The choice of the two chemistries is deliberate. NMC sits at technology readiness level 9 on NASA’s scale, meaning it is fully flight-proven in commercial terms: it accounted for roughly 60 percent of electric vehicle battery sales in 2022 and is projected to dominate the market alongside lithium iron phosphate through 2050. Lithium–sulfur, by contrast, is approaching commercial-scale manufacture with prototypes and demonstrators but no mass-market adoption, placing it at TRL 5–6. The two systems store energy in fundamentally different ways. NMC relies on the reversible intercalation of lithium ions into a layered transition metal oxide, while lithium–sulfur cells convert solid sulfur into solid lithium sulfide through a series of soluble lithium polysulfide intermediates. That conversion chemistry gives sulfur a theoretical gravimetric capacity of 1675 mAh g⁻¹, roughly six times the ~277 mAh g⁻¹ of NMC, but the diffusion of soluble polysulfides away from the cathode matrix causes capacity degradation that remains the central obstacle to adoption. Because the two chemistries occupy different operating regimes, the researchers argue they will play complementary rather than competing roles in electrification, which makes a side-by-side comparison of reporting practices particularly informative.

To gather the data, the team built a graphical user interface in a Python Jupyter notebook, allowing fast, standardised entry of parameters drawn from five voluntary reporting checklists published by ACS, Batteries Europe, Joule, the Journal of Power Sources and Wiley. Articles were identified through the Web of Science database and citation searching, with the most recent search performed in August 2025, and eligibility required that each paper report galvanostatic cycling capacity for the cathode under investigation. The database captured information on electrode fabrication, electrochemical testing and physical characterisation, distinguishing between the raw active material, the composite sulfur–carbon material, the finished uncycled electrode, in-situ measurements during cycling and post-mortem analysis of recovered electrodes. The full dataset is available as a CSV file in the supplementary information, and the extraction code is hosted openly on GitHub, inviting the community to extend the review as new papers appear.

The findings on electrode preparation are sobering. While 96 percent of articles reported the composition of the electrode, meaning the relative weights of active material, binder and conductive additive, far fewer reported the parameters that determine whether that composition translates into a homogeneous, reproducible coating. The scale of synthesis, which affects mixing conditions and slurry homogeneity, was reported by only 64 percent of lithium–sulfur articles and just 21 percent of NMC articles, despite being explicitly recommended in the ACS and Journal of Power Sources checklists. The solid content of the electrode slurry, which governs viscosity during coating, appeared in a mere 8 percent of papers. Some authors resorted to describing solvent quantities as an appropriate amount or enough, language that betrays reliance on tacit laboratory experience rather than transferable specification. This matters beyond the bench: electrode drying contributes approximately 12–13 percent of the embodied energy of cell manufacture, and replacing the toxic solvent NMP with PFAS-free alternatives is a research priority for both sustainable manufacturing and recycling.

Electrode thickness tells a similar story of under-reporting. Although it is a readily accessible measurement, thickness was reported by only 11 percent of lithium–sulfur and 12 percent of NMC articles, while the areal loading of active material, which can be inferred simply from electrode mass and area, was reported far more frequently at 73 percent and 37 percent respectively. Thickness and porosity directly influence cell-level energy density, and calendering, the compression of electrodes under defined load and temperature, controls porosity, tortuosity and electronic conductivity. Yet 15 articles reported using calendering without reporting the resulting thickness, specifying instead only the applied pressure. The physics here is subtle: reducing porosity improves conductivity, as one study demonstrated with a linear increase in conductivity as lithium–sulfur electrode porosity fell to 50 percent, but it also increases tortuosity, the ratio of the actual diffusive path length through the porous network to the straight-line distance. During discharge, precipitating lithium sulfide can block these winding pathways, reducing reversible capacity. Only one article in the entire dataset reported electrode tortuosity quantitatively, calculated from impedance measurements of symmetrical coin cells, even though tools such as TauFactor can extract it from tomographic data.

