PRELITHIATION REAGENT FOR LITHIUM-ION BATTERY (LIB), AND PREPARATION METHOD THEREFOR AND USE THEREOF

Abstract

The present disclosure discloses a prelithiation reagent for a lithium-ion battery (LIB), and a preparation method therefor and use thereof. The prelithiation reagent for the LIB has a chemical formula of Li.sub.5FeO.sub.4@C; and the prelithiation reagent for the LIB has a structure of secondary particles generated from the agglomeration of Li.sub.5FeO.sub.4 primary particles, and carbon is coated on a surface of the Li.sub.5FeO.sub.4 primary particles. In the present disclosure, a carbon source is mixed with a soluble salt of Fe, such that Fe ions are attached to the carbon source; then aqueous ammonia is added, such that a hydroxide with small particles and high dispersibility is generated; and then a solvothermal reaction is conducted to obtain a nano-scale oxide.

Claims

1. A prelithiation reagent for a lithium-ion battery (LIB), wherein the prelithiation reagent for the LIB has a chemical formula of Li.sub.5FeO.sub.4@C; and the prelithiation reagent for the LIB has a structure of secondary particles generated from the agglomeration of Li.sub.5FeO.sub.4 primary particles, and carbon is coated on a surface of the Li.sub.5FeO.sub.4 primary particles.

2. The prelithiation reagent for the LIB according to claim 1, wherein a content of carbon in the prelithiation reagent for the LIB is 1 wt. % to 20 wt. %.

3. The prelithiation reagent for the LIB according to claim 1, wherein the Li.sub.5FeO.sub.4 primary particles each have a particle size of less than or equal to 10 ?m.

4. A preparation method of the prelithiation reagent for the LIB according to claim 1, comprising the following steps: S1: mixing a soluble salt of Fe, a carbon source, and a solvent to obtain a mixed solution A; S2: adding aqueous ammonia to the mixed solution A to obtain a mixed solution B; S3: subjecting the mixed solution B to a solvothermal reaction, and subjecting a resulting mixture to solid-liquid separation (SLS) to obtain a Fe.sub.2O.sub.3/carbon composite; and S4: mixing the Fe.sub.2O.sub.3/carbon composite with a lithium source, and subjecting a resulting mixture to a high-temperature solid-phase reaction in an inert atmosphere to obtain the prelithiation reagent for the LIB.

5. The preparation method according to claim 4, wherein in S1, the carbon source is at least one selected from the group consisting of a carbon-containing compound and elemental carbon, the carbon-containing compound is at least one selected from the group consisting of polyaniline (PANI), polypyrrole (PPy), polyacetylene (PA), polythiophene (PTh), and polydopamine (PDA), and the elemental carbon is at least one selected from the group consisting of graphene, carbon nanotube (CNT), carbon fiber, graphdiyne (GDY), carbon black, and Ketjen black; and the carbon source is subjected to an acidification treatment.

6. The preparation method according to claim 4, wherein in S1, a molar ratio of Fe in the soluble salt of Fe to C in the carbon source is 1:(0.13-3.22).

7. The preparation method according to claim 4, wherein in S1, the solvent is at least one selected from the group consisting of water, ethanol, ethylene glycol (EG), diethylene glycol (DEG), propanol, isopropanol, propylene glycol (PG), glycerol, n-butanol, isobutanol, tert-butanol, N-methylpyrrolidone (NMP), N,N-dimethylformamide (DMF), and dimethylsulfoxide (DMSO).

8. The preparation method according to claim 4, wherein in S2, a molar ratio of the aqueous ammonia to the Fe in the soluble salt of Fe is (2-3): 1.

9. The preparation method according to claim 4, wherein in S3, the solvothermal reaction is conducted at a temperature of 150? C. to 250? C. and a pressure of 0.5 MPa to 10 MPa.

10. The preparation method according to claim 4, wherein in S4, the high-temperature solid-phase reaction is conducted at 500? C. to 800? C. for 8 h to 20 h.

11. Use of the prelithiation reagent for the LIB according to claim 1 in a cathode material of an LIB or a cathode sheet of an LIB.

12. A preparation method of the prelithiation reagent for the LIB according to claim 2, comprising the following steps: S1: mixing a soluble salt of Fe, a carbon source, and a solvent to obtain a mixed solution A; S2: adding aqueous ammonia to the mixed solution A to obtain a mixed solution B; S3: subjecting the mixed solution B to a solvothermal reaction, and subjecting a resulting mixture to solid-liquid separation (SLS) to obtain a Fe.sub.2O.sub.3/carbon composite; and S4: mixing the Fe.sub.2O.sub.3/carbon composite with a lithium source, and subjecting a resulting mixture to a high-temperature solid-phase reaction in an inert atmosphere to obtain the prelithiation reagent for the LIB.

