimethoxybenzene were studied and will be presented; (DDB-EMIm-TFSI) and (DDB-EMIm-PF6). Their electrochemical behaviour in Lithium-ion cells and their thermal properties were investigated . References: 1. J. B. Goodenough and Y. Kim, Chemistry of Materials, 2009, 22, 587-603. 2. V. Etacheri, R. Marom, R. Elazari, G. Salitra and D. Aurbach, Energy & Environmental Science, 2011, 4, 3243-3262. 3. Z. H. Chen, Y. Qin and K. Amine, Electrochimica Acta, 2009, 54, 5605-5613. 4. J. C. Forgie, S. El Khakani, D. D. MacNeil and D. Rochefort, Physical Chemistry Chemical Physics, 2013, 15, 7713-7721.

The use of Lithium ion batteries in electronic devices continues to grow, the popularity stems from the excellent cycle life and the ability to store more energy per volume than any other portable rechargeable battery currently available. 1 However, one major problem of the Li-ion battery is preventing it from going into an abuse situation. An abuse situation is when a cell is overcharged; causing degradation of the battery and in some cases exothermic reactions at elevated temperatures. 2 There are however several safety mechanisms that can be employed to prevent the overcharge situation.

LiFePO4/C composite materials have been synthesized from a low cost Fe2O3 precursor by a hydrothermal method to make LiFePO4(OH) in a first step followed by a fast calcination and carbon coating. This method combines the advantages of both hydrothermal and solid state synthetic methods. The as-prepared LiFePO4/C provides enhanced discharge capacity and cycling stability compared to LiFePO4 synthesized using a solid state method with the same precursors. Thus, the method to be described herein is a promising option in the search to reduce the cost of large-scale synthesis of LiFePO4/C for use in lithium-ion batteries, while maintaining adequate electrochemical performance.