Search

Polyanionic cathode materials are increasingly used in research because of their good cycling performance, high theoretical capacity, and high operating voltage. However, it exhibits poor performance due to its structure, which prevents it from reaching its full theoretical capacity. In this study, carbon‐coated Li6V3(PO4)5@C cathode materials are constructed under Li3V2(PO4)3 research conditions using the sol–gel process and anhydrous citric acid as the carbon source. Several boron doping concentrations are investigated to create Li6V3(PO4)5@BC cathode materials. The electrochemical measurements demonstrate that during the first cycle, at a current density of 0.5 C and a B doping quantity of 2 wt%, the specific discharge capacity of Li6V3(PO4)5@BC reaches 167.43 mAh g−1. The steady discharge specific capacity following 80 cycles of constant‐current charging and discharging is 136.84 mAh g−1. Li6V3(PO4)5@BC‐2 has a specific discharge capacity of 131.1 mAh g−1 at 2 C. The material's electrochemical performance greatly improves following the right quantity of B doping, which is primarily attributed to the increase in carbon layer defects brought on by B's entrance. This can increase the rate of lithium‐ion migration and hold more lithium ions. [ABSTRACT FROM AUTHOR]

Sodium‐ion batteries (SIBs) work similarly to lithium‐ion batteries, but they cost less and are safer. However, the battery has some shortcomings, such as low energy density and poor stability, which hinder its development and application. The development of electrode materials with low cost and high‐performance characteristics is a hot and difficult point in the research of SIBs. In this paper, the existing sodium ion cathode and anode materials are systematically reviewed. Firstly, the electrochemical structures and properties of various cathode and anode materials were introduced, and the limitations of cathode and anode materials of SIBs were analyzed. Based this, the current modification methods were summarized, such as surface coating of materials, doping of heteroatoms and metal elements to improve the electrochemical performance. In this paper, the research progress and modification measures of SIBs are summarized and prospected. It is helpful to further improve its comprehensive performance and lay a foundation for the future application of cathode and anode materials for SIBs. [ABSTRACT FROM AUTHOR]

A facile and highly efficient method was proposed for the separation and regeneration of LiFePO4 (LFP) cathode materials from spent lithium‐ion batteries (LIBs). The optimal separation conditions involved immersing the spent LFP materials in NaOH (0.5 mol/L) solutions at a temperature of 90 °C, with a solid‐liquid ratio of 30 g/L under stirring of 500 rpm. The high separation effect can be attributed to the synergistic action of several factors at the interface. Furthermore, the structure, composition, morphology, and electrochemical performance of the regenerated LFP (D‐LFP) materials at different temperatures were systematically investigated. Notably, the D‐LFP material generated through calcination at 650 °C for 10 h exhibited a initial discharge capacity of 154.4 mAh g−1 at 0.5 C and the capacity retention rate of 97.3 % after 100 cycles. Moreover, a detailed investigation of the kinetics of the separation and regeneration processes was carried out, along with an exploration of the underlying electrochemical mechanism. This idea not only mitigates the harmful impact of waste on both human health and the environment but also realizes the transformation of waste into valuable resource treasure, promoting a greener and more sustainable development of society. [ABSTRACT FROM AUTHOR]

Heterostructure NaMnO2–Li0.5Mn2O4 cathode materials were prepared by adjusting the molar ratio of sodium in the materials by a solid phase method. X-ray diffraction (XRD) analysis showed that the prepared samples were a layered-spinel heterostructure NaMnO2–Li0.5Mn2O4. The lattice fingerprint region of NaMnO2–Li0.5Mn2O4 was studied by electron microscopy, and the results showed the (111) plane of Li0.5Mn2O4 and the (001) plane of NaMnO2. The heterostructure 0.5NaMnO2–0.5Li0.5Mn2O4 exhibits superior high-rate capability and excellent cycling performance. The proposed heterostructure 0.5NaMnO2–0.5Li0.5Mn2O4 cathode is investigated by in situ XRD and impedance analysis. The rate of discharge of heterostructure 0.5NaMnO2–0.5Li0.5Mn2O4 was 108.8 mA h g−1 at 500 mA g−1. The initial discharge of 0.5NaMnO2–0.5Li0.5Mn2O4 was 61.69 mA h g−1, and after 1000 cycles the discharge capacity remained 51.13 mA h g−1 at a current of 2 A g−1. The heterogeneous structure combines the advantages of high capacity of the layered structure NaMnO2 and the structural stability of the spinel Li0.5Mn2O4, which exert a synergistic effect and improve the electrochemical performance of the lithium-free layered NaMnO2 cathode material. [ABSTRACT FROM AUTHOR]

