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The oxygen vacancy modulated LiTiOPO4‐y was synthesized by simple hydrothermal and high‐temperature solid‐phase methods. X‐ray diffraction (XRD) test data analyses reveal that the density of oxygen defects in LiTiOPO4‐y can be affected by the hydrothermal reaction time. The electron paramagnetic resonance (EPR) showed signal peaks at g=2.003, which proved that oxygen defects were generated. X‐ray photoelectron spectroscopy (XPS) further demonstrated that oxygen defects exist in LiTiOPO4‐y, which led to the partial conversion of Ti4+ to Ti3+. The capacity of LiTiOPO4 was limited (less than 161 mAh g−1) by cycling potential range (0.5–3.0 V). The oxygen‐deficient LiTiOPO4‐y was used to enhance lithium‐ion storage performance by mediating voltage from 0.01 to 3.0 V. The initial capacity of oxygen‐deficient LiTiOPO4‐y, which was synthesized after hydrothermal treatment for 18 h, with an exposed (121) face, reached 563.5 mAh g−1 at the current density of 500 mA g−1. After 1500 cycles, the specific discharge capacity kept at 397.2 mAh g−1. In the oxygen‐defective LiTiOPO4‐y, multiple coordination unsaturated sites are exposed, which can not only significantly enhance ion diffusion and charge transfer, but also promote Li+ to more storage sites. [ABSTRACT FROM AUTHOR]

The cathode material Na 3 V 2 (PO 4) 2 F 3 of sodium-ion battery is well-known for its large number of ion migration channels and high working voltage. However, the electrochemical performance of Na 3 V 2 (PO 4) 2 F 3 is not very outstanding. Thus, in the present study, Na 3 V 2 (PO 4) 2 F 3 cathode materials were successfully synthesized by using the sol-gel method and mechanical milling method to enhance the electrochemical performance. The physicochemical properties of synthesized Na 3 V 2 (PO 4) 2 F 3 were investigated by using X-ray diffraction spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, transition electron microscopy. X-ray diffraction spectroscopy indicates that the doping of nitrogen and sulfur did not alter the crystal form of Na 3 V 2 (PO 4) 2 F 3. Transition electron microscopy image shows that Na 3 V 2 (PO 4) 2 F 3 has a thin carbon layer, and x-ray photoelectron spectroscopy illustrates the successful doping of nitrogen and sulfur into the carbon layer. The cyclic voltammetry curves show that the nitrogen and sulfur co-doped Na 3 V 2 (PO 4) 2 F 3 samples have good reversibility and low polarization. Materials with 15% thiourea has a high discharge specific capacity (126.9 mA h g−1 at 0.2 C) at the first cycle and excellent cycle stability (126.3 mA h g−1 after 100 cycles, a capacity retention of 99.5%) among the synthesized cathode materials. In the present study, the electrochemical performance of the Na 3 V 2 (PO 4) 2 F 3 cathode material was enhanced by regulation of co-doping of nitrogen and sulfur atoms. [ABSTRACT FROM AUTHOR]

Europium-modified TiO2 with different valence states was prepared by a hydrothermal method and calcined in air. Microscopic analyses revealed that the average particle size of europium-modified TiO2 nanoparticles is approximately 11.03 nm, and the particle size distribution is narrow. In addition, defects were introduced into TiO2 by doping with europium. X-ray photoelectron spectroscopy (XPS) showed different valence states of Eu3+/Eu2+ in Ti1−xEuxO2 (x = 0.04). A mechanism for europium-modified TiO2 with different valence states is proposed. Europium-modified TiO2 features excellent rate performance and long-term stability. The discharge capacity of Ti1−xEuxO2 (x = 0.04) reached 417.5 mA h g−1 at the initial cycle and retained 219.1 mA h g−1 at 5C after 600 cycles. When it is cycled at 50C, the rate discharge capacity is maintained at 134.9 mA h g−1. The electronic conductivity of TiO2 was significantly improved by doping with different valence states of europium (Eu3+/Eu2+) due to the existence of mixed valence states of Ti4+/Ti3+. [ABSTRACT FROM AUTHOR]

Oxygen-deficient Li 1.3 Al 0.3 Ti 1.7 (PO 4) 3 (LATP) was prepared using a hydrothermal method followed by high-temperature calcination. Comprehensive analyses using X-ray powder diffraction (XRD), electron paramagnetic resonance (EPR), and X-ray photoelectron spectroscopy (XPS) conclusively demonstrated the successful preparation of oxygen-deficient LATPs under different calcination temperatures in an argon-hydrogen mixed atmosphere. These varying temperatures affected the concentration of oxygen defects in LATP. The hydrothermal precursor was calcined at 700 °C for 6 h to prepare an oxygen-deficient LATP, which was subsequently combined with polyacrylonitrile (PAN) to form a solid composite electrolyte. The composite exhibited a total ionic conductivity of 7.55 × 10−4 S cm−1 at 20 °C. Furthermore, when tested at 25 °C with a current density of 0.025 mA cm−2, the composite displayed good compatibility with a lithium metal anode. At a current density of 0.1 C, the initial discharge capacity was found to be 256.2 mA h g−1, which was maintained at 231.8 mA h g−1 after 100 cycles within the voltage range of 2.0–4.5 V. By judiciously modulating the oxygen defects concentration, it is possible to not only improve the ionic conductivity of the solid composite electrolyte but also to further enhance its discharge capacity. [ABSTRACT FROM AUTHOR]

• LiTiOPO 4 /CeO 2 was synthesized by hydrothermal and solid phase method. • The different valence states of Ce3+/Ce4+ exist in LiTiOPO 4 /CeO 2. • The Ce3+-doped and CeO 2 modified LiTiOPO 4 enhance Lithium-Ion storage. LiTiOPO 4 /CeO 2 composites as high-performance anodes for lithium-ion batteries (LIBs) were synthesized by a simple hydrothermal and high-temperature solid-phase method. X-ray diffraction (XRD) analysis results showed that CeO 2 -motified LiTiOPO 4 was successfully prepared. Electron microscopy observation of the structural and morphological analysis data of the prepared materials further showed that CeO 2 was coated on the surface of LiTiOPO 4. X-ray photoelectron spectroscopy (XPS) showed different valence states of Ce4+/Ce3+ exist in LiTiOPO 4 /CeO 2. The Ce3+-doped LiTiOPO 4 with CeO 2 surface modification was used to enhance lithium-ion storage performance by mediating voltage from 0.01 to 3.0 V. The rate capacity of the LiTiOPO 4 /CeO 2 was maintained at 295.5 mAh g−1. The specific discharge capacity was maintained at 206.5 mAh g−1 after 1000 cycles, at 5 A g−1. The CeO 2 not only significantly enhances ion diffusion and charge transfer, but also reduces polarization, promotes transport of Li+ to more storage sites in LiTiOPO 4. [ABSTRACT FROM AUTHOR]