A method for preparing low-cost lithium cobalt oxide cathode material based on slurry spray combustion

Abstract

The application relates to the technical field of lithium ion battery material preparation, and discloses a method for preparing low-cost lithium cobaltate positive materials based on slurry spraying combustion, which comprises the following steps: a cobalt source, a lithium source, carbon-containing fuel, a high-molecular dispersant and water are mixed and ground to prepare combustion slurry; the combustion slurry is delivered to an atomizer, atomized to form liquid drops and enters a combustion chamber with a carrier gas; the carbon-containing fuel is ignited by an ignition device, in-situ combustion reaction is carried out under the condition of oxygen-containing gas, the liquid drops rapidly complete solid-phase synthesis in a high-temperature microenvironment; the gas-solid mixture generated in the reaction enters a cooling area to be forcedly cooled, and the solid-state powder is collected to obtain the lithium cobaltate positive material. The in-situ deflagration heating of the carbon-containing fuel significantly shortens the reaction period and reduces the manufacturing energy consumption, meanwhile, the forced quenching process limits the grain coarsening and lithium element volatilization, improves the consistency of the material, and realizes the low-cost continuous production of the lithium cobaltate positive material.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery material preparation technology, specifically a method for preparing low-cost lithium cobalt oxide cathode material based on slurry spray combustion. Background Technology

[0002] Lithium cobalt oxide is widely used as a cathode material in lithium-ion batteries for consumer electronics and other fields due to its high tap density and stable charge / discharge voltage platform. As market demands for cost control in lithium batteries increase, the low-cost, high-efficiency preparation of high-quality lithium cobalt oxide materials has become a key research focus in this field.

[0003] Currently, the industrial production of lithium cobalt oxide cathode materials generally employs a high-temperature solid-state synthesis method. This method typically involves mechanically mixing cobalt and lithium sources, followed by high-temperature calcination in a heated furnace. In actual production processes, the reaction between these solid particles is limited by macroscopic solid-state diffusion mass transfer mechanisms, resulting in a slow mass exchange rate between reactants. To ensure sufficient crystal phase reconstruction and synthesis reactions, the materials must be calcined at high temperatures for more than ten hours, consuming a significant amount of energy and directly increasing production costs.

[0004] In traditional calcination processes, external heating relies on heat conduction from the surface inwards, which can easily lead to uneven thermal distribution in large-scale reaction equipment. Excessively high local temperatures can cause lithium volatilization and loss, as well as excessive growth of primary grains, while locally low temperatures can result in incomplete reactions and the presence of impurity phases in the product. Furthermore, conventional dry mechanical mixing struggles to achieve uniform dispersion of cobalt and lithium at the submicron scale, further affecting the consistency of the final material's electrochemical performance. To address these shortcomings, existing processes typically require multiple grinding and secondary sintering steps. This not only increases the complexity of the process and the investment in equipment but also fails to fundamentally address the long solid-state reaction cycle and high energy consumption, limiting further reductions in the manufacturing cost of lithium cobalt oxide materials.

[0005] Therefore, this invention proposes a method for preparing low-cost lithium cobalt oxide cathode materials based on slurry spray combustion to overcome the shortcomings of existing technologies. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a method for preparing low-cost lithium cobalt oxide cathode materials based on slurry spray combustion. This method solves the problems of long reaction cycles, high energy consumption, uneven material mixing leading to high production costs and poor product consistency in existing solid-phase synthesis processes for lithium cobalt oxide cathode materials.

[0007] To achieve the above objectives, the present invention provides the following technical solution: a method for preparing low-cost lithium cobalt oxide cathode materials based on slurry spray combustion, comprising the following steps:

[0008] Raw materials including cobalt source, lithium source, carbon-containing fuel, polymeric dispersant and water are mixed and ground to prepare a combustion slurry, and the prepared combustion slurry is stored in a slurry storage tank.

[0009] The carbon-containing fuel is selected from one or more of coke powder, biomass charcoal powder and sucrose, and the solid content of the combustion slurry is 20% to 70%, the apparent viscosity at room temperature is 200 to 8000 mPa·s, and the median particle size D50 is 3.5 to 8.0 micrometers.

[0010] The combustion slurry is delivered to the atomizer by a slurry pump, atomized into droplets, and enters the combustion chamber with the carrier gas. The combustion chamber includes at least a pre-evaporation and concentration zone, a combustion phase formation zone, and a cooling zone along the movement direction of the droplets. The droplets first evaporate some water and shrink in the pre-evaporation and concentration zone, and then enter the combustion phase formation zone.

[0011] The carbon-containing fuel is ignited by an initial heat source provided by an ignition device, and a combustion reaction is carried out under the condition that oxygen-containing gas is introduced through the air supply port, so that the temperature of the high-temperature reaction environment in the combustion chamber is 850-1200°C, and the residence time of the atomized droplets in the combustion chamber is controlled to be 0.5-10 seconds.

[0012] The gas-solid mixture generated by the reaction enters a cooling zone with a cooling jacket for forced cooling. Within 2 seconds, the dust-laden high-temperature airflow is rapidly cooled to below 200°C. The cooled solid powder is collected by a product collector to obtain the lithium cobalt oxide cathode material, while the exhaust gas is introduced into the exhaust gas treatment system.

[0013] By employing the above technical solution, cobalt source, lithium source, and carbon-containing fuel are co-dispersed in the same slurry system, and droplets containing reactants and fuel are formed through spraying. This transforms the lithium cobalt oxide synthesis reaction from a traditional large-volume solid-phase particle reaction to a droplet-scale dispersion reaction. A polymeric dispersant keeps the cobalt source, lithium source, and carbon-containing fuel suspended and dispersed in the aqueous phase, reducing agglomeration and sedimentation between raw material particles. This ensures that the atomized droplets simultaneously contain the cobalt, lithium, and heating components required for the phase formation reaction.

[0014] This invention divides the droplet reaction process within the combustion chamber into three consecutive stages: pre-evaporation and concentration, combustion phase formation, and rapid cooling. Upon entering the pre-evaporation and concentration zone, water first absorbs heat and evaporates, reducing the droplet volume. The cobalt source, lithium source, and carbon-containing fuel are concentrated within the droplet, shortening the interparticle spacing. This process reduces the outward expansion of the droplet due to the instantaneous vaporization of water in the subsequent high-temperature reaction stage, thus improving the contact efficiency of the reactants within the droplet. The droplet then enters the combustion phase formation zone, where the carbon-containing fuel undergoes an in-situ exothermic oxidation reaction with the participation of oxygen-containing gas. The heat of reaction directly acts on the cobalt and lithium sources within the droplet, enabling them to reach the temperature required for lithium cobalt oxide phase formation in a short time.

[0015] The first stage involves the formation and preheating of homogeneous micro-droplets. Through the steric hindrance and charge repulsion of the polymeric dispersant, the insoluble cobalt source and carbon-containing fuel form a stable, dispersed suspension in the aqueous phase, while some soluble lithium source dissolves in the aqueous phase, creating a homogeneous solid-liquid combustion slurry. After atomization, the slurry forms spatially dispersed micron-sized droplets, each droplet constituting an independent micro-unit of chemical reaction. Upon entering the combustion chamber, the water absorbs heat from the environment at high temperatures and rapidly vaporizes, causing the droplets to shrink in volume and become denser internally.

[0016] The second stage is in-situ micro-regional deflagration. As the water in the droplet evaporates completely, the exposed carbonaceous fuel reaches its ignition point. With the participation of oxygen-containing gas, the carbonaceous fuel undergoes a violent exothermic oxidation reaction inside or on the surface of the droplet.

[0017] The in-situ combustion of fuel instantaneously releases a large amount of heat into the droplet micro-units, forming a local high-temperature microenvironment. This overcomes the thermal resistance effect of heat conduction from the surface to the interior during traditional external heating, and enables rapid heating of the reactants.

[0018] The third stage is solid-state in-situ synthesis. Within the high-temperature field provided by in-situ combustion, the cobalt and lithium sources undergo thermal decomposition and lattice reconstruction at the micro-nano scale.

[0019] Because the reactants are dispersed through grinding before spraying to achieve submicron-level physical contact, the diffusion path of solid-phase ions is shortened, allowing the synthesis of layered lithium cobalt oxide to be completed within seconds. This extremely short reaction time limits excessive grain boundary migration and grain coarsening.

[0020] The fourth stage is forced quenching. The high-temperature gas-solid mixture that has completed the phase transformation then enters the cooling zone, where heat exchange is carried out using a cooling jacket. The forced cooling process freezes the crystal structure of the material in a high-temperature stable state, avoiding the loss of lithium elements due to volatilization or the degradation of the crystal form to the spinel phase that may occur if lithium cobalt oxide is kept at high temperatures for a long time.

[0021] The pre-evaporation concentration zone is used to reduce the interference of moisture in the droplets on the combustion phase formation stage. The combustion phase formation zone is used to complete the in-situ exothermic reaction of carbon-containing fuels and the rapid phase formation of lithium cobalt oxide. The cooling zone is used to terminate the high-temperature process and stabilize the product state. This process path continuously connects slurry dispersion, droplet concentration, in-situ heating, short-time phase formation and forced cooling, which can reduce the dependence of traditional solid reactors on long-term external heating.