13. A preparation method of the prelithiation reagent for the LIB according to claim 3, comprising the following steps: S1: mixing a soluble salt of Fe, a carbon source, and a solvent to obtain a mixed solution A; S2: adding aqueous ammonia to the mixed solution A to obtain a mixed solution B; S3: subjecting the mixed solution B to a solvothermal reaction, and subjecting a resulting mixture to solid-liquid separation (SLS) to obtain a Fe.sub.2O.sub.3/carbon composite; and S4: mixing the Fe.sub.2O.sub.3/carbon composite with a lithium source, and subjecting a resulting mixture to a high-temperature solid-phase reaction in an inert atmosphere to obtain the prelithiation reagent for the LIB.

14. Use of the prelithiation reagent for the LIB according to claim 2 in a cathode material of an LIB or a cathode sheet of an LIB.

15. Use of the prelithiation reagent for the LIB according to claim 3 in a cathode material of an LIB or a cathode sheet of an LIB.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The drawings are used to provide a further understanding of the technical solutions herein, constitute a part of the description, and explain the technical solutions herein in conjunction with examples of the present disclosure, without limiting the technical solutions herein. The present disclosure is further described below with reference to accompanying drawings and examples.

[0033] FIG. 1 is a scanning electron microscopy (SEM) image of the prelithiation reagent of Example 1 of the present disclosure;

[0034] FIG. 2 is an SEM image of the prelithiation reagent of Comparative Example 1 of the present disclosure;

[0035] FIG. 3 shows X-ray Diffraction (XRD) patterns of the prelithiation reagents in Example 1 and Comparative Example 1 of the present disclosure; and

[0036] FIG. 4 shows charging curves of the prelithiation reagents in Example 1 and Comparative Example 1 of the present disclosure.

DETAILED DESCRIPTION

[0037] The concepts and technical effects of the present disclosure are clearly and completely described below in conjunction with examples, so as to allow the objectives, features and effects of the present disclosure to be fully understood. Apparently, the described examples are merely some rather than all of the examples of the present disclosure. All other examples obtained by those skilled in the art based on the examples of the present disclosure without creative efforts should fall within the protection scope of the present disclosure.

Example 1

[0038] In this example, a prelithiation reagent for an LIB was prepared, which had a chemical formula of Li.sub.5FeO.sub.4@C. The prelithiation reagent had a structure of secondary particles generated from the agglomeration of Li.sub.5FeO.sub.4 primary particles; carbon was coated on a surface of the Li.sub.5FeO.sub.4 primary particles at a carbon content of 10 wt. %; and the Li.sub.5FeO.sub.4 primary particles had a particle size of less than or equal to 10 ?m. A specific preparation process was as follows: [0039] (1) FeCl.sub.3.Math.6H.sub.2O and acidified graphene were added in a molar ratio of C:Fe=0.59:0.41 to absolute ethanol, and a resulting mixture was subjected to ultrasonic dispersion to obtain a mixed solution A, where the acidified graphene was prepared by stirring graphene in 10 wt. % nitric acid for 1 h; [0040] (2) aqueous ammonia was added dropwise to the mixed solution A under ultrasonic stirring for dispersion to obtain a mixed solution B of a hydroxide and graphene, where a molar ratio of aqueous ammonia to Fe.sup.3+ was 3:1; [0041] (3) the mixed solution B was transferred to a high-temperature and high-pressure reactor to undergo a solvothermal reaction for 4 h at a temperature of 180? C. and a pressure of 1.0 MPa, a resulting mixture was filtered, and a resulting filter cake was washed and dried to obtain a Fe.sub.2O.sub.3/carbon composite, where a volume of the mixed solution B was 80% of a volume of the high-temperature and high-pressure reactor; and [0042] (4) the Fe.sub.2O.sub.3/carbon composite was mixed with lithium hydroxide in a molar ratio of Fe:Li=1:5.0, a resulting mixture was subjected to a high-temperature solid-phase reaction at 680? C. for 12 h in a nitrogen atmosphere, and a resulting product was cooled to obtain the prelithiation reagent Li.sub.5FeO.sub.4@C.

