Stephane Laruelle

Sodium-ion batteries are emerging as supplementary technology to lithium-ion batteries. This study focuses on investigating the thermal stability of Na3V2(PO4)2F3 (NVPF) || hard carbon (HC) sodium-ion cells through the lens of Solid Electrolyte Interphase. Differential Scanning Calorimetry demonstrated a clear increase in SEI stability formed with improved electrolyte formulations (NaFSI and additives). At cell level, Accelerating Rate Calorimetric tests were performed on pristine versus aged batteries. Ramp heating analysis revealed consistent thermal behavior, with SEI degradation initiating near 155 °C and thermal runaway (TR) triggering around 210 °C in both pristine and aged batteries. However, Heat Wait Search analysis on aged cells exhibited less severe TR compared to pristine batteries. The higher onset temperature observed in aged batteries was attributed to enhanced thermal stability of the re-formed SEI, while the reduced thermal severity was proven to be unlinked to the lower energy density.

After an introductory reminder of safety concerns pertaining to early rechargeable battery technologies, this review discusses current understandings and challenges of advanced sodium-ion batteries. Sodium-ion technology is now being marketed by industrial promoters who are advocating its workable capacity, as well as its use of readily accessible and cheaper key cell components. Often claimed to be safer than lithium-ion cells, currently only limited scientifically sound safety assessments of sodium-ion cells have been performed. However, the predicted sodium-ion development roadmap reveals that significant variants of sodium-ion batteries have entered or will potentially enter the market soon. With recent experiences of lithium-ion battery failures, sodium-ion battery safety management will constitute a key aspect of successful market penetration. As such, this review discusses the safety issues of sodium-ion batteries, presenting a twofold innovative perspective: (i) in terms of comparison with the parent lithium-ion technology making use of the same working principle and similar flammable non-aqueous solvent basis, and (ii) anticipating the arrival of innovative sub-chemistries at least partially inspired from successive generations of lithium-ion cells. The authors hope that the analysis provided will assist concerned stakeholders in the quest for safe marketing of sodium-ion batteries.

After an introductory reminder of safety concerns pertaining to early rechargeable battery technologies, this review discusses current understandings and challenges of sodium-ion batteries. Sodium-ion technology is now being marketed by industrial promoters who are advocating its workable capacity, use of readily accessible and cheaper key cell components. Often claimed to be safer than lithium-ion cells, currently only limited scientific-sound safety assessment of sodium-ion cells has been performed. However, the predicted sodium-ion development roadmap reveals that significant variants of sodium-ion batteries will potentially enter the market in the near future. With recent experiences of lithium-ion battery failures, sodium-ion battery safety management will constitute a key aspect of successful market penetration. As such this review discusses the safety issues of sodium-ion batteries presenting a twofold innovative perspective: i) in terms of comparison with the parent lithium-ion technology making use of the same working principle and similar flammable non-aqueous solvent basis and ii) anticipating the arrival of innovative sub-chemistries at least partially inspired from successive generations of lithium-ion cells. The authors do hope that the analysis provided will assist the concerned stakeholders in the quest for safe marketing of sodium-ion batteries.

This paper provides a holistic view of the different studies related to gassing in NMC/graphite lithium-ion batteries over the past couple of decades of scientific development. It underlines the difficulty of predicting the concentration and the proportion of gas released upon cycling and storage and to get a clear mechanistic insight into the reduction and oxidation pathways of electrolyte solvents, the thermal electrolyte degradation, as well as the reactions that involve secondary sources such as water, NMC surface species and cross-talk reactions. Though many relevant experiments such as operando gas analysis using isotope-labeled solvents or two-compartment cells have been conducted, they failed, for instance, to determine the exact mechanism leading to the generation of CO and CO₂ gas. Last but not least, this paper discusses different strategies that are currently proposed to reduce or eliminate gassing such as the use of electrolyte additives that enable singlet oxygen quenching or scavenging, NMC coatings that limit the contact with electrolyte and different lithium salts to prevent thermal electrolyte degradation.

With the aim of establishing a data simultaneous comparison, the Principal Component Analysis (PCA) statistical tool was applied to LiNi _0.6 Mn _0.2 Co _0.2 O ₂ /graphite Li-ion cells electrolyte’s decomposition products detected by UHPLC-ESI-HRMS. Herein, we illustrate how the chemometric tool associated with mass spectrometry data can be relevant to provide information about the presence of unusual molecules. Indeed, pristine Triton X-100 surfactant molecules used in the electrode elaboration process were detected after the impregnation stage. However, as they chemically react and oxidize at a potential lower than 4.5 V vs Li/Li ⁺ , only surfactant derivatives and classical ageing molecules were observed, respectively, after storage and cycling stages at 55 °C, leading to a triangle-type correlation circle. On the other hand, global schemes of LiPF ₆ -based electrolyte degradation pathways were elaborated from a comparative study with literature to help interpret results in future electrolyte ageing studies.

A reliable heating device coupled with a FTIR gas analyzer has been tailored with the aim of evaluating the role of state-of-the-art lithium-ion battery components and environmental conditions on thermal and toxic hazards. Here, we demonstrate its effectiveness in accurately assessing the role of fully charged 0.6 Ah pouch cells confinement, electrolyte composition and separator coating on heat release and toxic gas generation-related risks. The fire safety international standards developed by the ISO TC92 SC3 subcommittee were used to determine the asphyxiant and irritant gases toxicity. Cells tighting confinement proves to be a very efficient way to diminish and delay (from 180 to 245 °C) the thermal runaway phenomenon occurrence and relating toxic gas release. Vinylene carbonate as electrolyte additive is able to shift (+20 °C) the onset temperature, while substitution of 1/3 M LiPF₆ by LiFSI does not modify the thermal behavior, nor the toxic risks. The coating of a tri-layer separator influences the irritant gas toxicity related risk, by decreasing fluorinated components release. This study highlights that some improvements regarding LIB safety can be achieved through appropriate component selection and cells integration design at a module/pack level.