Positive electrode lithium supplement agent and preparation method and application thereof

Abstract

The invention provides a positive electrode lithium supplement agent and a preparation method and application thereof. The preparation method comprises the following steps that a metal source solution, a precipitant solution and an oxidizing agent solution are mixed for the first time, then a reaction is conducted, first slurry is obtained, and the first slurry comprises metal oxyhydroxide; performing second mixing on the first slurry, a lithium source, a reducing agent and a coating agent to obtain a mixture; and sintering the mixture to obtain the positive electrode lithium supplement agent. According to the preparation method, the process is simple, the consistency of product batches is improved, the valence state of metal elements is stabilized, the safety risk of the battery is reduced, and the overall safety of the battery is improved; and secondly, the positive electrode lithium supplementing agent prepared based on the preparation method is high in applicability and can better play a lithium supplementing effect in the charging and discharging process, and when the positive electrode lithium supplementing agent is used in cooperation with an active material, due to the fact that the valence state of non-lithium metal elements of the positive electrode lithium supplementing agent is stable, side reactions of the battery are reduced, the energy density of the battery is improved, and the cycle life of the battery is prolonged.

Description

Technical Field

[0001] The present invention belongs to the technical field of battery materials, and particularly relates to a cathode lithium supplement agent, a preparation method thereof, and an application thereof. Background Art

[0002] Lithium-ion batteries are one of the most promising and widely used batteries at present due to their high energy density, low self-discharge rate, long cycle life, and environmental friendliness.

[0003] However, current lithium-ion batteries have the following problems: During the first charging process of lithium-ion batteries, lithium ions in the cathode are embedded into the anode, and the solid electrolyte interface (SEI film) formed on the anode surface will consume a part of the active lithium, resulting in a loss of the first specific capacity of the lithium-ion battery and a reduction in the battery energy density. To compensate for this loss, a lithium supplementation method is usually used for compensation. For example, CN115621461A discloses a preparation method of a cathode lithium supplement agent, which includes depositing a carbon source on the surface of a cathode lithium supplement agent precursor by means of low-temperature chemical vapor deposition; wherein, the cathode lithium supplement agent precursor includes a lithium carbon oxide, and the lithium carbon oxide includes L i2 C 2 O 4 、Li 2 C 4 O 4At least one of the following: the low-temperature vapor deposition is carried out in a reaction chamber of a chemical vapor deposition device with a cooling device, and the carbon source passes through a catalyst chamber in the reaction chamber to form a nano-carbon material and is deposited on the surface of the positive electrode lithium supplement precursor; wherein the temperature of the cooling device is -30 to -20°C, the temperature of the catalyst chamber is 400-900°C, and the chemical vapor deposition time is 0.5-12h. CN119252921A discloses a method for preparing an ultra-high capacity positive electrode lithium supplement, comprising the following steps: mixing, mixing a lithium source and a transition metal compound MO at a high speed in an inert atmosphere according to a specified ratio to obtain an initial mixed material; sintering, placing the initial mixed material in an inert atmosphere for high-temperature sintering to obtain a sintered material; ball milling, ball milling the sintered material to obtain a positive electrode lithium supplement. CN118431477A discloses a method for preparing a positive electrode lithium supplement, comprising the following steps: mixing a lithium source and an iron source, and then pressing the tablets once to obtain a sheet precursor; sintering the sheet precursor once to obtain a crude product; crushing the crude product, adding a lithium source, and then ball milling it evenly, pressing the tablets a second time, and sintering it a second time to obtain a positive electrode lithium supplement; wherein the temperature of the second sintering is higher than the temperature of the first calcination. In the above-mentioned existing lithium supplement methods, the use of multiple tableting and sintering may lead to poor consistency between product batches, affecting the electrochemical properties of the positive electrode lithium supplement; the uniformity of particle size and distribution during ball milling is difficult to accurately control; the operation of adding a lithium source may lead to waste of the lithium source, especially during high-temperature sintering, lithium may volatilize or react with other components, resulting in poor cycle life and energy density of the battery, and limited commercial application prospects.

[0004] Therefore, providing a process method for lithium supplementation to improve the consistency of product batches and enhance the energy density and cycle life of batteries is a technical problem that needs to be solved urgently. Summary of the invention

[0005] In view of the deficiencies of the prior art, the purpose of the present invention is to provide a positive electrode lithium supplement agent and its preparation method and application. The present invention optimizes the preparation method of the positive electrode lithium supplement agent, which not only simplifies the process and improves the consistency of product batches, but also stabilizes the valence state of the metal element, which is conducive to reducing the possibility of internal short circuit or other safety risks of the battery, thereby improving the overall safety of the battery; secondly, the positive electrode lithium supplement agent prepared based on this preparation method has strong applicability, can better play the lithium supplement effect during the charging and discharging process, and when used in combination with active materials, due to the stable valence state of the non-lithium metal elements of the positive electrode lithium supplement agent, it is conducive to reducing the side reactions of the battery and improving the energy density and cycle life of the battery.

[0006] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

[0007] In a first aspect, the present invention provides a method for preparing a cathode lithium supplement agent, and the preparation method includes the following steps:

[0008] Perform a first mixing on a metal source solution, a precipitant solution, and an oxidant solution, and then carry out a reaction to obtain a first slurry, and the first slurry includes metal hydroxyoxide.

