Lithium-rich material preparation method, lithium-rich material and positive pole piece

Abstract

The invention relates to a lithium-rich material preparation method, a lithium-rich material and a positive pole piece, and belongs to the technical field of power battery preparation. The preparation method comprises the following steps: carrying out acid leaching treatment on the ferro-nickel alloy, and then filtering to obtain an acid solution containing nickel ions and ferrous ions; alkali is added into the acid solution for precipitation, the pH value of the solution is adjusted to 3-10, nickel hydroxide and ferrous hydroxide precipitates are obtained and filtered, and precipitates are obtained. And drying the precipitate, and then carrying out low-temperature calcination so as to decompose the precipitate to obtain a nickel oxide and ferrous oxide mixture. And carrying out primary high-temperature calcination on the mixture, lithium hydrogen phosphate powder and a carbon source together, then adding lithium oxide, and carrying out secondary high-temperature calcination to obtain the lithium iron phosphate and lithium nickelate compound. According to the preparation method of the lithium-rich material, the processing process from preparation of the lithium supplementing agent and the lithium iron phosphate to mixing to form the slurry can be simplified, and the production cost is reduced while the production and processing efficiency is improved.

Description

Technical Field

[0001] The present application relates to the technical field of power battery preparation, and in particular to a method for preparing a lithium-rich material, a lithium-rich material, and a positive electrode sheet. Background Art

[0002] With the development of the new energy industry, the requirements for the energy density and life of lithium-ion batteries are gradually increasing. Lithium iron phosphate batteries generate a solid electrolyte interface (SEI) film on the negative electrode surface during the first charge and discharge, which consumes active lithium and reduces the cycle life. Pre-lithiation is one of the means to solve the above problem, among which positive electrode lithium supplementation is more widely used.

[0003] In the existing technology, commonly used positive electrode lithium supplements include lithium ferrite (Li5FeO4), lithium nickelate (Li2NiO2), lithium cobaltate (Li6CoO4), lithium zirconate (Li8ZrO6), etc. When used, the lithium supplement is mixed and stirred with lithium iron phosphate slurry as part of the battery's positive electrode active material.

[0004] However, when the above process method is used, the lithium supplement and lithium iron phosphate need to be prepared separately, and after preparation, they need to be mixed and stirred together to form a slurry. The overall preparation process is cumbersome, which not only affects the production and processing efficiency, but also leads to an increase in the overall processing cost. Summary of the Invention

[0005] The purpose of this application is to provide a method for preparing a lithium-rich material, a lithium-rich material and a positive electrode plate, which can simplify the processing process of preparing a lithium supplement and lithium iron phosphate until they are mixed to form a slurry, thereby improving production and processing efficiency while reducing production costs.

[0006] In order to achieve the above objectives, in a first aspect of the present application, the present application provides a method for preparing a lithium-rich material, the preparation method comprising the following steps:

[0007] Acid leaching treatment: the nickel-iron alloy is subjected to acid leaching treatment, and then filtered to obtain an acidic solution containing nickel ions and ferrous ions.

[0008] Add alkali to precipitate, add alkali to the acidic solution for precipitation, and adjust the pH value of the solution to 3-10 to obtain nickel hydroxide and ferrous hydroxide precipitates, and filter to obtain the precipitate.

[0009] The precipitate is dried and then calcined at a low temperature to decompose the precipitate to obtain a mixture of nickel oxide and ferrous oxide.

[0010] High-temperature calcination: the mixture is initially calcined at high temperature together with lithium hydrogen phosphate powder and a carbon source, and then lithium oxide is added and calcined at high temperature for a second time to obtain a lithium iron phosphate and lithium nickelate composite.

[0011] Based on the above-mentioned embodiments of the present application, when preparing lithium-rich materials, nickel-iron alloy is used as raw material. First, nickel and iron are present in the form of nickel ions and ferrous ions, respectively, in an acidic solution by acid leaching. In this process, some insoluble matter will be generated. After filtering out the insoluble matter, an acidic solution containing nickel ions and ferrous ions is obtained. Subsequently, alkali is added to the acidic solution to introduce hydroxide, such as adding sodium hydroxide, so that a double decomposition reaction occurs to generate nickel hydroxide and ferrous hydroxide precipitates. The precipitate is then filtered out, and some water-soluble impurities can be removed in this process. The filtered precipitate is dried and calcined at low temperature to generate a mixture of nickel oxide and ferrous oxide. Finally, after two high-temperature calcinations and the process of adding lithium oxide midway, a composite of lithium iron phosphate and lithium nickelate is finally obtained. Among them, lithium iron phosphate is the main component of the battery positive electrode slurry, and lithium nickelate is mixed with lithium iron phosphate as a lithium supplement. In summary, the processing method described above enables in-situ synthesis of a lithium-rich material comprising lithium iron phosphate and lithium nickelate, combining a two-part preparation process into a single one, thus simplifying the processing. Furthermore, the mixing process of lithium iron phosphate and lithium nickelate is eliminated, further simplifying the process and reducing costs, ultimately lowering the manufacturing cost of lithium-ion batteries.