[0022] Preferably, the combustion slurry is prepared from raw materials comprising the following parts by weight:

[0023] 100-150 parts of cobalt source;

[0024] Lithium source: 22-90 parts;

[0025] Carbon-containing fuels: 10–76 parts;

[0026] 0.5 to 4 parts of polymeric dispersant;

[0027] Water 65-1060 parts.

[0028] This ratio ensures the required stoichiometric ratio of cobalt and lithium within the system, and the heat released from the combustion of carbon-containing fuel at this dosage is sufficient to maintain the required phase formation temperature of the system. Controlling the water volume within the aforementioned range balances the rheological properties of the slurry with the latent heat energy required for evaporation and dewatering.

[0029] Preferably, the cobalt source is selected from one or more of cobalt(II) oxide, cobalt(III) oxide, cobalt(II) nitrate, and cobalt(II) acetate, and the lithium source is selected from one or more of lithium carbonate, lithium nitrate, and lithium hydroxide.

[0030] The synthesis reaction is controlled by utilizing the physicochemical properties of different cobalt and lithium sources. Using soluble salts such as nitrates can improve the mixing uniformity of the reaction components at the molecular level. When heated, they can release oxygen or nitrogen oxides in situ, which can assist in pore formation and provide a strong local oxidizing atmosphere in micro-regions, which is conducive to the oxidation of cobalt to the trivalent state. Using insoluble raw materials such as oxides can increase the overall solid content of the slurry and reduce the energy consumption for dehydration.

[0031] Preferably, the carbon-containing fuel is selected from one or more of coke powder, biochar powder, and sucrose, and the polymeric dispersant is selected from one or more of sodium polyacrylate, sodium carboxymethyl cellulose, polyvinyl alcohol, and sodium lignosulfonate.

[0032] Coke powder and biochar powder have high calorific value, providing a stable and sustained combustion heat field; sucrose, as an organic carbon source, has a low ignition point and acts as a skeletal support during the early dehydration and carbonization process. Various selected polymeric dispersants, by adsorbing onto the particle surface to change the surface potential or increasing the viscosity of the liquid phase system, prevent the sedimentation and stratification of high-density solid particles, ensuring the continuity of pumping and atomization operations.

[0033] Preferably, the raw materials of the combustion slurry also include modified additives;

[0034] The amount of the modified additive is 1 to 3.9 parts;

[0035] The modified additive is selected from one or more of magnesium nitrate hexahydrate, tetraethyl orthosilicate, titanium isopropoxide, and nano-alumina.

[0036] The process of spray combustion achieves integrated operation of precursor doping or surface coating. In the in-situ reaction system of droplets, the modified additives are transformed into corresponding metal or non-metal oxides upon heating. Some of these oxides enter the lattice of lithium cobalt oxide to achieve bulk doping, while others segregate on the particle surface during droplet shrinkage to form a protective film.

[0037] Preferably, the combustion chamber further includes an oxidation repair zone located between the combustion phase formation zone and the cooling zone;

[0038] The combustion phase-forming zone is provided with a primary gas supply port, through which oxygen-containing gas is introduced to support the in-situ combustion reaction of the carbon-containing fuel within the droplet.

[0039] The oxidation remediation zone is equipped with a secondary gas inlet, which is located after the combustion phase formation zone and before the cooling zone, and is used to replenish oxygen-containing gas before the gas-solid mixture enters the cooling zone.

[0040] By adopting the above technical solution, the combustion phase-forming zone and the oxidation repair zone respectively undertake the functions of heating phase formation and atmosphere correction. The primary gas injection port supplies oxygen-containing gas to the combustion phase-forming zone, enabling the carbon-containing fuel to undergo in-situ oxidation reactions inside or on the surface of the droplets, releasing heat and promoting rapid phase formation of the cobalt and lithium sources. Since carbon monoxide or a locally reducing atmosphere may be generated during the combustion of carbon-containing fuel, if the gas-solid mixture directly enters the cooling zone under these conditions, the valence state of cobalt may easily shift. The secondary gas injection port is located after the combustion phase-forming zone and before the cooling zone, allowing oxygen-containing gas to be supplied to the gas-solid mixture before cooling, further oxidizing carbon monoxide to carbon dioxide and increasing the oxidizing properties of the environment surrounding the gas-solid mixture. Through the phased setup of primary and secondary gas injection, the heating process of carbon-containing fuel combustion and the oxidation regulation process before cooling can be controlled separately, thereby reducing the problems of insufficient oxygen supply or accumulation of locally reducing atmosphere under a single gas injection method.

[0041] Preferably, the atomizer is a pressure atomizing nozzle, a rotary atomizer, or a dual-fluid atomizing nozzle;

[0042] When using a pressure-type atomizing nozzle, the atomizing pump pressure is set to 2.0–2.5 MPa; when using a rotary atomizer, the rotation speed is set to 10,000–20,000 rpm.

[0043] By limiting specific mechanical energy input conditions, the relative sliding velocity between the carrier gas and the liquid film can be controlled, thereby controlling the initial Sotter mean diameter of the droplets. The size of the droplets directly determines the subsequent drying time and the geometry of the final product particles.

[0044] Preferably, an exhaust gas detection unit is provided at the combustion chamber outlet to detect the oxygen, carbon monoxide, and carbon dioxide content in the exhaust gas online, and adjust the oxygen-containing gas flow rate of the primary or secondary air inlet and the feed rate of the slurry pump according to the detection results to maintain the oxidizing reaction atmosphere in the combustion chamber.

[0045] By adopting the above technical solution, the exhaust gas detection unit can reflect the combustion state and redox environment of carbon-containing fuels in the combustion chamber. When the carbon monoxide content in the exhaust gas increases, it indicates that the carbon-containing fuel is not fully combusted or that there is insufficient oxygen supply in some areas. When the oxygen content in the exhaust gas decreases, it indicates a mismatch between the oxygen-containing gas supply and the slurry feed rate. Adjusting the oxygen-containing gas flow rate at the primary or secondary air inlet based on the exhaust gas detection results can improve the oxidizing properties of the combustion phase formation zone or the oxidation repair zone. Adjusting the feed rate of the slurry pump based on the exhaust gas detection results can control the amount of carbon-containing fuel and reactants entering the combustion chamber per unit time. This feedback adjustment creates a matching relationship between the oxygen supply and the feed rate, reducing the accumulation of local reducing atmosphere caused by feed fluctuations and improving the reaction stability during continuous spray combustion.

[0046] Preferably, the cooling zone exchanges heat with the dust-laden high-temperature airflow through a cooling jacket, and the cooling jacket is cooled by water cooling, air cooling, or a combination of water cooling and air cooling.

[0047] Preferably, the product collector includes a cyclone separator and a bag filter.

[0048] The collected solid powder needs to be crushed and demagnetized to obtain the lithium cobalt oxide cathode material.

[0049] The exhaust gas produced by the reaction is collected and then introduced into the exhaust gas treatment system for treatment before being discharged.

[0050] This invention provides a method for preparing low-cost lithium cobalt oxide cathode materials based on slurry spray combustion. It has the following beneficial effects:

[0051] 1. This invention prepares a combustion slurry by cobalt source, lithium source, carbon-containing fuel, polymeric dispersant, and water, and maintains the dispersion of the reactants and carbon-containing fuel in the slurry through cyclic shear mixing. After atomization, the combustion slurry forms droplets. These droplets first lose some water and shrink in a pre-evaporation concentration zone before entering the combustion phase-forming zone for in-situ combustion of the carbon-containing fuel. Thus, the heat released by the carbon-containing fuel can directly act on the cobalt and lithium sources inside the droplets, reducing external heat transfer paths, improving heat utilization efficiency, and enabling the lithium cobalt oxide phase-forming reaction to be completed in a shorter time, thereby reducing high-temperature holding time and manufacturing energy consumption.

[0052] 2. This invention sets up a combustion phase-forming zone and an oxidation repair zone within the combustion chamber, and introduces oxygen-containing gas in stages through a primary and a secondary gas injection port. The primary gas injection port supports in-situ combustion of carbon-containing fuel inside or on the surface of the droplet, while the secondary gas injection port replenishes oxygen-containing gas before the gas-solid mixture enters the cooling zone, thereby reducing the impact of the localized reducing atmosphere generated during the combustion of carbon-containing fuel on the cobalt valence state. Furthermore, the exhaust gas detection unit detects the oxygen, carbon monoxide, and carbon dioxide content, and adjusts the gas injection flow rate or slurry pump feed rate to maintain a stable oxidizing atmosphere during the combustion reaction, which is beneficial for improving the consistency of the lithium cobalt oxide phase-forming reaction.