[0009] Perform a second mixing on the first slurry, a lithium source, a reducing agent, and a coating agent to obtain a mixture.

[0010] Sinter the mixture to obtain the cathode lithium supplement agent.

[0011] The present invention optimizes the preparation method of the cathode lithium supplement agent. Not only is the process simple, but also the valence states of metal elements are stabilized, which is beneficial to reducing the possibility of internal short circuit or other safety risks in the battery, thereby improving the overall safety of the battery; secondly, the cathode lithium supplement agent prepared based on this preparation method has strong applicability and can better exert the lithium supplement effect during charge and discharge. When used in combination with active materials, due to the stable valence states of non-lithium metal elements in the cathode lithium supplement agent, it is beneficial to reduce side reactions of the battery and improve the energy density and cycle life of the battery.

[0012] In the present invention, metal hydroxyoxide exhibits better cycle stability than metal hydroxide in an electrochemical system, especially under high potential conditions; and less pollution is generated during its preparation and use.

[0013] Preferably, the technological process of the preparation method is carried out under an inert atmosphere. Exemplarily, for example, it can be nitrogen, etc.

[0014] The preparation method provided by the present invention is carried out under an inert atmosphere, which can make the valence states of non-lithium metal elements in the prepared cathode lithium supplement agent stable, so as to better exert the lithium supplement effect during charge and discharge and improve the energy density and cycle life of the battery.

[0015] Preferably, the metal source solution includes a nickel source solution.

[0016] Preferably, in the nickel source solution, the nickel source includes any one or a combination of at least two of nickel sulfate heptahydrate, nickel chloride, or nickel carbonate.

[0017] Preferably, the precipitant solution includes an alkali solution. Exemplarily, for example, it can be a sodium hydroxide solution, etc.

[0018] Preferably, the concentration of the alkali solution is 1-10 mol / L, for example, it can be 1 mol / L, 2 mol / L, 3 mol / L, 4 mol / L, 5 mol / L, 6 mol / L, 7 mol / L, 8 mol / L, 9 mol / L, or 10 mol / L, etc.

[0019] Preferably, the oxidant solution includes a hydrogen peroxide solution.

[0020] Preferably, the concentration of the hydrogen peroxide solution is 5-15 wt%, and for example, it can be 5 wt%, 7 wt%, 10 wt%, 12 wt% or 15 wt% etc.

[0021] Preferably, the method for the first mixing includes:

[0022] Adding the metal source solution, the precipitant solution and the oxidant solution into the reaction kettle in a co-current manner.

[0023] Preferably, the concentration of the metal source solution is 0.5-4 mol / L, and for example, it can be 0.5 mol / L, 1 mol / L, 1.5 mol / L, 2 mol / L, 2.5 mol / L, 3 mol / L, 3.5 mol / L or 4 mol / L etc.

[0024] Preferably, the flow rate ratio of the metal source solution, the precipitant solution and the oxidant solution is (0.8-1.2):(0.8-1.2):(0.8-1.2). Among them, the selection range "0.8-1.2" of the metal source solution can be, for example, 0.8, 0.9, 1, 1.1 or 1.2 etc., the selection range "0.8-1.2" of the precipitant solution can be, for example, 0.8, 0.9, 1, 1.1 or 1.2 etc., and the selection range "0.8-1.2" of the oxidant solution can be, for example, 0.8, 0.9, 1, 1.1 or 1.2 etc.

[0025] In the present invention, an appropriate flow rate ratio of the metal source solution, the precipitant solution and the oxidant solution helps to avoid side reactions or the generation of impurities caused by an excess or deficiency of a certain component, thereby improving the purity of the product. And an appropriate flow rate ratio helps to maintain the balance of the reaction rate and avoid the reaction from being too fast or too slow.

[0026] Preferably, the metal hydroxyoxide includes nickel oxyhydroxide.

[0027] Exemplarily, the chemical equation for generating nickel oxyhydroxide is shown as follows:

[0028] NiSO 4 +NaOH+H 2 O 2 →NiOOH+Na 2 SO 4 +H 2 O. The specific reaction process includes: first, a precipitation reaction occurs to generate nickel hydroxide, and then an oxidation reaction occurs with the oxidant to generate nickel oxyhydroxide.

[0029] Preferably, during the reaction, the rotation speed of the reaction system is 200 - 600 rpm, for example, it can be 200 rpm, 300 rpm, 400 rpm, 500 rpm or 600 rpm, etc.

[0030] Preferably, the reaction temperature is 40 - 60 °C, for example, it can be 40 °C, 50 °C or 60 °C, etc.

[0031] Preferably, during the reaction, the pH value of the reaction system is 8 - 12, for example, it can be 8, 9, 10, 11 or 12, etc.

[0032] Preferably, the second mixing method includes:

[0033] Mix the first slurry and the lithium source, and obtain a metal mixture after drying.

[0034] Blend the metal mixture, the reducing agent and the coating agent.

[0035] Preferably, the lithium source includes any one or a combination of at least two of lithium carbonate, lithium hydroxide or lithium chloride.

