基于超氧化物为放电产物的碱金属空气电池

In recent years, rechargeable non-aqueous “alkali metal-oxygen (A-O2) batteries” (i.e. lithium-oxygen (Li-O2) battery, sodium-oxygen (Na-O2) battery, and potassium-oxygen (K-O2) battery) have attracted much attention because of their much higher theoretical energy density than conventional lithium-ion batteries. However, A-O2 batteries have a few key challenges to be resolved, i.e., complicated discharge/charge mechanisms, low round-trip energy efficiency (<65%) and relatively unstable electrolyte. In this proposal we will establish energy storage mechanism based on the superoxides (LiO2, NaO2 and KO2) as the discharge product, aiming to improve the round-trip energy efficiency (80~90%). Firstly, because the trace of the superoxide radical (O2-) dissolved in electrolyte is probably related to the formation of the superoxides, we will focus on the potential effect of the electrolyte’s donor-number and the solvation process on the dissolution property of O2-, and possible decomposition mechanism of the electrolyte attacked by O2-. Next some fundamental issues during the discharge and charge processes will be studies systemically, including the nucleation-growth-decomposition process of the superoxides, possible side reactions and the alkali-metal anode protection. Especially, the structural stability of LiO2 and NaO2 during the cycle will be discussed emphatically, which closely correlates to the cyclic stability of batteries. Finally, a complete A-O2 battery system based on the superoxides will be built up, which includes both the systematically theoretical analysis and experimental characterization.

以锂空气电池为代表的碱金属空气电池(包括锂空气、钠空气和钾空气电池)由于具有超高的能量密度，是下一代高能量密度储能器件的一个重要研究方向。然而目前碱金属空气电池在一些关键性问题上仍存在严重不足，譬如基于多种放电产物的存储机理不完善、能量转化效率低(<65%)、电解液不稳定等问题。本项目拟建立以超氧化物(LiO2、NaO2、KO2)为放电产物的能量存储机制，从根本上提高碱金属空气电池的能量转化效率(80~90%)。首先从形成超氧化物的“前驱体”—超氧根(O2-)出发，揭示O2-在电解液中的溶解特性受溶液酸碱度、溶剂化过程等因素影响的规律，以及O2-导致电解液分解的化学/电化学机理，深入研究在充放电过程中超氧化物的形核-生长-分解过程、电子转移过程、副反应机理、碱金属负极保护等科学问题，重点研究掌握LiO2、NaO2的结构稳定性原理，最终建立以超氧化物为放电产物的碱金属空气电池的科学研究体系。

以锂氧气电池为代表的碱金属空气电池(包括锂氧气、钠氧气和钾氧气电池)由于具有超高的能量密度，是下一代高能量密度储能器件的一个重要研究方向。然而目前碱金属氧气电池在一些关键性问题上仍存在严重不足，譬如基于多种放电产物的存储机理不完善、能量转化效率低(<65%)、电解液不稳定等问题。本项目在超氧化钾在氧气电池中的稳定性、电化学反应的可逆性开展了深入研究，通过石墨插层化合物替代金属负极的方法，有效抑制了负极界面的不可逆反应，提高了电池的安全性和循环稳定性。并将超氧化钾引入到锂-氧气电池中，有效降低了锂-氧气电池的充电过电势。项目对提高碱金属-氧气电池金属负极的安全性和稳定性提出了有效策略。通过液态负极（常温下）替换固态负极，从根本上消除了枝晶生长，提高电池的安全性；通过金属/碳复合、人工SEI构建、醚类电解液开发，提高了金属负极的均匀沉积/剥离。通过在碳正极表面引入具有催化作用的官能团、开发非碳陶瓷/RuO多孔正极，显著降低了充电过电势，极大提高了锂-氧气电池的比容量和循环可逆性。