Composite lithium-supplementing agent material, preparation method therefor, positive electrode sheet, and battery

Abstract

A composite lithium-supplementing agent material, a preparation method therefor, a positive electrode sheet, and a battery. The composite lithium-supplementing agent material comprises an inner core and a coating layer, wherein the inner core comprises a lithium-supplementing material, and the coating layer comprises Mo 2N.

Description

Composite lithium supplement material and preparation method thereof, positive electrode sheet, and battery

[0001] This application claims priority to the Chinese patent application filed with the China Patent Office on September 13, 2023, with application number 202311179185.2. The entire contents of the above application are incorporated by reference into this application. Technical Field

[0002] The present application relates to the field of positive electrode lithium replenishment technology, and in particular to a composite lithium replenisher material and a preparation method thereof, a positive electrode sheet, and a battery. Background Art

[0003] During the first charge of a lithium-ion battery, the negative electrode material permanently consumes more active Li from the positive electrode. + , forming an SEI film on the surface of the negative electrode, which reduces the capacity and energy density of the lithium-ion battery. To compensate for the lithium consumed in forming the SEI film, lithium replenishment technology can be used in lithium-ion batteries. Compared with negative electrode lithium replenishment, positive electrode lithium replenishment can directly add positive electrode lithium replenishment materials into the positive electrode slurry, without the need for additional process improvements, and the cost is relatively low.

[0004] Related technologies disclose a composite lithium-replenishing additive and a method for replenishing lithium in a lithium-ion battery positive electrode. The composite lithium-replenishing additive is composed of a core lithium-replenishing compound and an outer phosphorus-containing compound. The lithium-replenishing compound is selected from one or more of Li5FeO4, Li5Fe5O8, Li6CoO4, Li2NiO2, Li2O, and Li2O2, and the phosphorus-containing compound is selected from one or more of phosphates, phosphites, alkylphosphonates, and their phenyl, halogen, and thienyl substitutions. The lithium-replenishing method comprises mixing a positive electrode active material, a binder, and the composite lithium-replenishing additive in a solvent to prepare a slurry; uniformly coating the slurry on the surface of a current collector, and drying to obtain a lithium-replenishing positive electrode material. In the lithium-replenishing method, oxygen generated during the first cycle of charging can be absorbed by the phosphorus-containing compound and form a uniform coating on the surface of the positive electrode particles, thereby solving the problem of gas production during lithium replenishment and improving the cycle stability of the battery.

[0005] There are many types of positive electrode lithium supplements, among which Li5FeO4 has attracted widespread attention due to its good compatibility with battery systems, low production cost, non-toxicity, and high specific capacity. However, Li5FeO4 easily reacts chemically with carbon dioxide and water in the air, forming lithium carbonate and carbon dioxide on its surface. As a result, Li5FeO4 is highly susceptible to deterioration in air. Furthermore, Li5FeO4 has very low electrical conductivity, making it almost an insulating compound. Furthermore, Li5FeO4 has a high decomposition potential, requiring a high potential during the initial charge cycle to fully release its capacity, and high voltages can easily lead to electrolyte decomposition.

[0006] Therefore, in order to achieve better lithium replenishment effects, it is urgent to develop a lithium replenishment material with low decomposition potential, stability in air and good conductivity. Technical issues

[0007] The present application provides a composite lithium supplement material and a preparation method thereof, as well as a positive electrode plate and a battery to solve the above technical problems. Technical Solutions

[0008] In order to solve the above technical problems, the present application provides a composite lithium supplement material and a preparation method thereof.

[0009] The positive electrode and battery utilize a uniform Mo2N2 shell structure formed in situ on the outer surface of the lithium-replenishing material, preventing direct contact between the material and air and improving its stability in air. Furthermore, Mo2N2, as a typical interstitial metal compound, forms Mo-N bonds with Mo atoms, exhibiting metal-like high conductivity, effectively improving the material's electrical conductivity. Furthermore, Mo2N2 has a catalytic effect, catalyzing the release of active lithium ions from the lithium-replenishing material at a lower potential, reducing the battery's initial charge voltage, minimizing the impact on the electrolyte, and reducing gas production.

