A lithium supplement intermediate and its preparation method and application

Abstract

The present invention provides a lithium supplement intermediate and its preparation method and application. The chemical formula of the lithium supplement intermediate is Li 5+ x FeO 4‑(m / 2) ·(OH) m , wherein 1.95≤m≤3.27, 0.05≤x≤0.55. The lithium supplement agent intermediate provided by the present invention includes an appropriate amount of hydroxide. When preparing the lithium supplement agent using this intermediate, the generation of water vapor during the subsequent sintering process can be regulated and the uniformity of the material reaction can be optimized, thereby obtaining a lithium supplement agent with uniform material and high phase purity.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium-ion batteries, in particular to a lithium supplement agent, and in particular to a lithium supplement agent intermediate and a preparation method and application thereof. Background Art

[0002] In the application of lithium-ion batteries, during the first charge and discharge, the electrolyte will decompose on the surface of the negative electrode, and the products will be deposited on the surface to form a SEI film. This process will consume the active lithium of the positive electrode, resulting in a decrease in the coulombic efficiency of the first cycle, which in turn affects the capacity and energy density of the lithium battery. To solve this problem, lithium compensation technology has emerged. Among them, Li5FeO4 has attracted widespread attention due to its ultra-high theoretical capacity. During the first charge, Li5FeO4 can theoretically deintercalate 4 Li + It is used to compensate for the loss of negative electrode lithium, and its actual capacity is about 700mAh / g. Due to its ultra-high lithium replenishment capacity, low cost and environmental friendliness, it has become one of the most promising positive electrode lithium replenishment materials.

[0003] However, the existing Li5FeO4 production process often uses lithium oxide and iron oxide in a high-temperature solid-phase reaction. However, lithium oxide is expensive and easily absorbs water. Furthermore, the resulting lithium-rich ferrite has a high pH, ​​high residual alkalinity, and low capacity, making it difficult to scale up. Using other lithium salts for the synthesis of lithium-rich ferrite presents stringent process requirements, impure synthetic materials, and uneven element distribution.

[0004] CN116986890A discloses a method for preparing Li5FeO4 material, which simplifies multiple steps such as atomization-precipitation-thermal decomposition into a continuous, rapid, and easily controllable process, avoiding the introduction of impurities and destruction of the crystal structure during the production process. Not only is the particle size and morphology of the product controllable, but the composition is also uniform, the purity is high, and the production cost is low.

[0005] CN117735616A discloses a mixed coated Li5FeO4 material, in which the core is Li5FeO4, the main material of the mixed coating layer is a mixed carbon film material, and the filling coating material is LiF. This mixed coating layer can isolate water and CO2 in the air, improve the air stability of the material, and suppress the problem of increased surface residual alkali during material storage, transportation, pulping, etc.

[0006] CN117219761A discloses a composite lithium supplement Li5FeO4@Li2CO3 and its preparation method. By coheating a mixed gas containing CO2 with Li5FeO4 in a tubular furnace, a Li2CO3 coating with good stability is in situ generated on the surface of Li5FeO4, which can effectively protect Li5FeO4 from environmental influences, thereby improving the environmental stability of the material.

[0007] In the existing technology, only the effects of water or CO2 in the air on the stability of Li5FeO4 are considered. Therefore, impurities in the air are isolated by simply coating Li5FeO4, or the preparation process is complicated, making it difficult to achieve large-scale production. However, the effect of water vapor released from the raw materials during the preparation process on the structure of the prepared lithium supplement is not considered, making it difficult to prepare a uniform pure-phase lithium supplement.

[0008] Therefore, it is of great significance to provide a technical solution that has a simple preparation process and a low residual alkali content in the prepared lithium supplement. Summary of the Invention

[0009] In response to the shortcomings of the prior art, the present invention aims to provide a lithium supplement intermediate, its preparation method, and its application. The present invention provides a lithium supplement intermediate containing an appropriate amount of hydroxide. When used to prepare a lithium supplement, this intermediate can regulate the generation of water vapor during the subsequent sintering process and optimize the uniformity of the material reaction, thereby producing a lithium supplement with uniform material, high phase purity, low residual alkali content, and high capacity.