[0036] Preferably, in the metal mixture, the molar ratio of the metal element to the lithium element in the metal hydroxyoxide is 1:(2 - 2.2), for example, it can be 1:2, 1:2.05, 1:2.1, 1:2.15 or 1:2.2, etc.

[0037] In the present invention, the molar ratio of the metal element to the lithium element in the metal hydroxyoxide is within a suitable range, which helps to avoid side reactions or impurity generation caused by an excess or deficiency of a certain component, thereby improving the cycling performance of the cathode lithium supplement agent.

[0038] Preferably, the reducing agent includes any one or a combination of at least two of glucose, sucrose or starch.

[0039] Preferably, the coating agent includes any one or a combination of at least two of an aluminum source, a boron source or a magnesium source.

[0040] Preferably, the aluminum source includes any one or a combination of at least two of aluminum isopropoxide, aluminum hydroxide or Al 2 O 3 in it.

[0041] Preferably, the molar ratio of the metal hydroxyoxide in the metal mixture to the reducing agent is 1:(0.03 - 0.05), for example, it can be 1:0.03, 1:0.04 or 1:0.05, etc.

[0042] In the present invention, the molar ratio of the metal hydroxide in the metal mixture to the reducing agent within an appropriate range is helpful for forming a cathode lithium supplement agent with high capacity and high stability.

[0043] Preferably, the molar ratio of the metal element in the metal hydroxide to the coating element in the coating agent is 1:(0.007 - 0.031), and for example, it can be 1:0.007, 1:0.01, 1:0.015, 1:0.02, 1:0.025, 1:0.03 or 1:0.031, etc.

[0044] In the present invention, the molar ratio of the metal element in the metal hydroxide to the coating element in the coating agent within an appropriate range is helpful for forming a good interfacial bond between the metal hydroxide and the coating layer, improving the mechanical strength and electrochemical stability of the material; in addition, the good interfacial bond can reduce the volume change and stress concentration of the material during charge and discharge.

[0045] Preferably, stirring is accompanied during the blending process.

[0046] Preferably, the stirring rate is 200 - 600 rpm, and for example, it can be 200 rpm, 300 rpm, 400 rpm, 500 rpm or 600 rpm, etc.

[0047] Preferably, before the mixture is sintered, the mixture is compacted first.

[0048] In the present invention, the purpose of the compaction treatment is to reduce the pores between the mixture particles and make the arrangement more compact, thereby improving the overall density of the mixture, which helps to reduce shrinkage during the sintering process, improve the density and strength of the sintered body, and enable the cathode lithium supplement agent to have better performance; secondly, it can improve the air permeability of the mixture, so that gas can be discharged more smoothly during the sintering process, avoiding defects such as pores and cracks caused by gas retention, and being beneficial to improving the quality of the sintered product.

[0049] Preferably, the sintering atmosphere is an inert atmosphere. Exemplarily, for example, it can be nitrogen, etc.

[0050] Exemplarily, the chemical reactions occurring during the sintering process include the following chemical reaction equations:

[0051]

[0052] Preferably, the sintering is multi-stage sintering, and the multi-stage sintering includes the first-stage sintering and the second-stage sintering.

[0053] The present invention adopts a multi-stage sintering method, which on the one hand helps to stabilize the valence of non-lithium metal elements in the lithium-rich active material, and on the other hand, for the coating layer on the surface of the lithium-rich active material, it helps to improve its uniformity and enhance the bonding strength between the coating layer and the lithium-rich active material, making the lithium supplementing effect of the cathode lithium supplementing agent better.

[0054] Preferably, the temperature of the first-stage sintering is 250-400 °C, for example, it can be 250 °C, 300 °C, 350 °C or 400 °C, etc.

[0055] Preferably, the heat preservation time of the first-stage sintering is 2-8 h, for example, it can be 2 h, 3 h, 4 h, 54 h, 6 h, 7 h or 8 h, etc.

[0056] Preferably, the temperature of the second-stage sintering is 500-800 °C, for example, it can be 500 °C, 600 °C, 700 °C or 800 °C, etc.

[0057] Preferably, the time of the second-stage sintering is 3-12 h, for example, it can be 3 h, 4 h, 5 h, 6 h, 7 h, 8 h, 9 h, 10 h, 11 h or 12 h, etc.

[0058] Preferably, the preparation method is carried out in an inert atmosphere and includes the following steps:

[0059] (1) Dissolve the metal source in an aqueous solvent to obtain a metal source solution with a concentration of 0.5-4 mol / L;

[0060] The metal source solution, the alkali solution and the hydrogen peroxide solution are added into the reaction kettle in a co-current manner according to a flow rate ratio of (0.8-1.2):(0.8-1.2):(0.8-1.2), and the reaction is carried out at 40-60 °C to obtain a first slurry, and the first slurry includes metal hydroxyoxides.

[0061] Among them, the concentration of the alkali solution is 1-10 mol / L, and the concentration of the hydrogen peroxide solution is 5-15 wt%; during the reaction process, the rotation speed of the reaction system is 200-600 rpm, and the pH value is 8-12.

[0062] (2) Mix the first slurry and the lithium source, and then dry the mixed slurry to remove moisture to obtain a metal mixture; in the metal mixture, the molar ratio of the metal element of the metal hydroxyoxide to the lithium element is 1:(2-2.2).

