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储能的首选。然而，它们的表现仍然没有达到推动交通运输从以化石燃料为基础的有意义转变所需的指标。具体地说，单位体积储存的能量或能量密度太低。提高能量密度的挑战源于故障率和断电率的同时增加。这种权衡是由阴极的限制驱动的，但必须精确定义其微观化学结构和机制，才能产生有效的解决方案。伊利诺伊大学芝加哥分校的研究人员试图通过一系列基于X射线测绘的现有和新兴技术，揭示纳米和微米级的化学变化如何决定现代锂离子正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以空间精确的化学知识为基础的新的工程原理来推动电化学工程和电池制造，这将指导随后的新突破。为了最大限度地提高和加快对当前技术的影响，这项研究集中在基本问题上，但应用于工业感兴趣的正极材料。这些活动与通过本科生和高中生实习、在当地小学促进科学和关于电化学的暑期讲习班来培训未来几代科学家交织在一起。这些活动将特别关注芝加哥拉美裔社区的成员，他们在STEM中的代表性传统上较低。锂离子电池能量密度的限制来自阴极，主要是因为领先的候选家族层状氧化物目前的表现没有达到理论极限。这种限制从根本上是由产生电荷流动的潜在电化学反应支撑的，而电荷流动受到不完全可逆性和降低活性的竞争过程的阻碍。这项研究的目的是将宏观电池性能与当今所追求的复杂建筑中的局部化学成分和存储反应的进展相关联。通常，这些关联是在整体电极的集合平均值和极少数孤立粒子的水平上建立的。但这些尺度与目前设计多功能异质结构以提高阴极性能的努力是不匹配的，其中关键是确定不同元素的纳米级分布及其在许多粒子内部和之间的一致性。它们也不匹配，以准确地定位竞争阴极以极端速度和广泛循环失败的微观根源，这关键取决于相对于完整架构的特定微尺度活动。这项研究将使用一套X射线成像和测绘技术来量化相关长度尺度上的临界异质性，包括在3D和电池运行期间。在电池研究中具有广泛适用性的新颖分析方法将是该项目遗留下来的一部分。新的洞察力将提供可行的工程投入，以克服下一代锂离子电池在转换能量密度方面的持久阴极障碍。该奖项反映了NSF的法定使命，并已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。

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.