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All-solid-state lithium-ion batteries (ASSLBs) represent a promising breakthrough in battery technology owing to their high energy density and exceptional stability. When crafting cathode electrodes for ASSLBs, the solid electrolyte/cathode material interface is physically hindered by the specific morphology of carbon additive materials. In this paper, we examine the distribution of conductive additives within the electrode and its impact on the electrochemical performance of composites incorporating either nano-sized carbon black (CB) or micron-sized carbon nanofibers (CNF) into Ni-rich (LiNi0.8Co0.1Mn0.1O2) cathode material based composites. When nano-sized CB is employed as a conductive additive, it enhances the electrical conductivity of the composite by adopting a uniform distribution. However, its positioning between the solid electrolyte and cathode material leads to an increase in interfacial resistance during charge and discharge cycles, resulting in decreased electrochemical performance. In contrast, using micron-sized CNF as a conductive additive results in a reduction in the composite’s electrical conductivity compared to CB. Nevertheless, due to the comparatively uninterrupted interfaces between the solid electrolyte and cathode materials, it exhibits superior electrochemical characteristics. Our findings are expected to aid the fabrication of electrochemical-enhanced cathode composite electrodes for ASSLBs.

All-solid-state lithium-ion batteries (ASSLBs) have recently received significant attention due to their exceptional energy/power densities, inherent safety, and long-term electrochemical stability. However, to achieve energy- and power-dense ASSLBs, the cathode composite electrodes require optimum ionic and electrical pathways and hence the development of electrode designs that facilitate such requirements is necessary. Among the various available conductive materials, carbon black (CB) is typically considered as a suitable carbon additive for enhancing electrode conductivity due to its affordable price and electrical-network-enhancing properties. In this study, we examined the effect of different weight percentages (wt%) of nano-sized CB as a conductive additive within a cathode composite made up of Ni-rich cathode material (LiNi0.8Co0.1Mn0.1O2) and solid electrolyte (Li6PS5Cl). Composites including 3 wt%, 5 wt%, and 7 wt% CB were produced, achieving capacity retentions of 66.1%, 65.4%, and 44.6% over 50 cycles at 0.5 C. Despite an increase in electrical conductivity of the 7 wt% CB sample, a significantly lower capacity retention was observed. This was attributed to the increased resistance at the solid electrolyte/cathode material interface, resulting from the presence of excessive CB. This study confirms that an excessive amount of nano-sized conductive material can affect the interfacial resistance between the solid electrolyte and the cathode active material, which is ultimately more important to the electrochemical performance than the electrical pathways.

Sulfide electrolyte all-solid-state lithium-ion batteries (ASSLBs) that have inherently nonflammable properties have improved greatly over the past decade. However, determining both the stable and functional electrode components to pair with these solid electrolytes requires significant investigation. Solid electrolyte comprises 20–40% of the composite cathode electrode, which improves the ionic conductivity. However, this results in thick electrolyte that blocks the electron pathways in the electrode, significantly lowering the electrochemical performance. The application of conductive carbon material is required to overcome this issue, and, hence, determining the carbon properties that result in the most stable performance in the sulfide solid electrolyte is vital. This study analyzes the effect of the cathode conductive additive’s morphology on the electrochemical performance of sulfide electrolyte-based ASSLBs. Carbon black (CB) and carbon nanotubes (CNTs), which provide electron pathways at the nanoscale and sub-micron scale, and carbon nanofiber (CNF), which provides electron pathways at the tens-of-microns scale, are all tested individually as potential conductive additives. When the CNF, with its high crystallinity, is used as a conductive material, the electrochemical performance shows an excellent initial discharge capacity of 191.78 mAh/g and a 50-cycle capacity retention of 83.9%. Conversely, the CB and the CNTs, with their shorter pathways and significantly increased surface area, show a relatively low electrochemical performance. By using the CNF to provide excellent electrical conductivity to the electrode, the polarization is suppressed. Furthermore, the interfacial impedance across the charge transfer region is also reduced over 50 cycles compared with the CB and CNT composite cells. These findings stringently analyze and emphasize the importance of the morphology of the carbon conductive additives in the ASSLB cathode electrodes, with improvements in the electrochemical performance being realized through the application of long-form two-dimensional crystalline CNFs.

