Preparation method of low-temperature-resistant lithium ion energy storage battery and battery prepared thereby

Abstract

The application discloses a preparation method of a low-temperature-resistant lithium ion energy storage battery and the battery. Iron source, manganese source, phosphorus source and ascorbic acid are dissolved in deionized water, mixed uniformly to obtain a first solution; a lithium source is dissolved in deionized water, mixed uniformly to obtain a second solution; the second solution is uniformly and continuously added into the first solution, stirred and mixed uniformly to obtain a mixed solution, and the mixed solution is subjected to superfine grinding treatment to obtain a first slurry; the first slurry is subjected to constant-temperature reaction, then is subjected to suction filtration and washing, and is vacuum dried to obtain a precursor; the precursor and a carbon source, conductive carbon black and graphene oxide are ground, mixed uniformly and subjected to refining treatment to obtain a second slurry; and the second slurry is subjected to segmented sintering in an N2 environment to obtain the low-temperature-resistant lithium ion energy storage battery. The battery is prepared by using the preparation method. The application has excellent charge-discharge specific capacity, good cycle performance, excellent low-temperature electrochemical performance, simple preparation and is suitable for industrialized production.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery technology, and in particular to a method for preparing a low-temperature resistant lithium-ion energy storage battery and the battery obtained therefrom. Background Technology

[0002] Railway lines in high-altitude and frigid regions often feature numerous steep slope engineering projects, where dynamic forces such as earthquakes, freeze-thaw cycles, and rainfall are prominent, easily triggering severe engineering disasters. Therefore, conducting long-term automated monitoring of slope stability is crucial for ensuring the safety of on-site construction and railway operation. Different types and frequencies of monitoring systems have significantly different power consumption levels and use different power batteries. However, given the extremely low and even ultra-low temperature conditions in high-altitude and frigid regions, most batteries cannot meet the daily power requirements of the monitoring systems. Currently, the most common batteries used in high-altitude and frigid regions are lithium-ion batteries, which are further divided into three types: lithium manganese oxide batteries, lithium iron phosphate batteries, and ternary lithium-ion batteries.

[0003] Lithium manganese oxide battery cathode materials possess numerous advantages, including high safety and good low-temperature performance. However, the cathode material itself is unstable and prone to decomposition, generating gas. It is often used in combination with other materials to reduce cell costs, but its cycle life decays rapidly, it is prone to swelling, has poor high-temperature performance, and a relatively short lifespan, limiting its applications. Ternary lithium-ion batteries, due to their high energy density, have relatively high charge / discharge specific capacity, but generally exhibit O2O2 during charge / discharge processes. 2- oxidation, Ni 2+ / Li + It suffers from several problems, such as cation mixing and the tendency for surface alkaline oxides to undergo side reactions, resulting in poor cycle stability and limiting its application.

[0004] Compared to the two types of batteries mentioned above, lithium iron phosphate (LFP) batteries have several advantages, including excellent thermal stability, low cost, and long lifespan. However, LFP materials have poor low-temperature charge-discharge performance. When the temperature is below 0°C, the energy conversion and storage capacity of lithium-ion batteries rapidly declines, causing performance degradation or failure. This severely hinders the promotion and development of lithium-ion batteries, increases their usage costs and risks, and reduces energy utilization. Therefore, improving the low-temperature performance of LFP batteries is crucial for enhancing their electrochemical performance.

[0005] Chinese patent CN106340624A, "A method for preparing carbon-coated lithium iron phosphate nanorods", discloses a carbon-coated lithium iron phosphate nanorod. By coating the surface of lithium iron phosphate with carbon, the electrochemical performance of lithium iron phosphate at low temperature is improved. However, the discharge specific capacity of the carbon-coated lithium iron phosphate nanorod is low and the cycle performance is average. Its low-temperature electrochemical performance needs to be further improved.

[0006] Therefore, it is of great significance to develop a lithium-ion energy storage battery with high discharge specific capacity, good cycle performance, and excellent low-temperature electrochemical performance, as well as its preparation method and application. Summary of the Invention

[0007] The purpose of this invention is to provide a method for preparing a low-temperature resistant lithium-ion energy storage battery and the battery obtained therefrom, which solves at least one of the above-mentioned technical problems. The battery has excellent charge-discharge specific capacity, good cycle performance, excellent low-temperature electrochemical performance, is simple to prepare, and is suitable for industrial production.