[0010] To achieve this goal, this application adopts the following technical solutions:

[0011] In a first aspect, the present application provides a composite lithium supplement material, comprising a core and a coating layer; the core comprises a lithium supplement material, and the coating layer comprises Mo2N.

[0012] Optionally, the lithium supplement material includes any one or a combination of at least two of Li5FeO4, Li6CoO4, LiF or Li3N. Typical but non-limiting combinations include a combination of Li5FeO4 and Li6CoO4, a combination of Li6CoO4 and LiF, a combination of LiF and Li3N, a combination of Li5FeO4, Li6CoO4 and LiF, a combination of Li6CoO4, LiF and Li3N, preferably Li5FeO4.

[0013] Optionally, the mass of the lithium supplement material is 90wt% to the total mass of the composite lithium supplement material.

[0014] 95wt%, for example, can be 90wt%, 91wt%, 92wt%, 93wt%, 94wt% or 95wt%, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0015] In this application, if the amount of lithium-supplementing material added is too much, the coating layer material is insufficient, the formed coating layer is incomplete, and the coating layer cannot fully function, which has limited performance improvement on the lithium-supplementing agent. If the amount of lithium-supplementing material added is too little, the coating layer material is excessive, and because the coating layer does not provide active lithium ions, the charge capacity of the composite lithium-supplementing agent is reduced. Preferably, the mass of the coating layer material is 5-10wt% of the total mass of the composite lithium-supplementing agent material, for example, it can be 5wt%, 6wt%, 7wt%, 8wt%, 9wt%, or 10wt%, but is not limited to the listed values, and other values ​​within the numerical range not listed are also applicable.

[0016] In this application, if the coating layer's mass percentage is too high, the coating layer material is relatively high. Because the coating layer does not provide active lithium ions, the charge capacity of the composite lithium supplement is reduced. If the coating layer's mass percentage is too low, the coating layer is incomplete and cannot fully function, resulting in limited improvement in the performance of the lithium supplement.

[0017] Optionally, the thickness of the coating layer is 0.5µm~1µm, wherein the thickness can be 0.5µm, 0.6µm, 0.7µm, 0.8µm, 0.9µm or 1µm, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0018] In this application, if the coating layer is too thick, the charge capacity of the composite lithium supplement is reduced because the coating layer does not provide active lithium ions. If the coating layer is too thin, the coating layer is not fully formed and cannot fully function, resulting in limited improvement in the performance of the lithium supplement.

[0019] In a second aspect, the present application provides a method for preparing the composite lithium supplement material according to the first aspect, the preparation method comprising:

[0020] (1) preparing the kernel;

[0021] (2) mixing the molybdenum source and the obtained core, and sintering the mixture to obtain the composite lithium supplement material.

[0022] Optionally, when the core is a lithium supplement material Li5FeO4, the preparation method thereof includes:

[0023] (a) mixing an iron source and a precipitant, reacting, and then drying to obtain an intermediate precursor;

[0024] (b) mixing a lithium source and the intermediate precursor, and sintering the mixture under a protective atmosphere to obtain the core.

[0025] Optionally, the iron source in step (a) comprises any one or a combination of at least two of ferric sulfate, ferric chloride or ferric nitrate. Typical but non-limiting combinations include a combination of ferric sulfate and ferric chloride, a combination of ferric chloride and ferric nitrate, a combination of ferric sulfate and ferric nitrate, and a combination of ferric sulfate, ferric chloride and ferric nitrate.

[0026] Optionally, the precipitant in step (a) includes sodium hydroxide and / or potassium hydroxide.