[0063] (3) Crush the metal mixture, and then stir and blend it with a reducing agent and a coating agent at a stirring rate of 200 - 600 rpm to obtain a mixed material; wherein, the molar ratio of the metal hydroxide in the metal mixture to the reducing agent is 1:(0.03 - 0.05), and the molar ratio of the metal element in the metal hydroxide to the coating element in the coating agent is 1:(0.007 - 0.031).

[0064] Press the mixed material at a pressure of 20 - 40 tons (such as 20 tons, 25 tons, 30 tons, 35 tons or 40 tons, etc.) to obtain a pressed material.

[0065] (4) Conduct multi-stage sintering on the pressed material. First, conduct the first-stage sintering at 250 - 400 °C for 2 - 8 h, and then conduct the second-stage sintering at 500 - 800 °C for 3 - 12 h to obtain a sintered product.

[0066] Crush and screen the sintered product to obtain the cathode lithium supplement agent.

[0067] In the first aspect, the present invention provides a cathode lithium supplement agent, which is prepared by the preparation method of the cathode lithium supplement agent as described in the first aspect.

[0068] The cathode lithium supplement agent includes a lithium-rich active material and a coating layer coated on the surface of the lithium-rich active material.

[0069] Preferably, the lithium-rich active material includes Li 2 NiO 2 and / or Li 2 FeO 2 .

[0070] Preferably, the material of the coating layer includes any one or a combination of at least two of alumina, boron oxide or magnesium oxide.

[0071] In the third aspect, the present invention provides a cathode material, which includes a cathode lithium supplement agent. The cathode lithium supplement agent is prepared by the preparation method described in the first aspect or is the cathode lithium supplement agent described in the second aspect.

[0072] It should be noted that the cathode active material used in combination with the cathode lithium supplement agent can be, for example, lithium iron phosphate, lithium manganese iron phosphate or lithium nickel cobalt manganese oxide, etc.

[0073] Preferably, in the cathode material, the mass ratio of the cathode lithium supplement agent is 0.5 - 2%, such as 0.5%, 1%, 1.5% or 2%, etc.

[0074] Fourth aspect, the present invention provides a lithium-ion battery, and the positive electrode sheet of the lithium-ion battery includes the positive electrode material as described in the third aspect.

[0075] The numerical ranges described in the present invention not only include the above-listed point values, but also include any point values between the above numerical ranges that are not listed. Due to space limitations and for the sake of simplicity, the present invention does not exhaustively list the specific point values included in the range.

[0076] Compared with the prior art, the present invention has the following beneficial effects:

[0077] (1) The present invention optimizes the preparation method of the positive electrode lithium supplement agent. Not only is the process simple, improving the consistency of product batches, but also the valence states of metal elements are stabilized, which is beneficial to reducing the possibility of internal short circuits or other safety risks in the battery, thereby improving the overall safety of the battery.

[0078] (2) The positive electrode lithium supplement agent prepared based on the preparation method provided by the present invention has strong applicability and can be used in combination with a variety of active materials. Moreover, the positive electrode lithium supplement agent can better exert the lithium supplement effect during charge and discharge. At the same time, due to the stable valence states of non-lithium metal elements in the positive electrode lithium supplement agent, it is beneficial to reduce side reactions in the battery and improve the energy density and cycle life of the battery.

[0079] (3) In the positive electrode lithium supplement agent prepared based on the preparation method provided by the present invention, the setting of the coating layer can isolate moisture and reduce the influence of moisture on the lithium-rich active material in the positive electrode lithium supplement agent, which is beneficial to improving the processing performance of the battery. Description of the Drawings

[0080] Figure 1 It is a schematic structural diagram of the positive electrode lithium supplement agent provided in Embodiment 1 of the present invention.

[0081] Among them, 1 - lithium-rich active material; 2 - coating layer. Detailed Embodiments

[0082] The technical solutions of the present invention will be further described below through specific embodiments. Those skilled in the art should understand that the embodiments are only for helping to understand the present invention and should not be regarded as specific limitations to the present invention.

[0083] Embodiment 1

[0084] This embodiment provides a preparation method of a positive electrode lithium supplement agent. The preparation method is carried out under a nitrogen atmosphere and includes the following steps:

[0085] (1) Dissolve nickel sulfate heptahydrate in water to obtain a nickel sulfate solution with a concentration of 2 mol / L;

[0086] The nickel sulfate solution, sodium hydroxide solution, and hydrogen peroxide solution are added to a reaction kettle at a flow rate ratio of 1:1:1 in a uniform and parallel flow manner, and the reaction is carried out at 50 °C to obtain a first slurry, and nickel oxyhydroxide is included in the first slurry.

[0087] Among them, the concentration of the sodium hydroxide solution is 5 mol / L, and the concentration of the hydrogen peroxide solution is 10 wt%; during the reaction process, the rotation speed of the reaction system is 400 rpm, and the pH value is 10.

[0088] (2) The first slurry and lithium carbonate are mixed, and then the mixed slurry is dried in a blast drying oven (nitrogen is blown) to remove moisture to obtain a metal mixture; in the metal mixture, the molar ratio of nickel element to lithium element in nickel oxyhydroxide is 1:2.1.

