Preparation And Characterization Of High-Energy Density Storage Materials LiNi_1-x-yAl_xMg_yO₂

This article mainly reported on the preparation method and structuralevolution of new high energy density anode materials of rechargeable lithiumbatteries, LiNi1-xAlxO2 and LiNi0.75-yMgyAl0.25O2. It also discussed thatpossibility of their application as anode materials of rechargeable lithiumbatteries in view of their structures.LiNi1-xAlxO2 has positive formation enthalpy. It's easy to decompose, so itis difficult to compose LiNi1-xAlxO2 solid solution with high Al content.LiNi1-xAlxO2 is the solid solution of LiNiO2 and α-LiAlO2, so research had tobe done on the preparation condition and temperature scope of structuralstability of LiNiO2 and α-LiAlO2 respectively. Based on those results, wefound a new preparation method that can improve Al content rapidly inLiNi1-xAlxO2 solid solution. We prepared LiNi1-xAlxO2 (0≤x≤0.6)solidsolution samples with Al dissolved completely through this method. At thesame time, we found out that the doping of Al reduces the preparationtemperature of LiNi1-xAlxO2 and the dependence degree on oxygenatmosphere.The XRD and XPS studies were carried out. The results indicate that theinteraction between Ni(Al)and O are enhanced with the increasing of Alcontent, so that the average bond length of Ni1-xAlx-O decreases. As a result,the structural stability is enhanced. The XPS study also indicates that thebinding energy of Li1s increase with the increasing of Al content, so that thismaterial will possess higher balance voltage and energy density. And theomission of Li+ is suppressed gradually.A series of compounds with chemical formula of LiNi0.75-yMgyAl0.25O2were synthesized and their structures were studied by XRD. The results showthat both lattice constant a and lattice constant c of LiNi0.75-yMgyAl0.25O2increases, and cell volume V increases with the increasing of Mg content,which indicate that the layer properties are strengthened , while the bindingenergy are weakened with Mg doping. The changes not only benefit theprocess of lithium ion extracting and inserting, but also benefit the freemovement of the electrons because of the weak binding from lattice. As aresult, conductivity is enhanced.So far, according to LiNi1-xAlxO2和LiNi0.75-yMgyAl0.25O2, analysis of thestructure show that Al doping induces not only increasing of the LiNiO2structural stability but also the higher balance voltage and higher energydensity. On the basis of it, Mg doping will benefit the enhancement of theconductivity. All these results lay a foundation for the application of LiNiO2 asanode material of lithium batteries.