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F-doped carbon layer coating is an effective surface modification method to enhance the intrinsic conductivity of active materials and facilitate the accommodation of solvated Li+ ions near the carbon surface. Furthermore, it induces the formation of an effective LiF-rich solid electrolyte interface with high electrochemical stability and facile surface diffusion of Li+ ion owing to its low energy barrier. Therefore, by employing a cost-effective coating material poly(vinylidene fluoride) (PVDF), high electrochemical performance in rate capability, cyclability, and energy/power density can be easily achieved without using expensive materials. A uniform and thin coating of an F-doped amorphous carbon layer was fabricated on the natural graphite (NG) surface using 1 wt % of PVDF (NG-F1), followed by a carbonization step. This process resulted in a high energy density of 59.8 Wh kg–1 at a current density of 5.0 A g–1 (100C) in a full cell configuration for lithium-ion capacitors (LICs). In comparison, the pristine NG demonstrated an energy density of 47.3 Wh kg–1. Furthermore, this LIC full cell with NG-F1 showed a lower charge-transfer resistance and a higher capacity retention of 99.4% than pristine NG, even after 500 charge–discharge cycles at 3C.

Mixed transition metal oxides are promising anodes to meet high‐performance energy storage materials; however, their widespread uses are restrained owing to limited theoretical capacity, restricted synthesis methods and templates, low conductivity, and extreme volume expansion. Here, Mn3‐xFexO4 nanosheets with interconnected conductive networks are synthesized via a novel self‐hybridization approach of a facile, galvanic replacement‐derived, tetraethyl orthosilicate‐assisted hydrothermal process. An exceptionally high reversible capacity of 1492.9 mAh g−1 at 0.1 A g−1 is achieved by producing Li‐rich phase through combined synergistic effects of amorphous phases with interface modification design for fully utilizing highly spin‐polarized surface capacitance. Furthermore, it is demonstrated that large surface area can effectively facilitate Li‐ion kinetics, and the formation of interconnected conductive networks improves the electrical conductivity and structural stability by alleviating volume expansion. This leads to a high rate capability of 412.3 mAh g−1 even at an extremely high current density of 10 A g−1 and stable cyclic stability with a capacity up to 921.9 mAh g−1 at 2 A g−1 after 500 cycles. This study can help to overcome theoretically limited electrochemical properties of conventional metal oxide materials, providing a new insight into the rational design with surface alteration to boost Li‐ion storage capacity.

Nowadays, thickness optimization of an electrode is considered an effective approach to achieve a high energy density or high areal capacity of Li-ion batteries. In this paper, we report a simple electrospinning technique to develop free-standing sheet bundles of lithium titanium oxide (LTO) nanowires with a readily controlled thickness of electrodes. The LTO nanowire sheet bundles (LNSBs) can show a very high areal capacity as an anode due to its microscale layer-by-layer configuration in which the nanoscale LTO nanowires are networked in each microscale layer. Such unique structures with interspaces formed between the multiple stacked sheet layers should promote electrolytes to efficiently penetrate through the thick electrode layer. Nanoscale wire assemblies can also increase the transfer rates of ions and electrons during the lithiation/delithiation processes. Consequently, the fabricated LNSB electrode delivers an ultrahigh areal capacity of up to ca. 14.2 mA h cm–2 for the first cycle and ca. 6.5 mA h cm–2 for the 500th cycle at 0.2C rate current density, which is a much larger areal capacity than the commercial graphite anode (ca. 3.5 mA h cm–2). Such a high areal discharge capacity on a novel free-standing electrode design could provide an idea for advanced energy storage applications.