[0053] 3. This invention introduces modified additives into the combustion slurry, allowing these additives to enter the droplet reaction system along with the cobalt source, lithium source, and carbon-containing fuel. During the droplet pre-evaporation and concentration, combustion phase formation, and cooling processes, the modified additives are transformed into corresponding metal oxides or non-metal oxides, enabling simultaneous bulk doping or surface coating during lithium cobalt oxide formation. Simultaneously, the gas-solid mixture after the reaction is forcibly cooled in a short time via a cooling jacket, reducing lithium volatilization, grain coarsening, and structural relaxation caused by high-temperature residence. This allows powder synthesis, atmosphere conditioning, modification treatment, and cooling and shaping to be completed in a continuous process. Attached Figure Description

[0054] Figure 1 This is a graph showing the XRD characteristic peak intensity ratio and XPS cobalt valence state distribution of the samples from this invention.

[0055] Figure 2 This is a distribution diagram of the physical compactness index of the embodiments and comparative samples of the present invention;

[0056] Figure 3 This is a distribution diagram of residual carbon content and Raman peak intensity ratio in the samples of this invention;

[0057] Figure 4 This is a distribution diagram of unit energy consumption and overall manufacturing cost under different process paths of the present invention;

[0058] Figure 5The following are electrochemical performance test graphs of the samples of the present invention, wherein (a) is a graph showing the distribution of the initial discharge capacity and rate performance of each sample, and (b) is a graph showing the distribution of the high voltage cycling performance of each sample.

[0059] Figure 6 Here is a scanning electron microscope image of the material obtained in this invention;

[0060] Figure 7 This is a schematic diagram of the atomizing combustion device of the present invention.

[0061] The components include: 1. Slurry storage tank; 2. Slurry pump; 3. Atomizer; 4. Ignition device; 5. Combustion chamber; 6. Primary air supply port; 7. Cooling jacket; 8. Product collector; 9. Exhaust gas treatment system; and 10. Secondary air supply port. Detailed Implementation

[0062] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0063] The main raw materials and reagents used in the following examples and comparative examples have the following sources and specifications. Reagents not specifically mentioned are all commercially available analytical grade or higher grade products.

[0064] Cobalt oxide, with the chemical formula CoO and CAS number 1307-96-6, is made from commercially available industrial or battery-grade powder with a cobalt mass fraction of not less than 75%.

[0065] Cobalt tetroxide, with the chemical formula Co3O4 and CAS number 1308-06-1, is made from commercially available battery-grade powder.

[0066] Lithium carbonate, with the chemical formula Li2CO3 and CAS number 554-13-2, uses commercially available battery-grade powder with a main content of not less than 99.5%.

[0067] Lithium hydroxide monohydrate, with the chemical formula LiOH·H2O and CAS number 1310-66-3, uses commercially available battery-grade powder.

[0068] Coke powder, whose main component is carbon, has the CAS number 7440-44-0. It is a solid carbon-containing fuel made by crushing and grinding commercially available industrial-grade high-carbon coking coal.

[0069] Biomass charcoal powder, whose main component is carbon, has a CAS number of 7440-44-0 and uses commercially available industrial-grade biomass pyrolysis carbonization pulverized fuel.

[0070] Sodium carboxymethyl cellulose, CAS number 9004-32-4, is a commercially available chemically pure grade product.

[0071] Sodium polyacrylate, CAS number 9003-04-7, is a commercially available chemically pure grade product.

[0072] Polyvinyl alcohol, CAS number 9002-89-5, is a commercially available chemically pure product with a degree of alcoholysis of 87% to 89%.

[0073] Sodium lignosulfonate, CAS number 8061-51-6, is a commercially available chemically pure grade product.

[0074] Nano-alumina, with the chemical formula Al2O3 and CAS number 1344-28-1, is made from commercially available powder with a purity of not less than 99.9% and an average particle size of 30 to 50 nanometers.

[0075] See attached document Figure 7 , Figure 7 This is a schematic diagram of the atomizing combustion device according to the present invention.

[0076] Example 1:

[0077] This embodiment provides a method for preparing low-cost lithium cobalt oxide cathode materials based on slurry spray combustion, including the following steps:

[0078] (1) 100 parts cobalt oxide, 45 parts lithium carbonate, 20 parts coke powder, 2 parts sodium polyacrylate, 0.5 parts sodium carboxymethyl cellulose, 1.3 parts magnesium nitrate hexahydrate, 2.6 parts tetraethyl orthosilicate and 115 parts water are placed in a ball mill and ground and mixed at room temperature for 2 hours to prepare a uniform combustion slurry. The solid content of the slurry is controlled to be 60% by adjusting the amount of water added, the apparent viscosity at room temperature is 2000 mPa·s, the median particle size D50 is 5.0 micrometers, and the prepared combustion slurry is stored in slurry storage tank 1. A circulation reflux pipeline is set between slurry storage tank 1 and atomizer 3. Before entering atomizer 3, the combustion slurry is continuously refluxed and homogenized at a circulation flow rate of 50 L / min so that the apparent viscosity at room temperature of the combustion slurry before entering atomizer 3 is maintained in the range of 1800 to 2200 mPa·s.

[0079] (2) The combustion slurry is pumped by the slurry pump 2 to the atomizer 3 located at the top of the combustion chamber 5. The atomizer 3 uses a pressure atomizing nozzle and is set with a pumping pressure of 2.0 MPa. The atomized droplets are atomized and enter the combustion chamber 5 with the air carrier gas at a flow rate of 15 L / min. The combustion chamber 5 is arranged in sequence along the droplet movement direction as a pre-evaporation concentration zone, a combustion phase formation zone, an oxidation repair zone, and a cooling zone. The atomized droplets first enter the pre-evaporation concentration zone at a temperature of 350°C and stay for 0.6 seconds, causing some of the water in the droplets to evaporate and shrink. Then, they enter the combustion phase formation zone at a temperature of 1000°C and are ignited by the ignition device. The combustion chamber 5 provides an initial heat source to ignite the fuel. A primary air inlet 6 is provided in the combustion phase formation zone of the combustion chamber 5, which introduces air at a flow rate of 20 L / min to support in-situ combustion of coke powder within the droplets. A secondary air inlet 10 is provided after the combustion phase formation zone, which introduces oxygen-enriched air at a flow rate of 8 L / min. The oxygen-enriched air has an oxygen volume fraction of 30% and is used to perform short-term oxidation treatment on the gas-solid mixture generated by the reaction. The residence time of the gas-solid mixture in the oxidation repair zone is 0.8 seconds, and the total residence time of the droplets in the combustion chamber 5 is controlled to be 3.0 seconds, of which the residence time in the combustion phase formation zone is 1.6 seconds.

[0080] An exhaust gas detection unit is installed at the outlet of combustion chamber 5 to detect the oxygen, carbon monoxide, and carbon dioxide content in the exhaust gas online. When the volume fraction of carbon monoxide in the exhaust gas is higher than 0.5% or the volume fraction of oxygen is lower than 3%, the oxygen-containing gas flow rate of the first-stage air inlet 6 and / or the second-stage air inlet 10 is increased; when the volume fraction of oxygen in the exhaust gas is higher than 12%, the oxygen-containing gas flow rate of the second-stage air inlet 10 is reduced to maintain an oxidizing reaction atmosphere in combustion chamber 5.

[0081] (3) The dust-laden high-temperature gas flow generated by the reaction then quickly enters the gas-solid cooling zone with cooling jacket 7 and rapidly cools down to below 150°C within 2 seconds. The cooled solid powder is collected by the product collector 8, which includes a cyclone separator and a bag filter. After being crushed and demagnetized, the lithium cobalt oxide cathode material is obtained. At the same time, the tail gas generated by the reaction is introduced into the tail gas treatment system 9 for treatment and then discharged.

[0082] Example 2:

[0083] This embodiment provides a method for preparing low-cost lithium cobalt oxide cathode materials based on slurry spray combustion, including the following steps:

[0084] (1) 150 parts of cobalt nitrate hexahydrate, 38 parts of lithium nitrate, 18 parts of sucrose, 1.5 parts of sodium polyacrylate, 0.3 parts of sodium carboxymethyl cellulose and 100 parts of water were placed in a sand mill and mixed under high shear at room temperature for 1.5 hours to prepare a homogeneous combustion slurry. The solid content of the slurry was controlled to be 67%, the apparent viscosity at room temperature was 1000 mPa·s, the median particle size D50 was 3.5 micrometers, and the prepared combustion slurry was stored in slurry storage tank 1. The slurry storage tank 1 was equipped with a low-speed stirring paddle and a circulation return pipeline. The speed of the low-speed stirring paddle was 80 rpm and the circulation return flow rate was 35 L / min, so that the sucrose, nitrate and dispersant were uniformly distributed before entering the atomizer 3. The apparent viscosity at room temperature of the combustion slurry before entering the atomizer 3 was controlled by the online viscosity detection unit to be maintained in the range of 900 to 1100 mPa·s.

