Study On The Performance Regulation Of Spinel Lithium Manganate

With the emergence and development of our country’s new energy industry,the demand for high-performance lithium electric energy storage equipment is increasing in the fields of communications industry,electric vehicle and hybrid electric vehicle.The property of lithium-ion batteries crucially depends on the cathode materials.Traditional lithium cobalt oxide has gradually withdrawn from the market due to its high price and environmental pollution.As one of cathode materials,spinel lithium manganate extremely has the brilliant development prospect owe to its abundant sources,environmental friendliness,low cost,and simple preparation.But the problems of poor cycle stability and poor large-rate performance restrict its further large-scale industrial application.Hence,improving the performance of lithium manganese oxide is a top-priority issue.In this article,spherical spinel lithium manganate was synthesized by co-precipitation and template-based method.And the effect of lithium content on the properties of lithium manganate materials was analysed.Due to the partial loss of lithium ions caused by the formation of the SEI film,the results indicate when the amount of lithium is adjusted to an excess of 5%,the synthesized lithium manganate sample exhibits the best electrochemical performance.Under the optimal amount of lithium,a spinel lithium manganate material doped with phosphorus is prepared.Analyzing the change in the lattice structure of lithium manganate after phosphorus doping,it is found that phosphorus doping makes the lithium manganate crystal grow more completely with higher crystallinity,and the cycle performance is greatly improved compared to the undoped material.Comparing samples with different phosphorus doping content,it is found that the material with a doping content of 1%,Li Mn_1.98P_0.02O₄ has the best electrochemical performance.The discharge specific capacity reaches 117m Ah g^-1 in first cycle.Cycling 150cycles under 0.5C current and 250 cycles under 1C current achieves a higher capacity retention rate of 95.4%and 97.3%.The morphology and structure affect the rate performance of the lithium manganate material.In this paper,the porous structure of the spherical lithium manganate material is studied by the producing gas method and the etching-template method.Studies have manifested that porous spherical lithium manganate materials with different structural characteristics are synthesized by different pore-producing methods.The prepared porous materials by the producing gas method have uniform internal and external pores,while the porous materials prepared by the etching template method have few surface pores and more internal voids.The increase in the internal pores of the microspheres enables the electrolyte to more fully infiltrate the material,and the migration path of lithium ions in the solid phase crystal is also shortened,which is beneficial to improve the discharge performance at large rates.At 0.2C current,porous spherical lithium manganate prepared by producing gas method has the highest discharge specific capacity,reaching 114.2m Ah g^-1,5C current reaching 88.9 m Ah g^-1,and 10C current reaching 73.6 m Ah g^-1.Based on phosphorus doping and porous structure control,the synergistic effects of the two on the structure and performance of lithium manganate materials were studied.The experimental results show that the synergistic effect of phosphorus doping and porous structure has a higher improvement effect on electrochemical performance than a single phosphorus doping or porous structure.In terms of rate performance,the discharge specific capacity of phosphorus-doped porous spherical lithium manganate at 10C current can reach 98.4 m Ah g^-1,and even holds a capacity of 68.7 m Ah g^-1 under 20C current,which is much higher than that of single-acting manganese acid.Lithium material.In terms of cycle performance,the materials reached capacity retention rate of 94.4%and 100%respectively after 1000 cycles at 5C and 10C current.It shows that coordinated regulation of phosphorus doping and porous structure design can achieve the performance of spinel lithium manganate in both rate capability and cycling stability.