Introduction of Key Technology of Cathode Materials --- Ternary Cathode

 I. Material systems and basic theory

1.1 Chemical composition and crystal structure of trivalent materials

The crystal structure of the ternary cathode materials (lini _ xCo _ yMn _ zO _ 2 or lini _ xCo _ yAl _ zO _ 2) is a lamellar a-NaFeO _ 2 type, with space group R-3m. Nickel cobalt manganese (aluminum) ions occupy the 3a position, lithium ions occupy the 3b position, and oxygen ions occupy the 6c position. Nickel content directly affects:

Specific capacity : Ni²+ / Ni⁴+ redox couple provides the main capacity （ about 15-20mAh / g per 10% increase in Ni content ）

Structural stability : High Ni material （ Ni ≥ 80 % ） is prone to H2 → H3 phase transition , resulting in lattice distortion rate of more than 6 %

Thermal stability : Thermal decomposition temperature decreases by about 15 ℃ per 10 % increase in nickel content

1.2 Technology comparison of low- and medium-nickel and high-nickel systems

System type	Typical Model	Nickel content	Specific capacity (mAh / g)	Heat out of control temperature
Medium and Low Nickel	NCM523	50-70%	155-175	220-250℃
	NCM622		165-185
High Nickel	NCM811	≥80%	195-220	180-210℃
	NCA90		200-220

II. Deep analysis of precursor preparation processes

2.1 Cohesion reaction mechanism

Reactions that occur in a continuously stirred reactor (CSTR):

Ni²+ + Co²+ + Mn²+ + 2OH⁻ → (NiCoMn)(OH)₂↓

Four phases of control:

Nucleation stage （0-30min）： pHThe value jumps to more than 10.5, forming 5-20nm crystal nuclei

Growth stage （ 1-10h ） : Ostwald ripening dominates , D50 increases to 3-5μm

Densification stage （ 10-20h ） : surface energy is controlled by ammonia concentration , densification density is 1.8-2.2g / cm3

Curing stage （ 2-4h ） : Eliminate internal stress , reduce BET surface area to 10-15m2 / g

2.2 Critical equipment and parameter matrix

1 Level 5 serial reactor system (specialty for high nickel):

Bus Station	Temperature control	PH range	Ammonia concentration (g / L)	Mixing power (kW / m3)
1#	55±0.5℃	11.8-12.2	2.0-2.5	3.5-4.0
2#	58±0.3℃	11.5-11.8	1.8-2.2	4.0-4.5
3#	60±0.2℃	11.2-11.5	1.5-1.8	4.5-5.0
4#	62±0.2℃	10.8-11.2	1.0-1.5	5.0-5.5
5#	65±0.1℃	10.5-10.8	0.5-1.0	5.5-6.0

2 Parameters of medium and low nickel materials:

Single reactor reaction time : 8-12h

Particle distribution: D10=2.5μm, D50=4.5μm, D90=8.0μm

Specific surface area : 12-18m2 / g

III. Core technologies of lithium blending and sintering processes

3.1 Lithium source selection and rationing calculation

The formula for the lithium overload coefficient:

Li / (Ni + Co + Mn) = 1.05-1.10 (low and medium nickel)

Li/(Ni+Co+Al) = 1.08-1.15（高镍）

Mixed manufacturing process comparison:

parameter	Dry method of mixing		Wet mixing
equipment	V-mixer	High Speed Hybrid	Planetary ball milling machine
speed	15-25rpm	200-500rpm	200-300rpm
time	2-4h	0.5-1h	4-6h
homogeneity	RSD≥5%	RSD≥5%	RSD≤2%
System of application	Medium and Low Nickel	System-wide	High Nickel

3.2 Sintering Dynamics and Equipment Selection

Push Plate Kiln vs Roller Kiln vs Return Kiln:

Indicator	Crane kiln (low and medium nickel)	Crane kilns (whole system)	Reverse kiln (high nickel)
Temperature uniformity	±5℃	±1℃	±1℃
Climate control	air	Air or oxygen	O2 concentration 5-15%
Rate of heating	3-5 °C/min	3-5 °C/min	1-2 °C/min
production capacity	200kg / batch	300kg / batch	500kg / day
Lithium residual control	1.2-1.8%	1.0-2.0%	0.8-1.2%

Typical sintering curves:

NCM622 : Room temperature → 400 ℃ （2h） → 750 ℃ （12h） → furnace cooling

NCM811： Room temperature → 300 ℃ (2h, O2 5%) → 500 ℃ (3h, O210%) → 750 ℃ (10h, O215%) → rapid cooling

