SciMed Education
Scanning Electron Microscopy for Lithium-Ion Battery Materials
What is SEM and how is it used in lithium-ion battery inspection?
Scanning Electron Microscopy (SEM) is a key analytical technique for imaging and investigating materials at micro- to nanoscale resolution. By directing a finely focused electron beam across a sample’s surface, SEM collects emitted signals in the form of secondary and backscattered electrons, which are translated into high-resolution images of surface topography, microstructure, and elemental contrast.
When paired with Energy Dispersive Spectroscopy (EDS), SEM can also identify elemental distribution by the detection of characteristic X-rays, providing compositional insight down to sub-micron levels.
In the battery and energy storage industry, SEM plays a critical role in developing, manufacturing, and analyzing lithium-ion battery (LIB) components. It enables detailed evaluation of the electrode layers and the separator membrane, which are central to electrochemical performance, thermal safety, cycle life, and degradation behavior.
Why SEM is critical in battery R&D and QC
- Visualise and quantify particle dimensions, shape, and distribution
- Detect failure mechanisms such as cracks, delamination, or lithium dendrites
- Analyse interfacial contact between layers and within composite materials
- Measure thickness, uniformity, and porosity of coatings and membranes
- Track ageing-related microstructural changes after cycling
These capabilities are indispensable for battery researchers, manufacturers, and failure analysts.
Without SEM, it is virtually impossible to understand the relationship between material design and battery performance characteristics at the structural level.
Typical Features of Battery Materials Observed by SEM
SEM is particularly well-suited for analysing all three of the key internal components of lithium-ion batteries.
Each plays a distinct role in performance, and each has unique features that must be carefully optimised and inspected.
Cathode Materials
Lithium-ion cathodes are typically based on layered or spinel-structured metal oxides—like LiNiMnCoO₂ (NMC), LiFePO₄ (LFP), or LiCoO₂ (LCO)—sintered into micrometre-scale secondary particles. SEM allows researchers to assess:
• Particle morphology and size distribution to ensure consistent electrochemical behaviour
• Intergranular cracking, porosity, and voids introduced during cycling
• Coating uniformity (such as conductive carbon layers) and binder distribution
• Surface roughness, sintering quality, or contamination from synthesis or handling.
These features strongly influence cathode kinetics, capacity retention, and thermal stability.
Anode Materials
While most anodes are still based on graphite, alternatives like silicon-based materials and lithium metal are growing in relevance. SEM can be used to:
- Assess flake orientation, porosity, and binder adhesion in graphite layers
- Visualise SEI (solid electrolyte interphase) growth and degradation patterns
- Detect dendritic lithium plating, especially in fast-charging or overcharging conditions
- Monitor silicon particle expansion, fracture, and electrode delamination due to volume change
This level of structural insight is essential for optimising charge rate capability, capacity fade, and safety.
Separator Membranes
The separator is a microporous polymer film (typically polyethylene or polypropylene) that electrically insulates the electrodes while allowing lithium ions to pass. SEM analysis is essential for:
- Measuring pore size, distribution, and structural consistency
- Identifying punctures, melting, or thermal shrinkage from overheating
- Detecting blockage due to electrolyte decomposition products
- Evaluating ceramic coatings (such as Al₂O₃) for heat resistance or wettability improvement
Because separators are often less than 25 µm thick and contain pores that may be 10 nm in diameter, SEM is one of the only ways to resolve their microstructure.
How do I prepare battery materials for SEM analysis?
High-quality SEM imaging begins with proper sample preparation. This is especially important when working with fragile, composite, or beam-sensitive materials. Lithium-ion battery components often involve soft polymers, metal oxides, and multi-phase interfaces that require careful handling to prevent damage and reaction with the lab environment.
1. Mounting and Conductive Coating
- Electrodes can be embedded in epoxy, then either mechanically polished or ion milled to expose cross-sections.
- Powders can be dispersed onto conductive carbon tape or pressed into pellets.
- Separators may be mounted flat or cryogenically fractured to observe their pore structure internally.
