Preparation And Electrochemical Properties Of Ni-rich Cathode Materials For Lithium-ion Batteries

Ni-rich layered cathode materials have become one of the most concerned lithium-ion battery cathode materials due to their high specific capacity and low cost.In particular,Ni-rich cathode materials with low-cobalt or cobalt-free have become a new research hotspot.In this paper,Li Ni_0.95Mn_0.05O₂material was prepared by high-temperature solid-phase method,and the research was carried out from three aspects:optimization process,doping modification,and coating modification.The main contents are as follows:（1）Li Ni_0.95Mn_0.05O₂（NM95）cathode material was prepared by high-temperature solid-phase method with Ni_0.95Mn_0.05（OH）₂and Li₂CO₃as raw materials.The best electrochemical performance of NM95 material is obtained under the ratio of Li/（Ni+Mn）=1:1.05 and calcination at 800℃for 12 h in oxygen atmosphere.At the current density of 1 C at room temperature,the initial discharge capacity of NM95 is163.34 m Ah g^-1,and the capacity retention is 81.98%after 50 cycles.（2）NM95 was modified by Li₂Ti O₃coating with tetrabutyl titanate as the titanium source.The introduction of the Li₂Ti O₃coating layer greatly improves the cycle stability of the material.The capacity retention of NM95-4LTO is 83.44%after 200cycles at 1 C at room temperature,which is 22.09%higher than NM95.The excellent cycle stability benefits from the enhancement of the phase transition stability of the material by the Li₂Ti O₃coating layer.（3）NM95-1Co was synthesized by high-temperature solid-phase method.The successful incorporation of Co into the structure of the material results in the lengthening of c-axis,the increase in content of Ni³⁺on the surface of the material and the improvement of surface stability.The capacity retention of NM95-1Co is 77.10%after 200 cycles at 1 C,which is 22.09%higher than NM95.The excellent cyclability of NM95-1Co comes from the structural stability of the material in the deep delithiation state and the smaller interface transfer resistance.（4）NM95-1MA was synthesized by high-temperature solid-phase method.Doping of Mg and Al lengthen the c-axis of NM95 material,increase the surface Ni³⁺content and improve the cycle stability,which is similar to the equivalent Co doping.The capacity retention of NM95-1MA is 75.57%after 200 cycles at 1 C,which is attributed to the improvement of the structural stability and the reversibility of phase transformation of NM95-1MA.