Process for the production of a cathode material for lithium-ion batteries

Abstract

The invention provides an environmentally friendly process for producing high capacity cathode materials for lithium ion batteries. Conventional processes for producing lithium mixed metal oxide cathode materials typically generate large amounts of wastewater that must be treated prior to discharge. The present process uses mixed metals as feedstock in a wet chemical reaction with an oxidizing agent to produce a high quality metal hydroxide precursor that can be used to produce high quality cathode materials after lithiation. As a key feature, during the precursor production process, a large portion of the aqueous solution used in the wet chemical reaction can be recycled to the reactor, resulting in little or no wastewater throughout the production process of the cathode precursor material.

Description

[0001] This application is a divisional application of the invention patent application No. 201980022125.5 entitled "Method for producing cathode material for lithium-ion batteries", filed on April 3, 2019. Technical Field

[0002] This invention relates to a method for producing a cathode material for lithium-ion batteries. Specifically, compared with existing industrial methods, the provided method relates to the relatively wastewater-free production of the cathode material. Background Technology

[0003] Rechargeable lithium-ion batteries are used as energy storage components in a wide variety of devices, including mobile phones, laptops, wireless power tools, hybrid and pure electric vehicles. In recent years, especially with the rapid growth of the electric vehicle market, the demand for high-output lithium-ion batteries has increased dramatically. The main components of a lithium-ion battery include the negative electrode, the positive electrode, and the electrolyte. During its charge and discharge cycles, lithium ions shuttle between the negative and positive electrode active materials via the electrolyte. Due to its limited specific capacity and high production and raw material costs, the positive electrode active material is typically the most expensive component in a lithium-ion battery. Therefore, selecting the right positive electrode active material is crucial for improving the performance of lithium-ion batteries and reducing their cost. This is especially true for automotive applications, given the projected phenomenal growth in this field over the next two decades.

[0004] Currently, lithium mixed metal oxides, primarily containing nickel, cobalt, manganese, and / or aluminum, as well as other necessary dopants, are the main components used to produce high-performance cathode active materials. The demand for and production of this material continues to increase significantly.

[0005] Existing industrial methods for producing these high-performance cathode materials involve two main steps: a precursor production step and a lithiation step, wherein the high-performance cathode material is, for example, a lithium mixed metal oxide. In current methods, the precursor step begins by dissolving a mixed metal sulfate in water to form an aqueous solution. This solution is then mixed in a stirred reactor with an alkaline solution, typically composed primarily of sodium hydroxide solution, to carry out a co-precipitation reaction. This reaction can be described by the following chemical equation: Me(SO4) 1+x / 2 +(2+x) NaOH --> Me(OH) 2+x +(1+x / 2)Na2SO4 (1) Where Me(OH) 2+x It is the desired precursor in solid form in the reaction system, Me represents a mixture of metal ions with different valences, and x is a factor used to provide charge balance between anions and cations.

[0006] Filtration is typically performed to separate the solid from the liquid. The resulting solid precursor is then mixed with a lithium-containing compound, and the mixture is calcined in a furnace to produce the final lithium mixed metal oxide material used as a positive electrode active material.

[0007] However, due to Me(SO4) 1+x / 2 Due to the limited solubility of NaOH, these coprecipitation methods typically generate large amounts of Na₂SO₄-containing solutions after the solid portion is removed by filtration. Because of the Na₂SO₄ content, the collected solution cannot be reused in the reaction system and must therefore be treated as wastewater.

[0008] Furthermore, ammonia is typically added to the reaction system as a chelating agent to help the precursor materials provide the correct physical properties. Therefore, in addition to salts (in most cases sodium sulfate), the wastewater may also contain ammonia, ammonium, dissolved heavy metals, fine solid particles, etc. This wastewater usually must be treated to remove ammonia and sodium sulfate before it can be discharged into the environment or recycled back into the reaction system. This wastewater treatment is very expensive and consumes a significant amount of energy. Moreover, due to its limited industrial applications and demand, sodium sulfate is generally considered a solid waste product after wastewater treatment, thus having little or no added value.