[0085] (2) The slurry is pumped to the atomizer 3 by the slurry pump 2. The atomizer 3 uses a pressure atomizing nozzle and the atomizing pumping pressure is set to 2.5 MPa. The atomized droplets enter the combustion chamber 5 with the air carrier gas. The combustion chamber 5 is arranged in sequence along the droplet movement direction as a pre-evaporation concentration zone, a combustion phase formation zone, an oxidation repair zone, and a cooling zone. The atomized droplets first enter the pre-evaporation concentration zone at a temperature of 300°C and stay for 0.5 seconds to allow the droplets to complete partial dehydration. Then, they enter the combustion phase formation zone at a temperature of 850°C and are ignited by the ignition device. 4. An initial heat source is provided to ignite the fuel. Air is introduced at a flow rate of 18 L / min through the primary air inlet 6. Combined with the oxidizing gas produced by the thermal decomposition of nitrate, the sucrose undergoes in-situ combustion within the droplets. A secondary air inlet 10 is set at the rear end of the combustion phase formation zone to introduce oxygen-enriched air with an oxygen volume fraction of 28% at a flow rate of 6 L / min. The gas-solid mixture resides in the oxidation repair zone for 1.0 second. The total residence time of the droplets in the combustion chamber 5 is controlled to be 5.0 seconds, of which the residence time in the combustion phase formation zone is 3.5 seconds.

[0086] An exhaust gas detection unit is installed at the outlet of combustion chamber 5 to detect the oxygen, carbon monoxide and carbon dioxide content in the exhaust gas online. Based on the exhaust gas detection results, the flow rates of the first-stage air inlet 6 and the second-stage air inlet 10 are adjusted to maintain the oxygen volume fraction in the exhaust gas at 3% to 10% and the carbon monoxide volume fraction below 0.5%.

[0087] (3) The dust-laden high-temperature airflow generated by the reaction enters the forced air cooling quenching zone with cooling jacket 7 and cools down to below 200°C within 2 seconds. The cooled solid product is collected by product collector 8, and after sieving, the layered lithium cobalt oxide cathode material is obtained. The tail gas is introduced into the tail gas treatment system 9 for treatment and then discharged.

[0088] Example 3:

[0089] This embodiment provides a method for preparing low-cost lithium cobalt oxide cathode materials based on slurry spray combustion, including the following steps:

[0090] (1) 125 parts of cobalt acetate tetrahydrate, 22 parts of lithium hydroxide monohydrate, 14 parts of biomass char powder, 1 part of polyvinyl alcohol and 200 parts of water were placed in a ball mill and ground and mixed at room temperature for 3 hours to prepare a basic combustion slurry without doping or coating. The solid content of the slurry was controlled to be 45%, the apparent viscosity at room temperature was 500 mPa·s, the median particle size D50 was 8.0 micrometers, and the prepared combustion slurry was stored in slurry storage tank 1. A circulation reflux pipeline was set in slurry storage tank 1. The combustion slurry was refluxed and homogenized at a circulation flow rate of 30 L / min before entering atomizer 3. At the same time, the apparent viscosity at room temperature was controlled to be maintained in the range of 450 to 550 mPa·s by an online viscosity detection unit to avoid sedimentation and stratification of biomass char powder during storage and transportation.

[0091] (2) The combustion slurry is delivered to the atomizer 3 by the slurry pump 2. The atomizer 3 is a rotary atomizer with a rotation speed of 10,000 to 20,000 rpm. The atomized droplets enter the combustion chamber 5 with the air carrier gas. The combustion chamber 5 is arranged in sequence along the droplet movement direction as a pre-evaporation concentration zone, a combustion phase formation zone, an oxidation repair zone, and a cooling zone. The atomized droplets first enter the pre-evaporation concentration zone at a temperature of 380°C and stay for 0.4 seconds to remove some moisture from the droplets beforehand; then they enter the zone at a temperature of 1200°C. In the combustion phase formation zone, the biomass charcoal powder is ignited by the ignition device 4, and the primary air supply port 6 introduces air at a flow rate of 25 L / min to support the combustion heat release. After the combustion phase formation zone, a secondary air supply port 10 is set up to introduce oxygen-enriched air with an oxygen volume fraction of 35% at a flow rate of 10 L / min, so that the gas-solid mixture stays in the oxidation repair zone for 0.6 seconds before entering the cooling zone. The total residence time of the droplets in the combustion chamber 5 is controlled to be 2.0 seconds, of which the residence time in the combustion phase formation zone is 1.0 second.

[0092] An exhaust gas detection unit is installed at the outlet of combustion chamber 5. When the volume fraction of carbon monoxide in the exhaust gas is detected to be higher than 0.8%, the oxygen-enriched air flow rate of the secondary air injection port 10 is increased to 12 L / min. When the volume fraction of oxygen in the exhaust gas is lower than 3%, the air flow rate of the primary air injection port 6 is increased to 28 L / min to maintain the oxidizing reaction atmosphere in the combustion phase formation zone and the oxidation repair zone.

[0093] (3) The gas-solid mixture enters the water-cooled cooling zone with cooling jacket 7 and is rapidly cooled to 150°C. The solid powder is collected by the product collector 8 containing a bag filter. After demagnetization, the lithium cobalt oxide cathode material is obtained, and the tail gas is introduced into the tail gas treatment system 9.

[0094] Example 4:

[0095] This embodiment provides a method for preparing low-cost lithium cobalt oxide cathode materials based on slurry spray combustion, including the following steps:

[0096] (1) 100 parts cobalt oxide, 45 parts lithium carbonate, 10 parts coke powder, 3 parts sodium polyacrylate, 1 part sodium carboxymethyl cellulose and 65 parts water were placed in a kneading and grinding mill and mixed to prepare a high solids content fluid slurry. The solid content of the slurry was controlled to be 70% and the apparent viscosity at room temperature was 8000 mPa·s. The prepared combustion slurry was stored in slurry storage tank 1. A high torque stirring mechanism and a circulation reflux pipeline were installed in slurry storage tank 1. The speed of the high torque stirring mechanism was 40 rpm and the circulation reflux flow rate was 20 L / min. The viscosity of the slurry was monitored by an online viscosity detection unit. When the apparent viscosity at room temperature was higher than 8500 mPa·s, water was added to adjust it to the range of 7500 to 8500 mPa·s. When the apparent viscosity at room temperature was lower than 7500 mPa·s, the amount of water added was reduced and the reflux homogenization time was extended.

[0097] (2) High-viscosity slurry is delivered to atomizer 3 by slurry pump 2. Atomizer 3 uses a dual-fluid atomizing nozzle to atomize the slurry and send it into combustion chamber 5. Combustion chamber 5 is arranged in sequence along the droplet movement direction as a pre-evaporation concentration zone, combustion phase formation zone, oxidation repair zone and cooling zone. The atomized droplets first enter the pre-evaporation concentration zone at a temperature of 420°C and stay for 0.3 seconds to pre-shrink the high solid content droplets. Then they enter the combustion phase formation zone at a temperature of 1100°C and are ignited by ignition device 4. The first-stage air supply port 6 introduces oxygen-enriched air at a flow rate of 22L / min. The oxygen volume fraction in the oxygen-enriched air is 32%. After the combustion phase formation zone, a second-stage air supply port 10 is set up to introduce air at a flow rate of 8L / min. The gas-solid mixture stays in the oxidation repair zone for 0.5 seconds before entering the cooling zone. The total residence time of the droplets in combustion chamber 5 is controlled to be 1.3 seconds, of which the residence time in the combustion phase formation zone is 0.5 seconds.

[0098] An exhaust gas detection unit is installed at the outlet of combustion chamber 5, and the exhaust gas detection unit is linked with slurry pump 2 and primary air supply port 6. When the volume fraction of carbon monoxide in the exhaust gas is higher than 0.5%, the oxygen-enriched air flow rate of primary air supply port 6 is increased to 25L / min, or the feeding speed of slurry pump 2 is reduced by 5% to 10%.

[0099] (3) The product enters the water-cooled wall forced quenching cooling zone with cooling jacket 7 and is cooled to room temperature. The product collector 8 collects the densified high-pressure lithium cobalt oxide cathode material containing trace amounts of residual carbon, and the tail gas is discharged into the tail gas treatment system 9.

[0100] Example 5:

[0101] This embodiment provides a method for preparing low-cost lithium cobalt oxide cathode materials based on slurry spray combustion, including the following steps:

[0102] (1) Mix and grind 100 parts cobalt oxide, 90 parts lithium nitrate, 76 parts coke powder, 0.5 parts sodium lignosulfonate and 1060 parts water to prepare a low-viscosity suspension slurry. Control the solid content of the slurry to be 20% and the apparent viscosity at room temperature to be 200 mPa·s. Store the prepared combustion slurry in slurry storage tank 1. A circulation return pipeline is set in slurry storage tank 1. The combustion slurry is circulated back and homogenized at a circulation flow rate of 60 L / min. The suspension stability of coke powder and the viscosity of the slurry are monitored by an online turbidity detection unit and an online viscosity detection unit to keep the apparent viscosity of the slurry at room temperature in the range of 180 to 240 mPa·s before entering the atomizer 3.

