TL;DR:
- Lithium battery insulation tape is not one product but four: tab tape (protects welded tabs), termination tape (fixes the jellyroll end), expansion tape (swells in electrolyte to lock the winding), and blue film tape (wraps prismatic cells).
- Every tape inside a cell must pass electrolyte immersion testing — 85°C in standard LiPF₆ electrolyte for 168 hours with no delamination, no adhesion loss above 20%, and no extractables that poison the cell chemistry.
- Tab tape is typically polyimide or PET with acrylic adhesive; termination and blue film tapes are PET or PP based; expansion tape uses a specialty swelling adhesive layer.
- Before a bulk order, run three verifications: electrolyte soak test, peel strength before and after soaking, and a pilot winding trial on your own line — never qualify a tape on datasheet values alone.
Lithium battery insulation tape is a family of specialized pressure-sensitive tapes used inside lithium-ion cells to insulate welded tabs, fix wound electrodes, cushion expansion, and wrap prismatic housings — and each position imposes a different set of chemical, electrical, and mechanical demands. Unlike general electrical tape, every tape that goes inside a cell must survive years of direct contact with aggressive carbonate electrolyte without swelling, dissolving, or contaminating the chemistry. This article maps where each tape sits in the winding and stacking process, breaks down the requirements and selection criteria for tab, termination, expansion, and blue film tapes, explains how Ni-MH battery tape differs, compares backing materials and adhesive systems, and finishes with the verification checklist to run before committing to a bulk order — helping cell manufacturers and pack builders source battery tape with confidence.
Where Tapes Are Used Inside a Lithium Cell
A cylindrical or prismatic cell contains tape at four distinct positions, each visible if you follow the winding or stacking sequence. First, after the anode and cathode tabs are ultrasonically or laser welded to the current collectors, the weld zone is covered with tab tape to prevent burrs from puncturing the separator and to insulate the weld from the opposite electrode. Second, when the electrode-separator sandwich is fully wound, the outermost turn is fixed with termination tape so the jellyroll cannot unwind during insertion into the can. Third, some cylindrical designs place expansion tape at the core or between layers, where it swells on contact with electrolyte to take up dimensional slack and maintain internal pressure against the can wall. Fourth, prismatic cells receive an external wrap of blue film tape — the characteristic blue skin — that insulates the aluminum housing, protects it from scratches, and provides a printable surface for codes and labels. Each position sees the same electrolyte but different mechanical stress, which is why no single tape construction covers all four.
Tab Tape: Electrolyte Resistance, Low Impedance, Adhesion
Tab tape works at the most electrically critical point in the cell — the welded tab — so its requirements are the strictest. The backing is typically 0.025–0.05 mm polyimide film (high-drain cells) or PET film (consumer cells) with an electrolyte-resistant acrylic adhesive. Three properties define a qualified tab tape. Electrolyte resistance: after 168 hours in standard electrolyte (1M LiPF₆ in EC/DMC/DEC) at 85°C, the tape must show no edge lift, swelling ≤5%, and adhesion retention ≥80%. Low impedance: total thickness directly affects the tab interface, which is why tab tapes run thinnest of the four. Burr coverage: the adhesive must wet out over weld burrs without voids — a single exposed burr can pierce the 9–16 μm separator and create an internal short. SIDA lithium battery tab tape is available in polyimide and PET constructions with batch-tested electrolyte immersion reports.
Termination Tape: Fixing the Jellyroll End
Termination tape closes the jellyroll and must hold that closure through electrolyte filling, formation, and years of charge-discharge expansion. Its backing is usually PET or PP film, 0.03–0.06 mm, with acrylic or rubber-based adhesive. The defining requirements are initial tack — the tape must grab instantly on a high-speed winding line — and long-term shear resistance in electrolyte, because the wound layers exert constant unwind force on the joint. A tape that loses shear strength lets the jellyroll loosen, showing up as capacity fade and, in severe cases, tab misalignment. SIDA termination tape is offered in green, blue, and transparent PET with high-tack acrylic systems matched to winding-line speeds up to 300 mm/s.
