Lithium-supplementing additive and preparation method therefor, positive electrode material, positive electrode sheet, and battery

Abstract

A lithium-supplementing additive and a preparation method therefor, a positive electrode material, a positive electrode sheet, and a battery. The lithium-supplementing additive comprises a lithium-containing compound, the lithium-containing compound is selected from one or a combination of more compounds as represented by the following chemical formula: aLiFeαMnβM1-α-βO2-γXγ(1-a)Li2FeδMnεN1-δ-εO3-ηXη, where the element M and the element N are each independently selected from one or more of Zr, Co, Sr, Al, Ni, W, Ti, Cu, Mg, Zn, Ca, Ba, Sc, Ga, Y, La, In, Ce, Ge, Hf, Sn, Nb, Ta, V and Sb, the X is the element F, 0.4≤a≤0.9, 0<α≤1, 0≤β≤1, 0<α+β≤1, 0≤γ≤0.1, 0<δ≤1, 0≤ε≤1, 0<δ+ε≤1, and 0≤η≤0.1. The lithium-supplementing additive can stably and uniformly supplement lithium and improve the cycling stability.

Description

Lithium supplement additive and preparation method thereof, positive electrode material, positive electrode sheet and battery

[0001] This application claims priority to the Chinese patent application filed with the China Patent Office on September 28, 2023, with application number 202311281693.1. The entire contents of the above application are incorporated by reference into this application. Technical Field

[0002] The present application relates to the technical field of lithium batteries, and in particular to a lithium supplement additive and a preparation method thereof, a positive electrode material, a positive electrode sheet and a lithium ion battery. Background Art

[0003] Phosphate cathode materials have attracted considerable attention due to their safety and long cycle life. However, they still have many shortcomings in practical applications. Currently, phosphate cathode materials suffer from rapid capacity decay in the early stages of room-temperature cycling. This is primarily due to the instability of the negative electrode SEI membrane during these initial stages. The repair and generation of the SEI membrane continuously consumes active lithium released from the positive electrode, increasing the irreversible capacity of the positive electrode and causing rapid decay in the early stages of cycling. To reduce the loss of active lithium in phosphate cathode materials during these initial stages, it is necessary to introduce lithium-supplementing additives into the cathode formulation to provide active lithium and compensate for this loss. Technical issues

[0004] The present application provides a lithium supplement additive and a preparation method thereof, a positive electrode material, a positive electrode plate and a lithium ion battery, which are used to improve the technical problem of unstable lithium-rich phase structure of the lithium supplement material. Technical Solutions

[0005] In a first aspect, the present application provides a lithium supplement additive, wherein the lithium supplement additive comprises a lithium-containing compound, wherein the lithium-containing compound is selected from one or more combinations of compounds represented by chemical formula (I): aLiFe α Mn β M 1-α-β O 2-γ X γ (1-a)Li2F3 δ Mn ε N 1-δ-ε O 3-η X η (I);

[0006] Wherein, the M element and the N element are each independently selected from one or more of Zr, Co, Sr, Al, Ni, W, Ti, Cu, Mg, Zn, Ca, Ba, Sc, Ga, Y, La, In, Ce, Ge, Hf, Sn, Nb, Ta, V, and Sb; the X is an F element, and 0.4≤a≤0.9, 0<α≤1, 0≤β≤1, 0<α+β≤1, 0≤γ≤0.1, 0<δ≤1, 0≤ε≤1, 0<δ+ε≤1, and 0≤η≤0.1;

[0007] The surface basicity of the lithium supplement additive is 10 to 400 μmol·g -1 .

[0008] In a second aspect, the present application provides a method for preparing a lithium supplement additive, comprising the following steps:

[0009] The precursor material was prepared by spray pyrolysis;

[0010] mixing the precursor material with a lithium source and calcining the mixture to obtain a lithium-containing compound;

[0011] The lithium supplement additive comprises a lithium-containing compound, and the lithium-containing compound is selected from one or more combinations of compounds represented by chemical formula (I): aLiFe α Mn β M 1-α-β O 2-γ X γ (1-a)Li2Fe δ Mn ε N 1-δ-ε O 3-η X η (I);

[0012] Wherein, the M element and the N element are each independently selected from one or more of Zr, Co, Sr, Al, Ni, W, Ti, Cu, Mg, Zn, Ca, Ba, Sc, Ga, Y, La, In, Ce, Ge, Hf, Sn, Nb, Ta, V, and Sb; the X is an F element, and 0.4≤a≤0.9, 0<α≤1, 0≤β≤1, 0<α+β≤1, 0≤γ≤0.1, 0<δ≤1, 0≤ε≤1, 0<δ+ε≤1, and 0≤η≤0.1.

[0013] In a third aspect, the present application provides a positive electrode material comprising a positive electrode active material and the lithium supplement additive as described above.

