Hexoloy SE Rollers for Lithium-Ion Battery Process

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Li-ion batteries are ubiquitous in handheld electronics, medical equipment, power tools and many other products. Suppliers are responding on several fronts by developing new battery chemistries for greater energy density, boosting recycling efforts and expanding battery production.
 
Multiple cathode chemistries are available to provide the optimum combination of energy density, cost and safety for the target application. Some of the popular formulations include:
 
  • LFP — lithium iron phosphate (LiFePO4)
  • NMC — lithium nickel cobalt manganese oxide (LiNiCoMnO2)
  • LCO — lithium cobalt oxide (LiCoO2)
  • NCA — lithium nickel cobalt aluminum oxide (LiNiCoAlO2)
  • LMO — lithium manganese oxide (LiMn2O4)
Roller hearth kilns (RHK) operating at high temperatures are crucial in the manufacturing of cathode powders. An RHK is a continuously firing furnace in which a hearth made of rotating rollers moves products through the kiln. 
 
In the face of burgeoning demand, manufacturers are boosting production with new, larger RHKs that require larger diameter and longer rollers compared to earlier versions of the kilns. These rollers must also demonstrate long service life and high reliability with large loads.
 
Saint-Gobain Performance Ceramics & Refractories’ Hexoloy® SE is a self-bonded fine-grained (less than 10 µm) silicon carbide (SiC) material that combines exceptional strength at high-temperature operation with high chemical corrosion resistance. Here are five reasons why Hexoloy® material is ideally suited for RHKs in Li-ion battery manufacturing applications.
 
  1. High temperature stability. RHK temperatures can reach up to 1200° C (2192° F) during the calcination process for cathodes. Hexoloy® SE material’s single-phase composition allows it to operate up to 1600° C in air and results in an extremely low coefficient of thermal expansion (4.02 x 10-6/°C), making it very stable in severe-environment applications.
     
  2. High thermal conductivity. Hexoloy® SE materials’ high thermal conductivity (35 W/mK at 1200° C) makes it very resistant to thermal shock.
     
  3. Extreme hardness. Hexoloy® SE SiC is one of the hardest high-performance materials available and is 50% harder than tungsten carbide. Its density is over 95% of theoretical and it is essentially impervious without the use of any impregnants, which means no contamination in high-purity applications. Minimizing contamination is critical to high-quality battery manufacturing: metallic particles are especially damaging and can produce unwanted reactions and shorts in finished batteries.
     
  4. High strength. Hexoloy® SE SiC rollers offer higher load bearing capability than silicon-infiltrated silicon carbide (SiSiC); therefore, these rollers are typically offered with thinner walls. In large RHKs, Hexoloy® SE SiC rollers can measure up to 50 mm in diameter with 7 to 8 mm thick walls in lengths up to 3350 mm. The ability to achieve the same strength with a lighter, thinner roller allows the designer to increase energy efficiency with lower-cost smaller motors that use less power.
     
  5. Virtually universal corrosion resistance. High corrosion resistance gives longer product life, lowers maintenance costs and increases uptime. RHKs in battery manufacturing operate with a variety of gases: air, oxygen, nitrogen, nitrogen plus hydrogen and CO2. In addition, some of the new cathode powders include corrosive chemistries: the RHK must be resistant to all of the various gases and formulations.
 
The many desirable properties of Hexoloy® SE SiC make it the clear choice for use in RHKs in Li-ion battery manufacturing production lines. 
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