Expansion Tape: The Swelling Principle
Expansion tape is the least understood of the four. Placed inside the winding — typically at the core of a cylindrical cell — its adhesive or backing layer is engineered to swell in a controlled way on contact with electrolyte, expanding 20–100% in thickness over the first formation cycles. This swelling takes up the internal clearance left for winding insertion, then maintains steady outward pressure that keeps the electrode layers pressed uniformly. That pressure matters for cycle life: layers that shift microscopically during charge-discharge develop uneven current distribution and accelerated lithium plating. Selection criteria are the swelling ratio (matched to the designed clearance — too much over-compresses the separator and restricts ion flow), the swelling speed (full expansion within the formation window), and chemical cleanliness, because the swelling polymer lives in the electrolyte for the cell’s entire life. SIDA expansion tape is specified by swelling ratio and initial thickness; our technical team can match the ratio to your cell’s designed clearance.
Blue Film Tape: Wrapping and Protecting Prismatic Cells
The blue film wrapping on prismatic and large cylindrical cells is a PET-based tape or film, typically 0.08–0.12 mm thick, applied to the aluminum housing after assembly. Its jobs are electrical insulation of the can (which is often live at cell potential), mechanical protection against scratching and abrasion in module assembly, and cosmetic identity — the blue color has become an industry convention. Key selection parameters are puncture and abrasion resistance (the film must survive module stacking and vibration), adhesion on aluminum that holds through thermal cycling from −40°C to 85°C in automotive service, and dielectric strength of at least 4–6 kV for pack-level insulation coordination. For EV applications — see our electric vehicle insulation solutions — blue film must additionally pass flame and smoke requirements at pack level. SIDA power battery blue film tape is produced in widths matched to standard prismatic cell heights with corona-treated surfaces for ink adhesion.
How Ni-MH Battery Tape Differs
Nickel-metal-hydride cells impose a different chemistry: the electrolyte is alkaline (potassium hydroxide) rather than a lithium organic carbonate, and KOH attacks adhesives and backings through hydrolysis rather than solvent swelling. Tapes qualified for lithium cells are therefore not automatically qualified for Ni-MH. Ni-MH tape uses alkali-resistant backings (PP and stabilized PET) with adhesives formulated to resist saponification; the qualification soak is 6M KOH at 60–85°C rather than LiPF₆ carbonate at 85°C. SIDA Ni-MH battery tape is a dedicated alkaline-system product line, tested and reported separately from the lithium series — do not substitute one for the other without requalification.
Material Comparison: PET vs PI vs PP Backings
| Property | PET Film | Polyimide (PI) Film | PP Film |
|---|---|---|---|
| Typical thickness | 0.025–0.12 mm | 0.025–0.05 mm | 0.03–0.08 mm |
| Temperature resistance | 130–150°C | 220°C+ | 100–120°C |
| Electrolyte resistance (LiPF₆) | Good | Excellent | Good |
| Alkali resistance (KOH, Ni-MH) | Fair (stabilized grades good) | Good | Excellent |
| Puncture / burr coverage | Good | Excellent | Fair |
| Relative cost | Base | 3–5× PET | 0.8–1.0× PET |
| Typical position | Termination, blue film, tab (consumer) | Tab (high-drain), high-temp zones | Termination (cost-sensitive), Ni-MH |
The adhesive system matters as much as the backing: solvent-based acrylic adhesives dominate for their electrolyte stability, while rubber systems are used where high initial tack is needed on winding lines. For a deeper look at polyester film behavior across industries, see our polyester film tape applications guide.
What to Verify Before a Bulk Order
Battery tape qualification should never rest on datasheets. Run this three-step verification before committing to volume:
- Electrolyte soak test. Immerse tape samples (applied to aluminum and copper foil, as in the cell) in your actual electrolyte at 85°C for 168 hours. Pass criteria: no delamination, no discoloration of the electrolyte, swelling ≤5%, adhesion retention ≥80%. For Ni-MH, substitute 6M KOH at 60°C.
- Peel strength before and after soaking. Measure 180° peel per ASTM D3330 on the as-received tape and on soaked samples. The absolute values matter less than the retention ratio — a tape that starts at 8 N/25mm and ends at 3 N/25mm will fail in service even though both numbers look acceptable in isolation.
