Thick electrodes greatly enhance lithium extraction capacity. However, with the increase of active substances loading, the traditional thick electrodes are more hydrophobic, severely limiting the utilization of active substances. Hence, a sulfonation process to functionalize thick electrodes was applied to enhance their wettability (~45 mg·cm⁻¹) in brine. Experimental and theoretical results show that the lithium extraction capacity of thick electrodes can be significantly improved by enhancing the electrodes hydrophilicity. At 0.8 V, the S-PVDF electrode's capacity for lithium extraction in simulated brine (41.72 mg·g⁻¹) significantly surpassed the PVDF electrode (35.72 mg·g⁻¹), and it also performed well in actual brine (28.8 mg·g⁻¹). The Mg²⁺/Li⁺ ratio in actual brine dropped from 65 to 0.37, achieving effective magnesia‑lithium separation. This method offers a novel approach to developing high-efficiency lithium extraction thick electrodes.

Enhancing the kinetic performance of thick electrodes is essential for improving the efficiency of lithium extraction processes. Biochar, known for its affordability and unique three-dimensional (3D) structure, is utilized across various applications. In this study, we developed a biochar-based, 3D-conductive network thick electrode (∼20 mg cm−2) by in-situ deposition of LiFePO4 (LFP) onto watermelon peel biomass (WB). Utilizing Density Functional Theory (DFT) calculations complemented by experimental data, we confirmed that this The thick electrode exhibits outstanding kinetic properties and a high capacity for lithium intercalation in brines, even in environments where the Magnesia-lithium ratios are significantly high. The electrode showed an impressive intercalation capacity of 30.67 mg g−1 within 10 min in a pure lithium solution. It also maintained high intercalation performance (31.17 mg g−1) in simulated brines with high Magnesia-lithium ratios. Moreover, in actual brine, it demonstrated a significant extraction capacity (23.87 mg g−1), effectively lowering the Magnesia-lithium ratio from 65 to 0.50. This breakthrough in high-conductivity thick electrode design offers new perspectives for lithium extraction technologies.

Despite the high energy density of lithium-rich manganese-based (LR) cathode materials, the practical implementation in batteries has been impeded by the intrinsic issues regarding cycling. Herein, a coherent interface modification strategy is proposed. The LR materials are coated with a lattice-matched Li3BO3 (LBO) layer at the interface. The coating applied to the electrode has two impacts. (1) It reduces interfacial side reactions between the electrode materials and electrolyte, thereby improving structural stability. (2) It mitigates stress between solid particles, which enhances the cycling stability (83% after 500 cycles at 2C) of LR. Furthermore, the LBO coating promotes the development of a spinel-like structure on the electrode materials surface, eliminating unstable oxygen, increasing oxygen vacancy (Ov), consequently enhancing the initial Coulombic efficiency (ICE, 92.18%), and alleviating particle breakage (Young’s moduli of LR@S@LBO is 3.26 ± 1.6 GPa) after optimization. Theoretical calculations show that Ov and spinel can improve the diffusion of Li+ and the structural stability of LR materials. This work shows great potential for the rational design of high-energy-density electrode materials.