Attenuation-resistant electric bicycle lithium battery positive electrode material and preparation method thereof
By employing multi-material composite, element doping, and surface coating processes in the preparation method, the problems of insufficient stability and cycle life of lithium battery cathode materials for electric bicycles under high-temperature environments have been solved, achieving long battery life and high energy density.
Patent Information
- Application Number
- CN202511044287.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-07-28
- Publication Date
- 2025-11-21
AI Technical Summary
Existing lithium battery cathode materials for electric bicycles lack stability and cycle life under high-temperature conditions, making it difficult to meet the requirements for long-term use and resulting in a short battery life.
Using lithium iron phosphate, lithium nickel cobalt manganese oxide, lithium-rich manganese-based oxide, and magnesium nitrate as raw materials, a degradation-resistant lithium battery cathode material for electric bicycles is prepared through pretreatment, doping reaction, and surface coating processes. The process includes steps such as ball milling, drying, doping, and coating to form a stable crystal structure and surface coating layer.
It improves the cycle stability and specific capacity of the cathode material, extends the battery's lifespan, provides longer-lasting power support, and resists battery degradation during long-term use.
Smart Images
Figure CN120998957A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of lithium battery technology, and in particular to a cathode material for a lithium battery with resistance to battery degradation in electric bicycles and its preparation method. Background Technology
[0002] With the global advocacy for green travel and the continuous development of electric bicycle technology, electric bicycles have become an important means of transportation for short-distance daily commutes due to their convenience, environmental friendliness, and economy. Lithium batteries, as the core power source of electric bicycles, directly determine key indicators such as range, lifespan, safety, and operating costs. Cathode materials, as a crucial component of lithium batteries, play a vital role in the charging and discharging process. They not only determine the battery's energy density but also significantly impact cycle life, charging and discharging efficiency, and safety.
[0003] Currently, the most common cathode materials for electric bicycle lithium batteries on the market include lithium iron phosphate and lithium nickel cobalt manganese oxide. Lithium iron phosphate has advantages such as high safety, long cycle life, and low cost.
[0004] However, the existing lithium iron phosphate batteries have relatively low energy density and cannot meet the requirements for long-range operation. While lithium nickel cobalt manganese oxide batteries have higher energy density and can provide longer range, their stability and cycle life under high-temperature conditions need to be improved. Based on the above, they are difficult to meet the requirements for long-term use of electric bicycles, and their battery life is relatively short. Summary of the Invention
[0005] The purpose of this invention is to provide a lithium-ion battery cathode material for electric bicycles with resistance to degradation and its preparation method, aiming to solve the technical problem that existing lithium-ion battery cathode materials are difficult to meet the requirements of long-term use of electric bicycles and have a short battery life.
[0006] To achieve the above objectives, the present invention employs a lithium-ion battery cathode material for electric bicycles with resistance to degradation, comprising the following raw materials: lithium iron phosphate, lithium nickel cobalt manganese oxide, lithium-rich manganese-based oxide, and magnesium nitrate.
[0007] This invention also provides a method for preparing a lithium-ion battery cathode material resistant to battery degradation in electric bicycles, comprising the following steps:
[0008] Various materials for preparing lithium battery cathode materials for electric bicycles were obtained, including lithium iron phosphate, lithium nickel cobalt manganese oxide and lithium-rich manganese-based materials, and composite materials were obtained through pretreatment.
[0009] Magnesium nitrate material was obtained according to the doping ratio, and the magnesium nitrate material was then subjected to a doping reaction with the composite material.
[0010] The coating solution is prepared according to the coating requirements, a surface coating layer is prepared, and the surface coating layer is attached to the composite material.
[0011] Prepare the finished lithium battery cathode material for electric bicycles, and then seal and store the finished product.
[0012] Among them, in the step of obtaining various materials for preparing lithium battery cathode materials for electric bicycles, including lithium iron phosphate, lithium nickel cobalt manganese oxide, and lithium-rich manganese-based materials, and obtaining composite materials through pretreatment:
[0013] High-purity lithium iron phosphate, lithium nickel cobalt manganese oxide, and lithium-rich manganese-based materials were selected as the basic raw materials.
