China Lithium Iron Phosphate Battery Cell Discretization Standard 2025
“For every 1% increase in the accuracy of capacity separation, the life of the battery pack will be extended by 200 cycles” — the industry consensus reveals the value leverage effect of this process. As battery engineers, we will penetrate the appearance of the standard, and directly hit the lithium iron phosphate battery cell capacitance process control points.
I.The lithium iron phosphate battery capacity control environment: data accuracy of the life and death line
Temperature precision control
Standard requirements: 25 ± 2 ℃, but the power core needs to be upgraded to 25 ± 0.5 ℃ (module-level grouping requirements)
Temperature compensation technology: Anhui DEYI 2025 patented capacity calibration equations, through the multi-temperature node fitting to eliminate the impact of temperature drift
Deadly impact: 30 ℃ environment capacity than 25 ℃ capacity of the capacity of the false high 4.2% (LFP material characteristics of the decision)4
Humidity and cleanliness
Humidity control: 45-75% RH is not a fixed value, the temperature is not a fixed value. 75% RH is not a fixed value, after the injection of liquid core needs <30% RH (anti-electrolyte hydrolysis)
Dust control: coating stage metal impurities (such as Fe> 50ppm) will lead to micro-short-circuit self-discharge rate soared 300
II.Lithium iron phosphate battery charging and discharging process: the precision dance of activation and screening
New generation of four-stage capacitor separation process (compare with traditional process)
| point | Innovative processes | Traditional Craftsmanship Defects | engineering value |
|---|---|---|---|
| preprocessing | 0.2C charging and discharging 2 times +45℃ aging 24h | Insufficient activation by a single small current | 40% improvement in SEI film uniformity |
| deep discharge | 0.6C→0.1C→0.05C阶0.6C→0.1C→0.05C step discharge | 0.5C one-step discharge to 2.0V | Eliminates polarization differences and improves voltage consistency to 99 percent |
| SOC balance | Constant voltage 3.0V small current charging | Full charge state (3.65V) at standstill | 80% reduction in flatulence, safe turnaround |
| verification loop | Dynamic adjustment of current (0.5C/1C dual mode) | Fixed Current Test | Detection of cells with abnormal multiplier performance |
Key Parameter Prohibited Areas
Overcharge protection: >3.65V will trigger LFP lattice collapse, internal resistance will increase by 15% permanently.
Over-discharge protection: <2.0V will lead to dissolution of copper collector, increasing the risk of self-discharge rate exceeding the standard by 8 times.
III. Consistency Screening: Multi-dimensional Parameter Matrix
1. Capacity grading
Basic standard: 95-105% of nominal capacity
Vehicle-grade requirements: ±2% bandwidth (e.g., 100Ah cells are only allowed to be 98-102Ah)
Innovative method: based on K-value clustering analysis (OCV24h-OCV0h), excluding self-discharge anomalies
2. Internal resistance matching
A\Test –> 1C discharge 10s take –> C[ACIR@1kHz]
B & C –> D[3D heat map clustering]
D –> E[Exclude ±3σ outer cells]
Note: Power battery pack requires internal resistance difference ≤ 3mΩ (common energy storage ≤ 10mΩ)
3.Voltage consistency
Voltage difference after static: ≤50mV (module level) → ≤10mV (VDA standard)
Dynamic pressure difference monitoring: Charge/discharge end pressure difference >100mV battery cell is directly scrapped.
IV.Engineering-level considerations: mass production yield guardian manual
1. Equipment Calibration
Current sensor: monthly calibration with 0.05 level shunt, error > ± 0.5% immediately stop the line
Voltage acquisition: 24bit ADC chip (LTC2440), sampling jitter <1mV
2. Safety prevention and control
Thermal runaway warning:
First-level alarm: temperature rise rate > 1 ℃ / s → trigger nitrogen fire
Second-level alarm: single body temperature difference > 5 ℃ → automatically cut off the circuit
Explosion-proof design:
sub-capacity cabinet integrated pressure sensor (> 15kPa relief valve start)
3. Data-driven sorting
Establishment of electric core “digital twin”:
Sorting Strategy: Priority Matching Capacity – Internal Resistance – Self-Discharge Same Cluster Cells
V.The fusion of cutting-edge technology: sub-capacity 4.0 era
1.Temperature-capacity compensation algorithm
Anhui get one 2025 patent core equation:
where k is the material coefficient and ΔT is the deviation from 25°C of the production line capacity separation temperature.
2.Dynamic Threshold Adjustment
Aging core: capacity bandwidth is relaxed to 90-110% after 300 cycles
Low temperature application: -20℃ ambient discharge capacity >85% of nominal value4
3.AI pre-sorting system
Input: CC-CV curve shape of chemicalization → Prediction of capacity-sorting pass rate (accuracy > 92%)
Engineer’s quick checklist: key process red line
| parameters | Consumer Electronics Standards | Vehicle-grade standards | Consequences of failure |
|---|---|---|---|
| capacity bandwidth | 95-105% | 98-102% | 30% degradation of module usable capacity |
| Internal Resistance Extreme Differences | ≤10mΩ | ≤3mΩ | Risk of thermal runaway increases fivefold |
| Standstill voltage difference | ≤50mV | ≤10mV | BMS equalization failure |
| K value screening threshold | ≤5mV/day | ≤2mV/day | 3-month capacity jumps 15% |
Sorting is not a simple charging and discharging, but the first performance finalization of the battery cell life cycle. Mastering the three core elements of environment control, multi-stage activation dynamics, and digital twin sorting is the only way to forge a highly consistent battery pack.
