Battery failure analysis testing is a structured laboratory investigation of failed lithium-ion and other rechargeable cells, modules, and packs. The procedure traces a fault from its electrochemical origin to its physical expression on electrodes, separators, and current collectors. Work begins with non-destructive imaging and electrical characterization, proceeds to teardown and sample preparation, and continues with microscopic, spectroscopic, and chromatographic methods that identify degradation products, contaminants, and structural change. Each module below covers one stage of this chain: mechanism principles, failure modes and preparation, imaging and electrochemical techniques, gas and materials analysis, quantitative acceptance criteria, and typical application scenarios with report deliverables. The result is a defensible root-cause conclusion for manufacturers, insurers, and regulatory reviewers.
Principle & mechanism
A battery fails when electrochemical, thermal, or mechanical stresses exceed the tolerance of one or more cell components. Analysis therefore rests on correlating electrical behavior with material evidence. Capacity fade commonly originates in loss of lithium inventory, loss of active material, or rising impedance, and each mechanism leaves a characteristic signature in charge–discharge curves and impedance spectra. Internal short circuits arise from lithium dendrite penetration, metallic contamination, or separator damage, and typically announce themselves as abnormal self-discharge or rapid voltage collapse. Gas generation, electrode fracture, and current-collector corrosion follow distinct chemical pathways that can be verified analytically. A sound analysis treats the cell as a coupled system: thermal runaway, for instance, couples SEI decomposition, electrolyte reaction, and cathode oxygen release. The laboratory workflow preserves this coupling by sequencing tests from non-destructive to destructive, so that early measurements are not invalidated by later disassembly.
Failure modes and sample preparation
Failed cells must be handled as hazardous evidence. Prior to teardown, samples are photographed, weighed, dimensioned, and checked for residual voltage; swollen units are transferred to inert-atmosphere or ventilated enclosures because vented electrolyte is flammable and toxic. Discharge to a safe low state of charge is performed through a resistive load before any cutting operation. Teardown is then conducted inside an argon-filled glovebox, where humidity and oxygen would otherwise alter electrode surfaces and create artifacts. Electrodes are retrieved with ceramic or polymer tools, rinsed with a carbonate solvent such as dimethyl carbonate to remove residual electrolyte, and dried under vacuum. Specimens for microscopy are punched or sectioned to standard dimensions; cross-sections for ion-beam or argon-polishing preparation follow, since fresh-cut surfaces reveal layer thickness and interface condition. Every preparation step is logged with sample identity, and chain-of-custody records accompany the report.
Test
methods — CT, SEM/EDS, and electrochemical characterization
X-ray computed tomography is usually the first examination because it is non-destructive. It reveals electrode stacking defects, separator wrinkles, welding voids, deformation, and debris without opening the housing, and repeated scans can track internal change across cycling. scanning electron microscopy with energy-dispersive X-ray spectroscopy then examines morphology and elemental composition at high magnification: dendrite morphology, particle cracking, coating delamination, and foreign-metal particles are identified, while EDS mapping localizes elements such as fluorine, phosphorus, or iron that indicate electrolyte decomposition or contamination. Electrochemical characterization quantifies the electrical fault. Capacity and coulombic-efficiency tests establish fade rate; DC internal resistance and electrochemical impedance spectroscopy separate ohmic, charge-transfer, and diffusion contributions; cycling with dQ/dV analysis pinpoints which electrode governs degradation. Used together, these three method families connect structural observation with measurable electrical consequence.
Gas and materials analysis — GC-MS, ICP-OES, XRD
Destructive chemical analysis identifies what the electrochemical data cannot show directly. gas chromatography–mass spectrometry analyzes vented or extracted gases and electrolyte solvents, detecting decomposition products such as carbon dioxide, hydrogen, methane, and fluorinated species; their relative abundance distinguishes electrolyte oxidation from reduction-side reactions and SEI growth. inductively coupled plasma optical emission spectrometry quantifies dissolved and dissolved-out metal content: lithium, manganese, nickel, cobalt, and copper levels in electrolyte or on counter-electrodes reveal transition-metal dissolution and copper current-collector corrosion at over-discharge. X-ray diffraction determines crystallographic phase and structural change in cathode and anode materials, identifying phase transition, lattice-parameter shift, and degree of lithiation. Surface-analysis techniques such as X-ray photoelectron spectroscopy are often added to characterize SEI composition on a case-by-case basis. The combined dataset allows the analyst to state which chemical reaction pathway produced the observed failure signature.
Performance
metrics and acceptance criteria
Findings are judged against measurable indicators rather than visual impression alone. Capacity retention and fade rate are compared with the cell specification and with a reference cell of the same model cycled under identical conditions. Internal resistance increase is expressed as a percentage over the beginning-of-life value; impedance spectra are fitted to an equivalent circuit, and changes in each element are attributed to a physical component. Coulombic efficiency deviation, self-discharge rate, and dQ/dV peak shift serve as supporting criteria. Acceptance of a root-cause conclusion requires consistency across at least two independent evidence streams — for example, dendrite observation by CT confirmed by SEM, or gas composition from GC-MS consistent with impedance-derived SEI growth. Quantitative limits are drawn from the product specification, applicable safety and performance test standards, and contractual agreement with the client, since universal pass–fail thresholds do not exist for failure analysis itself. Any residual uncertainty must be stated in the report.
Application
scenarios and report deliverables
Typical submissions include field-failed cells returned from service, cells that failed during certification or production testing, post-thermal-runaway remnants, and units involved in recalls or liability disputes. Manufacturers use the analysis to close design or process gaps; insurers and legal parties rely on it to assign cause between manufacturing defect, misuse, and external damage; fleet operators apply the findings to adjust charging protocols and storage conditions. A complete report contains the sample description and chain of custody, test conditions and instrument methods, imaging and spectral evidence with annotated figures, quantitative metric tables against specification, a ranked root-cause determination, and corrective recommendations. Distinguishing between intrinsic product defect and extrinsic abuse requires the analyst to present the evidence chain openly. Where results remain inconclusive, the report defines the additional samples or tests needed to reach closure.
Frequently Asked Questions
What
sample requirements apply when submitting batteries for Battery Failure Analysis?
Samples should be submitted in their failed or as-received state with usage history and failure description provided. Depending on the suspected failure mode, intact cells, dissected components, or extracted electrode materials may be requested. Proper sample preparation, including safe disassembly and cross-sectioning, follows the failure modes identified in prior non-destructive examination.
How do I choose among CT, SEM/EDS, and electrochemical methods in Battery Failure Analysis?
Method selection depends on the failure hypothesis: CT reveals internal structural defects without disassembly; SEM/EDS characterizes morphology and elemental distribution of electrodes and interfaces; electrochemical characterization assesses capacity fade, impedance growth, and degradation mechanisms. Gas and materials analysis such as GC-MS, ICP-OES, and XRD further supplements compositional and crystallographic diagnosis.
What
criteria determine the conclusions in a Battery Failure Analysis report?
Conclusions are judged against performance metrics and acceptance criteria covered in the analysis plan, integrating imaging evidence, electrochemical data, gas composition, and material characterization results. Reports link observed failure modes to their underlying mechanisms, supported by applicable limit references and method-specific findings rather than single isolated measurements.