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

硅和硫具有理论容量高、成本低、毒性小等优点，是非常有前景的锂电池活性材料。然而，由于其可循环性不足，它们的商业使用受到阻碍。尽管粘结剂在总电极材料中所占比例很小(通常低于10wt.%)，但粘结剂在电极性能中起着关键作用，因为它确保了电极成分(活性材料和导电剂)的粘附性，以及它们在电极制备过程和循环条件下与集电体的粘附性。值得注意的是，在硅和S电极的情况下，粘结剂应该缓解与分别形成LixSi和LixS相关的非常大的电极体积变化，而不会出现明显的分层、破裂和坍塌，这些分层、破裂和坍塌会导致活性物质的电子布线损失，从而导致大容量随着循环而衰退。在本研究计划中，将评估配位化学为应对这些挑战提供的机会。更准确地说，配位键的特性，特别是它们的可调性和动态性，将为开发先进的粘结剂提供替代途径，这些粘结剂可能显著提高锂离子电池硅基负极和锂金属电池S基正极的电化学性能。考虑到可用配位基序的多样性，显然存在大幅调整粘结剂的性质和扩大先进电池技术的可获得的环保粘结剂的范围的空间。特别是，极性粘结剂中存在的许多官能团与金属阳离子结合的能力将被研究，以诱导粘结剂聚合物链的离子交联。这样的配位网络容易变形，但也很容易恢复其初始状态，最终在电极中诱导自愈性能。此外，交联粘结剂可能有助于在硅活性材料表面形成更稳定的固体电解质界面层，或者可能有利于电解质可溶的多硫化物中间体在S阴极中的保留。为了将粘结剂的配位状态与硅基和S基电池电极的形态、机械和电化学性能相关联，该研究计划的重要部分将致力于开发一大批互补的原位/操作面表征方法。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，并将为培训加拿大开发绿色能源储存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.