[0103] (2) The slurry is pumped by the slurry pump 2 to the atomizer 3 with a pressure nozzle. After atomization, the slurry enters the combustion chamber 5. The combustion chamber 5 is set with a pre-evaporation concentration zone, a combustion phase formation zone, an oxidation repair zone and a cooling zone in sequence along the droplet movement direction. The atomized droplets first enter the pre-evaporation concentration zone at a temperature of 280°C and stay for 1.2 seconds to remove some water from the low solid content droplets. Then, they enter the combustion phase formation zone at a temperature of 950°C and are ignited by the ignition device 4. A large proportion of coke powder is combined with the air provided by the primary air supply port 6 to burn. The air flow rate of the primary air supply port 6 is 35L / min. After the combustion phase formation zone, a secondary air supply port 10 is set to introduce oxygen-enriched air with an oxygen volume fraction of 30% at a flow rate of 12L / min. The gas-solid mixture stays in the oxidation repair zone for 1.5 seconds. The total residence time of the droplets in the combustion chamber 5 is controlled to be 10.0 seconds, of which the residence time in the combustion phase formation zone is 7.3 seconds.

[0104] An exhaust gas detection unit is installed at the outlet of combustion chamber 5, and the feeding speed of primary air inlet 6, secondary air inlet 10 and slurry pump 2 is adjusted according to the oxygen, carbon monoxide and carbon dioxide content in the exhaust gas. Specifically, when the volume fraction of carbon monoxide in the exhaust gas is higher than 0.8%, the oxygen-enriched air flow rate of secondary air inlet 10 is increased to 15L / min, and when the volume fraction of oxygen in the exhaust gas is lower than 3%, the air flow rate of primary air inlet 6 is increased to 40L / min.

[0105] (3) After the gas-solid mixture is cooled by the cooling jacket 7, it is collected by the product collector 8 to obtain powder material, and the exhaust gas is discharged to the exhaust gas treatment system 9.

[0106] Example 6:

[0107] This embodiment provides a method for preparing low-cost lithium cobalt oxide cathode materials based on slurry spray combustion, including the following steps:

[0108] (1) Mix and grind 100 parts cobalt tetroxide, 48 parts lithium carbonate, 30 parts sucrose, 2 parts sodium lignosulfonate, 1 part polyvinyl alcohol, 2 parts titanium isopropoxide, 1 part nano alumina and 130 parts water for 2.5 hours to prepare a composite modified slurry. Control the solid content to be 55% and the apparent viscosity at room temperature to be 1200 mPa·s. Store the prepared combustion slurry in slurry storage tank 1. The slurry storage tank 1 is equipped with a circulation reflux pipeline and an online viscosity detection unit. Before entering the atomizer 3, the combustion slurry is refluxed and homogenized at a circulation flow rate of 45 L / min to keep the sucrose, cobalt tetroxide, lithium carbonate and modified additives in a uniform suspension state. The apparent viscosity of the slurry at room temperature is controlled to be maintained in the range of 1100 to 1300 mPa·s by the online viscosity detection unit.

[0109] (2) The slurry is fed into the atomizer 3 by the slurry pump 2 and atomized by the dual-fluid atomizing nozzle before entering the combustion chamber 5. The combustion chamber 5 is set with a pre-evaporation concentration zone, a combustion phase formation zone, an oxidation repair zone and a cooling zone in sequence along the droplet movement direction. The atomized droplets first enter the pre-evaporation concentration zone at a temperature of 360°C and stay for 0.5 seconds to allow the droplets to complete partial dehydration and shrinkage. Then, they enter the combustion phase formation zone at a temperature of 1000°C and are ignited by the ignition device 4. The first-stage air supply port 6 introduces air at a flow rate of 20L / min to allow the fuel sucrose to undergo in-situ combustion in the droplets. After the combustion phase formation zone, a second-stage air supply port 10 is set up to introduce oxygen-enriched air with an oxygen volume fraction of 30% at a flow rate of 9L / min. The gas-solid mixture stays in the oxidation repair zone for 0.8 seconds before entering the cooling zone. The total residence time of the droplets in the combustion chamber 5 is controlled to be 4.0 seconds, of which the residence time in the combustion phase formation zone is 2.7 seconds.

[0110] An exhaust gas detection unit is installed at the outlet of combustion chamber 5 to detect the oxygen, carbon monoxide, and carbon dioxide content in the exhaust gas online, and adjust the oxygen-enriched gas flow rates of the primary air inlet 6 and the secondary air inlet 10 according to the detection results; when the carbon monoxide volume fraction in the exhaust gas is higher than 0.5%, the oxygen-enriched air flow rate of the secondary air inlet 10 is increased to 12L / min, and when the oxygen volume fraction in the exhaust gas is higher than 12%, the oxygen-enriched air flow rate of the secondary air inlet 10 is reduced to 6L / min.

[0111] (3) Dust-laden high-temperature airflow enters the cooling jacket 7 for forced cooling and is collected by the product collector 8 to obtain lithium cobalt oxide cathode material with a titanium aluminum oxide film layer on the outer surface and a complete layered structure inside. The exhaust gas enters the exhaust gas treatment system 9.

[0112] Comparative Example 1:

[0113] Weigh 100 parts of battery-grade cobalt tetroxide and 48.5 parts of battery-grade lithium carbonate, add them to a ball mill and mix for 4 hours. Place them in an electric heating box furnace and calcine at 950°C for 12 hours. After natural cooling, crush and sieve to obtain the lithium cobalt oxide product.

[0114] Comparative Example 2:

[0115] Compared with Example 1, the difference is that no coke powder was added when preparing the combustion slurry, and the ignition device was turned off during the atomization reaction. Conventional spray pyrolysis was carried out only by relying on the external electric heater of the combustion chamber to provide a high-temperature thermal field of 1000°C. All other aspects are the same.

[0116] Comparative Example 3:

[0117] Compared with Example 1, the difference is that the gas supply port of the combustion chamber is closed during the reaction, and the external oxygen compensation is cut off, resulting in the formation of an extremely oxygen-deficient pure reducing atmosphere in the droplet micro-region due to the oxygen consumption of coke powder combustion. All other aspects are the same.

[0118] Comparative Example 4:

[0119] Compared with Example 1, the difference is that the amount of water added is greatly increased to about 3000 parts when preparing the combustion slurry, which greatly reduces the solid content of the slurry to about 5%, thereby destroying the capillary contraction force under high solid content. All other aspects are the same.

[0120] Comparative Example 5:

[0121] Compared with Example 1, the difference is that the gas-solid cooling zone with cooling jacket is removed, and the dust-laden high-temperature gas flow generated by the reaction directly enters the conventional large-volume heat preservation settling chamber, and is naturally and slowly cooled to room temperature with the furnace. The process of rapid quenching, freezing and shrinkage is eliminated, and everything else is the same.

[0122] Comparative Example 6:

[0123] Compared with Example 1, the difference is that tetraethyl orthosilicate, which serves as a surface coating element source, was not added when preparing the combustion slurry, thus disrupting the interfacial segregation and spontaneous formation mechanism of the coating layer. All other aspects are the same.

[0124] Test Example 1:

[0125] Powder samples from Examples 1 to 6 and Comparative Examples 1 to 3 were obtained and placed in a vacuum drying oven at 120°C for 12 hours to remove surface adsorbed water.

[0126] Weigh about 2 grams of dry powder, spread it evenly and compact it on a quartz glass sample stage, and use an X-ray diffractometer to scan the crystal structure. The test uses a copper target radiation source, with the tube voltage and tube current set to 40 kV and 40 mA, respectively. The scanning range is controlled between 10° and 80°, and the step size is set to 0.02°.

[0127] Extract the absolute peak intensities of the (003) and (104) characteristic crystal planes in the diffraction pattern and calculate their ratio. Combine this with full-spectrum fine fitting to obtain the ratio of lattice parameters c to a.

[0128] A small amount of the same batch of samples was uniformly fixed on conductive tape and sent into the ultra-high vacuum analysis chamber of the X-ray photoelectron spectrometer. The surface elements and chemical states were scanned using monochromatic aluminum Kα rays as the excitation source.

[0129] The high-resolution spectrum of the cobalt core energy level was subjected to Shirley background subtraction and peak fitting. The relative atomic percentages of trivalent cobalt and divalent cobalt on the sample surface were calculated by integrating the area of ​​each characteristic peak of each valence state.

