The safety issues of lithium ion batteries pose ongoing challenges as the market for Li-ion technology continues to grow in personal electronics, electric mobility, and stationary energy storage. The ...severe risks posed by battery thermal runaway necessitate safeguards at every design level – from materials, to cell construction, to module and pack assembly. One promising approach to pack thermal management is the use of phase change composite materials (PCC™), which offer passive protection at low weight and cost while minimizing system complexity. We present experimental nail penetration studies on a Li-ion pack for small electric vehicles, designed with and without PCC, to investigate the effectiveness of PCC thermal management for preventing propagation when a single cell enters thermal runaway. The results show that when parallel cells short-circuit through the penetrated cell, the packs without PCC propagate fully while those equipped with PCC show no propagation. In cases where no external short circuits occur, packs without PCC sometimes propagate, but not consistently. In all test conditions, the use of PCC lowers the maximum temperature experienced by neighboring cells by 60 °C or more. We also elucidate the propagation sequence and aspects of pack failure based on cell temperature, voltage, and post-mortem data.
•Nail penetration is conducted on Li-ion packs with phase change composite (PCC™).•Thermal runaway propagation is observed in baseline tests on packs without PCC.•Propagation is prevented in the corresponding packs with PCC thermal management.•PCC reduces the max temperature of cells surrounding the penetrated cell by 60 °C.
The thermal conductivity of paraffin wax was increased by two orders of magnitude by impregnating porous graphite matrices with the paraffin. The graphite matrices were fabricated by compacting flake ...graphite that had been soaked in a bath of sulfuric and nitric acid then heat-treated at 900
°C. The properties of the graphite matrix and paraffin phase change material (PCM) composites were measured for graphite matrix bulk densities ranging from 50
g/L to 350
g/L. The properties studied include the thermal conductivity in directions parallel and perpendicular to the direction of compaction, paraffin mass fraction, and the latent heat of fusion of the composite samples. The latent heat of fusion and phase change characteristics of the graphite/paraffin composites were studied using differential scanning calorimetry (DSC). Scanning electron microscope (SEM) pictures are included to visualize the morphology of the graphite during each stage of the composite fabrication process. The performance of the PCM-composite was demonstrated by using the PCM-composite as a passive thermal management system for a lithium ion battery pack discharged at high rates.
The use of phase change materials (PCMs) in thermal storage is not a new concept, but engineers are continually finding new ways to utilize them in a wide range of applications. A PCM takes advantage ...of high latent heat in the phase change process to store large amounts of heat while undergoing only a small change in temperature. This property makes PCMs suitable for thermal storage purposes in a wide range of engineering applications. Due to the nature of these applications, it is vital to have a precise knowledge of the thermal characteristics of any PCM. Unfortunately, due to the low thermal conductivities and high latent heats found in PCMs, current measuring tools such as differential scanning calorimetry, provide inconsistent results. This paper conjectures that these errors come from the effects of low thermal diffusivity samples as well as improper data analysis methods.
The discharge and charge mechanisms of rechargeable Li-O2 batteries have been the subject of extensive investigation recently. However, they are not fully understood yet. Here we report a systematic ...study of the morphological transition of Li2O2 from a single crystalline structure to a toroid like particle during the discharge-charge cycle, with the help of a theoretical model to explain the evolution of the Li2O2 at different stages of this process. The model suggests that the transition starts in the first monolayer of Li2O2, and is subsequently followed by a transition from particle growth to film growth if the applied current exceeds the exchange current for the oxygen reduction reaction in a Li-O2 cell. Furthermore, a sustainable mass transport of the diffusive active species （e.g., O2 and Li＋） and evolution of the underlying interfaces are critical to dictate desirable oxygen reduction （discharge） and evolution （charge） reactions in the oorous carbon electrode of a Li-O2 cell.
•Passive thermal management system of Lithium-ion cells.•Expanded graphite/paraffin wax phase change composite fabrication.•Selective laser sintering 3D printing technique without ...post-processing.•Experimental and Finite Element Analysis validation of the fabricated composite.•Customizable material composition based on the application.
This paper investigates the thermal management performance of a newly developed phase change composite for Lithium-ion battery packaging applications. Phase change materials have been investigated for passive thermal management of lithium-ion batteries on maintaining a uniform temperature, reducing the operational risk possibility, and elongating the life cycle. Despite these advances, the manufacturing of such material for battery thermal management is still not simple. Challenges including material waste, limited design freedom, and long production time remain and significantly limit the broader application of phase change materials in thermal management. To address those challenges, the phase change composite in this paper was produced using a 3D printing technique called selective self-binding laser sintering. The effectiveness of the 3D printed composites on thermal management of lithium-ion battery cells is investigated and compared with other phase change composites manufactured by conventional techniques. The composite studied in this paper consists of expanded graphite and paraffin wax. Equivalent heat generations of a cylindrical 18,650 Lithium-ion cell are resembled using a thin polyimide heater, and performances of the composites in thermal management are characterized. Experimental results and finite element analysis show that the 3D printed phase change composite can achieve thermal management functions comparable with the composites manufactured by the conventional press and soak technique.
