Phosphate-based positive electrode material, preparation method thereof, positive electrode sheet, and battery

Abstract

The application discloses a phosphate-based positive electrode material, a preparation method thereof, a positive electrode sheet and a battery. The preparation method of the phosphate-based positive electrode material comprises the following steps: preparing a solid-phase precursor material by using raw materials containing an iron source, a phosphorus source, a lithium source, a first carbon source and a doping element source; placing the solid-phase precursor material in a non-active atmosphere, pre-sintering the solid-phase precursor material at 500-600 DEG C for 6-12 hours to obtain a semi-finished product; placing materials containing the semi-finished product in a non-active atmosphere, performing gradient sintering, and then reducing the temperature to 20-30 DEG C at a rate of 0.5-3 DEG C / min to obtain the phosphate-based positive electrode material; and the doping element source accounts for 0.5wt%-1.5wt% of the total mass of the phosphate-based positive electrode material. According to the embodiment of the application, the crystallinity in the crystal can be controlled, so that the cycle stability of the phosphate-based positive electrode material is effectively improved.

Claims

1. A method for preparing a phosphate-based cathode material, characterized in that, include: Solid-phase precursor materials are prepared from raw materials containing iron source, phosphorus source, lithium source, first carbon source and dopant element source. The solid precursor material is placed in an inactive atmosphere and pre-sintered at 500~600 °C for 6~12 h to obtain a semi-finished product; The material containing the semi-finished product is placed in an inactive atmosphere and subjected to gradient sintering, and then cooled to 20-30 °C at a rate of 0.5-3 °C / min to obtain a phosphate-based cathode material. The doping element source accounts for 0.5wt% to 1.5wt% of the total mass of the phosphate-based cathode material. The gradient sintering includes setting a first gradient, a second gradient, and a third gradient, wherein the temperature of the first gradient is T. 1 The time is t 1 The temperature of the second gradient is T. 2 The time is t 2 The temperature of the third gradient is T. 3 The time is t 3 Among them, 300 ℃≤T 1 ≤600℃, 600℃ <T 2 ≤700 ℃, 700 ℃ <T 3 ≤800 ℃, 4 h≤t 1 ≤8 h, 4 h≤t 2 ≤8 h, 4 h≤t 3 ≤8 h.

2. The preparation method according to claim 1, characterized in that, The first gradient, the second gradient, and the third gradient each include several sub-gradients, and the temperature and time corresponding to the sub-gradients are all within a preset range.

3. The preparation method according to claim 2, characterized in that, The heating rates of the first gradient, the second gradient, and the third gradient are independently selected from 1 to 10 °C / min.

4. The preparation method according to claim 1, characterized in that, The doping element source includes an oxide or soluble salt of at least one element selected from Ti, Mg, V and Nb; And / or, the first carbon source is an organic carbon source, which includes at least one of sucrose, glucose, fructose, PEG, PVP and CTAB; And / or, in the step of preparing a solid-phase precursor material from raw materials containing an iron source, a phosphorus source, a lithium source, a first carbon source, and a dopant element source, the raw materials further contain a manganese source. And / or, in the step of placing the material containing the semi-finished product in an inactive atmosphere, the material further includes a second carbon source.

5. The preparation method according to claim 4, characterized in that, The second carbon source is an inorganic carbon source, which includes at least one of carbon nanotubes, graphite powder, graphene, Ketjen black, and acetylene black.

6. The preparation method according to claim 5, characterized in that, The first carbon source accounts for 1 wt% to 10 wt% of the total mass of the phosphate-based cathode material; And / or, the second carbon source accounts for 0.5wt% to 3.0wt% of the total mass of the phosphate-based cathode material.

7. The preparation method according to any one of claims 1-6, characterized in that, The chemical formula of the phosphate-based cathode material is LiM z Mn x Fe y PO4 or LiM z Mn x Fe y PO4 / C, where M is the dopant element, 0 ≤ x < 1, 0 <y<1,0<z<0.1,x+y+z=1。 8. The preparation method according to claim 1, characterized in that, Inactive atmospheres include at least one of nitrogen, helium, argon, and neon.

9. A phosphate-based cathode material, characterized in that, The phosphate-based cathode material obtained by the preparation method according to any one of claims 1-8 has a gradient difference in crystallinity from the inside to the outside.

10. A positive electrode plate, characterized in that, The positive electrode sheet includes a positive current collector and a positive electrode film layer located on at least one surface of the positive current collector, wherein the positive electrode film layer includes a phosphate-based positive electrode material obtained by the preparation method of any one of claims 1-8 or a phosphate-based positive electrode material as described in claim 9.

11. A battery, characterized in that, Includes the positive electrode sheet as described in claim 10.

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