Potassium-Ion batteries: sustainable strategies

近年来，由于交通运输领域的需求不断增长，锂离子电池(LiB)作为高能量存储解决方案的首选，经历了巨大的增长。电池存储的扩大伴随着对锂、钴或镍等元素在可预见的未来资源短缺的担忧。后继的技术，如钠或钾离子电池(NiB和KiB)，应该通过使用更丰富的资源来避免这个问题。到目前为止，这些技术存在可逆性差和电池寿命短的问题。一个成功的KiB开发不仅要关注单个组件，而且要关注整个系统，允许相互调整单元组件。因此，该项目旨在了解关键电池组件的基本方面，即阴极、阳极和电解液，以及它们在KiB中的相互作用。这将通过开发新的活性材料，如六氰基金属酸盐和氧代(氟化物)磷酸盐，硬碳，并研究它们在电极-电解液-界面上的相互作用来实现。例如，氧代(氟化物)磷酸盐被认为是一类很有前途的金属离子电池超快阴极，它在高电流密度下表现出稳定的循环，由于体积变化很小而具有高的机械稳定性，并且在高电化学势下工作。然而，当超过电解液的稳定窗口时，后者就会变成一个问题。因此，需要新颖和创新的材料策略来实现电极界面和电解液之间的兼容性，这可以在潜在的更低成本和更大的可持续性下将能量密度提高到接近普通LiB的水平。通过对LiB的研究，可以找到潜在的解决方案，例如通过选择电正性较低的过渡金属来降低阴极氧化还原电位，或者开发合适的电解液添加剂来促进稳定的界面形成。然而，在这方面，KiB的研究仍处于起步阶段。尽管与LIB有相似之处，但这两种技术之间的知识转移必须得到严格的审查。同时，应最有效地利用现有的协同作用，以解决目前阻碍KiB技术的重大基础性科学挑战。因此，本项目设想同时开发这三个关键电池组件。阳极和阴极之间的联系是电解液和电极-电解液界面的分析，以推动KiB研究在所有主要方向上向前发展。该项目为期三年，将由三个团队制定：Skoltech(俄罗斯)、IFW Dresden和KIT(均在德国)。为了促进团队之间的密切合作，特别是学士/硕士和博士生之间的密切合作，计划在同步加速器源进行联合光束时间以及持续的样品交换。这些团队拥有执行该项目所需的所有基础设施。

Li-ion batteries (LIB) as high-energy storage solution of choice experience a tremendous growth in recent years owing to increasing demand in the transport sector. The expansion of battery storage is accompanied with the concern of resource shortage in the foreseeable future for elements such as Li, Co or Ni. Successor technologies like Na- or K-ion batteries (NIB and KIB) ought to avoid this problem by use of more abundant resources. Up until now, these technologies suffer from poor reversibility and short battery life. A successful development of KIB has to focus not only on individual components but on the entire system allowing mutual adjustment of the cell components. Hence, this project aims at understanding of fundamental aspects of the key battery components, i.e. cathodes, anodes and electrolytes, and their mutual interactions in a KIB. This will be achieved by developing novel active materials, such as hexacyanometallates and oxo(fluoride)phosphates, hard carbons and studying their interactions at the electrode-electrolyte-interface. For example, oxo(fluoride)phosphates are considered nowadays a class of promising superfast cathodes for metal-ion batteries, that show stable cycling at high current densities, high mechanical stability due to a minor volume change, and operate at high electrochemical potentials. That latter, however, turns into a problem when the stability window of the electrolyte is exceeded. Therefore, novel and innovative material strategies are required to enable compatibility between the electrode interface and electrolyte, which can lift the energy density closer to the levels of common LIB at potentially lower cost and greater sustainability. Potential solutions are available through the research on LIB, e.g. lowering of the cathode redox potential by choice of less electropositive transition metals or developing suitable electrolyte additives that promote stable interface formation. However, in this respect KIB research is still at its beginning. Despite parallels to LIB, knowledge transfer between the two technologies has to be critically reviewed. At the same time, existing synergies shall be used most effectively in order to solve the major fundamental scientific challenges that currently hamper the KIB technology. Therefore, simultaneous development of the three key battery components is envisaged in this project. The link between anode and cathode activities is the electrolyte and the analysis of electrode-electrolyte interfaces in order to move KIB research forward in all major directions. The project is intended for three years and will be worked out by three teams: Skoltech (Russia), IFW Dresden and KIT (both in Germany). In order to promote a close collaboration between the teams, in particular Bachelor/Master and PhD students, joint beamtimes at synchrotron sources as well as constant sample exchange are planned. The teams possess all necessary infrastructure to perform this project.