Ionic Conductor of Li₂SiO₃ as an Effective Dual-Functional Modifier To Optimize the Electrochemical Performance of Li₄Ti₅O₁₂ for High-Performance Li-Ion Batteries

Ionic conductor of Li₂SiO₃ (LSO) was used as an effective modifier to fabricate surface-modified Li₄Ti₅O₁₂ (LTO) via simply mixing followed by sintering at 750 °C in air. The electrochemical performance of LTO was enhanced by merely adjusting the mass ratio of LTO/LSO, and the LTO/LSO composite with 0.51 wt % LSO exhibited outstanding rate capabilities (achieving reversible capacities of 163.8, 157.6, 153.1, 147.0, and 137.9 mAh g^–1 at 100, 200, 400, 800, and 1600 mA g^–1, respectively) and remarkable long-term cycling stability (120.2 mAh g^–1 after 2700 cycles with a capacity fading rate of only 0.0074% per cycle even at 500 mA g^–1). Combining structural characterization with electrochemical analysis, the LSO coating coupled with the slight doping effect adjacent to the LTO surface contributes to the enhancement of both electronic and ionic conductivities of LTO

Improving the Electrochemical Performance of Li₂ZnTi₃O₈ by Surface KCl Modification

Inorganic salt of KCl was first employed as an effective modifier to modify Li₂ZnTi₃O₈ anode material via simply mixing in KCl solution followed by sintering at 800 °C in air. The Li₂ZnTi₃O₈ modified with 1.0 wt % KCl exhibited splendid rate capabilities (retaining reversible capacities of 225.6, 195.4, 178.0, 162.4, and 135.6 mAh g^–1 at 100, 200, 400, 800, and 1600 mA g^–1, respectively) and excellent long-term cycling stability (maintaining a capacity of 201.6 mAh g^–1 after 700 cycles). Combining structural characterization with electrochemical analysis, the KCl modification leads to simultaneous doping of K⁺ and Cl^– in Li₂ZnTi₃O₈, contributing to enhance the electronic and ionic conductivities of Li₂ZnTi₃O₈

Enhanced Electrochemical Performance of FeWO₄ by Coating Nitrogen-Doped Carbon

FeWO₄ (FWO) nanocrystals were prepared at 180 °C by a simple hydrothermal method, and carbon-coated FWO (FWO/C) was obtained at 550 °C using pyrrole as a carbon source. The FWO/C obtained from the product hydrothermally treated for 5 h exhibits reversible capacities of 771.6, 743.8, 670.6, 532.6, 342.2, and 184.0 mAh g^–1 at the current densities of 100, 200, 400, 800, 1600, and 3200 mA g^–1, respectively, whereas that from the product treated for 0.5 h achieves a reversible capacity of 205.9 mAh g^–1 after cycling 200 times at a current density of 800 mA g^–1. The excellent electrochemical performance of the FWO/C results from the combination of the nanocrystals with good electron transport performance and the nitrogen-doped carbon coating

Carbon-Coated Fe–Mn–O Composites as Promising Anode Materials for Lithium-Ion Batteries

Fe–Mn–O composite oxides with various Fe/Mn molar ratios were prepared by a simple coprecipitation method followed by calcining at 600 °C, and carbon-coated oxides were obtained by pyrolyzing pyrrole at 550 °C. The cycling and rate performance of the oxides as anode materials are greatly associated with the Fe/Mn molar ratio. The carbon-coated oxides with a molar ratio of 2:1 exhibit a stable reversible capacity of 651.8 mA h g^–1 at a current density of 100 mA g^–1 after 90 cycles, and the capacities of 567.7, 501.3, 390.7, and 203.8 mA h g^–1 at varied densities of 200, 400, 800, and 1600 mA g^–1, respectively. The electrochemical performance is superior to that of single Fe₃O₄ or MnO prepared under the same conditions. The enhanced performance could be ascribed to the smaller particle size of Fe–Mn–O than the individuals, the mutual segregation of heterogeneous oxides of Fe₃O₄ and MnO during delithiation, and heterogeneous elements of Fe and Mn during lithiation

Simple Preparation of Carbon Nanofibers with Graphene Layers Perpendicular to the Length Direction and the Excellent Li-Ion Storage Performance

Sulfur-containing carbon nanofibers with the graphene layers approximately vertical to the fiber axis were prepared by a simple reaction between thiophene and sulfur at 550 °C in stainless steel autoclaves without using any templates. The formation mechanism was discussed briefly, and the potential application as anode material for lithium-ion batteries was tentatively investigated. The carbon nanofibers exhibit a stable reversible capacity of 676.8 mAh/g after cycling 50 times at 0.1 C, as well as the capacities of 623.5, 463.2, and 365.8 mAh/g at 0.1, 0.5, and 1.0 C, respectively. The excellent electrochemical performance could be attributed to the effect of sulfur. On one hand, sulfur could improve the reversible capacity of carbon materials due to its high theoretical capacity; on the other hand, sulfur could promote the formation of the unique carbon nanofibers with the graphene layers perpendicular to the axis direction, favorable to shortening the Li-ion diffusion path

