Description
1. Significance of Electrode Resistance Measurement
Material Evaluation
- Evaluate resistance of electrodes and current collectors prepared with different cathode materials, anode materials, conductive agents, binders, and current collector types.
Process Evaluation
- Evaluate electrode resistance prepared with different slurry formulations.
- Assess consistency and uniformity of the coating process.
- Assess consistency and uniformity of the calendering (compaction) process.
Failure Analysis
- Evaluate electrode resistance changes during room/high-temperature cycling and storage.
- Compare electrode resistance across different States of Charge (SOCs).
2. The Limitations of Traditional Test Methods
2.1 Current Status of Electrode Resistance Measurement
Multiple methods exist for measuring electrode resistance, including four point probe, multi-point probe, and single-point probe techniques. While these conventional approaches are well-established for homogeneous thin films in other fields, they exhibit significant limitations when evaluating composite electrodes for lithium-ion batteries.
2.2 Four-Point Probe Method
The four-point probe technique is a standard method for measuring thin-film surface resistance. Using four or more probe contacts, it provides accurate sheet-resistance measurements with simple operation. By applying basic equivalent-circuit models, the technique can separate anisotropic resistance components. When combined with electrode thickness measurement, four-point-probe data enable precise calculation of bulk resistivity and support comprehensive electrode characterization. However, its fundamental principle requires:
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Smooth surfaces
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Homogeneous materials
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Insulating substrates
Lithium-ion battery electrodes present critical incompatibilities:
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Inherently rough surfaces
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Multi-component heterogeneity (active materials, binders, conductive additives)
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Conductive current collector substrates
Consequently, four point probe measurements yield inconsistent data that defy theoretical modeling. Increasing probe quantity/complexity marginally improves reliability but introduces:
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Structural impracticalities
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Compromised measurement repeatability & reproducibility
2.3 Single-Point Probe Method
This industry-prevalent approach employs:
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Fixed probe at current collector terminus
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Mobile probe on electrode coating surface
Despite its simplicity (often implemented via user-assembled probes with resistance meters), it remains a rough empirical method neglecting critical variables:
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Applied pressure consistency
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Current path length variation
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Substrate interference effects
Thus, single-point probing fails to deliver reliable or consistent electrode resistance data.
3. The IEST’s Creative Solution
The BER Series Multifunctional Electrode Resistance Analyzer combines a high-precision pressure control system with integrated capabilities for electrode thickness measurement and resistance analysis. The BER Series adopts the dual-planar pressure-controlled disc electrode resistance method to directly measure the overall resistivity of real battery electrodes—comprising the sum of coating resistance, coating-to-current collector contact resistance, and current collector resistance. Jointly developed with CATL and Xiamen University. It is an ideal tool for electrode formulation development and process stability monitoring. 
3.1 Our Unique Testing Process:
- Comprehensive evaluation of slurry mixing homogeneity and coating stability, facilitating early detection of conductive agent agglomeration.
- Identification of mixing uniformity deviations in silicon-carbon composite anodes.、
- Assessment of electronic conductivity for different active material formulations.
- Evaluation of electronic conductivity across varied conductive agent formulations.
- Characterization of electronic conductivity in functional primer coatings for current collectors.
- Failure analysis of battery conductive networks.
- Contact resistance profiling of cathode/anode surfaces post-formation.
3.2 Measurable Samples
As an leading electrode resistivity tests manufacturer, IEST Instrument presents the BER Series battery electrode resistance analyzer. The BER Series employs two pressure-controllable planar probes to directly measure through-thickness electrode resistance, which can obtain the overal resislance and resistivity in the thickness directon of the electrode, includimng the contact the collector and the current.
The dual-plane, pressure-controllable, high-conductivity probe specially designed for composite electrode and micron-level flat surface treatment ensure the measurement accuracy, the high-precision resistance resolution and the attached calibration module ensure the stability and reliability of the results.
3.3 Test Methods and Principles—Three Methods
| Equipment | Four-Point & Multi-Probe Method | Single-Probe Method | BER Series Electrode Resistance Meter |
|---|---|---|---|
| Principle |  |
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| Rtotal | Rtotal = Rcoating + Rcoating-collector + Rcollector | Rtotal = Rcoating-test electrode + Rcoating + Rcoating-collector + Rcollector-transverse | Rtotal = Rcoating-test electrode + Rcoating + Rcoating-collector + Rcollector-longitudinal |
| Applicable Samples | Single-component thin films with smooth surfaces (non-electrodes) | Composite electrodes with current collectors | Thicker composite materials with resistance gradients (electrodes / current collectors) |
| Function | Measure resistance and conductivity of single-component thin films with smooth surfaces | Measure resistance of composite electrodes with current collectors | Measure resistance and conductivity of battery electrodes, adjust testing pressure, and measure electrode thickness changes |
| Summary | 1. Traditional testing methods do not account for parameters such as pressure and contact area during testing. Furthermore, there is a significant discrepancy between theoretical calculation models of multi-point probes and actual samples, making the data results uncontrollable. 2. The BER series battery electrode resistance meter accurately controls testing parameters such as pressure and contact area to ensure stable and reliable results, and directly establishes the correlation between electrode compaction density and electrode resistance. |
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4. Applictions
Material Evaluation
- Active material conductivity evaluation
- Conductivity evaluation of conductor types
Process Evaluation
- Evaluation of electrode primer technology
- Conductive agent distribution uniformity evaluation
- Uniformity evaluation of silicon–carbon hybrid material
Cell Evaluation
- Analysis of electrode resistance during high temperature cycle & storage
5. Software
6. Measurement System Analyze(MSA)
Applications
1. Materials Evaluation
1.1 Modification of NCM Ternary Materials With Varying Nickel Content
- Adjust the Ni content in the NCM material, and test the powder conductivity. It can be found that as the Ni content increases, the powder conductivity increases;
- Comparing three NCM pieces with different Ni content, it can also be obtained that as the Ni content increases, the conductivity of the electrode piece increases;
- Powder resistivity and electrode have the same trend.