Lithium-ion batteries play a crucial role in present-day energy storage systems, necessitating the development of precise prediction models to improve their performance and ensure safety. The present ...study introduces a comprehensive methodology that encompasses the calibration, validation, and application of two separate Li-ion battery electrochemical models: the equivalent circuit model and the electrochemistry-based model. The calibration and validation of these models are based on experimental data conducted under various operating conditions, including charge/discharge rates, calendaring temperature, and Hybrid Pulse Power Characterization (HPPC) tests. After the successful validation process, these models are used to generate synthetic data tailored to real-world applications, particularly electric vertical takeoff and landing vehicles (eVTOL). The primary objective is to assess the precision of battery performance prediction, wherein the synthetic data is thoroughly compared with real experimental data. The results demonstrate the effectiveness of the proposed approach in developing a model that reduces dependence on labor-intensive testing and associated equipment costs, reduces time for experimentation, and accelerates controller development for batteries. This work highlights the importance of precise predictive models in lithium-ion batteries, facilitating the effective investigation of practical applications and advancements in energy storage technology.
In this study, two inorganic phase change materials (PCM) were tested to be used for thermal control of lithium-ion batteries. Paraffin wax was used as a reference material. To increase thermal ...conductivity, the PCMs were impregnated into the expanded graphite matrix, forming composite PCM (CPCM). Four types of Li-ion battery packs were manufactured to show the difference in performance between the packs with various CPCMs and No-CPCM.
Electrical cycling studies at ambient temperature showed that at C/2 discharge the No-CPCM pack surpasses 35 °C, while all CPCM packs remain around 30 °C, demonstrating similar behavior. At 1C discharge, No-CPCM pack reaches 49 °C, whereas the CPCM packs do not exceed 40 °C. At 2C discharge, the No-CPCM pack overpassed the safety limit of 65 °C and was stopped before completing the first discharge. The CPCM packs successfully completed the cycling. Studies performed at 45 °C demonstrate a similar trend, but with higher peak temperatures. Nail penetration testing proved that the inorganic CPCMс inhibited the pack from self-accelerated degradation, successfully prevented thermal runaway propagation and potential explosion. Low cost and incombustibility make inorganic PCMs а viable alternative to the organic PCMs, with a positive impact on environmental and economic issues.
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•Inorganic phase change materials are effective for Li-ion batteries thermal control.•Batteries are maintained at uniform temperatures and in safe temperature range.•Thermal runaway propagation was successfully prevented.
A passive thermal management system is evaluated for high-power Li-ion packs under stressful or abusive conditions, and compared with a purely air-cooling mode under normal and abuse conditions. A ...compact and properly designed passive thermal management system utilizing phase change material (PCM) provides faster heat dissipation than active cooling during high pulse power discharges while preserving sufficiently uniform cell temperature to ensure the desirable cycle life for the pack. This study investigates how passive cooling with PCM contributes to preventing the propagation of thermal runaway in a single cell or adjacent cells due to a cell catastrophic failure. Its effectiveness is compared with that of active cooling by forced air flow or natural convection using the same compact module and pack configuration corresponding to the PCM matrix technology. The effects of nickel tabs and spacing between the cells were also studied.
•High thermal conductivity phase change composite for thermal energy storage.•Hybrid HVAC/thermal energy storage with high-conductivity phase change composite.•Hybrid HVAC-TES for flexible resource ...to shave/shift on-peak power demand.•HVAC efficiency and optimized control strategies for smart grid applications.•HVAC-thermal storage system level modeling and simulation study using Aspen Plus®.
This paper evaluates the use of a phase change composite (PCC) material consisting of paraffin wax (n-Tetradecane) and expanded graphite as a potential storage medium for cold thermal energy storage (TES) systems to support air conditioning applications. The PCC-TES system is proposed to be integrated with the vapor compression refrigeration cycle of an air conditioning (AC) system. The use of this PCC material is novel because of its unique material and thermal characteristics as compared to ice or chilled water that are predominantly used in commercial TES systems for air cooling applications. The work of this paper proposed and tested a hypothesis, which suggests that integrating a conventional AC with a PCC-TES would result in significant benefits concerning compressor size, compressor efficiency, electricity consumed and CO2 emissions. The proposed integration would also contribute to reduce electricity demand during peak hours and reduce necessity to build more expensive power plants and distribution lines. To test the hypothesis, a simulation model in Aspen Plus® software was prepared. However, Aspen Plus® does not have a built-in library to predict PCC’s melting and solidification behaviors. Therefore, an analytical heat transfer model was written as a system of equations in Fortran code into Aspen Plus® calculation block to simulate the phase change behavior and associated characteristics. The overall simulation model, which was designed specifically for this research work, consists of two main parts that communicate with each other. The first part simulates the AC’s refrigeration loop using the built-in Aspen Plus® components and the second part implements the PCC heat transfer model written within the calculation block of Aspen Plus®. The simulation model was validated by crosschecking the calculated results with actual experimental data from an actual 4 kWh PCC-TES benchtop thermal storage system. Very good agreement was observed between the simulations and laboratory data. Simulated performance of the proposed integration between the AC and the PCC-TES indicated the potential to (1) downsize the compressor by 50%, (2) lower electrical consumption by the compressor by 30%, (3) lower CO2 emissions by 30%, and (4) double the compressor efficiency during off and mid peak hours. The present work is a conceptual design and optimization study and does not account for integration inefficiencies, energy losses, real-world operation complexity, and added capital cost of TES integration with AC systems.
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