[0027] Optionally, the molar ratio of the iron source to the precipitant in step (a) is 1:(2-4), for example, 1:2, 1:3 or 1:4, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0028] Optionally, the pH of the precipitant in step (a) is 9 to 13, for example, 9, 10, 11, 12 or 13, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0029] Optionally, the reaction temperature in step (a) is 20°C to 70°C, for example, 20°C, 30°C, 40°C, 50°C, 60°C or 70°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0030] Optionally, the reaction time of step (a) is 3 h to 8 h, for example, 3 h, 4 h, 5 h, 6 h, 7 h or 8 h, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0031] Optionally, the reaction in step (a) further comprises washing to neutrality.

[0032] Optionally, the drying temperature in step (a) is 80°C to 100°C, for example, 80°C, 85°C, 90°C, 95°C or 100°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0033] Optionally, the drying time in step (a) is 20 h to 30 h, for example, 20 h, 22 h, 24 h, 26 h, 28 h or 30 h, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0034] Optionally, the lithium source in step (b) includes any one or a combination of at least two of lithium hydroxide, lithium carbonate or lithium oxide. Typical but non-limiting combinations include a combination of lithium hydroxide and lithium carbonate, a combination of lithium hydroxide and lithium oxide, a combination of lithium carbonate and lithium oxide, and a combination of lithium hydroxide, lithium carbonate and lithium oxide.

[0035] Optionally, the molar ratio of the lithium source and the intermediate precursor in step (b) is (5~11):2, wherein the molar ratio can be 5:2, 6:2, 7:2, 8:2, 9:2, 10:2 or 11:2, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0036] Optionally, the protective atmosphere in step (b) comprises any one or a combination of at least two of a nitrogen atmosphere, a helium atmosphere or an argon atmosphere. Typical but non-limiting combinations include a combination of a nitrogen atmosphere and a helium atmosphere, a combination of a nitrogen atmosphere and an argon atmosphere, a combination of a helium atmosphere and an argon atmosphere, and a combination of a nitrogen atmosphere, a helium atmosphere and an argon atmosphere.

[0037] Optionally, the sintering temperature in step (b) is 600°C to 1000°C, for example, 600°C, 700°C, 800°C, 900°C or 1000°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0038] Optionally, the sintering time in step (b) is 8 h to 15 h, for example, 8 h, 10 h, 12 h, 14 h or 15 h, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0039] Optionally, the molybdenum source in step (2) includes Mo, MoO2, MoCl5, MoO3 or (NH4)6Mo7O 24 ∙Any one or a combination of at least two of 4H2O, typical but non-limiting combinations include the combination of Mo and MoO2, the combination of MoO2 and MoCl5, the combination of MoCl5 and MoO3, the combination of MoO3 and (NH4)6Mo7O 24 ∙ Combination of 4H2O, combination of Mo, MoO2 and MoCl5, combination of MoO2, MoCl5 and MoO3, combination of MoCl5, MoO3 and (NH4)6Mo7O 24 ∙ Combinations of 4H2O, Mo, MoO2, MoCl5, and MoO3, MoO2, MoCl5, MoO3, and (NH4)6Mo7O 24 ∙4H2O combination.

[0040] Optionally, the sintering in step (2) is carried out in a mixed gas atmosphere.

[0041] Optionally, the mixed gas includes hydrogen and nitrogen or hydrogen and ammonia.

[0042] Optionally, the sintering temperature in step (2) is 400°C to 900°C, for example, 400°C, 500°C, 600°C, 700°C, 800°C or 900°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0043] Optionally, the sintering time in step (2) is 10 h to 40 h, for example, 10 h, 15 h, 20 h, 30 h or 40 h, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0044] As a preferred technical solution of the preparation method described in the second aspect of the present application, the preparation method comprises:

[0045] (1) Prepare the kernel as follows:

[0046] a. Mix the iron source and a precipitant with a pH of 9 to 13, react at 20°C to 70°C for 3 to 8 hours, filter and wash until the pH is neutral, and then dry at 80°C to 100°C for 20 to 30 hours to obtain an intermediate precursor;

