The insulation design of lithium‑battery packs—particularly high‑voltage power battery modules and energy‑storage systems—serves as the first line of defense in ensuring system safety and preventing electric shock and thermal runaway. As voltage platforms evolve toward 800 V or even higher (as seen in new‑energy vehicles and grid‑scale energy storage stations), the reliability and lightweighting of insulation solutions have become increasingly critical.

The following from Design principles, common materials, key processes, and testing and validation A brief discussion from four perspectives.

I. Core Design Principles

Basic insulation + supplementary/reinforced insulation According to standards such as IEC 60664, high-voltage components must be provided with double protection. For example, the aluminum case of a battery cell is coated with an insulating layer (basic insulation), and additional insulation is achieved by using insulating partitions between modules (supplementary insulation).

Creepage Distance and Electrical Clearance : Calculate the minimum creepage distance based on the system’s maximum operating voltage (e.g., 1500 V DC), the pollution degree (e.g., PD2 for indoor energy storage systems), and the material group (CTI value). Corrections are also required for high altitudes (>2000 m).

Thermal management compatibility Insulating materials must withstand battery-generated heat and potential localized overheating, while also not impeding effective heat dissipation (e.g., thermally conductive pads that provide both thermal conductivity and electrical insulation).

Aging resistance and chemical compatibility Electrolyte leakage, coolant, salt spray, and humid environments can all degrade insulating materials; long-term compatibility must be assessed.

II. Common Insulation Schemes and Materials

It is worth noting that In cell-to-module (CTM) or cell-to-pack (CTP) designs, a combination of structural adhesive and insulating film is commonly employed. The structural adhesive—typically modified epoxy or polyurethane—provides both bonding and mechanical fixation while also serving as an effective insulator, thereby simplifying the use of conventional insulating components.

III. Key Processes and Structural Details

Rounded Corners and Chamfers : The battery tabs and busbar edges must be rounded (R ≥ 0.5 mm) to prevent tip discharge or puncture of the insulation layer.

Potting and Overmolding : The BMS circuit board, high-voltage relays, and other sensitive components are fully encapsulated to provide insulation, vibration resistance, and moisture protection.

Insulation Coating Thickness Control When using electrostatic powder coating, ensure uniform coating coverage at edges, corners, and bolt holes (≥50 μm) to prevent localized thinning.

Electrochemical corrosion prevention : At the junctions of dissimilar metals (copper/aluminum), insulating shims or conductive grease must be used to prevent electrochemical corrosion beneath the insulation layer caused by potential differences.

IV. Common Failure Modes and Test Verification

1. Primary failure modes:

Dielectric breakdown : Caused by metal burrs, contamination from conductive particles, and moisture condensation.

Creepage flashover : In environments with contamination or condensation, surface discharge occurs along the edge of the insulator.

Aging and embrittlement : Temperature cycling and vibration cause the blue film to crack, exposing the aluminum housing.

2. Key test items (refer to GB/T 38031 and UL 2580):

Insulation Resistance Test : Use a 1000 V/500 V megohmmeter; the insulation resistance of the entire package must be ≥ 1 MΩ (the typical design target is > 100 MΩ).

Withstand Voltage Test : Apply 2 times the rated voltage plus 1000 V (AC or DC), with leakage current below the set threshold (e.g., 5 mA), and maintain this condition for 1 minute without flashover.

Partial Discharge Testing : Particularly important for high-voltage systems (>700 V), it detects even the smallest insulation defects.

Damp-Heat Cycling + Insulation Testing : Immediately measure insulation after simulating a high-humidity environment (e.g., 95% RH, 55°C) to assess the impact of moisture.

Insulation after thermal aging and vibration : After storage at high temperature (85–105°C) for 1,000 hours, subject the component to mechanical vibration and re‑test its insulation integrity.

V. Emerging Trends and Challenges

Dry-Electrode Technology and Solid-State Batteries : There is no risk of liquid electrolyte leakage, but the thermal stability of the separator and the interfacial adhesion are required to be higher.

The 800V platform’s sensitivity to partial discharge : A higher voltage gradient makes it easier for partial discharges to occur in the tiny air gaps within the insulation, necessitating a higher‑quality bubble‑free potting process.

Integrated insulation structure : By injection molding with plastics such as PA6+GF30, multiple insulating components are integrated into a single 3D‑structured part, reducing assembly errors and costs.

Online Insulation Monitoring Integrate insulation‑monitoring functionality into the BMS (e.g., low‑frequency pulse injection) to provide real-time alerts when insulation resistance drops.

Summary and Recommendations

Ultimately, there is no one-size-fits-all insulation solution. It must be tailored to the battery’s… Shape (cylindrical/square/padded), voltage, application environment (automotive/energy storage/outdoor), production volume Come and customize your own combination. But the core principle remains unchanged: Redundant design, avoidance of single points of failure, and end-to-end testability. 。