[en] Li_1_+_xAl_xTi_2_-_x(PO_4)_3 (LATP) solid electrolytes are prepared by hydrothermal reaction as an effective method to yield moderate ionic conductivity adoptable in actual lithium-ion batteries. Particularly examined in this study are the effects of the synthesis conditions, such as Al dopant concentration (x), hydrothermal reaction time, and calcination and sintering temperatures, on the ionic conductivity of the synthesized LATP. Through repeated synthesis and characterizations of the LATPs by variation of the values of condition variables, the optimum condition for the best LATP with adequate ionic conductivity applicable to actual lithium batteries are determined to be x = 0.3 or 0.4, a hydrothermal reaction time of 12 h, and calcination and sintering temperatures of 600 °C and 900 °C, respectively

[en] Layered electrodes of electrodeposited RuO_2 (eRuO_2) and polyaniline (ePAn) are prepared on a platinum substrate to yield ePAn-on-eRuO_2 and eRuO_2-on-ePAn electrodes and their supercapacitive properties are investigated. The eRuO_2 electrode forms a compact stratified structure with nearly flat surfaces by electrodeposition from a RuCl_3·3H_2O-based solution, whereas the ePAn electrode forms densely connected particles or particle aggregates by the electrodeposition from aniline solution. In the scan rate range of 20–1000 mV s"−"1, specific capacitance (810–575 F g"−"1) of ePAn-on-eRuO_2 electrode is superior by the higher probability to occur redox reaction and proton diffusion due to particulate surface and inner pores of the upper layer (ePAn), respectively. In contrast, the eRuO_2-on-ePAn electrode loses the specific capacity (680–550 F g"−"1) but achieves higher capacity retention ratio (81%) by flat compact surface of the upper layer (eRuO_2).

[en] Despite extensive studies on lithium-metal batteries (LMBs) that have garnered considerable attention as a promising high-energy-density system beyond current state-of-the-art lithium-ion batteries, their application to flexible power sources is staggering due to the difficulty in simultaneously achieving electrochemical sustainability and mechanical deformability. To address this issue, herein, a new electrode architecture strategy based on conductive fibrous skeletons (CFS) is proposed. Lithium is impregnated into nickel/copper-deposited conductive poly(ethylene terephthalate) nonwovens via electrochemical plating, resulting in self-standing CFS–Li anodes. The CFS–Li anodes exhibit stable Li plating/stripping cyclability and mechanical deformability. To achieve high-capacity flexible cathodes, over-lithiated layered oxide (OLO) particles are compactly embedded in conductive heteronanomats (fibrous mixtures of multiwalled carbon nanotubes and functional polymer nanofibers). The conductive heteronanomats, as CFS of OLO cathodes, provide bicontinuous electron/ion conduction pathways without heavy metallic current collectors and chelate metal ions dissolved from OLO, thus improving the areal capacity, redox kinetics, and cycling retention. Driven by the attractive characteristics of the CFS–Li anodes and CFS–OLO cathodes, the resulting CFS–LMB full cells provide improvements in the cyclability, rate performance, and more notably, (cell-based) gravimetric/volumetric energy density (506 Wh kg${}_{cell}$${}^{-<!--\; ???\; -->1}$/765 Wh L${}_{cell}$${}^{-<!--\; ???\; -->1}$) along with the exceptional mechanical flexibility. (© 2021 Wiley-VCH GmbH)

