Preparation And Modification Of Lithium Vanadium Phosphate For Lithium-ion Battery Cathode Material

It can not meet the requirements of the market for the industrialized lithium-ion battery cathode material in security and price, so the olivine structure is the development direction of cathode material. The lithium vanadium phosphoric material specific capacity is not only high, moreover circulates the stability and the percentage performance is so good that it will be new generation positive electrode material hopefully. Therefore the present research key point is this kind of material. This article has outlined the lithium ion battery positive electrode material research development. this article uses research techniques and so on XRD, SEM, thermo-gravimetric analysis, electrochemistry test and ultimate analysis, chooses from raw material, the synthesis craft, the structure attribute, the appearance analysis, the electrochemistry performance evaluation, the partial element doping modified and so on multi-aspects have conducted the system thorough research to positive electrode material Li3V2(PO4)3 in the analysis new lithium ion battery positive electrode material Li3V2(PO4)3 preparation technological process and in the influencing factor foundationIn this article, it used wet milling carbon thermal sintering to synthesize positive electrode material Li3V2(PO4)3 under the nitrogen protection. we study the influence of the material's performance by comprehensive study of different carbon sources, the same proportion of different carbon sources, different lithium sources, milling time, precursor processing, roasting time on the final product structure and electrical properties. The best synthesis craft route : taking the lithium carbonate, ammonium dihydrogen phosphate, vanadium pentoxide as raw materials, taking electric conduction carbon ECP as the reducible carbon source, excess 110%, wetting 1.5h, 80℃drying 24h, dry grinding 1h, muffling at 300℃furnace pre-4h, and then nitrogen through the tube furnace baking 800℃18h, cooled to room temperature. Prepared under these conditions, lithium vanadium phosphate materials are the first specific capacity of up to 126.3mAh / g, discharge capacity is 123.6 mAh / g, efficiency of 97.3% for the first time. The battery capacity after 1500 cycles can be maintained above 82% , the electric discharge under 10C may maintain the 1C charging capacity above 85%. The circulation voltammetry to the vanadium lithium phosphoric inlaying /escaping of the lithium mechanism's analysis test to indicate that in the 3.0~4.3V scope, Li3V2(PO4)3 will have three pair of oxidation reduction peak: 3.65V/3.51V, 3.74V/3.61V, 4.11V/3.97V. The first two pairs appraise corresponding V4+/V3+ is the first ion corresponding embedding and prolapse, the latter of variable value corresponding V5 + / V4 +, the corresponding points is the second lithium-ion intercalation and prolapse.The titanium, zirconium, aluminum three elements in three doping on the synthesis of lithium vanadium phosphate materials doped to further improve the phosphoric acid vanadium lithium the electrochemistry performance. In the XRD analysis demonstration composition material has not appeared dopes the second peak position. The charging and discharging result indicated that when the alloying element are many (M:V≥0.25:1.75), the material charging and discharging platform reduces, this causes the material the platform to be stable, which is advantageous in using for the battery charging and discharging. However, the doping of these three elements did not improve the capacity of the material, but declined, perhaps because this doped material doped lithium metal elements embedded in the extrusion process and the more difficult due to variation.The paper provides detailed research data and further improving the performance of the material and the industrial foundation of preparing for lithium-ion battery cathode material of lithium vanadium phosphate by high temperature solid.