[0130] The data is shown in Table 1:

[0131] Table 1: Quantitative analysis data of crystal structure parameters and surface cobalt valence state of each sample

[0132] Sample number I(003) / I(104) peak intensity ratio c / a lattice parameter ratio <![CDATA[Co 3+ Relative content (%) <![CDATA[Co 2+ Relative content (%) Example 1 1.28 4.996 99.4 0.6 Example 2 1.31 4.998 99.7 0.3 Example 3 1.25 4.992 98.9 1.1 Example 4 1.34 4.999 99.8 0.2 Example 5 1.22 4.989 98.6 1.4 Example 6 1.29 4.995 99.5 0.5 Comparative Example 1 1.14 4.982 96.2 3.8 Comparative Example 2 1.18 4.985 97.5 2.5 Comparative Example 3 0.95 4.974 82.3 17.7

[0133] in conclusion:

[0134] According to Table 1 and Figure 1 The data shows that the sample in the example group successfully constructed the target layered rock salt structure within an extremely short reaction window. In X-ray diffraction analysis, the I(003) / I(104) peak intensity ratio is often used to evaluate the degree of cation mixing in layered transition metal oxides. When this ratio exceeds 1.2, it usually indicates that the material has low mixing and excellent layered arrangement. The ratio of this ratio in Examples 1 to 6 is distributed in the range of 1.22 to 1.34, and the test results are clearly better than those of Comparative Example 1 (peak intensity ratio of 1.14), which underwent conventional high-temperature sintering for 12 hours. This physical phenomenon of long-range ordered crystallization completed in seconds breaks through the kinetic limitations of conventional solid-phase reactions that rely on long-term heat conduction and solid-state ion diffusion. Combined with the preparation process of this invention, the low-melting-point lithium salt in the system melts instantaneously in an ultra-high temperature environment to form a micro-region liquid phase, fundamentally changing the mass transfer path of the phase transition interface. The molten liquid phase provides an extremely high mass transport rate when wetting and enveloping the surrounding solid precursor, allowing the lattice development process to directly overcome the energy barrier generated by solid-solid mechanical contact, exhibiting highly efficient epitaxial growth characteristics. Combined with the continuous arrangement of the pre-evaporation concentration zone, combustion phase formation zone, and oxidation repair zone in each embodiment, the atomized droplets undergo partial dehydration and shrinkage before entering the main combustion reaction, which is beneficial for the further enrichment of reaction components in the droplet micro-region. Subsequently, the carbon-containing fuel releases heat in situ in the combustion phase formation zone, enabling the cobalt source and lithium source to complete a rapid reaction within a short residence time.

[0135] Quantitative surface elemental data from X-ray photoelectron spectroscopy further elucidated the oxidation reaction logic in the aforementioned rapid phase formation process. In the example group, the relative content of trivalent cobalt reached over 98.6%, and no large-scale residue of low-valence impurity phases was found. In the high-temperature pyrolysis system accompanied by violent combustion of carbon-containing fuels, the strongly reducing microenvironment easily hinders the conversion of transition metal ions to higher valence states. The test results of Comparative Example 3 confirmed this chemical limitation; after artificially cutting off external gas supply and removing endogenous oxidizing salts, the proportion of divalent cobalt in the product surged to 17.7%, and the final phase of the material deviated significantly from the design specifications of pure-phase layered lithium cobalt oxide. The examples, through the synergistic effect of the release of active oxygen from the thermal decomposition of nitrates within the system and the forced air supply from the external system, established a localized strongly oxidizing environment within the flying droplets, sufficient to counteract the surrounding reducing thermal field. The oxygen partial pressure within the microenvironment rapidly reached saturation after fuel combustion, thermodynamically forcibly advancing the de-electron process that would otherwise be difficult to complete completely in a very short time, ensuring the chemical stability of the trivalent state of the main elements in the lithium cobalt oxide lattice. The phase parameters and valence state distribution characteristics obtained from the tests directly confirmed the feasibility of the micro-region in-situ oxygen supply and molten salt liquid phase epitaxial growth mechanism at the macroscopic testing level.

[0136] Test Example 2:

[0137] The positive electrode material powders prepared in Examples 1 to 6 and Comparative Examples 1, 4 and 5 were obtained. Approximately 50 grams of each powder were placed in a 110°C forced-air drying oven and baked at a constant temperature for 6 hours to remove free moisture from the powder surface.

[0138] Weigh 20 grams of dry powder and slowly pour it into a 25 ml graduated cylinder through a glass funnel. Fix the graduated cylinder to the vibration component of the powder tap density tester. Set the vibration frequency to 250 times / minute and the total number of vibrations to 3000. After the program ends, read the final volume of the powder in the graduated cylinder and calculate the corresponding tap density based on the sample mass.

[0139] Weigh 5.0 g of dry powder and place it in a high-carbon steel cylindrical mold with an inner diameter of 13 mm. Gently tap to compact and level the surface. Operate a hydraulic servo powder compaction density meter, applying pressure to 300 MPa at a constant rate and holding the pressure for 10 seconds. Use the high-precision displacement sensor equipped with the device to read the thickness of the compacted block under pressure, calculate the volume of the compacted block based on the bottom area of ​​the mold, and thus obtain the compaction density of the sample.

[0140] The experimental data are shown in Table 2:

[0141] Table 2: Test data of physical density index of powder for each sample

[0142] Sample number <![CDATA[Tap density (g / cm 3 )]]> <![CDATA[Compaction density @ 300 MPa (g / cm 3 )]]> Example 1 2.62 4.03 Example 2 2.68 4.12 Example 3 2.54 3.96 Example 4 2.76 4.15 Example 5 2.48 3.91 Example 6 2.65 4.08 Comparative Example 1 2.38 3.84 Comparative Example 4 1.15 2.65 Comparative Example 5 1.82 3.15

[0143] in conclusion:

[0144] According to Table 2 and Figure 2 Data shows that conventional spray pyrolysis processes, due to the intense vaporization and expansion of the solvent within the droplets at high temperatures, easily form porous or hollow powder structures. This physical phenomenon is clearly reflected in the test results of Comparative Example 4. When the slurry solid content in the process was adjusted to 5%, the extremely high solvent content dominated the drying kinetics of the droplets. The outward vapor pressure generated by the boiling of water hindered the internal structural shrinkage of the particles, causing the tap density of the product to drop to 1.15 g / cm³. 3 Even under an external test pressure of 300 MPa, its compaction density is only 2.65 g / cm³. 3 Powders with a large number of pores will severely limit the volumetric energy density of batteries in the actual roll coating process of battery electrodes.

[0145] The example group exhibited drastically different powder development patterns through adjustments to the slurry formulation. Within the higher solid content range of 20% to 70%, the proportion of free water in the system was significantly compressed. When the droplets entered the high-temperature reaction field, the rapid evaporation of trace solvents was insufficient to generate outward expansion force; instead, it triggered strong capillary tension through the retreat of the liquid interface. This physical tension instantly pulled the dispersed solid precursor towards the center of the droplet, promoting initial geometric compaction of the particles. For example, Example 4, with a solid content of 70%, achieved a compaction density of 4.15 g / cm³. 3 This confirms that reducing the solvent volume ratio can effectively trigger the capillary contraction effect of precursor particles and lock them into a contracted state. Combined with the pre-evaporation concentration zone set in the embodiment, the atomized droplets have already had some moisture removed before entering the combustion phase-forming zone, further increasing the concentration of solid components within the droplets. This process, together with the high-solids slurry itself, makes it easier for the droplets to contract and aggregate when entering the high-temperature combustion phase-forming stage, rather than forming hollow particles dominated by solvent vaporization and expansion.

[0146] The final density of the particles depends not only on the initial physical drag but also on the thermodynamic conditions during the cooling stage. Comparative Example 5 removed the forced cooling jacket, allowing the high-temperature gas-solid mixture to undergo slow, natural cooling in the latter part of the reactor; its compacted density subsequently dropped to 3.15 g / cm³. 3Within the microenvironment of micron-sized particles, the pores left by the combustion of carbon-containing fuels and the liquid-phase filling of molten low-melting-point salts are in dynamic competition. A slow cooling rate leads to continuous thermal expansion of residual gases, while the slow release of lattice thermal stress may cause structural relaxation or secondary microcracks in the already contracted particles. The forced quenching zone in the example process can rapidly reduce the system temperature to a safe threshold within seconds. This temperature cutoff mechanism directly freezes the dense configuration of the particles after capillary shrinkage and liquid-phase sintering, inhibiting secondary expansion of internal pores. The synergy between physical freezing and micro-area liquid-phase sintering results in a powder density slightly exceeding that of traditional pure solid-phase synthesis products that have undergone long-term heat treatment (Comparative Example 1), providing fundamental parameter guarantees for the practical engineering applications of the material.

[0147] Test Example 3:

[0148] The cathode material powders prepared in Examples 1 to 6, as well as Comparative Examples 1 and 2, were collected and placed in a vacuum drying oven at 100°C for 8 hours to desorb the impurity gases and free moisture adhering to the surface of the powder.

[0149] Accurately weigh 0.5 g of dry powder, add pure iron and tungsten-tin flux, transfer to a special ceramic crucible, and then push it into the induction furnace chamber of the high-frequency infrared carbon-sulfur analyzer. Perform high-frequency induction heating combustion on the sample in an oxygen-rich carrier gas environment. Use the built-in infrared detector of the device to capture the characteristic absorption peak of carbon dioxide in the escaping gas in real time, and calculate and output the total carbon mass fraction in the sample based on the calibration curve of the standard material.

