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Lithium iron phosphate (LiFePO 4) has been extensively investigated as a cathode material for next generation lithium ion batteries, but it faces inherent low electronic conductivity and slow Li+ diffusion rate. This leads to poor electrochemical performance at high C-rates and at high temperatures. To solve this, we coat optimally thick, conductive, and conformal TiN films on LiFePO 4 particles using atomic layer deposition. The 10 cycles of TiN (10TiN) coated sample delivers an initial capacity of ∼78.8 mAhg−1 at a high rate of 5 C-rate and at a high temperature of 55 °C, while an uncoated sample delivers only ∼ 62.8 mAhg−1 under the same condition. The high electrode density due to ALD thin film coating, optimized pressing, and protective nature of the ultrathin film and increase in conductivity are contributing factors to the improved the high rate performance of the coated samples as compared to the pristine sample at elevated temperature. • ALD TiN coating improved the high rate capability of LiFePO 4 at high temperature. • The enhanced behavior is closely related to an increase of electrode density. • Also, it could be caused from an improvement of ionic and electronic conductivity. [ABSTRACT FROM AUTHOR]

Herein, the spinel-layered cathode material Li1.33MnTiO4+z (0.8LiMnTiO4•0.2Li2Mn0.5Ti0.5O3) is investigated for the purpose of developing a high-capacity, low-cost, and environmentally friendly cathode for Li-ion batteries. Sol-gel synthesis is conducted and the relationships between synthesis temperature, structure, and electrochemical performance of the cathodes are studied. The effects of size and purity on the capacities of these cathodes are discussed. The samples fired at 500 and 600 °C contain an impurity phase of TiO2, thus delivering capacities of 208 and 210 mAh g−1 at C/10, respectively. The sample fired at 700 °C without the impurity phase of TiO2 shows a high capacity of 222 mAh g−1 at C/10 and capacity retention of 90.5% after 100 cycles at 1C. [ABSTRACT FROM AUTHOR]

Flower-like Li1.2Ni0.17Co0.17Mn0.5O2 microstructures were prepared by a simple one step low-temperature electrospinning method. The morphological changes occurred with temperature increase from 500°C to 700°C. Scanning electron microscopy showed that flower-like Li1.2Ni0.17Co0.17Mn0.5O2 after heat treatment at 600°C was composed of nanoplates with an open porous structure. Flower-like electrode with well-organized porous structure can be attributed to the favorable shape to facilitate the diffusion of lithium ions. Flower-like Li1.2Ni0.17Co0.17Mn0.5O2 microstructures showed a high discharge capacity of 235mAhg−1 during the first cycle compared to other electrode materials. [ABSTRACT FROM AUTHOR]

Integrated spinel-layered cathode materials are much appeal for use in high-energy-density Li-ion batteries. Here, we introduce a one-step hydrothermal reaction to synthesize high-capacity cathode materials (>300 mAh g−1) based on Li–Mn–O systems. The synthesis temperature governs the phase components and cation disorder. The sample with a low synthesis temperature (150 °C) shows the highest capacity (320 mA h g−1, 2–4.8 V) but the capacity decreases intensely to 62% after 50 cycles. The sample with the higher synthesis temperature (200 °C) shows better cycling stability with 85% capacity retention after 50 cycles. This study elucidates the roles of cation disorder as well as the spinel phase on the high-capacity cathode and provides an understanding of their electrochemical behaviors. • Introduction of high-capacity spinel-layered cathode materials. • Elucidating roles of the spinel phase and cation disorder in high-capacity cathodes. • The cycle stability depends on the synthesis temperature and phase component. [ABSTRACT FROM AUTHOR]

• Introduction of F-doped layered-spinel Li 1.2 Mn 0.75 Ni 0.25 O 2-z F z cathode materials. • F doping has confilicting roles on electrochemical performance of cathode materials. • The cycle stability depends on the F doping content. Herein, the conflicting roles of F doping on the electrochemical performance of layered-spinel Li 1.2 Mn 0.75 Ni 0.25 O 2- z F z (z = 0, 0.05, 0.1) cathode materials are studied. The compound consists of Li 1.2 Mn 0.6 Ni 0.2 O 2 and LiMn 1.5 Ni 0.5 O 4 with their phase ratio depending on F doping content. When z = 0.05, it favors the spinel phase formation, leading to increased first Coulombic efficiency and improved cycle stability. However, it reduces the cathode capacity to 250 mAh g−1 at C/10 (the capacity of the pristine is 280 mAhg−1). With F doping content increasing to z = 0.1, the cycle stability of the cathode is the best, with 96 % capacity retention after 200 cycles at C/2. The high level of F stabilizes the structure, prevents phase transition, and retards voltage decay. The result demonstrates a promising strategy for the design of composite cathode materials by F doping. [ABSTRACT FROM AUTHOR]

