Towards the Rational Design of Ni & Co free Chalcogen Anion Redox Cathode Materials

全球能源需求和减少对化石燃料依赖的愿望加强了对大规模能源储存能力的研究。尽管对锂离子电池技术进行了多年的活跃研究，但目前的电池材料仍然严重依赖于传统的过渡金属正极材料。这些阴极材料的容量有限，地缘政治问题引发了对其持续供应的担忧。最近，研究人员一直在探索所谓的富锂阴离子氧化还原阴极化学，即过渡金属和阴离子都参与电化学氧化还原反应，从而产生显著更高的储能能力。尽管提供了高容量，但这些富锂阴极存在根本性的稳定性问题。该项目旨在获得设计下一代不含镍和钴金属的低成本和高容量正极材料所需的基本见解。对于更广泛的影响，将成立一个具体的外展任务，为密歇根州底特律周围社区大学的学生提供研究经验，那里的大多数学生来自代表性不足的群体。随着过渡金属基层状氧化物的常规阳离子氧化还原达到理论容量极限，富锂阴离子氧化还原阴极化学应运而生。虽然阴离子和阳离子的结合氧化还原使其具有更高的储能能力，但阴极存在电压衰减、大电压滞后和不可逆的氧释放，这一现象神秘地源于氧配体本身的阴离子氧化还原活性。该项目的技术目标是通过使用商业上可行的金属阳离子和电负性较低的硫族配体(硫化物和硒)来调节金属-配体共价性，构建富锂阴离子氧化还原阴极的结构框架。提出的研究是基于这样的假设，即通过使富锂硫化物中金属阳离子d带接近硫族阴离子p带，从而利用高度可逆的多电子氧化还原化学，可以实现金属-配体共价性的改善。该项目的成功成果是阐明了硫氧阴离子氧化还原化合物的锂(放电)-脱硫化(电荷)动力学以及阴离子氧化还原在不同的金属d带和配体p带环境中引起的结构转变的核心理解。因此，这项研究旨在定义硫化物氧化还原化学的新视角，以促进对下一代阴极材料的基本理解。该奖项反映了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。

Global energy demands and a desire for decreased reliance on fossil fuels have intensified research toward large-scale energy storage capabilities. Even though many years of active research in Li-ion battery technologies, the current battery materials still rely heavily on conventional transition-metal cathode materials. These cathode materials have limited capacity, and geopolitical issues raise concerns over their continued availability. Recently, researchers have been exploring the so-called “Lithium-rich anion redox” cathode chemistry, where both transition metals and anions participate in the electrochemical redox reactions, resulting in significantly higher energy storage capability. Despite delivering high capacity, these Li-rich cathodes suffer from fundamental stability issues. This project seeks to gain the fundamental insights necessary for the design of next-generation low-cost and high-capacity cathode materials that are free from Nickel and Cobalt metals. For broader impacts, a specific outreach mission will be formed to provide research experience to the students in community colleges around Detroit, MI where the majority of students are from underrepresented groups. Li-rich anion-redox cathode chemistry is emerging as conventional cationic-redox of transition metal-based layered oxides are reaching their theoretical capacity limit. Though the combined redox of both anion and cation towards higher energy storage capability, the cathodes suffer from voltage fade, large voltage hysteresis, and irreversible oxygen release, which originate mysteriously from the anionic redox activity of oxygen ligand itself. The technical objective of this project is to construct a structural framework for Li-rich anion redox cathodes by tuning metal-ligand covalency using commercially viable metal-cations and less electronegative chalcogen ligands (sulfides and selenides). The proposed research is based on the hypothesis that the improved metal-ligand covalency can be achieved by bringing metal cation d-band close to chalcogen anion p-band in lithium-rich chalcogenide thereby utilizing highly reversible multi-electron redox chemistry. The successful outcome of the project is to elucidate the core understanding of lithiation (discharge)-delithiation (charge) kinetics in chalcogen anion redox compounds and anion redox induced structural transformation in various metal d-band and ligand p-band environments. Thus, this research aims to define fresh perspectives on chalcogen redox chemistry to advance the fundamental understanding of the next-generation cathode materials.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.