In this investigation, a lithium-free cathode material, Na0.7MnO2.05–Na0.91MnO2, was synthesized by the solid phase method. The intercalation mechanism and partial phase transformation mechanism of NMO600 were clarified by in situ X-ray diffraction and impedance. The design of the heterostructure is favourable for improving the lithium ion storage of NMO600, which can deliver a discharge capacity of 83.12 mA h g−1 at 1 A g−1 and keep 61.71 mA h g−1 after 700 cycles. [ABSTRACT FROM AUTHOR]

Herein, a facile method with high efficiency is proposed for the separation and regeneration of LiMn2O4 (LMO) cathode material for spent lithium‐ion batteries through a simple heat treatment method. At first, the aluminum foil is separated at 450 °C in air, with a separation efficiency as high as 97.95%. Then, separation LMO is regenerated with high crystallinity at 650 °C with an optimum calcination time of 6 h. Importantly, this method allows D‐LMO to exhibit high reversible capacity (133 mAh g−1 at 0.1C), high rate performance (101 mAh g−1 at 5C), and long lifespan (0.5C, 92.1% capacity retention ratio after 100 cycles). A positive effect of the pyrolysis of polyvinylidene fluoride on D‐LMO is also suggested by the results. Moreover, a detailed investigation of the kinetics of the separation and regeneration is done, and the electrochemical mechanism is explored. Furthermore, this method requires much less energy input and chemical consumption, which would be helpful for environmental protection and green recycling. [ABSTRACT FROM AUTHOR]

• The composite solid-state electrolytes were formed by NATP and PAN. • The ionic conductivity of Na 1.3 Al 0.3 Ti 1.7 (PO 4) 3 -PAN was 4.51 × 10−4 S/cm at 20 °C. • Al3+ doping NTP enlarged the electrochemical window to 5.2 V. • Na 1.3 Al 0.3 Ti 1.7 (PO 4) 3 -PAN exhibited excellent electrochemical performance. In this study, Na 1+x Al x Ti 2-x (PO 4) 3 (NATP) with oxygen vacancies was synthesized using a high-temperature solid-phase method. Then, NATP and polyacrylonitrile (PAN) were combined to form NATP-PAN composite solid-state electrolytes. X-ray powder diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) analyses demonstrated the presence of oxygen defects in NATP. Al3+ doping created oxygen vacancies in NATP, which decreased the activation energy for Li+ ions transport; this increased the mobility of Li+ ions in the material, broadening the electrochemical window of the electrolyte. The Na 1.3 Al 0.3 Ti 1.7 (PO 4) 3 -PAN solid-state electrolytes achieved an excellent ionic conductivity of 4.51 × 10−4 S cm−1 at 20 °C and a wide electrochemical stability window of 5.2 V (vs. Li+/Li). Na 1.3 Al 0.3 Ti 1.7 (PO 4) 3 -PAN composite electrolyte was used to assemble a Li||Li symmetric half-cell, which exhibited good interface stability and an overpotential of approximately ±60 mV at a current density of 0.25 mA cm−2. Furthermore, Li׀Na 1.3 Al 0.3 Ti 1.7 (PO 4) 3 -PAN׀LiFePO 4 was assembled into an all-solid-state lithium metal battery, which exhibited excellent electrochemical performance, with the initial discharge capacity of 255.0 mA h g−1 at 0.1 C. After 100 cycles, the discharge capacity was maintained at 229.6 mA h g−1, and the capacity retention rate was 90.0 %. Increasing dopant concentration, the oxygen defect concentration is increasing, which plays a crucial role in the ionic conductivity as well as the interface stability. The Na 1.3 Al 0.3 Ti 1.7 (PO 4) 3 -PAN solid-state electrolytes achieved an excellent ionic conductivity of 4.51 × 10−4 S cm−1 at 20 °C and a wide electrochemical stability window of 5.2 V (vs. Li+/Li). Increasing dopant concentration, the oxygen defect concentration is increasing, which plays a crucial role in the ionic conductivity as well as the interface stability. [Display omitted] [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 TiP2O7‐y is synthesized by solvothermal and high‐temperature solid‐phase methods. X‐ray powder diffraction (XRD) test data analyses reveal that the solvothermal reaction time can affect the density of oxygen defects in the TiP2O7‐y. Fourier transform infrared spectra (FT‐IR) shows that there is a blue shift in the P−O bond because of the presence of oxygen vacancies. It is strongly demonstrated that oxygen vacancies exist in TiP2O7‐y because electron paramagnetic resonance (EPR) shows sharp peaks at g=2.003. Oxygen vacancy modulated TiP2O7‐y with exposed (541) face shows long cycling stability and super high‐rate capabilities. The initial discharge capacity of TiP2O7‐y, which was prepared after solvothermal reaction for 18 h, reached 828.4 mAh g−1. It can still maintain 246.9 mAh g−1, at 0.5 A g−1, after 500 cycles. Even cycled at 5 A g−1, the reversible rate capacity was maintained at 209.7 mAh g−1. Oxygen vacancies can not only improve the electronic conductivity of TiP2O7‐y but also increase the lithium‐ion diffusion rate. [ABSTRACT FROM AUTHOR]

