Comparison of grinding difficulty between LFP and painting materials

Although both involve “grinding” solid particles in a liquid medium, their purposes, process requirements, and material properties are vastly different. Below, we will conduct a detailed comparison from several core dimensions.

Summary of core differences

Comparison Dimensions	Lithium iron phosphate (LiFePO₄) cathode material	Paint raw materials (taking titanium dioxide/pigment as an example)
Core objective	To achieve electrochemical activity , the goal is to achieve nano-sized , uniform , and spherical particles .	To achieve hiding power/tinting strength , the goal is to achieve micronized particles and uniform distribution in the paint film .
Target particle size	Submicron scale (100-500 nm) , and even some primary particles are required to be below 100 nm.	Micrometer scale (0.1 – 50 μm) , most high-end pigments can meet the requirements below 1 μm.
Process requirements	Extremely demanding . It requires precise control over particle size distribution and morphology, avoiding the introduction of impurities and lattice damage.	Relatively lenient . Primarily focuses on fineness, dispersion stability, and viscosity, and is not sensitive to morphology and crystal form damage.
Material properties	High hardness and high purity . The particles themselves are highly hard, and the grinding process must maintain the integrity of the crystal structure.	The hardness varies , ranging from softer organic pigments to harder inorganic pigments (such as titanium dioxide), but the overall requirements are lower than those for LFP.
Abrasive media	Ultra-high hardness grinding beads such as zirconia beads are commonly used to avoid contamination.	Commonly used materials include glass beads, zirconium silicate beads, and zirconium oxide beads , offering a wider range of choices.
Energy consumption and cost	Extremely high . Nanoscale grinding consumes enormous amounts of energy, and the equipment wear and maintenance costs are high.	Low . Mature industrial processes with controllable energy consumption and costs.
Main challenges	1. Particle coarsening and agglomeration 2. Introduction of elemental iron impurities 3. Crystal structure disruption 4. Energy consumption and cost control	1. Pigment flocculation 2. Grinding stability 3. Compatibility with resin systems

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Detailed analysis

1. The difficulty of grinding lithium iron phosphate (LiFePO₄)

As a cathode material for lithium-ion batteries, the electrochemical performance of lithium iron phosphate is highly dependent on the physical properties of the particles.

Nanoparticle size is key to performance : lithium ions and electrons diffuse slowly in lithium iron phosphate materials. Grinding particles to the nanoscale can significantly shorten the migration paths of ions and electrons, thereby improving the battery’s rate performance (fast charging capability) and capacity .

The ultimate pursuit of particle size and morphology :

Uniform particle size : Uneven particles can lead to uneven current distribution during charging and discharging, affecting battery life and safety.

Sphericalization : Spherical or near-spherical secondary particles have higher tap density, which is beneficial to improving the energy density of the battery.

Strict purity requirements : Battery materials have zero tolerance for metallic impurities (especially elemental iron). During the grinding process, the wear between the grinding beads (such as zirconia beads) and the inner wall of the equipment introduces impurities. These impurities can cause micro-short circuits inside the battery, seriously jeopardizing safety. Therefore, high-cost, high-hardness zirconia beads must be used, and the process must be strictly controlled.

Sensitivity to crystal structure : The mechanical energy generated by excessive grinding may damage the crystal structure of lithium iron phosphate, producing amorphous phases or defects, which will directly lead to capacity decay . Therefore, grinding is a process that is “just right,” both fine and not “damaged.”

Strong agglomeration effect of nanoparticles : Once particles reach the nanoscale, their surface energy is extremely high, and they will spontaneously agglomerate into larger secondary particles (i.e., the “re-agglomeration” phenomenon). Breaking this hard agglomeration requires very high energy, while preventing it from agglomerating again requires highly efficient dispersants and complex surface treatment processes.

In summary, the grinding of lithium iron phosphate is a “high-end manufacturing” process involving precision machining at the molecular/atomic scale. It requires finding the optimal balance between several conflicting constraints (fine grinding vs. structural integrity, high energy input vs. low impurity introduction), resulting in very high technical barriers and costs.

2. Difficulty in grinding paint raw materials

The grinding of paint (often referred to as “dispersion” in the industry) is primarily aimed at dispersing pigment particles into the continuous phase of resin and solvent to form a stable and uniform suspension system.

The target particle size is primarily for optical performance : once the pigment’s hiding power and tinting strength reach a certain fineness (typically below half the wavelength of visible light, i.e., about 200 nm), the improvement becomes less significant. Therefore, the vast majority of paint grinding aims to reach the micron level , with little need to penetrate the deep nanoscale.

Insensitive to morphology and crystal form : As long as the chemical properties of the pigment remain unchanged, minor changes in its crystal structure during grinding usually do not have a decisive impact on color and hiding power. Whether it is spherical or not is also not a key indicator.

The purity requirements are relatively low : although purity is still required, it is not as sensitive to metallic impurities at the ppm (parts per million) level as battery materials. Slight wear and impurity introduction from the grinding beads are generally within acceptable limits.

The core challenge is dispersion stability : the main difficulty in grinding lies in selecting a suitable dispersant to generate sufficient steric hindrance or electrostatic repulsion on the surface of pigment particles, preventing flocculation and sedimentation during storage and use . This process focuses more on surface chemistry than purely mechanical grinding.

In summary, paint grinding is a mature industrial process that focuses more on physical dispersion and surface modification . Its technical challenge lies in formulation and process stability, rather than the extreme pursuit of particle size and structure.

Grinding paint is like grinding sugar into fine powder ; as long as it’s fine enough and doesn’t clump, it’s perfect for baking.

Lithium iron phosphate grinding is akin to grinding diamonds into nanodiamond powder of a specific size and shape , requiring each particle to be free of cracks and without any other material debris being mixed in during the process. Its technological complexity and cost are completely incomparable.