Photo-responsive electrode materials and multifunctional electrolytes for Li-ion batteries for multi-modal energy harvesting

自持式电化学储能系统对于缓解能源向未来可持续社会过渡的障碍至关重要。锂离子二次电池是一种能量密度高、倍率高、可靠性高的储能设备，被广泛应用。然而，锂离子电池的自主性是有限的，因为需要外部负载来逆转负责功率提取(放电)的电化学反应。在这种背景下，基于具有光电和电化学活性的双模电极的光充电电池代表着同时收集和存储太阳能的突破性能源技术。在光和暗条件下进行的电化学研究表明，光生空穴促进了锂离子从正极材料中的提取，从而使电池能够完全通过光照明进行充电。在这一双边项目中，将研究新的电极材料(德国团队)和光稳定性电解液(日本团队)，以开发可直接用可见光充电的可光充电锂离子电池。传统的锂离子电池通过液体电解液在阴极和阳极之间进行可逆的锂离子转移。在充电过程中，从阴极中提取的Li+(脱嵌)通过电解液迁移到阳极中。在可光充电的锂离子电池中，电极材料的光氧化促进了锂离子的向外移动(脱硫化)，但光诱导锂离子从电极上提取锂离子的机理(例如，光电极带隙和电池电压的相互依赖)还不是很清楚，将成为本提议的一个主要方面。虽然有一些关于光开关电极材料的报道，但还没有关于液体电解液对光致Li+萃取的影响的报道。该项目的创新之处在于其多学科方法，将日本团队在电解液开发和溶液/界面电化学方面的专业知识(PI：Y.Y.Yamada教授)与德国团队(PI：S.Mathur教授)的材料开发和集成专业知识相结合，以实现光电池。要最大限度地提高光充电效率，需要调整电极材料和电解液的功能行为，以加速Li+的提取，防止光激e-/h+的复合，这是仅基于电极材料的传统方法无法实现的。这一应用的具体研究目标包括(I)光活性电极的制造(Ii)电解液的制备和电化学评估(Iii)光照下界面电极-电解液相互作用的操作研究和(Iv)全电池配置的验证。

Self-sustained electrochemical energy storage systems are crucial to alleviate the barriers of energy transition toward future sustainable society. Lithium-ion rechargeable batteries represent a class of energy storage devices that are widely deployed due to high energy density, rate capability, and reliability. However, the autonomy of Li-ion batteries is limited due to the necessity of an external load that is required to reverse the electrochemical reactions responsible for power extraction (discharge). In this context, photochargeable batteries based on dual-mode electrode exhibiting photo- and electrochemical activities represent breakthrough energy technologies to simultaneously harvest and store solar energy. Electrochemical studies performed in light and under dark conditions demonstrate that photogenerated holes promotes the extraction of Li+ ions from the cathode material, which enables batteries solely rechargeable by light illumination. Within this bilateral project, new electrode materials (German Team) and photostable electrolytes (Japanese Team) will be studied to develop photo-rechargeable lithium-ion batteries that can be directly charged by visible light. Conventional lithium-ion batteries operate upon reversible Li+ transfer between a cathode and an anode through a liquid electrolyte. During charging process, Li+ extracted (de-intercalation) from the cathode migrates through an electrolyte for insertion (intercalation) into the anode. In photo-rechargeable lithium-ion batteries, the outward movement of Li+ (delithiation) is promoted by photooxidation of electrode material, however the mechanistic pathways (e.g., interdependence of bandgap of photoelectrode and battery voltage) for photo-induced Li+ extraction from the electrode are not well understood and will form a major aspect of this proposal. Although there are some reports on photo-switchable electrode materials, there is no insight into the role of liquid electrolyte that affects the photo-induced Li+ extraction. The originality of this project lies in its multidisciplinary approach in which the specialized know-how of the Japanese team in electrolyte development and solution/interfacial electrochemistry (PI: Prof. Y. Yamada) will be integrated with materials development and integration expertise of the German team (PI: Prof. S. Mathur) to realize a photobattery. The target of maximizing photo-charging efficiency will need adjustment of functional behavior of both electrode materials and electrolytes to accelerate Li+ extraction and prevent the recombination of photo-excited e-/h+, which cannot be achieved via conventional approach based only on electrode materials. The specific research objectives of this application include (i) fabrication of light active electrodes (ii) preparation of electrolytes and electrochemical assessment (iii) operando studies on interfacial electrode-electrolyte interactions under illumination and (iv) validation in full cell configuration.