[en] A pouch-type flexible thin-film lithium-ion battery is fabricated by sequential screen-printing (wet) processes to produce consecutive layers of a current collector, positive and negative electrodes, and a gel polymer electrolyte. Optimum conditions of each process are determined by adjusting the paste or slurry compositions to achieve lower surface resistance of each layer (current collector and electrodes) and higher ionic conductivity of the gel polymer electrolyte. The fabricated flexible thin-film lithium-ion battery (5.5 × 5.5 cm"2, 325 μm thick) shows superior electrochemical performance, including an energy density of 292.3 Wh L"−"1 based on electrode size (4.0 × 4.0 cm"2), an initial discharge capacity of 2.5 mAh cm"−"2 per electrode area, and capacity retention ratio of over 68% at the 50th cycle. To further improve the battery performance, the wet processes are modified by adopting hybrid (dry-wet) processes, which mainly consist of the formation of metallic current collector layers (Al and Cu) using a thermal evaporator and another optimized gel polymer electrolyte, to achieve an energy density of 332.8 Wh L"−"1 and capacity retention ratio of 84% at the 50th cycle. Cell flexibility is also confirmed by stable open circuit voltages after the system is subjected to several hundred iterations of bending, stretching, and even folding. There is the possibility that the suggested wet and dry-wet processes can be expanded to a high-speed mass-production roll-to-roll process

[en] Highlights: • A high energy density lithium metal battery is operated at high cut-off voltage of 4.6 V. • A new sulfite-type additive, BDTD is suggested for high voltage operating lithium metal batteries. • BDTD forms SEI and CEI on the surface of lithium metal anode NMC622 cathode, respectively. -- Abstract: The combination of high specific-capacity lithium (Li) metal anode and high cut-off voltage in Li secondary batteries provides an innovative method to realize high energy-density rechargeable batteries that satisfy the needs of future applications. However, an upgrade of both the cathode and anode is vital to establish high-voltage lithium metal batteries (LMB) concepts. In this study, we fabricated an electrolyte additive, [4, 4′-bi(1,3,2-dioxathiolane)] 2,2′-dioxide (BDTD), based on a novel sulfite-type additive and applied in LMB. Suppression of the Li dendrite growth on the Li metal anode was ensured by homogeneous Li plating in Li/Li symmetric cells. Scanning electron microscopy images demonstrated anode stabilization due to the introduction of the BDTD additive. In addition, X-ray photoelectron spectroscopy results confirmed the stabilization of the LiNi_0.6Mn_0.2Co_0.2O₂ cathode by protective cathode-electrolyte interphase made from the BDTD additive. This single additive introduced in the electrolyte enhanced both electrodes synergistically, and thus it resulted in an extended cycle life with high capacity retention in the high-voltage operation (4.6 V). We believe that this study will open new avenues for fabricating batteries with high-energy-density from high-voltage LMBs via this dual-function additive.

[en] We prepared and optimized the ionically conducting perovskite-type Li_0.33La_0.56TiO₃ by an adipic acid-assisted sol-gel process. A high ionic conductivity of 0.131 mS cm⁻¹ was obtained at an ambient temperature by adjusting the synthesis temperature, holding time, and cooling process. A dramatic improvement in the Li_0.33La_0.56TiO₃ conductivity was noted in each step. Interestingly, a tetragonal-to-cubic structural transition was evident during the quenching process unlike in the conventional slow cooling process. An increase in the bottleneck site volume was observed that facilitated Li⁺ ion migration for enhanced conductivity. - Highlights: • Adipic acid assisted sol-gel process is utilized to prepare Li_0.33La_0.56TiO₃. • High ambient temperature ionic conductivity of 0.131 mS cm⁻¹ is realized. • Transition from tetragonal to cubic is one of the main reason for such conductivity.

[en] To use as an anode material of lithium batteries, carbon-coated TiO₂ nanotubes are prepared by hydrothermal reaction of rutile particles, subsequent sol–gel mixing with poly(vinyl pyrrolidone), and heat treatment at 300–500 °C. The carbon-coated TiO₂ nanotubes are also characterized by morphology observation, crystalline property analysis, potentiostatic redox behaviors, and galvanostatic discharge–charge evaluations at low and high rates. When annealed at 300 °C, the amorphous phase of carbon layers which are covered on the TiO₂ nanotubes dominates the anatase TiO₂ nanocrystalline phase. When annealed at 500 °C, the carbon-coated TiO₂ nanotubes exhibit superior cyclic performance and high-rate capability, due to the crystalline phase in the carbon-coated layer formed by annealing at high temperature. -- Highlights: ► Carbon-coated TiO₂ nanotubes are prepared by sol–gel mixing with poly(vinyl pyrrolidone). ► The poly(vinyl pyrrolidone) component forms partially crystalline carbon layer. ► The carbon layer allows an excellent cycle performance and high-rate capability for lithium-ion batteries.