Nanoparticle Na3V2(PO4)3/C materials with different polyacrylonitrile contents can be successfully synthesized using precipitation method. As an energy storage material used in the production of lithium batteries which is also compared with pure of that, the Na3V2(PO4)3/C not only has a larger capacity, but also has a very high cycle stability. In particular, the initial discharge capacities of the Na3V2(PO4)3/C sample annealed at 750°C containing 10 wt% of polyacrylonitrile are 130.9 and 122.2 mAh g−1 at current densities of 0.5 and 1 C, respectively; the corresponding coulomb efficiencies are 97.3 and 99.5%. It is also worth noting that the capacity retention can reach as high as 92.7% for 500 cycles at 1 C. [ABSTRACT FROM AUTHOR]

Summary: Herein, a series of lithium‐sodium hybrid ion Na3−xLixV2(PO4)3/C (x = 2.5, 2.0, 1.5, 1.0, 0.5) as cathode materials are prepared by sol‐gel method. The lithium storage properties of Na3−xLixV2(PO4)3/C reveal that the lithium sodium ratio has a strong influence on material structure and the electrochemical properties. The multiple voltage platforms are observed at charge and discharge curve for the Na0.5Li2.5V2(PO4)3 material, as it contains rhombohedral and monoclinic Li3V2(PO4)3 phases, whereas a single voltage platform can be observed when x is less than 2, which are mixtures of Na3V2(PO4)3 with rhombohedral structure and Li3V2(PO4)3 with rhombohedral structure. Notably, NaLi2V2(PO4)3/C prepared by the calcination at 700°C for 8 hours contains a single rhombohedral phase. And when the charging and discharging voltage at the range 2.5 to 4.5 V and current density at 0.5C, NaLi2V2(PO4)3/C and Na2.5Li0.5V2(PO4)3/C are prepared by the pre‐calcination at 400°C for 4 hours and subsequent calcination at 750°C for 8 hours exhibit high first‐cycle specific discharge capacities of 124.8 and 130.0 mAh·g−1. The capacities are 118.4 and 115.1 mAh·g−1 after 50 cycles, indicating excellent capacity retention. [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]

Lithium-ion batteries (LIBs) present the advantages of long cycle life, high voltage, and energy density and are widely made in the field of energy storage. LiVOPO 4 (LVOP), a cathode material used in LIBs, has a high conceptual capacity of 159 mAh g−1 and high operating voltage of 3.9 V. However, its low electrical conductivity and cycle performance limit its commercial applications. According to the X-ray diffraction results, orthogonal crystal LVOP and monoclinic crystal Li 3 V 2 (PO 4) 3 (LVP) coexisted in the synthesised composite material. The transmission electron microscopy results also indicated that the LVOP and LVP phases coexist, which were coated by carbon layer of about 2.5 nm. The discharge of LVOP–LVP composite material initially was 143.2 mAh g−1, and that after 120 cycles was 132.2 mAh g−1 (at 0.1 C and 3–4.5 V). Thus, the electronic conductivity and first discharge specific capacity of the material enhanced due to the introduction of fast ion conductor LVP into LVOP. Electrochemical performance improved because the introduction of LVP led to an increase in Li+ pervasion channels in the original material and the acceleration of the Li+ transmission speed. [ABSTRACT FROM AUTHOR]

