Electrode Tab Design — The Hidden Variable That Determines Internal Resistance

What Is in Focus: The Tab Hidden Behind the Capacity Spec

The electrode tab is the only path through which current leaves the inside of a cell, and the tab’s position and number alone can sharply change a cell’s internal resistance and heat generation. The higher the power of a cell, the more tab design becomes a hidden variable governing performance and life, and it has recently become an area contested through patents, going beyond multi-tab designs to “tabless” structures that use the entire electrode edge as the current-collection path.

Start with the industry picture. Cell spec sheets lead with capacity (Ah) and energy density, but tab structure is rarely disclosed. Yet in applications that draw large currents in bursts, such as power tools and high-performance EVs, cells of the same chemistry and capacity can differ in heat generation and degradation rate depending on tab design. The larger the cell and the longer the electrode, the bigger this difference becomes.

The tension is a trade-off between manufacturing and performance. Adding tabs lowers resistance but increases weld points and alignment steps. This piece answers three questions. Why do tab position and number change resistance? How do experimental and modeling studies show the difference? And what scope of rights is tab design creating from a patent perspective?

Basic Principle: The Distance Current Has to Walk

An electrode is a long strip of thin metal foil (the current collector) coated with active material. Current generated throughout the active material flows along the foil, gathers at the tab, and leaves the cell through it. Because the foil’s resistance is proportional to the length the current travels, current from points farther from the tab travels a longer path and meets more resistance.

By analogy, a tab is “the exit of a long corridor-style building.” If there is only one exit at the end of the corridor (single tab), people at the far end must walk the whole corridor, and the area near the exit is always crowded. If exits are added at intervals along the corridor (multi-tab), walking distance shrinks and crowding is spread out. If one entire wall of the corridor is opened as an exit (tabless), walking distance shrinks to roughly the corridor’s width. In exchange, the more exits there are, the more door-installation work (welding) is needed.

Heat is generated in proportion to this resistance multiplied by the square of the current (Joule heating). So when current doubles, heat at the same resistance quadruples. This is why tab resistance becomes a variable that cannot be ignored in high-power applications. And when current crowds near the tab, temperature differences (thermal gradients) form inside the cell, and degradation rates can differ by region.

• Single tab: current concentrated at one point at the electrode end; simple structure; long current path
• Multi-tab: current collected at multiple points; short path; higher welding and alignment burden
• Tabless: the whole electrode edge used for collection; shortest path; requires a separate forming process

Comparison: Single Tab vs. Multi-Tab, and What Research Shows

The first table below preserves the original comparison table. The second table summarizes the conditions under which published academic studies confirmed the effect of tab count.

Item	Single tab	Multi-tab
Current path	Concentrated at one point at the electrode end	Collected at multiple points
Internal resistance	Relatively high	Low due to shorter paths
Manufacturing difficulty	Simple	More tab alignment and weld points
Internal temperature distribution	Tends to concentrate around the tab	Tends to spread out (smaller thermal gradient)

What this table says: Multi-tab designs have the advantage in resistance and heat distribution, but the price is paid in the manufacturing process. Tab design is a performance question and a process-yield question at the same time.

Study	Cell studied	Conditions	Tab-related result
Waldmann et al., Journal of Energy Storage 5 (2016)	26650 cylindrical high-power cells (LiFePO₄ cathode / graphite anode)	Modified with 1 to 4 current-collecting tabs; discharge up to 10C (=25 A)	Operando measurement of internal thermal gradients and electrochemical performance by tab count
Li et al., Journal of Power Sources 492 (2021)	LG M50T 2170 cylindrical cells (NMC811), validated with a 3D electro-thermal model	Varying the number of tabs joining the jellyroll to the can base; comparing side and base cooling	More tabs reduced the internal thermal gradient by up to 25.41%; as a single cooling surface, side cooling was more effective than base cooling

What this table says: Both studies confirmed that changing the tab count alone changes the internal temperature distribution of a cell, and the 2021 study quantified the effect as up to a 25.41% reduction in thermal gradient. That the cooling method also changed the results substantially in the same study means tab design should be viewed together with the pack cooling structure, not the cell alone.

Here this piece adds one interpretation. The value of tab design is easily summed up in one line as “lower resistance,” but what the research actually showed is thermal uniformity more than resistance itself. Smaller temperature differences inside the cell mean smaller regional variation in degradation, which affects pack-level life management and fast-charging limits. Tab structure should therefore be treated in cell-spec reviews not as an item next to capacity and resistance but as an “input to cooling design.”

Patent Perspective: The Scope of Rights for Structures That Eliminate Tabs

Claim gist: As a case that pushes tab design to its extreme, consider Tesla’s US granted patent US11749842B2 (Cell with a tabless electrode; inventors Kunio Tsuruta and two others). According to Google Patents, its priority date is November 5, 2018, its filing date November 4, 2019, its publication number US20200144676A1 (published May 7, 2020), and its grant date September 5, 2023, and its legal status is shown as Active (anticipated expiration November 4, 2039).

