What every battery figure and Methods section must disclose — and what to do to make the
numbers trustworthy. Distilled from the reporting guidelines of Joule, ACS Energy Letters,
Advanced Energy Materials, and the Nature journals. Most journals — including Materials Today
Energy — expect these same items even when they do not provide a form.
Rule of thumb: a reader should be able to rebuild your cell and reproduce your plot from the
Methods and SI alone, and compare your numbers to anyone else’s on equal terms. If they can’t,
something on this list is missing.
A · Report these (in Methods / SI)
1. Cell and electrodes
Cell type and configuration — coin / pouch / Swagelok; half-cell vs full-cell.
Number of electrodes — 2-electrode (working + counter, i.e. a normal cell) or 3-electrode (working + counter + reference). Use 3-electrode whenever you need a single electrode’s true potential, or to separate anode from cathode contributions; a 2-electrode voltage cannot tell you which electrode is limiting.
Counter / reference electrode identity (e.g. Li metal). Half-cell CE against Li is not full-cell CE — say which you report.
Number of cells (n) — report how many independent cells each value is based on. Run at least three per condition (triplicate) where feasible; this is the common expectation and the basis for the error bars below.
Active-material mass and mass loading (mg cm⁻²).
Electrode area (cm²) and areal capacity (mAh cm⁻²).
Electrode formulation (active : conductive : binder), thickness, and density after calendering.
N/P ratio (negative-to-positive capacity) for full cells.
Li-metal anodes: lithium thickness / excess (the lithium inventory).
2. Electrolyte and separator
Electrolyte composition and — crucially — amount, as E/C ratio (µL mAh⁻¹) or µL cm⁻². A flooded coin cell hides poor efficiency.
Separator type and thickness.
3. Test protocol
Voltage window (cut-offs).
Current: the C-rateand the current density, with a clear definition of what 1C means (which capacity it is based on).
Basis of every specific current / specific capacity: per active material, per total electrode, or per cell.
Temperature (and whether it was controlled).
Formation protocol, CC vs CC–CV (and the CV cut-off current), and any rest steps.
Number of cycles actually run.
4. Metrics
Specific capacity with an explicit basis (per active mass vs per electrode / cell).
Initial (first-cycle) Coulombic efficiency and steady-state CE, to enough significant figures (e.g. 99.92 %, not “~100 %”).
Capacity retention: % over N cycles and the absolute capacities.
Energy / power density: state the level — material, electrode, or cell.
Rate capability across defined C-rates.
B · Do these (rigour)
Test at a practical mass loading (aim for areal capacity in the mAh cm⁻² range, not µAh); ultra-thin electrodes inflate rate and cycling.
Run a fair baseline / control under identical conditions in the same study.
Report more than one cell: at least three independent cells per condition where feasible, give n, show error bars or the spread, and report the average — never just the best cell.
Show raw voltage profiles (V vs capacity), not only capacity-vs-cycle.
Use an appropriate number of significant figures; put error bars on plots.
Build a full cell — or state plainly that you did not — before claiming device-level performance.
Disclose enough that someone else could rebuild the cell.
C · Reporting several cells (GCD & cycling)
When the same measurement is run on n cells, present it so the spread is visible and nothing is
hidden. State n in every caption.
Scalar numbers (capacity, ICE, steady-state CE, retention, energy density) — quote as
mean ± standard deviation across the n cells, and say it is SD (not SE). Example:
“148 ± 4 mAh g⁻¹ (n = 3)”.
Voltage profiles (the GCD curves) — show one representative cell, chosen as the one
closest to the mean, and say so. Do not point-by-point average voltage–capacity curves —
averaging smears the plateaus and invents a shape no cell produced. If you want to show
reproducibility, overlay all cells as thin, faint lines behind the representative one.
Capacity / CE vs cycle number — plot the mean as the line with a shaded ± SD band, or
plot every cell as a thin line with the mean in bold. Do not plot only the best cell.
Rate capability / bar summaries — bar = mean, error bar = SD; overlay the individual data
points when there are only a few cells.
Account for every cell — state how many cells were assembled and how many are included. If
any were excluded (short, no contact, leak), say so and why. Never quietly keep only the good ones.
One basis throughout — keep the same normalisation (per active mass, or per area) across
all cells and all panels so the numbers are comparable.
D · Red flags reviewers catch
A large areal capacity implied by a tiny loading, or huge specific capacity from ~0.5 mg cm⁻².
Half-cell data presented as if it were a full cell.
CE quoted as “~100 %” or to two significant figures.
No electrolyte amount / E/C ratio.
“High rate” from an electrode far thinner than any real device.
Only % retention with no absolute numbers; only the single best cell shown.
Journal notes
Joule requires a Battery Checklist to be submitted with the manuscript (Standardized Battery Reporting Guidelines).
ACS Energy Letters publishes An Experimental Checklist for Reporting Battery Performances — the items above track it.
Advanced Energy Materials gives community guidelines for interpreting and reporting energy-storage performance.
Nature Energy / Nature journals scrutinise loading, cell count, and reproducibility (The path to accurate reporting).
Materials Today Energy and most other journals expect the same core items even without a bespoke form.
An Experimental Checklist for Reporting Battery Performances — ACS Energy Letters 6, 2187 (2021). https://pubs.acs.org/doi/10.1021/acsenergylett.1c00870
Energy Storage Data Reporting in Perspective — Guidelines for Interpreting the Performance of Electrochemical Energy Storage Systems — Advanced Energy Materials (2019). https://advanced.onlinelibrary.wiley.com/doi/abs/10.1002/aenm.201902007
Best Practices for Reporting on Energy Storage — ACS Applied Materials & Interfaces (2015). https://pubs.acs.org/doi/10.1021/acsami.5b06029
Aligning academia and industry for unified battery performance metrics — Nature Communications (2018). https://www.nature.com/articles/s41467-018-07599-8
The path to accurate reporting — Nature Energy (2024). https://www.nature.com/articles/s41560-024-01663-y