[0150] A trace amount of powder was evenly spread onto a clean glass slide, and gently pressed with a flat glass plate to make the surface dense and smooth. The slide was placed on the test stage of a micro Raman spectrometer, using a solid-state laser with a wavelength of 532 nm as the excitation source. To prevent localized thermal damage to the sample caused by the high-energy laser, the laser power was strictly limited to 5 milliwatts, the single exposure time was set to 10 seconds, and three signals were superimposed. A 1000 cm⁻¹ sample was collected. -1 Up to 2000cm -1 Raman scattering spectra within the range, after smoothing and subtracting the extracted spectral baseline, were analyzed for locations at approximately 1350 cm⁻¹. -1 The D peak at approximately 1580 cm -1 Lorentz line fitting was performed on the G peak at that location. The integral areas of both lines were recorded and the corresponding values ​​were calculated. Peak intensity ratio. Samples that do not show a significant scattered signal within a specified wavelength band are recorded as having no signal.

[0151] The experimental data are shown in Table 3:

[0152] Table 3: Residual carbon content and carbon structure Raman spectral analysis data for each sample

[0153] Sample number Residual carbon content (wt%) Peak intensity ratio Example 1 1.14 0.92 Example 2 0.87 1.05 Example 3 1.32 1.18 Example 4 0.65 0.88 Example 5 1.86 0.81 Example 6 1.45 0.98 Comparative Example 1 0.03 No signal Comparative Example 2 0.05 No signal

[0154] in conclusion:

[0155] According to Table 3 and Figure 3 According to the data, after introducing carbon-based fuels into the spray reaction system, the actual carbon residue of the product is at a low level. Excessive amorphous carbon in the battery cathode material usually reduces the compaction density of the electrode and increases the diffusion resistance of lithium ions at the interface. In Examples 1 to 6, carbon-based energetic fuels such as coke powder, sucrose, or biomass char powder were specifically added during the mixing stage. After high-temperature spray reaction, the residual carbon content of the product was controlled between 0.65 wt% and 1.86 wt%. This indicates that the carbon source inside the droplets underwent a sufficient oxidation reaction when exposed to the high-temperature thermal field and oxygen, and most of the carbon left the system in gaseous form, avoiding the formation of a thick physical barrier layer inside the particles. The carbon detection values ​​of the pure solid-phase synthesis in Comparative Example 1 and the spray method product without coke powder in Comparative Example 2 were only 0.03% and 0.05%, respectively, which belong to the baseline background of the test equipment system or trace environmental contamination. Since this trace carbon does not have complete structural features, it failed to excite an effective signal in Raman spectroscopy. The residual carbon content in the example group can be maintained within a low range, which corresponds to the staged oxygen supply method of setting a primary air supply port and a secondary air supply port in the example: the primary air supply port supports in-situ combustion of carbon-containing fuel in the droplets, and the secondary air supply port replenishes an oxidizing atmosphere before cooling, thereby reducing the risk of excessive carbon residue caused by incomplete combustion.

[0156] For trace structural carbon retained in the bulk phase and grain boundaries, Raman spectral parameters further reflect the transformation of its microscopic order. In the spectroscopic analysis of carbon materials, 1350 cm⁻¹... -1 The nearby D peak is attributed to defects and disorder in the carbon lattice, 1580 cm⁻¹ -1 The nearby G peak corresponds to sp 2 The ratio of peak intensities of the in-plane stretching vibrations of hybrid carbon atoms. Commonly used to evaluate the degree of localized graphitization in carbon materials. Example group. The values ​​range from 0.81 to 1.18. Compared to the amorphous carbon produced by conventional low-temperature pyrolysis (the ratio is usually greater than 1.5), the residual carbon produced by this process has a relatively high sp2 value. 2The hybridization ratio exhibits localized graphitization characteristics. Conventional modification processes require prolonged high-temperature treatment above 1500℃ for graphitization of carbon precursors. In this preparation method, the transient thermal field provided by micro-region fuel combustion provides the thermodynamic conditions for the rearrangement of carbon atoms; furthermore, the cobalt ions enriched within the system exhibit a significant catalytic effect on the transformation of the amorphous carbon framework into a graphite-like microstructure at high temperatures. The subsequent rapid cooling process directly retains this conductive microcrystalline carbon network within the intergranular spaces of the primary grains. This embedded conductive phase, formed alongside the in-situ reaction, provides a physical channel for electron transport during high-voltage charge-discharge processes.

[0157] Test Example 4:

[0158] Economic calculations were performed on single full-load production batches of Example 1, Comparative Example 1, and Comparative Example 2. The purchase price and actual input of cobalt source for each batch were recorded. Example 1 and Comparative Example 2 used industrial-grade cobalt suboxide, while Comparative Example 1 used deeply refined battery-grade cobalt tetroxide.

[0159] Track the entire production cycle. A high-precision power meter is connected in series at the input of the electric heating equipment to record the total power consumption of the material from heating, high-temperature reaction to cooling and exiting the furnace. For Example 1, the coke powder mixed into the slurry is additionally weighed on a dry basis, and the fuel cost is calculated based on the benchmark price of bulk coal transactions. Simultaneously, the operation log of the on-site centralized control system is extracted to confirm the actual residence time of the core reaction section.

[0160] Establish a static cost accounting model for a single ton of product. Summarize the cobalt source procurement cost, industrial electricity cost, and coke powder fuel cost, and combine this with the final output weight of qualified powder to calculate the unit energy consumption cost per kilogram of powder and the comprehensive manufacturing cost per ton of product.

[0161] The experimental data are shown in Table 4:

[0162] Table 4: Energy consumption and economic accounting data for the entire production cycle of the examples and comparative examples.

[0163] project Example 1 Comparative Example 1 Comparative Example 2 Comparison and explanation Cobalt source type Industrial grade cobalt oxide Battery-grade cobalt tetroxide Industrial grade cobalt oxide The average market price of industrial-grade cobalt sources is approximately 42% of that of battery-grade precursors. Energy source Coke powder combustion is the primary source of heat. pure electric heating pure electric heating Coke powder provides in-situ heat, reducing reliance on external electrical energy. Energy consumption per unit product (RMB / kg) 0.87 3.85 3.14 Endogenous heat release significantly reduces direct thermal costs. Number of processes 3 steps 7 steps 4 steps The embodiment combines the precursor refining and high-temperature sintering processes. Core reaction time 3.2 seconds 12.5 hours 35 seconds The reaction kinetics changed from heat conduction to transient in-situ exothermic reaction. Comprehensive manufacturing cost estimation 74,000 yuan / ton 142,000 yuan / ton 116,000 yuan / ton Raw material substitution and energy consumption reduction work together to reduce overall costs.

[0164] in conclusion:

[0165] According to Table 4 and Figure 4The data shows that the manufacturing cost structure of cathode materials has changed significantly after the introduction of the micro-area self-heating process. Conventional lithium cobalt oxide production relies on battery-grade cobalt tetroxide, and the precursors used in Comparative Example 1 require multiple refining processes, including acid dissolution, impurity removal, extraction, and controlled crystallization. These lengthy chemical steps increase environmental remediation costs, which are ultimately reflected as a premium in material preparation. Example 1 simplifies this path by directly using crude, unrefined cobalt suboxide as the input raw material. Although Comparative Example 2 also attempted to use this inexpensive cobalt source for spray pyrolysis, the lack of an internal heat source meant that its thermal process still heavily relied on external electrical energy, resulting in a comprehensive cost of 116,000 yuan / ton, failing to fully realize the economic advantages of raw material substitution.

[0166] The underlying reason for the cost difference lies in the difference in thermodynamic transport methods. In the traditional solid-state synthesis framework, Comparative Example 1, limited by the long-range solid-state diffusion rate between reactant components, requires 12.5 hours of high-temperature holding in a box furnace. During this period, a large amount of external electrical energy is consumed in the insulation of the equipment itself and the dissipation of heat from the environment, resulting in high energy consumption per unit product (3.85 yuan / kg). Example 1 changes the heat supply logic; the uniformly dispersed coke powder inside the suspended droplets is ignited upon entering the reaction field, and the heat released from combustion directly constructs a transient thermal field within the micron-sized particles. This in-situ exothermic mechanism bypasses the thermal conduction resistance at the gas-to-solid interface, shortening the development time of the core phase to 3.2 seconds. Thanks to this efficient heat utilization method, the direct energy cost of Example 1 is reduced to 0.87 yuan / kg. Engineering test data shows that the use of downgraded raw materials and the reduction in energy consumption during the manufacturing process have a significant synergistic effect.

[0167] Test Example 5:

[0168] The positive electrode material powders prepared in Examples 1 to 6 and Comparative Examples 1, 2, and 6 were dry-mixed with conductive carbon black and polyvinylidene fluoride (PVDF) in a mass ratio of 8:1:1. An appropriate amount of N-methylpyrrolidone (NMP) solvent was added dropwise to prepare a slurry with certain rheological properties, which was then coated onto the surface of an aluminum foil current collector. The electrode was placed in a vacuum drying oven at 120°C and baked for 12 hours to evaporate the solvent. Subsequently, it was compacted by a roller press and punched into positive electrode discs with a diameter of 14 mm.