[0009] Currently, several methods have been proposed to avoid wastewater generation. For example, Chinese patent CN104409723 B, authorized in 2016, discloses an electrochemical preparation method using lithium mixed metal oxides to produce positive electrode active materials for lithium-ion batteries. According to this method, pure nickel, cobalt, and manganese metals are used as raw materials, and a green electrochemical synthesis method is used to synthesize nickel, cobalt, and manganese salt compounds by electrolysis (at ambient pressure and temperature). Ternary anode materials (LiNi) x Co y Mn z O2, where x is greater than 0 and less than 1, y is greater than 0 and less than 0.8, z is greater than 0 and less than 1, and x+y+z equals 1, can be obtained by lithium addition reaction, spray drying of the mixture, and high-temperature treatment. According to the patent specification, compared with conventional methods, the disclosed electrochemical preparation method can reduce raw material costs and energy consumption, simplify the process, reduce environmental pollution, and improve product performance.

[0010] Therefore, the electrochemical synthesis technology employed in this method aims to provide an environmentally friendly chemical approach, in which pure metals are used as the negative electrode material (without introducing impurities), thereby ensuring controllability of concentration and high purity of nickel, cobalt, and manganese ions. Furthermore, it requires zero wastewater discharge into the environment and enables continuous, large-scale production with minimal emissions. However, due to the use of organic acids, such as acetic acid and citric acid, a significant amount of carbon dioxide gas is generated during the calcination operation, potentially raising concerns about the quality of the final product (e.g., product density). Similarly, a substantial energy consumption is expected during the spray drying operation to evaporate the water present in the system.

[0011] A similar method can be found in Chinese patent CN 102219265 A (2011), in which nitrates are used instead of organic acids and thermal decomposition is carried out at high temperature under a controlled atmosphere.

[0012] Another method for manufacturing lithium mixed metal oxides for lithium-ion batteries without significant wastewater generation is the "sol-gel" method described by Ching-Hsiang Chen et al. in the Journal of Power Sources, 146, 626–629 (2005). In this method, layered LiNi is synthesized via a sol-gel process using citric acid as a chelating agent. x Co 1-2x Mn x O2 powder. Stoichiometric amounts of lithium acetate, manganese acetate, nickel acetate, and cobalt nitrate were selected as raw materials for preparing the precursor. All salts were dissolved in an appropriate amount of distilled water, and citric acid was added dropwise with continuous stirring. After all salts were dissolved, the solution temperature was raised to 80-90°C, and stirring continued until a transparent, viscous gel was formed. The gel was vacuum dried at 120°C for 2 hours to obtain the precursor powder. This precursor powder was decomposed in an oxygen stream at 450°C for 4 hours, then ground into a fine powder, and calcined at 900°C for 12 hours under oxygen flow conditions. The heating and cooling rate was maintained at 2°C per minute.

[0013] Similarly, due to the need to evaporate a large amount of water, and the fact that organic acids and / or nitrates must participate and decompose during calcination, this method is expected to have high energy consumption and poor density of the final material.

[0014] Another paper by Huaquan Lu et al. in Solid State Ionics; 249-250, (2013) also describes a method for preparing lithium mixed metal oxides using a sol-gel process, in which only nitrates are used instead of a mixture of organic salts and nitrates. However, it suffers from essentially the same problems as the previous sol-gel method. Summary of the Invention

[0015] To address these problems, it is advantageous that the present invention provides a method for producing cathode materials for batteries, particularly lithium-ion batteries, that improves and / or solves the aforementioned wastewater problems arising from currently known methods for preparing lithium mixed metal oxides. Therefore, it is desirable to provide a suitable method that generates little or no wastewater. That is, the desired method provides a system in which substantially all liquid portions from the reaction can or can be completely recycled back into the reaction system without any significant treatment. Furthermore, in the desired method, little or no evaporation of water and / or decomposition of organic matter or nitrates are required during the final high-temperature treatment / calcination process.

[0016] As described below, the method of the present invention provides at least in part or entirely the above-mentioned advantages, as well as other inherent objects and objectives.

