Hyeon-Gyun Im

LiFePO₄-type (LFP) batteries have attracted significant attention in most battery manufacturing industries due to their long lifespan, high-temperature safety, and low cost of raw materials. However, as an active material, LFP still suffers from several intrinsic drawbacks, including poor conductivity, a low Li⁺ diffusion coefficient, low capacity, and a lack of electrochemical stability, primarily due to conventional fluorine-based binders. Here, we report a simple yet effective approach to developing a fluorine-free binder based on a robust cycloaliphatic epoxy-based siloxane nanohybrid material (CES) to achieve high electrochemical stability in LFP batteries. The high content of silanol moieties in CES induces a strong affinity for the active material and conductive agent, significantly improving rheological (thixotropy) and mechanical (adhesion and cohesion) properties, which enable the formation of a uniformly coated electrode. As a result, we achieved superior electrochemical performance and stability in CES-applied electrodes compared to those with conventional fluorine-based binders. We investigate the reasons behind the contribution of CES to the electrochemical stability of LFP batteries through various analyses. The high thermal and oxidation stability of CES effectively prevents degradation of LFP-based active materials. Our binder development strategy offers a significant breakthrough in replacing conventional fluorine-based binders, advancing the development of high-performance and stable secondary batteries.

Although the high‐energy Ni‐rich layered cathodes suffer from undesirable surface reactions with the electrolyte, the polyvinylidene fluoride (PVDF) binder has a limitation on surface stabilization because of its weak affinity and low adhesion/cohesion. Here, it is demonstrated that the novel fluorine‐free and hydroxyl‐rich siloxane nanohybrid (SNH) binder can enhance the electrochemical performances of LiNi _0.8 Mn _0.1 Co _0.1 O ₂ cathode (NCM811) via successful surface stabilization. The high silanol content in the SNH binder enhances the affinity to both NCM811 and conductive agent, facilitating uniform electron/ion pathways with high mass loading, improved shear thinning, and superior mechanical properties. Moreover, the fluorine‐free organic‐inorganic hybrid structure prevents the dissolution of transition metals, active material structural changes, and electrolyte interaction, leading to greatly enhanced cyclability of the SNH‐based NCM811 electrode (≈81.9% in half‐cell; ≈87.82% in full‐cell after 200 cycles) compared to PVDF‐based NCM811 electrode (≈58.8% in half‐cell; ≈61.24% in full‐cell after 200 cycles). Various analyses also indicate that the application of the fluorine‐free SNH binder successfully stabilizes both the surface and bulk structure of the NCM811 cathode during charge/discharge. The binder design represents a straightforward yet highly effective approach to achieving remarkably prolonged cyclability in lithium‐ion batteries, surpassing the performance of other fluorine‐based or polymer‐based binders.

A nano-sized CuSO₄/carbon (N-CSO/C) composite achieves outstanding electrochemical performances with a high average operating voltage of ∼2.8 V (vs. K⁺/K).

Metal nanowires (NWs) are promising transparent conducting electrode (TCE) materials because of their excellent optoelectrical performance, intrinsic mechanical flexibility, and large-scale processability. However, the surface roughness, thermal/chemical instability, and limited electrical conductivity associated with empty spaces between metal NWs are problems that are yet to be solved. Here, we report a highly reliable and robust composite TCE/substrate all-in-one platform that consists of crystalline indium tin oxide (c-ITO) top layer and surface-embedded metal NW (c-ITO/AgNW-GFRH) films for flexible optoelectronics. The c-ITO top layer (thickness: 10–30 nm) greatly improves the electrical performance of a AgNW-based electrode, retaining its transparency even after a high-temperature annealing process at 250 °C because of its thermally stable basal substrate (i.e., AgNW-GFRH). By introducing c-ITO thin film, we achieve an extremely smooth surface (R_rms < 1 nm), excellent optoelectrical performance, superior thermal (> 250 °C)/chemical stability (in sulfur-contained solution), and outstanding mechanical flexibility (bending radius = 1 mm). As a demonstration, we fabricate flexible organic devices (organic photovoltaic and organic light-emitting diode) on c-ITO/AgNW-GFRH films that show device performance comparable to that of references ITO/glass substrates and superior mechanical flexibility. With excellent stability and demonstrations, we expect that the c-ITO/AgNW-GFRHs can be used as flexible TCE/substrate films for future thin-film optoelectronics.