[0010] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

[0011] In the first aspect, the present invention provides a lithium supplement intermediate, the chemical formula of which is Li 5+ x FeO 4-(m / 2) ·(OH) m , where 1.95≤m≤3.27, 0.05≤x≤0.55.

[0012] The lithium supplement intermediate provided by the present invention has the chemical formula Li 5+x FeO 4-(m / 2) ·(OH) m , which contains an appropriate amount of hydroxide. During the subsequent preparation of the lithium supplement, the hydroxide in the hydroxide is released in the form of water vapor. By controlling the hydroxide content in the intermediate, the present invention can regulate the generation of water vapor during the subsequent sintering process during the subsequent preparation of the lithium supplement, optimize the uniformity of the material reaction, and thus obtain a lithium supplement with uniform material and high phase purity. In addition, the uniform material allows the lithium source and the iron source to fully react, and the prepared lithium supplement has a lower residual alkali component and a lower pH.

[0013] If the hydroxide content of the intermediate is too low, the subsequent water vapor release during the preparation of the lithium supplement will be low, resulting in an overly violent and uncontrollable reaction between the iron source and the lithium source, which will form a lithium supplement with large particle size variations, poor product particle size uniformity, and low capacity. If the hydroxide content of the intermediate is too high, the subsequent water vapor release during the preparation of the lithium supplement will affect the uniformity of the reaction and make it difficult to obtain a lithium supplement with high purity.

[0014] As a preferred technical solution of the present invention, the lithium supplement intermediate further includes a doping element, the mass of which accounts for 0.3%-1.0% of the total mass of the lithium supplement intermediate; the doping element includes any one of Zr, Al, W, Ti or Mg, or a combination of at least two of them.

[0015] In a second aspect, the present invention provides a method for preparing the lithium supplement intermediate as described in the first aspect, the preparation method comprising:

[0016] A lithium source and an iron source are mixed and pre-sintered to prepare the lithium supplement agent intermediate, wherein the pre-sintering temperature is 100° C.-500° C.

[0017] The present invention pre-sinters the mixture of lithium source and iron source, and releases part of the crystal water and hydroxide in the mixture in the form of water vapor, thereby regulating the content of hydroxide in the pre-sintered product to obtain the Li 5+x FeO 4-(m / 2) ·(OH) m The intermediate can be used to prepare a lithium supplement agent, and the generation of water vapor in the subsequent sintering process can be controlled to optimize the uniformity of the material reaction, thereby obtaining a lithium supplement agent with uniform material, high phase purity and low residual alkali content.

[0018] As a preferred technical solution of the present invention, the pre-sintering time is 2h-10h.

[0019] Preferably, the molar ratio of Li / Fe in the lithium source and the iron source is 5.05-5.55.

[0020] Preferably, the pre-sintering is performed under an inert atmosphere.

[0021] As a preferred technical solution of the present invention, the preparation method further includes adding an additive when mixing the lithium source and the iron source, wherein the additive includes any one of zirconium oxide, aluminum oxide, tungsten oxide, titanium oxide or magnesium oxide, or a combination of at least two thereof.

[0022] In a third aspect, the present invention provides a lithium supplement agent, which is prepared from the lithium supplement agent intermediate described in the first aspect; the lithium supplement agent includes a Li5FeO4 matrix, and a metal oxide coating layer and a carbon coating layer sequentially coated on the surface of the Li5FeO4 matrix.

[0023] In a fourth aspect, the present invention provides a method for preparing the lithium supplement according to the third aspect, the preparation method comprising:

[0024] The lithium supplement agent intermediate is subjected to a first sintering to obtain a first sintered product; the first sintered product is mixed with a coating agent and subjected to a second sintering to obtain a second sintered product; the second sintered product is mixed with a carbon source and subjected to a third sintering to obtain the lithium supplement agent.

[0025] Preferably, the temperature of the first sintering is 700° C.-850° C., and the time of the first sintering is 5 h-10 h.

[0026] Preferably, the temperature of the second sintering is 400° C.-700° C., and the time of the second sintering is 4 hours-10 hours.

[0027] Preferably, the temperature of the third sintering is 420° C.-720° C., and the time of the third sintering is 5 h-10 h.