Example 2

[0043] In this example, a prelithiation reagent for an LIB was prepared, which had a chemical formula of Li.sub.5FeO.sub.4@C. The prelithiation reagent had a structure of secondary particles generated from the agglomeration of Li.sub.5FeO.sub.4 primary particles; carbon was coated on a surface of the Li.sub.5FeO.sub.4 primary particles at a carbon content of 5 wt. %; and the Li.sub.5FeO.sub.4 primary particles had a particle size of less than or equal to 10 ?m. A specific preparation process was as follows: [0044] (1) FeNO.sub.3.Math.9H.sub.2O and acidified PPy were added in a molar ratio of C:Fe=0.40:0.54 to a mixed solvent of water and ethanol in a mass ratio of 1:1, and a resulting mixture was subjected to ultrasonic dispersion to obtain a mixed solution A, where the acidified PPy was prepared by stirring PPy in 15 wt. % permanganic acid for 2 h; [0045] (2) aqueous ammonia was added dropwise to the mixed solution A under ultrasonic stirring for dispersion to obtain a mixed solution B of a hydroxide and PPy, where a molar ratio of aqueous ammonia to Fe.sup.3+ was 2.5:1; [0046] (3) the mixed solution B was transferred to a high-temperature and high-pressure reactor to undergo a solvothermal reaction for 2 h at a temperature of 200? C. and a pressure of 1.5 MPa, a resulting mixture was filtered, and a resulting filter cake was washed and dried to obtain a Fe.sub.2O.sub.3/carbon composite, where a volume of the mixed solution B was 75% of a volume of the high-temperature and high-pressure reactor; and [0047] (4) the Fe.sub.2O.sub.3/carbon composite was mixed with lithium hydroxide in a molar ratio of Fe:Li=1:5.5, a resulting mixture was subjected to a high-temperature solid-phase reaction at 650? C. for 8 h in a nitrogen atmosphere, and a resulting product was cooled to obtain the prelithiation reagent Li.sub.5FeO.sub.4@C.

Example 3

[0048] In this example, a prelithiation reagent for an LIB was prepared, which had a chemical formula of Li.sub.5FeO.sub.4@C. The prelithiation reagent had a structure of secondary particles generated from the agglomeration of Li.sub.5FeO.sub.4 primary particles; carbon was coated on a surface of the Li.sub.5FeO.sub.4 primary particles at a carbon content of 2 wt. %; and the Li.sub.5FeO.sub.4 primary particles had a particle size of less than or equal to 10 ?m. A specific preparation process was as follows: [0049] (1) FeCl.sub.3.Math.6H.sub.2O and acidified CNT were added in a molar ratio of C:Fe=0.21:0.71 to EG, and a resulting mixture was stirred for dispersion to obtain a mixed solution A, where the acidified CNT was prepared by stirring CNT in 5 wt. % perchloric acid; [0050] (2) aqueous ammonia was added dropwise to the mixed solution A under ultrasonic stirring for dispersion to obtain a mixed solution B of a hydroxide and CNT, where a molar ratio of aqueous ammonia to Fe.sup.3+ was 2:1; [0051] (3) the mixed solution B was transferred to a high-temperature and high-pressure reactor to undergo a solvothermal reaction for 1 h at a temperature of 220? C. and a pressure of 2.0 MPa, a resulting mixture was filtered, and a resulting filter cake was washed and dried to obtain a Fe.sub.2O.sub.3/carbon composite, where a volume of the mixed solution B was 85% of a volume of the high-temperature and high-pressure reactor; and [0052] (4) the Fe.sub.2O.sub.3/carbon composite was mixed with lithium hydroxide in a molar ratio of Fe:Li=1:6.0, a resulting mixture was subjected to a high-temperature solid-phase reaction at 750? C. for 14 h in a nitrogen atmosphere, and a resulting product was cooled to obtain the prelithiation reagent Li.sub.5FeO.sub.4@C.