[0017] Therefore, in a first aspect, the present invention provides a chemical method for producing lithium mixed metal oxides as positive electrode active materials for use in lithium-ion secondary batteries. The method comprises two main steps: a wet chemical process for manufacturing the precursor and a solid-state reaction known as "lithiation" for manufacturing the final positive electrode material.

[0018] In the method of the present invention, a raw material, preferably in metallic form, is added to an aqueous reaction system. At least one oxidizing agent, such as oxygen, nitrate, or nitric acid, is added to the aqueous reaction system to react with the metal, thereby forming a metal hydroxide.

[0019] In operation, the reaction system typically includes at least one stirred tank and / or reactor in which an aqueous slurry of reactants and resulting products is mixed. A portion of the slurry is removed, and preferably any unreacted feed metal is removed from the slurry, and recycled to the reactor. In this regard, if necessary, the tank or reactor may be equipped with a separation device, such as a magnetic separator, to remove and recover unreacted metal feed from the oxidized metal hydroxide. After the unreacted metal is recovered, the remaining slurry undergoes a solid-liquid separation operation. Preferably, a portion of the liquid filtrate from this filtration is recycled to the reaction system for further reaction. The solid portion is collected and removed as precursor material. The collected precursor material is then subjected to a lithiation stage.

[0020] It should be noted that, in order to initiate the reaction system, an artificial “seed” portion can be prepared and used to start the reaction, wherein the “seed” portion preferably has a desired metal hydroxide composition that is substantially the same as or similar to the collected precursor material.

[0021] Furthermore, an artificial solution with the same or similar composition as the desired filtrate liquid can be prepared and used to initiate the reaction until a suitable filtrate is produced from the filtration system.

[0022] In the lithiation stage, the final positive electrode active material is obtained by mixing the solid precursor material produced above with a lithium-containing compound and optional other dopants, followed by calcination. Additional surface treatments, and optional additional calcination treatments, may then be performed if desired.

[0023] Therefore, the present invention provides, in its preferred form, a method for producing lithium mixed metal oxides as positive electrode active materials for the production of lithium-ion batteries. This method comprises two main steps: a precursor preparation step and a lithiation step, wherein: A) In the precursor preparation step, a selected metal in solid metallic form is added to a stirred reaction system comprising a mixture of the solid metal particles in an aqueous solution and optionally seeded metal hydroxide particles, and at least one oxidant, wherein the oxidant is preferably selected from oxygen, metal nitrates, and nitric acid or combinations thereof. The oxidant is added to a reactor to oxidize the metal particles under alkaline conditions, wherein the entire oxidation reaction is represented by the following equation: xMe+yMe'(NO3) n +zHNO3+(0.25xm-2yn-2z)O2+(0.5xm+2yn+z)H2O -->Me x Me' y (OH) (xm+yn) +(yn+z)NH3 Me represents at least one metal selected from nickel, manganese, cobalt, aluminum and magnesium in metallic form; Me' represents at least one metal selected from nickel, manganese, cobalt, aluminum, magnesium, zirconium, yttrium, titanium, vanadium and molybdenum in ionic form. x Me' y (OH) (xm+yn) The precursor product is represented by x and y, which are the mole fractions of metals Me and Me', respectively. m is the molar weighted average valence of the mixed metal Me in the precursor product, n is the molar weighted average valence of the mixed metal Me' in ionic form in the reactants, and z is the mole fraction of HNO3 added to the reaction system. xm ≥ 8yn + 8z, x + y = 1, 1 ≥ x > 0, y ≥ 0, z ≥ 0. The slurry obtained from the oxidation reaction is removed from the reactor, unreacted metals are removed from the slurry and recycled back to the reaction system, and then solid-liquid separation is performed. The collected solid material is used as the collected precursor product, and the liquid material is preferably recycled directly back to the reaction system without any treatment. B) A lithiation step in which the collected precursor product is mixed with a lithium-containing compound and optional other dopants to produce a final mixture, which is then calcined to obtain a positive electrode active material.

