Research On Lithium Iron Manganese Phosphate Cathode Material

In this paper,the validation of LFMP cathode composite material is carried out,which is divided into three parts.The first part is the study of the cathode material of LFP/LFMPcore-shell cladding structure.According to the design ratio of 9:1,the test data of LFP prepared by different core in situ coating were compared.The results show that the in-situ coating material prepared by STL carbon-free LFP has a 0.2C specific capacity of148m Ah/g,a first-effect of 94%,and a 1C discharge specific capacity of 125.4 to127m Ah/g.Compared with the gram capacity of normal pure LFP,the gram capacity of in-situ coating material prepared by STL carbon-free LFP has a lower gram capacity.This may be related to the uneven size distribution of slurry.However,the median voltage parameters increase obviously,indicating that the core-shell structure has been formed.Compared with STL results,the material obtained by in-situ coating with DYLFP oxide as the core has a 0.2C specific capacity of 155m Ah/g,a first effect of about 96%,and a 1C discharge specific capacity of 143m Ah/g,which has reached the level of normal LFP,and the value voltage of 3.44V is higher than that of ordinary LFP 3.389V.The results show that the ideal LFP/LFMP core-shell structure is obtained by using DYLFP oxide as the core,and the desired design effect is obtained.When the core-shell ratio was increased to 8:2,all the performance indexes decreased.The real situation may be that core-shell structure materials are not completely formed inside the material,and part of LFMP is not involved in the shell structure.There are differences in raw materials from different manufacturers,which affect the experimental results.According to the electrochemical data,when the core-shell ratio increases,the first effect of the material will be reduced,and the performance of the oxide core-shell structure material is better than that of this batch of pure LFP,indicating that the use of oxide in the nuclear material has more advantages.The experimental results show that the synthesis method has a great influence on the core-shell structure of LFP/LFMP.The experimental results show that the core-shell structure of in-situ coated LFP/LFMP is feasible and has good application significance.The second part is the study of LiMn_0.6Fe_0.4PO₄/C core-shell coating ternary materials.The core-shell structure of LiMn_0.6Fe_0.4PO₄/C was prepared by ball milling and spray drying.Using the way of coating slurry coating ternary material,forming a layered structure of the pole sheet.SEM test shows that the composite is composed of primary nanometer（30-80nm）particles composed of secondary micron spherical particles with a diameter of about 5 microns,and the surface of the particles is uniformly coated with carbon layer.There is no spectrum peak of carbon material in XRD test,indicating that the curve is LiMn_0.6Fe_0.4PO₄/C material and there is no other miscellaneous phase.The charge-discharge curve test results of 2032 button battery show that the specific discharge capacity of0.2c is 195.2m Ah/g,which maintains the excellent specific capacity of ternary materials.The capacity decay rate of the battery is only 10%after 100 weeks of1C cycling,showing excellent cycling performance.The 14500 battery was assembled and the results showed that the battery passed the 4C-10V overcharge test,puncture test and short circuit test safely.The third part is the study of LFMP mixed LFP cathode material.LFMP physical mixing of LFP did not improve LFP battery,which may be due to the broadening of research ideas.Instead of simply mixing,sintering process after mixing should be added.Relevant experimental schemes are being improved.The research work in this paper explored the feasibility of LFMP composite electrode technology route,many experiments need to be improved in the future.Many relevant mechanisms are beyond our ability and cognition,which will lay a good foundation for us to carry out relevant research work continuously.