Aerosol-based processes for the production of battery materials

What to learn about the production of battery materials with Glatt technologies?

With the introduction of the lithium battery by Sony in 1990, the development of active materials has gone through a steady process with the aim of increasing energy density. This is realised through the development of novel, nickel-rich and cobalt-free cathode materials, the production of silicon-carbon composite materials and the development of solid-state batteries. The increasing demand for applications within electromobility or stationary energy storage requires the implementation of novel, sustainable and continuous manufacturing processes as well as processes for coating active materials. Aerosol-based methods based on spray drying / spray calcination and spray granulation are presented using selected examples. First results on electrochemical characterisation are shown.

Materials and methods

Production of cathode materials

The development of new cathode materials starting from the layered oxide LiCoO₂ led to lithium nickel manganese oxides NMC and lithium nickel aluminum oxides NCA by substituting cobalt with other elements. In addition to these materials, which are predominantly used for electromobility, oxides of the olivine structure, e.g. lithium iron phosphate LiFePO₄, and materials of the spinel structure LiMn_2‑xNi_xO₄ are used. The production of these active materials involve a variety of methods, some of which require multiple process steps. These include precipitation and solid-state reactions, hydrothermal processes, and sol-gel processes. By applying aerosol-based spray drying and spray calcination processes, the number of process steps can be reduced and continuous production can be realized.

Production of anode materials

Graphite represents a common anode material. The theoretical capacity of this material is limited to a theoretical capacity of 372 mAh/g due to the formation of the compound LiC₆. The push for higher energy densities brought the focus to other elements. Silicon offers an alternative solution here due to its good availability and a much higher theoretical capacity of 3600 mAh/g. A volume change of 320 % during the charge and discharge cycle leads to fracture of particles, loss of contact to the current sink and continuous erosion of the protective boundary layer between silicon and electrolyte. The fabrication of silicon-carbon composites offers a promising approach to compensate for the volume change. The production can be done by continuous aerosol based processes based on spray drying and spray granulation.

Production of solid electrolytes

Another method of increasing energy density is the development of solid-state batteries in which the liquid electrolyte is replaced by a lithium-conducting material, for example lithium lanthanum zirconium oxide LLZO. This allows metallic lithium to be used as the anode material (theoretical capacity of 3860 mAh/g). The challenge here is the synthesis of the solid electrolyte. By producing it from aerosol-based processes, the reaction time can be shortened.

Coating of cathode materials

Another representative of solid state electrolytes is lithium phosphorus sulfide LPS. The material is characterized by high ionic conductivity. However, the material has low chemical stability with respect to oxide cathode materials, so that a coating of the active materials is necessary. Lithium phosphate Li₃PO₄, lithium niobate LiNbO₃, lithium borate Li_xB_yO_z and lithium titanium oxides LTO, among others, are being discussed. Processes based on spray drying and spray calcination can also be used for this purpose in order to realize continuous processing.