[0012] In some embodiments, before the acid leaching treatment, the preparation method further includes: high-temperature insulation, subjecting the nickel-iron alloy to high-temperature insulation treatment.

[0013] Based on the above-mentioned embodiments of the present application, before the acid leaching treatment, the phase structure of the nickel-iron alloy can be optimized by high-temperature insulation, so that the nickel ions and ferrous ions can better enter the acidic solution during the acid leaching treatment, thereby improving the reaction efficiency during the subsequent acid leaching treatment, and ultimately improving the finished product output rate.

[0014] In some embodiments, in the high-temperature insulation step, the insulation temperature is 700° C.-1000° C., and the insulation time is 0.5 h-2 h.

[0015] Based on the above-mentioned embodiments of the present application, by controlling the insulation temperature and insulation time, it is possible to ensure that the subsequent acid leaching efficiency is improved through appropriate heating, and to a certain extent, it is possible to avoid deformation of the nickel-iron alloy or other adverse reactions caused by excessive temperature that affect the subsequent processing process.

[0016] In some embodiments, the nickel content of the nickel-iron alloy is 5%-20% by weight, the iron content is 77.5%-94.5% by weight, and / or the particle size of the nickel-iron alloy is in the range of 0.3 μm-50 μm.

[0017] Based on the above-mentioned embodiments of the present application, by limiting the weight ratio of nickel and iron in the nickel-iron alloy respectively, on the one hand, the proportion of other impurities in the nickel-iron alloy can be reduced, reducing the impact on the quality of the final product. On the other hand, the ratio of lithium iron phosphate and lithium nickelate in the final lithium-rich material product can also be limited to a certain extent, that is, the ratio of lithium iron phosphate to lithium supplement agent in the lithium-rich material is guaranteed, and the energy density of the battery as a whole is guaranteed. Further, the particle size of the nickel-iron alloy is limited so that the particle size of the nickel-iron alloy can be limited to a suitable range, usually with nickel-iron alloy powder as raw material. When the particle size is too large, it is not conducive to the full contact of the nickel-iron alloy with the acid solution, thereby affecting the efficiency of the acid leaching treatment and affecting the yield of the final product. And when the particle size is too small, the processing and preparation process of the nickel-iron alloy will be required to be higher, which not only affects the overall production and processing efficiency, but also causes the processing cost to rise.

[0018] In some embodiments, in the acid leaching step, the treatment temperature is 25° C.-100° C., and the treatment time is 0.5 h-3 h.

[0019] Based on the above-mentioned embodiments of the present application, during the acid leaching treatment, the treatment temperature is set to a temperature range higher than room temperature. By increasing the treatment temperature, the acid leaching efficiency is accelerated, and the solubility is increased, increasing the amount of dissolved nickel ions and ferrous ions, thereby improving the product yield. The specific treatment time can be adjusted according to the reaction rate and the amount of raw materials to ensure that the nickel-iron alloy can fully react with the acid solution.

[0020] In some embodiments, before the low-temperature calcination step, the method for preparing a lithium-rich material further comprises washing the precipitate to a neutral state.

[0021] Based on the above embodiments of the present application, by washing the precipitate, the acidic solution or some alkaline substances adsorbed on the surface of the precipitate can be removed, thereby avoiding the influence of the above substances on the subsequent reaction process and improving the quality of the final product.

[0022] In some embodiments, in the low-temperature calcination step, the calcination temperature increases gradually within the range of 230° C. to 500° C., and the calcination time is 4 h to 8 h.

[0023] Based on the above-mentioned embodiments of the present application, when calcined at low temperature, nickel hydroxide will first lose some of its crystal water, causing itself to form intermediate products such as basic carbonates. Subsequently, as the temperature continues to rise, the basic carbonates and other intermediate products will further decompose into nickel oxide and water. When calcining ferrous hydroxide, the main dehydration reaction occurs, generating ferrous oxide and water. By controlling the temperature to rise in a gradient, it is easier to control the reaction process and improve the yield of the product.

[0024] In some embodiments, in the high-temperature calcination step, the calcination temperature of the initial high-temperature calcination is 500°C-600°C, and the calcination time is 4h-8h; and / or, the calcination temperature of the secondary high-temperature calcination is 600°C-750°C, and the calcination time is 12h-24h; and / or, the carbon source includes at least one of glucose, sucrose, carbon black, phenolic resin, and carbon graphite.

[0025] Based on the above-described embodiments of the present application, during the high-temperature calcination process, during the initial high-temperature calcination, the mixture of nickel oxide, ferrous oxide, lithium hydrogen phosphate, and a carbon source preferentially produces lithium iron phosphate. Subsequently, by increasing the calcination temperature and performing a secondary high-temperature calcination, the reaction conditions are further adjusted to produce lithium nickelate. The specific carbon source can be selected based on actual application requirements.

[0026] According to a second aspect of the present application, a lithium-rich material is provided. The lithium-rich material is prepared by the above-mentioned lithium-rich material preparation method.