[0014] The basic raw materials were chemically analyzed, and the content of each element was detected by X-ray fluorescence spectrometry to ensure that they met the preparation requirements. The microstructure of the basic raw materials was observed by scanning electron microscopy to understand their particle size and distribution.
[0015] Lithium iron phosphate, lithium nickel cobalt manganese oxide, and lithium-rich manganese-based materials were accurately weighed in a mass ratio of 3:5:2, placed in a container, and the three raw materials were initially mixed evenly using a stirring device.
[0016] The mixed raw materials are transferred to a ball mill for ball milling. The ball-to-material ratio is 10:1, the speed of the ball mill is 300-400 r / min, and the ball milling time is 6-8 h to obtain a fine and uniform composite slurry. Zirconia balls are used as the ball milling media.
[0017] The composite slurry was transferred to a vacuum drying oven and dried at 80–100°C for 12–15 hours to remove anhydrous ethanol and moisture, resulting in dried composite powder.
[0018] In the step of obtaining magnesium nitrate material according to the doping ratio and then reacting the magnesium nitrate material with the composite material:
[0019] Based on the mass of lithium iron phosphate in the composite material, the required amount of magnesium nitrate is calculated according to the doping ratio. The weighed magnesium nitrate is dissolved in deionized water to prepare a solution with a concentration of 0.2–0.4 mol / L. The solution is stirred for 30 minutes to obtain a homogeneous magnesium nitrate solution.
[0020] The dried composite material powder was slowly added to the magnesium nitrate solution, and a glass rod was used to continuously stir to ensure that the composite material was in full contact with the solution.
[0021] The mixed solution was transferred to a water bath and stirred for 4 to 6 hours at 60 to 70°C to allow magnesium to be uniformly adsorbed onto the surface of lithium iron phosphate and to undergo a doping reaction.
[0022] The mixed solution after the doping reaction is transferred to an evaporating dish and evaporated to dryness in a water bath at 80-90°C to obtain a doped precursor. The doped precursor is placed in a muffle furnace and heated to 550-600°C at a heating rate of 5°C / min under nitrogen protection, and held at that temperature for 5-6 hours to allow magnesium to be uniformly doped into the crystal structure of lithium iron phosphate, forming a magnesium-doped composite material.
[0023] In the step of calculating the required amount of magnesium nitrate based on the mass of lithium iron phosphate in the composite material and the doping ratio, the weighed magnesium nitrate is dissolved in deionized water to prepare a solution with a concentration of 0.2–0.4 mol / L. The solution is then stirred for 30 minutes to obtain a homogeneous magnesium nitrate solution.
[0024] The magnesium doping amount is 1% to 3% of the mass of lithium iron phosphate.
[0025] Among them, the steps of preparing the coating solution according to the coating requirements, preparing the surface coating layer, and attaching the surface coating layer to the composite material are as follows:
[0026] Weigh out carbon nanotubes and alumina, mix them in a mass ratio of 1:1, put them in a mortar, and grind them gently for 30 to 60 minutes to ensure that the two materials are fully mixed and homogeneous, thus obtaining a mixture.
[0027] The ground mixture was added to a 95% ethanol solution and ultrasonically dispersed for 2-3 hours using an ultrasonic disperser to uniformly disperse the carbon nanotubes and alumina in the ethanol, forming a stable coating solution.
[0028] Magnesium-doped composite material was added to the coating solution and ultrasonically dispersed for 1-2 hours using an ultrasonic disperser to ensure that the coating material was fully adsorbed on the surface of the composite material. The mixed solution was then transferred to a rotary evaporator and rotary evaporated at 70-80°C to remove ethanol and obtain the coating precursor.
[0029] The coating precursor is placed in a tube furnace and heated to 350-400°C at a heating rate of 5°C / min under nitrogen protection. The temperature is held for 2-3 hours to allow carbon nanotubes and alumina to form a stable coating layer on the surface of the composite material, thus obtaining the surface-coated cathode material.
