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

硅和硫具有理论容量大、成本低、毒性低等特点，是极具发展前景的锂电池活性材料。然而，它们的商业用途受到其不充分的可循环性的阻碍。尽管粘合剂在总电极材料中所占的比例很小（通常小于10 wt.%），但它在电极性能中起着关键作用，因为它确保了电极成分（活性物质和导电剂）的内聚性，以及它们在电极制备和循环条件下与集流器的粘附性。值得注意的是，在Si和S电极的情况下，粘合剂应减轻LixSi和LixS各自形成相关的非常大的电极体积变化，而不会出现明显的分层、开裂和坍塌，从而导致活性质量的电子布线损失，从而导致大容量随循环衰减。在本研究计划中，将评估配位化学为解决这些挑战所提供的机会。更准确地说，配位键的特性，特别是它们的可调性和动态特性，将为开发先进的粘合剂提供替代途径，这些粘合剂可能会显著提高锂离子电池的硅基负极和锂金属电池的基基正极的电化学性能。考虑到各种可用的配位基序，显然有空间大幅调节粘合剂的特性，并扩大可用于先进电池技术的生态友好粘合剂的范围。特别是，极性粘合剂中存在的许多官能团与金属阳离子结合的能力，以诱导粘合剂聚合物链的离子交联，将被研究。这样的配位网络容易变形，但也容易恢复其初始状态，最终在电极中诱导自愈特性。此外，交联结合剂可能有助于在Si活性材料表面形成更稳定的固体电解质界面（SEI）层，或者可能有利于在S阴极中保留电解质可溶性多硫化物中间体。为了将粘结剂的配位状态与Si和S基电池电极的形态、力学和电化学性能联系起来，研究计划的一个重要部分将致力于开发大量互补的原位/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，并将为培养加拿大发展绿色储能技术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.