Electrochemical testing protocols showed equally troubling gaps. Four of the five publisher guidelines recommend stating the theoretical capacity used to calculate C rates, yet only 49 percent of NMC articles did so, compared with 90 percent of lithium–sulfur articles, likely because sulfur’s theoretical capacity is well-defined by its conversion stoichiometry while the practical lithium stoichiometry in novel NMC compositions is not. When the researchers converted reported current densities to C rates using an assumed capacity of 277 mAh g⁻¹ for NMC, they obtained near-integer C rate values, strongly suggesting that authors were using this figure implicitly without stating it. Temperature reporting fared worse still: 23 percent of lithium–sulfur and 45 percent of NMC articles specified the temperature during cycling, despite all surveyed guidelines recommending it. The consequences are not trivial. One cited study showed that lithium-ion pouch cells cycled in ambient laboratory conditions self-heated to 27 °C rather than the intended 25 °C, a difference comparable to diurnal fluctuations that measurably affected cell longevity through competing effects on lithium plating and interphase formation.

Electrolyte reporting exposed a chemistry-specific asymmetry. Lithium–sulfur articles overwhelmingly used the established 1:1 volume mixture of 1,2-dimethoxyethane and 1,3-dioxolane with 1 M LiTFSI salt, while NMC articles employed a more diverse range of carbonate solvents, most commonly ethylene carbonate blended with dimethyl or ethyl methyl carbonate in commercial formulations such as LP30 and LP57. The electrolyte-to-sulfur ratio is critical for lithium–sulfur energy density because excess electrolyte offsets the chemistry’s gravimetric advantage, with published targets ranging from 5 down to 2 µL mg⁻¹. The analysis found a skew towards lower reported E/S ratios and increased reporting after about 2019, suggesting authors report electrolyte volume when proactively minimising it but omit it when using excess. A further complication is lithium nitrate, the additive used in 73 percent of lithium–sulfur articles to passivate the lithium anode and suppress the polysulfide shuttle, which evolves gas at or below 40 °C and is therefore incompatible with UN transport regulations, a barrier that must be overcome for widespread adoption.

Physical characterisation practices also diverged between the chemistries in ways that reflect their underlying science. Scanning electron microscopy and X-ray diffraction dominated both fields, but for different purposes. In lithium–sulfur work, XRD distinguishes bulk crystalline sulfur from the thin amorphous layers sought at the host–electrolyte interface, while thermogravimetric analysis, reported by 65 percent of lithium–sulfur articles for the composite, confirms sulfur loading. In NMC research, Rietveld refinement of diffraction data is routine, reflecting the need for reversible lithium intercalation, and X-ray photoelectron spectroscopy probes the valence states of nickel, manganese and cobalt as well as the composition of the cathode–electrolyte interphase. Surface area and pore size measurements relied heavily on nitrogen adsorption with the Barrett–Joyner–Halenda equation, which can underestimate pores below 10 nm, yet only two lithium–sulfur articles specified a second method capable of resolving micropores. Notably, of the 200 articles surveyed, only one included a battery-specific voluntary reporting checklist in its supplementary information, and correspondence with three of the five publishing journals confirmed that checklist implementation is not routinely tracked.

The authors are careful not to prescribe a single magic parameter, concluding that no beach-head determinant of reproducibility emerged from the analysis. Instead, they argue that even non-optimised values, such as excess electrolyte volumes or unflattering electrode thicknesses, should be reported because they enable direct comparison across studies and reveal correlations with performance as each interdependent component is optimised. They also highlight that only one article in the dataset reported electrochemical data averaged over multiple cells, even though cells from the same batch assembled with nominally identical procedures are known to show different capacities and failure modes. The living database they have established, cataloguing values and references for key parameters across cell chemistries, electrode compositions and configurations, is intended as a foundation for a much larger resource, one that can also serve as a directory of mutually compatible input parameters for numerical models. If the community adopts it, the era of incomparable battery papers may finally begin to close.

Subject of Research: Systematic review of characterisation and parameter reporting practices in lithium-ion and lithium–sulfur battery cathode research

Article Title: Establishing a living systematic review of characterisation and parameter reporting in lithium-ion and lithium–sulfur cathode research

Article References: Bird, L., Shao, Y., Pang, B., Robinson, J., & Shearing, P. (2026). Establishing a living systematic review of characterisation and parameter reporting in lithium-ion and lithium–sulfur cathode research. Discover Electrochemistry, 3(1), Article 35. https://doi.org/10.1007/s44373-026-00099-1

Image Credits: AI Generated

DOI: 10.1007/s44373-026-00099-1

Keywords: lithium-ion batteries, lithium-sulfur batteries, NMC cathodes, reproducibility, systematic review, battery testing standards, electrode manufacturing, electrochemical characterisation, reporting guidelines, energy storage, technology readiness level, meta-analysis