Example 4

[0053] In this example, a prelithiation reagent for an LIB was prepared, which had a chemical formula of Li.sub.5FeO.sub.4@C. The prelithiation reagent had a structure of secondary particles generated from the agglomeration of Li.sub.5FeO.sub.4 primary particles; carbon was coated on a surface of the Li.sub.5FeO.sub.4 primary particles at a carbon content of 15 wt. %; and the Li.sub.5FeO.sub.4 primary particles had a particle size of less than or equal to 10 ?m. A specific preparation process was as follows: [0054] (1) FeCl.sub.3.Math.6H.sub.2O and acidified carbon black were added in a molar ratio of Fe:C=0.24:0.70 to a mixed solvent of water and EG in a mass ratio of 1:1, and a resulting mixture was subjected to ultrasonic dispersion to obtain a mixed solution A, where the acidified carbon black was prepared by soaking carbon black in 20 wt. % chloric acid; [0055] (2) aqueous ammonia was added dropwise to the mixed solution A under ultrasonic stirring for dispersion to obtain a mixed solution B of a hydroxide and carbon black, where a molar ratio of aqueous ammonia to Fe.sup.3+ was 3:1; [0056] (3) the mixed solution B was transferred to a high-temperature and high-pressure reactor to undergo a solvothermal reaction for 4 h at a temperature of 220? C. and a pressure of 3.0 MPa, a resulting mixture was filtered, and a resulting filter cake was washed and dried to obtain a Fe.sub.2O.sub.3/carbon composite, where a volume of the mixed solution B was 70% of a volume of the high-temperature and high-pressure reactor; and [0057] (4) the Fe.sub.2O.sub.3/carbon composite was mixed with lithium hydroxide in a molar ratio of Fe:Li=1:6.5, a resulting mixture was subjected to a high-temperature solid-phase reaction at 600? C. for 20 h in a nitrogen atmosphere, and a resulting product was cooled to obtain the prelithiation reagent Li.sub.5FeO.sub.4@C.

Comparative Example 1

[0058] In this comparative example, a prelithiation reagent was prepared. A preparation process was different from Example 1 in that the carbon source, the lithium source, and the Fe.sub.2O.sub.3 were directly mixed; and a specific process was as follows: [0059] commercial nano-scale Fe.sub.2O.sub.3, glucose, and lithium hydroxide were mixed in molar ratios of C:Fe=0.59:0.41 and Fe:Li=1:5.0, a resulting mixture was subjected to a high-temperature solid-phase reaction at 700? C. for 12 h in a nitrogen atmosphere, and a resulting product was cooled to obtain the prelithiation reagent.

Comparative Example 2

[0060] In this comparative example, a prelithiation reagent for an LIB was prepared. A preparation process was different from Example 1 in that no carbon source was added in step (1); and a specific process was as follows: [0061] (1) FeCl.sub.3.Math.6H.sub.2O was added to absolute ethanol solvent, and a resulting mixture was subjected to ultrasonic dispersion to obtain a mixed solution A; [0062] (2) aqueous ammonia was added dropwise to the mixed solution A under ultrasonic stirring for dispersion to obtain a mixed solution B of a hydroxide, where a molar ratio of aqueous ammonia to Fe.sup.3+ was 3:1; [0063] (3) the mixed solution B was transferred to a high-temperature and high-pressure reactor to undergo a solvothermal reaction for 4 h at a temperature of 180? C. and a pressure of 1.0 MPa, a resulting mixture was filtered, and a resulting filter cake was washed and dried to obtain Fe.sub.2O.sub.3, where a volume of the mixed solution B was 80% of a volume of the high-temperature and high-pressure reactor; and [0064] (4) the Fe.sub.2O.sub.3 was mixed with lithium hydroxide in a molar ratio of Fe:Li=1:5.0, a resulting mixture was subjected to a high-temperature solid-phase reaction at 680? C. for 12 h in a nitrogen atmosphere, and a resulting product was cooled to obtain the prelithiation reagent Li.sub.5FeO.sub.4.

Test Example 1

[0065] The prelithiation reagents of Examples 1 to 4 and Comparative Examples 1 to 2 were each used as a cathode active material to prepare a cathode sheet, and the cathode sheet was assembled into an LIB for a charge-discharge test. Test results were shown in Table 1.

TABLE-US-00001 TABLE 1 Primary particle size, carbon content, and initial discharge capacity of each of the prelithiation reagents in the examples and comparative examples Primary Electric Charge Charge particle Carbon conduc- capacity capacity size content tivity at 0.01 C at 0.2 C (?m) (%) (S/cm) (mAh/g) (mAh/g) Example 1 2.32 9.45 2.32 682 672 Example 2 3.56 4.76 1.96 688 664 Example 3 3.85 1.98 1.74 685 640 Example 4 2.08 14.32 2.15 673 653 Compar- 12.35 9.65 0.0023 675 195 ative Example 1 Compar- 15.68 0.13 ~0 632 12.3 ative Example 2