[0024] Therefore, the present invention provides a method for preparing lithium mixed metal oxides while generating little or no wastewater. That is, the present invention provides a system in which substantially all liquid portions from the reaction are, or can be, completely recycled back to the reaction system without any wastewater treatment.

[0025] In addition, during the final high-temperature treatment and / or calcination process, there is little or no need for water evaporation and / or decomposition of organic acids or nitrates.

[0026] Among other features, it should be noted that although the method of the present invention can be carried out in batches, it is particularly suitable for being carried out in a substantially continuous manner.

[0027] In a second aspect, the present invention also provides a cathode material precursor product, wherein a suitable cathode material precursor of the present invention is prepared by the method described above, and wherein these particles are particularly preferably prepared by a continuous method, preferably in the manner described herein, using the single-stage reaction system of the present invention. The present invention also provides the final cathode active material of the present invention produced by the methods described herein, and the cathode produced therefrom.

[0028] In a third aspect, the present invention also provides a battery, wherein the positive electrode of the battery is produced by the chemical method of the present invention described above. Invention Details It is well known that metal oxides or hydroxides can be formed by corrosion processes, such as metal oxidation in aqueous solutions or under humid conditions. For the preparation of precursor hydroxide materials from pure metals, this principle is preferably used in the first step of the invention, wherein the metal corrosion / oxidation reaction and the co-precipitation reaction occur simultaneously, and preferably within the same reactor. The overall reaction is shown in the following equation: xMe+yMe'(NO3) n +zHNO3+(0.25xm-2yn-2z)O2+(0.5xm+2yn+z)H2O -->Me x Me' y (OH) (xm+yn) +(yn+z)NH3 Wherein Me represents at least one metal selected from nickel, manganese, cobalt, aluminum and magnesium, preferably in metallic form; Me' represents at least one metal selected from nickel, manganese, cobalt, aluminum, magnesium, zirconium, yttrium, titanium, vanadium and molybdenum, preferably in ionic form; Me x Me' y (OH)(xm+yn) The product represents the precursor; x and y are the mole fractions of metals Me and Me', respectively, where m is the mole weighted average valence of the mixed metal Me in the precursor, n is the mole weighted average valence of the mixed metal Me' in ionic form in the reactants, and z is the mole fraction of HNO3 added to the reaction system; where xm≥8yn+8z, x+y=1, 1≥x>0, y≥0, and z≥0.

[0030] Oxygen is preferred as an oxidant because it typically does not produce any noticeable byproducts during the reaction. Oxygen can be provided from pure oxygen sources and / or as oxygen contained in other gases, such as oxygen in the air.

[0031] Certain metal nitrates may be included as oxidants for use with metal elements that do not readily react with oxygen, or for metal elements that are difficult to handle in processing operations, such as during the stirring process of homogeneous mixing or during the magnetic separation process in their metallic form.

[0032] Nitric acid can be used as an additional oxidant to control the co-precipitation reaction of metal nitrates. When using nitrates and nitric acid, ammonia is the only byproduct. However, the ammonia produced in the reaction is gaseous and therefore does not remain in the reaction system during operation. Therefore, in the above-described wet chemical method for preparing the precursor, no additional or new compounds are added to the liquid after solid-liquid separation. Consequently, up to at least 75%, more preferably up to at least 90%, and even more preferably up to 100% of the liquid can be directly recycled back into the reaction system without any adverse effect on the overall reaction.

[0033] The ammonia produced can be collected as a useful chemical or chemical precursor for use in other industries, such as the fertilizer industry.

[0034] Depending on the reactor conditions, other oxidants may be used.

[0035] To obtain high-quality products with constant properties, it is preferable to operate the reactions described herein in a continuous mode, whereby the reactions will reach steady-state conditions. This provides better control over the resulting chemical composition. In a preferred method, an artificial solution having the same or similar composition as the liquid in the reaction system is prepared and used to initiate the reaction, and this artificial solution is used until the liquid produced from the solid-liquid separation operation resembles the artificial solution.

