Introduction

During the high-temperature sintering process of cathode and anode materials for lithium batteries, saggers serve as containers for powdered materials, and their quality directly determines product purity and production efficiency. With the explosive growth of the new energy vehicle industry, production lines for cathode materials such as lithium iron phosphate (LFP) and ternary materials have imposed increasingly stringent requirements on saggers in terms of corrosion resistance, thermal shock resistance, and service life. At present, advanced ceramic saggers have become an indispensable core consumable in the sintering of lithium battery materials.

Technical Principles and Material Systems

      Saggers for lithium battery sintering are primarily subjected to high temperatures below 1200°C, chemical attack from alkaline lithium salts, and thermal shock from repeated heating and cooling cycles. Depending on the material being sintered, the choice of sagger material varies significantly.

     Mullite-based saggers** are the mainstream choice for sintering ternary materials (NCM/NCA). They have an Al₂O₃ content of approximately 58% and an Fe₂O₃ content controlled below 0.5%, effectively preventing metal contamination. For high-nickel ternary materials (NCM811), high-performance products capable of withstanding temperatures ≥1200°C with a thermal expansion coefficient ≤3.5×10⁻⁶/°C are required.

     Graphite saggers** are widely used in the sintering of lithium iron phosphate (LFP) and some anode materials. High-purity graphite (C% ≥ 99.9%) offers excellent thermal conductivity—ranking first among non-metallic materials—which ensures a uniform temperature distribution within roller kilns.

      Clay-fused silica saggers** were once widely used in high-temperature fast-firing processes, with their core advantage being excellent thermal shock resistance. However, studies have shown that during use, the crystallization transformation of fused silica into cristobalite, along with the migration of impurity ions such as potassium and sodium, leads to increased internal stress and detachment of aggregate from the bonding phase, ultimately resulting in cracking failure.

Manufacturing Processes and Quality Control

   The manufacture of advanced ceramic saggers involves raw material batching, mixing and granulation, press forming, drying, high-temperature sintering, precision machining, and final inspection and packaging. For mullite saggers, the introduction of reinforcing agents such as POSS-modified phenolic resin and boron oxide can significantly enhance the corrosion resistance and mechanical strength of the green body.

Key quality indicators include:

- Thermal shock resistance： Must withstand ≥100 rapid thermal cycles (1200°C ↔ room temperature) without cracking
- Chemical stability：No reaction with cathode materials at high temperatures; Fe and Ni content ≤50 ppm
- Dimensional accuracy：Allowable tolerance of ±0.5 mm to ensure compatibility with kiln loading systems

Industry standard T/ZGTS 008-2024 stipulates that saggers must pass high-temperature load softening tests (≥1250°C), achieve flexural strength ≥30 MPa, and meet heavy metal migration detection requirements.

Application Practices and Lifecycle Management

In actual production, the service life of graphite saggers for LFP sintering is typically 15–100 cycles, while mullite saggers for ternary materials last 25–50 cycles, depending on loading capacity, heating profiles, and cleaning maintenance frequency.

Usage precautions include:

- Loading volume should not exceed 75%–80% of the sagger capacity to avoid sidewall cracking due to thermal expansion
- Residual material should be removed every 5–10 sintering cycles, using ultrasonic cleaning combined with nitrogen purging
- Saggers should be scrapped when surface erosion exceeds 25% or weight loss reaches ≥10%

Xiamen Zhongke Jinyuan employs proprietary high-temperature coatings and a double-layer material technology, extending sagger service life by more than 30% above the industry average. The resulting smooth surface resists spalling and material adhesion, effectively reducing the "lithium absorption" phenomenon.

Conclusion

The selection of ceramic saggers requires comprehensive consideration of the type of sintering material, temperature regime, cost budget, and lifespan requirements. From mullite to graphite, and from cordierite to fused silica, continuous advances in materials science are steadily reducing the per-unit consumable cost in lithium battery production.