Synthesis of Li-ion battery cathode materials via freeze granulation

Keivan Amiri Kasvayee
Department of Materials and Manufacturing Technology
Chalmers University of Technology

Göteborg, Sweden

Synthesis of Li-ion battery cathode materials via freeze granulation

Summary

Recently, enormous efforts have been done within the development of Li-ion batteries for use in portable electric devices from small scale applications such as mobile phones, digital cameras, laptop computers, to large scale applications like electrical vehicles (EVs) and hybrid electric vehicles (HEVs). LiFePO4 as an active material in cathode materials in Li-ion batteries has shown outstanding advantages compare to other cathode materials such as low cost, low toxicity and environmental compatibility, good thermal stability, high theoretical specific capacity of 170 mAh/g and operating reversibility at 3.4V. Still, it is a need to develop the manufacture of the cathode material to achieve improved performance reliability by using  environmental sustainable processes in order to meet future demands in large scale production and uses of Li-ion batteries.
The aim of this work was to develop a non-toxic, cheap, efficient and environmentally friendly process for synthesis of high quality active cathode material based on LiFePO4 for Li-ion batteries. Water based suspensions/solutions containing various reactant constituents have been homogenized, granulated and calcined. Freeze granulation was applied as the key tool for the synthesis of LiFePO4 with integrated carbon in order to produce granules with high degree of homogeneity prior to calcination. The resulting powder materials have been evaluated by XRD, carbon and conductivity measurements and characterization of other physical properties such as density and specific surface area. The promising version was used for manufacture of cathode material by tape casting, cell assembling and evaluation of the performance by charge/discharge cycling of the cells.
For the best sample in our experiment the XRD results revealed a high degree of purity, homogeneity and crystallinity of LiFePO4. The produced LiFePO4/C composite also had a high specific surface area and, therefore, considered as a promising material for cathode manufacturing and cell assembly. A discharge capacity of 155 and 140 mAh/g was achieved at the fifth cycle at 0.1C rate at room temperature for the cathodes which were made with NMP (solvent based) and water system, respectively. The long-term stability test indicated good result with no loss in capacity for at least 390 cycles. The satisfactory discharge capacity should be attributed to the homogenous nano-sized particles with a conductive porous carbon structure that was provided by the freeze granulation process and adapted calcination process.

Keywords: Li-ion batteries, LiFePO4, cathode active material, specific capacity, freeze
granulation, calcination, LiFePO4/C composite, cell assembly.

Please contact us and we will further discuss the opportunities with Freeze Granulation in your powder system and read more on technology.

Wet Granulation

Freeze Granulation – homogeneous wet granulation of powders

Freeze Granulation is a wet granulation method where the powders, chemicals and binders are first mixed and dispersed in a solvent. In the next step the homogeneous slurry is pumped and sprayed through a nozzle to form droplets, which are sprayed into liquid nitrogen for instant freezing. In the final step the frozen granulate is moved to a freeze dryer where the solvent is sublimated leaving spherical, dust-free and homogeneous granules. The solvent could be water or organic solvents with a freezing point close to zero degree, like cyclohexane.

Please contact us and we will further discuss the opportunities with Freeze Granulation in your powder system and read more on technology and a Granulation Test of your powder system.

 

Spray-freezing and freeze drying

Spray-freezing and freeze drying – Freeze Granulation

PowderPro AB develop, manufacture, market and sell equipment and know-how for Freeze Granulationspray freezing and subsequent freeze drying (lyophilization or cryodesiccation). Freeze Granulation was developed in late 1980s at Swedish Ceramic Institute in Göteborg and it is also a development of Spray Freeze Drying (SFD) and Spray Freezing into Liquid (SFL).

Spray cooling or rather called spray freezing is the first step in the freeze granulation process where a suspension is atomized, sprayed with a nozzle, into a chamber with liquid nitrogen. The small droplets are then rapidly frozen with a minimum of ice crystal growth. The frozen material (granules) are then transferred to a freeze dryer where the ice is removed by sublimation, i e never go through a liquid state that ensure homogeneity preservation.