[0027] Based on the above-mentioned embodiments of the present application, the lithium-rich material provided by the present application is prepared by the above-mentioned method for preparing lithium-rich materials. Through the above-mentioned preparation method, a composite material comprising lithium iron phosphate and lithium nickelate can be prepared at the same time. Among them, lithium iron phosphate can be used as the main component of the positive electrode of the battery, and lithium nickelate can be used as a lithium supplement for the positive electrode of the battery. When used, the two compounds formed can be used directly, eliminating the mixing step. Thereby, it is possible to simplify the preparation process of the two and eliminate the mixing process, so that the process is further simplified, the cost is further reduced, and ultimately the manufacturing cost of the lithium supplement battery is reduced.

[0028] According to a third aspect of the present application, a positive electrode plate is provided, which includes the above-mentioned lithium-rich material.

[0029] Based on the above-mentioned embodiments of the present application, the positive electrode plate provided by the present application includes the above-mentioned lithium-rich material. The final product of the preparation process of the above-mentioned lithium-rich material is a mixed state of lithium iron phosphate and lithium nickelate. During use, the lithium iron phosphate serves as the main component of the active material in the battery positive electrode plate, while the lithium nickelate serves as a lithium supplement, which can replenish lithium ions consumed during battery use and improve the battery's cycle life.

[0030] Other features and advantages of the present application will be described in detail in the subsequent detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The accompanying drawings are used to provide a further understanding of the present application and constitute a part of the specification. Together with the following detailed description, they are used to explain the present application but do not constitute a limitation of the present application. In the accompanying drawings:

[0032] Figure 1It is a flow chart of the method for preparing lithium-rich materials provided in the embodiments of the present application.

[0033] Figure 2 3 is a flow chart of a method for preparing a lithium-rich material including step S0100 provided in an embodiment of the present application.

[0034] Figure 3 3 is a flow chart of a method for preparing a lithium-rich material including step S0300 provided in an embodiment of the present application. DETAILED DESCRIPTION

[0035] In order to make the purpose, technical solutions and advantages of this application more clearly understood, the present application is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain this application and are not intended to limit this application.

[0036] To make the objectives, technical solutions, and advantages of the embodiments of the present application more clear, the technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Generally, the components of the embodiments of the present application described and shown in the drawings herein can be arranged and designed in various different configurations.

[0037] Therefore, the following detailed description of the embodiments of the present application provided in the accompanying drawings is not intended to limit the scope of the present application for protection, but merely represents selected embodiments of the present application. All other embodiments obtained by persons of ordinary skill in the art based on the embodiments in the present application without making any creative efforts shall fall within the scope of protection of the present application.

[0038] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, it does not need to be further defined or explained in subsequent drawings.

[0039] In the description of this application, it should be noted that, unless otherwise stated, the terms "inner" and "outer" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, or the orientations or positional relationships in which the product of this application is typically placed when in use. These terms are intended solely to facilitate the description of this application and simplify the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limitations on this application. Furthermore, the terms "first" and "second" and the like are used solely to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0040] It should also be noted that, in the description of this application, unless otherwise expressly specified or limited, the terms "disposed" and "connected" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to direct connections, indirect connections through an intermediate medium, or internal connections between two components. Those skilled in the art will understand the specific meanings of the above terms in this application based on specific circumstances.

[0041] With the development of the new energy industry, the energy density and lifespan of lithium-ion batteries are being increasingly demanded. During the initial charge and discharge of lithium iron phosphate batteries, a solid electrolyte interface (SEI) film forms on the negative electrode surface, which consumes active lithium and reduces cycle life. Pre-lithiation is one of the methods to address this problem. Specifically, it involves pre-storing some lithium ions in the battery's electrode. When the solid electrolyte interface consumes lithium ions, the pre-stored lithium ions are released to replenish the battery.

[0042] In the existing technology, commonly used positive electrode lithium supplements include lithium ferrite (Li5FeO4), lithium nickelate (Li2NiO2), lithium cobaltate (Li6CoO4), lithium zirconate (Li8ZrO6), etc. When used, the lithium supplement is mixed and stirred with lithium iron phosphate slurry as part of the battery's positive electrode active material.

[0043] However, when using the above process, the lithium supplement and the lithium iron phosphate, the primary material for the battery's positive electrode, must be prepared using separate processes. This not only requires the establishment of separate production lines and production areas, but also increases costs in raw material procurement and other processes. Furthermore, after the lithium supplement and lithium iron phosphate are prepared separately, they must be mixed before use, making the overall production process cumbersome, affecting processing efficiency, lengthening the overall processing cycle, and increasing overall processing costs.

[0044] In order to solve the above problems in the prior art, according to the first aspect of the present application, the present application provides a method for preparing a lithium-rich material, referring to Figure 1 As shown, the preparation method comprises the following steps:

[0045] S100: acid leaching treatment, subjecting the nickel-iron alloy to acid leaching treatment, and then filtering treatment to obtain an acidic solution containing nickel ions and ferrous ions.

[0046] In this step, to ensure the content of nickel ions and ferrous ions in the resulting acidic solution, it is necessary to limit the content of each component in the nickel-iron alloy. In specific use, the weight ratio of nickel in the nickel-iron alloy can be limited to 5%-20%, and the weight ratio of iron can be limited to 77.5%-94.5%.

