Designing Graphite‐Based Positive Electrodes and Their Properties in Dual‐Ion Batteries Using Particle Size‐Adjusted Active Materials

Abstract

In almost all state‐of‐the‐art lithium‐ion batteries, the negative electrode is made from graphite. For dual‐ion batteries (DIBs), graphite electrodes can even be used as negative and positive electrodes as the electrolyte provides both cations and anions for energy storage. As the amount of active material is very high in graphite electrodes, one of the main structure‐controlling parameters is its particle size distribution (PSD). Based on changes in the active material particle size and resulting changes in electrode structure, the corresponding cell characteristics like coulombic efficiency or power density are strongly affected. Herein, results for graphite positive electrodes manufactured with different PSDs of one typical commercial synthetic graphite are displayed. A high‐performance single‐wheel air classifier is used to create the differently distributed graphite particle fractions that do not vary in particle shapes for all fractions created. To gain a better understanding of the particle size impact on electrode properties, the electronic and mechanical properties, as well as the electrode structure, are investigated. The electrochemical performance of the Li metal/graphite system is correlated with structure properties influenced by PSD.

Impact of Particle Size Distribution on Performance of Lithium‐Ion Batteries

“…A further decrease in particle size will in turn cause negative effects on the cell performance, whereby the negative effect is increasing with decreasing particle size and this can lead to strong performance losses for very small particles. In comparison to previous studies, the particle size x 50 from F1 is less than half the size of the other small investigated x 50 graphitic particle sizes (around 3 to 4 μm) and about 2 to 16 times smaller than commonly used x 50 particle sizes [25,27,42] …”

“…In comparison to previous studies, the particle size x 50 from F1 is less than half the size of the other small investigated x 50 graphitic particle sizes (around 3 to 4 μm) and about 2 to 16 times smaller than commonly used x 50 particle sizes. [25,27,42] Besides differences in performance, the different PSD also impact degradation. Discharge capacity of F3 decreased significantly during the first 29th cycles.…”

“…For example, Ender et al [41] characterized the polydispersity of graphite through 3D reconstructed X-ray tomography and concluded that the pore network of the high-energy materials is limiting the electrolyte transport. Nowak et al [42] assessed experimentally the impact of particle size as well as PSD on a dual-ion battery system. Capone et al [43] studied the effect of PSD for red phosphoruscarbon composite anode for sodium-ion batteries.…”

“…characterized the polydispersity of graphite through 3D reconstructed X‐ray tomography and concluded that the pore network of the high‐energy materials is limiting the electrolyte transport. Nowak et al [42] . assessed experimentally the impact of particle size as well as PSD on a dual‐ion battery system.…”

Analysis of Lithium‐Ion Battery State and Degradation via Physicochemical Cell and SEI Modeling

“…They estimated the mass-specific surface area of different particle size distributions via the Brunauer-Emmett-Teller (BET) theory. [68] Depending on the median particle size of the sample, the BET-based specific surface area is roughly three to nine times higher than the corresponding approximation with spherical particles. Such an underestimation would result into a proportional overestimation of the SEI thickness, which would explain the difference to experiments.…”