[0030] In the steps of preparing the finished lithium battery cathode material for electric bicycles, and sealing and storing the finished product:
[0031] Place the surface-coated positive electrode material into a mortar and grind it gently for 30 to 60 minutes. Then, use a standard sieve to sieve and select positive electrode material particles with a particle size of 5 to 15 μm.
[0032] The sieved cathode material is placed in a vacuum drying oven and vacuum dried at 100-120℃ for 8-10 hours to remove moisture and residual organic matter from the surface of the material.
[0033] After drying, the positive electrode material is placed in a sealed plastic bag, desiccant is added, and the bag is sealed and stored in a dry, cool environment.
[0034] This invention discloses a lithium-ion battery cathode material for electric bicycles with resistance to battery degradation and its preparation method. The cathode material comprises the following raw materials: lithium iron phosphate, lithium nickel cobalt manganese oxide, lithium-rich manganese-based oxide, and magnesium nitrate. The preparation method includes the following steps: First, various materials for preparing the cathode material are obtained, including lithium iron phosphate, lithium nickel cobalt manganese oxide, and lithium-rich manganese-based oxide, and a composite material is obtained through pretreatment. Then, magnesium nitrate is obtained according to the doping ratio, and the magnesium nitrate is reacted with the composite material. Next, a coating solution is prepared according to the coating requirements to prepare a surface coating layer. The surface coating layer is then attached to the composite material. Finally, the finished lithium-ion battery cathode material for electric bicycles is prepared. The finished product is then sealed, packaged, and stored. During this process, the advantages of different materials are fully utilized through multi-material composites. Furthermore, element doping and surface coating processes effectively improve the crystal structure and surface properties of the materials, reducing structural changes and side reactions during charging and discharging, and enhancing the cycle stability of the materials. The cathode material is then treated with a special preparation process. Based on the above, the specific capacity of the cathode material is increased, providing longer-lasting power for electric bicycles and effectively resisting battery degradation during long-term use, thus extending battery life. Through these methods, the specific capacity of the cathode material is increased, providing longer-lasting power for electric bicycles and effectively resisting battery degradation during long-term use, thus extending battery life. Attached Figure Description
[0035] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0036] Figure 1 This is a flowchart illustrating the steps of the method for preparing the attenuation-resistant lithium battery cathode material for electric bicycles according to the present invention.
[0037] Figure 2 This is a flowchart of steps S100 of the present invention.
[0038] Figure 3This is a flowchart of steps S200 of the present invention.
[0039] Figure 4 This is a flowchart of steps S300 of the present invention.
[0040] Figure 5 This is a flowchart of steps S400 of the present invention. Detailed Implementation
[0041] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this application.
[0042] The terminology used in this application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The singular forms “a,” “the,” and “the” used in this application and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the term “and / or” as used herein refers to and includes any or all possible combinations of one or more of the associated listed items.
[0043] It should be understood that although the terms first, second, third, etc., may be used in this application to describe various information, such information should not be limited to these terms. These terms are only used to distinguish information of the same type from one another. For example, without departing from the scope of this application, first information may also be referred to as second information, and similarly, second information may also be referred to as first information. Depending on the context, the word "if" as used herein may be interpreted as "when," "when," or "in response to determination."
[0044] This invention provides a cathode material for a lithium-ion battery for electric bicycles that is resistant to degradation, comprising the following raw materials: lithium iron phosphate, lithium nickel cobalt manganese oxide, lithium-rich manganese-based oxide, and magnesium nitrate.
[0045] Please see Figures 1-5 The present invention also provides a method for preparing a lithium-ion battery cathode material resistant to battery degradation in electric bicycles, comprising the following steps:
[0046] S100: Obtain various materials for preparing lithium battery cathode materials for electric bicycles, including lithium iron phosphate, lithium nickel cobalt manganese oxide, and lithium-rich manganese-based materials, and obtain composite materials through pretreatment.
