| The LiTi2(PO4)3(LTP)solid electrolyte has attracted significant attention because it has the advantages of high safety,low cost and strong chemical stability compared with the traditional liquid electrolyte.However,there are still some problems for the commercial applications of LiTi2(PO4)3 oxide solid electrolyte,such as lithium deficiency in the preparation process,low density.In this work,the electrochemical performance of solid electrolyte was improved by elemental doping,optimization of heat treatment process and exploration of optimal lithium content.The main research contents and results are as follows:(1)The LTP solid electrolyte was modified by aluminum doping to synthesize Li1-xAlxTi2-x(PO4)3(x=0、0.1、0.2、0.3、0.4、0.5)solid electrolyte.The effect of aluminum doping on the performance of LTP solid electrolyte was studied.The Li1.3Al0.3Ti1.7(PO4)3(LATP)with Al3+ content x=0.3 has the best performance,and the ionic conductivity was 3.69x10-5 S/cm.The intermal structure of the material and the size of the ion transport channel were effectively improved.(2)The crystallization temperature and the pre-synthesis temperature in the heat treatment process of the LATP solid electrolyte were optimized.When the crystallization temperature was 800℃,a good degree of densification was obtained;the ionic conductiv ity was 6.01 x 10-5 S/cm,which was an increase of 62.87%in comparison to the value at 900℃.When the pre-synthesis temperature was 420℃,the crystallinity was improved,and the ionic conductivity was 1.01×10-4 S/cm,which was an increase of 68.05%compared to the value at 350℃.(3)The effect of Li content on LATP solid electrolyte was studied.The solid electrolyte of LiyAl0.3Ti1.7(PO4)3(y=1.05、1.15、1.25、1.35、1.45、1.55、1.65)was synthesized.When the Li content y=1.45,the sample has the best performance,and the ion conductivity was 2.01×10-4 S/cm,which was an increase of 99.01%compared to the highest ion conductivity obtained in the previous work.It showed that the proper excess of lithium can compensate the volatilization of lithium at high temperature to some extent and promote the crystallization of the sample,thereby the properties of the material were improved.(4)The solid electrolyte obtained in the study was verified to have good electrochemical properties.The Li1.45Al0.3Ti1.7(PO4)3/NCM cathode material was synthesized.The cycling performance and rate capability of the sample after doping were improved.When Li1.45Al0.3Ti1.7(PO4)3 content was 10wt%,the cathode exhibits the best electrochemical performance:the initial specific discharge capacity was 166.96mAh/g at 1C rate;capacity was 151.95mAh/g after 50cycles,which increased 14.43%compared to the pristine powder.The capacity was 88.52mAh/g after 10 cycles at 5C,which increased 63.93%compared to the pristine powder.It showed that the Li1.45Al0.3Ti1.7(PO4)3 protected the cathode from side reactions,simultaneously improving the lithium ion diffusion coefficient to get an improved performance of lithium ion battery. |
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