Addressing the challenges of high-capacity electrodes for lithium batteries through coordination chemistry

硅和硫由于其高理论容量、低成本和低毒性，是非常有前途的锂电池活性材料。然而，它们的商业用途受到其不足的可循环性的阻碍。尽管其在总电极材料中的比例很小（通常小于10重量%），粘合剂在电极性能中起关键作用，因为它确保电极组分（活性材料和导电剂）的内聚以及它们在电极制备期间和循环条件下对集电器的粘附。值得注意的是，在Si和S电极的情况下，粘合剂应减轻与LixSi和LixS的相应形成相关的非常大的电极体积变化，而没有显著的分层、破裂和塌陷，这导致活性物质的电子布线损失，从而导致随着循环的大容量衰减。 在这项研究计划中，将评估配位化学为应对这些挑战所提供的机会。更确切地说，将利用配位键的特性，特别是它们的可调谐性和动态特性，为开发可能显着改善Li离子电池的Si基负极和Li金属电池的S基正极的电化学性能的先进粘合剂提供替代途径。考虑到可用的配位基序的多样性，显然存在大幅调节粘合剂的性质和扩大用于先进电池技术的可获得的生态友好粘合剂的范围的空间。特别地，将研究极性粘合剂中存在的许多官能团与金属阳离子结合以诱导粘合剂聚合物链的离子交联的能力。这种配位网络易于变形，但也易于恢复其初始状态，最终在电极中诱导自修复特性。另外，交联的粘合剂可以有助于在Si活性材料的表面处形成更稳定的固体电解质界面（SEI）层，或者可以有利于电解质可溶的多硫化物中间体保留在S阴极中。为了将粘合剂的配位状态与Si和S基电池电极的形态、机械和电化学性能相关联，研究计划的重要部分将致力于开发一个大型的互补原位/操作表征方法。拟议的研究计划将加强加拿大在电池技术领域的专业知识，并将为培养加拿大开发绿色储能技术所急需的高素质人才提供肥沃的土壤。

Due to their high theoretical capacities, low cost and low toxicity, silicon and sulfur are very promising active materials for lithium batteries. However, their commercial use is hampered by their insufficient cyclability. Despite its small proportion of the total electrode material (usually less than 10 wt.%), the binder plays a key role in the electrode performance since it ensures the cohesion of the electrode constituents (active material and conducting agent), as well as their adhesion to the current collector, both during the electrode preparation and under cycling conditions. Notably, in the case of Si and S electrodes, the binder should mitigate the very large electrode volume variation associated with the respective formation of LixSi and LixS without significant delamination, cracking and collapsing, which lead to the electronic wiring loss of the active mass, resulting in a large capacity fading with cycling.  In this research program, the opportunities offered by coordination chemistry to tackle these challenges will be evaluated. More precisely, the characteristics of the coordination bonds, notably their tunability and dynamic character, will be exploited to offer alternative paths for developing advanced binders likely to significantly improve the electrochemical performance of Si-based negative electrodes for Li-ion batteries and S-based positive electrodes for Li metal batteries. Considering the variety of coordination motifs available, there is clearly room for drastically modulating the properties of the binder and for enlarging the scope of accessible ecofriendly binders for advanced battery technologies. Especially, the ability of many functional groups present in polar binders to bind to metallic cations, in order to induce an ionic crosslinking of the binder polymer chains, will be studied. Such a coordination network is prone to deform, but also to recover its initial state easily, eventually inducing self-healing properties in the electrode. Additionally, cross-linked binders may assist in the formation of a more stable solid electrolyte interphase (SEI) layer at the surface of the Si active material or may favour the retention of the electrolyte-soluble polysulfide intermediates in the S cathode. In order to correlate the coordination state of the binder to the morphological, mechanical and electrochemical properties of the Si and S based battery electrodes, a significant part of the research program will be devoted to the development of a large panel of complementary in-situ/operando characterization methods. The proposed research program will strengthen Canada's expertise in the field of battery technologies and will provide a fertile ground for the training of highly qualified personnel urgently needed for developing green energy storage technologies in Canada.