[0047] Based on the above-mentioned embodiments of the present application, by limiting the weight ratio of nickel and iron in the nickel-iron alloy respectively, on the one hand, the proportion of other impurities in the nickel-iron alloy can be reduced, thereby reducing the impact on the quality of the final product. On the other hand, the ratio of lithium iron phosphate and lithium nickelate in the final lithium-rich material product can also be limited to a certain extent, that is, the ratio of lithium iron phosphate to lithium supplement in the lithium-rich material is ensured, thereby ensuring the overall energy density of the battery. In addition, the nickel-iron alloy generally also includes other elements, such as sulfur and silicon.

[0048] Alternatively, in some other embodiments of the present application, the ratio of each element in the nickel-iron alloy can also be appropriately adjusted. For example, in some embodiments, a nickel-iron alloy with a nickel content of 5%-30% can be selected. By increasing the nickel content, the proportion of lithium nickelate in the final product can be adjusted. At the same time, after the ratio of each element is adjusted, the reaction process can also be appropriately adjusted within a suitable range, such as adjusting the reaction temperature and reaction time. The specific settings can be made according to actual conditions, and this application does not impose any specific restrictions on this.

[0049] In this step, the nickel-iron alloy can be in a bulk or powder form. In order to accelerate the reaction rate during the acid leaching treatment, in the practical application of this application, the particle size of the nickel-iron alloy can be limited to between 0.3 μm and 50 μm, that is, the nickel-iron alloy material can be selected in powder or granular form.

[0050] By limiting the particle size of Rhometal, the particle size of Rhometal can be limited in a suitable range, avoid the various problems caused by excessive or too small particle diameter. Specifically, when the particle size is too large, it is unfavorable for the sufficient contact of Rhometal with acid solution, thereby affecting the efficiency of acid leaching treatment, affecting the yield rate of final product. And when the particle size is too small, the processing preparation process of Rhometal can be required to be higher, not only affecting overall production and processing efficiency, but also processing cost can be increased, therefore usually using Rhometal powder as raw material in actual use.

[0051] Specifically, during the production and processing process, nickel-iron alloy powder with a particle size between 0.3μm and 50μm can be obtained by ball milling or other methods. The specific particle size can be set to multiple specific values ​​including 0.3μm, 5μm, 10μm, 20μm, 35μm and 50μm. In actual use, it can be specifically selected according to factors such as processing method and reaction requirements. This application does not impose any specific restrictions on this.

[0052] In terms of the choice of acid solution, in actual use, a variety of inorganic strong acid solutions can be selected, including sulfuric acid, hydrochloric acid, and nitric acid. Compared with organic acids, the above-mentioned inorganic acid solutions are generally more acidic, and therefore have better effects during acid leaching. In the specific reaction, taking sulfuric acid leaching as an example, the metal elements such as nickel and iron in the nickel-iron alloy will react with sulfuric acid to form corresponding sulfates. For example, nickel reacts with sulfuric acid to form nickel sulfate, and iron reacts with sulfuric acid to form ferrous sulfate. At this time, the nickel and iron elements are present in the sulfuric acid solution in the form of nickel ions and ferrous ions, respectively, for subsequent treatment.

[0053] During acid leaching of the nickel-iron alloy, other elements in the alloy also react with the acid solution to form insoluble matter. For example, some silicon in the alloy reacts with the acid solution to form silicon dioxide. The insoluble matter is then filtered out to produce an acidic solution containing nickel and ferrous ions.

[0054] In summary, when preparing lithium-rich materials, step S100: nickel-iron alloy is used as raw material in the acid leaching treatment. First, nickel and iron are made to exist in the acidic solution in the form of nickel ions and ferrous ions respectively by acid leaching. In this process, some insoluble matter is also generated. The insoluble matter is filtered out by filtration to obtain an acidic solution containing nickel ions and ferrous ions.

[0055] S200: adding alkali for precipitation, adding alkali to the acidic solution obtained in step S100 for precipitation, and adjusting the pH value of the solution to 3-10 to obtain nickel hydroxide and ferrous hydroxide precipitates, which are then filtered to obtain the precipitate.

[0056] In this step, the specific type of alkali added can be any one of sodium hydroxide, potassium hydroxide or ammonia. Taking the addition of sodium hydroxide as an example, a double decomposition reaction occurs in the solution to generate corresponding precipitates, specifically including nickel hydroxide precipitate and ferrous hydroxide precipitate.

[0057] S300: low-temperature calcination, drying the precipitate, and then performing low-temperature calcination to decompose the precipitate to obtain a mixture of nickel oxide and ferrous oxide.

[0058] In some embodiments of the present application, in the low-temperature calcination step, the calcination temperature increases gradually within the range of 230° C. to 500° C., and the calcination time is 4 h to 8 h.

[0059] Based on the above-mentioned embodiment of the present application, when low-temperature calcination is carried out, nickel hydroxide will first lose part of its crystal water to form intermediate products such as basic carbonate, and then when the temperature continues to rise, it will further decompose into nickel oxide and water. When ferrous hydroxide is calcined, a dehydration reaction mainly occurs to generate ferrous oxide and water. By controlling the temperature to rise in a gradient, it is easy to control the reaction process to increase the yield of the product. The specific calcination time can be adjusted according to the adaptability of the reaction process, and can be specifically set to multiple specific times including 4h, 6h and 8h, and the present application does not make specific restrictions on this.

