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Flexible Li-ion batteries have shown great promise in powering wearable electronic devices due to their high energy/power densities and long cycling time. However, coordinating the promising electrochemical performance and flexibility for different applications is still a big challenge. Herein, we report a highly conductive graphene-modified mesoporous anatase TiO 2 (M-TiO 2 -GS) hierarchical film electrode for flexible Li-ion battery anode via a two-step vacuum filtration method. In such a hierarchical film electrode, the down-layer composed of bare graphene component provides ideal mechanical flexibility and electronic conductivity, and the hybrid top-layer composed of both graphene and active M-TiO 2 guarantees effective Li+ and electrons transport pathways and acts as the active layer for energy storage. The designed M-TiO 2 -GS film electrode delivers a reversible capacity of 205 and 76 mAh g−1 at rates of 0.5C and 20C, respectively, and high capacity retention of ∼70.5% after 3500 cycles at 5C. When packed in flexible cells, the M-TiO 2 -GS electrode can also maintain a highly reversible capacity and outstanding cycling stability in both flating and benting conditions. This work may provide a promising anode candidate for the next-generation flexible LIBs and the developed two-step filtration method can be readily applied to other flexible electrodes. Less defective graphene nanosheets with relatively high conductivity have been employed to fabricate a free-standing flexible M-TiO 2 -GS anode for LIBs through a two-step vacuum filtration method. Layer-by-layer assembled GS networks connected with M-TiO 2 cakes provides criss-crossed fast electrons transport paths and available ions diffusion channels, leading to great Li+ storage behavior. Image 1 • Highlights to Electrochimica Acta . • A graphene-modified TiO 2 hierarchical flexible film electrode is designed. • The designed film electrode has optimized electrochemical kinetic properties. • The electrode shows excellent performance in both free and bending conditions. [ABSTRACT FROM AUTHOR]

Abstract: Flexible supercapacitors have potential for wearable energy storage due to their high energy/power densities and long operating lifetimes. High electrochemical performance with robust mechanical properties is highly desired for flexible supercapacitor electrodes. Usually, the mechanical properties are improved by choosing high flexible textile substrates but at the much expense of electrochemical performance due to the nonideal contact between conductive materials and textile substrates. Herein, the authors present an efficient, scalable, and general strategy for the simultaneous fabrication of high‐performance textile electrodes and yarn electrodes. It is interesting to find that the conformal reduced graphene oxide (RGO) layer is uniformly and successively painted on the surface of SnCl2 modified polyester fibers (M‐PEF) via a repeated “dyeing and drying” strategy. The large‐area textile electrodes and ultralong yarn electrodes are fabricated by using RGO/M‐PEF as substrate with subsequent deposition of polypyrrole. This work provides new opportunities for developing high flexible textile electrodes and yarn electrodes with further increased electrochemical performance and scalable production. [ABSTRACT FROM AUTHOR]

Two dimensional (2D) nanomaterials have great application potential in developing the energy storage systems with high volumetric energy and power densities. However, due to the sluggish ion diffusion, achieving both high volumetric capacities and rate performance in thick and dense 2D nanomaterial electrodes is still challenging. Here, we report a femtosecond laser drilling method to introduce appropriate micro-hole arrays into the thick and dense electrodes for facilitated ion transport. These micro-hole arrays shorten ion transport paths and thus significantly reduce the ion transport resistance. More importantly, constructing micro-hole arrays with hole spacing higher than 40 μm rarely sacrifices the density of the electrode. The effectiveness of micro-hole arrays to improve capacities and rate performance of the thick and dense electrodes is evidenced by two model cases: a TiO 2 -based electrode constructed with the upper-layer TiO 2 -coated graphene hybrids and under-layer graphene (dTiO 2 -G/G), and a graphene electrode. As presented, the micro-hole array with a hole spacing of 40 μm decreases the ionic resistance of the dTiO 2 -G/G electrode, and consequently improves the volumetric capacity at 10C from 15.8 to 97 mA h cm−3. Such micro-hole array also improves the volumetric capacity and rate performance of the graphene electrode. • Femtosecond laser drills micro-hole arrays in thick and dense 2D material electrodes. • Micro-hole arrays improve the volumetric performance of thick and dense electrodes. • A wet pressing process is proposed to densify 2D material electrodes. [ABSTRACT FROM AUTHOR]

2D nanomaterials have attracted intensive attention in the area of compact energy storage owing to their large packing densities. However, the highly tortuous and lengthy channels in conventional 2D nanomaterial electrodes cause sluggish ion diffusion kinetics and seriously reduce the capacity. Herein, we report a simple method adopting diamond wire saw cutting technology to construct a compact vertically aligned TiO 2 -graphene nanosheet electrode (VATiO 2 -G) with a large thickness of 130 μm. The vertical alignment not only provides short and less tortuous ion transport pathways to facilitate ion diffusion kinetics, but also improves the electronic conductivity to promote electron transport across the electrode. Accordingly, the VATiO 2 -G anode for lithium-ion batteries simultaneously exhibits high volumetric and areal capacities of 243 mA h cm−3 and 3.16 mA h cm−2 at 2.8 mA cm−2, respectively. This work exploits a general method to attain vertically aligned architecture in dense and thick 2D nanomaterial electrodes. [ABSTRACT FROM AUTHOR]

Micro-sized Sb particles were dually encapsulated in carbon layer and MXene network with robust interfacial bonding of Sb-O-C and C-O-Ti improving the volumetric performance. [Display omitted] • Micro-sized Sb dually encapsulated in carbon layer and Ti 3 C 2 T x MXene network. • Robust interfacial bonding of Sb O C and C O Ti is formed. • The robust interfacial bonding promotes efficient ion/electron transport. High-theoretical-capacity antimony (Sb) anodes hold promise for high-performing sodium-ion storage, yet suffer from huge volume change. In solving this obstacle, traditional strategies normally incorporate nanosized Sb with low-density conductive materials, which, in turn, sacrifice volumetric performance. Here, we report micro-sized Sb particles (m-Sb) dually encapsulated in carbon layer and densely-packed Ti 3 C 2 T x MXene network (m-Sb/C@MXene), forming a highly-confined composite with robust interfacial bonding of Sb O C between m-Sb and the carbon layer, and C O Ti between the carbon layer and MXene. The m-Sb/C@MXene anode displays a high volumetric capacity of 482.6 mAh cm−3 and a high volumetric capacity retention of 407.1 mAh cm−3 after 100 cycles at 0.1 A/g. A high-rate capacity of 191.0 mAh cm−3 at 10 A/g has also been achieved. Such superior performance stems from its unique architecture highly confined by the conductive and elastic network, which can provide fast electron/ion transport and effectively buffer volume expansion. Furthermore, ex-situ X-ray diffraction reveals that this hierarchical structure not only stabilizes m-Sb but also enhances ion transport kinetics by promoting the amorphization of m-Sb, thus delivers the excellent capacity and rate performance. This work offers an effective design of high-volumetric-capacity anode materials for their practical applications in sodium-ion energy storage. [ABSTRACT FROM AUTHOR]