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Abstract A nanoscale spinel pillaring layer is introduced onto the surface of the LiNi 0.8 Co 0.1 Mn 0.1 O 2 cathode material, which is confirmed by combined surface-probing techniques. The functional layer does not change the crystal structure after of pristine LiNi 0.8 Co 0.1 Mn 0.1 O 2 , while it plays a vital role in avoiding unfavorable side reactions occurred in the interphase between cathode materials and electrolyte. The treated sample shows suppressed capacity decay (19.3%) as compared to the pristine sample (41.9%) after 200 cycles at 2 C rate. Moreover, it can also improve the storage performance of LiNi 0.8 Co 0.1 Mn 0.1 O 2 by restraining the generation of Li 2 CO 3 and the NiO-like phase during the storage process in humid air. Thus, the capacity retention capability is improved after storage in air for 2 months, which improves from 52.2% to 77.6% after 200 cycles. Overall, this study offers an effective solution to improve the cyclability and storage stability of the Ni-based cathode materials. Highlights • A spinel pillaring layer is introduced onto the surface of the Ni-based materials. • The spinel pillaring layer can alleviate HF erosion, and side reactions between electrode and electrolyte. • The spinel pillaring layer can suppress the reduction of nickel and the generation of Li 2 CO 3. • Both cycle performance and storage property are enhanced. [ABSTRACT FROM AUTHOR]

To improve the stability of LiVPO 4 F electrode/electrolyte interface, Li 3 PO 4 is used to modify LiVPO 4 F composite (P-LVPF) for the first time. Morphological characterization shows that LiVPO 4 F particles are wrapped by amorphous carbon and lithium ionic conductor Li 3 PO 4 as the interlayer and outer layer, respectively. Compared to the pristine sample, the resultant P-LVPF exhibits greatly improved rate capability and elevated-temperature cycle performance when applied as the cathode material for lithium ion batteries. Specifically, the Li 3 PO 4 modified sample specific capacity maintains 77.6% at 1 C after 100 cycles under 55 °C. Such improvement is attributed to the fact that the Li 3 PO 4 coating layer not only acts as a good ionic conductor for LiVPO 4 F, but also serves as a physical barrier between electrode and electrolyte which can build a stable interface. [ABSTRACT FROM AUTHOR]

Highlights: [•] Preparation of LiV1− x Al x PO4F by a soft chemical lithiation process. [•] Comparative studies on effects of aluminum precursors. [•] AlF3 is chosen as Al source, as well as to provide excess F source. [•] Al doping can decrease electrode polarization and electrochemical impedance. [•] AlF3 performs much better than Al2O3 in improving electrochemcial performance. [ABSTRACT FROM AUTHOR]

Abstract: xLi3V2(PO4)3·LiVPO4F/C composite is synthesized by mechanically activated chemical reduction. The value of x is designed to be 2.0 but in fact is 2.7 in the prepared sample because of volatilization of HF or VF3. The as-prepared powders with the average primary size of 0.5–1μm are coated with amorphous carbon layer. Structural analysis of the composite indicates that two phases of monoclinic Li3V2(PO4)3 and triclinic LiVPO4F coexist. The composite as cathode for LIB shows excellent electrochemical performances. In the potential range of 3.0–4.4V, it delivers initial discharge capacity of 139, 137, 131, and 123mAhg−1 at 0.1, 1, 5 and 10 C, respectively. And 97.4% of initial capacity is retained even after 300 cycles at 10 C. The cyclic voltammetry (CV) and AC impedance analysis indicate that the prepared composite separately shows good ionic diffusivity and low resistance. [Copyright &y& Elsevier]

Molybdenum doping is introduced to improve the electrochemical performance of lithium-rich manganese-based cathode material. X-ray diffraction (XRD) results illustrate that the crystallographic parameters a , c and lattice volume V become larger with the increase of Mo content. The scanning electron microscope (SEM) shows that the molybdenum substitution increases the crystallinity of the primary particles. When evaluated as cathode material, the as-prepared Li[Li 0.2 Mn 0.54- x /3 Ni 0.13- x /3 Co 0.13- x /3 Mo x ]O 2 ( x = 0.007) delivers a discharge capacity of 155.5 mA h g −1 at 5 C (1 C = 250 mA g −1 ) and exhibits the capacity retention of 81.8% at 1 C after 200 cycles. The results of cyclic voltammetry (CV) and electronic impedance spectroscopy (EIS) tests reflect that the molybdenum substitution is able to significantly reduce the electrode polarization and lower the charge-transfer resistance. Within appropriate amount of Mo doping, the lithium ion diffusion coefficient of the material can reach to 8.92 × 10 –15 cm 2 s −1 , which is ~ 30 times higher than that of pristine materials (2.65 × 10 –16 cm 2 s −1 ). [ABSTRACT FROM AUTHOR]

