Negative Electrode Material, and Preparation Method Therefor and Use Thereof

Abstract

A negative electrode material includes a composite matrix material and a carbon coating coated on the composite matrix material. The composite matrix material includes lithium silicate, silicon oxide, an activator, and silicon embedded in the lithium silicate and the silicon oxide.

Claims

1. A negative electrode material, wherein the negative electrode material comprises a composite matrix material and a carbon coating coated on the composite matrix material, wherein the composite matrix material comprises lithium silicate, an oxide of silicon, an activator and silicon, which is embedded in the lithium silicate and the oxide of silicon.

2. The negative electrode material according to claim 1, wherein the activator comprises any one of an alkali metal, a transition metal, an alkali metal oxide and a transition metal oxide or a combination of at least two therefrom.

3. The negative electrode material according to claim 1, wherein the lithium silicate is 30 wt %˜70 wt %.

4. A method for preparing the negative electrode material according to claim 1, wherein the method comprises steps of: (1) mixing an oxide of silicon containing carbon with a lithium source to obtain a raw material mixture; (2) making the raw material mixture undergo primary sintering under a protective atmosphere or a vacuum condition, to obtain a sintered mixture; (3) fusing the sintered mixture with the activator to obtain an activated precursor; and (4) making the activated precursor undergo secondary sintering under a protective atmosphere or a vacuum condition.

5. The method according to claim 4, wherein a mass ratio of the sintered mixture to the activator in step (3) is 5:1˜30:1.

6. The method according to claim 4, wherein a molar ratio of the oxide of silicon containing carbon to the lithium source in step (1) is 2.5:1˜9:1.

7. The method according to claim 4, wherein a molecular formula of the oxide of silicon containing carbon is SiO.sub.xC, where x is a constant of 0.5˜1.8.

8. The method according to claim 4, wherein a temperature of the primary sintering in step (2) is 200˜1000° C. and a duration of the primary sintering is 2 h˜6 h.

9. The method according to claim 4, wherein the method comprises steps of: (1) mixing SiOC and lithium metal according to a molar ratio of 2.5:1˜9:1 to obtain a raw material mixture; (2) sintering the raw material mixture at 500˜900° C. for 2 h˜6 h under a protective atmosphere, to obtain a sintered mixture; (3) fusing the sintered mixture and Mg according to a molar ratio of 5:1˜30:1 at a temperature of 100˜300° C. for 1 h˜4 h, to obtain an activated precursor; and (4) sintering the activated precursor at 300˜900° C. for 6 h˜10 h under a protective atmosphere to obtain a negative electrode material.

10. (canceled)

11. (canceled)

12. A lithium ion battery, wherein the lithium ion battery comprises the negative electrode material according to claim 1.

13. A lithium ion battery, wherein the lithium ion battery comprises negative electrode material, wherein the negative electrode material of the lithium ion battery is the negative electrode material according to claim 1.

14. The negative electrode material according to claim 3, wherein the oxide of silicon is 1 wt %-13 wt %.

15. The negative electrode material according to claim 3, wherein the carbon is 0.05 wt %-25 wt %.

16. The negative electrode material according to claim 3, wherein the activator is 1 wt %-10 wt %.

17. The negative electrode material according to claim 3, wherein the silicon is 20 wt %-40 wt %.

18. The negative electrode material according to claim 3, wherein the lithium silicate comprises any one of lithium orthosilicate, lithium metasilicate, lithium disilicate and lithium pentasilicate or a combination of at least two therefrom.

19. The negative electrode material according to claim 3, wherein a molecular formula of the oxide of silicon is SiO.sub.x, where x is a constant of 0.5-1.8.

20. The negative electrode material according to claim 4, wherein a temperature of the fusing is 100-300° C., and a duration of the fusing is 1 h-4 h.

21. The negative electrode material according to claim 4, the lithium source comprising any one of lithium metal, lithium carbonate, lithium hydroxide and lithium acetate or a combination of at least two therefrom.

22. The negative electrode material according to claim 4, wherein a temperature of the secondary sintering in step (4) is 150-1000° C.; and a duration of the secondary sintering is 6 h-10 h.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0053] FIG. 1 is an SEM diagram of a sample obtained from Example 1 of the present disclosure; and

[0054] FIG. 2 isn a SEM diagram of a sample obtained from Example 7 of the present disclosure.

DETAILED DESCRIPTION OF EMBODIMENTS

[0055] In order to facilitate understanding the present disclosure, examples listed in the present disclosure are as follows. Those skilled in the art should know that the examples are merely to help understand the present disclosure, but should not be considered as specific limitation to the present disclosure.

Example 1

[0056] A method for preparing a negative electrode material included steps of:

[0057] (1) mixing SiOC and lithium metal according to a molar ratio of 3:1 to obtain a raw material mixture;

[0058] (2) sintering the raw material mixture at 700° C. for 4 h under a protective atmosphere to obtain a sintered mixture;

[0059] (3) fusing the sintered mixture and Mg according to a mass ratio of 10:1 at a temperature of 180° C. for 2 h to obtain an activated precursor; and

[0060] (4) sintering the activated precursor at 750° C. for 8 h under a protective atmosphere to obtain a negative electrode material with a morphology feature as shown in FIG. 1, wherein it can be seen from the figure that the negative electrode material obtained has a particle size of 5˜10 μm, and has a carbon coating at the outermost layer.

Example 2

[0061] Different from Example 1, the molar ratio of the sintered mixture to Mg was 5:1 in step (3).

Example 3

[0062] Different from Example 1, the molar ratio of the sintered mixture to Mg was 30:1 in step (3).

Example 4

[0063] Different from Example 1, the molar ratio of the sintered mixture to Mg was 4:1 in step (3).

