Mechanistic Investigation of Metal Sulfide Electrodes for High-Energy Non-Aqueous Anion Batteries

目前锂离子电池的能量密度已经接近天花板；然而，续航里程焦虑仍然阻碍着电动汽车的市场增长。此外，目前的高能电池依赖价格昂贵的钴和镍元素，这些元素的地球丰度很低，在国内钴的储量也不是很多。因此，制造这种电池对于将很大比例的汽车电气化以缓解气候变化来说是不可持续的。目前的高能电池使用锂离子(正电荷离子)作为电荷载体，以补偿金属氧化物在充放电过程中的电荷中性。从理论上讲，电池电极的运行可以利用负离子(负电荷离子)作为电荷载体，但这一研究方向还没有得到很大的重视，特别是要实现高能量密度。该项目将研究国内储量丰富的铜和硫等地球丰富的材料。这一基础研究项目将以轻(低分子)阴离子为载流子，与廉价金属硫化物的氧化还原反应耦合为电极，填补这一知识空白。该项目将建立在转换电极反应中阴离子的可逆储存的初步发现的基础上。此外，PI将研究非水电解液，以促进新的电池反应。作为研究的一部分，该项目将为服务不足的本科生和高中生提供高质量的研究机会。该项目旨在阐明高能正极在掺有锂盐的Cu2S和由铜盐、CuA2和硫组成的复合材料之间可逆转化的运行机理。靶向Cu2S是一种天然矿物，由于Cu2S既是电子的导体，又是铜离子的导体，因此是一种很有前途的负离子承载正极材料。该项目将产生关于三个离子在看似复杂的转化反应中的相互作用和传输的知识。在Cu2S-LiA和CuA-2-S的电化学反应中，有四个电子转移。锂离子从不与铜或硫的氧化还原中心相互作用，而只与A-阴离子相互作用；然而，铜离子和阴离子在Cu2S、CuS和CuA2的氧化还原中心之间转移。这种电极设计实现了器件电荷补偿和电极电荷补偿的解耦。该项目的成果将是固态离子和电化学系统的新成员。与锂S电池的硫磺正极不同，铜离子的存在消除了多硫化物的形成，因为铜离子与硫化物之间有很强的结合。Cu2S和CuS的不溶性质允许对不同荷电状态下的固体电极进行详细的结构和动力学性质的表征。该项目将描述影响电极利用率、动力学特性和可逆性的相互关系。该项目将建立阴离子电荷载体和电解液的协同选择规则，以促进拟议的电池化学性能。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。

The energy density of the current Li-ion batteries has nearly reached their ceiling; however, driving range anxiety still hinders the market growth of electric vehicles. In addition, the current high-energy batteries rely on expensive elements of cobalt and nickel with poor earth abundance and in cobalt’s case not plentiful domestically. Therefore, manufacturing such batteries is not sustainable for transforming a large percentage of vehicles to be electrified to mitigate climate change. Current high-energy batteries employ Li-ions (positive charged ions) as the charge carrier to compensate for the charge neutrality of metal oxides during charge and discharge. In theory, the operation of battery electrodes can use anions (negative charged ions) as charge carriers, but this research direction has yet to receive much attention, particularly to achieve high energy density. This project will study earth abundant materials that are plentiful domestically such as copper and sulfur. This fundamental research project will fill the knowledge gap by employing light (low molecular weight) anions as the charge carriers to couple with the redox reactions of inexpensive metal sulfides as the electrode. The project will build upon the preliminary findings of the reversible storage of anions in conversion electrode reactions. In addition, the PI will study nonaqueous electrolytes to facilitate the new battery reactions. As a part of the research, the project will provide high-quality research opportunities for underserved undergraduate and high school students. The project aims to elucidate the operation mechanism of a high-energy cathode converted reversibly between Cu2S mixed with a lithium salt and the composite comprising a cupric salt, CuA2, and sulfur. The targeted Cu2S, as a natural mineral, is a promising anion-hosting cathode material because Cu2S is a conductor of both electrons and copper ions. The project will generate knowledge about the interplays and transport of three ions in a seemingly complicated conversion reaction. In the electrochemical conversion reactions between Cu2S+LiA and CuA2+S, four electrons are transferred. Li-ions never interact with redox centers of copper or sulfur but only with A-anion; however, copper ions and anions transport between the redox centers of Cu2S, CuS, and CuA2. This electrode design causes the decoupling of device charge compensation and electrode charge compensation. The outcomes of this project will be a new addition to solid-state ionics and electrochemical systems. Unlike that of the sulfur cathode in Li-S batteries, the presence of copper ions eliminates polysulfide formation due to the strong binding between copper ions and sulfides. The insoluble nature of Cu2S and CuS allows the characterization of the solid electrode at different state of charge on detailed structural and kinetic properties. The project will delineate the correlations that affect the utilization, the kinetic properties, and the reversibility of the electrodes. The project will establish synergistic selection rules of anion charge carriers and electrolytes to promote the proposed battery chemistry performance.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.