Preparation method of lithium iron phosphate and battery anode

[0030] Example 2

[0031] Respectively mix 0.01mol of ferrous acetate, 0.01mol of phosphoric acid and 0.02mol of LiOH·H 2 O was dissolved in 10ml of secondary deionized water under stirring, and then the three transparent solutions were mixed to obtain a light green mixed precipitate, then 1g of PVP was added, and the pH value of the mixed solution was adjusted to about 7 with urea aqueous solution. Ion water to 100ml, stir evenly, then transfer the mixture to a hydrothermal reaction vessel, screw it tightly and place it in a blast drying oven at a constant temperature of 180°C for continuous reaction for 12 hours, and then take the hydrothermal reaction vessel out of the oven. Place it in the air to cool to room temperature, filter, wash, and vacuum dry at 30°C. The obtained material was analyzed as pure olivine LiFePO by XRD 4 Structure, the space group is Pnma. SEM( figure 2 ) Analysis shows that the product is a very uniform spindle-shaped micron particles with a size of 0.5×2 microns, and each spindle-shaped particle is composed of many small sheet-like nanoparticles with a size of less than 100 nm. The resulting product was assembled into a button half-cell, and its charge-discharge specific capacity and cycle stability were tested. The charge-discharge curve at 0.1C is as follows Figure 7 As shown, the cycle stability under different current rates is as Figure 8 Shown. From Figure 7 with Figure 8 It can be seen that the low rate (0.1C) reversible capacity of the spindle-shaped material is about 125mAh/g, the 1C reversible capacity is about 88mAh/g, and the 10C reversible capacity is about 55mAh/g, and the cycle is very stable.

[0032] Example 3

[0033] Dissolve 0.01 mol of ferrous chloride, 0.01 mol of dipotassium hydrogen phosphate and 0.03 mol of lithium nitrate in 10 ml of secondary deionized water with stirring, and then mix the three transparent solutions to obtain a light green mixed precipitate. Then add 20ml of ethylene glycol, adjust the pH value of the mixed solution to about 9 with NaOH aqueous solution, add secondary deionized water to 100ml, stir evenly, then transfer the mixture to a hydrothermal reaction vessel, screw it tightly and place it at a constant temperature of 200℃ The reaction was continued for 24 hours in a blast drying oven, and then the hydrothermal reaction kettle was taken out of the oven, placed in the air and naturally cooled to room temperature, filtered, washed, and dried under vacuum at 80°C. The obtained material was analyzed as pure olivine LiFePO by XRD 4 Structure, the space group is Pnma. TEM( image 3 ) Analysis shows that most of the product particles have the morphology of nanorods, the diameter of the nanorods is about 100-200nm and the length is about 2 microns. In addition to nanorod-shaped particles, there are also some olive-shaped nanoparticles with a size of 200-500 nm. The resulting product was assembled into a button half-cell, and its charge-discharge specific capacity and cycle stability were tested. The charge-discharge curve at 0.1C is as follows Figure 7 As shown, the cycle stability under different current rates is as Figure 8 Shown. From Figure 7 with Figure 8 It can be seen that the low rate (0.1C) reversible capacity of the nanorod-shaped material is about 100mAh/g, the 1C reversible capacity is about 75mAh/g, and the 10C reversible capacity is about 50mAh/g, and the cycle is stable.

[0034] Example 4

[0035] Respectively mix 0.01mol of ferrous nitrate, 0.01mol of phosphoric acid and 0.03mol of LiOH·H 2 O was dissolved in 10ml of secondary deionized water under stirring, then the three transparent solutions were mixed to obtain a light green mixed precipitate, then 2g of citric acid was added, the pH of the mixture was adjusted to about 8 with ammonium carbonate, and then added twice Deionized water to 100ml, stir evenly, then transfer the mixture to a hydrothermal reaction vessel, screw it tightly and place it in a blast drying oven with a constant temperature of 220°C for continuous reaction for 24 hours, and then take the hydrothermal reaction vessel out of the oven , Placed in the air and naturally cooled to room temperature, filtered, washed, and dried under vacuum at 60°C. The obtained material was analyzed as pure olivine LiFePO by XRD 4 Structure, the space group is Pnma. SEM( Figure 4 ) Analysis shows that the product is very uniform polyhedral micron particles with a size of 2-3 microns. Detailed analysis found that most of the particles are hexagonal plate-like crystals, and a few have the morphology of cubes, rhombuses and truncated hexagons. The resulting product was assembled into a button half-cell, and its charge-discharge specific capacity and cycle stability were tested. The charge-discharge curve at 0.1C is as follows Figure 7 As shown, the cycle stability under different current rates is as Figure 8 Shown. From Figure 7 with Figure 8 It can be seen that, among all the sample materials, the sheet-like material has the smallest charge and discharge polarization, and its low rate (0.1C) reversible capacity is about 100mAh/g, 1C reversible capacity is about 70mAh/g, and 10C reversible capacity is about It is about 48mAh/g, and the cycle is stable.