A study published in *Nature Energy* investigates the reproducibility of all-solid-state battery (ASSB) cell performance across 21 research groups. The study uses commercially available materials—LiNi₀.₆Mn₀.₂Co₀.₂O₂ for the positive electrode, Li₆PS₅Cl as the solid electrolyte, and indium for the negative electrode—to assess variability in cell assembly and electrochemical performance. The results show significant differences in processing pressures, pressing durations, and In-to-Li ratios among groups. Despite this, an initial open circuit voltage (OCV) of 2.5–2.7 V vs Li⁺/Li is a good predictor of successful cycling. The study recommends reporting data in triplicate to improve reproducibility. The study highlights large variability in cell performance, including specific discharge capacities ranging from 71 to 157 mAh g⁻¹ at 0.1 C, and Coulomb efficiencies varying between 75% and 99.8%. The initial OCV was found to be a critical factor in determining cell performance, with cells having OCVs below 2.5 V showing lower capacities. The study also found that cycling pressure significantly affects cell performance, with higher pressures (above 40 MPa) leading to better cycling performance. The study emphasizes the importance of standardized reporting of processing parameters and cell parameters to improve comparability of ASSB data. It also highlights the challenges in assembling ASSB cells, with a 43% failure rate due to issues such as improper electrode mixing, material degradation, and incorrect cell set-ups. The study recommends that the number of failed cells should be reported to better assess the reproducibility and robustness of the assembly protocol. The study concludes that while ASSB technology is promising, significant variability in cell performance exists due to differences in processing parameters and cell set-ups. To improve reproducibility and comparability, standardized testing and reporting of cell parameters are essential. The study also highlights the need for further research to standardize testing and improve the reproducibility of ASSB data.A study published in *Nature Energy* investigates the reproducibility of all-solid-state battery (ASSB) cell performance across 21 research groups. The study uses commercially available materials—LiNi₀.₆Mn₀.₂Co₀.₂O₂ for the positive electrode, Li₆PS₅Cl as the solid electrolyte, and indium for the negative electrode—to assess variability in cell assembly and electrochemical performance. The results show significant differences in processing pressures, pressing durations, and In-to-Li ratios among groups. Despite this, an initial open circuit voltage (OCV) of 2.5–2.7 V vs Li⁺/Li is a good predictor of successful cycling. The study recommends reporting data in triplicate to improve reproducibility. The study highlights large variability in cell performance, including specific discharge capacities ranging from 71 to 157 mAh g⁻¹ at 0.1 C, and Coulomb efficiencies varying between 75% and 99.8%. The initial OCV was found to be a critical factor in determining cell performance, with cells having OCVs below 2.5 V showing lower capacities. The study also found that cycling pressure significantly affects cell performance, with higher pressures (above 40 MPa) leading to better cycling performance. The study emphasizes the importance of standardized reporting of processing parameters and cell parameters to improve comparability of ASSB data. It also highlights the challenges in assembling ASSB cells, with a 43% failure rate due to issues such as improper electrode mixing, material degradation, and incorrect cell set-ups. The study recommends that the number of failed cells should be reported to better assess the reproducibility and robustness of the assembly protocol. The study concludes that while ASSB technology is promising, significant variability in cell performance exists due to differences in processing parameters and cell set-ups. To improve reproducibility and comparability, standardized testing and reporting of cell parameters are essential. The study also highlights the need for further research to standardize testing and improve the reproducibility of ASSB data.