[0036] The pH of the reaction slurry is preferably 7.5 to 13, more preferably 8 to 12. The pH of the solution is preferably adjusted by adding an acid selected from sulfuric acid, nitric acid, or acetic acid and / or by adding an alkaline material selected from lithium hydroxide or lithium oxide, sodium hydroxide or sodium oxide, potassium hydroxide or potassium oxide, and ammonia. Preferably, the pH is adjusted by adding an acid such as sulfuric acid or nitric acid and / or by adding an alkaline material such as lithium hydroxide or sodium hydroxide. Generally, it should be noted that a lower pH value can lead to a lower quality of the coprecipitated product, while a higher pH value may lead to passivation of the metal during the corrosion reaction.

[0037] The preferred reaction temperature is within the range of 20°C to the boiling point of the reaction slurry, or more preferably 20°C to 100°C. More preferably, the reaction temperature is 30°C to 80°C.

[0038] Maintaining acceptable electrical conductivity in the reaction system can also be important for controlling corrosion / oxidation reactions. Therefore, the reaction slurry preferably also contains dissolved salts to form an electrolyte for conducting electricity. These salts can include salts having cations selected from sodium, lithium, potassium, and ammonium, such as sulfates, acetates, nitrates, chlorates, etc. These salts are typically and preferably reusable in a recirculating liquid, which is collected after liquid-solid separation.

[0039] The reaction slurry may also contain dissolved complexing agents, such as a mixture of ammonia and ammonium, which can chelate metal ions in aqueous solution. The general function of these complexing or chelating agents is preferably to control the properties of the coprecipitated products and / or to make the metal more reactive to corrosion.

[0040] The preparation method of the cathode material may also include a step of “reactivating” unreacted raw material metals, wherein the unreacted raw material metals are collected from the slurry, for example, by a magnetic separation step. This may include grinding and / or washing the materials using a liquid, typically with a decreased pH value, obtained from a liquid-solid separation step.

[0041] In addition, the method may also include the step of introducing solid particles with the same or similar composition as the precursor product but with a smaller particle size into the reaction system at the start of the reaction and / or during the reaction.

[0042] Therefore, the method of the present invention is preferably used to produce cathode material precursor particles with a composition similar to that of prior art cathode material precursors, having a uniform elemental distribution within each particle, wherein the metals are added in a stable and continuous manner in a single-stage reaction system. However, the method can also be applied to produce particles with a non-uniform elemental distribution within each particle by adding different metals at different times, for example, cathode material precursor particles with a gradient or stratification in a multi-stage reaction system. In such a multi-stage system, each stage can deposit a layer of material with a different composition to achieve different functions. For example, the core region of the cathode material particle can be enriched with nickel for higher capacity, while the surface area can be enriched with manganese, magnesium, or aluminum to have a stable interface with the electrolyte in a lithium-ion battery.

[0043] Therefore, this method provides a system in which metal is continuously added at the same ratio at all times to produce a precursor with a uniform elemental distribution in each particle, or in which metal is continuously added at different ratios over time to produce a precursor with a non-uniform elemental distribution in each particle.

[0044] The precursor compound is then mixed with a lithium-containing compound and calcined, and optionally surface-treated, to obtain the final positive electrode active material to be produced according to the present invention. This process is commonly referred to as lithiation, and it is typically carried out as a solid-state reaction, depending on the chemical composition of the final material, preferably at a temperature between 600°C and 1100°C. Oxidation conditions may also be required as part of the lithiation reaction step. Air, oxygen, and nitrates are preferably used as oxidants.

[0045] In most applications, lithium hydroxide and lithium carbonate, with or without water of crystallization, are preferred as lithium sources.

[0046] Following lithiation, slight crushing / grinding may be necessary during size reduction operations to break up the loose clumps formed during the lithiation step. Then, optional surface treatments and coatings to stabilize the material's surface are sometimes required or desired, such as washing to remove additional lithium hydroxide / lithium carbonate and other impurities. Therefore, after calcination, the cathode material can be further processed, including washing to remove additional lithium and other unwanted impurities, and coating to improve the cathode material's performance during battery production and / or battery application. Additional optional calcination steps may also be performed if required or desired. Attached Figure Description

[0047] The method of the present invention will now be described by way of example only, with reference to the accompanying drawings, wherein: Figure 1These are SEM images of precursor materials produced using the method of this invention; Figure 2 This is the XRD pattern of the precursor material produced using the method of this invention; Figure 3 The charging and discharging curves of the final positive electrode active material produced using the method of this invention in half-cell testing; and Figure 4 This is a process flow diagram showing a preferred embodiment of the method of the present invention.