[0089] (3) The metal mixture is transferred to a glove box, the humidity is controlled at 5%, and it is pulverized, and then stirred and blended with glucose and aluminum isopropoxide, and the stirring rate is 400 rpm to obtain a mixed material; among them, the molar ratio of nickel oxyhydroxide to glucose in the metal mixture is 1:0.04, and the molar ratio of nickel element in nickel oxyhydroxide to aluminum element in aluminum isopropoxide is 1:0.019.

[0090] The mixed material is tableted under a pressure of 30 tons to obtain a tableted material.

[0091] (4) The tableted material is subjected to multi-stage sintering. First, the first-stage sintering is carried out at 300 °C for 5 h, and then the second-stage sintering is carried out at 650 °C for 8 h to obtain a sintered product.

[0092] The sintered product is pulverized, sieved, and sealed and packaged in a glove box to obtain the positive electrode lithium supplement agent.

[0093] This embodiment also provides a positive electrode lithium supplement agent, and the positive electrode lithium supplement agent is prepared by using the preparation method described above.

[0094] The structural schematic diagram of the positive electrode lithium supplement agent is as Figure 1 shown, and it includes interlaced lithium-rich active materials 1 and a coating layer 2 coated on the surface of the lithium-rich active materials 1; among them, the lithium-rich active materials 1 are Li 2 NiO 2 .

[0095] This embodiment also provides a positive electrode material, and the positive electrode material includes a positive electrode active material and the above positive electrode lithium supplement agent; among them, the positive electrode active material is lithium iron phosphate; in the positive electrode material, the mass ratio of the positive electrode lithium supplement agent is 0.65%.

[0096] Example 2

[0097] This embodiment provides a preparation method of a cathode lithium supplement agent. The preparation method is carried out under a nitrogen atmosphere and includes the following steps:

[0098] (1) Dissolve nickel sulfate heptahydrate in water to obtain a nickel sulfate solution with a concentration of 0.5 mol / L;

[0099] Add the nickel sulfate solution, sodium hydroxide solution, and hydrogen peroxide solution into a reaction kettle at a uniform flow rate ratio of 0.8:1.2:0.8 and react at 40 °C to obtain a first slurry, which includes nickel oxyhydroxide.

[0100] Among them, the concentration of the sodium hydroxide solution is 1 mol / L, and the concentration of the hydrogen peroxide solution is 5 wt%; during the reaction process, the rotation speed of the reaction system is 200 rpm, and the pH value is 8.

[0101] (2) Mix the first slurry and lithium carbonate, and then dry the mixed slurry in a blast drying oven (blowing nitrogen) to remove moisture to obtain a metal mixture; in the metal mixture, the molar ratio of nickel element to lithium element in nickel oxyhydroxide is 1:2.

[0102] (3) Transfer the metal mixture to a glove box, control the humidity at 5%, crush it, and then stir and blend it with glucose and aluminum hydroxide at a stirring rate of 200 rpm to obtain a mixed material; among them, the molar ratio of nickel oxyhydroxide in the metal mixture to glucose is 1:0.03, and the molar ratio of nickel element in nickel oxyhydroxide to aluminum element in aluminum hydroxide is 1:0.007.

[0103] Press the mixed material at a pressure of 20 tons to obtain a pressed sheet.

[0104] (4) Carry out multi-stage sintering on the pressed sheet. First, carry out the first-stage sintering at 250 °C for 8 h, and then carry out the second-stage sintering at 500 °C for 12 h to obtain a sintered product.

[0105] Crush, screen, and seal and package the sintered product in a glove box to obtain the cathode lithium supplement agent.

[0106] This embodiment also provides a cathode lithium supplement agent, which is prepared by using the preparation method described above.

[0107] The cathode lithium supplement agent includes a lithium-rich active material and a coating layer coated on the surface of the lithium-rich active material; among them, the lithium-rich active material is Li 2 NiO 2 .

[0108] This embodiment also provides a cathode material, which includes a cathode active material and the above-mentioned cathode lithium supplement agent; wherein, the cathode active material is lithium iron manganese phosphate; in the cathode material, the mass ratio of the cathode lithium supplement agent is 0.8%.

[0109] Example 3

[0110] This embodiment provides a preparation method of a cathode lithium supplement agent. The preparation method is carried out in a nitrogen atmosphere and includes the following steps:

[0111] (1) Dissolve nickel sulfate heptahydrate in water to obtain a nickel sulfate solution with a concentration of 4 mol / L;

[0112] Add the nickel sulfate solution, sodium hydroxide solution and hydrogen peroxide solution into the reaction kettle at a uniform flow rate in a flow ratio of 1.2:0.8:1.2, and react at 60 °C to obtain a first slurry, which includes nickel oxyhydroxide.

[0113] Among them, the concentration of the sodium hydroxide solution is 10 mol / L, and the concentration of the hydrogen peroxide solution is 15 wt%; during the reaction process, the rotation speed of the reaction system is 600 rpm, and the pH value is 12.

