Critical perspective on smart thermally self-protective lithium batteries
Jinqiu ZhouYunfei HuanLifang ZhangZhenkang WangXi ZhouJie LiuXiaowei ShenLanping HuTao QianChenglin Yan
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Thermal Runaway
Heat Generation
Thermal Runaway
Overheating (electricity)
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Based on the electrochemical and thermal model, a coupled electro-thermal runaway model was developed and implemented using finite element methods. The thermal decomposition reactions when the battery temperature exceeds the material decomposition temperature were embedded into the model. The temperature variations of a lithium titanate battery during a series of charge-discharge cycles under different current rates were simulated. The results of temperature and heat generation rate demonstrate that the greater the current, the faster the battery temperature is rising. Furthermore, the thermal influence of the overheated cell on surrounding batteries in the module was simulated, and the variation of temperature and heat generation during thermal runaway was obtained. It was found that the overheated cell can induce thermal runaway in other adjacent cells within 3 mm distance in the battery module if the accumulated heat is not dissipated rapidly.
Thermal Runaway
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Heat Generation
Lithium battery
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Thermal Runaway
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With the wide application of lithium-ion batteries (LIBs), it is important to understand the internal heating effects and thermal runaway behavior of such batteries to evaluate their thermal safety and improving thermal management systems. The heat generation of LiCoO2/graphite LIBs under various conditions was compared using calorimetry and electrochemical methods. The heat generation results of the two methods in the process of charging/discharging at different current rates were consistent, but the calorimetry method is simple, convenient, and more feasible. The greater the working current, the greater the irreversible heat generation. Through the identification of the thermal runaway behavior, it was found that the change of the onset temperature of self-heating reactions fluctuates in a narrow range. Thermal runaway after battery degradation is more likely to be triggered by the degradation of thermal stability.
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Improper design and abusive operations are identified to be major causes related to safety accidents of lithium-ion batteries.A robust and powerful mathematical-physical model based on relevant complex mechanisms that could be an effective tool for thermal analysis,structural design,and thermal management design of lithium-ion batteries is thus a critically requirement.In this paper a thermal abusing model is established particularly for oven tests of graphite/LiPF6 /LiCoO2 batteries to investigate the influence of heat release condition and temperature of oven on battery thermal behaviors by a series of simulations calculation.The simulation results can be applied for detail analysis of battery thermal behaviors.It is found that during abusing processes of oven heat and not leading to thermal runaway,the cathode zone of the battery is the maximum source of heat generation and the rate of heat generation depends mainly on the reaction between intercalated lithium and electrolyte and the decomposition of solid electrolyte interface(SEI);during abusing processes of oven heat and even leading to thermal runaway,the anode zone is the maximum source of heat generation and the rate of heat generation depends mainly on the reaction between anode and solvent.It is also found that the thermal behavior of the battery is dominated by the combined effect of conditions of heat release and oven temperature,the critical temperature of oven for thermal runaway rises with increase of the heat dissipation coefficient,and the critical dissipation coefficient of heat without thermal runaway increases when the oven temperature rises,indicating the importance of thermal design and management of batteries.
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Ultrahigh capacity lithium-ion batteries (LIBs) with prudent safety measures are key to future transportation. The undesirable thermal events such as thermal runaway (TR) in LIBs can pose a direct risk to battery life and the consumers. In the present study, a set of new TR criteria are established by closely inspecting the relation between the rate of heat generation and dissipation to anticipate the TR at an early stage. From the proposed criteria, three alarming temperatures prior to TR are identified, such as the safe temperature limit TE (an intersection between heat generation curve and heat removal line), the maximum temperature limit TM (where second derivative of heat generation is zero), and the low temperature TC from the Semenov theory. For a safer battery operation, both the low and upper limit temperatures have to remain below the safety zone, i.e. TM < TE with TC < TE. The criteria are validated by implementing them on the ultrahigh capacity LIBs, which are subjected to the thermal abuse, wherein the rate of heat generation was determined from calorimetry. The state TM < TE indicates the first precursor to TR where a controlled measure can be taken to prevent the runaway. However, TE ≤ TM regarded as the critical state during which a self-sustaining reaction involving delithiated nickel-rich cathode, intercalated anode, and dissociated electrolyte progresses, resulting in an irreversible TR in the system. The validity of the proposed criteria is demonstrated, while additional work is considered in a broad class of batteries subjected to thermal abuse conditions for establishing a safety margin of operation.
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<div>Thermal runaway of lithium (Li)-ion batteries is a serious concern for engineers developing battery packs for electric vehicles, energy storage, and various other applications due to the serious consequences associated with such an event. Understanding the causes of the onset and subsequent propagation of the thermal runaway phenomenon is an area of active research. It is well known that the thermal runaway phenomenon is triggered when the heat generation rate by chemical reactions within a cell exceeds the heat dissipation rate. Thermal runaway is usually initiated in one or a group of cells due to thermal, mechanical, and electrical abuse such as elevated temperature, crushing, nail penetration, or overcharging. The rate of propagation of thermal runaway to other cells in the battery pack depends on the pack design and thermal management system. Estimating the thermal runaway propagation rate is crucial for engineering safe battery packs and for developing safety testing protocols. Since experimentally evaluating different pack designs and thermal management strategies is both expensive and time consuming, physics-based models play a vital role in the engineering of safe battery packs. In this article, we present all the necessary background information needed for developing accurate thermal runaway models based on predictive chemistry. A framework that accommodates different types of chemical reactions that need to be modeled, such as solid electrolyte interphase (SEI) layer formation and decomposition, anode-solvent and cathode-solvent interactions, electrolyte decomposition, and separator melting, is developed. Additionally, the combustion of vent gas is also modeled. A validated chemistry model is used to develop a module-level model consisting of networks of pouch cells, flow, thermal, and control components, which is then used to study the thermal runaway propagation at different coolant flow rates.</div>
Thermal Runaway
Separator (oil production)
Heat Generation
Thermal engineering
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Lithium-ion batteries (LIB) have found a wide range of applications in many consumer products in the last 25 years. The United States Navy and Marine Corps have various applications using LIB, and safe battery technologies are critically needed. While many consumer applications typically utilize smaller high capacity cells, military applications can utilize specialty large-format (>30 Ah) cells in their LIB packs. One of the most important safety considerations for LIB cells is their thermal stability under various abuses such as exposure to heat, nail penetration, external short circuit, crushing, and so on. Several exothermic reactions can occur as the inner cell temperature increases, and if the heat generation is larger than the dissipated heat to the surroundings, this leads to heat accumulation in the cell and acceleration of the chemical reactions, which can then lead to a thermal runaway. To understand and control thermal runaway, many researchers have formulated complex mathematical models and built experimental set-ups for investigating the phenomenon in detail. However, most of the studies focused on the effect of thermal runaway event, while no detailed numerical analysis on the vaporization of the electrolyte and the correlation of electrochemical reactions with overcharge in large-format LIB has been reported yet. So this study reports the recently developed electrochemical-thermal coupled gas generation and overcharge-to-thermal-runaway model for a large-format lithium-ion battery tested at NSWCCD using COMSOL software.
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Overcharge
Heat Generation
Exothermic reaction
Nuclear transmutation
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Thermal Runaway
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