[en] Highlights: • PEGDA-based gel polymer electrolytes are synthesized on separator via thermal polymerization of PEGDA with a thermal initiator and a LiPF₆-/EC/DMC solution. • The nonwoven PVdF separator shows good absorption of gel polymer electrolytes due to high porosity and good compatibility with the precursor solution. • The inclusion of the PEGDA-based gel polymer electrolytes prolongs the cycle life through a better capacity retention ratio in lithium-ion batteries. - Abstract: Porous polyethylene (PE) or nonwoven poly(vinylidene fluoride) (PVdF) separator-supported gel polymer electrolytes are realized by thermal polymerization of a precursor solution consisting of poly(ethylene glycol)diacrylate (PEGDA) and an electrolyte solution (1 M LiPF₆ in an equal-volume mixture of ethylene carbonate and dimethyl carbonate). The polymerization conditions are optimized to include a PEGDA content of 3 wt.% in the precursor solution and subsequent heat treatment at 80 °C for 10 min. Even though the gelled PEGDA electrolyte has a lower ionic conductivity than the electrolyte solution, a Li_xCoO₂/graphite full-cell that has a gel electrolyte with optimized PEGDA content on the PVdF separator achieves a battery performance superior to the one with PE. The best battery performances achieved are a high discharge capacity (116 mAh g⁻¹), a good high-rate capability (95 mAh g⁻¹ at 5.0 C-rate), and a high capacity retention ratio (90%) after the 100th cycle. This enhancement is due to the incorporation of a polar electrolyte solution that is entrapped by the polar PEGDA matrix within the nonwoven PVdF separator, which is a more suitable host that is able to well absorb and preserve the gel electrolyte

[en] From mixed (anatase and rutile) bulk particles, anatase TiO₂ nanotubes are synthesized in this study by an alkaline hydrothermal reaction and a consequent annealing at 300-400 ^oC. The physical and electrochemical properties of the TiO₂ nanotube are investigated for use as an anode active material for lithium-ion batteries. Upon the first discharge-charge sweep and simultaneous impedance measurements at local potentials, this study shows that interfacial resistance decreases significantly when passing lithium ions through a solid electrolyte interface layer at the lithium insertion/deinsertion plateaus of 1.75/2.0 V, corresponding to the redox potentials of anatase TiO₂ nanotubes. For an anatase TiO₂ nanotube containing minor TiO₂(B) phase obtained after annealing at 300 ^oC, the high-rate capability can be strongly enhanced by an isotropic dispersion of TiO₂ nanotubes to yield a discharge capacity higher than 150 mAh g^-1, even upon 100 cycles of 10 C-rate discharge-charge operations. This is suitable for use as a high-power anode material for lithium-ion batteries.

[en] The graphite/silicon-based diffusion-dependent electrodes (DDEs) are one of the promising electrode designs to realize high energy density for all-solid-state batteries (ASSBs) beyond conventional composite electrode design. However, the graphite/silicon-based electrode also suffers from large initial irreversible capacity loss and capacity fade caused by significant volume change during cycling, which offsets the advantages of the DDEs in ful-cell configuration. Herein, a new concept is presented for DDEs, dry pre-lithiated DDEs (PL-DDEs) by introducing Li metal powder. Since Li metal powder provides Li ions to graphite and silicon even in a dry state, the lithiation states of active materials is increased. Moreover, the residual Li within PL-DDE further serves as an activator and a reservoir for promoting the lithiation reaction of the active materials and compensating for the active Li loss upon cycling, respectively. Based on these merits, ASSBs with PL-DDE exhibit excellent cycling performance with higher columbic efficiency (85.2% retention with 99.6% CE at the 200th cycle) compared to bare DDE. Therefore, this dry lithiation process must be a simple but effective design concept for DDEs for high-energy-density ASSBs. (© 2023 The Authors. Advanced Energy Materials published by Wiley‐VCH GmbH)