[0014] In a fourth aspect, the present application provides a positive electrode plate, which contains the lithium supplement additive as described above.

[0015] In a fifth aspect, the present application provides a battery comprising the positive electrode plate as described above. Beneficial effects

[0016] The beneficial effects of this application are:

[0017] The lithium-supplementing additive of the present invention includes a lithium-containing compound. By introducing a large amount of iron into the lithium-containing compound, the cost is reduced. 3+ / Fe 4+ Unique controllable redox reversibility can provide more active lithium required by the negative electrode, achieve efficient lithium replenishment in the first cycle, and obtain the best lithium replenishment effect;

[0018] In detail, the lithium-containing compound of the present application is composed of LiFe α Mn β M 1-α-β O 2-γ X γ and Li2Fe δ Mn ε N 1- δ-ε O 3-η X η Two phases, the lithium-rich phase Li2Fe δ Mn ε N 1-δ-ε O 3-η X η During the first charge at high voltage, due to irreversible oxygen release and Fe 3+ / Fe 4+ The unique controllable redox reversibility makes its initial coulombic efficiency low, which can provide more active lithium required for the negative electrode; while LiFe α Mn β M 1-α-β O 2-γ X γ Phase due to Fe 3+ / Fe 4+ The unique controllable redox reversibility can provide more reversible capacity while providing part of the active lithium required for the negative electrode, and can also stabilize the lithium-rich phase structure. The combination of the two can not only achieve a good lithium replenishment effect, but the material itself can also contribute capacity in subsequent cycles, which can reduce the reduction in energy density caused by the introduction of additives. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the technical solutions in the embodiments of the present application or related technologies, the following is a brief introduction to the drawings required for use in the embodiments or related technical descriptions. Obviously, the drawings described below are some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work. The positional relationships described in the drawings in the following description are based on the directions of the components shown in the diagrams, unless otherwise specified.

[0020] FIG1 is an XRD test diagram of the lithium supplement additive material prepared in Example 4 of the present application. Modes for Carrying Out the Invention

[0021] Example 1

[0022] This embodiment provides a lithium supplement additive including a lithium-containing compound, wherein the chemical formula of the lithium-containing compound is 0.7LiFeO2·0.3Li2FeO3.

[0023] This embodiment provides a method for preparing the above-mentioned lithium supplement additive, comprising the following steps:

[0024] S1. Dissolve an iron source and a nucleating agent in deionized water at a molar ratio of 1:0.05 and mix them uniformly to obtain a mixed solution. Then, pressurize the mixed solution into spray droplets using a two-fluid nozzle with a pore size of 2 μm. Then, the spray droplets are fed into a pyrolysis reactor at a flow rate of 20 L / min by a carrier gas, and rapidly pyrolyze at high temperature to obtain a precursor material.

[0025] Wherein, the iron source is ferric nitrate, the nucleating agent is ammonium nitrate; the carrier gas is nitrogen; and the spray pyrolysis reaction temperature is 950°C.

[0026] S2, mixing the prepared precursor material with a lithium source in a molar ratio of 1:1.3; after the mixture is evenly mixed, calcining at 800° C. for 10 h in an oxygen-containing atmosphere to obtain a lithium-containing compound, i.e., a lithium supplement additive, whose chemical formula is 0.7LiFeO2·0.3Li2FeO3;

[0027] Wherein, the lithium source is lithium hydroxide; the lithium content of the lithium-containing compound is 9.0wt%; the particle size D of the lithium-containing compound is V 50 is 800 nm, and the specific surface area of ​​the lithium-containing compound is 15 m 2 / g, the pH value of the lithium supplement additive is 11.2; the residual lithium content of the lithium supplement additive is 950ppm;

[0028] S3. The prepared lithium supplement additive is mixed with the phosphate positive electrode main material LiFePO4 in a mass ratio of 1:9, and a conductive agent Super P and a binder PVDF are added to prepare a composite positive electrode slurry. The slurry is used to coat the positive electrode sheet, and the negative electrode sheet is used to prepare a lithium-ion battery. After the battery is activated by a high voltage of 4.2V to 4.8V, the cycle performance of the lithium-ion battery is tested.

[0029] Example 2

[0030] This embodiment provides a lithium supplement additive including a lithium-containing compound, wherein the chemical formula of the lithium-containing compound is 0.6LiFeO2·0.4Li2FeO3.

[0031] This embodiment provides a method for preparing the above-mentioned lithium supplement additive, comprising the following steps:

[0032] S1. Dissolve an iron source and a nucleating agent in deionized water at a molar ratio of 1:0.03 and mix them uniformly to obtain a mixed solution. Then, pressurize the mixed solution into spray droplets using a two-fluid nozzle with a pore size of 5 μm. Then, the spray droplets are fed into a pyrolysis reactor at a flow rate of 10 L / min by a carrier gas, and rapidly pyrolyze at high temperature to obtain a precursor material.