1.2 Evaluation of Conductive Agent Types
(Note: Coefficient of Variation(COV)=(Standard Deviation SD/Mean)×100%)
Constant pressure test
- Pressure: 25MPa
- Holding time: 25s
- Points tested: 15 points
- Electrical conductivity ranking: SP-1 > SP-2 > SP-3
- Dispersion homogeneity assessment: SP-3 shows higher coefficient of variation (COV) in conductivity, indicating inferior dispersion homogeneity. Both SP-1 and SP-2 exhibit superior dispersion performance
- Electrode conductivity characterization can be applied to evaluate conductive agents’ electrical conduction and dispersion properties.
1.3 Evaluation of Coated Aluminum foil: Bare aluminum foil, carbon-coated aluminum foil A, carbon -coated aluminum foil B
- Different primer coating processes alter the conductivity of current collectors.
- After coating a 1–2 μm layer of primer material onto bare aluminum foil, the current collector exhibits better conductivity uniformity, but its resistivity increases.
2. Process Evaluation
2.1 Stability Monitoring of Coating & Calendering Processes Across Batches
- The dispersion of conductive agents in cathode and anode electrodes is influenced by numerous complex process parameters, such as slurry formulation, mixing conditions, and coating/drying conditions. Non-uniform dispersion of conductive agents significantly deteriorates the kinetic performance of battery cells, yet it is difficult to detect through conventional monitoring methods like electrode appearance or adhesion strength. Consequently, it is easily overlooked and can cause irreversible losses.
- Monitoring electrode resistance variations across different batches and positions enables rapid identification of process fluctuations at the electrode stage.
2.2 Cathode and Anode Electrodes with Different Conductive Agent Formulations
As conductive carbon content increases, the resistivity of NCM electrodes progressively decreases. When conductive carbon exceeds 5%, the reduction magnitude diminishes significantly. Conversely, graphite electrodes exhibit a near-linear reduction in resistivity.
2.3 Evaluating Electrode Side A/B Coating Differences — Folding Method
- When Side A or Side B faces up individually, the differences in electrode resistance and uniformity are relatively small.
- When tested after folding Side A or folding Side B, differences are observed between the two, which are mainly caused by coating variations between the two sides. Therefore, this method can be used to evaluate coating differences between Side A and Side B.
2.4 Electrode Compressibility Characterization
- 1 (1.35 g/cm³) < 2 (1.5 g/cm³) < 3 (1.6 g/cm³) < 4 (1.65 g/cm³)
- As the electrode calendering pressure increases, the maximum deformation, reversible deformation, and irreversible deformation of the four electrodes all decrease gradually (1 > 2 > 3 > 4), though the rate of decrease gradually slows down. This trend is closely related to the filling and compaction effects of the powder within the electrode coating, including particle flow and rearrangement, elastic and plastic deformation, as well as particle breakage. Typically, during the electrode calendering process, work must be done on the electrode coating to overcome friction, surface forces, elastic deformation, plastic deformation, and particle breakage in order to compact the electrode.
3. Failure Analysis
3.1 Anode/Cathode Electrode Changes During High-temperature Cycling & Storage
- Cathode electrode resistance continuously increases with the number of cycles, indicating significant changes on the cathode side after high-temperature cycling, which may be related to side products on the surface of cathode particles or inter-particle contact.
- Anode electrode resistance increases with extended storage time, indicating significant changes on the anode side during storage, which may be related to increased side reactions on the surface of anode materials.
3.2 Electrode Resistance Analysis of Disassembled Cells at Different SOCs
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Dry electrodes exhibit the lowest resistance and the best resistance uniformity.
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The electronic resistance test results of disassembled electrodes are consistent with the previously measured cell DCR trends.
- After DMC soaking and drying, the electrode resistance increases overall, with the anode showing a greater degree of increase. Additionally, the COV (Coefficient of Variation) of electrode resistance increases significantly post-soaking.
Video
Specifications
| Model | BER2100 | BER2200 | BER2300 | BER2500 | |
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| Pressurization Method | Pneumatic Cylinder (Requires air source, Pressure: 5 ~ 35 MPa) |
Servo Motor (No air source required, Pressure: 5 ~ 60 MPa) |
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| Measurable Parameters | Resistance, Force, Temp & Humidity | Resistance, Resistivity, Conductivity, Force, Pressure, Temp & Humidity | Resistance, Resistivity, Conductivity, Force, Pressure, Temp & Humidity | Resistance, Resistivity, Conductivity, Force, Pressure, Temp & Humidity, Thickness, Compacted Density | |
| Functions | Single-Point Test | ● | ● | ● | ● |
| Continuous Test | − | ● | ● | ● | |
| Variable Pressure Mode | − | − | ● | ● | |
| Fully Automated Software | − | ● | ● | ● | |
| Thickness Measurement | − | − | − | Range: 0 ~ 5 mm Resolution / Accuracy: 0.1 μm / ±1 μm |
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| Compacted Density Curve | − | − | − | Electrode resistance, resistivity, and conductivity vs. compacted density curves | |
| Optional Features | In-situ Double-Sided (A/B) Electrode Testing, Automatic Sample Feeder | ||||
| Specifications |
1. Dimensions (W×D×H): 355 × 321 × 560 mm
2. Weight: 70 kg
3. Rated Power: 100 W
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1. Dimensions (W×D×H): 355 × 321 × 795 mm
2. Weight: 83 kg
3. Rated Power: 450 W
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IEST Lithium Battery Electrode Resistance Tester