[0048] In the accompanying drawings, the same reference numerals denote the same elements. Detailed Implementation

[0049] From the following embodiments, the novel features considered to be features of the present invention will be better understood, wherein the preferred embodiments of the invention are described hereby by way of example only, with respect to their structure, organization, use and operation, as well as their purpose and advantages.

[0050] However, it should be clearly understood that these embodiments and figures are for illustrative and descriptive purposes only and are not intended to limit the invention. Furthermore, unless otherwise specifically indicated, it should be understood that all features described herein can be combined with the above aspects in any combination.

[0051] Example The following embodiments describe the method of the present invention according to a preferred embodiment and the properties of the resulting materials.

[0052] Example 1 according to Figure 4 In a production method typically indicated by 10, a 1.1 L aqueous solution was prepared and transferred to a 2 L reaction vessel using a stirring and heating system. This aqueous solution contained 1 mole of sodium sulfate as the electrolyte and 50 mL of 28% ammonia solution as a complexing agent. The solution was stirred at approximately 750 rpm while being heated to 60°C. Approximately 150 g of mixed metal hydroxide powder was added to the reaction vessel as a seed component, wherein the metal hydroxide powder mainly contained nickel hydroxide and a very small amount of cobalt hydroxide (less than 5% cobalt by molar weight).

[0053] The pH of the aqueous solution was adjusted to 10.5 by adding ammonia and sodium hydroxide to the reaction vessel. An additional 87 grams of nickel powder and 13 grams of cobalt powder were also added to the reaction vessel. After approximately 60 minutes, an additional 7.2 grams of nickel powder and 1.08 grams of cobalt powder were added to the reaction vessel every 60 minutes. This formed the starting material for the reaction.

[0054] Furthermore, oxygen, acting as an oxidant, is continuously added to the reaction vessel at a flow rate of approximately 26.5 mL per minute.

[0055] Approximately 50 mL of the resulting slurry is collected from the reaction vessel each hour and subjected to magnetic separation to separate unreacted magnetic raw material metal from the metal hydroxide. The separated unreacted magnetic raw material metal is returned to the reaction vessel. The non-magnetic solid fraction is then filtered from the remaining slurry and washed with water. All remaining liquid filtrate, along with the wash water, is returned to the reaction vessel.

[0056] The solid fraction obtained from the filtration step is then used as a chemical precursor for use in this invention and dried at about 100°C for about 5 hours.

[0057] The above operation was repeated continuously for 100 hours. After reaching steady-state conditions, the dried solid material from the last 24 hours of operation was collected as a good precursor material sample. The particle size D50 of the collected precursor material was approximately 10 micrometers. The tap density of the collected precursor material was approximately 2.1 g / cm³. 3 And as Figure 1 The scanning electron microscope (SEM) image shown appears as spherical particles with fine primary particles.

[0058] Chemical analysis results show that the chemical composition of the product finally reached the steady state of the target element molar ratio Ni : Co = 0.87 : 0.13.

[0059] SEM / EDX (scanning electron microscopy with energy-dispersive X-ray diffraction) cross-sectional examination of the collected material showed that all target metallic elements were uniformly distributed within each precursor particle. Figure 2 As shown, the X-ray diffraction (XRD) results also indicate that the obtained product is a single phase.

[0060] Example 2 Similar to Example 1, approximately 1.2 L of an aqueous solution was prepared and transferred to a 2 L reaction vessel. This aqueous solution contained approximately 1 M ammonium nitrate and 0.5 M sodium nitrate. The solution was stirred at approximately 700 rpm while being heated to approximately 60 °C. This temperature was maintained by a heating mantle integrated with a temperature controller and a J-type thermocouple. The pH of the aqueous solution was then adjusted to approximately 10.0 at 60 °C by adding ammonia to the reaction vessel.