[0033] Wherein, the iron source is ferric chloride, the nucleating agent is urea; the carrier gas is argon; and the spray pyrolysis reaction temperature is 780°C.

[0034] S2. The obtained precursor material is mixed with a lithium source in a molar ratio of 1:1.4; after the mixture is uniformly mixed, it is calcined at 900° C. for 12 h in an oxygen-containing atmosphere to obtain a lithium-containing compound having a chemical formula of 0.6LiFeO2·0.4Li2FeO3;

[0035] Wherein, the lithium source is lithium hydroxide; the lithium content of the lithium-containing compound is 9.7wt%; the particle size D of the lithium-containing compound is V 50 is 2 μm, and the specific surface area of ​​the lithium-containing compound is 8.3 m 2 / g.

[0036] S3, uniformly mixing the prepared lithium-containing compound and the carbon source at a mass ratio of 1:0.01, and then performing a high-temperature heat treatment under an argon atmosphere to obtain a lithium supplement additive;

[0037] Wherein, the carbon source is cyclodextrin; the surface carbon element coating amount is 10000 ppm; the pH value of the lithium supplement additive is 10.8; the residual lithium content of the lithium supplement additive is 1380 ppm;

[0038] S4. The prepared lithium supplement additive is mixed with the phosphate positive electrode main material LiFePO4 in a mass ratio of 10:90, and a conductive agent Super P and a binder PVDF are added to prepare a composite positive electrode slurry. The slurry is used to coat the positive electrode sheet, and a lithium-ion battery is prepared by matching the negative electrode sheet. After the battery is activated by a high voltage of 4.2V to 4.8V, the cycle performance of the lithium-ion battery is tested.

[0039] Example 3

[0040] The rest is the same as Example 1, except that the molar ratio of the iron source to the nucleating agent in S1 is 1:0.02, the molar ratio of the precursor material to the lithium source in S2 is 1:1.35, and the chemical formula of the prepared lithium-containing compound is 0.65LiFeO2·0.35Li2FeO3.

[0041] Example 4

[0042] This embodiment provides a lithium supplement additive comprising a lithium-containing compound, the chemical formula of which is 0.8LiFe 0.42 Mn 0.58 O2·0.2Li2Fe 0.6 Mn 0.4 O3.

[0043] This embodiment provides a method for preparing the above-mentioned lithium supplement additive, comprising the following steps:

[0044] S1. Dissolve a manganese source, an iron source, and a nucleating agent in deionized water at a molar ratio of 1:0838:0.025 and mix them uniformly to obtain a mixed solution. The concentration of manganese ions in the mixed solution is controlled to be 0.2 mol / L. Then, the mixed solution is pressed into spray droplets using a two-fluid nozzle with a pore size of 3 μm. The spray droplets are then fed into a pyrolysis reactor at a flow rate of 20 L / min by a carrier gas, and rapidly pyrolyzed at high temperature to obtain a precursor material.

[0045] Wherein, the manganese source is manganese sulfate, the iron source is ferric sulfate, the nucleating agent is urea; the carrier gas is helium; and the spray pyrolysis reaction temperature is 880°C.

[0046] S2. The obtained precursor material is mixed with a lithium source in a molar ratio of 1:1.2; after the mixture is evenly mixed, it is calcined at 900°C for 15 hours in an oxygen-containing atmosphere to obtain a lithium-containing compound, whose chemical formula is 0.8LiFe 0.42 Mn 0.58 O2·0.2Li2Fe 0.6 Mn 0.4 O3;

[0047] Wherein, the lithium source is lithium acetate; the lithium content of the lithium-containing compound is 8.3wt%; the particle size D of the lithium-containing compound isV 50 is 1 μm, and the specific surface area of ​​the lithium-containing compound is 12 m 2 / g.

[0048] S3. Evenly mix the prepared lithium-containing compound and the carbon source at a mass ratio of 1:0.02, and then perform a high-temperature heat treatment under a hydrogen atmosphere to obtain a lithium supplement additive.

[0049] Wherein, the carbon source is sucrose; the surface carbon element coating amount is 20000 ppm; the pH value of the lithium supplement additive is 11.6; and the residual lithium content of the lithium supplement additive is 2240 ppm.

[0050] S4. The prepared lithium supplement additive is mixed with the phosphate positive electrode main material LiFePO4 in a mass ratio of 10:90, and a conductive agent Super P and a binder PVDF are added to prepare a composite positive electrode slurry. The slurry is used to coat the positive electrode sheet, and a lithium-ion battery is prepared by matching the negative electrode sheet. After the battery is activated by a high voltage of 4.2V to 4.8V, the cycle performance of the lithium-ion battery is tested.