[0047] b mixed lithium source and the resulting intermediate precursor, sintered at a temperature of 600 ℃ ~ 1000 ℃ under a protective atmosphere for 8h ~ 15h to obtain the core;

[0048] (2) mixing the molybdenum source and the obtained core, and sintering them at a temperature of 400° C. to 900° C. for 10 h to 40 h in a hydrogen-nitrogen and / or hydrogen-ammonia atmosphere to obtain the composite lithium supplement material;

[0049] The iron source includes any one of ferric sulfate, ferric chloride or ferric nitrate, or a combination of at least two of them; the precipitant includes sodium hydroxide or potassium hydroxide; the lithium source includes any one of lithium hydroxide, lithium carbonate or lithium oxide, or a combination of at least two of them; the protective atmosphere includes any one of nitrogen atmosphere, helium atmosphere or argon atmosphere, or a combination of at least two of them; the molybdenum source includes Mo, MoO2, MoCl5, MoO3 or (NH4)6Mo7O 24 ∙ Any one or a combination of at least two of 4H2O.

[0050] This application effectively improves the air stability and conductivity of the Li5FeO4 material through a single in-situ coating, while reducing its decomposition voltage.

[0051] In a third aspect, the present application provides a positive electrode plate, wherein the positive electrode plate contains the composite lithium supplement material as described in the first aspect.

[0052] In a fourth aspect, the present application provides a battery, wherein the battery contains the composite lithium supplement material as described in the first aspect or the positive electrode sheet as described in the third aspect. Beneficial effects

[0053] The beneficial effects of this application are:

[0054] The composite lithium-replenishing material provided herein forms a uniform Mo2N shell structure in situ on the outer surface of the lithium-replenishing material, preventing direct contact between the lithium-replenishing material and air, thereby improving its stability in air. Furthermore, because Mo2N, a typical interstitial metal compound, forms Mo-N bonds with Mo atoms, it exhibits high metal-like conductivity, effectively improving the material's electrical conductivity. Furthermore, Mo2N has a catalytic effect, catalyzing the release of active lithium ions from the lithium-replenishing material at a lower potential, thereby reducing the battery's initial charge voltage, minimizing the impact on the electrolyte, and reducing gas production. The button battery assembled with composite lithium-supplementing materials and metallic lithium can be charged to 4.2V at a constant current of 0.1C and then charged to 0.05C at a constant voltage. The charging capacity can reach more than 640 mAh / g. It can be charged to 4.2V at a constant current of 0.5C and then charged to 0.05C at a constant voltage. The charging capacity can reach more than 625 mAh / g. It can be charged to 3.8V at a constant current of 0.1C and then charged to 0.05C at a constant voltage. The charging capacity can reach more than 621 mAh / g. Modes for Carrying Out the Invention

[0055] The technical solution of the present application is further described below through specific implementation methods. Those skilled in the art should understand that the embodiments are only used to help understand the present application and should not be regarded as specific limitations of the present application.

[0056] Example 1

[0057] This embodiment provides a composite lithium supplement material, which includes a core and a coating layer; the core is Li5FeO4, with a mass of 92wt% of the composite lithium supplement material; the coating layer is Mo2N, with a mass of 8wt% of the composite lithium supplement material; and the thickness of the coating layer is 0.8µm.

[0058] The preparation method of the composite lithium supplement material comprises:

[0059] (1) Prepare the kernel as follows:

[0060] a. Press Fe 3+ :OH -1 =1:3 molar ratio of ferric sulfate solution and sodium hydroxide solution with a pH of 10 were mixed, reacted at 50 ° C for 5 hours, filtered and washed until the pH was neutral, and then dried at 90 ° C for 25 hours to obtain an intermediate precursor;

[0061] b. mixing lithium hydroxide and the obtained intermediate precursor in a molar ratio of 8:2 and sintering at a temperature of 800 ° C for 12 h under a nitrogen atmosphere to obtain the core;

[0062] (2) MoO2 and the obtained core are mixed and sintered at a temperature of 600°C for 25 hours in a hydrogen and nitrogen atmosphere to obtain the composite lithium supplement material.