[0169] Inside a high-purity argon glove box, a lithium metal sheet was used as the counter electrode, and a polypropylene microporous membrane was used as the separator. A 1 mol / L lithium hexafluorophosphate (LiPF6) solution was selected as the electrolyte, and the solvent was composed of ethylene carbonate (EC), diethyl carbonate (DEC), and methyl ethyl carbonate (EMC) in a 1:1:1 volume ratio to assemble a CR2032 coin cell.

[0170] After assembly, the battery was allowed to stand for 12 hours to fully wet the electrodes before being connected to the battery testing system for testing within the 2.8V to 4.5V voltage range. A constant current of 0.1C was used to perform three charge-discharge cycles for activation, and the initial discharge specific capacity was recorded. Subsequently, the rate was adjusted to 0.5C for 200 charge-discharge cycles, and the capacity retention rate was recorded. A separate rate test group was also established to evaluate the battery's capacity retention level under a 5C high-current discharge condition.

[0171] The experimental data are shown in Table 5:

[0172] Table 5: Electrochemical performance test data of each sample

[0173] Sample number Initial discharge capacity (mAh / g) Capacity retention (%) after 200 cycles at 0.5C 5C rate capacity retention (%) Example 1 184.6 93.50 85.80 Example 2 183.2 93.10 85.20 Example 3 177.8 90.80 83.50 Example 4 186.1 94.20 87.30 Example 5 179.8 91.60 82.80 Example 6 185.3 93.80 86.40 Comparative Example 1 176.2 89.30 78.60 Comparative Example 2 181.5 88.70 82.10 Comparative Example 6 182.4 84.20 80.50

[0174] in conclusion:

[0175] According to Table 5, Figure 5 and Figure 6 The content describes how raising the charging cutoff potential to 4.5V places higher demands on the lattice structure and interface stability of the cathode material. Under high-voltage delithiation, the bulk lithium cobalt oxide crystal undergoes an irreversible phase transition from the O3 phase to the H1-3 phase, and the exposed surface is more prone to catalyzing the oxidative decomposition of the electrolyte. Comparative Example 1, prepared by long-term solid-state sintering, showed a capacity retention rate of only 89.30% after 200 cycles at 0.5C, and its initial capacity was limited to only 176.2 mAh / g due to the non-uniformity of solid-state diffusion. Comparative Example 2 used a spray pyrolysis process, and the liquid-phase mixing of the precursor increased its initial capacity to 181.5 mAh / g. However, due to the lack of internal structural modification, its long-cycle retention rate (88.70%) was basically at the same level as that of the traditional solid-state method.

[0176] Test results show that Examples 1 and 2, which incorporate a micro-regional deflagration mechanism, outperform the traditional solid-state method in all electrochemical indicators and are slightly superior to conventional spray pyrolysis products. Example 1 achieved an initial discharge capacity of 184.6 mAh / g, a retention rate of 93.50% after 200 cycles at 0.5C, and a retention rate of 85.80% at a high discharge rate of 5C. This performance improvement is directly related to the microscopic physical network formed within the material. Short-duration in-situ deflagration retains trace amounts of graphitized carbon between primary particles and grain boundaries, and this embedded conductive network reduces ohmic polarization during high-frequency charge and discharge processes. Meanwhile, the failure phenomenon of Comparative Example 6 (where the removal of the coating source resulted in a cycle retention rate drop to 84.20%) indirectly confirms that the example system utilizes instantaneous thermal field-driven elemental segregation to spontaneously construct a physical isolation layer on the particle surface, mitigating dissolution and corrosion problems under high pressure. Based on the economic analysis of previous test cases, the process of the embodiment, while achieving the above-mentioned performance optimization, reduces the overall cost by approximately 30% to 40% compared to Comparative Example 2 by replacing the inexpensive cobalt source and the self-heating mechanism, and reduces the energy consumption per unit product by approximately 50%. This engineering design, which simultaneously completes bulk crystallization, conductive network construction, and interface passivation at the microscale, provides a technical path for the manufacture of cathode materials that balances high performance and significant economic benefits.

[0177] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing low-cost lithium cobalt oxide cathode materials based on slurry spray combustion, characterized in that, Includes the following steps: Raw materials including cobalt source, lithium source, carbon-containing fuel, polymeric dispersant and water are mixed and ground to prepare a combustion slurry, and the prepared combustion slurry is stored in a slurry storage tank. The carbon-containing fuel is selected from one or more of coke powder, biomass charcoal powder and sucrose, and the solid content of the combustion slurry is 20% to 70%, the apparent viscosity at room temperature is 200 to 8000 mPa·s, and the median particle size D50 is 3.5 to 8.0 micrometers. The combustion slurry is delivered to the atomizer by a slurry pump, atomized into droplets, and enters the combustion chamber with the carrier gas. The combustion chamber includes at least a pre-evaporation and concentration zone, a combustion phase formation zone, and a cooling zone along the movement direction of the droplets. The droplets first evaporate some water and shrink in the pre-evaporation and concentration zone, and then enter the combustion phase formation zone. The carbon-containing fuel is ignited by an initial heat source provided by an ignition device, and the combustion reaction takes place under the condition that oxygen-containing gas is introduced through the primary and secondary air inlets, so that the temperature of the high-temperature reaction environment in the combustion chamber is 850-1200°C, and the residence time of the atomized droplets in the combustion chamber is controlled to be 0.5-10 seconds. The gas-solid mixture generated by the reaction enters the cooling zone with a cooling jacket for forced cooling. Within 2 seconds, the dust-laden high-temperature airflow is rapidly cooled to below 200°C. The cooled solid powder is collected by the product collector to obtain the lithium cobalt oxide cathode material, while the exhaust gas is introduced into the exhaust gas treatment system. The combustion slurry is prepared from raw materials comprising the following parts by weight: 100-150 parts of cobalt source; Lithium source: 22-90 parts; Carbon-containing fuels: 10–76 parts; 0.5 to 4 parts of polymeric dispersant; Water 65–1060 parts; The raw materials of the combustion slurry also include modified additives; The amount of the modified additive is 1 to 3.9 parts; The modifying additive is selected from one or more of magnesium nitrate hexahydrate, tetraethyl orthosilicate, titanium isopropoxide, and nano-alumina; The combustion chamber also includes an oxidation repair zone located between the combustion phase formation zone and the cooling zone; The combustion phase-forming zone is provided with a primary gas supply port, through which oxygen-containing gas is introduced to support the in-situ combustion reaction of the carbon-containing fuel within the droplet. The oxidation remediation zone is equipped with a secondary gas inlet, which is located after the combustion phase formation zone and before the cooling zone, and is used to replenish oxygen-containing gas before the gas-solid mixture enters the cooling zone.

2. The method for preparing low-cost lithium cobalt oxide cathode material based on slurry spray combustion according to claim 1, characterized in that, The cobalt source is selected from one or more of cobalt(II) oxide, cobalt(III) oxide, cobalt(II) nitrate, and cobalt(II) acetate, and the lithium source is selected from one or more of lithium carbonate, lithium nitrate, and lithium hydroxide.

3. The method for preparing low-cost lithium cobalt oxide cathode material based on slurry spray combustion according to claim 1, characterized in that, The polymeric dispersant is selected from one or more of sodium polyacrylate, sodium carboxymethyl cellulose, polyvinyl alcohol, and sodium lignosulfonate.

4. The method for preparing low-cost lithium cobalt oxide cathode material based on slurry spray combustion according to claim 1, characterized in that, The atomizer is a pressure atomizing nozzle, a rotary atomizer, or a dual-fluid atomizing nozzle. When using a pressure-type atomizing nozzle, the atomizing pump pressure is set to 2.0–2.5 MPa; when using a rotary atomizer, the rotation speed is set to 10,000–20,000 rpm.

5. The method for preparing low-cost lithium cobalt oxide cathode material based on slurry spray combustion according to claim 1, characterized in that, An exhaust gas detection unit is installed at the outlet of the combustion chamber to detect the oxygen, carbon monoxide, and carbon dioxide content in the exhaust gas online. Based on the detection results, the flow rate of oxygen-containing gas at the primary or secondary air inlet and the feeding speed of the slurry pump are adjusted to maintain the oxidizing reaction atmosphere in the combustion chamber.

6. The method for preparing low-cost lithium cobalt oxide cathode material based on slurry spray combustion according to claim 1, characterized in that, The cooling zone exchanges heat with the dust-laden, high-temperature airflow through a cooling jacket, which is cooled by water cooling, air cooling, or a combination of water cooling and air cooling.

7. The method for preparing low-cost lithium cobalt oxide cathode material based on slurry spray combustion according to claim 1, characterized in that, The product collector includes a cyclone separator and a bag filter. The collected solid powder needs to be crushed and demagnetized to obtain the lithium cobalt oxide cathode material. The exhaust gas produced by the reaction is collected and then introduced into the exhaust gas treatment system for treatment before being discharged.

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