[0028] Preferably, before the first sintering, the lithium supplement agent intermediate is subjected to a homogeneity treatment.

[0029] Preferably, the coating agent includes any one of zirconium oxide, aluminum oxide, tungsten oxide, titanium oxide, niobium oxide or magnesium oxide, or a combination of at least two thereof.

[0030] Preferably, the carbon source includes any one of conductive carbon black, carbon nanotubes, citric acid, polyethylene glycol, polytetrafluoroethylene or glucose, or a combination of at least two thereof.

[0031] In a fifth aspect, the present invention provides a lithium-ion battery, comprising the lithium supplement agent according to the third aspect.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] (1) The chemical formula of the lithium supplement intermediate provided by the present invention is Li 5+x FeO 4-(m / 2) ·(OH) m , which contains an appropriate amount of hydroxide. The present invention controls the content of hydroxide in the intermediate. When preparing the lithium supplement agent later, it is possible to regulate the generation of water vapor in the subsequent sintering process and optimize the uniformity of the material reaction, thereby obtaining a lithium supplement agent with uniform material, high phase purity and low residual alkali content.

[0034] (2) The present invention pre-sinters the mixture of lithium source and iron source, and releases part of the crystal water and hydroxide in the mixture in the form of water vapor, thereby regulating the content of hydroxide in the pre-sintered product to obtain the Li 5+x FeO 4-m / 2 ·(OH) mWhen the intermediate is used to prepare a lithium supplement agent, the generation of water vapor in the subsequent sintering process can be regulated, and the uniformity of the material reaction can be optimized, thereby obtaining a lithium supplement agent with uniform material and high phase purity. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 1 is the XRD diagram of the lithium supplement agent provided in Example 1 and Comparative Example 1. DETAILED DESCRIPTION

[0036] The technical solution of the present invention is further described below by way of specific embodiments. It should be understood by those skilled in the art that the embodiments are merely to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0037] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" and any variations thereof in this application are intended to cover non-exclusive inclusions.

[0038] In the description of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be understood to indicate or imply relative importance or implicitly indicate the quantity, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, the meaning of "plurality" is more than two, unless otherwise clearly and specifically defined.

[0039] For example, it may include, but is not limited to, the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0040] In the first embodiment, the present invention provides a lithium supplement intermediate, the chemical formula of which is Li 5+x FeO 4-(m / 2) ·(OH) m , where 1.95≤m≤3.27, 0.05≤x≤0.55.

[0041] The lithium supplement intermediate provided by the present invention has the chemical formula Li 5+x FeO 4-(m / 2) ·(OH) m , containing an appropriate amount of hydroxide. During the subsequent preparation of the lithium supplement, the hydroxide in the hydroxide is released as water vapor. By controlling the hydroxide content in the intermediate, the present invention can regulate the generation of water vapor during the subsequent sintering process during the preparation of the lithium supplement, optimizing the uniformity of the material reaction, thereby obtaining a lithium supplement with uniform material and high phase purity.

[0042] In some embodiments, the lithium supplement intermediate further includes a doping element, and the doping element includes any one or a combination of at least two of Zr, Al, W, Ti, Nb or Mg. Typical but non-limiting combinations include a combination of Zr and Al, a combination of W and Ti, a combination of Mg and Zr, a combination of Al and W, or a combination of Ti and Mg.

[0043] In some embodiments, the mass of the doping element accounts for 0.3%-1.0% of the total mass of the lithium supplement intermediate, for example, it can be 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9% or 1.0%, including but not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0044] In a second specific embodiment, the present invention provides a method for preparing the lithium supplement intermediate as described in the first embodiment, the preparation method comprising:

[0045] A lithium source and an iron source are mixed and pre-sintered to prepare the lithium supplement agent intermediate, wherein the pre-sintering temperature is 100° C.-500° C.

[0046] The present invention pre-sinters the mixture of lithium source and iron source, and releases part of the crystal water and hydroxide in the mixture in the form of water vapor, thereby regulating the content of hydroxide in the pre-sintered product to obtain the Li 5+x FeO 4-(m / 2) ·(OH) m When the intermediate is used to prepare a lithium supplement agent, the generation of water vapor in the subsequent sintering process can be controlled, and the uniformity of the material reaction can be optimized, thereby obtaining a lithium supplement agent with uniform material and high phase purity.