[0047] In this embodiment, various materials for preparing the positive electrode material of the electric bicycle lithium battery are obtained, including lithium iron phosphate, lithium nickel cobalt manganese oxide, and lithium-rich manganese-based oxide. A composite material is obtained through pretreatment. By combining multiple materials, the advantages of different materials are fully utilized, improving the specific capacity of the positive electrode material and providing longer-lasting power for the electric bicycle. The specific process is as follows:
[0048] S101: High-purity lithium iron phosphate, lithium nickel cobalt manganese oxide, and lithium-rich manganese-based materials are selected as basic raw materials;
[0049] S102: The basic raw materials are chemically analyzed, and the content of each element is detected by X-ray fluorescence spectrometry to ensure that they meet the preparation requirements. The microstructure of the basic raw materials is observed by scanning electron microscopy to understand their particle size and distribution.
[0050] S103: Accurately weigh lithium iron phosphate, lithium nickel cobalt manganese oxide and lithium-rich manganese-based material according to a mass ratio of 3:5:2, put them into a container, and use a stirring device to initially mix the three raw materials evenly.
[0051] S104: Transfer the mixed raw materials to a ball mill for ball milling. The ball-to-material ratio is 10:1, the speed of the ball mill is 300-400 r / min, and the ball milling time is 6-8 h to obtain a fine and uniform composite slurry. Zirconia balls are used as the ball milling media.
[0052] S105: Transfer the composite slurry to a vacuum drying oven and dry it at 80-100℃ for 12-15 hours to remove anhydrous ethanol and moisture, and obtain dried composite powder.
[0053] In the above process, high-purity lithium iron phosphate (LiFePO4) and lithium nickel cobalt manganese oxide (LiNi) are selected. x CoγMn 1-x- y O2) and lithium-rich manganese-based materials (Li 1+x Mn yUsing O2 as the basic raw material, the chemical composition of the basic raw material was analyzed. The content of each element was detected by X-ray fluorescence spectrometry (XRF) to ensure that it met the preparation requirements. The microstructure of the basic raw material was observed by scanning electron microscopy (SEM) to understand its particle size and distribution. Then, lithium iron phosphate, lithium nickel cobalt manganese oxide, and lithium-rich manganese-based material were accurately weighed at a mass ratio of 3:5:2 and placed in a container. The three raw materials were initially mixed evenly using a stirring device. The mixed raw materials were then transferred to a ball mill for ball milling. The ball-to-material ratio was 10:1, the ball mill speed was 300-400 r / min, and the ball milling time was 6-8 h to obtain a fine and uniform composite slurry. Zirconia balls were used as the ball milling media. The composite slurry was then transferred to a vacuum drying oven and dried at 80-100℃ for 12-15 h to remove anhydrous ethanol and water, resulting in a dried composite powder.
[0054] S200: Obtain magnesium nitrate material according to the doping ratio, and then carry out a doping reaction between the magnesium nitrate material and the composite material.
[0055] In this embodiment, magnesium nitrate material is obtained according to the doping ratio, and the magnesium nitrate material is then subjected to a doping reaction with the composite material. The elemental doping and surface coating processes effectively improve the crystal structure and surface properties of the material, reduce structural changes and side reactions during charge and discharge, thereby improving the cycle stability of the material. The specific process is as follows:
[0056] S201: Based on the mass of lithium iron phosphate in the composite material, calculate the required amount of magnesium nitrate according to the doping ratio, and dissolve the weighed magnesium nitrate in deionized water to prepare a solution with a concentration of 0.2–0.4 mol / L. Stir the solution for 30 minutes to obtain a homogeneous magnesium nitrate solution;
[0057] S202: Slowly add the dried composite material powder to the magnesium nitrate solution, and continuously stir with a glass rod to ensure that the composite material is in full contact with the solution;
[0058] S203: Transfer the mixed solution to a water bath and stir it at 60-70°C for 4-6 hours to allow magnesium to be uniformly adsorbed on the surface of lithium iron phosphate and to undergo a doping reaction.