Li-Ion Storage Performance of Carbon-Coated Mn–Al–O Composite Oxides

The composites of manganese oxide and alumina (Mn–Al–O) with varied Mn/Al molar ratios were fabricated by a simple coprecipitation method and subsequently sintered at different temperatures. Carbon-coated oxides were prepared at 550 °C using pyrrole as the carbon source. Compared with the carbon-coated MnO prepared under the same conditions, the carbon-coated Mn–Al–O exhibits greatly enhanced electrochemical performance which is associated with both the Mn/Al molar ratio and sintering temperature. The carbon-coated composites with a ratio of 2:1 sintered at 600 °C could deliver a stable reversible capacity of 450 mAh g^–1 after 100 cycles at a current density of 100 mA g^–1 and the capacities of 373, 309, 245, and 175 mAh g^–1 at the densities of 200, 400, 800, and 1600 mA g^–1, respectively. The enhanced cycling and rate performance is attributed to the improved Li-ion conductivity owing to the formation of LiAlO₂ and the smaller particle size of MnO due to the dispersion effect of Al₂O₃

Li_1.3Al_0.3Ti_1.7(PO₄)₃ Behaving as a Fast Ionic Conductor and Bridge to Boost the Electrochemical Performance of Li₄Ti₅O₁₂

Li_1.3Al_0.3Ti_1.7(PO₄)₃ (LATP) is a Li-ion conductive solid electrolyte with high ionic conductivity; meanwhile, it also possesses relatively high electronic conductivity compared to those of the other fast ionic conductors. In this work, LATP was composited with Li₄Ti₅O₁₂ (LTO) at a mass ratio of 0.026 and calcined at 700 °C for 5 h. The composite delivers reversible capacities of 164.8, 156.3, 152.4, 146.5, 130.5, and 158.6 mAh g^–1 at the current densities of 100, 200, 400, 800, 1600, and 100 mA g^–1, respectively, as well as a capacity of 112 mAh g^–1 after cycling at 500 mA g^–1 for 1200 cycles. The appreciable performance is attributable to the three-dimensional Li-ion diffusion channels in LATP to facilitate Li-ion migration, and the local charge imbalance resulted from the substitution of Al³⁺ for Ti⁴⁺ to promote charge transfer in LTO, thus the LATP-composited LTO exhibits enhanced ionic and electronic conductivities, as well as the markedly boosted electrochemical performance

Uniform Surface Modification of Li₂ZnTi₃O₈ by Liquated Na₂MoO₄ To Boost Electrochemical Performance

Poor ionic and electronic conductivities are the key issues to affect the electrochemical performance of Li₂ZnTi₃O₈ (LZTO). In view of the water solubility, low melting point, good electrical conductivity, and wettability to LZTO, Na₂MoO₄ (NMO) was first selected to modify LZTO via simply mixing LZTO in NMO water solution followed by calcining the dried mixture at 750 °C for 5 h. The electrochemical performance of LZTO could be enhanced by adjusting the content of NMO, and the modified LZTO with 2 wt % NMO exhibited the most excellent rate capabilities (achieving lithiation capacities of 225.1, 207.2, 187.1, and 161.3 mAh g^–1 at 200, 400, 800, and 1600 mA g^–1, respectively) as well as outstanding long-term cycling stability (delivering a lithiation capacity of 229.0 mAh g^–1 for 400 cycles at 500 mA g^–1). Structure and composition characterizations together with electrochemical impedance spectra analysis demonstrate that the molten NMO at the sintering temperature of 750 °C is beneficial to diffuse into the LZTO lattices near the surface of LZTO particles to yield uniform modification layer, simultaneously ameliorating the electronic and ionic conductivities of LZTO, and thus is responsible for the enhanced electrochemical performance of LZTO. First-principles calculations further verify the substitution of Mo⁶⁺ for Zn²⁺ to realize doping in LZTO. The work provides a new route for designing uniform surface modification at low temperature, and the modification by NMO could be extended to other electrode materials to enhance the electrochemical performance

Combined Modification of Dual-Phase Li₄Ti₅O₁₂–TiO₂ by Lithium Zirconates to Optimize Rate Capabilities and Cyclability

The low electrical conductivity and ordinary lithium-ion transfer capability of Li₄Ti₅O₁₂ restrict its application to some degree. In this work, dual-phase Li₄Ti₅O₁₂–TiO₂ (LTOT) was modified by composite zirconates of Li₂ZrO₃, Li₆Zr₂O₇ (LZO) to boost the rate capabilities and cyclability. When the homogeneous mixture of LiNO₃, Zr­(NO₃)₄·5H₂O and LTOT was roasted at 700 °C for 5 h, the obtained composite achieved a superior reversible capacity of 183.2 mAh g^–1 to the pure Li₄Ti₅O₁₂ after cycling at 100 mA g^–1 for 100 times due to the existence of a scrap of TiO₂. Meanwhile, when the composite was cycled by consecutively doubling the current density between 100 and 1600 mA g^–1, the corresponding reversible capacities are 183.2, 179.1, 176.5, 173.3, and 169.3 mAh g^–1, signifying the prominent rate capabilities. Even undergoing 1400 charge/discharge cycles at 500 mA g^–1, a reversible capacity of 144.7 mAh g^–1 was still attained, denoting splendid cyclability. From a series of comparative experiments and systematic characterizations, the formation of LZO meliorated both the Li⁺ migration kinetics and electrical conductivity on account of the concomitant superficial Zr⁴⁺ doping, responsible for the comprehensive elevation of the electrochemical performance