[0008] The embodiments of the present invention are implemented as follows:

[0009] A method for preparing a low-temperature resistant lithium-ion energy storage battery, comprising:

[0010] S100 involves dissolving iron, manganese, phosphorus, and ascorbic acid in deionized water and mixing them thoroughly to obtain the first solution.

[0011] S200: Dissolve the lithium source in deionized water and mix thoroughly to obtain a second solution.

[0012] S300, the second solution is added dropwise to the first solution at a uniform rate, and the mixture is stirred and mixed evenly to obtain a mixed solution. The mixed solution is then subjected to ultrafine grinding to obtain a first slurry.

[0013] S400, the first slurry is subjected to a constant temperature reaction at 200℃~220℃, then filtered, washed, and vacuum dried to obtain the precursor.

[0014] S500: The precursor, carbon source, conductive carbon black, and graphene oxide are ground and mixed evenly, and refined to obtain a second slurry. The second slurry is then sintered in segments in an N2 environment to obtain a low-temperature resistant lithium-ion energy storage battery.

[0015] In a preferred embodiment of the present invention, in the above-mentioned method for preparing a low-temperature resistant lithium-ion energy storage battery, the iron source includes at least one of iron oxide, ferric sulfate, ferric phosphate, ferrous oxalate, and ferric nitrate.

[0016] The manganese source includes at least one of manganese dioxide, manganese tetroxide, and manganese acetate.

[0017] The phosphorus source includes at least one of phosphoric acid, ammonium monohydrogen phosphate, and ammonium dihydrogen phosphate.

[0018] The lithium source includes at least one of lithium hydroxide, lithium acetate, lithium carbonate, lithium nitrate, and lithium fluoride.

[0019] The technical advantages are as follows: iron oxide provides high stability; ferric sulfate and ferric nitrate are readily soluble in water; ferrous oxalate and ferric phosphate provide good electrochemical performance; manganese dioxide and manganese tetroxide provide excellent conductivity and stability; manganese acetate has good solubility and reactivity; lithium hydroxide and lithium carbonate are commonly used to improve the stability of materials, while lithium nitrate and lithium fluoride help improve low-temperature performance and conductivity. Through the synergistic effect of different compounds, the electrochemical performance and structural stability of the electrode material are effectively improved, enabling the prepared lithium-ion energy storage battery to maintain good electrochemical performance and stability even at low temperatures.

[0020] In a preferred embodiment of the present invention, in the above-mentioned method for preparing a low-temperature resistant lithium-ion energy storage battery, the molar ratio of iron to ascorbic acid in the first solution is Fe:C6H8O6=1:(0.4~0.6).

[0021] Its technical effect is that by adjusting the molar ratio of iron and ascorbic acid, the growth rate and final particle size of the precursor particles can be controlled, thus generating particles with ideal size and morphology, ensuring that ascorbic acid is evenly distributed in the solution, promoting the uniform distribution and dissolution of the iron source, and preventing the iron source from agglomerating or precipitating in the solution.

[0022] In a preferred embodiment of the present invention, in the above-mentioned method for preparing a low-temperature resistant lithium-ion energy storage battery, the molar ratio of lithium, iron, manganese and phosphorus in the mixed solution is Li:Fe:Mn:P = 3:0.96:0.04:1.

[0023] The technical advantages are as follows: ensuring that the cathode material has an appropriate crystal structure and electrochemical activity, while taking into account the conductivity and stability of the material; the appropriate doping of Mn helps to reduce the charge transfer impedance of the material and enhance the discharge capacity and efficiency of the battery at low temperatures; the appropriate Li:Fe:Mn molar ratio helps to form a favorable crystal structure, optimize the migration path of lithium ions, and improve the diffusion rate of lithium ions; the ratio of Fe to P is close to 1:1, while the ratio of Li is 3, which can form a stable lithium iron phosphate structure (LiFePO4) with high stability and safety. At the same time, a small amount of Mn doping (0.04) will not destroy this stable structure, further enhancing the overall stability of the material and reducing capacity decay.

[0024] In a preferred embodiment of the present invention, in the above-mentioned method for preparing a low-temperature resistant lithium-ion energy storage battery, in step S300, the stirring time of the second solution and the first solution is 10 min to 30 min.