[0047] In the present invention, the pre-sintering temperature is 100°C-500°C, for example, it can be 100°C, 150°C, 200°C, 250°C, 300°C, 350°C, 400°C, 450°C or 500°C, including but not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0048] In some embodiments, the lithium source includes any one or a combination of at least two of lithium hydroxide, lithium oxide, lithium carbonate or lithium nitrate. Typical but non-limiting combinations include a combination of lithium hydroxide and lithium oxide, a combination of lithium carbonate and lithium nitrate, a combination of lithium oxide and lithium carbonate, or a combination of lithium nitrate and lithium hydroxide.

[0049] In some embodiments, the iron source comprises iron oxide and / or iron hydroxide.

[0050] In some embodiments, the pre-sintering time is 2h-10h, for example, 2h, 3h, 4h, 5h, 6h, 7h, 8h, 9h or 10h, including but not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0051] In some embodiments, the lithium source and the iron source have a Li / Fe molar ratio of (5.05-5.55):1, for example, 5.05:1, 5.10:1, 5.15:1, 5.20:1, 5.25:1, 5.30:1, 5.35:1, 5.40:1, 5.45:1, 5.50:1 or 5.55:1, including but not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0052] In some embodiments, the pre-sintering is performed under an inert atmosphere, which includes nitrogen and / or an inert gas.

[0053] In some embodiments, the preparation method further includes adding an additive when mixing the lithium source and the iron source, wherein the additive includes any one of zirconium oxide, aluminum oxide, tungsten oxide, titanium oxide, niobium oxide or magnesium oxide, or a combination of at least two thereof. Typical but non-limiting combinations include a combination of zirconium oxide and aluminum oxide, a combination of tungsten oxide and titanium oxide, a combination of magnesium oxide and zirconium oxide, a combination of aluminum oxide and tungsten oxide, or a combination of titanium oxide and magnesium oxide.

[0054] In some embodiments, the preparation method further comprises mechanically crushing the lithium supplement intermediate to homogenize the material and improve the reaction activity.

[0055] In a third specific embodiment, the present invention provides a lithium supplement agent, which is prepared from the lithium supplement agent intermediate described in the first specific embodiment; the lithium supplement agent includes a Li5FeO4 matrix, and a metal oxide coating layer and a carbon coating layer sequentially coated on the surface of the Li5FeO4 matrix.

[0056] In the present invention, a metal oxide coating layer and a carbon coating layer are sequentially arranged on the surface of the Li5FeO4 substrate. The metal oxide coating layer is first arranged on the surface of the Li5FeO4 substrate to improve its air stability, and the carbon coating layer is then arranged to further improve the electrical conductivity of the material.

[0057] In some embodiments, the mass of the metal oxide coating layer accounts for 0.05%-3.00% of the mass of the Li5FeO4 matrix, for example, it can be 0.05%, 0.20%, 0.50%, 0.80%, 1.00%, 1.20%, 1.50%, 2.00%, 2.50% or 3.00%, including but not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0058] In some embodiments, the mass of the carbon coating layer accounts for 0.1%-1% of the mass of the Li5FeO4 matrix, for example, it can be 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9% or 1%, including but not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0059] In a fourth embodiment, the present invention provides a method for preparing the lithium supplement as described in the third embodiment, the preparation method comprising:

[0060] The lithium supplement agent intermediate is subjected to a first sintering to obtain a first sintered product; the first sintered product is mixed with a coating agent and subjected to a second sintering to obtain a second sintered product; the second sintered product is mixed with a carbon source and subjected to a third sintering to obtain the lithium supplement agent.

[0061] In some embodiments, the temperature of the first sintering is 700°C-850°C, for example, it can be 700°C, 720°C, 740°C, 760°C, 780°C, 800°C, 810°C, 830°C or 850°C, including but not limited to the listed values, and other values ​​not listed in the numerical range are also applicable. The time of the first sintering is 5h-10h, for example, it can be 5h, 6h, 7h, 8h, 9h or 10h, including but not limited to the listed values, and other values ​​not listed in the numerical range are also applicable.