[0114] (2) Mix the first slurry and lithium carbonate, and then dry the mixed slurry in a blast drying oven (blowing nitrogen) to remove moisture to obtain a metal mixture; in the metal mixture, the molar ratio of nickel element to lithium element in nickel oxyhydroxide is 1:2.2.

[0115] (3) Transfer the metal mixture to a glove box, control the humidity at 5%, crush it, and then stir and blend it with glucose and Al 2 O 3 The stirring rate is 600 rpm to obtain a mixed material; among them, the molar ratio of nickel oxyhydroxide in the metal mixture to glucose is 1:0.05, and the molar ratio of nickel element in nickel oxyhydroxide to aluminum element in the Al 2 O 3 is 1:0.031.

[0116] Press the mixed material at a pressure of 40 tons to obtain a tablet.

[0117] (4) Carry out multi-stage sintering on the tablet. First, carry out the first-stage sintering at 400 °C for 2 h, and then carry out the second-stage sintering at 800 °C for 3 h to obtain a sintered product.

[0118] Crush, screen and seal the sintered product in a glove box to obtain the cathode lithium supplement agent.

[0119] This embodiment also provides a cathode lithium supplement agent, which is prepared by the preparation method described above.

[0120] The cathode lithium supplement agent includes a lithium-rich active material and a coating layer coated on the surface of the lithium-rich active material; wherein, the lithium-rich active material is Li 2 NiO 2 .

[0121] This embodiment also provides a cathode material, which includes a cathode active material and the above-mentioned cathode lithium supplement agent; wherein, the cathode active material is lithium nickel cobalt manganate; in the cathode material, the mass ratio of the cathode lithium supplement agent is 0.6%.

[0122] Example 4

[0123] The difference between this embodiment and Example 1 is that the first slurry, lithium carbonate, glucose, and Al 2 O 3 are directly mixed to obtain a mixture.

[0124] The remaining preparation methods and parameters are the same as those in Example 1.

[0125] Example 5

[0126] The difference between this embodiment and Example 1 is that in the metal mixture in step (2), the molar ratio of nickel element to lithium element in nickel oxyhydroxide is 1:2.5.

[0127] The remaining preparation methods and parameters are the same as those in Example 1.

[0128] Example 6

[0129] The difference between this embodiment and Example 1 is that in the metal mixture in step (2), the molar ratio of nickel element to lithium element in nickel oxyhydroxide is 1:1.5.

[0130] The remaining preparation methods and parameters are the same as those in Example 1.

[0131] Example 7

[0132] The difference between this embodiment and Example 1 is that in step (3), the molar ratio of nickel oxyhydroxide to glucose in the metal mixture is 1:0.06.

[0133] The remaining preparation methods and parameters are the same as those in Example 1.

[0134] Example 8

[0135] The difference between this embodiment and Example 1 is that in step (3), the molar ratio of nickel oxyhydroxide to glucose in the metal mixture is 1:0.02.

[0136] The remaining preparation methods and parameters are the same as those in Example 1.

[0137] Example 9

[0138] The difference between this example and Example 1 is that the molar ratio of nickel element in nickel oxyhydroxide to aluminum element in aluminum isopropoxide in step (3) is 1:0.04.

[0139] The remaining preparation methods and parameters are the same as those in Example 1.

[0140] Example 10

[0141] The difference between this example and Example 1 is that the molar ratio of nickel element in nickel oxyhydroxide to aluminum element in aluminum isopropoxide in step (3) is 1:0.005.

[0142] The remaining preparation methods and parameters are the same as those in Example 1.

[0143] Example 11

[0144] The difference between this example and Example 1 is that no tablet pressing treatment is carried out in step (3).

[0145] The remaining preparation methods and parameters are the same as those in Example 1.

[0146] Comparative Example 1

[0147] The difference between this comparative example and Example 1 is that no hydrogen peroxide solution is added in step (1).

[0148] The remaining preparation methods and parameters are the same as those in Example 1.

[0149] Comparative Example 2

[0150] The difference between this comparative example and Example 1 is that no glucose is added in step (3).

[0151] The remaining preparation methods and parameters are the same as those in Example 1.

[0152] Performance Test

[0153] The cathode materials provided in the above examples and comparative examples are mixed with conductive carbon black and polyvinylidene fluoride in a mass ratio of 8:1:1, and added to N-methylpyrrolidone to make a slurry, and then coated on an aluminum foil. After drying, a cathode sheet is obtained; the anode sheet is a lithium metal sheet, the separator is a polypropylene film, and the electrolyte is a 1 mol / L lithium hexafluorophosphate carbonate solution (the solvent is composed of ethylene carbonate and dimethyl carbonate with a volume ratio of 1:1); the above cathode sheet, anode sheet, separator and electrolyte are assembled to obtain a lithium-ion battery.

[0154] The charge-discharge performance of the above lithium-ion battery was tested under the following conditions: after the battery was left standing for 3 h, charge / discharge tests were carried out on a LAND battery test system with a voltage range of 2.0 - 4.5 V. The discharge specific capacities of the battery at currents of 0.1C and 1C were recorded respectively. The calculation method for the first efficiency was: the discharge gram capacity of the first cycle / the charge gram capacity of the first cycle × 100%; the capacity retention rate of the battery after 100 cycles at a current of 1C was calculated and recorded, and the calculation method for the capacity retention rate was: the discharge capacity of the 100th cycle / the discharge capacity of the first cycle × 100%.

