Stability Improvement And Lithium Extraction From Sea Water/Brine Of NCM

As an important strategic resource,lithium and its compounds play a very important part in energy,defense industry and many other fields.After the 20th century,seawater and salt lakes are found with rich lithium resources,with the rapid growth of global demand for lithium,how to efficiently extract lithium from seawater/salt lakes has quickly become a research focus in various countries.Electrochemical lithium extraction,as a new technology for extracting lithium from seawater and brine,utilizes the working principle of lithium ion batteries.Compared to precipitation,adsorption and many other traditional methods,it has many advantages such as high selectivity,low consumption and environmental friendly.However,multi-metal composition and possible corrosiveness of seawater/brine requires high capacity electrode with high selectivity and cycle stability.To address this issue,this work proposed a less layer graphene gauze modified Ni-rich cathode material LiNi0.6Co0.2Mn0.2O2 core-shell structure microsphere(rGO/NCM)with shell thickness of 3 nm and core size of 8?10 ?m.XRD,Raman,HRTEM and other testing techniques proved that layered structure of NCM was well formed and the transition elements were uniformly distributed.The electrochemical tests of NCM and rGO/NCM in organic and aqueous systems show that rGO/NCM with core-shell structure has better performance in terms of cycle stability,rate performance,and initial capacity than unmodified origin samples.The rGO shell reduces the possibility of NCM phase transition from layered to spinel structure due to the migration of transition metal ions to the Li layer during the cycling process by increasing the electron transfer rate,thereby improving the electrochemical performance of NCM.Li+diffusion coefficient of CV in organic systems and ex-situ XRD in aqueous solutions all confirm the better performance of rGO/NCM.In a desalination system composed of rGO/NCM as a positive and activated carbon(AC)as negative electrode,rGO/NCM//AC delivered high Li+extraction efficiencies reaching of 13.84 mg/g per cycle in simulated brine by consuming only 1.4 Wh/mol Li+at optimized operating conditions.The purity of Li+in receiving solution is?93%and the rGO/NCM//AC system still has high selectivity and separation efficiency for Li+ after 15 cycles.The results show that rGO/NCM//AC has an excellent lithium extraction performance in salt lakes with a high Mg/Li ratio and is a promising electrochemical lithium extraction approach.