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

自维持电化学能量存储系统对于缓解未来可持续社会的能源转型障碍至关重要。锂离子可再充电电池代表一类由于高能量密度、倍率能力和可靠性而被广泛部署的能量存储装置。然而，由于需要外部负载来逆转负责功率提取（放电）的电化学反应，锂离子电池的自主性受到限制。在这种情况下，基于双模式电极的可光充电电池表现出光和电化学活性，代表了突破性的能源技术，同时收获和存储太阳能。在光照和黑暗条件下进行的电化学研究表明，光生空穴促进了Li+离子从阴极材料中的提取，这使得电池能够仅通过光照进行再充电。在该双边项目中，将研究新的电极材料（德国团队）和光稳定电解质（日本团队），以开发可通过可见光直接充电的光可充电锂离子电池。常规的锂离子电池在阴极和阳极之间通过液体电解质的可逆Li+转移时运行。在充电过程中，从阴极提取（脱嵌）的Li+迁移通过电解质以插入（嵌入）到阳极中。在光可再充电锂离子电池中，Li+的向外移动（脱锂）通过电极材料的光氧化来促进，然而，光电极的带隙和电池电压的相互依赖性）对于从电极的光诱导Li+提取还没有很好地理解，并且将形成该提议的主要方面。虽然有一些关于光可切换电极材料的报道，但没有深入了解液体电解质影响光诱导Li+提取的作用。该项目的独创性在于其多学科方法，其中日本团队在电解质开发和溶液/界面电化学方面的专业知识（PI：Y教授）。山田）将与德国团队（PI：S教授）的材料开发和集成专业知识相结合。Mathur）来实现光电池。最大化光充电效率的目标将需要调整电极材料和电解质两者的功能行为以加速Li+提取并防止光激发的e-/h+的复合，这不能通过仅基于电极材料的常规方法实现。本申请的具体研究目标包括（i）光活性电极的制造（ii）电解质的制备和电化学评估（iii）光照下界面电极-电解质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.