[0063] Example 2

[0064] This embodiment provides a composite lithium supplement material, which includes a core and a coating layer; the core is Li5FeO4, with a mass of 90wt% of the composite lithium supplement material; the coating layer is Mo2N, with a mass of 10wt% of the composite lithium supplement material; and the thickness of the coating layer is 1µm.

[0065] The preparation method of the composite lithium supplement material comprises:

[0066] (1) Prepare the kernel as follows:

[0067] a. Press Fe 3+ :OH -1 =1:2 molar ratio of ferric sulfate solution and potassium hydroxide solution with a pH of 9 were mixed, reacted at 20 ° C for 8 hours, filtered and washed until the pH was neutral, and then dried at 80 ° C for 30 hours to obtain an intermediate precursor;

[0068] b mixing a molar ratio of 5:2 of lithium carbonate and the obtained intermediate precursor, and sintering at a temperature of 600 ° C for 15h in a helium atmosphere to obtain the core;

[0069] (2) MoCl5 and the obtained core are mixed and sintered at a temperature of 400°C for 40 hours in a hydrogen and ammonia atmosphere to obtain the composite lithium supplement material.

[0070] Example 3

[0071] This embodiment provides a composite lithium supplement material, which includes a core and a coating layer; the core is Li5FeO4, with a mass of 95wt% of the composite lithium supplement material; the coating layer is Mo2N, with a mass of 5wt% of the composite lithium supplement material; and the thickness of the coating layer is 0.5µm.

[0072] The preparation method of the composite lithium supplement material comprises:

[0073] (1) Prepare the kernel as follows:

[0074] a. Press Fe 3+ :OH -1=1:4 molar ratio of ferric sulfate solution and sodium hydroxide solution with a pH of 13 were mixed, reacted at 70 ° C for 3 hours, filtered and washed until the pH was neutral, and then dried at 100 ° C for 20 hours to obtain an intermediate precursor;

[0075] b. mixing lithium oxide and the obtained intermediate precursor in a molar ratio of 11:2 and sintering at a temperature of 1000 ° C for 8 h under an argon atmosphere to obtain the core;

[0076] (2) Mixed (NH4)6Mo7O 24 ∙4H2O and the obtained core are sintered at a temperature of 900°C for 10 hours in a hydrogen and nitrogen atmosphere to obtain the composite lithium supplement material.

[0077] Example 4

[0078] In this embodiment, except that 92wt% of Li5FeO4 and 8wt% of Mo2N of the composite lithium-supplementing material are replaced by 88wt% of Li5FeO4 and 12wt% of Mo2N of the composite lithium-supplementing material, other conditions are the same as those in Example 1.

[0079] Example 5

[0080] In this embodiment, except that Li5FeO4, which accounts for 92wt% of the mass fraction of the composite lithium-supplement material, and Mo2N, which accounts for 8wt% of the mass fraction of the composite lithium-supplement material, are replaced by Li5FeO4, which accounts for 98wt% of the mass fraction of the composite lithium-supplement material, and Mo2N, which accounts for 2wt% of the mass fraction of the composite lithium-supplement material, other conditions are the same as those in Example 1.

[0081] Example 6

[0082] In this embodiment, except that the thickness of the coating layer is changed to 1.2 μm, other conditions are the same as those in Example 1.

[0083] Example 7

[0084] In this embodiment, except that the thickness of the coating layer is changed to 0.3 μm, other conditions are the same as those in Example 1.

[0085] Comparative Example 1

[0086] This comparative example provides a lithium supplement material, which differs from Example 1 in that it does not contain a coating layer.

[0087] The above-mentioned lithium supplement material was added to the positive electrode plate, and the battery was assembled. The air stability, conductivity and charging voltage were tested. The test results are shown in Table 1.

