Grinding and Spheronization of Graphite

How efficiently electrical energy can be stored and provided in batteries and fuel cells depends in particular on the quality of the raw materials used in their manufacturing process.

Battery Grade Anode Graphite, made from natural graphite or in form of synthetic graphite based on petroleum coke, is the key raw material, for the anodes of Li-ion batteries. Even as silicon, which is currently added at 4-8%, is gaining importance, the characteristics of the graphite are most critical to improve battery performance.  

Battery Performance, such as high capacity and energy density as well as short charging cycles, is particularly important for use in electric vehicles (EV).

Battery Anode Grade graphite therefore must have special properties in order to influence battery performance positively. Decisive factors are:

  • Fine but steep particle size distributions
  • High tap density
  • Low Specific BET surfaces
  • Spherical Particle shape (Spherical Graphite - SPG) 

While the product characteristics determine the performance, the grinding and spheronization process and equipment to achieve these characteristics, determine the economic and ecologic viability of such production.

In order to provide Graphite producers with a high capacity, low-energy, high-yield, economic and ecologic solution, NEUMAN & ESSER Process Technology has developed the NEA|Sphere grinding and spheronization equipment series.

NEA|Sphere: Grinding and Spheronization Process - Efficency, Simplicity, Reliability

Contrary to the traditional micronisation and spheronization process for natural graphite, where each particle has to pass many individual mills in a cascading mill line, in the NEA|Sphere process each particle only passes one grinding unit and one spheronization unit. Breaking down the process into the basic two process steps and using dedicated units to perform these process steps, offers the following advantages:

Efficiency:

  • Minimized particle stress
  • Low amount of superfines
  • Much higher yields
  • Low specific energy consumption
  • Low Co2 footprint at low OPEX

Simplicity:

  • Only two serial units involved
  • Low complexity
  • Simple setup
  • High flexibility to adjust for changing quality requirements

Reliability:

  • Parallel instead of serial arrangement of Production units
  • High availability of the overall plant, as individual units may be maintained while keeping up the production of parallel units

NEA|Sphere M: Steep Particle Size Distribution and finest Particles

In order to produce fine particles with a steep particle size distribution, i.e. small proportion of so-called "superfines", the NEA|Sphere M has been equipped with unique air and particle guidance as well as a highly efficient integrated classifier module. The material is ground to the desired fineness on this mill, but not overground. For battery applications the fineness requirements are often in the range of 90% < 10-40 µm.  

NEA|Sphere S: High tap densities and steep particle size distributions

Besides strict PSD requirements, Battery Anode Graphite also requires a spherical shape in order to perform ideally in the battery cell. The NEA|Sphere S has been developed for spheronization of flaky graphite as well as petroleum coke particles Due to tools specifically designed for this purpose and the highly efficient integrated classifier module for ultra-fine classification, the NEA|sphere S allows the complete spheronization of particles in a single step. This rounding is possible for natural and synthetic graphite as well as for green and calcined coke before graphitization.

The spheronization process on the NEA ICS is characterized by high tap densities, low BET surface areas, and high yields of up to 85%. In addition, undesirable fines can be specifically removed from the product by varying the classifier speed. This allows for even steeper particle size distributions and higher tap densities.

Petroleum Coke (precursor of synthetic graphite)

Natural Graphite

Adaption of the particle size distribution by the NEUMAN & ESSER GRC:

The NEA GRC guide ring classifier offers a further possibility for the targeted modification of a particle size distribution in the fine and coarse range. This classifier is used, among other things, to separate specific ultra-fine fractions in order to achieve steep particle size distributions. This process offers the advantage that the finest fraction can be reused either by blending or in applications with other products.  This increases the overall yield.