[0060] Specifically, the phrase "calcination temperature gradually increases within the range of 230°C to 500°C" in this application means that during low-temperature calcination, the starting temperature is 230°C, and the temperature is gradually increased during calcination until the temperature reaches 500°C. For example, starting at 230°C, heating is continued until the temperature reaches 300°C and is maintained for a certain time, then heating is continued until the temperature reaches 400°C and is maintained for a certain time, and finally heating is continued until the temperature reaches 500°C and is maintained for a certain time.

[0061] S400: high-temperature calcination, the mixture is initially calcined together with lithium hydrogen phosphate powder and a carbon source at high temperature, and then lithium oxide is added and calcined at high temperature for a second time to obtain a lithium iron phosphate and lithium nickelate composite.

[0062] In some embodiments of the present application, in the high-temperature calcination step, the calcination temperature of the initial high-temperature calcination can be set to 500° C.-600° C., and the calcination time can be set to 4 h-8 h.

[0063] Based on the aforementioned embodiments of this application, during the high-temperature calcination process, the conditions for producing lithium nickelate are more stringent than those for producing lithium iron phosphate. Therefore, during the initial high-temperature calcination, the primary product is lithium iron phosphate. The primary reaction is: the iron in ferrous oxide reacts with the phosphorus and lithium in lithium hydrogen phosphate to produce lithium iron phosphate. The specific calcination temperature and time can be adjusted adaptively based on the reaction process and are not specifically limited in this application.

[0064] In some embodiments of the present application, in the high-temperature calcination step, the calcination temperature of the secondary high-temperature calcination can be set to 600° C.-750° C., and the calcination time can be set to 12 h-24 h.

[0065] Based on the above-mentioned embodiments of this application, during the secondary high-temperature calcination process, the reaction conditions are adjusted by increasing the calcination temperature and extending the calcination time to ensure that the reaction is in a high-temperature, oxygen-rich environment. This converts the nickel element from divalent nickel ions to trivalent nickel ions, causing nickel oxide and lithium oxide to react to form lithium nickelate. At the same time, some lithium iron phosphate is still produced during this process.

[0066] In some embodiments of the present application, in the high-temperature calcination step, the carbon source may include at least one of glucose, sucrose, carbon black, phenolic resin, and carbon graphite.

[0067] Based on the above embodiments of the present application, during the above specific reaction process, the presence of a carbon source can provide a reducing atmosphere, reducing the iron element to a low-valent state, which is conducive to the formation of lithium iron phosphate. At the same time, a carbon coating layer can be formed on the surface of the generated product to improve the conductivity and performance stability of the material. In specific use, any suitable carbon source type can be selected based on factors such as material cost. In addition, in some other embodiments, a polymer carbon source such as polyvinyl pyrrolidone (PVP) or polyvinyl alcohol (PVA) can also be selected. Under the condition that the above-mentioned use requirements are met, this application does not impose specific restrictions on this.

[0068] In summary, through the above-mentioned processing method of the present application, a composite material comprising lithium iron phosphate and lithium nickelate can be prepared simultaneously, wherein lithium iron phosphate is used as the main component of the battery positive electrode slurry, and lithium nickelate is mixed with lithium iron phosphate as a lithium supplement. The preparation process that should have been divided into two parts is combined into one part, which simplifies the processing of lithium iron phosphate and lithium nickelate. At the same time, the generated lithium iron phosphate and lithium nickelate are in a mixed state. Therefore, the mixing process of lithium iron phosphate and lithium nickelate is also omitted, which further simplifies the process and further reduces the cost, thereby ultimately reducing the manufacturing cost of lithium-supplemented batteries.

[0069] Furthermore, in the present application, lithium iron phosphate and lithium nickelate are prepared in situ using nickel-iron alloy as raw material. As the application of pyrometallurgical technology on nickel-iron ore in the existing technology becomes more and more mature, the output of nickel-iron ore is gradually increasing, and the economic efficiency of the above-mentioned process in industrial application is also gradually increasing.

[0070] In addition, the lithium-rich material preparation method disclosed in this application is not limited to the above steps. In application, additions, adjustments, and further refinements of some steps may be made based on the above disclosure. The following will be described in conjunction with some specific implementation processes.

[0071] refer to Figure 2 As shown in , in some embodiments of the present application, before the acid leaching treatment in S100, the preparation method may further include:

[0072] S0100: High temperature insulation, high temperature insulation treatment of nickel-iron alloy.

[0073] Based on the above-mentioned embodiments of the present application, before the acid leaching treatment, the phase structure of the nickel-iron alloy can be optimized by high-temperature insulation, so that the nickel ions and ferrous ions can better enter the acidic solution during the acid leaching treatment, thereby improving the reaction efficiency during the subsequent acid leaching treatment, and ultimately increasing the yield of lithium iron phosphate and lithium nickelate complexes.

