What is the insulation performance of plasma sprayed alumina coating on lithium battery equipment
Information summary：The insulation performance of plasma sprayed alumina (Al ? O3) coating used in lithium battery equipment is excellent, and its core advantage lies in the high insulation properties of alumina itself and the dense structure endowed by plasma spraying process. The following provides a detailed explanation from the aspects of material properties, coating performance, influencing factors, and applicat
The insulation performance of plasma sprayed alumina (Al ? O3) coating used in lithium battery equipment is excellent, and its core advantage lies in the high insulation properties of alumina itself and the dense structure endowed by plasma spraying process. The following provides a detailed explanation from the aspects of material properties, coating performance, influencing factors, and application scenarios:
1、 Basic insulation characteristics of alumina coating
1. Intrinsic insulation properties of materials
Aluminum oxide (α - Al ? O3, also known as corundum) is a typical inorganic insulating material with a resistivity of ≥ 1 × 10 1?Ω· cm at room temperature and a breakdown field strength of ≥ 10 MV/m, far exceeding most metal and organic insulating materials (such as epoxy resin with a breakdown field strength of about 30 kV/mm).
High temperature insulation resistance: The volume resistivity can still reach 1 × 10 ΩΩ· cm at 200 ℃, suitable for the temperature rise environment caused by charging and discharging in lithium battery equipment (working temperature is usually ≤ 100 ℃).
2. Enhancement of insulation by plasma spraying process
Coating Density: Plasma spraying uses high-temperature plasma (temperature ≥ 10000 ℃) to melt and spray alumina powder onto the surface of the substrate, forming a dense coating with a porosity of ≤ 1%, to avoid insulation failure caused by pores (for every 1% increase in porosity, the breakdown field strength decreases by about 5%).
Crystal structure optimization: During the spraying process, the alumina powder rapidly solidifies, forming columnar or equiaxed crystal structures with clear grain boundaries and few defects, reducing the migration path of charge carriers and further improving insulation performance.
2、 Insulation application scenarios in lithium battery equipment
1. Insulation protection for polarizer processing equipment
Application objects: metal rollers, molds, etc. of roller presses and slitting machines.
effect:
Prevent short circuits between the electrode plates (positive and negative electrode materials) and the metal roller to avoid equipment failure or battery short circuit risks;
The coating surface is smooth (roughness Ra ≤ 1 μ m), reducing electrode scratches, and the insulation layer can withstand electrolyte corrosion (such as LiPF ? electrolyte stability ≥ 1000 hours).
2. Insulation treatment of battery shell and cover plate
Application scenarios: Insulation coating on the inner wall of aluminum shell batteries and cylindrical battery cover plates.
Advantages:
Replace traditional PVC insulation sheets, with a coating substrate bonding strength of ≥ 50 MPa (better adhesion than adhesive insulation sheets), to avoid detachment during long-term use;
Ultra thin coating (20-30 μ m) saves internal space of the battery and improves energy density (5% higher space utilization rate than traditional insulation solutions).
3. Insulation of battery cell assembly tooling
Application objects: metal fixtures and positioning blocks for laminating machines and winding machines.
Key Performance:
Organic solvents (such as NMP) used in the production of lithium resistant batteries ensure that the coating does not swell or peel off;
High insulation prevents short circuits in the battery cells, while the coating hardness is ≥ HV1000 and the wear resistance life is ≥ 100000 cycles.
3、 Key factors and optimization measures affecting insulation performance
1. Coating thickness and uniformity
Coating thickness: In lithium battery equipment, a thickness of 50-100 μ m is usually chosen. Thin coating is prone to breakdown (such as a 20% decrease in breakdown field strength when the thickness is less than 20 μ m), while thick coating increases thermal resistance (the thermal conductivity of alumina is about 30 W/m · K, and the thickness needs to be controlled to balance insulation and heat dissipation).
Uniformity control: Using computer-controlled plasma spraying trajectory (such as reciprocating scanning speed of 500-1000 mm/s) to ensure coating thickness deviation of ≤± 5%.
2. Surface pretreatment of the substrate
Before spraying, the substrate needs to be sandblasted and roughened (such as using Al ? O3 sand particles for sandblasting, with a roughness of Ra 5-10 μ m) to enhance coating adhesion and avoid partial discharge caused by interface delamination (PDIV ≥ 300V).
3. Post processing technology
High temperature annealing: After spraying, anneal at 600-800 ℃ for 2 hours to reduce internal stress in the coating, further reduce porosity (which can be reduced to below 0.5%), and improve insulation stability.
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