[0025] The median particle diameter (D50) of the first slurry obtained after ultrafine grinding is 80 nm to 100 nm.

[0026] The technical benefits lie in optimizing the uniformity and particle size of the slurry. Nanoscale particles (80nm~100nm) can provide shorter lithium-ion migration paths, reduce battery internal resistance, and improve battery discharge efficiency.

[0027] In a preferred embodiment of the present invention, in the above-described method for preparing a low-temperature resistant lithium-ion energy storage battery, in step S400, the time for the first slurry to react at a constant temperature is 12 hours.

[0028] The vacuum drying temperature is 60℃~80℃, and the time is 2h~3h.

[0029] Its technical advantages are as follows: long-term constant temperature reaction helps to form a uniform precursor particle structure, ensuring the consistency of the chemical composition and crystal structure of the material, fully removing impurities in the precursor, and improving the purity of the material; controlling the drying conditions can effectively remove moisture and residual solvents from the material, ensuring uniform drying of the material, avoiding bubbles and pores in the subsequent sintering process, and avoiding material aging caused by excessive time.

[0030] In a preferred embodiment of the present invention, in the above-mentioned method for preparing a low-temperature resistant lithium-ion energy storage battery, the carbon source includes at least one of glucose, fructose, white sugar, citric acid, sucrose, and activated carbon.

[0031] Its technical advantages are as follows: glucose, fructose, white sugar, sucrose, etc. can be decomposed and carbonized under high temperature conditions to form a conductive carbon network, which can effectively improve the conductivity of electrode materials and promote the rapid transport of electrons; the carbon layer can improve the structural stability of the material and improve the cycle life of the battery.

[0032] In a preferred embodiment of the present invention, in the above-mentioned method for preparing a low-temperature resistant lithium-ion energy storage battery, the mass ratio of the precursor, carbon source, conductive carbon black and graphene oxide in the second slurry is precursor: carbon source: conductive carbon black: graphene oxide = 1:(0.04~0.06):0.02:0.03.

[0033] Its technical advantages are as follows: by optimizing the mass ratio of precursor, carbon source, conductive carbon black and graphene oxide, the conductivity, structural stability and low-temperature performance of electrode materials can be effectively improved, and the overall electrochemical performance and cycle life of low-temperature lithium-ion energy storage batteries can be significantly improved.

[0034] In a preferred embodiment of the present invention, in the above-mentioned method for preparing a low-temperature resistant lithium-ion energy storage battery, in step S500, the median diameter (D50) of the particles of the second slurry obtained after the refinement treatment is 40 nm to 50 nm.

[0035] The conditions for segmented sintering are: hold at 200℃ for 3 hours, then raise the temperature to 700℃ and sinter for 5 to 7 hours.

[0036] The technical advantages are as follows: After the second slurry is refined, the median diameter (D50) of the particles is 40nm to 50nm, which helps to increase the specific surface area of ​​the material, increase the contact area between the electrode material and the electrolyte, improve the electrode reaction rate and the energy density of the battery, reduce the diffusion path of lithium ions in the electrode material, promote the rapid diffusion of lithium ions and the efficient conduction of electrons, and improve the charge and discharge rate and power performance of the battery. The precisely controlled sintering process can reduce the porosity and defects inside the material, enabling the material particles to be tightly bonded, ensuring the structural uniformity and stability of the electrode material.

[0037] A low-temperature resistant lithium-ion energy storage battery is prepared using the preparation method of a low-temperature resistant lithium-ion energy storage battery as described above.

[0038] The beneficial effects of this invention are:

[0039] This invention prepares a carbon-coated manganese-doped lithium iron phosphate battery via a hydrothermal method. Carbon coating effectively prevents Fe oxidation in the lithium iron phosphate material and improves the electrical contact between materials. Adding conductive carbon black and graphene oxide to the carbon source further enhances the material's electronic conductivity, allowing for timely conduction of electrons gained or lost during electrochemical reactions, thus effectively improving the electrochemical performance of the lithium-ion energy storage battery. Furthermore, the doping of manganese ions non-equivalently replaces Fe sites in lithium iron phosphate, promoting the formation of favorable defects in the material's lattice, widening the diffusion channels for Li ions, reducing the resistance to Li ion diffusion along one-dimensional paths, and improving the diffusion kinetics of Li ions in the lattice. This, in turn, improves the material's rate performance and reduces resistance. The process improves the conductivity and charge / discharge specific capacity of the material. Ultrafine grinding effectively increases the contact area between materials, allowing magnesium ions to be fully dispersed and doped into lithium iron phosphate, increasing the active sites for the reaction, increasing the specific surface area of ​​the material, and improving the cycle reversibility and low-temperature performance. Further refining allows the carbon layer to fully coat the particle surface, hindering further particle growth, reducing the contact area between particles, decreasing the possibility of particle agglomeration, suppressing pulverization under high-rate charge / discharge, and minimizing the self-discharge phenomenon that easily occurs in nanoscale lithium iron phosphate. Ultimately, this results in a lithium-ion energy storage battery with excellent charge / discharge specific capacity, good cycle performance, and excellent low-temperature electrochemical performance. Attached Figure Description

[0040] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0041] Figure 1a This is a schematic diagram of the cycle performance and coulombic efficiency curves at -20°C and 0.5C for Example 1 of the preparation method of the low-temperature resistant lithium-ion energy storage battery of the present invention.

[0042] Figure 1b This is a schematic diagram of the cycle performance and coulombic efficiency curves at -20℃ and 1C for Example 1 of the preparation method of the low-temperature resistant lithium-ion energy storage battery of the present invention.

[0043] Figure 2a This is a schematic diagram of the cycle performance and coulombic efficiency curves at -40°C and 0.5C for Example 1 of the preparation method of the low-temperature resistant lithium-ion energy storage battery of the present invention.

[0044] Figure 2b This is a schematic diagram of the cycle performance and coulombic efficiency curves at -40°C and 0.5C for a comparative example of the preparation method of the low-temperature resistant lithium-ion energy storage battery of the present invention.

[0045] Figure 3a This is a schematic diagram of the charge-discharge curve at -40°C and 0.5C for Example 1 of the preparation method of the low-temperature resistant lithium-ion energy storage battery of the present invention.

[0046] Figure 3b This is a schematic diagram of the charge-discharge curve at -40°C and 0.5C, which is a comparative example of the preparation method of the low-temperature resistant lithium-ion energy storage battery of the present invention. Detailed Implementation

[0047] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of 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. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0048] An embodiment of the present invention provides a method for preparing a low-temperature resistant lithium-ion energy storage battery, comprising: S100, dissolving an iron source, a manganese source, a phosphorus source, and ascorbic acid in deionized water and mixing them evenly to obtain a first solution; S200, dissolving a lithium source in deionized water and mixing them evenly to obtain a second solution; S300, adding the second solution dropwise to the first solution at a uniform rate and stirring to mix evenly to obtain a mixed solution, and subjecting the mixed solution to ultrafine grinding to obtain a first slurry; S400, subjecting the first slurry to a constant temperature reaction at 200℃~220℃, followed by filtration, washing, and vacuum drying to obtain a precursor; S500, grinding and mixing the precursor, carbon source, conductive carbon black, and graphene oxide evenly and refining the mixture to obtain a second slurry, and sintering the second slurry in a N2 environment in stages to obtain a low-temperature resistant lithium-ion energy storage battery.

[0049] The iron source includes at least one of iron oxide, ferric sulfate, ferric phosphate, ferrous oxalate, and ferric nitrate; the manganese source includes at least one of manganese dioxide, manganese tetroxide, and manganese acetate; the phosphorus source includes at least one of phosphoric acid, ammonium hydrogen phosphate, and ammonium dihydrogen phosphate; and the lithium source includes at least one of lithium hydroxide, lithium acetate, lithium carbonate, lithium nitrate, and lithium fluoride.

[0050] The technical advantages are as follows: iron oxide provides high stability; ferric sulfate and ferric nitrate are readily soluble in water; ferrous oxalate and ferric phosphate provide good electrochemical performance; manganese dioxide and manganese tetroxide provide excellent conductivity and stability; manganese acetate has good solubility and reactivity; lithium hydroxide and lithium carbonate are commonly used to improve the stability of materials, while lithium nitrate and lithium fluoride help improve low-temperature performance and conductivity. Through the synergistic effect of different compounds, the electrochemical performance and structural stability of the electrode material are effectively improved, enabling the prepared lithium-ion energy storage battery to maintain good electrochemical performance and stability even at low temperatures.