[0051] By performing XRD test on the product, as shown in Figure 1, it can be seen that the peak with an asterisk at 20° to 25° is Li2Fe δ Mn ε N 1-δ-ε O 3-η X η The phase characteristic peak is a monoclinic structure with a space group of C2 / m. The other diffraction peaks correspond to the α-NaFeO2 diffraction peaks, which correspond to LiFe α Mn β M 1-α-β O 2-γ X γ Phase, is a layered structure of α-NaFeO2 with space group R-3m, which proves that the prepared material has LiFe α Mn β M 1-α-β O 2-γ X γ and Li2Fe δ Mn ε N 1-δ-ε O 3-η X η of two phases.

[0052] Example 5

[0053] The rest is the same as Example 4, except that in S4, the main material of the positive electrode is lithium nickel cobalt manganese oxide.

[0054] Example 6

[0055] This embodiment provides a lithium supplement additive comprising a lithium-containing compound, the chemical formula of which is 0.6LiFe 0.68 Mn 0.31 Al 0.01 O2·0.4Li2Fe 0.45 Mn 0.54 Al 0.01 O3.

[0056] This embodiment provides a method for preparing the above-mentioned lithium supplement additive, comprising the following steps:

[0057] S1. Dissolve a manganese source, an iron source, an M source, a N source, and a nucleating agent in deionized water at a molar ratio of 1:1.463:0.0015:0.001:0.015 and mix them uniformly to obtain a mixed solution. The concentration of manganese ions in the mixed solution is controlled to be 0.1 mol / L. Then, the mixed solution is pressed into spray droplets using a two-fluid nozzle with a pore size of 4 μm. The spray droplets are then fed into a pyrolysis reactor at a flow rate of 15 L / min by a carrier gas, and rapidly pyrolyzed at high temperature to obtain a precursor material.

[0058] The manganese source is manganese nitrate, the iron source is ferric nitrate, the M source is aluminum nitrate, the N source is aluminum acetate, and the nucleating agent is ammonium nitrate; the carrier gas is argon; and the spray pyrolysis reaction temperature is 920°C.

[0059] S2. The obtained precursor material is mixed with a lithium source in a molar ratio of 1:1.4; after the mixture is evenly mixed, the mixture is calcined at 850°C for 18 hours in an oxygen-containing atmosphere to obtain a lithium-containing compound, whose chemical formula is 0.6LiFe 0.68 Mn 0.31 Al 0.01 O2·0.4Li2Fe 0.45 Mn 0.54 Al 0.01 O3;

[0060] Wherein, the lithium source is lithium hydroxide; the lithium content of the lithium-containing compound is 9.7wt%; the particle size D of the lithium-containing compound is V 50 is 4 μm, and the specific surface area of ​​the lithium-containing compound is 4.3 m 2 / g.

[0061] S3. Evenly mix the prepared lithium-containing compound and the carbon source at a mass ratio of 1:0.025, and then perform a high-temperature heat treatment under a nitrogen and argon atmosphere to obtain a lithium supplement additive.

[0062] Among them, the carbon source is starch; the surface carbon element coating amount is 25000 ppm, the pH value of the lithium supplement additive is 11.3; and the residual lithium content of the lithium supplement additive is 1340 ppm.

[0063] S4, the prepared lithium supplement additive and the phosphate positive electrode main material LiMn 0.7 Fe 0.3 PO4 was mixed in a mass ratio of 17:83, and a conductive agent Super P and a binder PVDF were added to prepare a composite positive electrode slurry. The slurry was used to coat the positive electrode sheet, and a lithium-ion battery was made with the negative electrode sheet. After the battery was activated by a high voltage of 4.2V to 4.8V, the cycle performance of the lithium-ion battery was tested.

[0064] Example 7

[0065] This embodiment provides a lithium supplement additive comprising a lithium-containing compound, the chemical formula of which is 0.7LiFe 0.55 Mn 0.43 Co 0.02 O 1.95 F 0.05 0.3Li2Fe 0.33 Mn 0.65 Co 0.02 O 2.95 F 0.05 .

[0066] This embodiment provides a method for preparing the above-mentioned lithium supplement additive, comprising the following steps:

[0067] S1. Dissolve a manganese source, an iron source, an M source, a N source, an X source, and a nucleating agent in deionized water at a molar ratio of 1:0.976:0.028:0.012:0.101:0.035 and mix them uniformly to obtain a mixed solution. The concentration of manganese ions in the mixed solution is controlled to be 0.5 mol / L. Then, the mixed solution is pressed into a spray droplet using a two-fluid nozzle with an aperture of 8 μm. The spray droplet is then fed into a pyrolysis reactor at a flow rate of 25 L / min by a carrier gas, and rapidly pyrolyzed at high temperature to obtain a precursor material.

[0068] The manganese source is manganese acetate, the iron source is ferric acetate, the M source is cobalt acetate, the N source is cobalt nitrate, the X source is NH4F, the nucleating agent is urea, the carrier gas is helium, and the spray pyrolysis reaction temperature is 780°C.