IV. Post-treatment and surface modification techniques

4.1 Crushing grading process

Parameters for jet stream crushing machines:

Working pressure : 0.8-1.2MPa

Speed of classification wheel : 4000-8000rpm

D50 control accuracy : ± 0.3 μm

Production capacity : 100-300kg/h

Rating criteria:

Indicator	Low and medium nickel requirements	High nickel requirements
D10	2. 0-3.0μm	3. 0-4.0μm
D50	4. 0-5.0μm	5. 0-6.5μm
D90	10μm	12μm
Length coefficient	<1.2	<1.0

4.2 Surface cladding techniques

Wet cladding process:

Coating agent : AlPO₄ , Li₂TiO₃ , LiAlO₂

Reaction conditions : solid-liquid ratio 1 : 3 , 80 ℃ , pH = 9-10 , stirring for 2 h

Coating thickness : 2-5nm

Coating amount : 0.5-2.0wt %

Atomic layer deposition (ALD) technology:

Deposited material : Al₂O₃ , TiO₂

Deposition rate : 0.1nm / cycle

Vacuum of equipment: 10⁻³ Pa

Film uniformity : > 95 %

V. Key performance indicators and test methods

5.1 Electrochemical properties

Test projects	Methodological standards	Typical values of medium and low nickel	High nickel target value
First efficiency	GB/T 30835	85-88%	88-92%
1C cycle life	25℃,2.8-4.3V	1500 weeks ≥ 80%	1000 weeks ≥ 90%
High temperature performance	Storage at 45 ° C for 7 days	Capacity maintained at ≥ 95%	≥92%
DCIR elongation	1C cycle 500 weeks	<25%	<15%

5.2 Physical properties

parameter	Test equipment	Control standards
Vibration density	Hall Flow Rate Meter	≥2.2g/cm³
Compared to surface area	BET nitrogen sorbent	0.3-0.8m²/g
Magnetic foreign objects	High-gradient magnetic sorting machine	≤100ppb
Water content	Calffaut Water Meter	≤500ppm

VI. Core influencing factors and control strategies

6.1 Quality control of raw materials

Elements of impurities	Allowable upper limit (ppm)	Effect mechanisms
Na	<50	Blocking the diffusion of lithium ions
Ca	<20	Generating a LiCaPO4 Blocking Channel
Fe	<10	Catalyst for Electrolyte Decomposition
S	<100	Formation of Li2SO4 increases interface impedance

6.2 Tolerance analysis of process parameters

working procedure	Key parameters	Allowable range of volatility	Impact on performance
Together, we settled	PH value	±0.05	★★★★★
	Ammonia Concentration	±0.1g/L	★★★★☆
Sinter	Maximum temperature	±3℃	★★★★★
	Oxygen Concentration	±1vol%	★★★★☆
smash	Level wheel speed	±50rpm	★★★☆☆

VII. Frontier technologies and development trends

7.1 Breakthroughs in monocrystalline technology

Synthesis process : Melt salt method （ LiNO₃-LiOH co-melting system ）

Single crystal size : 3-5μm

Improved cycle performance : 1C / 2000 cycles > 88 % capacity retention

7.2 Concentration gradient materials

Composition of nuclear layer : Ni80Co10Mn10

Shell composition : Ni50Co20Mn30

Thickness of transition layer : 200-500nm

Improved thermal stability : DSC peak temperature increased by 30 ℃

7.3 Solid-state battery adaptation technology

Interface modification : LiNbO₃ / LiTaO₃ coating

Sintering temperature optimization : 850-950 ℃

Ion conductivity: > 10⁻⁴ S/cm （Matching with sulfide electrolytes）

VIII. CONCLUSIONS

The industrial production of trivalent cathode materials has formed a complete technical system from raw material refinement (metal purity ≥ 99.95%), precursor synthesis (particle size CV value < 10%), to sintering process (oxygen pressure closed-loop control).

For high-nickel materials, it is necessary to establish a process-wide inert gas protection system (dew point ≤ -40 ° C, oxygen content ≤ 10 ppm), and to introduce online laser particle analysis (sampling every 30 seconds) and real-time XRD monitoring (fluctuation of lattice parameters a and c values ≤ 0.005Å per batch detection).

With the maturity of technologies such as multi-element mixing (Mg / Ti / Zr co-mixing) and microstructure regulation (secondary spherical porosity 15-20%), triad materials are continuously evolving towards higher energy density (≥ 300 Wh / kg) and longer cycle life (≥ 1500 weeks).

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