离子筛赝电容器高选择性吸收锂及微观吸附机制分析

Lithium ion sieve(LIS) is an excellent material for selective adsorption of lithium ions. However, there is inevitable aggregation of the materials due to high temperature treatment during preparation. Meanwhile, the adsorption rate is slow and the regeneration process is complicated. All these have limited its broad application in the recovery of lithium ions. This project aims to fabricate the lithium ion sieve-containing carbon nanofibre composite materials (LIS-CNF) via low-temperature hydrothermal synthesis of ion sieves, followed by electrospinning the lithium ion sieves with polymers （carbon sources） and carbonization treatment. The polymers in the fiber act as the matrix for the dispersion of the LIS, which can avoid the agglomeration of the ion sieves during the high temperature treatment, and improve the loading of the ion sieves. Further, the pseudo-capacitor can be constructed using LIS-CNF materials as the cathode and conducting polymer modified carbon fiber as the anode to achieve the super adsorption ability to lithium ions. The adsorption rate is greatly improved and the adsorption amount is highly enhanced, thanks to the synergy of ion sieve exchange, redox insertion and electric double layer adsorption. The nano-impact chronoamperometry technology is applied to investigate the adsorption mechanism and kinetics of lithium ions at the micro domain of the LIS-CNF surface, and the relevant kinetics model of the diffusion, migration and adsorption of ions to reveal the general law of the correlation of the kinetics process and the structure of the active materials. The feasibility of the ion sieve pseudo-capacitor desalination technology to the practical application in the lithium recovery of brine/seawater will be verified by energy consumption calculation and stability test by running the capacitor in the actual water sample.

锂离子筛是选择性吸收锂的优良材料，但其高温制备过程的易团聚、吸附速率慢及再生复杂等问题限制了其在锂离子提取技术中的广泛应用和推广。本项目拟通过低温水热及静电纺丝技术制备高度分散的锂离子筛/碳纳米纤维复合材料，纤维中聚合物提供了离子筛分散的基质，减少或避免了其高温团聚,提高了离子筛的负载量；并以该材料为阴极，导电聚合物修饰碳纤维为阳极构建锂离子筛赝电容器，从而实现锂离子筛的离子交换性、氧化还原性和电容器双电层吸附的协同作用，显著提高其吸附速率和吸附量。通过纳米撞击-计时电流技术从微观尺度探索锂离子筛/碳纳米纤维表面锂离子吸、脱附相关机制，建立离子在微观区域的表面扩散、迁移的相关动力学模型，揭示离子吸脱附动力学过程与活性材料结构相关性的一般规律。并通过对实际水样的循环运行、能耗计算、稳定性测试等，验证离子筛赝电容器脱盐技术对高原卤水/海水锂回收实际应用的可行性。

电化学提锂技术清洁、经济、高效，应用前景广阔。电容去离子（CDI）是新兴的电去离子技术。探究高导电性、高稳定性、高选择性的锂吸附电极材料是实现电化学提取锂的重点。锂离子筛（锰氧化合物）是选择性吸收锂的优良材料，但其高温制备过程中易团聚、导电性低、吸附速率慢、再生复杂及稳定性差等问题制约了其在锂离子CDI提取技术中的应用和推广。本项目结合炭纳米材料的导电性及锰氧化物类锂离子筛的氧化还原活性，通过固相反应及低温水热等技术，得到了高稳定性、高导电性、高选择吸附性的锂离子筛/纳米碳复合材料。通过炭基质材料（石墨烯、纳米管、静电纺炭纤维）调控，减少其高温团聚，提高了离子筛的负载量及有效利用率；同时在阳极材料改性方面，采用静电纺丝多孔炭纤维为阳极结合BiOCl修饰等提高其吸附容量，从而实现赝电容器的高容量和高选择性。建立了纳米撞击-计时电流技术测定颗粒表面离子吸附动力学方法，分析了电极活性材料中离子存储机制，为电极材料的筛选、电极结构调控以及电容器池的构型设计等提供理论指导。并通过对实际水样的容量分析、选择性测试、能耗计算、稳定性试验等，从而证明了离子筛赝电容器脱盐技术对高原卤水/海水锂提取实际应用的可行性。该项目所得结果为卤水/海水提锂及锂回收实际应用提供可靠的技术支撑和理论依据。