[0069] S2. The obtained precursor material is mixed with a lithium source in a molar ratio of 1:1.3; after the mixture is evenly mixed, the mixture is calcined at 950°C for 12 hours in an oxygen-containing atmosphere to obtain a lithium-containing compound, whose chemical formula is 0.7LiFe 0.55 Mn 0.43 Co 0.02 O 1.95 F 0.05 0.3Li2Fe 0.33 Mn0.65 Co 0.02 O 2.95 F 0.05 ;

[0070] Wherein, the lithium source is lithium acetate; the lithium content of the lithium-containing compound is 9.0wt%; the particle size D of the lithium-containing compound is V 50 is 6 μm, and the specific surface area of ​​the lithium-containing compound is 1.8 m 2 / g.

[0071] S3. Evenly mix the prepared lithium-containing compound and the carbon source at a mass ratio of 1:0.015, and then perform a high-temperature heat treatment under a nitrogen atmosphere to obtain a lithium supplement additive.

[0072] Wherein, the carbon source is polyvinyl alcohol; the surface carbon element coating amount is 15000 ppm; the pH value of the lithium supplement additive is 11.8; and the residual lithium content of the lithium supplement additive is 560 ppm.

[0073] S4. The prepared lithium supplement additive is mixed with the phosphate positive electrode main material LiFePO4 in a mass ratio of 28:72, and a conductive agent Super P and a binder PVDF are added to prepare a composite positive electrode slurry. The slurry is used to coat the positive electrode sheet, and a lithium-ion battery is prepared by matching it with the negative electrode sheet. After the battery is activated by a high voltage of 4.2V to 4.8V, the cycle performance of the lithium-ion battery is tested.

[0074] Example 8

[0075] The rest is the same as Example 6, except that in S1: the M source is nickel sulfate, the N source is zirconium sulfate; the chemical formula of the obtained lithium-containing compound is 0.6LiFe 0.68 Mn 0.31 Ni 0.01 O2·0.4Li2Fe 0.45 Mn 0.54 Zr 0.01 O3.

[0076] Example 9

[0077] The rest is the same as Example 6, except that in S1: the M source is zinc nitrate, the N source is titanium nitrate; the chemical formula of the obtained lithium-containing compound is 0.6LiFe 0.68 Mn 0.31 Zn 0.01 O2·0.4Li2Fe 0.45 Mn 0.54 Ti 0.01 O3.

[0078] Example 10

[0079] The rest is the same as Example 6, except that in S1: the M source is cobalt acetate, the N source is tantalum nitrate; the chemical formula of the obtained lithium-containing compound is 0.6LiFe 0.68 Mn 0.31 Co 0.01 O2·0.4Li2Fe 0.45 Mn 0.54 Ta 0.01 O3.

[0080] Example 11

[0081] The rest is the same as Example 6, except that in S1: the M source is nickel nitrate, the N source is lanthanum nitrate; the chemical formula of the obtained lithium-containing compound is 0.6LiFe 0.68 Mn 0.31 Ni 0.01 O2·0.4Li2Fe 0.45 Mn 0.54 La 0.01 O3.

[0082] Example 12

[0083] The rest is the same as Example 7, except that in S1: the M source is nickel sulfate, the N source is strontium nitrate, and the X source is NH4F; the chemical formula of the obtained lithium-containing compound is 0.7LiFe 0.55 Mn 0.43 Ni 0.02 O 1.95 F 0.05 0.3Li2Fe 0.33 Mn 0.65 Sr 0.02 O 2.95 F 0.05 .

[0084] Example 13

[0085] The rest is the same as Example 7, except that in S1: the M source is aluminum sulfate, the N source is niobium nitrate, and the X source is LiF; the chemical formula of the obtained lithium-containing compound is 0.7LiFe 0.55 Mn 0.43 Al 0.02 O 1.95 F 0.05 0.3Li2Fe 0.33 Mn 0.65 Nb 0.02 O 2.95 F 0.05 .

[0086] Example 14

[0087] The rest is the same as Example 7, except that in S1: the M source is zirconium nitrate, the N source is zirconium sulfate, and the X source is NH4F; the chemical formula of the obtained lithium-containing compound is 0.7LiFe 0.55 Mn 0.43 Zr 0.02 O 1.95 F 0.05 0.3Li2Fe 0.33 Mn 0.65 Zr 0.02 O 2.95 F 0.05 .

[0088] Example 15

[0089] The rest is the same as Example 7, except that in S1: the M source is magnesium chloride, the N source is tungsten nitrate, and the X source is LiF; the chemical formula of the obtained lithium-containing compound is 0.7LiFe 0.55 Mn 0.43 Mg 0.02 O 1.95 F 0.05 0.3Li2Fe 0.33 Mn 0.65 W 0.02 O 2.95 F 0.05 .

