A review of hard carbon anode materials for sodium-ion batteries and their environmental assessment

Abstract

Sodium-ion batteries are increasingly being promoted as a promising alternative to current lithium-ion batteries. The substitution of lithium by sodium offers potential advantages under environmental aspects due to its higher abundance and availability. However, sodium-ion (Na-ion) batteries cannot rely on graphite for the anodes, requiring amorphous carbon materials (hard carbons). Since no established market exists for hard carbon anode materials, these are synthesised individually for each Na-ion battery from selected precursors. The hard carbon anode has been identified as a relevant driver for environmental impacts of sodium-ion batteries in a recent work, where a significant improvement potential was found by minimising the impacts of the hard carbon synthesis process. In consequence, this work provides a detailed process model of hard carbon synthesis processes as basis for their environmental assessment. Starting from a review of recent studies about hard carbon synthesis processes from different precursors, three promising materials are evaluated in detail. For those, the given laboratory synthesis processes are scaled up to a hypothetical industrial level, obtaining detailed energy and material balances. The subsequent environmental assessment then quantifies the potential environmental impacts of the different hard carbon materials and their potential for further improving the environmental performance of future Na-ion batteries by properly selecting the hard carbon material. Especially organic waste materials (apple pomace) show a high potential as precursor for hard carbon materials, potentially reducing environmental impacts of Na-ion cells between 10 and 40% compared to carbohydrate (sugar) based hard carbons (the hard carbon material used by the current reference work). Waste tyres are also found to be a promising hard carbon precursor, but require a more complex pre-treatment prior to carbonisation, why they do not reach the same performance as the pomace based one. Finally, hard carbons obtained from synthetic resins, another promising precursor, score significantly worse. They obtain results in the same order of magnitude as the sugar based hard carbon, mainly due to the high emissions and energy intensity of the resin production processes.

On the environmental competitiveness of sodium-ion batteries under a full life cycle perspective – a cell-chemistry specific modelling approach

“…For NaNMMT cell chemistries, values of between 69-140 kg per CO 2 eq. per kWh can be found, 19,20,30 though with different assumptions regarding cell housing, hard carbon precursor and manufacturing energy demand, all parameters with relevant inuence on the total GHG emissions. This is signicantly higher than the 50.6 kg CO 2 eq.…”

“…Hard carbon derived from petroleum coke is used as active materials for the anodes, a material that showed a promising environmental performance in previous studies. 19,20 Table 1 provides the mass balance and key parameters of the assessed battery cells as obtained from the dimensioning tool.…”

“…A follow-up study investigated the impact of different precursor materials for the hard carbon anode materials, showing potential of reducing environmental impacts of SIB cells by sourcing hard carbon materials from organic waste material or fossil carbon material (petroleum coke). 20 Other works focused on specic aspects like costs or material demand. 11,21 The most recent publication with a specic environmental focus compares a NaNMC (NaNi 1/ parametrizable battery cell model for generating own inventory data.…”

Mixing, Domains, and Fast Li-Ion Dynamics in Ternary Li–Sb–Bi Battery Anode Alloys

“…Antimony and its alloys have been intensively studied in recent years as high-capacity anode materials in alkali metal-ion-based rechargeable batteries. − It has a theoretical storage capacity of 660 mAh/g, which is almost twice as high as graphite (372 mAh/g) that is currently used in commercial lithium-ion batteries (LIBs) and double that of hard carbon in emerging sodium-ion batteries. − Recently, antimony-based anodes have been extended to include potassium-ion batteries. , The range of antimony-alkali compounds that has been characterized is, however, considerably broader than just these two elements and can include up to three alkali metal ions from group I, from lithium to cesium, with the number of intermediate compounds increasing as one moves down the group of the periodic table. , In contrast to the more widely studied tin anodes, antimony shows good performance in conventional commercial carbonate-based electrolytes, making it a more suitable candidate to replace graphite in LIBs. − …”

Special issue on Materials and Society: the Circular Economy SAM-13

“…material scarcity. J. F. Peters, M. Abdelbaky, M. Baumann, M. Weil of the Karlsruhe Institute of Technology [5] addressed a particular example of this issue: indeed, sodium-ion batteries would be superior to lithium-ion batteries in terms of the availability of sodium vs. lithium, except that they need amorphous carbon anodes rather than graphite ones. Such anodes are produced one at a time for experimental purposes only today and, therefore, the details of industrial production are not available from the literature: the paper proposes to generate an LCI from modeling the process route for making them, an approach usually applied to describe future, not-yet existing technologies.…”