[0074] Specifically, by subjecting the nickel-iron alloy to high-temperature insulation before acid leaching, the oxide layer on the surface of the nickel-iron alloy can be removed, making it easier to remove the oxide layer during the acid leaching process. Simultaneously, the internal phase structure of the nickel-iron alloy can be changed, causing changes such as grain growth and grain boundary migration within the nickel-iron alloy. This makes the microstructure inside the alloy looser, making it more susceptible to corrosion during the acid leaching process, thereby improving the depth and effectiveness of the acid leaching treatment.

[0075] On the other hand, high-temperature treatment of the nickel-iron alloy can also enhance the subsequent treatment effect. Specifically, high-temperature heating can make some impurity elements in the nickel-iron alloy more easily dissolved or separated during the acid leaching process, thereby improving the purity of the acidic solution obtained by filtration.

[0076] Furthermore, in some embodiments of the present application, in the above-mentioned S0100 high-temperature insulation step, the insulation temperature can be set to 700° C.-1000° C., and the insulation time can be set to 0.5 h-2 h.

[0077] Based on the above-mentioned embodiments of the present application, by controlling the holding temperature and holding time, it is possible to ensure that the subsequent acid leaching efficiency is improved by appropriate heating, and to a certain extent, it is possible to avoid deformation of the nickel-iron alloy caused by excessive temperature or other adverse reactions that affect the subsequent processing process. In specific use, the holding temperature can be set to multiple specific temperatures such as 700°C, 800°C, 900°C and 1000°C, and the holding time can also be specifically set to multiple specific times such as 0.5h, 1h, 1.5h and 2h. In actual use, it can be set according to factors such as the amount of nickel-iron alloy raw materials, and this application does not impose specific restrictions on this.

[0078] In some embodiments of the present application, in the acid leaching step, the treatment temperature is 25° C.-100° C., and the treatment time is 0.5 h-3 h.

[0079] Based on the above-mentioned embodiments of the present application, during the acid leaching treatment, the treatment temperature is set to a temperature range higher than room temperature. By increasing the treatment temperature, the acid leaching treatment efficiency is accelerated. Generally speaking, for every 10°C increase in temperature, the reaction rate can be increased by 2 to 4 times, thereby shortening the reaction time and improving production efficiency. At the same time, it can also increase solubility, increase the dissolution amount of nickel ions and ferrous ions, allow more metal elements to enter the acid solution, increase the extraction rate of acid leaching, and thus increase the final yield. The specific treatment time can be adjusted according to the reaction rate and the amount of raw materials so that the nickel-iron alloy can fully react with the acid solution.

[0080] refer to Figure 3 As shown in , in some embodiments of the present application, before the low-temperature calcination step S300, the method for preparing the lithium-rich material may further include:

[0081] S0300: Wash the precipitate to neutrality.

[0082] Based on the above-mentioned embodiments of the present application, the nickel-iron alloy is subjected to acid leaching to obtain an acidic solution containing nickel ions and ferrous ions, and then alkali is added to the acidic solution to finally obtain nickel hydroxide and ferrous hydroxide precipitates. The surface of the precipitate may be adsorbed with the acidic solution. At the same time, the surface of the precipitate or the cracks of the precipitate may also contain alkaline substances remaining in the above steps. By washing the precipitate, the acidic solution or part of the alkaline substances adsorbed on the surface of the precipitate can be removed, thereby avoiding the influence of the above substances on the subsequent reaction process, thereby improving the quality of the final product.

[0083] In addition, in some other embodiments of the present application, during the high-temperature calcination step, different gases can be injected into the reaction vessel to change the calcination atmosphere. For example, nitrogen and argon can be injected to form an inert atmosphere, thereby reducing or even isolating oxygen from entering the reaction system, thereby reducing oxygen interference and the formation of by-products, so that the prepared lithium iron phosphate product has a higher purity and improves battery performance. Alternatively, hydrogen and argon can be injected to form a weak reducing atmosphere. The specific setting can be based on the actual reaction process and is not specifically limited by this application.

[0084] On the basis of the above technical solution, according to the second aspect of the present application, the present application further provides a lithium-rich material, which is prepared by the above lithium-rich material preparation method.

[0085] Based on the above-mentioned embodiments of the present application, the lithium-rich material provided in the present application is prepared by the above-mentioned method for preparing lithium-rich materials. Through the above-mentioned preparation method, a composite material including lithium iron phosphate and lithium nickelate can be prepared at the same time. Among them, lithium iron phosphate can be used as the main component of the positive electrode of the battery, and lithium nickelate can be used as a lithium supplement for the positive electrode of the battery. When used, the two can be used directly without mixing. Thereby, it is possible to simplify the preparation process of the two and eliminate the mixing process, so that the process is further simplified, the cost is further reduced, and ultimately the manufacturing cost of the lithium supplement battery is reduced.

[0086] On the basis of the above technical solution, according to the third aspect of the present application, the present application provides a positive electrode plate, which includes the above lithium-rich material.

[0087] Based on the above-mentioned embodiments of this application, the positive electrode provided herein includes the above-mentioned lithium-rich material. The final products of the preparation process of the above-mentioned lithium-rich material are lithium iron phosphate and lithium nickelate. During use, the lithium iron phosphate serves as the main component of the active material in the battery positive electrode, while the lithium nickelate serves as a lithium supplement, which can replenish lithium ions consumed during battery use and improve the battery's cycle life.

