Mesh standards are divided into 4 key production stages: flotation concentrate raw ore, pre-spheroidization intermediate powder, post-spheroidization semi-finished powder, and finished sieved anode graphite. Mesh number corresponds to screen aperture μm (standard US mesh).
1. Raw Flotation Concentrate (Front-End Raw Material Before Crushing)
This is the flake graphite feedstock delivered from mines, the starting material of anode production.
Industrial Standard Mesh Grades
- +50 mesh (≥300 μm flake) – mainstream battery-grade raw material
Aperture: 300 μm; ≥90% material retained on 50 mesh screen (large thick flakes) - Alternative feed: +80 mesh (180 μm fine flake), only for small-capacity 3C batteries
Mandatory Control Rule
- Reject ultra-coarse +32 mesh (>500 μm): Oversized flakes cannot be fully spheroidized, leave sharp edges, low tap density
- Reject fine -100 mesh (<150 μm): Excess fine flakes lead to high BET, low first Coulombic efficiency
Purpose
Large thick +50 mesh flakes are easy to shape into near-spherical particles with high tap density after spheroidization.
2. Pre-Spheroidization Coarse Grinding Powder (After Jet Milling, Before Shaping)
After primary crushing & air classification, raw flakes are ground into uniform medium powder for spheroidization shaping.
Mesh Specification
- Main target: -100 mesh ~ +200 mesh (75–150 μm)
Pass 100 mesh screen, retained on 200 mesh screen - Oversize removal: 80 mesh coarse screen to remove >180 μm unground large flakes
- Fines interception: 325 mesh fine screen to remove <44 μm ultra-fine dust
Screening Standard
- Oversize (>180 μm) residue ≤2% for re-grinding
- Ultra-fine fines (<44 μm) yield controlled ≤10%
3. Post-Spheroidization Semi-Finished Powder (Core Sieving Stage)
After mechanical spheroidization, near-spherical graphite requires multi-layer ultrasonic screening to cut oversized coarse particles and excess ultrafine powder (critical for battery safety & tap density).
Double-Layer Screen Mesh Configuration
- Upper coarse screen: 200 mesh (75 μm)
Remove all oversized particles >75 μm; residue on 200 mesh ≤0.5% (coarse particles pierce separator during cell winding) - Lower fine screen: 325 mesh (44 μm)
Intercept ultra-fine powder <44 μm; pass-through fine fraction ≤15% (too many fines raise BET, increase SEI film loss)
Target PSD Matching Mesh
Commercial battery spherical graphite D50 =15–22 μm, fully passes 325 mesh screen, main fraction retained between 325–500 mesh.
- EV power battery: D50 18–22 μm → primary grading 200–325 mesh
- 3C consumer battery: D50 15–18 μm → primary grading 325–500 mesh
4. Final Finished Product Sieving (After Acid Purification & Drying)
Fine polishing screening before finished product silo homogenization, removes agglomerates generated during acid washing and drying.
Mesh Selection
- Standard power battery finished screen: 400 mesh (38 μm)
- High-rate fast-charging fine graphite: 500 mesh (25 μm)
Acceptance Index
- 100% pass through 200 mesh screen; residual oversize on 200 mesh = 0
- Oversize agglomerates >75 μm completely eliminated
5. Mesh Aperture & Particle Size Conversion Table (US Standard Mesh)
| Mesh Number | Aperture (μm) | Application Stage |
|---|---|---|
| 50 mesh | 300 μm | Mine flotation concentrate raw material |
| 100 mesh | 150 μm | Pre-spheroidization coarse powder lower limit |
| 200 mesh | 75 μm | Post-spheroidization upper coarse cutoff |
| 325 mesh | 44 μm | Post-spheroidization lower fine cutoff |
| 400 mesh | 38 μm | EV finished graphite fine screening |
| 500 mesh | 25 μm | 3C small battery fine graphite |
6. Critical Mesh Control Principles for Battery Performance
- Too many particles retained on 200 mesh (>75 μm): Sharp angular particles, risk of separator puncture, uneven electrode coating
- Excess powder passing 325 mesh (<44 μm): High specific surface area, low initial Coulombic efficiency, severe electrolyte consumption
- Raw material <+50 mesh fine flake feed: Low tap density after spheroidization, reduced volumetric energy density
- Must use ultrasonic vibrating screen for ≥300 mesh fine grading: Flaky graphite easily blocks standard screen cloth without ultrasonic anti-blocking function
7. Full Process Mesh Flow Summary
+50 mesh flotation concentrate → 80 mesh coarse screening → grind to -100~+200 mesh pre-spheroid powder → spheroidization shaping → double-layer 200 mesh + 325 mesh ultrasonic screening → acid purification → final 400 mesh polishing screening → finished spherical graphite anode material
