CAREER: Understanding Spontaneous Internal Short Circuit Caused Thermal Runaway of Lithium-ion Batteries through In Situ Diagnosis

预计到2030年，电动汽车(EVS)将占美国乘用车销量的一半以上。然而，代价高昂的电池起火已成为蓬勃发展的电动汽车行业的一个关键挑战。这一挑战最令人担忧的是，在某些情况下，电池在车辆不使用时突然起火。这些火灾被归因于锂离子电池的内部短路，这也是涉及智能手机、笔记本电脑和网格级储能等许多其他应用的电池起火的主要原因。这项职业研究试图了解锂离子电池内部短路是如何形成、演变并突然导致热失控事件(以及潜在的火灾)的。这项研究的洞察力将促进对电化学能源系统能量故障的理解，并为电动汽车和许多其他应用开发更安全的电池。综合教育任务包括组织一系列关于最先进的储能技术的研讨会，创建一个储能俱乐部，开发一门关于电池基础的新课程，以及指导本科生进行锂电池研究和高级设计项目。这些任务的目的是培养本科生，以满足美国东南部蓬勃发展的电动汽车行业对劳动力发展日益增长的需求。综合外展活动包括在当地高中组织实践工作坊，让大多数低收入和少数族裔学生专注于电池基础知识和电池相关新兴产业的机会，在亨茨维尔的阿拉巴马大学(University Of Alabama)体验夏令营计划中创建和教授电池模块(成为一名工程学学生)，以及在当地的STEM活动中展示储能研究。这些活动将吸引当地的K-12学生进入STEM领域，为他们在电动汽车行业和其他新兴的电池驱动行业的机会做好准备。本研究旨在通过现场诊断了解内部短路(ISC)是如何形成、演变并引发锂离子电池热失控的。中心假设是，由ISC引起的热失控的阈值是一个临界能量屏障，而不是一个临界温度。为了验证这一假设，该项目将实现三个目标：1.通过原位测量包括ISC电流、温度和发热量在内的关键参数来确定ISC引起的热失控阈值；2.通过原位成像和电化学表征了解ISC的形成和演化；3.了解电流引导和自冷却对ISC行为和热失控风险的影响。第一个目标将弥合传统的异地实验和数值模拟之间的差距，以确定和确定由ISC引起的热失控的可靠阈值。第二个目标将揭示ISC的机制和行为，以促进对这一高度局域和瞬时的热-电化学耦合现象的理解。第三个目标将确定阈值能量，并为工业工程师开发未来的热失控保护策略和技术提供基础。总之，这项研究将提供对ISC导致的锂离子电池热失控的洞察，并帮助确保电池的安全，这些电池对指数级增长的电动汽车行业的成功至关重要。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Electric vehicles (EVs) are expected to account for more than half of passenger cars sold in the U.S. by 2030. However, costly battery fires have become a critical challenge for the burgeoning EV industry. What makes this challenge most concerning is that, in some cases, the batteries suddenly caught fire when the vehicles were not in use. These fires have been attributed to the internal short circuit of lithium-ion batteries, which is also a major cause of battery fires involving many other applications such as smart phones, laptops, and grid-scale energy storage. This CAREER research seeks to understand how an internal short circuit forms, evolves, and suddenly causes a thermal runaway event (and potentially a fire) in lithium-ion batteries. Insights from the research will advance the understanding of energetic failures of electrochemical energy systems and the development of safer batteries for EVs and many other applications. The integrated educational tasks include organizing a series of seminars on state-of-the-art energy storage technologies, creating an energy-storage club, developing a new course on battery basics, and mentoring undergraduate students in lithium-battery research and senior design projects. These tasks will be performed to train undergraduate students to meet the growing demand of workforce development for the booming EV industry in the Southeastern U.S. The integrated outreach activities include organizing hands-on workshops in local high schools with majority low-income and minority students focusing on battery basics and opportunities of battery-related emerging industries, creating and teaching a module on batteries in the BEST (Be an Engineering STudent) Experience summer camp program at the University of Alabama in Huntsville, and showcasing energy storage research at local STEM events. These activities will attract local K-12 students to STEM fields, preparing them for opportunities in the EV industry and other emerging battery-enabled industries.This research seeks to understand how an internal short circuit (ISC) forms, evolves, and triggers thermal runaway of lithium-ion battery cells through in situ diagnosis. The central hypothesis is that the threshold for thermal runaway due to ISC is a critical energy barrier, not a critical temperature. To test this hypothesis, the project will achieve three objectives: 1. determine the threshold of thermal runaway caused by ISC through in situ measurement of critical parameters, including ISC current, temperature, and heat generation; 2. understand the formation and evolution of ISC through in situ imaging and electrochemical characterization; and 3. understand the effects of current-guiding and self-cooling on ISC behaviors and risk of thermal runaway. The first objective will bridge the gap between conventional ex situ experiments and numerical modeling to identify and determine a reliable threshold of thermal runaway caused by ISC. The second objective will reveal the mechanisms and behaviors of ISC to advance the understanding of this highly localized and transient thermal-electrochemical-coupled phenomenon. The third objective will confirm the threshold energy and provide a basis for industrial engineers to develop future thermal runaway protection strategies and techniques. Together, the research will provide insight into ISC-caused thermal runaway of lithium-ion batteries and help ensure the safety of batteries that are critical to the success of the exponentially growing EV industry.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.