Example 5

[0064] Different from Example 1, the molar ratio of the sintered mixture to Mg was 31:1 in step (3).

Example 6

[0065] A method for preparing a negative electrode material included steps of:

[0066] (1) mixing SiO.sub.xC (x=0.5) and lithium hydroxide according to a molar ratio of 9:1 to obtain a raw material mixture;

[0067] (2) sintering the raw material mixture at 200° C. for 6 h under a nitrogen atmosphere to obtain a sintered mixture;

[0068] (3) fusing the sintered mixture and K.sub.2O according to a molar ratio of 5:1 at a temperature of 100° C. for 4 h to obtain an activated precursor; and

[0069] (4) sintering the activated precursor at 150° C. for 10 h under a nitrogen atmosphere to obtain a negative electrode material.

Example 7

[0070] A method for preparing a negative electrode material included steps of:

[0071] (1) mixing SiO.sub.xC (x=1.8) and lithium metal according to a molar ratio of 2.5:1 to obtain a raw material mixture;

[0072] (2) sintering the raw material mixture at 1000° C. for 2 h under an argon atmosphere to obtain a sintered mixture;

[0073] (3) fusing the sintered mixture and Al according to a molar ratio of 30:1 at a temperature of 300° C. for 1 h to obtain an activated precursor; and

[0074] (4) sintering the activated precursor at 1000° C. for 6 h under an argon atmosphere to obtain a negative electrode material with a morphology feature as shown in FIG. 2, wherein it can be seen from the figure that the negative electrode material obtained has a particle size of 5˜10 μm, and has a carbon coating at the outermost layer.

Comparative Example 1

[0075] Different from Example 1, no Mg was added in step (3).

Comparative Example 2

[0076] Different from Example 1, SiOC was replaced by SiO.sub.2 in step (1).

[0077] Property Test:

[0078] The prepared negative electrode materials were subjected to the following property tests:

[0079] (1) Preparing a lithium ion battery: the prepared negative electrode material, conductive carbon black, CMC/SBR were coated on a copper foil at a ratio 75:15:10, to prepare a negative electrode sheet, a metal lithium sheet was used as a counter electrode, and PP/PE was used as a separator, to make a button battery.

[0080] (2) Testing first Coulombic efficiency: electrochemical property of the battery were tested using a LAND 5 V/10 mA type battery tester, wherein the charging and discharging voltage was 1.5 V, the charging and discharging rate was 0.1 C, and the first Coulombic efficiency=first charging specific capacity/first discharging specific capacity.

[0081] (3) Testing 50-cycle capacity retention ratio: the electrochemical property of the battery was tested using a LAND 5 V/10 mA type battery tester, wherein the charging and discharging voltage was 1.5 V, the charging and discharging rate was 0.1 C, and 50-cycle capacity retention ratio=the 50.sup.th charging specific capacity/the first charging specific capacity.

TABLE-US-00001 TABLE 1 First Discharging 50-cycle Capacity Specific First Coulombic Retention Ratio Capacity(mAh/g) Efficiency(%) (%) Example 1 1502 88.8 88.7 Example 2 1430 88.7 88.2 Example 3 1477 86.3 87.8 Example 4 1399 83.6 82.0 Example 5 1263 85.7 83.5 Example 6 1463 85.1 85.3 Example 7 1377 86.5 84.6 Comparative 1105 74.1 71.6 Example 1 Comparative 1378 70.6 63.7 Example 2

[0082] It can be seen from Table 1 that the lithium silicate in the negative electrode material prepared in Examples 1˜7 of the present disclosure is an electrochemically active ingredient, and further the negative electrode material has good electrochemical property. The first discharging specific capacity is no less than 1263 mAh/g, the first Coulombic efficiency is no less than 83.6%, and 50-cycle capacity retention ratio is no less than 82% at 0.1 C current density.

[0083] It can be seen from Table 1 that, the first Coulombic efficiency and the 50-cycle capacity retention ratio of Example 4 are lower than those of Example 1, possibly because the addition amount of the activator Mg in Example 4 is too large, and the structure of lithium silicate is destroyed, so that the first discharging specific capacity, the first Coulombic efficiency and the 50-cycle capacity retention ratio of the negative electrode material prepared are low.

[0084] It can be seen from Table 1 that, the first discharging specific capacity, the first Coulombic efficiency and the 50-cycle capacity retention ratio of Example 5 are lower than those of Example 1, possibly because the addition amount of the activator Mg in Example 5 is too small, then the lithium silicate in the negative electrode material is not activated, so that the first discharging specific capacity, the first Coulombic efficiency and the 50-cycle capacity retention ratio of the negative electrode material prepared are low.

[0085] It can be seen from Table 1 that, the first discharging specific capacity, the first Coulombic efficiency and the 50-cycle capacity retention ratio of Comparative Example 1 are lower than those of Example 1, possibly because no activator Mg is added in Comparative Example 1, then the lithium silicate in the negative electrode material is a chemical inert component, so that the first discharging specific capacity, the first Coulombic efficiency and the 50-cycle capacity retention ratio of the negative electrode material prepared are low.

[0086] It can be seen from Table 1 that the first Coulombic efficiency and the 50-cycle capacity retention ratio of Comparative Example 2 are lower than those of Example 1, possibly because the silicon source in Comparative Example 2 is SiO.sub.2, and there is no carbon coating in the negative electrode material prepared, so that the first Coulombic efficiency and the 50-cycle capacity retention ratio of the negative electrode material prepared are low.

[0087] The applicant states that the detailed process equipment and process flow of the present disclosure are illustrated through the above examples in the present disclosure, but the present disclosure is not limited to the above detailed process equipment and process flow, that is, it does not mean that the present disclosure must be implemented relying upon the detailed process equipment and process flow above.