[0066] It can be seen from Table 1 that each of the examples has small primary particles, and shows higher electric conductivity because the primary particles are coated with carbon; each of the comparative examples has large primary particles, and shows extremely-low or even no electric conductivity. Although carbon coating is conducted in Comparative Example 1, this comparative example shows very low electric conductivity, because the coating is achieved through simple solid-phase mixing and sintering and carbon is not well coated on the material surface. Although the charge capacity of each of the examples and comparative examples at 0.01 C is higher than 600 mAh/g; the charge capacity of each of the comparative examples at 0.2 C is extremely low. Wherein, because no carbon source is introduced in Comparative Example 2, the electric conductivity is 0 and there is almost no charge capacity. Since no carbon coating is conducted or the effect of carbon coating is poor, no carbon material acts as a barrier in the sintering process, such that the primary particles continue to grow and Li.sup.+ is not easy to be released during charge at a large current. While, the charge capacity of each of the examples is still higher than 600 mAh/g, indicating that the preparation method provided by the present disclosure can effectively improve the electric conductivity of the prelithiation reagent Li.sub.5FeO.sub.4, that is, the carbon coating can greatly improve the electric conductivity of the material.

[0067] FIG. 1 and FIG. 2 are SEM images of the prelithiation reagents in Example 1 and Comparative Example 1, respectively, and it can be seen from the figures that primary particles of the prelithiation reagent in Example 1 are small and show prominent inter-particle dispersibility; while particles of the prelithiation reagent in Comparative Example 1 are significantly larger than that in Example 1, which is not conducive to the diffusion of Lit. FIG. 3 shows XRD patterns of the prelithiation reagents in Example 1 and Comparative Example 1, and it can be seen that the prelithiation reagent prepared in Example 1 has a higher peak intensity, and is a pure phase of Li.sub.5FeO.sub.4; and the prelithiation reagent prepared in Comparative Example 1 includes an impurity phase of Li.sub.5FeO.sub.2 and has a lower main-phase peak intensity, because the raw material has large particles and is difficult to react, and the reaction between Fe.sub.2O.sub.3 and lithium hydroxide is incomplete. FIG. 4 shows charge-discharge curves of the prelithiation reagents in Example 1 and Comparative Example 1 at 0.2 C, and it can be seen that Example 1 has a charge plateaus at each of 3.6 V and 4.0 V, and a high charge capacity; and Comparative Example 1 has a high charge voltage plateaus and a low capacity.

Test Example 2

[0068] With LiCoO.sub.2 as a cathode active material, each of the prelithiation reagents prepared in Examples 1 to 4 and Comparative Examples 1 to 2 was added during a stirring process of a slurry at an amount 5 wt. % of the cathode active material to prepare a cathode sheet; with graphite as an anode active material, an electrode sheet was prepared; and an LIB was assembled to undergo a charge-discharge test and a cycling test. Test results were shown in Table 2.

TABLE-US-00002 TABLE 2 Electrochemical performance test results of LiCoO.sub.2 full batteries with one of the prelithiation reagents of the examples and comparative examples Capacity Specific charge Specific retention rate Prelithiation capacity discharge ICE after 500 cycles reagent (mAh/g) capacity (mAh/g) (%) (%) Example 1 190.1 183.7 96.65 88.7 Example 2 189.5 182.3 96.20 88.2 Example 3 189.1 180.6 95.51 87.5 Example 4 189.7 181.0 95.41 87.2 Comparative 184.9 174.0 94.10 82.1 Example 1 Comparative 185.2 174.7 94.30 83.6 Example 2 Without 185.0 173.6 93.84 82.5 prelithiation reagent

[0069] It can be seen from Table 2 that, in the slurry stirring process for the LiCoO.sub.2 battery, each of the prelithiation reagents of the examples and comparative examples is added, and then a test is conducted at a current of 0.2 C and a voltage range of 3.0 V to 4.48 V; and the addition of each of the prelithiation reagents of the examples greatly improves the charge and discharge capacities and the ICE of the battery, while the addition of each of the prelithiation reagents of the comparative examples does not significantly improve the performance of the battery. It is indicated that the addition of each of the prelithiation reagents prepared in the examples can improve the specific capacity and Coulomb efficiency, and can also greatly improve the cycling performance.

[0070] The examples of present disclosure are described in detail above with reference to the accompanying drawings, but the present disclosure is not limited to the above examples. Within the scope of knowledge possessed by those of ordinary skill in the technical field, various changes can also be made without departing from the purpose of the present disclosure. In addition, the examples and features therein in the present disclosure may be combined with each other in a non-conflicting situation.