To improve the electrochemical performance of LiVPO 4 F at room and elevated temperature focusing on the stability of LiVPO 4 F electrode/electrolyte interface, for the first time, MoS 2 nanosheets are introduced to modify LiVPO 4 F/C composites. The coating of MoS 2 layers on the surface of LiVPO 4 F/C nanoparticles is realized via a solution method followed by low-temperature calcination. Morphological observations present that the MoS 2 sheets are homogeneously wrapped around the LiVPO 4 F/C particles. When employed as cathode materials for lithium ion batteries, the MoS 2 -modified LiVPO 4 F/C composites exhibit superior high-rate capability and greatly improved cycle ability compared to bare one, and the sample coated with 1.75 wt% MoS 2 (2M-LVPF) delivers the best electrochemical performance. In particular, it maintains the capacity retention of 91.7% in 100 cycles at 2.0C and delivers a reversible specific capacity of 112 mAh g −1 at a high rate of 8.0C under room temperature. More importantly, it shows greatly improved cycling stability at elevated temperature (55 °C), maintaining 88.1% of its initial capacity at 0.5C after 50 cycles. The reasons for such improvement lie in the MoS 2 coating layer acting as a physical barrier between electrode and electrolyte, as well as electronic/ionic conducting framework for LiVPO 4 F particles. [ABSTRACT FROM AUTHOR]

The x LiVPO 4 F– y Li 3 V 2 (PO 4 ) 3 composite cathode materials have been synthesized through a soft chemical route with mechanical activation assistance followed by low-temperature calcination. Structural analysis indicates that two phases, i.e. monoclinic Li 3 V 2 (PO 4 ) 3 and triclinic LiVPO 4 F coexist in the composites. With the addition of LVP, the average particle size becomes smaller. The prepared composite materials show good electrochemical performance, and especially a good cyclic performance, the most suitable x / y ratio being 1:5 where the sample can deliver a reversible capacity of 139 mA h g −1 . [ABSTRACT FROM AUTHOR]

Abstract: The degradation of Ni-rich LiNi0.8Co0.15Al0.05O2 cathode material is successfully suppressed via a facile in situ oxidizing-coating method. KMnO4 is used as not only a Mn source but also an oxidant. X-ray diffraction (XRD) and scanning electron microscope (SEM) results demonstrate that the structure and morphology of the KMnO4-pretreated sample are the same as the pristine one. X-ray photoelectron spectroscopy (XPS) confirms that the valence state of Mn is +4 and the Ni3+ ions are partly reduced to Ni2+ when the material is doped with Mn4+. Besides, the Mn4+ ions are proved to distribute uniformly on the surface of the materials particles through energy dispersive spectrometer (EDS) and EDS elemental mapping. And it is confirmed that the concentration of Ni in the outer layer is reduced by the Mn-surface-modification. From the electrochemical characterizations, it is confirmed that the presence of tetravalent Mn at the surface can suppress the capacity fading during charge–discharge cycles, even under elevated temperature and overcharge conditions, and can prevent the material from deterioration during storage in air. [Copyright &y& Elsevier]

Abstract: The cathode material xLi2MnO3·(1−x)LiMn0.5Ni0.4Co0.1O2 was synthesized via a spray drying followed by solid-state calcination. The properties of the layered oxide cathodes for x=0.3, 0.5, 0.7 have been investigated by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), galvanostatic cell cycling, as well as Ac impedance spectroscopy. The results indicate that, when x=0.3, the layered oxide cathode shows the best charge–discharge performances of low current density. Between 2.5 and 4.8V (vs. Li/Li+), the initial discharge capacities of 0.3Li2MnO3·0.7LiMn0.5Ni0.4Co0.1O2 are 238, 229 and 206mAhg−1 at a constant current density of 12.5, 25 and 50mAg−1, respectively. The electrode composition 0.7Li2MnO3·0.3LiMn0.5Ni0.4Co0.1O2 displays the best performance at high charge–discharge rate. The initial discharge capacity of 0.7Li2MnO3·0.3LiMn0.5Ni0.4Co0.1O2 is 135mAhg−1 at 250mAg−1, after 50cycles, the discharge capacities of the layered oxide cathode remains 85%. [Copyright &y& Elsevier]