- All non-conductive samples should be sputter-coated with a thin conductive layer of gold, platinum, or carbon to reduce charging under the beam.
2. Cross-Sectioning with Argon Broad Ion Beam (BIB) Milling
For high-resolution structural analysis of interfaces and internal layers, cross-sectioning is essential. Traditional mechanical sectioning may deform soft materials, delaminate layered composites, or introduce damage through heating.
Argon Broad Ion Beam (BIB) milling is a preferred method. It uses a wide, low-energy ion beam to slowly remove material, yielding damage-free, ultra-flat cross sections. BIB milling is ideal for:
- Preserving delicate multilayer structures (e.g., cathode/separator/anode stacks)
- Revealing buried features such as SEI layers or interfacial damage
- Avoiding artefacts from smearing, chipping, or mechanical stress
- Creating large-area cross sections for full-cell inspection
3. Minimising Beam Damage
Battery materials, particularly SEI layers, polymers, and electrolytes, can be damaged by exposure to the high energy electron beam of the SEM. To mitigate this SEM users would typically make use of:
- Low accelerating voltages (1–5 kV) for surface-sensitive imaging
- Fast scan speeds and low dwell times to reduce local heating
- Cryogenic stages, which stabilise volatile or soft samples, although they require careful handling and preparation.
These strategies help preserve the true microstructure and avoid introducing artefacts during imaging.
What can SEM reveal about battery materials?
Surface Morphology and Topography
Cathodes – Analyse cracking, sintering, particle agglomeration, and surface roughness
Anodes – Detect dendrites, lithium plating, SEI layer buildup, or binder breakdown
Separators – Visualise pore structure, ceramic coating morphology, and signs of damage
Cross-Sectional Analysis
Layer thickness of electrodes, separator, current collectors, or coatings
Interfacial bonding quality between layers and risk of delamination
Aging effects such as increased porosity, loss of adhesion, or SEI thickening
Thermal or mechanical damage such as melting or cracking
Cross-sectional imaging is particularly useful for post-mortem failure analysis after thermal runaway, capacity fade, or short-circuiting.
Compositional Mapping with EDS
By combining SEM with Energy Dispersive X-ray Spectroscopy (EDS), users can generate elemental maps of:
Transition metal distribution in cathodes (e.g., Co, Ni, Mn)
Contaminants like Fe, Cu, or Al from casing or current collectors
Migration of elements between electrodes (e.g., Mn dissolving into anode)
Coating layers (e.g., Al₂O₃, carbon, PVDF) and their uniformity
EDS mapping provides a crucial chemical dimension to structural observations, enabling correlation of performance with material composition.
What industries benefit from SEM analysis of lithium-ion batteries?
SEM analysis of lithium-ion batteries is indispensable across multiple sectors, each with unique performance and reliability requirements:
Consumer Electronics
- Longer battery life and faster charging in smartphones, laptops, and wearables
- Defect detection and optimisation of small-format cell designs
Electric Vehicles and Transportation
- Reliability under high currents and wide temperature ranges
- Detection of lithium plating or dendrite growth for safety
- Structural evaluation of new materials like silicon or solid-state electrolytes
Grid Energy Storage
- Maximising cycle life and energy density in large-format pouch and cylindrical cells
- Diagnosing degradation from cycling and environmental exposure
Academic and Industrial R&D
- Prototyping novel materials and interfaces
- Benchmarking new formulations against commercial baselines
- Performing post-mortem analysis of failed or degraded cells
Conclusion: Why SEM is Essential in Battery Development
SEM provides unmatched insight into the structure, composition, and failure modes of lithium-ion battery materials. From identifying nanometre-scale defects to mapping elemental diffusion, SEM supports every stage of the battery lifecycle from R&D to production to failure analysis.
What to do next?
At SciMed, we offer a full range of advanced SEM systems tailored for battery materials research and quality control, including the CIQTEK SEM5000X, specifically designed for high-resolution low-voltage imaging, elemental mapping, and automated workflows ideal for industry operators.
If you’re ready to enhance your battery research or production process, get in touch with SciMed to discover the SEM solution best suited to your application.
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