[0061] Approximately 135 grams of nickel metal powder and 15 grams of cobalt metal powder were added to the reaction vessel. Additionally, approximately 150 grams of a mixed metal hydroxide powder, comprising nickel hydroxide and cobalt hydroxide in an atomic ratio of approximately 0.9:0.1, was added to the reaction vessel.

[0062] After approximately 60 minutes, 7.2 g of nickel metal powder and 0.8 g of cobalt metal powder were added to the reaction vessel every hour. Additionally, approximately 2% aluminum was added in the form of aluminum nitrate, prepared by dissolving aluminum hydroxide in 68% nitric acid. Nitric acid and oxygen were also simultaneously introduced into the reaction vessel at flow rates of 0.04 ml / min and 18 ml / min, respectively.

[0063] Samples were collected every three hours, using 100 ml of slurry. Magnetic separation was performed, and the magnetic fraction was returned to the reaction vessel. The non-magnetic fraction was filtered out and washed with distilled water, and all filtrate, along with the wash water, was returned to the reaction vessel.

[0064] The solid filter cake from the filtration operation was dried at about 100°C for about 6 hours as a precursor.

[0065] The above sampling operation was repeated continuously for 100 hours, and the dried solids collected in the last 24 hours were used as good samples of precursor materials. Chemical analysis results showed that the chemical composition of the product reached a stable state with the target atomic ratio of Ni:Co:Al = 0.865:0.097:0.038.

[0066] Example 3 Approximately 6 grams of lithium hydroxide monohydrate was selected and manually granulated using a mortar and pestle to reduce particle size. Then, approximately 1 gram of this granulated lithium hydroxide monohydrate was mixed with 2 grams of the precursor material collected in Example 1, and the mixture was transferred to an alumina crucible. The mixture was calcined in a tube furnace. During calcination, oxygen was continuously flowed through the tube furnace at a rate of approximately 220 mL per minute.

[0067] The temperature was increased to 800°C at a rate of 10°C per minute. This temperature was maintained at 800°C for 10 hours, then decreased at a rate of approximately 5°C per minute. After calcination, the collected solids were manually granulated to break up agglomerates, and then placed in a beaker containing approximately 30 mL of cold water at approximately 5°C. After stirring for approximately 2 minutes, the mixture was rapidly filtered, and the collected solids were placed in an alumina crucible and calcined again in a tube furnace at approximately 710°C for 5 hours. The resulting calcined solid composition was collected as the final positive electrode active product.

[0068] Example 4 Half-cell tests of a button cell battery were conducted using the final positive electrode active product collected from Example 3 as the positive electrode active material and lithium metal foil as the negative electrode active material. The positive electrode was prepared using a composition of 90% final positive electrode active product, 6% carbon black, and 4% PVDF (polyvinylidene fluoride). The electrolyte used in the tests was 1M LiPF6 in EC (ethylene carbonate), DEC (diethyl carbonate), and EMC (ethyl methyl carbonate), with an EC / DEC / EMC volume ratio of 1:1:1. The first charge and first discharge voltages were 3V to 4.3V, with a rate of 0.05C (where 1C = 150 mAh / g).

[0069] Figure 3 The results of the first cycle of the test are shown. The first discharge capacity was approximately 192 mAh / g, and the coulombic efficiency was approximately 88%.

[0070] Therefore, it is evident that, according to the present invention, methods, products, and batteries have been provided that fully satisfy the aforementioned objectives, purposes, and advantages. Specific embodiments of the invention have thus been described; it should be understood that alternatives, modifications, and variations may be suggested to those skilled in the art, and it is intended that this specification include all such alternatives, modifications, and variations that fall within the scope of the appended claims.

