Preparation And Electrochemical Performance Of Li_1.2Mn_0.54Ni_0.13Co_0.13O₂ Cathode Material For Lithium Ion Battery

The rapid development of the electric vehicle market has rapidly increased the demand for lithium ion batteries.And the characteristics of high energy density and long cycle life have become the requirements for the cathodes of the next generation of lithium ion batteries.Lithium-rich layerd oxide is considered to be the most potential cathode material for next-generation power batteries due to its high discharge specific capacity,low cost,low toxicity and high operating voltage.However,lithium-rich materials have not been widely used because of their low efficiency,low voltage decay,and poor cycle and rate performance.Designing rational morphology and controlling size have been efficient strategies to improve electrochemical performance of electrodes for lithium ion batteries.In this paper,Li_1.2Mn_0.54Ni_0.13Co_0.13O₂ materials with porous rod-like morphology have been successfully prepared by one-step coprecipitation method with subsequent heat treatment.The morphology of the prepared material can be easily controlled by adjusting the solvent of the precursor solutions.The relationship between products with different morphology and their electrochemical performance are systematically investigated.The material synthesized in deionized water exhibits prism-like morphology,and the material synthesized in ethanol has the morphology of dispersed particles.The materials synthesized in a mixed solvent of deionized water and ethanol show porous rod-like morphology after calcination.The more the ethanol content,the larger the length-width ratio of the rod.The material prepared at a ratio of deionized water to ethanol of 1:4 exhibits the best electrochemical performance due to its unique rod-like structure and moderate size.And the length of the rod material is about 7-8 ?m and the width is about 1.5-2.0 ?m.The initial discharge specific capacity of the sample is m Ah/g at 0.5 C,and the capacity retention rate can reach about 90% after 100 cycles.Its capacity does not decay substantially within 100 cycles and remains at about 188.3 m Ah/g at 1 C,and the capacity retention rate can reach about 82.7% after 300 cycles.The outstanding electrochemical performance can be attributed to the porous rod-like morphology,which not only promotes the contact between the electrolyte and the active material,but also shortens the lithium ion transmission distance and stabilizes the structure of the material.The core-shell structure Li_1.2Mn_0.54Ni_0.13Co_0.13O₂ cathode materials have been successfully prepared through a facile template-free method by using a solvothermal method with subsequent heat treatment.The size of the products can be easilycontrolled by adjusting the concentrations of the precursor solutions.The relationship between products with different sizes and their electrochemical performance are systematically investigated.Within a certain concentration range,the size of the precursor sphere increases with concentration increasing.The material prepared with precursor concentration of 0.03 mol/L exhibits the best electrochemical performance due to its unique core-shell structure and moderate sphere size.And its diameter is about 1.5 ?m.The sample delivers a high initial coulombic efficiency of 89.7%.Its capacity does not decay substantially within 50 cycles and remains at about 220 m Ah/g at 0.5 C.When cycled at 5 C,it has a high capacity retention rate of 96.2% and delivers a high specific capacity of 112.8m Ah/g after 500 cycles.The outstanding cycling stability can be attributed to its unique core-shell structure and moderate sphere size,which can buffer the structural strain during cycling.