[0155] The above test results are shown in Table 1 below.

[0156] Table 1

[0157]

[0158]

[0159] Analysis:

[0160] As can be seen from the above table, the cathode lithium supplement agent prepared based on the preparation method provided by the present invention has strong applicability and can be used in combination with a variety of active materials. Moreover, the cathode lithium supplement agent can better play the role of lithium supplementation during the charge-discharge process. At the same time, due to the stable valence state of the non-lithium metal elements in the cathode lithium supplement agent, it is beneficial to reduce the side reactions of the battery and improve the energy density and cycle life of the battery.

[0161] From the comparison between Example 1 and Example 4, it can be seen that if the first slurry, lithium carbonate, glucose and Al 2 O 3 are directly mixed, compared with the technical solution of the present invention, it will be difficult to precisely control the process parameters, affecting the consistency between batches, and the uneven distribution of materials will affect the insertion and extraction efficiency of lithium ions, thereby reducing the specific capacity.

[0162] From the comparison between Example 1 and Examples 5 - 6, it can be seen that if the molar ratio of nickel element to lithium element in nickel oxyhydroxide is too small, the redox reaction of nickel element will be hindered, reducing the electrochemical activity of the material, resulting in an unstable material structure and more volume changes during the charge-discharge process, thus affecting the cycle stability; if the molar ratio of nickel element to lithium element in nickel oxyhydroxide is too large, more phase changes and structural damages will occur during the cycle of the material, reducing the capacity retention rate.

[0163] As can be seen from the comparison between Example 1 and Examples 7-8, if the molar ratio of nickel oxyhydroxide to glucose in the metal mixture is too small, excessive glucose may decompose during sintering to produce too much carbon residue or other by-products, reducing the purity of the material; if the molar ratio of nickel oxyhydroxide to glucose in the metal mixture is too large, the insufficiently reduced material may exhibit a lower lithium-ion diffusion rate and electronic conductivity during charge and discharge, causing particle breakage or agglomeration, and further reducing the performance of the material.

[0164] As can be seen from the comparison between Example 1 and Examples 9-10, if the molar ratio of nickel element in nickel oxyhydroxide to aluminum element in aluminum isopropoxide is too small, the excessive aluminum element will increase the raw material cost and reduce the resource utilization efficiency; moreover, the excessive aluminum element may form by-products in subsequent processes, increasing the difficulty of waste treatment, reducing the conductivity of the material, increasing the internal resistance of the electrode, and thus affecting the charge and discharge efficiency; if the molar ratio of nickel element in nickel oxyhydroxide to aluminum element in aluminum isopropoxide is too large, the aluminum doping is insufficient, and the improvement effect of the aluminum element on the structural stability and electrochemical performance of the material cannot be fully exerted, resulting in more structural degradation during the cycling process of the material.

[0165] As can be seen from the comparison between Example 1 and Example 11, if no tablet pressing treatment is carried out in step (3), the un-tableted material is prone to particle separation or structural loosening during charge and discharge, resulting in accelerated capacity decay.

[0166] As can be seen from the comparison between Example 1 and Comparative Example 1, if hydrogen peroxide solution is not added in step (1), that is, no oxidant is introduced, nickel hydroxide will be directly added to the subsequent mixing process, that is, directly mixed with the lithium source, which will lead to insufficient surface activity of the material, incomplete reaction with the electrolyte, increased irreversible capacity loss, reduced initial efficiency, and the electrochemical performance of the material will decline.

[0167] As can be seen from the comparison between Example 1 and Comparative Example 2, if glucose is not added in step (3), that is, no reducing agent is introduced, the insufficiently reduced material may exhibit a lower lithium-ion diffusion rate and electronic conductivity during charge and discharge, causing particle breakage or agglomeration, and further reducing the performance of the material.

[0168] It should be noted that the present invention uses the above-mentioned examples to illustrate the process method of the present invention, but the present invention is not limited to the above-mentioned process steps, that is, it does not mean that the present invention must rely on the above-mentioned process steps to be implemented. Those skilled in the art should understand that any improvement to the present invention, the equivalent substitution of the raw materials selected by the present invention, the addition of auxiliary components, the selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for preparing a positive electrode lithium supplement, characterized in that: The preparation method comprises the following steps: The metal source solution, the precipitant solution and the oxidant solution are first mixed and then reacted to obtain a first slurry, wherein the first slurry includes a metal oxyhydroxide; Performing a second mixing of the first slurry, the lithium source, the reducing agent and the coating agent to obtain a mixture; The mixed material is sintered to obtain the positive electrode lithium supplement agent.

2. The method for preparing a positive electrode lithium supplement according to claim 1, characterized in that: The metal source solution includes a nickel source solution; Preferably, the precipitant solution comprises an alkali solution; Preferably, the concentration of the alkali solution is 1-10 mol / L; Preferably, the oxidant solution comprises a hydrogen peroxide solution; Preferably, the first mixing method comprises: Adding a metal source solution, a precipitant solution and an oxidant solution into a reaction kettle in parallel; Preferably, the concentration of the metal source solution is 0.5-4 mol / L; Preferably, the flow ratio of the metal source solution, the precipitant solution and the oxidant solution is (0.8-1.2):(0.8-1.2):(0.8-1.2); Preferably, the metal oxyhydroxide comprises nickel oxyhydroxide.