[0062] In some embodiments, the temperature of the second sintering is 400°C-700°C, for example, it can be 400°C, 450°C, 500°C, 550°C, 600°C, 650°C or 700°C, including but not limited to the listed values, and other values ​​not listed in the numerical range are also applicable. The time of the second sintering is 4h-10h, for example, it can be 4h, 5h, 6h, 7h, 8h, 9h or 10h, including but not limited to the listed values, and other values ​​not listed in the numerical range are also applicable.

[0063] In some embodiments, the temperature of the third sintering is 420°C-720°C, for example, it can be 420°C, 470°C, 520°C, 570°C, 620°C, 670°C or 720°C, including but not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable. The time of the third sintering is 5h-10h, for example, it can be 5h, 6h, 7h, 8h, 9h or 10h, including but not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0064] In some embodiments, prior to the first sintering, the lithium supplement intermediate is subjected to a homogenization treatment to uniformly distribute the components in the intermediate, further optimize the uniformity of the material reaction, and obtain a lithium supplement with high phase purity. The homogenization treatment method includes, but is not limited to, stirring, ball milling, crushing, or vibration.

[0065] In some embodiments, the first sintering, the second sintering, and the third sintering are each independently performed under an inert atmosphere, and the inert atmosphere includes nitrogen and / or an inert gas.

[0066] In some embodiments, the coating agent includes any one of zirconium oxide, aluminum oxide, tungsten oxide, titanium oxide or magnesium oxide, or a combination of at least two thereof. Typical but non-limiting combinations include a combination of zirconium oxide and aluminum oxide, a combination of tungsten oxide and titanium oxide, a combination of magnesium oxide and zirconium oxide, a combination of aluminum oxide and tungsten oxide, or a combination of titanium oxide and magnesium oxide.

[0067] In some embodiments, the carbon source includes any one or a combination of at least two of conductive carbon black, carbon nanotubes, polytetrafluoroethylene or glucose. Typical but non-limiting combinations include a combination of conductive carbon black and carbon nanotubes, a combination of polytetrafluoroethylene and glucose, a combination of carbon nanotubes and polytetrafluoroethylene, or a combination of glucose and conductive carbon black.

[0068] In some embodiments, the preparation method further comprises, after the first sintering and before the second sintering, sequentially performing mechanical pulverization and air flow pulverization on the first sintered product, in order to control particle size, uniform material, and improve reaction activity.

[0069] After the air flow crushing, sieving is further included, and the mesh size of the sieve is 200-400 mesh, for example, it can be 200 mesh, 250 mesh, 300 mesh, 350 mesh or 400 mesh, including but not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0070] In some embodiments, the preparation method further includes screening the second sintered product after the second sintering and before the third sintering, and the mesh size of the sieve is 200-400 mesh, for example, it can be 200 mesh, 250 mesh, 300 mesh, 350 mesh or 400 mesh, including but not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0071] In a fifth embodiment, the present invention provides a lithium-ion battery, comprising the lithium supplement agent as described in the third embodiment.

[0072] Example 1

[0073] This embodiment provides a lithium supplement intermediate, the chemical formula of which is Li 5.2 FeO 2.71 ·(OH) 2.58 The lithium supplement intermediate further comprises a doping element Zr with a mass ratio of 0.4 wt%. The preparation method of the lithium supplement intermediate comprises:

[0074] According to the Li / Fe molar ratio of 5.2:1, lithium hydroxide and nano-iron oxide were mixed, and zirconium oxide additive was added. Under nitrogen atmosphere, the temperature was raised to 470° C., sintered for 10 hours, and mechanically crushed to prepare the lithium supplement agent intermediate.