[0051] In the first solution, the molar ratio of iron to ascorbic acid is Fe:C6H8O6=1:(0.4~0.6).

[0052] Its technical effect is that by adjusting the molar ratio of iron and ascorbic acid, the growth rate and final particle size of the precursor particles can be controlled, thus generating particles with ideal size and morphology, ensuring that ascorbic acid is evenly distributed in the solution, promoting the uniform distribution and dissolution of the iron source, and preventing the iron source from agglomerating or precipitating in the solution.

[0053] In the mixed solution, the molar ratio of lithium, iron, manganese and phosphorus is Li:Fe:Mn:P = 3:0.96:0.04:1.

[0054] The technical advantages are as follows: ensuring that the cathode material has an appropriate crystal structure and electrochemical activity, while taking into account the conductivity and stability of the material; the appropriate doping of Mn helps to reduce the charge transfer impedance of the material and enhance the discharge capacity and efficiency of the battery at low temperatures; the appropriate Li:Fe:Mn molar ratio helps to form a favorable crystal structure, optimize the migration path of lithium ions, and improve the diffusion rate of lithium ions; the ratio of Fe to P is close to 1:1, while the ratio of Li is 3, which can form a stable lithium iron phosphate structure (LiFePO4) with high stability and safety. At the same time, a small amount of Mn doping (0.04) will not destroy this stable structure, further enhancing the overall stability of the material and reducing capacity decay.

[0055] In S300, the stirring time of the second solution and the first solution is 10 min to 30 min; the median diameter (D50) of the particles of the first slurry obtained after ultrafine grinding is 80 nm to 100 nm.

[0056] The technical benefits lie in optimizing the uniformity and particle size of the slurry. Nanoscale particles (80nm~100nm) can provide shorter lithium-ion migration paths, reduce battery internal resistance, and improve battery discharge efficiency.

[0057] In S400, the first slurry is reacted at a constant temperature for 12 hours; the vacuum drying temperature is 60℃~80℃, and the time is 2 hours~3 hours.

[0058] Its technical advantages are as follows: long-term constant temperature reaction helps to form a uniform precursor particle structure, ensuring the consistency of the chemical composition and crystal structure of the material, fully removing impurities in the precursor, and improving the purity of the material; controlling the drying conditions can effectively remove moisture and residual solvents from the material, ensuring uniform drying of the material, avoiding bubbles and pores in the subsequent sintering process, and avoiding material aging caused by excessive time.

[0059] The carbon source includes at least one of glucose, fructose, white sugar, citric acid, sucrose, and activated carbon.

[0060] Its technical advantages are as follows: glucose, fructose, white sugar, sucrose, etc. can be decomposed and carbonized under high temperature conditions to form a conductive carbon network, which can effectively improve the conductivity of electrode materials and promote the rapid transport of electrons; the carbon layer can improve the structural stability of the material and improve the cycle life of the battery.

[0061] In the second slurry, the mass ratio of precursor, carbon source, conductive carbon black and graphene oxide is precursor: carbon source: conductive carbon black: graphene oxide = 1:(0.04~0.06):0.02:0.03.

[0062] Its technical advantages are as follows: by optimizing the mass ratio of precursor, carbon source, conductive carbon black and graphene oxide, the conductivity, structural stability and low-temperature performance of electrode materials can be effectively improved, and the overall electrochemical performance and cycle life of low-temperature lithium-ion energy storage batteries can be significantly improved.

[0063] In S500, the median diameter (D50) of the particles of the second slurry obtained after refinement treatment is 40nm~50nm; the conditions for segmented sintering are to hold at 200℃ for 3h, then raise the temperature to 700℃ and sinter for 5h~7h.

[0064] The technical advantages are as follows: After the second slurry is refined, the median diameter (D50) of the particles is 40nm to 50nm, which helps to increase the specific surface area of ​​the material, increase the contact area between the electrode material and the electrolyte, improve the electrode reaction rate and the energy density of the battery, reduce the diffusion path of lithium ions in the electrode material, promote the rapid diffusion of lithium ions and the efficient conduction of electrons, and improve the charge and discharge rate and power performance of the battery. The precisely controlled sintering process can reduce the porosity and defects inside the material, enabling the material particles to be tightly bonded, ensuring the structural uniformity and stability of the electrode material.