The recently developed composite cathode can solve the disadvantages of single-component Lithium-ion batteries such as low capacity, low rate performance, and poor cycling stability. Spinel-layered Li 1.5 MnTiO 4+ δ composites synthesized by a solid-state reaction showed high capacity and excellent cycling stability at room temperature. However, this material showed very poor cycling stability at 50 °C. A novel approach was used to synthesize spinel@layered composites, with the thermally stable layered component located in the outer part, and the high-capacity spinel located in the inner part of the composite particles. The effects of annealing temperature on electrochemical performance of cathodes were studied at both room temperature and 50 °C. The optimized sample, which was annealed at 700 °C, showed excellent thermal stability at 50 °C with 92% capacity retention after 100 cycles at 1C, compared to the value of 87% shown by the solid-state sample. At room temperature, the optimized cathode exhibited enhanced capacities of 209 and 157 mAh g −1 at C/5 and 1C, respectively. Moreover, the optimized sample showed improved performance at different C-rates compare to the solid-state sample. [ABSTRACT FROM AUTHOR]

O3-type Na[Ni 1/3 Fe 1/3 Mn 1/3 O 2 (NaNFM) is considered as a promising cathode material for sodium-ion batteries; however, its poor cycling stability is still a concern. In this study, we discuss the structural, surface and electrochemical properties of Mg-doped NaMg x [Ni 1/3 Fe 1/3 Mn 1/3 1– x O 2 materials and their enhanced cycling performance. The variations of the lattice parameters by substitution of Mg ion and its uniform distribution on the particles are confirmed using X-ray diffraction and transmission electron microscopy. The optimized NaMg 0.05 [Ni 1/3 Fe 1/3 Mn 1/3 0.95 O 2 delivers a discharge capacity of ~120 mAh g−1 and has a diffusion coefficient of Na ranging from 6.5 × 10−13 to 2.7 × 10−10 cm2 s−1. In particular, it shows a relatively high discharge capacity of 42 mAh g−1 even at a high current density of 1200 mA g−1 and exhibits considerably enhanced cycling stability (77% capacity retention after 50 cycles), compared with that of the undoped NaNFM (40%). Based on structural and electrochemical analyses, it is suggested that Mg doping can effectively suppress the irreversible structural degradation and induce more reversible phase transitions; this results in a more stable cycling performance of the Mg-doped NaNFM than that of undoped NaNFM. Image 1 • Mg doping onto O3-type Na[Ni 1/3 Fe 1/3 Mn 1/3 O 2 for sodium-ion batteries. • Uniform distribution of Mg on the surface and bulk of the doped cathode particle. • Mg doping suppress the irreversible structural degradation. • The composition modification results in improved rate-capability and cyclability. [ABSTRACT FROM AUTHOR]

In this study, we propose composite materials based on the Li–Mn–Ti–O system to develop low cost and environmentally benign cathode materials for Li-ion batteries. Specifically, spinel-layered Li 2 MnTiO 4+z (0.5LiMnTiO 4 •0.5Li 2 Mn 0·5 Ti 0·5 O 3) material is studied with the aim to increase the operating voltage of the cathode. In contrast, to increase the capacity as well as rate capability of the cathode, an electrospinning technique is employed to synthesize uniform nanofibers with diameters of approximately 80 nm and a length of 15 μm. The hetero- and one-dimensional structure of the prepared sample facilitate Li+ transport by shortening the diffusion length for the ions. Consequently, high capacities of 210 (average operating voltage ~3.1 V) and 150 mAh g−1 at C/10 and 1C rates, respectively, are obtained. Image 100734 • Introduction of ultralong spinel-layered Li 2 MnTiO 4+ z nanofibers with diameters of about 80 nm and length of 15 µm. • Elucidating relationship between structure and electrochemical properties of the nanofibers. • A high reversible capacity of 210 mAh g-1 at C/10 and 95.3 % capacity retention after 100 cycles at 1C are obtained. [ABSTRACT FROM AUTHOR]

Hole-embedded one-directional two-dimensional sheet-assembly cobalt oxide microspheres are synthesized and assessed as effective encapsulation media for polysulfides in cathodes of lithium–sulfur batteries. The cathode of fishing-net-shaped cobalt oxide compounds incorporated with sulfur provides exceptional electrochemical properties such as a high Coulombic efficiency (99%), stable capacity fading, and a reversible capacity of 925 mA h g−1 at 1 C, which is 22% higher than that of the conventional nanoparticulate cobalt oxide/sulfur electrode. The enhanced electrochemical behavior is attributed to the effective polysulfide adsorbent and hierarchically designed porous cobalt oxide with a coaggregated framework. The controlled pore-embedded particle size is an essential parameter determining the capture of the mobile polysulfides, rather than the use of numerous mere highly porous encapsulants, such as nanoparticulate cobalt oxides. Image 1 • Optimum pore and morphology controlled spherical Co 3 O 4 for polysulfide reservoir. • Stable capacity retention for the given Co 3 O 4 microsphere incorporated S cathode. • Propose conceptual design of cobaltoxide compounds for the novel electrode material [ABSTRACT FROM AUTHOR]