Innovative iron oxides for the production of lithium-iron-phosphate for use in rechargable batteries

Electric drives are playing an increasingly important role as an eco-friendly alternative to conventional engines in vehicles. Lithium-ion-batteries are usually used as a power source due to their high energy density. For mobile applications, the preferred cathode material is lithium-iron- phosphate (LiFePO4 or LFP) owing to its good technical properties, long service life, good reliability, environmental compatibility and comparatively low cost.

Carbothermic reduction is playing an increasingly important role in the production of lithium-iron-phosphate and is paving the way for the use of customized iron oxide precursors. In addition to wet chemical methods such as hydrothermal synthesis and coprecipitation, many manufacturers use solid-state reactions for the production of LFP. In traditional solid-state synthesis, iron (II) compounds such as iron oxalate are used as a source of iron. Many of these compounds are relatively expensive while exhibiting less storage stability and relatively undefined morphological properties. Increasing interest is therefore being shown in LFP production based on carbothermic reduction using iron (III) compounds such as iron oxides. Graphite, carbon black or organic substances are used as reducing agents that produce carbon during the calcination of the raw materials. Another advantage of this method is that the low electrical conductivity of the LFP powder can be increased to a sufficiently high level by separating off conductive carbon, and grain coarsening can be suppressed during the sintering process. Only then does the material satisfy the prerequisites for use in batteries.

With Bayoxide® E B, the specialty chemicals company LANXESS has developed a product line for the production of high-quality lithium-iron-phosphate using solid-state synthesis. During the carbothermic reduction process, the quality of the resulting LFP is influenced by both the process parameters and, above all, the chemical and morphological properties of the iron oxide precursor. The use of Bayoxide® E B products offers numerous advantages like optimized particle size, narrow particle size distribution, high reactivity, high purity, good dispersibility, and optimized mixing behavior.