Abstract Herein, the hexagonal NaTi 2 (PO 4) 3 /C was successfully synthesized by mechanical ball-milling using citric acid as the carbon source and characterized the structure and morphology of as-obtained samples, revealing that their surface was covered with a thin carbon layer. Charge/discharge testing revealed that the NaTi 2 (PO 4) 3 /C sample with a carbon content of 4.4 wt% (prepared at 800 °C at a citric acid loading of 10 wt%) exhibited the highest initial discharge capacity of 869.5 mAh/g and featured excellent cycling stability. Thus, mechanical ball-milling coupled with carbon coating enabled the facile and practical preparation of NaTi 2 (PO 4) 3 /C with enhanced electrochemical properties. [ABSTRACT FROM AUTHOR]

Triclinic α-LiVOPO 4 with excellent electrochemical properties is prepared, using δ-VOPO 4 , LiNO 3, and a highly conductive carbon material (acetylene black) as raw materials, by a two-step method, for the first time. Transmission electron microscopy reveals that the synthesized nanoscale α-LiVOPO 4 is approximately 50–100 nm in size, and its surface is covered by 1.68 nm thick acetylene black, which not only improves the ionic conductivity of the material, but prevents material-size growth at high temperature, and particle agglomeration. In addition, the initial discharge capacity of α-LiVOPO 4 sintered at 600 °C over 10 h is the highest, reaching 111.7 mAh g −1 at 0.05 °C. The capacity retention rate is 95.1%, which is 106.3 mAh g −1 after 50 cycles. [ABSTRACT FROM AUTHOR]

• LiVOPO 4 -Li 2.72 Ti 2 (PO 4) 3 was successfully synthesized by a two-step method. • The LiVOPO 4 -Li 2.72 Ti 2 (PO 4) 3 has a heterogeneous structure. • The lithium superior conductor improves electrochemical performance of the LiVOPO 4. The heterostructure LiVOPO 4 -Li 2.72 Ti 2 (PO 4) 3 (LVOP-LTP) was synthesized using a hydrothermal process combined with a high-temperature solid-phase method. The electron microscopic analysis demonstrates that the sample has a heterojunction. The electrochemical performance tests reveal that the heterostructure LVOP-LTP has initial discharge-specific capacity of 88.4 mAh/g at 100 mA g−1, which is superior to the single-phase LiVOPO 4 (LVOP, 25.1 mAh/g) and Li 2.72 Ti 2 (PO 4) 3 (LTP, 37.1 mAh/g). The improved electrochemical performance of heterostructure LVOP-LTP can be ascribed to the introduction of lithium superionic conductor (LISICON) and the formation of a heterojunction, which increases the lithium-ion pervasion channels and accelerates the lithium-ion transmission speed. [ABSTRACT FROM AUTHOR]

A series of LiFe 1−x Mn x PO 4 /C composites (x=0, 0.1, 0.3, 0.5, 1) are synthesized via an ion exchange method, utilizing LiOH·H 2 O, FeSO 4 ·7H 2 O, MnSO 4 ·H 2 O, Na 3 PO 4 ·12H 2 O, and H 3 PO 4 as the raw materials, citric acid as the carbon source, and reductant, and H 2 O as the solvent. The composites containing Mn have larger lattice parameters compared to pure LiFeMnPO 4 /C, due to the larger ionic size of Mn 2+ compared to Fe 2+ . The composites also consist of spherical nanoparticles with a thicker carbon coating. LiFe 0.9 Mn 0.1 PO 4 /C exhibited the best electrochemical properties as the cathode in lithium-ion batteries, with a discharge capacity close to the theoretical value of LiFePO 4 , better capacity retention rate (98.5% vs. 94.5%) and excellent cycle stability. The improvements were attributed to the Mn-complex. Electrochemical impedance spectra demonstrate that the Mn-composites can improve electronic and ionic conductivity, indicating that introduction of Mn is a viable way to improve the conductivity in olivine-like LiFePO 4 cathode materials, and enhance the battery performance. [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]