The standard is divided into 3 stages step by step: flotation concentrate (primary raw material), spheroidized intermediate material (pre-leaching raw material), finished battery-grade graphite (after acid purification), based on GB/T 24533-2019 Lithium-ion Battery Graphite Anode Materials and industrial mass production specifications.
1. Flotation Concentrate (Original Raw Ore After Froth Flotation)
This is the primary incoming raw material for graphite anode factories, before spheroidization and acid leaching.
Mandatory Fixed Carbon Standard
- Minimum qualified grade: ≥94.0% fixed carbon (high-carbon flake graphite LG grade per GB/T 3518)
- Optimal industrial feed: 94.5% ~ 95.5% fixed carbon
- Unacceptable raw material: <94% C
- 92%–94% medium-carbon graphite: Excessive silicate gangue, drastically increases acid consumption, unstable purification purity, only used for low-end energy storage with double-cycle leaching
- <92% C: High impurity embedding, acid leaching cannot reach battery-grade purity, abandoned for lithium anode production
Supporting Control Index
Ash content ≤6.0%, Si/Fe bulk gangue evenly distributed, no massive quartz agglomerates.
Reason for the ≥94% threshold: Multi-stage flotation can only enrich ore (4%–30% C) to 94%–96%; lower carbon concentrate carries too much embedded silicate, leading to excessive HF consumption and inconsistent post-leaching purity.
2. Spheroidized Graphite (Pre-Acid Leaching Intermediate Raw Material)
After crushing, spheroidization shaping, multi-stage magnetic separation and drying, this material directly enters mixed acid purification.
Fixed Carbon Requirement
- Standard minimum: ≥94.0%
- Mass production control target: 94.8% ~ 95.8%
- Consistency rule: Batch-to-batch fixed carbon fluctuation ≤±0.3%
Key logic: Spheroidization only changes particle morphology, does not remove chemical impurities; carbon content basically consistent with flotation concentrate. If carbon drops below 94% after shaping, coarse gangue screening is insufficient, must re-sieve before leaching.
3. Finished Battery-Grade Natural Graphite (After Acid Purification, Final Anode Raw Material)
National Standard GB/T 24533-2019 Hard Requirement
Fixed carbon ≥99.5% as the lowest threshold for lithium-ion anode graphite.
Industrial sub-grades by application scenario:
| Grade Classification | Fixed Carbon Requirement | Application Scenario | Acid Purification Route |
|---|---|---|---|
| Energy storage low-power grade | ≥99.90% | Energy storage, consumer small batteries | Single-cycle mixed acid leaching |
| EV power battery mainstream grade | ≥99.95% | Electric vehicle power cells | Double-cycle mixed acid leaching / alkali-acid combined leaching |
| Ultra-high purity fast-charging grade | ≥99.99% | High-rate fast charge, premium power batteries | Acid leaching + high-temperature thermal deep purification |
Corresponding Ash & Impurity Limits
- ≥99.90% C: Total ash ≤0.10%, total metal impurities ≤20 ppm
- ≥99.95% C: Total ash ≤0.05%, Si ≤5 ppm, Fe ≤10 ppm
- ≥99.99% C: Total ash ≤0.01%, total metal impurities ≤10 ppm, Si ≤1 ppm
4. Why Raw Material Carbon Content Must Be Controlled Above 94%
- Purification cost control
Each 1% drop in flotation concentrate carbon increases HF acid consumption by ~15%, raises hazardous fluoride waste output sharply. - Purity consistency guarantee
Raw material with C <94% has uneven embedded silicate; acid leaching produces large batch-to-batch purity fluctuation, cannot stabilize finished product ≥99.90% C. - Electrochemical performance stability
Residual silicate impurities cause battery gas swelling, low first-cycle Coulombic efficiency, fast cycle attenuation. - Production yield
Flotation concentrate <94% C leads to 8%–15% lower finished graphite yield after acid washing and filtration.
5. Common Industrial Acceptance Rules Summary
- Incoming flotation raw graphite: Fixed carbon ≥94.0% (optimal 94.5–95.5%)
- Spheroidized powder before acid leaching: Fixed carbon ≥94.0%, fluctuation ≤±0.3%
- Acid-purified finished anode material: Minimum 99.5% C; power battery mainstream ≥99.95%, high-end fast-charge ≥99.99%