3. The method for preparing a positive electrode lithium supplement according to claim 1 or 2, characterized in that: During the reaction, the rotation speed of the reaction system is 200-600 rpm; Preferably, the reaction temperature is 40-60°C; Preferably, during the reaction, the pH value of the reaction system is 8-12.

4. The method for preparing a positive electrode lithium supplement according to any one of claims 1 to 3, characterized in that: The second mixing method includes: The first slurry and the lithium source are mixed and dried to obtain a metal mixture; the metal mixture, a reducing agent and a coating agent are blended; Preferably, the lithium source includes any one of lithium carbonate, lithium hydroxide or lithium chloride, or a combination of at least two thereof; Preferably, in the metal mixture, the molar ratio of the metal element of the metal oxyhydroxide to the lithium element is 1:(2-2.2); Preferably, the reducing agent comprises any one of glucose, sucrose or starch, or a combination of at least two thereof; Preferably, the coating agent comprises any one or a combination of at least two of an aluminum source, a boron source or a magnesium source; Preferably, the aluminum source includes any one of aluminum isopropoxide, aluminum hydroxide or Al2O3 or a combination of at least two thereof; Preferably, the molar ratio of the metal oxyhydroxide to the reducing agent in the metal mixture is 1:(0.03-0.05); Preferably, the molar ratio of the metal element in the metal oxyhydroxide to the coating element in the coating agent is 1:(0.007-0.031); Preferably, the blending process is accompanied by stirring; Preferably, the stirring rate is 200-600 rpm.

5. The method for preparing a positive electrode lithium supplement according to any one of claims 1 to 4, characterized in that: Before the mixed material is sintered, the mixed material is compacted; Preferably, the sintering atmosphere is an inert atmosphere; Preferably, the sintering is multi-stage sintering, and the multi-stage sintering includes a first stage sintering and a second stage sintering; Preferably, the temperature of the first stage sintering is 250-400°C; Preferably, the holding time of the first sintering stage is 2-8h; Preferably, the temperature of the second stage sintering is 500-800°C; Preferably, the second sintering time is 3-12 hours.

6. The method for preparing a positive electrode lithium supplement according to any one of claims 1 to 5, characterized in that: The preparation method is carried out in an inert atmosphere and comprises the following steps: (1) dissolving a metal source in an aqueous solvent to obtain a metal source solution with a concentration of 0.5-4 mol / L; Adding the metal source solution, alkali solution and hydrogen peroxide solution into a reaction kettle in parallel at a flow ratio of (0.8-1.2):(0.8-1.2):(0.8-1.2), reacting at 40-60° C. to obtain a first slurry, wherein the first slurry includes a metal hydroxide oxide; The concentration of the alkali solution is 1-10 mol / L, and the concentration of the hydrogen peroxide solution is 5-15 wt %; during the reaction, the rotation speed of the reaction system is 200-600 rpm, and the pH value is 8-12; (2) mixing the first slurry and a lithium source, and then drying the mixed slurry to remove water to obtain a metal mixture; in the metal mixture, the molar ratio of the metal element of the metal hydroxide oxide to the lithium element is 1:(2-2.2); (3) crushing the metal mixture, and then stirring and blending with a reducing agent and a coating agent, the stirring rate being 200-600 rpm, to obtain a mixture; wherein the molar ratio of the metal hydroxide oxide in the metal mixture to the reducing agent is 1:(0.03-0.05), and the molar ratio of the metal element in the metal hydroxide oxide to the coating element in the coating agent is 1:(0.007-0.031); The mixed material is tableted at a pressure of 20-40 tons to obtain a tablet material; (4) performing multi-stage sintering on the pressed sheet material, firstly performing a first stage sintering at 250-400° C. for 2-8 h, and then performing a second stage sintering at 500-800° C. for 3-12 h, to obtain a sintered product; The sintered product is crushed and sieved to obtain the positive electrode lithium supplement agent.

7. A positive electrode lithium supplement, characterized in that: The positive electrode lithium replenisher is prepared by the preparation method of the positive electrode lithium replenisher according to any one of claims 1 to 6; The positive electrode lithium supplement comprises a lithium-rich active material and a coating layer coated on the surface of the lithium-rich active material.

8. The positive electrode lithium supplement according to claim 7, characterized in that: The lithium-rich active material includes Li2NiO2 and / or Li2FeO2; Preferably, the material of the coating layer includes any one of aluminum oxide, boron oxide or magnesium oxide, or a combination of at least two of them.

9. A positive electrode material, characterized in that: The positive electrode material includes a positive electrode lithium replenisher, and the positive electrode lithium replenisher is prepared by the preparation method according to any one of claims 1 to 6, or is the positive electrode lithium replenisher according to claim 7 or 8; Preferably, in the positive electrode material, the mass proportion of the positive electrode lithium supplement is 0.5-2%.

10. A lithium ion battery, characterized in that: The positive electrode sheet of the lithium-ion battery includes the positive electrode material as claimed in claim 9.

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