Process and Drying Behavior Toward Higher Drying Rates of Hard Carbon Anodes for Sodium‐Ion Batteries with Different Particle Sizes: An Experimental Study in Comparison to Graphite for Lithium‐Ion‐Batteries

Abstract

Lithium-ion batteries (LIB) and sodium-ion batteries (SIB) are both based on similar intercalation/insertion electrodes of the respective alkali ions into the active materials during charging and discharging. [1] Due to the larger and heavier sodium (Na) ion, a lower gravimetric and as well volumetric capacity than with lithium can be achieved. [2,3] However, given the resource availability of active materials from sustainable raw materials, at potentially low cost, SIB is one of the most promising post-Li batteries for widespread commercialization in the coming years. [4][5][6] Electrode processing of materials for SIB is expected to be very similar to the processing of LIB materials. However, the producibility and material processing challenges of potential electrode materials for anodes and cathodes are poorly investigated.Unlike for the LIB, graphite cannot be recommended as anode material for the SIB, because the formation of a Na-graphite-intercalation compound is energetically unfavorable and has a very low capacity. [7][8][9][10] Instead, hard carbon (HC) is considered to be a promising anode active material with good electrochemical performance for alkali-metal-ion batteries, such as SIBs. [8] The low material costs, the fact that HC can be produced from sustainable raw materials, and the low electrode potential are advantageous for the use of HC as an anode material for SIB. [11,12] However, high capacity losses in the first cycles and at high current rates are still challenging. The performance characteristics of HC active materials, which result from different synthesis methods, are different. [8] The selected precursor and the carbonization conditions, namely, the carbonization temperature, influence the nongraphitic structure of the HC produced and thus, its properties. [2,8,10] The non graphitic structure of the HC offers various areas where Na ions can be deposited. These include especially the regions between the graphite-like domains consisting of micropores and defect sites. Various models describing the storage mechanism, which are controversially discussed, can be found in the literature. [2,10,13,14]

Enabling Long‐term Cycling Stability of Na3V2(PO4)3/C vs. Hard Carbon Full‐cells

“…The electrodes investigated originate from large‐scale processing and are based on processes originally developed for LIB technology [34,35] . A detailed description focusing on NVP/C processing was recently provided by Klemens et al [36] . and here we briefly summarize the process.…”

“…The electrodes investigated originate from large-scale processing and are based on processes originally developed for LIB technology. [34,35] A detailed description focusing on NVP/C processing was recently provided by Klemens et al [36] and here we briefly summarize the process. The slurry for NVP/C cathodes was mixed in a dissolver (Dispermat SN-10, VMA Getzmann), where carbon black (C65, C-Nergy) and graphite (KS6L, Timical-Imerys), a PVDF (Solef 5130, Solvay) binder-solvent solution with 7.5 wt % and about 50 % of the required amount of NMP were dispersed.…”

“…In a last mixing step, an aqueous solution of styrene-butadiene rubber (SBR, 40 wt %, Zeon Europe) was added to adjust the final solid content to 43 wt %. The electrode coating and drying was carried out under quasi-isothermal drying conditions as a discontinuous process likewise described by Klemens et al [34][35][36] The slurries were applied to an aluminum current collector by a doctor blade (ZUA 2000.60, Zehntner) and dried by an impingement dryer and temperature controlled heating plates, resulting in drying rates of 0.75 g m À 2 s À 1 in both cases. After drying, the electrodes were calendered at 50 °C.…”

About drying phenomena of fuel cell and electrolyzer CCM inks: Selectivity of the evaporation of 1‐propanol/water mixtures

“…Drying rates and the associated production times are of great interest for the processing of electrodes. Higher drying rates (HDRs) can lead to different electrode properties [39,46,[59][60][61][62] but have an advantage over lower drying rates (LDRs) in terms of faster production times. Even the LDR when, for example, slow drying an electrode under ambient conditions in the laboratory also reflects the limiting case of NTU 𝑖,g → 0 and is described by gas-side controlled drying, which increases the importance of this drying case.…”

Enabling Long-term Cycling Stability of Na3V2(PO4)3/C vs. Hard Carbon Full-cells

“…The electrodes investigated originate from large-scale processing developed in cooperation with several institutes of KIT. [34][35][36] A detailed description focusing on NVP/C processing was recently provided by Klemens et al 37 and here we briefly summarize the process. The slurry for NVP/C cathodes was mixed in a dissolver (Dispermat SN-10, VMA Getzmann), where carbon black (C65, C-Nergy) and graphite (KS6L, Timical-Imerys), a PVDF (Solef 5130, Solvay) binder-solvent solution with 7.5 wt.% and about 50 % of the required amount of NMP were dispersed.…”