[0090] Comparative Example 1

[0091] A composite positive electrode slurry was prepared by coating the phosphate positive electrode main material LiFePO4, the conductive agent Super P, and the binder PVDF. The slurry was used to coat the positive electrode sheet, and a lithium-ion battery was made by combining it with the negative electrode sheet. After the battery was activated by a high voltage of 4.2V to 4.8V, the cycle performance of the lithium-ion battery was tested.

[0092] Comparative Example 2

[0093] The main material of phosphate positive electrode LiMn 0.7 Fe 0.3 A composite positive electrode slurry was prepared using PO4, conductive agent Super P, and binder PVDF. The slurry was used to coat the positive electrode sheet, which was then used to make a lithium-ion battery with the negative electrode sheet. After the battery was activated with a high voltage of 4.2V to 4.8V, the cycle performance of the lithium-ion battery was tested.

[0094] Comparative Example 3

[0095] A composite positive electrode slurry was prepared by combining lithium supplement additive Li5FeO4, phosphate positive electrode main material LiFePO4, conductive agent Super P, and binder PVDF. The slurry was used to coat the positive electrode sheet, which was then matched with the negative electrode sheet to make a lithium-ion battery. After the battery was activated by a high voltage of 4.2V to 4.8V, the cycle performance of the lithium-ion battery was tested.

[0096] Comparative Example 4

[0097] The lithium supplement additive Li5FeO4 and the phosphate positive electrode main material LiMn 0.7 Fe 0.3 A composite positive electrode slurry was prepared using PO4, conductive agent Super P, and binder PVDF. The slurry was used to coat the positive electrode sheet, which was then used to make a lithium-ion battery with the negative electrode sheet. After the battery was activated with a high voltage of 4.2V to 4.8V, the cycle performance of the lithium-ion battery was tested.

[0098] Comparative Example 5

[0099] A composite positive electrode slurry was prepared by combining the lithium supplement additive 0.7Li2MnO3·0.3LiMgO2, the phosphate positive electrode main material LiFePO4, the conductive agent Super P, and the binder PVDF. The slurry was used to coat the positive electrode sheet, which was then used to make a lithium-ion battery with the negative electrode sheet. After the battery was activated with a high voltage of 4.2V~4.8V, the cycle performance of the lithium-ion battery was tested.

[0100] Comparative Example 6

[0101] The lithium supplement additive 0.7Li2MnO3·0.3LiMgO2, the phosphate positive electrode main material LiMn 0.7 Fe 0.3 A composite positive electrode slurry was prepared using PO4, conductive agent Super P, and binder PVDF. The slurry was used to coat the positive electrode sheet, which was then used to make a lithium-ion battery with the negative electrode sheet. After the battery was activated with a high voltage of 4.2V to 4.8V, the cycle performance of the lithium-ion battery was tested.

[0102] It should be noted that the specific parameters or some commonly used reagents in the above embodiments are specific embodiments or preferred embodiments under the conception of this application, and are not intended to limit them; those skilled in the art may make adaptive adjustments within the conception and protection scope of this application.

[0103] Test Case

[0104] The lithium ion batteries prepared in the above examples and comparative examples were subjected to the following tests:

[0105] Cyclic performance test method:

[0106] First, charge to 4.6V at a constant current of 0.1C, then discharge to 2.5V at a constant current of 0.1C, then charge to 4.2V at a constant current and constant voltage of 0.5C, with a cut-off current of 0.02C. After standing for 1 hour, discharge to 2.5V at a constant current of 0.5C, and then repeat the charge and discharge cycle at 2.5-4.2V for 500 times.

[0107] Surface alkalinity test method:

[0108] First, the material was heated to 1023K under a vacuum of 0.01pa and then heat treated for 2h to fully decompose Li2CO3 and LiOH on the material surface to produce Li2O. Then, CO2 was used as the acidic adsorption molecule at 423K, and the adsorption amount of CO2 was tested using a heat flow micro-adsorption calorimeter. The adsorption amount was recorded as the surface alkalinity.

[0109] pH test method:

[0110] 1. Place a 100mL beaker on an electronic balance, remove the tares, weigh 5.00g of the lithium supplement additive sample into the beaker with a spoon, add a stirrer, add 50.00g of pure water, and seal with parafilm;

[0111] 2. Set the magnetic stirrer to 450 rpm and stir for 5 minutes. After stirring, filter with quantitative rapid filter paper and take the filtrate for testing.

[0112] 3. Turn on the pH meter, immerse the electrode in the uniform sample solution, and read and record the sample pH result.

[0113] Residual lithium content test method:

[0114] 1. Fill a clean 250 mL Erlenmeyer flask with 250 mL of pure water and seal the flask with a sealing film. Place the sealed Erlenmeyer flask in a biochemical incubator at 25°C for 12 hours.