[0088] The performance of the lithium iron phosphate and lithium nickelate composite prepared by the lithium-rich material preparation method of the present application will be further described in detail below through four specific examples and one comparative example.

[0089] Example 1

[0090] The nickel-iron alloy is treated by the lithium-rich material preparation method provided in this application to obtain a mixture of nickel oxide and ferrous oxide, specifically:

[0091] (1) The nickel-iron alloy is mechanically ground in a ball mill to obtain a uniform nickel-iron alloy powder, wherein the particle size of the nickel-iron alloy powder is set to 10 μm, the weight ratio of nickel in the nickel-iron alloy powder is 5%, and the weight ratio of iron in the nickel-iron alloy powder is 85%.

[0092] (2) The nickel-iron alloy powder is kept at a high temperature of 900°C for 2 hours.

[0093] (3) The nickel-iron alloy powder after high-temperature insulation is immersed in a sulfuric acid solution for acid leaching treatment at a treatment temperature of 50° C. for a treatment time of 2 h, and then filtered to obtain an acidic solution containing nickel ions and ferrous ions.

[0094] (4) Sodium hydroxide is added to the acidic solution to adjust the pH to 8, thereby reacting to obtain nickel hydroxide and ferrous hydroxide precipitates, which are filtered out and washed to neutrality.

[0095] (5) The precipitate is dried, and then the precipitate is calcined at a low temperature by gradually increasing the temperature from 230°C to 500°C for 8 hours, so that the precipitate is decomposed to obtain a mixture of nickel oxide and ferrous oxide.

[0096] (6) The mixture is subjected to high-temperature calcination. Lithium hydrogen phosphate powder and glucose as a carbon source are added to the mixture. The initial high-temperature calcination temperature is 650°C and the calcination time is 6 hours. Subsequently, lithium oxide is added to the mixture and a second high-temperature calcination is performed. The second high-temperature calcination temperature is 650°C and the calcination time is 12 hours, ultimately obtaining a composite of lithium iron phosphate and lithium nickelate.

[0097] Example 2

[0098] The nickel-iron alloy is treated by the lithium-rich material preparation method provided in the present application to obtain a mixture of nickel oxide and ferrous oxide. The processing steps of Example 2 are basically the same as those of Example 1, except that the calcination temperature of the secondary high-temperature calcination in Example 2 is 750°C and the calcination time is 20 hours.

[0099] Example 3

[0100] The nickel-iron alloy is treated using the lithium-rich material preparation method provided in the present application to obtain a mixture of nickel oxide and ferrous oxide. The processing steps of Example 3 are basically the same as those of Example 1, except that the weight ratio of nickel in the nickel-iron alloy powder in Example 3 is 15%, and the weight ratio of iron is 75%.

[0101] Example 4

[0102] The nickel-iron alloy is treated by the lithium-rich material preparation method provided in the present application to obtain a mixture of nickel oxide and ferrous oxide. The processing steps of Example 4 are basically the same as those of Example 1, except that the weight ratio of nickel in the nickel-iron alloy powder in Example 4 is 15%, the weight ratio of iron is 75%, and the calcination temperature of the secondary high-temperature calcination is 750°C, and the calcination time is 20 hours.

[0103] Test Examples

[0104] The composite of lithium iron phosphate and lithium nickelate prepared in Examples 1-4 was used to prepare a slurry, which was then applied to a battery positive electrode material to obtain a battery positive electrode sheet. The battery was then produced using the battery positive electrode sheet, and the capacity and cycle life of the battery were tested.

[0105] A comparative example is also set up. The difference between the comparative example and the above-mentioned test examples 1-4 is that in the comparative example, pure lithium iron phosphate is used to prepare a slurry, and then a battery positive electrode sheet and a battery are obtained to test the capacity and cycle life of the battery.

[0106] Table 1 shows the main parameters in the process of preparing the mixture of nickel oxide and ferrous oxide in Examples 1-4, as well as the gram capacity and cycle life of batteries prepared using the positive electrode materials in Examples 1-4 and the comparative example.

[0107] Table 1

[0108]

[0109]

[0110] It should be noted that the "0.1C gram capacity mAh / g 4.0V-2.5V" in Table 1 above refers to the gram capacity of the lithium iron phosphate and lithium nickelate composite or pure lithium iron phosphate at a discharge rate of 0.1 over a voltage range of 4.0V to 2.5V. For example, the value 163.2 corresponding to Example 1 means that the gram capacity of the lithium iron phosphate and lithium nickelate composite prepared in Example 1 is 163.2 mAh / g at a discharge rate of 0.1 over a voltage range of 4.0V to 2.5V.

[0111] In Table 1 above, "25°C Cycle Life @ 80% SOH" refers to the number of cycles a battery undergoes until its state of health (SOH) reaches 80% at an ambient temperature of 25°C, i.e., the number of cycles it takes for the battery's usable capacity to decay to 80% of its initial capacity. For example, the value 2500 corresponding to Example 1 means that the battery's capacity will decay to 80% of its initial capacity after 2500 cycles of charge and discharge at an ambient temperature of 25°C.