[0088] The test method is as follows:

[0089] Air stability: The lithium supplement materials prepared in Examples 1-7 and Comparative Example 1 were left in air for 24 hours and then assembled with lithium metal into button cells for testing. The cells were charged at a constant current of 0.1C to 4.2V and then at a constant voltage of 0.05C. The charged gram capacity of the lithium supplement was calculated.

[0090] Conductivity: The lithium metal used as the lithium supplement material in Examples 1-7 and Comparative Example 1 was assembled into button cells for testing. The cells were charged to 4.2V at a constant current of 0.5C and then to 0.05C at a constant voltage. The charge capacity in grams of the lithium supplement was calculated.

[0091] Charging voltage: The lithium metal supplement materials prepared in Examples 1-7 and Comparative Example 1 were assembled into button cells for testing. They were charged at a constant current of 0.1C to 3.8V, and then charged at a constant voltage of 0.05C. The charging capacity in grams of the lithium supplement was calculated.

[0092] Table 1

[0093] Test No. Air Stability Charge Gram Capacity (mAh / g) Conductivity Charge Gram Capacity (mAh / g) Charging Voltage Charge Gram Capacity (mAh / g) Example 1 640 625 621 Example 2 624 61 1607 Example 3 51 859 3576 Example 4 480 580 550 Example 5 49 8460 454 Example 6 501 458 451 Example 7 48 357 5558 Comparative Example 1 30 255 6540

[0094] In summary, by comparing Example 1 with Examples 4-5, it can be seen that when the amount of Mo2N added is too much or too little, the air stability charge capacity, conductivity charge capacity, and charge voltage charge capacity of the battery are all reduced. When the mass proportion of the coating layer in this application is too high, the coating layer material is relatively large. Since the coating layer does not provide active lithium ions, the charge capacity of the composite lithium supplement is reduced. When the mass proportion of the coating layer is too low, the coating layer formed is not complete, the role of the coating layer cannot be fully exerted, and the performance improvement of the lithium supplement is limited.

[0095] A comparison of Example 1 and Examples 6-7 shows that when the coating layer is too thick or too thin, the battery's air stability charge capacity, conductivity charge capacity, and charge voltage charge capacity all decrease. When the coating layer is too thick, the charge capacity of the composite lithium supplement is reduced because the coating layer does not provide active lithium ions. When the coating layer is too thin, the formed coating is incomplete, unable to fully exert its function, and the performance improvement of the lithium supplement is limited.

[0096] Comparison of Examples 1-3 with Comparative Example 1 demonstrates that the composite lithium-replenishing agent material provided herein forms a uniform in-situ Mo2N shell structure on the outer surface of the lithium-replenishing material, preventing direct contact between the lithium-replenishing material and air, thereby improving its stability in air. Furthermore, since Mo2N, a typical interstitial metal compound, forms Mo-N bonds with Mo atoms, it exhibits high metal-like conductivity, effectively enhancing the material's electrical conductivity. Furthermore, Mo2N has a catalytic effect, enabling the lithium-replenishing material to release active lithium ions at a relatively low potential, thereby lowering the battery's initial charge voltage, minimizing the impact on the electrolyte, and reducing gas production.

Claims

1. A composite lithium supplement material, comprising a core and a coating layer; the core comprises a lithium supplement material, and the coating layer comprises Mo2N.

2. The composite lithium supplement material according to claim 1, wherein: The lithium supplement material includes any one of Li5FeO4, Li6CoO4, LiF or Li3N or a combination of at least two thereof, preferably Li5FeO4; Wherein, the mass of the lithium supplement material is 90wt%~95wt% of the total mass of the composite lithium supplement material; Wherein, the mass of the coating layer material is 5wt%~10wt% of the total mass of the composite lithium supplement material; Wherein, the thickness of the coating layer is 0.5µm~1µm.