[0059] S204: The mixed solution after the doping reaction is transferred to an evaporating dish and evaporated to dryness in a water bath at 80-90℃ to obtain the doped precursor. The doped precursor is placed in a muffle furnace and heated to 550-600℃ at a heating rate of 5℃ / min under nitrogen protection, and held for 5-6 hours to allow magnesium to be uniformly doped into the crystal structure of lithium iron phosphate, forming a magnesium-doped composite material.
[0060] In the above process, based on the mass of lithium iron phosphate in the composite material, the amount of magnesium nitrate required is calculated according to the doping ratio (the amount of magnesium doping is 1% to 3% of the mass of lithium iron phosphate), and the weighed magnesium nitrate is dissolved in deionized water to prepare a solution with a concentration of 0.2 to 0.4 mol / L. The solution was stirred for 30 minutes to obtain a homogeneous magnesium nitrate solution. Then, the dried composite material powder was slowly added to the magnesium nitrate solution, and the mixture was continuously stirred with a glass rod to ensure full contact between the composite material and the solution. The mixed solution was then transferred to a water bath and stirred for 4–6 hours at 60–70°C to allow magnesium to be uniformly adsorbed onto the surface of lithium iron phosphate and to undergo a doping reaction. The mixed solution after the doping reaction was then transferred to an evaporating dish and evaporated to dryness in a water bath at 80–90°C to obtain a doped precursor. The doped precursor was then placed in a muffle furnace and heated to 550–600°C at a heating rate of 5°C / min under nitrogen protection and held for 5–6 hours to allow magnesium to be uniformly doped into the crystal structure of lithium iron phosphate, forming a magnesium-doped composite material.
[0061] S300: Prepare a coating solution according to the coating requirements, prepare a surface coating layer, and attach the surface coating layer to the composite material.
[0062] In this embodiment, a coating solution is prepared according to the coating requirements to prepare a surface coating layer, and the surface coating layer is then attached to the composite material. The specific process is as follows:
[0063] S301: Weigh carbon nanotubes and alumina, mix them in a mass ratio of 1:1, put them in a mortar, and grind them gently for 30 to 60 minutes to ensure that the two materials are fully mixed and homogeneous to obtain a mixture.
[0064] S302: Add the ground mixture to a 95% ethanol solution and use an ultrasonic disperser to ultrasonically disperse for 2-3 hours to uniformly disperse carbon nanotubes and alumina in the ethanol to form a stable coating solution.
[0065] S303: Add the magnesium-doped composite material to the coating solution and continue to disperse it using an ultrasonic disperser for 1-2 hours to ensure that the coating material is fully adsorbed on the surface of the composite material. Then, transfer the mixed solution to a rotary evaporator and perform rotary evaporation at 70-80°C to remove ethanol and obtain the coating precursor.
[0066] S304: The coating precursor is placed in a tube furnace and heated to 350-400°C at a heating rate of 5°C / min under nitrogen protection. The temperature is held for 2-3 hours to allow carbon nanotubes and alumina to form a stable coating layer on the surface of the composite material, thus obtaining the surface-coated cathode material.
[0067] In the above process, carbon nanotubes and alumina are weighed and mixed at a mass ratio of 1:1. The mixture is placed in a mortar and gently ground for 30-60 minutes to ensure thorough and uniform mixing. The ground mixture is then added to a 95% ethanol solution and ultrasonically dispersed for 2-3 hours to ensure uniform dispersion of carbon nanotubes and alumina in the ethanol, forming a stable coating solution. Magnesium-doped composite material is then added to the coating solution and ultrasonically dispersed for another 1-2 hours to ensure full adsorption of the coating material onto the surface of the composite material. The mixed solution is then transferred to a rotary evaporator and rotary evaporated at 70-80°C to remove the ethanol, yielding a coating precursor. The coating precursor is then placed in a tube furnace and heated to 350-400°C at a rate of 5°C / min under nitrogen protection, and held for 2-3 hours to allow carbon nanotubes and alumina to form a stable coating layer on the surface of the composite material, resulting in a surface-coated cathode material.
