全钒液流电池电解液价态失衡机理及容量恢复策略研究

全钒液流电池作为一种新型大规模储能技术，因安全性高，具有容量和功率独立性等优势备受关注。然而，该电池的长期循环稳定性受到了容量衰减的影响。电池的容量衰减与正负极电解液价态失衡密切相关，目前人们对于价态失衡的机理尚未明晰，并且缺少有效的容量恢复策略。为了解决这一问题，本论文针对全钒液流电池电解液价态失衡机理以及容量恢复策略开展了系统性研究，使得电池长期运行的稳定性得到了有效提升。具体研究内容如下：

首先，通过建立正负极电解液的体积、浓度和价态失衡与电池容量衰减的数学模型，明确了电解液价态失衡对不可逆容量衰减的影响。结果表明，由电解液体积和浓度不平衡引起的容量衰减，可以通过混液方案进行修复。然而，对于电解液的价态偏离导致的容量衰减，仅依靠混液方案难以得到恢复。通过对电池在运行过程中的行为进行实验分析，揭示了充电过程中的负极析氢反应是导致电池电解液价态失衡的主要原因。而电流密度、充放电截止电压、电解液流速、电极活性及工作温度对析氢引起的电解液价态失衡有显著影响。

进一步，针对电解液价态失衡引起的容量衰减开发了一套修复装置。该装置由全液态甲酸燃料电池构成，不但可以在常温下恢复全钒液流电池的容量，并且可以输出电能。通过对催化剂进行优化和构建，使得该装置的功率密度可以达到282.5 mW cm^-2，为当前甲酸燃料电池的最高性能之一。另外，本论文基于流体力学与电化学耦合模型、密度泛函理论等揭示了装置的性能提升机理。最后，基于该装置提出了容量恢复策略并对电池的容量进行了修复。结果表明，电池在400圈后的容量仍能恢复到初始最高值的97.6%，有效提升了全钒液流电池的循环寿命。

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