| The solid electrolyte is one of the important components in the all-solid-state lithium-ion battery.Its use helps to improve the safety,energy density and power density of the lithium battery and broadens the operating temperature range and application field for the battery.NASICON lithium fast ionic conductor has a high lithium ion conductivity as well as a wide electrochemical window and most of them are stable in air,thus,it is a promising solid electrolyte material.In this paper,the solid electrolyte of LiHf2?PO4?3 was synthesized by high temperature solid-state reaction.All of the samples had rhombohedral phase structure after the partial substitution of Hf4+by different valence cations.The doping ions did not change the lattice structure of the matrix,but providing conditions for the migration of ions through defects and lattice distortions.The main effects of the ionic conductivity of the doped ionic ceramic electrolyte are:?1?Substitution of lower valence ions with larger radius could enlarge lattice volume and provide a sufficiently wide migration channel for lithium ions.At the same time,it will bring extra lithium ions into the crystal lattice to compensate the charge and increase the conductivity;?2?If the doping ions and the main ion have a large difference on their radius,the elastic repulsive force will generate between the ions,driving the doped ions out of the crystal lattice and forming into oxides,which was separated into grain boundaries as well as affecting ion conduction and lowering the electrical conductivity.When Al3+doping was 0.2%,the ionic conductivity of the Li1.2Al0.2Hf1.8?PO4?3 was 6.84×10-5S?cm-1 at room temperature.And during the synthesis of Li1.2Al0.2Hf1.8?PO4?3,excess 30%LiNO3 was added to the raw materials to compensate for the volatilization of lithium during the high-temperature sintering process,suppress the formation of hetero phases and increase the electrical conductivity.Spark plasma sintering?SPS?can obtain Li1.2Al0.2Hf1.8?PO4?3 electrolyte with 94%density in a short time?10min?,and its ion conductivity can reach 9.07×10-5S?cm-1 at the room temperature.A sol-gel method was used to replace Zr4+in LiZr2?PO4?3 with Y3+or Mg2+to obtain a rhombohedral phase structure that was stable at room temperature.When compared with the pressureless sintering,the density of Li1.1Y0.1Zr1.9?PO4?3 through the hot press sintering was increased from 76%to 94%and the electrical conductivity was 8.82×10-5S?cm-1.Lithium dendrites growth and chemical shuttle are destructive issues that obstruct the deployment of all-solid-state batteries as well as hybrid Li–redox–flow cells.In this work,a new solid NASICON Li1.2Mg0.1Zr1.9?PO4?3?LMZP for short?oxide,which has a high relative density of 2.95g?cm-3 and an improved room-temperature Li-ion conductivity of 4.2×10-5S?cm-1,was prepared to prevent lithium-dendrite formation and growth in an all-solid-state Li-ion battery and polysulfide-anion diffusion in a Li-S battery.The symmetric Li/LMZP/Li cell with a long cycle life exhibits a small Li-ion resistance for Li-ion transfer across the Li/LMZP interface.Both an all-solid-state Li-LiFePO4 and hybrid Li-S batteries with a LMZP pellet as a solid electrolyte have a superior cycling stability and a high coulombic efficiency,which is caused by a stable solid electrolyte interphase. |
PDF Full Text Request