Claims

1. A method for producing lithium mixed metal oxide cathode active materials for lithium-ion batteries, comprising: In the precursor preparation step, solid metal particles of the selected metal are added to the reaction system under alkaline conditions. The system comprises a mixture containing the solid metal particles, seed mixed metal hydroxide particles, an aqueous solution, and an oxidant including oxygen to simultaneously oxidize the solid metal particles and precipitate the precursor product, thereby forming a slurry containing the precursor product and unreacted solid metal particles. The selected metal is two or more metals selected from the group consisting of nickel, manganese, cobalt, aluminum, and magnesium. The precursor preparation step includes adjusting the pH to a range of 8 to 12, and the seed mixed metal hydroxide particles contain at least two ionic metals selected from the group consisting of nickel, manganese, cobalt, aluminum, magnesium, zirconium, yttrium, titanium, vanadium, and molybdenum. In the recycling step, the unreacted solid metal particles are separated from the slurry to form a first solution, the precursor product is collected from the first solution to form a second solution, and the unreacted solid metal particles and the second solution are directly recycled back to the reaction system. and In the lithiation step, the collected precursor product is mixed with a lithium-containing compound to produce a final mixture, and the final mixture is calcined to obtain a lithium mixed metal oxide cathode active material.

2. The method according to claim 1, wherein the precursor preparation step is carried out at a temperature from 20°C to the boiling point of the slurry.

3. The method according to claim 1, wherein the precursor preparation step further comprises adding at least one of sulfuric acid, nitric acid, acetic acid, lithium hydroxide or oxide, sodium hydroxide or oxide, potassium hydroxide or oxide, and ammonia to the mixture.

4. The method of claim 1, wherein the aqueous solution further comprises dissolved salt.

5. The method according to claim 4, wherein the dissolved salt is selected from sulfates, acetates, nitrates and chlorates containing cations selected from sodium, lithium, potassium and ammonium.

6. The method of claim 1, wherein the aqueous solution further comprises a complexing agent.

7. The method of claim 6, wherein the complexing agent comprises a mixture of ammonia and ammonium.

8. The method of claim 1, wherein the oxidant further comprises air, a metal nitrate, or nitric acid, or a combination thereof.

9. The method according to claim 8, wherein the metal nitrate is selected from at least one of ammonium nitrate and sodium nitrate.

10. The method of claim 1, wherein the oxidant is oxygen.

11. The method of claim 1, wherein the reaction system comprises at least one stirred tank.

12. The method of claim 1, wherein the recycling step further comprises reactivating the separated unreacted solid metal particles by grinding and / or washing.

13. The method according to any one of claims 1 to 12, wherein the precursor preparation step is carried out under steady-state conditions and in continuous operation.

14. The method of claim 13, wherein each of the selected metal elements is added continuously at the same ratio in the precursor preparation step to produce the precursor product having a uniform elemental distribution in each particle of the precursor product.

15. The method of claim 1, wherein at least 90% of the second solution is directly recycled to the reaction system.

16. The method of claim 1, wherein in the precursor preparation step, solid particles having the same or similar composition as the precursor product and a smaller particle size than the precursor product are introduced into the reaction system.

17. The method of claim 1, wherein an artificial solution having the same or similar composition as the aqueous solution is used in the precursor preparation step until a suitable second solution is produced by the recycling step and recycled back to the reaction system.

18. The method of claim 1, further comprising drying the collected precursor product.

19. The method of claim 18, wherein the lithium mixed metal oxide cathode active material is subjected to a crushing operation.

20. The method according to claim 1, wherein the lithium-containing compound is selected from lithium hydroxide and lithium carbonate.

21. The method of claim 1, wherein the final mixture is calcined at a temperature of 600°C to 1100°C.

22. The method of claim 1, wherein the lithium mixed metal oxide cathode material is subjected to further treatment selected from washing, coating, and combinations thereof.

23. A lithium mixed metal oxide product used as a positive electrode active material for a lithium-ion secondary battery, wherein the mixed metal oxide product is prepared according to the method according to any one of claims 1 to 22.

24. A secondary lithium battery comprising a lithium metal oxide as a positive electrode material, wherein the positive electrode material is a mixed metal oxide product prepared according to any one of claims 1 to 22.

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