[0075] This embodiment also provides a lithium supplement agent, which includes a Li5FeO4 matrix doped with 0.4 wt% of the element Zr, and a 1.5 wt% aluminum oxide coating layer and a 0.5 wt% conductive carbon black coating layer sequentially coated on the surface of the Li5FeO4 matrix. The preparation method of the lithium supplement agent includes:

[0076] Under nitrogen atmosphere, the Li 5.2 FeO 2.71 ·(OH) 2.58 The lithium supplement agent intermediate is subjected to a first sintering at a temperature of 750° C. for 10 hours to obtain a first sintered product; the first sintered product is mechanically crushed, then subjected to air flow crushing, passed through a 300-mesh sieve, mixed with alumina, and subjected to a second sintering at a temperature of 600° C. for 6 hours to obtain a second sintered product; the second sintered product is passed through a 300-mesh sieve, mixed with conductive carbon black, and subjected to a third sintering at a temperature of 600° C. for 5 hours to obtain the lithium supplement agent.

[0077] Example 2

[0078] This embodiment provides a lithium supplement intermediate, the chemical formula of which is Li 5.05 FeO 3.025 ·(OH) 1.95The lithium supplement intermediate further comprises 0.3 wt% of the doping element Mg. The preparation method of the lithium supplement intermediate comprises:

[0079] According to the Li / Fe molar ratio of 5.05:1, 72wt% lithium oxide, 28wt% lithium hydroxide monohydrate and nano-iron oxide were mixed, and magnesium oxide additive was added. Under an argon atmosphere, the temperature was raised to 100°C, sintered for 2 hours, and mechanically crushed to prepare the lithium supplement agent intermediate.

[0080] This embodiment also provides a lithium supplement agent, which includes a Li5FeO4 matrix doped with 0.3 wt% of elemental Mg, and a 1 wt% zirconium oxide coating layer and a 0.8 wt% carbon nanotube coating layer sequentially coated on the surface of the Li5FeO4 matrix. The preparation method of the lithium supplement agent includes:

[0081] Under argon atmosphere, the Li 5.05 FeO 3.025 ·(OH) 1.95 The lithium supplement agent intermediate is subjected to a first sintering at a temperature of 700° C. for 5 hours to obtain a first sintered product; the first sintered product is mechanically crushed, then subjected to air flow crushing, passed through a 200-mesh sieve, mixed with zirconium oxide, and subjected to a second sintering at a temperature of 400° C. for 4 hours to obtain a second sintered product; the second sintered product is passed through a 250-mesh sieve, mixed with carbon nanotubes, and subjected to a third sintering at a temperature of 420° C. for 7 hours to obtain the lithium supplement agent.

[0082] Example 3

[0083] This embodiment provides a lithium supplement intermediate, the chemical formula of which is Li 5.55 FeO 2.365 ·(OH) 3.27 The lithium supplement intermediate further comprises 0.8 wt% of the doping element Ti. The preparation method of the lithium supplement intermediate comprises:

[0084] According to the Li / Fe molar ratio of 5.55:1, lithium hydroxide and nano-iron oxide were mixed, and titanium oxide additive was added. Under nitrogen atmosphere, the temperature was raised to 500° C., sintered for 10 hours, and mechanically crushed to prepare the lithium supplement agent intermediate.

[0085] This embodiment also provides a lithium supplement agent, which includes a Li5FeO4 matrix doped with 0.8 wt% of elemental Mg, and a 0.7 wt% tungsten oxide coating layer and a 0.6 wt% amorphous carbon coating layer sequentially coated on the surface of the Li5FeO4 matrix. The preparation method of the lithium supplement agent includes:

[0086] Under nitrogen atmosphere, the Li5.55 FeO 2.365 ·(OH) 3.27 The lithium supplement agent intermediate is subjected to a first sintering at a temperature of 850° C. for 10 hours to obtain a first sintered product; the first sintered product is mechanically crushed, then subjected to air flow crushing, passed through a 400-mesh sieve, mixed with tungsten zirconium oxide, and subjected to a second sintering at a temperature of 700° C. for 10 hours to obtain a second sintered product; the second sintered product is passed through a 400-mesh sieve, mixed with glucose, and subjected to a third sintering at a temperature of 720° C. for 10 hours to obtain the lithium supplement agent.

[0087] Example 4

[0088] This embodiment provides a lithium supplement agent, which is the same as that of Example 1, except that the surface of the 0.4 wt % Zr-doped Li5FeO4 matrix only includes a carbon coating layer. The preparation method of the lithium supplement agent is the same as that of Example 1, except that alumina is not added during the second sintering process.

