Advanced Membrane-Free Electrochemical Energy Storage Devices (Phase 1)

要实现风能和太阳能等可再生能源发电的可调度，就需要储能。各种储能技术在技术上已经成熟，并且可以在商业上使用。其中，基于钒电化学的氧化还原液流电池(简称VRFB)具有功率和能量密度独立确定的独特优势，在电网和离网固定储能领域具有广阔的应用前景。然而，当前一代的RFB存在运行效率低下的问题，主要是由于使用了将阳极液和阴极液分开的Nafion膜。然而，为了支持电化学的基本原理，有必要允许质子在膜上移动。Nafion膜不能防止钒离子通过它，导致电解液稀释和效率损失，并限制了电池的工作温度范围，通常在40°C以上。此外，Nafion膜成本高昂，约占电池组成本的40%。我们正在提出一种彻底创新的RFB/VRFB设计，在该设计中，膜以及相关的技术问题被消除。在我们的设计中，用金属氧化物(SnO/SnO2)制成的辅助电极(AE)取代了膜，辅助电极在充放电过程中改变了它们的氧化状态(Sn2+/Sn4+)，平衡了阴极液和阳极液中的电荷，为电化学储能提供了必要的电化学条件。俄歇电子能消除电解液隔室之间的离子移动，完全防止电解液溢出，而不会对电池性能产生负面影响。这种新颖的设计还提供了在具有灵活操作条件的RFB系统中使用高能密度电解液的机会。在该项目期间，将对五名总部人员进行RFB技术培训。这些HQP将熟练掌握储能的技术和业务方面的知识，并在不久的将来适合工业界和学术界对储能的高需求职位。

Energy storage is required for making renewable electricity generation, such as wind and solar, dispatchable. A variety of energy storage technologies are technically mature and commercially available. Among these, redox flow batteries (RFBs) operating with vanadium electrochemistry (vanadium redox flow battery, VRFB) offer a unique advantage of independently sizing power and energy density, and are therefore a promising candidate for grid and off-grid stationary energy storage applications. However, the current generation of RFBs suffer from operational inefficiency, primarily due the use of Nafion membrane that separates the anolyte and catholyte. Yet it is necessary to allow the movement of protons across the membrane to support the fundamentals of electrochemistry. The membrane is incapable of preventing vanadium ion crossover through it resulting in electrolyte dilution and efficiency loss, and limiting the battery operating temperature range, generally above 40°C. Additionally, the Nafion membrane is costly and approximately represents 40% of the cell stack cost. We are proposing a radically innovative RFB/VRFB design in which the membrane as well as the associated technical issues are eliminated. In our design, the membrane is replaced with auxiliary electrodes (AE's) made of metal oxides (SnO/SnO2), that change their oxidation states (Sn2+/Sn4+) during charging/discharging, balance the charges in the anolyte and catholyte, and provide the necessary electrochemistry for the electrochemical energy storage. AEs eliminate ionic movement between electrolyte compartments and completely prevent electrolyte crossover without negatively impacting cell performance. This novel design also provides an opportunity to use high-energy-dense electrolytes in the RFB system with flexible operating conditions. Five HQPs will be trained in the RFB technology during this project. These HQPs will be skilled in technical and business aspects of energy storage and suitable for high-demand energy storage positions in industry and academia in the near future.