Ultrashort and Vertically Aligned Channels: Boosted Lithium Selective Extraction via Hybrid Capacitive Deionization
Hongmei Zhang, Lu Zhao, Zhiyuan Guo, Lei Wang, Yueqi Ma, Panpan Zhang, Jing Wang, Zhiyong Ji
Abstract
Hybrid capacitive deionization (HCDI) is energetically and operationally favorable for Li + extraction from salt lake brines. The bottlenecks of current LiMn 2 O 4 (LMO)-based electrodes are their limited Li + adsorption rate and capacity, caused by disordered electron/ion transport channels and insufficient ion-accessible sites. Inspired by selective ion uptake processes in mangroves, we propose the strategy, fabricating ultrashort, vertically aligned channels for Li + transport in the electrode to enhance the Li + selective performance of HCDI. The self-supporting graphene/LMO/bacterial cellulose electrode featuring vertically aligned channels (VGLB) possesses sturdy framework, excellent electrical conductivity, fast electron/ion transport channels, and abundant available Li + adsorption sites, enabling an ultrahigh Li + adsorption rate of 2.6 mg g –1 min –1 and capacity up to 33.9 mg g –1 with a high retention of 91.62% after 100 cycles. VGLB also manifests superior selectivity in various simulated salt lake brines with Li + purity in recovered solution of over 85%. Most importantly, VGLB enables selective Li + extraction in low-grade brine from Jingbian oil and gas-produced water. We conduct finite element simulations to study the Li + distribution in the electrode and disclose how the electrode microstructure influences the Li + extraction performance. This approach put forward an avenue for electrode structure design for efficient Li + extraction from both salt lakes and low-grade brines with HCDI application.