三维网络结构导电水凝胶高效海水提锂研究

As an important energy metal, the global demand for energy metal is increasing and lithium extraction from seawater is of great significance to the development of lithium resources. Currently, the λ-MnO2 lithium ion-sieve with Li+ imprinting channel is the most widely used adsorbent for lithium extraction from liquid phase due to its high lithium extraction capacity and excellent lithium separation performance. Although combining it with electrochemical method can improve efficiency, there are still problems that λ-MnO2 is easily dissolved and the structural stability is poor in the cycle application. So, 1) a novel 3D nanostructured conductive polypyrrole hydrogel framework embedded with λ-MnO2 nanoparticles (3D-PPy/λ-MnO2) is proposed in this project. That is, λ-MnO2 nanoparticles are used as self-template and initiator, and a highly conductive, tough and tunable 3D network-structured inorganic-organic hybrid hydrogel is designed by in-situ polymerization technology through doping with different cross-linkers. Also, its characteristics will be studied. 2) It will be efficiently applied to separate Li+ from seawater through electrochemical method. Also the inherent mechanism between the structure of 3D-PPy/λ-MnO2 and Li+ separation performance will be revealed. The strategy proposed here not only can overcome shortcomings of slow adsorption rate and loss of powder caused by absorption method, but also can maintain the structural stability of the electrode during the lithium extraction process. Finally, the efficient separation of Li+ from seawater can be achieved, which can provide a reference for promoting the development of lithium ion-sieve in the field of electrochemical extraction of lithium resources.

作为重要的能源金属，全球对锂的需求量与日俱增，海水提锂对开发锂资源意义重大。具有Li+“印迹”孔道的λ-MnO2锂离子筛由于吸附量高及锂筛选性优异成为目前应用最广泛的液相提锂吸附剂，将其与电化学法相结合虽可提高提锂效率，但仍存在易溶损和循环应用中结构稳定性差的问题。针对这一问题，本项目1）提出将λ-MnO2嵌入新型三维网络结构的聚吡咯导电水凝胶框架内（3D-PPy/λ-MnO2），即λ-MnO2纳米颗粒作为自模板及引发剂，借助交联剂的掺杂，利用原位聚合技术可控合成高导电性、强韧性及三维网络结构的复合水凝胶并研究其特征；2）结合电化学法高效分离海水中Li+，揭示Li+在这一结构中的嵌脱机制。本项目提出的策略不仅可克服吸附法吸附平衡慢及粉末易流失等问题，还可保持电化学提锂过程中电极材料的结构稳定性，最终实现海水中Li+的高效分离，为推动锂离子筛在电化学法提取液态锂资源领域的发展提供参考。

对锂离子筛如λ-MnO2进行功能化是改善提锂性能的关键。然而，有机(如传统聚合物)或无机刚性包覆因堵塞其位点在一定程度上降低了吸附量及提锂效率。项目针对传统负载型锂离子筛面临的位点包埋及效率低的问题，以揭示“负载型锂离子筛形成机制”和“水凝胶强化锂离子筛提锂机制”两个紧密相关的科学问题为中心，系统研究了聚合物水凝胶包覆离子筛的提锂构效关系及应用研究。成功构筑了λ-MnO2水凝胶，证实无需造孔剂，λ-MnO2活性位点同时起到了自调节水凝胶孔结构的作用，建立了无机-有机界面结构调控的方法，实现了复合水凝胶在海水环境条件下锂的高效提取。进一步在理论计算指导下，分析了含羟基纤维素及MXene与锂离子筛的相互分子间作用，结合多界面结构的调控增强了锂离子筛与柔性膜的结合强度，建立了锂离子筛基自支撑膜的结构调控策略。通过物理建模，揭示了复合体系的提锂机制，证实了柔性基底在锂离子筛提锂过程中的自拦截作用及强化提锂速率的构效关系，提出了构筑锂离子筛基复合柔性体系的预测模型。总之，通过耦合柔性基底与锂离子筛的特性规律，完善了锂离子筛的化学理论，形成了调控锂离子筛提锂行为的技术基础，为解决锂离子筛在电控提锂中面临的难题提供了理论依据。