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Li1+xAlxTi2−x(PO4)3(LATP) is a promising solid electrolyte owing to its high stability and ionic conductivity. But the ionic conductivity of LATP prepared by a conventional solid-phase method is usually one order of magnitude lower than the one prepared by the liquid-phase method. Herein, we achieve a high ionic conductivity of 1.2 mS·cm−1by doping B3+and Y3+ions in LATP in a solid-state synthesis, and the roles of the dopants are revealed. The incorporation of B3+and Y3+in the lattice broadens the ion migration path and mitigates the Li+migration energy barrier. On the other hand, the strong electrostatic interaction between B–O and Y–O bond weakens the electrostatic attraction between the Li–O bond, which makes the Li–O bond easier to break, and greatly improves the ion conductivity of LATP. This study sheds light on the facile solid-state synthesis of LATP with a high ion conductivity and accelerates the incoming practical application in the solid-state battery.

P2-type layered transitional metal oxides as the promising cathode materials for sodium-ion batteries (SIBs) have attracted great attention. But their poor cycling stability and inferior rate capability restrict the practical applications. Foreign elements doping has been considered as one effective strategy to overcome these shortcomings. But the roles of the dopants are still poorly understood. Herein, we have taken La doping to modulate the crystal and electronic structure, and systematically investigated the different effects of La substitution for Mn, Ni and Co on the structure and electrochemical properties of P2-Na0.67Mn0.6Ni0.2Co0.2O2cathode materials. The substitution of La reduces Mn3+in the crystal lattice which alleviates Jahn?Teller distortion and reduces the collapse of the transition metal layer caused by the dissolution of Mn3+. Due to the large La-O bonding energy, the substitution of La for Mn, Ni and Co shortens O-O and TM-O bond length, and the thickness of TMO2, which all enhance the structure stability. In addition, the substitution of La for Mn, Ni and Co also expands the interlayer spacing and Na-O bond length enhancing Na+diffusion kinetics. The substitution of La for Mn shows better rate capability and cycling stability than the substitution for Ni and Co. It can provide a discharge capacity of 86 mAh g?1at a high current density of 8C (1600 mA g?1) with a capacity retention rate of 95%. This study also presents some insights into modulating the lattice and electronic structure by elements doping to optimize the electrochemical performances.

Li+/Ni2+disorder as an intrinsic structure defect in Ni-based layered oxides cathodes for lithium-ion batteries plays a crucial role on the overall electrochemical performances. However, the nature of Li+/Ni2+disorder on the structure and property is still poorly understood. Herein, we design and synthesize layered LiNi1/3Co1/3Mn1/3O2cathode materials with a different Li+/Ni2+mixing degree, and focus on unveiling the influence mechanism of Li+/Ni2+disorder on the surface/bulk structural evolution and the charge compensation mechanism by neutron, synchrotron radiation and electrochemical impedance techniques. High Li+/Ni2+disorder increases the side reactions between electrolyte and electrode surface and aggravates the variation of local environment of Mn cations with (de)lithiating, which is largely responsible for the degradation of the initial capacity, rate capability and cycling performance. Interestingly, Li+/Ni2+disorder can also relieve the electrostatic interaction between the cationic and anionic ions by enlarging the LiO6octahedron and TMO6octahedron, and locks the surrounding oxygen slabs by forming strong covalent bonds between antisite Ni and coordinated O ions, which alleviates the variations of the lattice parameters during charging/discharging. This study presents some new insights into designing high performance layered oxide cathodes through regulating Li+/Ni2+disorder.

Lithium-rich manganese-based layered oxides (LLOs) cathodes attract great attention due to their high specific capacity. But the low rate capability, inferior cycling stability, voltage decay and the poor low-temperature performances hinder their application. Herein, we propose a synergistic strategy of Zr doping and Li2TiO3coating to mitigate the drawbacks of Li1.2Ni0.2Mn0.6O2, and the cooperative modification mechanism is unraveled. In addition to the pre-doping of Zr in the precursor, a little fraction of Ti is also doped in the host during the coating process. This combines the advantages of Zr/Ti dual doping and Li+-conductor Li2TiO3coating, which cooperatively enhances the rate capability, cycling stability and the poor low-temperature performances as well as mitigate the voltage decay. Neutron diffraction analysis indicates that the interslab spacing and the bond length of O-O and TM-O are enlarged which lowers the Li+diffusion energy barrier and the repulsive interaction between Li-ions and TM cations, and facilitate Li+diffusion and rate capability. The Li+/Ni2+intermixing is also mitigated which further enhances Li+diffusion and the layered structure stability. Furthermore, the tightly bound Li+-conducting Li2TiO3layer not only avoids the electrode side reaction but also enhances the Li+diffusivity.