Carbon nanotubes (CNTs) are being used as a conductive material to achieve fast charging/discharging properties in high current density LIB systems. However, it is difficult to form a well-distributed electron transfer network within the electrode using CNTs due to their high aggregational properties. In this paper, we propose a strategy to fabricate the positive electrode with well-dispersed CNTs, controlling the solid content and sonication process of the slurry using LiNi0.8Co0.1Mn0.1O2 as the cathode materials. The CNTs are typically not well-mixed within the active material composite and aggregation occurs on the electrode surface in low solid content of under 50 wt%. When the solids content is as high as 70 %, CNTs are more evenly distributed in the electrode as bundled particles, however, there was no performance improvement using the ultra-sonication process. The CNTs at a mass ratio of CNTs at 4 wt% are well distributed in the electrode in 60 wt% of solid content, resulting in improved capacity retentions of 99.1 % after 100 cycles at a current density of 1C. When the electrochemical performance with CNTs was compared with Super P according to 1,2,3 and 4 wt% at a solid content of 60 %, the electrode using CNTs has a generally improved electrochemical performance due to the stable H1-M phase transition and stable average voltage during charging/discharging. Additionally, the excellent cycle ability at 5C with CNTs (92.8 % of capacity retention after 100 cycles) is helped by the fact that little polarization was observed compared with the Super P cells.

Lithium-ion batteries (LIBs) continue to dominate the battery market with their efficient energy storage abilities and their ongoing development. However, at high charge/discharge C-rates their electrochemical performance decreases significantly. To improve the power density properties of LIBs, it is important to form a uniform electron transfer network in the cathode electrode via the addition of conductive additives. Carbon nanotubes (CNTs) with high crystallinity, high electrical conductivity, and high aspect ratio properties have gathered significant interest as cathode electrode conductive additives. However, due to the high aggregational properties of CNTs, it is difficult to form a uniform network for electron transfer within the electrode. In this study, to help fabricate electrodes with well-dispersed CNTs, various electrodes were prepared by controlling (i) the mixing order of the conductive material, binder, and active material, and (ii) the sonication process of the CNTs/NMP solution before the electrode slurry preparation. When the binder was mixed with a well sonicated CNTs/NMP solution, the CNTs uniformly adsorbed to the then added cathode material of LiNi0.6Co0.2Mn0.2O2 and were well-dispersed to form a flowing uniform network. This electrode fabrication process achieved > 98.74% capacity retention after 50 cycles at 5C via suppressed polarization at high current densities and a more reversible H1-M phase transition of the active material. Our study presents a novel design benchmark for the fabricating of electrodes applying well-dispersed CNTs, which can facilitate the application of LIBs in high current density applications.

Abstract The increasing adoption of Ni‐rich cathode active materials in commercial liquid electrolyte Lithium‐ion batteries (LIBs) is testament to the improvements in the cathode stability through various surface modification strategies. The development of a deeper understanding of the cathode/electrolyte interface in LIBs has resulted in coatings capable of mitigating both surface and bulk cathode degradation mechanisms. However, due to increasing demands for safe and high energy density cells, a large portion of the research has now shifted towards applying Ni‐rich cathode active materials in inherently safer all‐solid‐state Lithium‐ion batteries (ASSLBs), with the resulting cathode surface modification strategies evolving differently. In this regard, a review outlining the surface modification strategies of Ni‐rich cathode materials applied in both LIB and ASSLB systems is provided. Within, a review of the traditional, advanced and specialized surface modification strategies of each system is discussed, along with a final perspective on the likely future direction of research regarding the design of system‐specific Ni‐rich cathode‐based surface modification strategies.