[0068] S400: Prepare finished lithium battery cathode materials for electric bicycles, and seal and store the finished products.
[0069] In this embodiment, the finished lithium battery cathode material for electric bicycles is prepared, and the finished product is sealed, packaged, and stored. The specific process is as follows:
[0070] S401: Place the surface-coated positive electrode material into a mortar and grind it gently for 30 to 60 minutes. Use a standard sieve to sieve and select positive electrode material particles with a particle size of 5 to 15 μm.
[0071] S402: Place the sieved cathode material into a vacuum drying oven and vacuum dry it at 100-120℃ for 8-10 hours to remove moisture and residual organic matter from the surface of the material.
[0072] S403: After drying, pack the positive electrode material into a sealed plastic bag, add a desiccant, seal the package, and store it in a dry, cool environment.
[0073] In the above process, the surface-coated positive electrode material is placed in a mortar and gently ground for 30-60 minutes. It is then sieved using a standard sieve to select positive electrode material particles with a particle size of 5-15 μm. The sieved positive electrode material is then placed in a vacuum drying oven and vacuum dried at 100-120℃ for 8-10 hours to remove moisture and residual organic matter from the material surface. The dried positive electrode material is then packed into a sealed plastic bag, desiccant is added for sealing, and it is stored in a dry and cool environment.
[0074] Other embodiments of this application will readily occur to those skilled in the art upon consideration of the specification and practice of the disclosure herein. This application is intended to cover any variations, uses, or adaptations of this application that follow the general principles of this application and include common knowledge or customary techniques in the art not disclosed herein.
[0075] It should be understood that this application is not limited to the precise structure described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope.
Claims
1. A cathode material for a lithium-ion battery in an electric bicycle that is resistant to battery degradation, characterized in that, It consists of the following raw materials: Lithium iron phosphate, lithium nickel cobalt manganese oxide, lithium-rich manganese-based oxide, and magnesium nitrate.
2. A cathode material for a lithium-ion battery with resistance to battery degradation in electric bicycles and a method for preparing the same, wherein the cathode material is prepared as described in claim 1, characterized in that... Includes the following steps: Various materials for preparing lithium battery cathode materials for electric bicycles were obtained, including lithium iron phosphate, lithium nickel cobalt manganese oxide and lithium-rich manganese-based materials, and composite materials were obtained through pretreatment. Magnesium nitrate material was obtained according to the doping ratio, and the magnesium nitrate material was then subjected to a doping reaction with the composite material. The coating solution is prepared according to the coating requirements, a surface coating layer is prepared, and the surface coating layer is attached to the composite material. Prepare the finished lithium battery cathode material for electric bicycles, and then seal and store the finished product.
3. The method for preparing the attenuation-resistant lithium battery positive electrode material for electric bicycles as described in claim 2, characterized in that, In the process of obtaining various materials for preparing lithium-ion battery cathode materials for electric bicycles, including lithium iron phosphate, lithium nickel cobalt manganese oxide, and lithium-rich manganese-based materials, and obtaining composite materials through pretreatment: High-purity lithium iron phosphate, lithium nickel cobalt manganese oxide, and lithium-rich manganese-based materials were selected as the basic raw materials. The basic raw materials were chemically analyzed, and the content of each element was detected by X-ray fluorescence spectrometry to ensure that they met the preparation requirements. The microstructure of the basic raw materials was observed by scanning electron microscopy to understand their particle size and distribution. Lithium iron phosphate, lithium nickel cobalt manganese oxide, and lithium-rich manganese-based materials were accurately weighed in a mass ratio of 3:5:2, placed in a container, and the three raw materials were initially mixed evenly using a stirring device. The mixed raw materials are transferred to a ball mill for ball milling. The ball-to-material ratio is 10:1, the speed of the ball mill is 300-400 r / min, and the ball milling time is 6-8 h to obtain a fine and uniform composite slurry. Zirconia balls are used as the ball milling media. The composite slurry was transferred to a vacuum drying oven and dried at 80–100°C for 12–15 hours to remove anhydrous ethanol and moisture, resulting in dried composite powder.