In substance, claim 1 covers (a) a cell in which a first substrate with conductive portions at one end, a second substrate, and a separator are wound around a central axis; (b) a configuration in which the spaced conductive portions form a concentric circular pattern when wound; (c) a cylindrical can and a cap with a contact surface; and (d) a configuration in which the conductive portions are electrically connected by being pressed against and in contact with the cap surface.

Filing history: The patent’s family continued into Europe, Japan, Korea, China, and elsewhere, including PCT application WO2020096973A1, and continuation filings are also ongoing in the US. Separately, the same applicant filed US20230402722A1 (Battery cell with a tabless electrode; priority date September 21, 2020; filed September 17, 2021; published December 14, 2023; pending), which covers a high-speed process in which flags at the electrode edge are cut, folded, and overlapped to create contact points for welding to a collector plate. The flow reads as the first patent targeting the “structure” and the follow-on application targeting “the process that makes that structure.”

Design-around points: The claims of US11749842B2 include specific limitations: the conductive portions form a concentric circular pattern and are pressed into contact with the cap surface. So even when the entire electrode edge is used, a structure that connects the conductive portions by welding them to a separate collector plate, or that collects current in an arrangement other than concentric circles, may lack a literal claim element. Conversely, a conventional multi-tab structure is far from this patent’s scope of rights, so its FTO (freedom-to-operate, infringement review) burden may be relatively small.

Design-around scenario (counterargument): However, if a change such as replacing “pressed contact” with “welded joint” achieves the same function (low-resistance collection across the entire electrode edge) with the same effect, it may be subject to a doctrine-of-equivalents analysis. Also, even if the structure is avoided, new infringement risk may arise in the flag-forming method if the process-side follow-on application is granted. Because this process application was pending as of the publication date, its final claim scope must be rechecked at grant. In-force patents on multi-tab and tabless designs held by other cell makers could not be confirmed within the scope of this piece.

Limits and Outlook

The optimistic outlook is that adding tabs or moving to tabless designs reduces internal resistance and thermal gradients, improving high-power and fast-charging performance and life together. There is, however, a counter-scenario. The more complex the tab structure, the more defect sources in welding, alignment, and forming, so if mass-production yield falls, the gain from lower resistance may be offset by cost and quality variation. And as the 2021 study shows, the effect of tab count depends on the cooling method, so without supporting pack cooling design, cell-level improvements may not translate into system performance.

The strategic alternative is to tier tab structures by application. Products where high power and fast charging are central would consider multi-tab or tabless designs first, while products with low power demands would protect yield and cost with a simpler structure. Tab design is rarely visible behind cell capacity specs, but it is a key variable governing internal resistance and heat generation, and the greater an application’s power demand, the more important it is to check the tab structure first.

It also helps to set out questions to ask alongside any tab-structure evaluation. First, is the tab at the end of the electrode or in the middle? Even with a single tab, position changes the distance to the farthest point. Second, do the cathode and anode share the same tab structure? Improving only one side can make the other the bottleneck. Third, does the cell maker manage tab-structure changes as process changes? Because tab structure is tied directly to yield, it is worth checking whether it is subject to change notification in the supply contract.

Practical action: Planning and IP staff procuring or developing high-power cells should ask that candidate cells’ tab structure (single, multi, or tabless) and collection method (pressed contact or welding) be stated in the specification, and, for tabless types, start an FTO review by building a claim chart against the claim elements of US11749842B2.

Items requiring verification

• Measured figures, under identical conditions, for the reduction in internal resistance (mΩ) of multi-tab versus single-tab designs
• Grant status and claim-scope differences of the Korean (KR) family member of US11749842B2
• Prosecution history and final claim scope of US20230402722A1
• In-force patents on multi-tab and tabless designs held by Korean cell makers

Sources

1. T. Waldmann, G. Geramifard, M. Wohlfahrt-Mehrens, Journal of Energy Storage 5 (2016) – Influence of current collecting tab design on thermal and electrochemical performance of cylindrical Lithium-ion cells during high current discharge
2. S. Li et al., Journal of Power Sources 492 (2021) – Optimal cell tab design and cooling strategy for cylindrical lithium-ion batteries
3. Google Patents, US11749842B2 – Cell with a tabless electrode
4. Google Patents, US20230402722A1 – Battery cell with a tabless electrode

Related Reading — Cell-to-Pack (CTP): What You Gain and Lose by Eliminating the Module · Why Do Pouch Cells Seem to Swell So Much? — The Structural Reason for Swelling · The 4680 Cylindrical Cell: The Name “Tabless” and the Actual Structure Are Different