[0115] 2. Weigh 5.0g of lithium supplement sample onto weighing paper, transfer the weighed sample to a 250mL beaker, and record the sample mass m1; place a magnetic stir bar in the beaker; immediately remove pure water from the biochemical incubator, weigh approximately 100g of pure water into the beaker, and record the pure water mass m2, then seal with parafilm;

[0116] 3. Immediately place the beaker on a magnetic stirrer and stir at 600 rpm for 5 minutes. After stirring, filter the solution within 2 minutes until there is no obvious solution on the filter membrane. Obtain the filtrate and record the mass of the filtrate m3.

[0117] 4. Use 0.1 mol / L dilute hydrochloric acid as the titrant to perform automatic potentiometric titration on the filtrate. As the dilute hydrochloric acid is added, the pH of the solution gradually decreases. When the pH is 6.5-9, the automatic potentiometric titrator will show an electrode potential jump point EP1. When the pH is 3.5-5.5, the automatic potentiometric titrator will show another electrode potential jump point EP2, which is the titration endpoint. The residual lithium content (%) is calculated as follows:

[0118] Table 1 Comparison of electrochemical performance of batteries in different embodiments

[0119] Note: The surface alkalinity, residual lithium content and pH values ​​in Table 1 are the results obtained by measuring the lithium supplement additive.

[0120] It is well known in the art that the lower the first coulombic efficiency, the more lithium is replenished in the first cycle, the better the lithium replenishment effect, and the higher the capacity retention rate indicates that the active lithium loss of the phosphate positive electrode main material is lower and the lithium replenishment effect is better.

[0121] Therefore, as shown in the table above, according to Examples 1-4 and Comparative Example 1, the addition of the lithium-supplementing additive provided by the present application in the examples effectively improves the capacity retention rate of the lithium-ion battery. According to Example 5, it can be known that the lithium-supplementing additive provided by the present application can be applied to a variety of positive electrode materials to improve their cycle performance; according to Examples 6-15, it can be known that the surface layer of the lithium-supplementing additive material provided by the present application can be doped with M elements and N elements to effectively inhibit the dissolution of Fe and Mn elements in the bulk phase, and avoid the destruction of SEI film after the dissolution of Fe and Mn elements, thereby improving structural stability and improving cycle performance. According to the effects of the examples and comparative examples 3-6, the lithium-containing compound in the lithium-supplementing additive provided by the present application is LiFe α Mn β M 1-α-β O 2-γ X γ and Li2Fe δ Mn ε N 1-δ-ε O 3-η X η Two phases, the lithium-rich phase Li2Fe δ Mn ε N 1-δ-ε O 3-η X η During the first charge at high voltage, due to irreversible oxygen release and Fe 3+ / Fe 4+ The unique controllable redox reversibility makes its initial coulombic efficiency low, which can provide more active lithium required for the negative electrode; while LiFeα Mn β M 1-α-β O 2-γ X γ Phase due to Fe 3+ / Fe 4+ The unique controllable redox reversibility can provide more reversible capacity while providing part of the active lithium required for the negative electrode, and can also stabilize the lithium-rich phase structure. The combination of the two can not only achieve a good lithium replenishment effect, but the material itself can also contribute capacity in subsequent cycles, which can reduce the reduction in energy density caused by the introduction of additives.

[0122] Moreover, as shown in the table above, according to the examples and comparative examples 3-6, it can be seen that the lithium supplement additive provided by the present application has an extremely low residual lithium content on its surface due to the ratio of the elements of the material itself and the special two-phase structure, which is 2 orders of magnitude lower than that of comparative examples 3 and 4, and 1 order of magnitude lower than that of comparative examples 5 and 6. In addition, from the pH value measured by the lithium supplement additive, the pH value of the lithium supplement additive of the present application is generally lower than 12, while the pH measurement values ​​of the lithium supplement materials of comparative examples 3 and 4 are too high, exceeding the pH value. Within the measurement range of the measuring equipment, the pH values ​​of Comparative Examples 5 and 6 are also above 12, and the high pH value and residual lithium content of the lithium supplement additive will cause the material to easily absorb water, resulting in poor stability of the slurry, causing the viscosity of the slurry to fluctuate greatly and even become jelly-like, resulting in poor fluidity, which will cause large fluctuations in the coating surface density and even cracking of the electrode during drying due to the poor fluidity of the slurry; in addition, the prepared electrode will also easily absorb water and be difficult to dry, and then after injection, the water will react with the electrolyte, deteriorating the electrochemical performance of the battery.

Claims

1. A lithium supplement additive, comprising a lithium-containing compound, wherein the lithium-containing compound is selected from one or more combinations of compounds represented by chemical formula (I): in, The M element and the N element are each independently selected from one or more of Zr, Co, Sr, Al, Ni, W, Ti, Cu, Mg, Zn, Ca, Ba, Sc, Ga, Y, La, In, Ce, Ge, Hf, Sn, Nb, Ta, V, and Sb; the X is an F element, and 0.4≤a≤0.9, 0<α≤1, 0≤β≤1, 0<α+β≤1, 0≤γ≤0.1, 0<δ≤1, 0≤ε≤1, 0<δ+ε≤1, and 0≤η≤0.1; The surface basicity of the lithium supplement additive is 10 to 400 μmol·g -1 .

