Electrochemical testing is the measurement craft underneath battery development: the potentiostat work that separates what a cell does from why it does it. Cyclic voltammetry screens new electrode materials, electrochemical impedance spectroscopy deconvolves ohmic, charge-transfer and diffusion processes across frequency, chronoamperometry and chronopotentiometry probe kinetics and transport in the time domain, and polarization measurements quantify overpotential. Every program from coin cells to gigafactories consumes this discipline, and the review literature is explicit that screening energy storage materials begins with voltammetry before any cell is assembled .
The seat is harder to fill than the title suggests. The techniques share vocabulary with analytical chemistry, but battery electrochemical testing adds state of charge dependence, long relaxations and degradation interpretation. National lab work is equally blunt about what the techniques can deliver: rapid DC pulses and EIS can estimate state of charge and capacity in minutes, which is why demand for this craft tracks every chemistry program in the sector .
Challenges in Electrochemical Testing Recruiting
Cyclic voltammetry separates electrochemists from battery test operators
A CV looks simple: sweep potential, record current. Reading it is the discipline. Peak positions locate redox potentials, peak separations expose reversibility, and scan-rate sweeps separate surface capacitive current from diffusion-controlled faradaic current, which is how lithium diffusivity gets estimated. Reviews aimed at energy storage are explicit that cyclic voltammetry is the first screen for new materials, and that thermodynamics, electron transfer kinetics and reaction intermediates all come out of the voltammogram before a cell is ever built . Battery test operators run charge-discharge cycles; electrochemists read the duck-shaped traces. The distinction matters on a CV because performed cyclic voltammetry can mean pressing run on an instrument someone else configured. Assessment has to find out who chose the scan rates, the potential window and the reference, and who interpreted what came back.
Electrochemical impedance spectroscopy turns minutes of data into capacity diagnostics
EIS applies a small AC perturbation across frequency and returns the cell's ohmic resistance, charge-transfer resistance and diffusion behavior in minutes instead of the day a full discharge takes. NREL's benchmarking of rapid diagnostics across 79 cells of four types found near net-zero energy DC pulse sequences estimate state of charge within about 1% mean absolute error and capacity within 2 to 5%, and that models built on electrochemical impedance spectroscopy perform practically the same as DC pulses . The same study found both approaches fail almost completely at safety-relevant targets: lithium plating detected by post-charge voltage relaxation and gas generation could not be predicted from impedance or pulses . Hiring for EIS therefore splits into two skill sets that do not overlap automatically: equivalent-circuit model fitting for state estimation, and experiment design that knows what impedance cannot see.
Electrochemical characterization splits full cells from half cells with reference electrodes
A two-electrode full cell returns a single impedance spectrum in which anode and cathode are convolved. Deconvolution requires three-electrode setups, where a reference electrode lets a study attribute features to each side of the cell. Recent work on a multilayer pouch cell used a micro-reference T-cell to separate cathode charge transfer from contact resistance, showing the high-frequency intercept shifts with state of charge and grows over cycling . The electrochemical characterization craft lives in those details: reference electrode placement and drift, blocking conditions, electrolyte wetting, fixture inductance at high frequency. Reference electrodes are the weak point in most cell characterization programs, because a drifting lithium wire silently corrupts every spectrum taken after it, and few job descriptions ask whether the candidate has managed one. A candidate who has only measured commercial full cells has never faced the deconvolution problem; a candidate who has only built coin cells may never have faced hundred-kilohertz artifacts. The role decides which gap is acceptable.
Electrochemical impedance spectroscopy pairs with incremental capacity to name degradation
Aging diagnosis in production cells rarely trusts one technique. A study of 75 Ah prismatic NMC631 cells combined incremental capacity analysis with EIS to separate loss of lithium inventory, loss of active material and conductivity loss, and to catch knee-point transitions that impedance alone missed; distribution of relaxation times deconvolves overlapping semicircles into peaks tied to specific aging mechanisms . The hiring consequence is that the useful electrochemical testing engineer reads dQ/dV curves and Nyquist spectra as one data set, and can say which degradation mode each technique can and cannot resolve. People who know only one instrument are common; the programs that diagnose field-aged cells need both.
Chronoamperometry reads kinetics in the first seconds of a potential step
Step techniques are where the discipline gets quantitative. In chronoamperometry the potential jumps past the formal potential and the current decay follows the Cottrell equation; in cyclic voltammetry the peak current follows Randles-Ševčík scaling with the square root of scan rate . Tutorial reviews walk through diagnostic criteria for coupled chemical-electrochemical reactions, double potential steps, and rotating disk and microelectrode variants . The people who own this technique can derive a diffusion coefficient from raw data and defend its assumptions. Most candidates cannot, and the technique tolerates them: the instrument always returns a curve. The interview that matters asks the candidate to explain which equation governs the trace and what breaks it.
Chronopotentiometry GITT diffusivity spans four orders of magnitude
The galvanostatic intermittent titration technique is chronopotentiometry with rests: constant current pulses interrupted by open-circuit relaxation, used to extract chemical diffusion coefficients across state of charge. The critical review in the Journal of The Electrochemical Society found reported diffusivities for the same layered oxide span four orders of magnitude, because composition-dependent overpotentials, finite-size geometry and relaxation analysis mistakes are routinely ignored . Polarization measurements built on GITT overpotentials inherit every one of those errors . The hiring lesson is sharp: this technique rewards method discipline more than most. Ask the candidate what relaxation time they used, whether they corrected the overpotential, and what geometry assumptions their sample satisfied. People who can defend a GITT value have been forced to learn the physics; people who quote one usually copied it.
Nyquist and Kramers-Kronig checks expose inflated electrochemical impedance spectroscopy claims
The last challenge is verification, and this craft has better instruments for it than most. Impedance data is checkable: Kramers-Kronig relations test causality and stationarity, and a spectrum that fails them was measured on a drifting cell and should be discarded. The assessment probes are concrete: which instrument, which frequency range, which perturbation amplitude, which reference electrode, what the Kramers-Kronig residual was, and which equivalent circuit or physical model they fit. NREL's finding that impedance and pulse diagnostics fail to predict lithium plating and gassing is the cost of assessment failure made technical : a team that trusts the wrong diagnosis ships a design that fails later. Electrochemical testing hires who cannot defend their spectra cost a program weeks of chasing artifacts; the ones who can are worth the search.
References
- Cyclic voltammetry for characterizing energy storage materials — Nature Reviews Clean Technology. (accessed 2026-09-28)
- Benchmarking the Use of Rapid DC Pulses and EIS for Diagnosing Battery Capacity, State-of-Charge, and Safety (ECS Meeting Abstract MA2025-01 575) — The Electrochemical Society. (accessed 2026-09-28)
- Deconvolution of an SoC- and SoH-Dependent Contact Resistance in a Multilayer Pouch Cell Using Impedance Spectroscopy — Journal of The Electrochemical Society. (accessed 2026-09-28)
- Multi-Modal Diagnosis of Aging in NMC631 Cells Using Incremental Capacity and Electrochemical Impedance Spectroscopy — World Electric Vehicle Journal (MDPI). (accessed 2026-09-28)
- Cyclic Voltammetry and Chronoamperometry (Tutorial Review) — PMC, National Institutes of Health. (accessed 2026-09-28)
- Galvanostatic Intermittent Titration Technique Reinvented: Part I. A Critical Review — Journal of The Electrochemical Society. (accessed 2026-09-28)