3. The method for preparing the composite lithium supplement material according to claim 1 or 2, the method comprising: (1) preparing the kernel; (2) Mixing the molybdenum source and the obtained core, and sintering them to obtain the composite lithium supplement material.

4. The preparation method according to claim 3, wherein When the core is a lithium supplement material Li5FeO4, the preparation method comprises: (a) mixing an iron source and a precipitant, reacting and then drying to obtain an intermediate precursor; (b) mixing a lithium source and the intermediate precursor, and sintering the mixture under a protective atmosphere to obtain the core.

5. The preparation method according to claim 4, wherein the iron source in step (a) comprises any one of ferric sulfate, ferric chloride or ferric nitrate, or a combination of at least two thereof; in, The precipitating agent in step (a) comprises sodium hydroxide and potassium hydroxide; Wherein, the molar ratio of the iron source to the precipitant in step (a) is 1:(2-4); Wherein, the pH of the precipitant in step (a) is 9 to 13; Wherein, the reaction temperature in step (a) is 20°C to 70°C; Wherein, the reaction time of step (a) is 3h~8h; Wherein, after the reaction in step (a), washing to neutrality is also included; Wherein, the drying temperature in step (a) is 80°C to 100°C; Wherein, the drying time in step (a) is 20h~30h.

6. The preparation method according to claim 4 or 5, wherein the lithium source in step (b) comprises any one of lithium hydroxide, lithium carbonate or lithium oxide, or a combination of at least two thereof; in, The molar ratio of the lithium source to the intermediate precursor in step (b) is (5-11):2; Wherein, the protective atmosphere in step (b) comprises any one of a nitrogen atmosphere, a helium atmosphere or an argon atmosphere, or a combination of at least two thereof; Wherein, the sintering temperature in step (b) is 600°C to 1000°C; Wherein, the sintering time in step (b) is 8h~15h.

7. The preparation method according to any one of claims 3 to 6, wherein the molybdenum source in step (2) comprises Mo, MoO2, MoCl5, MoO3 or (NH4)6Mo7O 24 ∙Any one or a combination of at least two of 4H2O; in, The sintering in step (2) is carried out in a mixed gas atmosphere; Wherein, the mixed gas includes hydrogen-nitrogen or hydrogen-ammonia; Wherein, the sintering temperature in step (2) is 400°C to 900°C; Wherein, the sintering time in step (2) is 10h~40h.

8. The preparation method according to any one of claims 3 to 7, comprising: (1) Prepare the kernel as follows: a. Mix the iron source and the precipitant with a pH of 9 to 13, react at 20°C to 70°C for 3h to 8h, filter and wash until the pH is neutral, and then dry at 80°C to 100°C for 20h to 30h to obtain an intermediate precursor; b. mixing the lithium source and the intermediate precursor obtained, and sintering at a temperature of 600°C to 1000°C under a protective atmosphere for 8h to 15h to obtain the core; (2) mixing the molybdenum source and the obtained core, and sintering them at a temperature of 400° C. to 900° C. for 10 h to 40 h in a hydrogen-nitrogen atmosphere or a hydrogen-ammonia atmosphere to obtain the composite lithium supplement material; The iron source includes any one of ferric sulfate, ferric chloride or ferric nitrate or a combination of at least two thereof; the precipitant includes sodium hydroxide or potassium hydroxide; the lithium source includes any one of lithium hydroxide, lithium carbonate or lithium oxide or a combination of at least two thereof; the protective atmosphere includes any one of nitrogen atmosphere, helium atmosphere or argon atmosphere or a combination of at least two thereof; the molybdenum source includes Mo, MoO2, MoCl5, MoO3 or (NH4)6Mo7O 24 ∙ Any one or a combination of at least two of 4H2O. 9 . A positive electrode sheet, comprising the composite lithium supplement material according to claim 1 or 2. 10 . A battery, comprising the composite lithium supplement material according to claim 1 or 2 or the positive electrode sheet according to claim 9 .