[0112] As can be seen from Table 1, the battery made of pure lithium iron phosphate in the comparative example has a gram capacity of 160 mAh / g at a discharge rate of 0.1 times and a voltage range of 4.0V to 2.5V. In contrast, the lithium iron phosphate and lithium nickelate composites prepared by the above-mentioned lithium-rich material preparation method in Examples 1-4 were applied to the battery positive electrode sheet and the gram capacities measured under the same conditions were 163.2 mAh / g, 166 mAh / g, 167.5 mAh / g and 176 mAh / g, respectively. Compared with the comparative example, the gram capacity of the battery positive electrode material has been significantly improved.

[0113] Meanwhile, in terms of battery cycle life, under the operating condition of 25°C, the number of charge and discharge cycles after which the capacity of the battery prepared in the comparative example decayed to 80% of the initial capacity was 2000. In comparison, under the same operating conditions, the number of charge and discharge cycles after which the capacity of the battery in Examples 1-4 decayed to 80% of the initial capacity was 2500, 2800, 3000, and 3800, respectively, indicating that the battery cycle life was significantly extended.

[0114] In summary, the lithium-rich material preparation method disclosed in this application can simplify the preparation process of lithium iron phosphate and lithium nickelate as a lithium supplement, simplify the production process, and reduce production costs. And according to the experimental data measured in Table 1, compared with batteries made using pure lithium iron phosphate, the lithium iron phosphate and lithium nickelate composite obtained by the lithium-rich material preparation method of this application, when used in the battery positive electrode, can increase the gram capacity of the battery positive electrode material and significantly extend the battery's cycle life.

[0115] The preferred embodiments of the present application are described in detail above in conjunction with the accompanying drawings. However, the present application is not limited to the specific details in the above embodiments. Within the technical concept of the present application, various simple modifications can be made to the technical solution of the present application, and these simple modifications all fall within the scope of protection of the present application.

[0116] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any appropriate manner unless there is any contradiction. In order to avoid unnecessary repetition, this application will not further describe various possible combinations.

[0117] In addition, the various implementation methods of the present application may be arbitrarily combined, and as long as they do not violate the concept of the present application, they should also be regarded as the contents disclosed in the present application.

Claims

1. A method for preparing a lithium-rich material, characterized in that: The preparation method comprises the following steps: Acid leaching treatment, subjecting the nickel-iron alloy to acid leaching treatment, and then filtering treatment to obtain an acidic solution containing nickel ions and ferrous ions; adding alkali to precipitate the acidic solution, and adjusting the pH value of the solution to 3-10 to obtain nickel hydroxide and ferrous hydroxide precipitates, and filtering to obtain a precipitate; Low-temperature calcination, drying the precipitate, and then low-temperature calcination to decompose the precipitate to obtain a mixture of nickel oxide and ferrous oxide; High-temperature calcination: the mixture is initially calcined together with lithium hydrogen phosphate powder and a carbon source at high temperature, and then lithium oxide is added and calcined at high temperature for a second time to obtain a lithium iron phosphate and lithium nickelate composite.

2. The method for preparing lithium-rich materials according to claim 1, wherein: Before the acid leaching treatment, the preparation method further comprises: high-temperature insulation, wherein the nickel-iron alloy is subjected to high-temperature insulation treatment.

3. The method for preparing lithium-rich materials according to claim 2, wherein: In the high-temperature insulation step, the insulation temperature is 700° C.-1000° C., and the insulation time is 0.5 h-2 h.

4. The method for preparing a lithium-rich material according to claim 1 or 2, wherein: In the nickel-iron alloy, the weight ratio of nickel is 5%-20%, and the weight ratio of iron is 77.5%-94.5%; And / or, the particle size of the nickel-iron alloy is in the range of 0.3 μm to 50 μm.

5. The method for preparing lithium-rich materials according to claim 1, wherein: In the acid leaching step, the treatment temperature is 25° C.-100° C., and the treatment time is 0.5 h-3 h.

6. The method for preparing lithium-rich materials according to claim 1, wherein: Before the low-temperature calcination step, the lithium-rich material preparation method further comprises: washing the precipitate to neutrality.

7. The method for preparing lithium-rich materials according to claim 1, wherein: In the low-temperature calcination step, the calcination temperature increases gradually within the range of 230° C. to 500° C., and the calcination time is 4 h to 8 h.

8. The method for preparing lithium-rich materials according to claim 1, wherein: In the high-temperature calcination step, the calcination temperature of the initial high-temperature calcination is 500° C.-600° C., and the calcination time is 4 h-8 h; And / or, the calcination temperature of the secondary high-temperature calcination is 600° C.-750° C., and the calcination time is 12 h-24 h; And / or, the carbon source includes at least one of glucose, sucrose, carbon black, phenolic resin, and carbon graphite.

9. A lithium-rich material, characterized in that The lithium-rich material is prepared by the lithium-rich material preparation method according to any one of claims 1 to 8.

10. A positive electrode plate, characterized in that: The positive electrode plate includes the lithium-rich material as claimed in claim 9.

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