Defining Critical Heterogeneity in Cathode Architectures for Li-ion Batteries with High Energy Density

锂离子电池是便携式设备和电动汽车清洁高效能源存储的首选。然而，它们的表现仍达不到推动以化石燃料为基础的交通方式发生重大转变所需的指标。具体来说，每单位体积存储的能量或能量密度太低。增加能量密度的挑战源于同时增加的故障率和功率损耗。这种权衡是由阴极的限制所驱动的，但它的微观化学结构和机制必须精确定义才能产生有效的解决方案。通过一套现有的和新兴的基于x射线测绘的技术，伊利诺伊大学芝加哥分校的研究人员试图揭示纳米和微观尺度上的化学变化（称为异质性）如何决定现代锂离子阴极在高能量密度电池中实现长寿命的能力。这项研究将通过建立基于空间精确化学知识的新工程原理来推进电化学工程和电池制造，这将随后指导新的突破。为了最大限度地提高和加快对当前技术的影响，本研究侧重于基本问题，但应用于工业感兴趣的阴极材料。通过为本科生和高中生提供实习机会，在当地小学推广科学，以及举办一个关于电化学的夏季讲习班，这些活动与培养未来几代科学家交织在一起。这些活动将特别关注芝加哥的西班牙裔社区成员，他们传统上在STEM领域的代表性不足。锂离子电池能量密度的限制来自于正极，主要是因为层状氧化物，主要的候选家族，目前还没有达到理论极限。这种限制从根本上是由产生电荷流的潜在电化学反应所支撑的，这种反应受到不完全可逆性和降低活性的竞争过程的阻碍。本研究的目的是将宏观电池性能与当前复杂结构中局部化学成分和存储反应的进展联系起来。通常，这些相关性是建立在整体电极的系综平均值和极少数孤立粒子的水平上的。但这些尺度与当前设计多功能异质结构以提高阴极性能的趋势不匹配，在这种情况下，确定不同元素的纳米尺度分布及其在许多颗粒内部和之间的一致性至关重要。它们也不匹配，以查明竞争阴极在极端速率和广泛循环下失效的微观起源，这主要取决于相对于完整结构的特定微观尺度活动。这项研究将通过一系列x射线成像和测绘技术，包括3D和电池运行期间，量化相关长度尺度上的关键异质性。在电池研究中广泛适用的新颖分析方法将是该项目遗产的一部分。这一新颖的见解将提供可行的工程投入，以克服长期存在的阴极障碍，实现下一代锂离子电池能量密度的转变。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Lithium-ion batteries are the premier choice for clean and efficient energy storage for portable devices and electric vehicles. However, their performance still falls short of the metrics required to drive a meaningful shift away from transportation based on fossil fuels. Specifically, the energy stored per unit of volume, or energy density, is too low. Challenges in increasing energy density stem from the concurrent increase in the rate of failure and loss of power. This trade-off is driven by limitations at the cathode, but its microscopic chemical structure and mechanisms must be precisely defined for effective solutions to arise. Through a suite of existing and emerging techniques based on X-ray mapping, researchers at the University of Illinois at Chicago seek to reveal how chemical variations, called heterogeneity, at the nano and microscale determine the ability of modern lithium-ion cathodes to achieve long lifetimes in batteries with high energy density. This research will advance electrochemical engineering and battery manufacturing by establishing novel engineering principles informed by spatially precise chemical knowledge, which will subsequently guide new breakthroughs. To maximize and expedite impact in current technology, this research focuses on fundamental questions, yet applied to cathode materials of interest to industry. The activities are intertwined with the training of future generations of scientists through internships for undergraduate and high school students, promotion of science in local elementary schools and a Summer workshop on electrochemistry. These activities will have a special focus on members of Chicago's Hispanic communities, which are traditionally underrepresented in STEM.Limitations in the energy density of Li-ion batteries stem from the cathode, mainly because layered oxides, the leading family of candidates, do not currently perform at their theoretical limit. This limitation is fundamentally underpinned by the underlying electrochemical reactions that generate flow of electrical charge, which are hindered by incomplete reversibility and competing processes that degrade activity. The objective of this research is to correlate macroscopic battery performance to local chemical composition and progress of the storage reactions in the complex architectures pursued today. Conventionally, these correlations are established at the ensemble averages of the bulk electrode and at the level of very few isolated particles. But these scales are mismatched to the current push to design multifunctional heterostructures to enhance cathode performance, where it is critical to ascertain the nanoscale distribution of different elements and its consistency both within and between many particles. They are also mismatched to pinpoint the microscopic origin of the failure of competitive cathodes at extreme rates and extensive cycling, which critically depends on the specific microscale activity relative to the complete architecture. This research will quantify critical heterogeneity at relevant length scales with a suite of techniques of X-ray imaging and mapping, including in 3D and during battery operation. Novel analytical methods of broad applicability in battery research will be part of the legacy of this project. The novel insight will provide actionable engineering inputs to overcome enduring cathode roadblocks toward transformational energy density in next-generation Li-ion batteries.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.