4. The method for preparing the attenuation-resistant lithium battery positive electrode material for electric bicycles as described in claim 2, characterized in that, In the steps of obtaining magnesium nitrate material according to the doping ratio and then reacting the magnesium nitrate material with the composite material: Based on the mass of lithium iron phosphate in the composite material, the required amount of magnesium nitrate is calculated according to the doping ratio. The weighed magnesium nitrate is dissolved in deionized water to prepare a solution with a concentration of 0.2–0.4 mol / L. The solution is stirred for 30 minutes to obtain a homogeneous magnesium nitrate solution. The dried composite material powder was slowly added to the magnesium nitrate solution, and a glass rod was used to continuously stir to ensure that the composite material was in full contact with the solution. The mixed solution was transferred to a water bath and stirred for 4 to 6 hours at 60 to 70°C to allow magnesium to be uniformly adsorbed onto the surface of lithium iron phosphate and to undergo a doping reaction. The mixed solution after the doping reaction is transferred to an evaporating dish and evaporated to dryness in a water bath at 80-90°C to obtain a doped precursor. The doped precursor is placed in a muffle furnace and heated to 550-600°C at a heating rate of 5°C / min under nitrogen protection, and held at that temperature for 5-6 hours to allow magnesium to be uniformly doped into the crystal structure of lithium iron phosphate, forming a magnesium-doped composite material.
5. The method for preparing the attenuation-resistant lithium battery positive electrode material for electric bicycles as described in claim 4, characterized in that, Based on the mass of lithium iron phosphate in the composite material, the required amount of magnesium nitrate is calculated according to the doping ratio. The weighed magnesium nitrate is dissolved in deionized water to prepare a solution with a concentration of 0.2–0.4 mol / L. The solution is then stirred for 30 minutes to obtain a homogeneous magnesium nitrate solution. The magnesium doping amount is 1% to 3% of the mass of lithium iron phosphate.
6. The method for preparing the attenuation-resistant lithium battery positive electrode material for electric bicycles as described in claim 2, characterized in that, In the steps of preparing a coating solution according to coating requirements, preparing a surface coating layer, and attaching the surface coating layer to the composite material: Weigh out carbon nanotubes and alumina, mix them in a mass ratio of 1:1, put them in a mortar, and grind them gently for 30 to 60 minutes to ensure that the two materials are fully mixed and homogeneous, thus obtaining a mixture. The ground mixture was added to a 95% ethanol solution and ultrasonically dispersed for 2-3 hours using an ultrasonic disperser to uniformly disperse the carbon nanotubes and alumina in the ethanol, forming a stable coating solution. Magnesium-doped composite material was added to the coating solution and ultrasonically dispersed for 1-2 hours using an ultrasonic disperser to ensure that the coating material was fully adsorbed on the surface of the composite material. The mixed solution was then transferred to a rotary evaporator and rotary evaporated at 70-80°C to remove ethanol and obtain the coating precursor. The coating precursor is placed in a tube furnace and heated to 350-400°C at a heating rate of 5°C / min under nitrogen protection. The temperature is held for 2-3 hours to allow carbon nanotubes and alumina to form a stable coating layer on the surface of the composite material, thus obtaining the surface-coated cathode material.
7. The method for preparing the attenuation-resistant lithium battery positive electrode material for electric bicycles as described in claim 2, characterized in that, In the steps of preparing the finished lithium battery cathode material for electric bicycles, and sealing and storing the finished product: Place the surface-coated positive electrode material into a mortar and grind it gently for 30 to 60 minutes. Then, use a standard sieve to sieve and select positive electrode material particles with a particle size of 5 to 15 μm. The sieved cathode material is placed in a vacuum drying oven and vacuum dried at 100-120℃ for 8-10 hours to remove moisture and residual organic matter from the surface of the material. After drying, the positive electrode material is placed in a sealed plastic bag, desiccant is added, and the bag is sealed and stored in a dry, cool environment.