[0089] Example 5

[0090] This embodiment provides a lithium supplement agent, which is identical to that of Example 1, except that the surface of the 0.4 wt % Zr-doped Li₅FeO₄ substrate only includes an alumina coating. The preparation method of the lithium supplement agent is identical to that of Example 1, except that carbon nanotubes are not added during the third sintering step.

[0091] Example 6

[0092] This embodiment provides a lithium supplement agent, which is identical to that of Example 1, except that a 0.4 wt % Zr-doped Li₅FeO₄ substrate includes a 0.5 wt % conductive carbon black coating layer and a 1.5 wt % aluminum oxide coating layer in sequence on its surface. The preparation method of the lithium supplement agent is identical to that of Example 1, except that the third sintering step is performed before the second sintering step.

[0093] Comparative Example 1

[0094] This comparative example provides a lithium supplement agent, comprising a Li5FeO4 matrix doped with 0.4 wt% of the element Zr, and a 1.5 wt% aluminum oxide coating layer and a 0.5 wt% conductive carbon black coating layer sequentially coated on the surface of the Li5FeO4 matrix. The preparation method of the lithium supplement agent comprises:

[0095] (1) Preparation of 0.4 wt% Zr-doped Li5FeO4. Lithium nitrate and nano-iron oxide were mixed at a Li / Fe molar ratio of 5.1:1, and titanium oxide was added as an additive. The mixture was heated to 850°C under a nitrogen atmosphere, sintered for 18 h, mechanically crushed, and then subjected to air flow milling to prepare 0.4 wt% Zr-doped Li5FeO4.

[0096] (2) The Zr-doped Li5FeO4 prepared in step (1) was mixed with alumina and sintered at 600°C for 6 hours; the sintered product was sieved through a 300-mesh sieve, mixed with conductive carbon black, and sintered at 600°C for 5 hours to obtain the lithium supplement.

[0097] Comparative Example 2

[0098] This comparative example provides a lithium supplement intermediate, except that the chemical formula of the lithium supplement intermediate is Li 5.2 FeO 3.4 ·(OH) 1.2 The preparation method of the lithium supplement agent intermediate is the same as that of Example 1 except that the pre-sintering temperature is 650° C. and the time is 8 h.

[0099] This comparative example also provides a lithium supplement agent, which is the same as Example 1 except that it is prepared using the lithium supplement agent intermediate provided in this comparative example.

[0100] Comparative Example 3

[0101] This comparative example provides a lithium supplement intermediate, except that the chemical formula of the lithium supplement intermediate is Li 5.2 Except for FeO2·(OH)4, the rest are the same as those in Example 1; the preparation method of the lithium supplement agent intermediate is the same as that in Example 1 except that the pre-sintering temperature is 90°C and the time is 2h.

[0102] This comparative example also provides a lithium supplement agent, which is the same as Example 1 except that it is prepared using the lithium supplement agent intermediate provided in this comparative example.

[0103] Performance testing:

[0104] The pH and residual alkali of the lithium supplements prepared in all the above examples and comparative examples were tested. The test results are shown in Table 1.

[0105] The lithium supplement prepared in all the above examples and comparative examples was mixed with PVDF and conductive carbon black in a mass ratio of 85:5:10 to prepare a positive electrode sheet. Metallic lithium was used as the negative electrode and a 15wt% LiPF6 solution with an EC:DEC ratio of 1:1 was used as the electrolyte to assemble a button battery. The initial charge capacity of the lithium supplement was tested at 2.5V-4.4V and 0.1C.

[0106] The XRD test results of the lithium supplement prepared in Example 1 and Comparative Example 1 are shown in Figure 1 .

[0107] Table 1

[0108]

[0109] like Figure 1 The XRD patterns of the lithium supplement provided in Example 1 and Comparative Example 1 show that the lithium supplement prepared by the lithium supplement intermediate containing an appropriate amount of hydroxide provided by the present invention has a higher phase purity, a residual alkali value as low as 0.38%, and an initial charge capacity as high as 747 mAh / g.

