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Li-rich manganese-based materials are considered to be the mainstream cathode materials for next-generation lithium-ion batteries due to high discharge capacity and low cost, but poor cycle life and high temperature performance limit their development. Herein, LiZr2(PO4)3 (LZPO) is coated on the surface of spherical Li1.2Mn0.54Ni0.13Co0.13O2 (LMNCO) material by a simple wet chemical method. The LZPO layer not only has the function of traditional coating layer to inhibit the occurrence of side reactions between electrolyte and LMNCO surface but also promotes the formation of spinel phase in the layered structure, increases the content of lattice oxygen, and reduces the content of absorbed oxygen. Thus, LZPO coated LMNCO has a more stable layered structure during cycling compared pure LMNCO, which improves effectively its long life and high temperature performance. The capacity loss rate of LZPO coated LMNCO is only 16.2% and 11.9% after 350 cycles at 25 °C and 200 cycles at 50 °C, respectively. Moreover, the capacity retention rate of the full cell composed of LZPO coated LMNCO and graphite is 70.7% after 200 cycles at 1.0 C. The coating layer toward stable surface structure can provide an idea for the modification of cathode materials, especially for Li-rich manganese-based materials. [ABSTRACT FROM AUTHOR]

Abstract NASICON-type LiZr 2 (PO 4) 3 (LZP) has a high bulk ionic conductivity (∼10−4 S cm−1) and a wide electrochemical stability window between 0 and 5.5 V. However, LZP suffers from a problem in which its desirable rhombohedral phase transforms to the triclinic phase (∼10−8 S cm−1) below 50 °C. In this work, we reported a rhombohedral-structured LiZr 2 (PO 4) 3 (α-LZP) at room temperature with a high total Li-ion conductivity (2.8 × 10−6 S cm−1) by a microwave sintering process. Moreover, this approach realized a drastic reduction in the sintering temperature from the typical 1200 °C–900 °C with only a 4 h holding time. Using this approach, we also demonstrated the successful synthesis of Ca-incorporated Li 1.2 Ca 0.1 Zr 1.9 (PO 4) 3 (LCZP) with an ionic conductivity of 1.7 × 10−5 S cm−1. [ABSTRACT FROM AUTHOR]

Abstract: A new complete solid solution of NASICON-type compounds between LiZr2(PO4)3 and La1/3Zr2(PO4)3 was evidenced with the general formula Li1− x La x /3Zr2(PO4)3 (0⩽x⩽1). These phases were synthesized by a complex polymerizable method and structurally characterized from Rietveld treatment of their X-ray and neutron powder diffraction data. This solid solution results from the substitution mechanism Li+→1/3La3++2/3□ leading to an increase of the vacancies number correlated to an increase of the La content. According to this substitution mechanism, the general formula can then be written Li1− x La x /3□2 x /3Zr2(PO4)3 (0⩽x⩽1) in order to underline the correlation between the La content and the vacancies rate. For all the compounds, the structure is clearly related to that of the NASICON family with three crystallographic domains evidenced. For 0⩽x⩽0.5, all the members adopt at high temperature the typical NASICON-type structure (s.g. R3¯c), while at lower temperature, their structure distorts to a triclinic form (s.g. C 1¯), as observed for LiZr2(PO4)3 prepared above 1100°C. Moreover, in this domain, the reversible transition is clearly soft and the transition temperature strongly depends of the x value. For 0.6⩽x⩽0.9, the compounds crystallize in a rhombohedral cell (s.g. R3¯), while for x=1, the phase La1/3Zr2(PO4)3 is obtained (s.g. P3¯, Z=6, a=8.7378(2)Å, c=23.2156(7)Å). This paper is devoted to the structure analysis of the series Li1− x La x /3Zr2(PO4)3 (0⩽x⩽1), from X-ray and neutron powder thermo diffraction and transmission electron microscopy (TEM) studies. [Copyright &y& Elsevier]