Problems of submicron active powders are their big surfaces, such as lithium iron phosphate. Owed to this the coating process requires a lot of solvent. Result is a low solid content, respectively a high slurry viscosity. Therefore special technology and big efforts are necessary for the industrial mass production to process such submicron lithium iron phosphate powders. To overcome the handling difficulties of the submicron powder, spherical secondary agglomerates have been synthesized from those submicron particles. These agglomerates have the size of standard oxide cathode powders (2 µm – 30 µm).

The tap density of the agglomerates could be reduced and the surface area is much lower (~30%). Due to this fact, high solid contents can be realized in the slurry. This leads to reduced amounts of necessary solvent within the coating process. Advantages for the processability are in summary: higher tap density, reduced surface area, reduced solvent demand, greatly simplified slurry dispersing processes and high areal loadings of the electrodes.

The synthesis of secondary agglomerates with lithium iron phosphate allows much better processability and a higher areal loading in the electrodes by preservation of the advantages of the sub-micron materials.

This work compares electrodes of the newly developed lithium iron phosphate secondary agglomerates with the primary submicron particles in respect to their areal loading, high rate capability and processability. Lithium iron phosphate has a very good rate capability and excellent safety features. The submicron powder has disadvantages that lead to a highly increased effort in processing and a limited areal loading. With the design of  spherical agglomerates those disadvantages could be eliminated. Moreover all the advantages of the material itself could be combined with better processability. Processability and the full cell performance of primary particles with those of  secondary agglomerates from lithium iron phosphate are compared.

Electrodes prepared from the secondary agglomerates make it even easier to reach higher areal loading ( >2 mAh/cm²  or 13 g/cm²). Additionally the electrochemical performance of the primary particles could be enhanced. The increased tap density and the smaller surface area enhance processability. Reduced amount of solvent enable slurries with improved rheology for established dispersing and coating processes.

The design of secondary agglomerates leads to much better processable cathode powders and electrodes with retained or improved electrochemical properties of such prepared with the original powder material.