[0110] According to the test results of Examples 1 and 4, if the sintering temperature is too high when preparing the lithium supplement agent intermediate, the hydroxide content in the prepared lithium supplement agent intermediate is too low. When the lithium supplement agent is subsequently prepared, the reaction between iron and lithium salt is too violent and the reaction process is uncontrollable, resulting in large differences in the particle size of the formed Li5FeO4 and poor particle size uniformity, resulting in low capacity.

[0111] Similarly, the test results in Example 1 and Comparative Examples 1 to Comparative Examples 3 also demonstrate that when the lithium supplement agent intermediate provided by the present invention is not used to further prepare the lithium supplement agent, or when the hydroxide content in the lithium supplement agent intermediate is not within the range of the lithium supplement agent intermediate provided by the present invention, it is impossible to effectively control the generation of water vapor in the subsequent sintering process and optimize the uniformity of the material reaction, thereby affecting the uniformity of the obtained material, and it is impossible to obtain a lithium supplement agent with high phase purity, low residual alkali content and high capacity.

[0112] The applicant declares that the above is only a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention fall within the scope of protection and disclosure of the present invention.

Claims

1. A lithium supplement intermediate, characterized in that: The chemical formula of the lithium supplement intermediate is Li 5+x FeO 4-(m / 2) ·(OH) m , where 1.95≤m≤3.27, 0.05≤x≤0.55; The iron source for preparing the lithium supplement intermediate includes iron oxide and / or iron hydroxide.

2. The lithium supplement intermediate according to claim 1, wherein The lithium supplement intermediate further includes a doping element; The mass of the doping element accounts for 0.3%-1.0% of the total mass of the lithium supplement intermediate; The doping element includes any one of Zr, Al, W, Ti, Nb or Mg, or a combination of at least two of them.

3. A method for preparing the lithium supplement intermediate according to claim 1 or 2, characterized in that: The preparation method comprises: Mixing a lithium source and an iron source, and pre-sintering them under an inert atmosphere to prepare the lithium supplement agent intermediate; The pre-sintering temperature is 100°C-500°C; The iron source includes iron oxide and / or iron hydroxide.

4. The preparation method according to claim 3, wherein The pre-sintering time is 2h-10h; And / or, in the lithium source and the iron source, the Li / Fe molar ratio is 5.05-5.

55.

5. The preparation method according to claim 3, wherein The preparation method further comprises adding an additive when mixing the lithium source and the iron source, wherein the additive comprises any one of zirconium oxide, aluminum oxide, tungsten oxide, titanium oxide or magnesium oxide, or a combination of at least two thereof.

6. A lithium supplement, characterized in that: The lithium supplement agent is prepared from the lithium supplement agent intermediate according to claim 1 or 2; The lithium supplement comprises a Li5FeO4 matrix, and a metal oxide coating layer and a carbon coating layer sequentially coated on the surface of the Li5FeO4 matrix.

7. A method for preparing the lithium supplement according to claim 6, characterized in that: The preparation method comprises: The lithium supplement agent intermediate is subjected to a first sintering to obtain a first sintered product; the first sintered product is mixed with a coating agent and subjected to a second sintering to obtain a second sintered product; the second sintered product is mixed with a carbon source and subjected to a third sintering to obtain the lithium supplement agent.

8. The preparation method according to claim 7, wherein The temperature of the first sintering is 700° C.-850° C., and the time of the first sintering is 5 h-10 h; And / or, the temperature of the second sintering is 400° C.-700° C., and the time of the second sintering is 4 hours-10 hours; And / or, the temperature of the third sintering is 420° C.-720° C., and the time of the third sintering is 5 h-10 h; And / or, before the first sintering, the lithium supplement agent intermediate is subjected to a uniformity treatment.

9. The preparation method according to claim 7, wherein The coating agent includes any one of zirconium oxide, aluminum oxide, tungsten oxide, titanium oxide, niobium oxide or magnesium oxide, or a combination of at least two thereof; And / or, the carbon source includes any one or a combination of at least two of conductive carbon black, carbon nanotubes, polyethylene glycol, citric acid, polytetrafluoroethylene or glucose.

10. A lithium ion battery, characterized in that: The lithium-ion battery includes the lithium supplement according to claim 6.

Images