- Pilot line trial. Run at least one winding shift with the candidate tape on your own equipment. Verify unwind tension stability, tack at line speed, and cut-edge cleanliness — adhesive ooze on slit edges is the most common cause of taping-head jams.
Beyond testing, qualify the supplier: ask for batch-level certificates of analysis, electrolyte immersion reports on production lots (not lab samples), and the change-notification policy for raw materials. SIDA supplies full documentation for every battery tape lot; our new energy materials program supports cell manufacturers from sample kits through mass production.
Frequently Asked Questions
Can the same tape be used for tab and termination positions?
Technically some PET-acrylic constructions pass both positions’ tests, but it is rarely optimal. Tab tape is engineered thinner (for impedance and burr coverage) and termination tape tackier (for line-speed fixation). Using one tape for both means compromising on at least one requirement — and tab failure modes (internal shorts) are far more dangerous than the cost saved. Specify dedicated tapes for each position.
What colors are available, and does color matter?
Tab tape is commonly green, blue, or amber (polyimide natural); termination tape green, blue, or transparent; blue film is blue by convention. Color is functionally a visual-inspection aid — a contrasting color makes coverage verification and automated optical inspection reliable. Pigments must themselves be electrolyte-stable, which is why battery tapes use qualified inorganic or stable organic pigments rather than generic dyes.
How long can battery tape be stored before use?
Stored sealed at 15–30°C and below 65% RH, acrylic-adhesive battery tapes maintain specification for 12 months from manufacture; rubber-based systems age faster (6–9 months). Run a quick adhesion check on stock older than 9 months, and never use tape from long-opened packaging — moisture pickup affects both adhesion and the cell’s water content budget.
What widths and roll formats are standard?
Tab tape typically ships slit to 2–15 mm widths; termination tape 8–20 mm; blue film in widths matched to cell height (50–200 mm). Standard roll lengths are 50–500 m on 76 mm cores, with splice-free rolls available for automated lines. State your winding machine’s core size and maximum roll diameter in the RFQ to avoid adapter downtime.
Summary
Sourcing lithium battery insulation tape means qualifying four distinct products, not one: thin, electrolyte-proof tab tape for weld protection; high-tack termination tape for jellyroll fixation; swelling expansion tape for internal pressure management; and puncture-resistant blue film for prismatic cell wrapping — plus a separately qualified alkaline-resistant series for Ni-MH. The non-negotiables are electrolyte immersion data on production lots, adhesion retention after soaking, and a pilot trial on your own winding line. SIDA manufactures the complete battery tape family — tab, termination, expansion, blue film, and Ni-MH — with batch-level test documentation and custom slitting to your line’s specifications:
Contact SIDA for Battery Insulation Tapes:
📞 +86-15958243831
📧 jessie.feng@sidanm.com
💬 WhatsApp: https://wa.me/8615958243831
🌐 sidanm.com
Browse the battery tape range: Tab Tape | Termination Tape | Expansion Tape | Blue Film Tape | Ni-MH Tape
References
- IEC 61960-3:2017 — Secondary Cells and Batteries Containing Alkaline or Other Non-Acid Electrolytes — Secondary Lithium Cells and Batteries for Portable Applications. International Electrotechnical Commission. https://webstore.iec.ch/publication/27485
- ASTM D3330/D3330M-04(2018) — Standard Test Method for Peel Adhesion of Pressure-Sensitive Tape. ASTM International. https://www.astm.org/d3330_d3330m-04r18.html
- UL 2580 — Standard for Batteries for Use in Electric Vehicles. Underwriters Laboratories. https://www.ul.com/standards
- IEC 62133-2:2017 — Secondary Cells and Batteries Containing Alkaline or Other Non-Acid Electrolytes — Safety Requirements for Portable Sealed Secondary Lithium Cells. International Electrotechnical Commission. https://webstore.iec.ch/publication/32662
- Xu, K. (2014). “Electrolytes and Interphases in Li-Ion Batteries and Beyond.” Chemical Reviews, 114(23), 11503–11618. https://pubs.acs.org/doi/10.1021/cr500003w
- GB 31241-2022 — Lithium Ion Cells and Batteries Used in Portable Electronic Equipments — Safety Technical Specification. Standardization Administration of China.