Below you can see an illustration of the Freeze Granulation process.

Please contact us and we will further discuss the opportunities with Freeze Granulation on your powder system and read more on technology and we propose a Granulation Test of your powder system.

Illustration of Freeze Granulation
Illustration of Freeze Granulation

How to make granules from powders

Homogeneous Granules by Freeze Granulation

By using Freeze Granulation or Spray Freeze Drying it’s possible to make spherical, homogeneous and dust-free granules with optimal flowability which is critical for automatic uniaxial pressing of for ex ceramics and metal powders.

You can expect spherical and homogenous granules of powders in terms of distribution of particle size  and other possible additives you want to use. The granules with a size distribution in the range of 50-300 microns will have weak inter particle bonding making them easy to break down in pressing or re-disperse into another formulation. Very much depend upon how you intend to process the powder and depending on that, adaptation can be made.

Please contact us and we will further discuss the opportunities with Freeze Granulation on your powder system and read more on technology and we propose a Granulation Test of your powder system.

Nano Diamond Powder

Freeze Granulation is today being used for mixing, granulation and drying of nano diamond powders. The resulting granules have a homogeneous distribution of nano diamond particles, fillers, binders and nano pores. Please go to Contact and ask for more information and for a Test-Granulation.

 

Processing of nanoparticles
Processing of nanoparticles

Technical specification lab-scale freeze granulator (LS-2)

PowderPro AB provides equipment for Freeze Granulation in two versions, LS-2 (see photo) and LS-6. The maximum granulation capacity of LS-2 is 2 litres slurry per hour and for LS-6 6 litres slurry per hours that typically correspond to ca 2 and 6 kg dry powder respectively.

LS-2 and LS-6 consists of a slip container with a stirrer, a pump for the slip, a spray nozzle, a regulator for compressed air and an insulated chamber for spraying and granule collection. Technical Specification LS-2

Besides the granulator, a freeze dryer (see photo of Lyovac GT2 below) with sufficient capacity is required and can be provided. Technical transfer including set-up of equip­ment and training of personnel is recomm­ended and offered upon request.

Please contact us and we will further discuss the opportunities with Freeze Granulation on your powder system and read more on technology and we propose a Granulation Test of your powder system.

Equipment for agglomeration of fine powders
Lab-scale freeze granulator LS-2

 

Freeze dryer Lyovac GT2

 

 

 

 

 

 

 

 

Technical specification GT2:  Freeze-Dryer-Drying-Vacuum-Lyophilizer-LYO-GT2-Overview–Product-Information-2010v01

Questionnaire for test of freeze granulation

If you would like to make a test-granulation, please download and fill in our Questionnaire for test of freeze granulation and email it to us and contact us if you have any questions.

Please contact us and we will further discuss the opportunities with Freeze Granulation on your powder system and read more on technology and we propose a Granulation Test of your powder system.

Freeze granulation vs spray drying
Freeze granulation vs spray drying

Spray drying compared with Freeze Granulation

What is the difference between spray drying and Freeze Granulation? For more info, please go to our Pros & Cons.

The best way to find out if Freeze Granulation is suitable for your material is to let us do a test granulation. Freeze Granulation will be more expensive than spray drying as it is a two-step process.  The relative difference depends on the scale and Freeze Granulation is more suitable for small or medium size batches where the demands on granule quality is high whereas spray drying is most suitable for large scale processing.

pros-cons

Interested in test-granulation of your material?

If you would like to test-granulate your powders or chemicals using Freeze Granulation, please contact us for details. You send your material and binders to us, we make the test-granulation using freeze granulation and then send the granulated material (granulaes) back to you for your evaluation and testing.

Freeze granulation is considered to be a natural tool in most kind of material processing and development where optimal material performance is to be reached. PowderPro provides test granulations to reduced cost to evaluate the performance regarding your specific material system and application.

When purchasing of granulation equipment, PowderPro provides help in concepts for suspension formulation/preparation and how to operate the equipment to achieve high yield and high-quality granules.

 

LS-2 - Lab-scale Freeze Granulator