A Green Titanium-Cerium Redox Flow Battery with Long-Term Stability via Efficient Capacity Recovery

Redox flow batteries (RFBs) have emerged as a transformative technology for large-scale energy storage, with growing research interest in developing cost-effective and durable systems. Here, we present a capacity recoverable RFB system that utilizes low-cost titanium/cerium species-Ti-Ce RFBs. A mixed-electrolyte design suppresses ion crossover, achieving the average energy efficiency of 86.02% at 30mA cm^-2. Moreover, owing to the few side reaction and unique active ion complex structure with negative or neutral charge, the capacity of Ti-Ce RFBs after attenuation can be almost completely recovered by directly mixing the electrolyte. Remarkably, exceptional long-term stability over 3721 cycles (1886 h) at 50 mA cm^-2 with average coulombic efficiency of 99.09% can be achieved by recovery regulation of mixing the electrolytes after attenuation. This design offers a simple but practical strategy to make Ti-Ce RFBs as a promising candidate for long-duration energy storage.