Preparation of Porous LiFePO4 Electrode of Electrochemical De-intercalation/intercalation Method for Lithium Extraction from Brine
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摘要:
电化学脱嵌法盐湖提锂技术因其选择性高、吸附量大、绿色无污染等优点，越来越受到人们的关注，但盐湖卤水矿化度高、黏度大，导致实际提锂速率较低。基于此，以NH4HCO3为造孔剂，制备了具有良好渗透性和传质性能的多孔LiFePO4电极，以改善提锂过程动力学性能。结果表明：造孔改性后电极表面具有微裂纹-微孔的复合结构，可显著强化溶液的传质过程，降低电化学极化。以多孔电极进行电化学脱嵌法提锂，其嵌锂容量由传统电极的25.6 mg（Li）/g（LiFePO4）增加至多孔电极的35.2 mg（Li）/g（LiFePO4），且提锂过程的平均电流密度由8.7 A/m2提高至17.9 A/m2，提锂效率显著提高。此外采用多孔电极循环提锂30次后容量保持率高达98%，表现出良好的循环性能。
Abstract:Electrochemical de-intercalation/intercalation method for lithium extraction from brine has attracted more and more attention due to the high selectivity, the large adsorption capacity and the pollution-free. However, the high mineralization and viscosity of the brine lead to a lower actual lithium extraction rate. Based on this, NH4HCO3 was used as a pore-former to prepare porous LiFePO4 electrodes with good permeability and mass transfer properties to improve the kinetic performance in the process of lithium extraction. The results showed that there was a composite structure of microcracks-microporosity formed on the surface of the electrode after the modification, which could significantly enhance the mass transfer process of the solution and reduce the electrochemical polarization. After the pore-forming modification, the special capacity of electrode increased from 25.6 mg (Li)/g (LiFePO4) to 35.2 mg (Li)/g (LiFePO4) during the electrochemical de-intercalation/intercalation process, and the average current density increased from 8.7 A/m2 to 17.9 A/m2, indicating the efficiency of lithium extraction has been significantly improved. In addition, the electrode exhibited good cycling performance with a capacity retention rate of 98% for 30 cycles.
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图 1 电极的二维形貌图: (a)未造孔电极，(d)造孔电极；电极的SEM形貌图: (b) 未造孔电极，(e) 造孔电极；电极的三维形貌图: (c) 未造孔电极，(f) 造孔电极
Figure 1.
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