2. The lithium supplement additive according to claim 1, wherein In the chemical formula (I), 0<β≤1, 0<ε≤1.

3. The lithium supplement additive according to claim 1, wherein In the chemical formula (I), 0<γ≤0.1, 0<η≤0.

1.

4. The lithium supplement additive according to any one of claims 1 to 3, wherein: In the chemical formula (I), 0<α+β<1, 0<δ+ε<1.

5. The lithium supplement additive according to claim 1, wherein: The lithium-containing compound is 0.8LiFe 0.42 Mn 0.58 O2·0.2Li2Fe 0.6 Mn 0.4 O3, 0.6LiFe 0.68 Mn 0.31 Al 0.01 O2·0.4Li2Fe 0.45 Mn 0.54 Al 0.01 O3.、0.7LiFe 0.55 Mn 0.43 Co 0.02 O 1.95 F 0.05 0.3Li2Fe 0.33 Mn 0.65 Co 0.02 O 2.95 A combination of one or more of F0.

05.

6. The lithium supplement additive according to claim 1, wherein: The volume average particle size D of the lithium-containing compound V 50 is 500nm-8μm; and / or the specific surface area of ​​the lithium-containing compound is 0.5 to 20 m 2 / g.

7. The lithium supplement additive according to claim 1, wherein: The lithium supplement additive further includes a coating located on at least a portion of the surface of the lithium-containing compound, and the coating contains carbon.

8. The lithium supplement additive according to claim 7, wherein: The carbon in the coating is derived from a carbon source, and the carbon source includes at least one of starch, glucose, sucrose, polyethylene glycol, polyvinyl alcohol, and cyclodextrin.

9. The lithium supplement additive according to claim 7, wherein: The carbon coating amount on the surface of the lithium-containing compound is 5000-50000ppm; And / or the thickness of the coating is 2 to 5 nm.

10. The lithium supplement additive according to claim 1 or 7, wherein: The residual lithium content of the lithium supplement additive is 200ppm-4000ppm; And / or the pH of the lithium supplement additive is 10-12.

11. A method for preparing a lithium supplement additive, comprising the following steps: The precursor material is prepared by spray pyrolysis; The precursor material is mixed with a lithium source and calcined to obtain a lithium-containing compound; The lithium supplement additive comprises a lithium-containing compound, and the lithium-containing compound is selected from one or more combinations of compounds represented by chemical formula (I): in, The M element and the N element are each independently selected from one or more of Zr, Co, Sr, Al, Ni, W, Ti, Cu, Mg, Zn, Ca, Ba, Sc, Ga, Y, La, In, Ce, Ge, Hf, Sn, Nb, Ta, V, and Sb; the X is an F element, and 0.4≤a≤0.9, 0<α≤1, 0≤β≤1, 0<α+β≤1, 0≤γ≤0.1, 0<δ≤1, 0≤ε≤1, 0<δ+ε≤1, and 0≤η≤0.

1.

12. The method for preparing the lithium supplement additive according to claim 11, wherein: The preparation method of the precursor material comprises: According to the stoichiometric ratio in the chemical formula (I), the iron source, the manganese source, the M source, the N source, and the X source are dissolved and mixed with deionized water, and a nucleating agent is added to obtain a mixed solution; The mixed solution is spray-pyrolyzed to form a precursor material.

13. The method for preparing the lithium supplement additive according to claim 12, wherein: In the chemical formula (I), 0<β≤1, 0<ε≤1, and the concentration of manganese ions in the mixed solution is 0.01-2 mol / L.

14. The method for preparing the lithium supplement additive according to claim 11, wherein: The molar ratio of the precursor material to the lithium source is 1:1.1 to 1:1.

6.

15. The method for preparing the lithium supplement additive according to claim 11, further comprising the following steps: The carbon source is added to form a carbon-containing coating on the surface of the lithium-containing compound.

16. The method for preparing the lithium supplement additive according to claim 15, wherein: The method for preparing the carbon coating comprises: mixing the lithium-containing compound with a carbon source, and then performing high-temperature heat treatment under a protective atmosphere.

17. The method for preparing the lithium supplement additive according to claim 15, wherein: The mass ratio of the lithium supplement additive to the carbon source is 1:(0.005-0.05). 18 . A positive electrode material comprising a positive electrode active material and the lithium supplement additive according to claim 1 .

19. A positive electrode sheet, comprising the positive electrode material according to claim 18.

20. A battery comprising the positive electrode sheet according to claim 19.

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