[0065] The present invention also provides a low-temperature resistant lithium-ion energy storage battery, which is prepared by the low-temperature resistant lithium-ion energy storage battery preparation method described above.

[0066] To better illustrate the purpose, technical solution, and advantages of this invention, the following embodiments are provided. All raw materials are commercially available; unless otherwise specified, the reagents, methods, and equipment used in this invention are conventional reagents, methods, and equipment in this technical field.

[0067] Example 1

[0068] A method for preparing a lithium-ion energy storage battery includes the following steps:

[0069] (1) Dissolve 4.8 mmol ferric sulfate, 0.2 mmol manganese dioxide, 5 mmol phosphoric acid and 2.5 mmol ascorbic acid in 30 mL of deionized water, mix well to obtain the first solution;

[0070] (2) Dissolve 15 mmol of lithium acetate in 20 mL of deionized water, mix well to obtain a second solution, add the second solution dropwise to the first solution at a uniform rate, stir for 20 min to mix well to obtain a mixed solution;

[0071] (3) The prepared mixed solution was ultra-fine ground until the particle D50 of slurry 1 was 80-100 nm, reacted at 220℃ for 12 h, filtered and washed, and vacuum dried at 60℃ for 3 h to obtain the precursor.

[0072] (4) Grind and mix 5g of the obtained precursor with 20mg of glucose, 10mg of conductive carbon black and 15mg of graphene oxide evenly, refine the slurry particles until the D50 is 40-50nm, sinter in sections under N2 protection, keep at 200℃ for 3h and then heat to 700℃ for 5h to obtain the lithium-ion energy storage battery.

[0073] Example 2

[0074] A method for preparing a lithium-ion energy storage battery includes the following steps:

[0075] (1) Dissolve 4.8 mmol iron oxide, 0.2 mmol manganese tetroxide, 5 mmol ammonium phosphate and 2 mmol ascorbic acid in 30 mL of deionized water, mix well to obtain the first solution;

[0076] (2) Dissolve 15 mmol of lithium carbonate in 20 mL of deionized water, mix well to obtain a second solution, add the second solution dropwise to the first solution at a uniform rate, stir for 20 min to mix well to obtain a mixed solution;

[0077] (3) The prepared mixed solution was ultra-fine ground until the particle D50 of slurry 1 was 80-100 nm, reacted at 200℃ for 12 h, filtered and washed, and vacuum dried at 80℃ for 2 h to obtain the precursor.

[0078] (4) Grind and mix 5g of the obtained precursor with 25mg of glucose, 10mg of conductive carbon black and 15mg of graphene oxide evenly, refine the slurry particles until the D50 is 40-50nm, sinter in sections under N2 protection, keep at 200℃ for 3h and then heat to 700℃ for 6h to obtain the lithium-ion energy storage battery.

[0079] Example 3

[0080] A method for preparing a lithium-ion energy storage battery includes the following steps:

[0081] (1) Dissolve 4.8 mmol ferrous oxalate, 0.2 mmol manganese acetate, 5 mmol dihydrogen phosphate and 3 mmol ascorbic acid in 30 mL of deionized water, mix well to obtain the first solution;

[0082] (2) Dissolve 15 mmol lithium nitrate in 20 mL deionized water, mix well to obtain a second solution, add the second solution dropwise to the first solution at a uniform rate, stir for 20 min to mix well to obtain a mixed solution;

[0083] (3) The prepared mixed solution was ultra-fine ground until the particle D50 of slurry 1 was 80-100 nm, reacted at 210℃ for 12 h, filtered and washed, and dried under vacuum at 70℃ for 2 h to obtain the precursor.

[0084] (4) Grind and mix 5g of the obtained precursor with 30mg of glucose, 10mg of conductive carbon black and 15mg of graphene oxide evenly, refine the slurry particles until the D50 is 40-50nm, sinter in sections under N2 protection, keep at 200℃ for 3h and then heat to 700℃ for 7h to obtain the lithium-ion energy storage battery.

[0085] Comparative Example 1

[0086] A method for preparing a lithium-ion energy storage battery includes the following steps:

[0087] (1) Dissolve 5 mmol ferric sulfate, 5 mmol phosphoric acid and 2.5 mmol ascorbic acid in 30 mL of deionized water, mix well to obtain the first solution;

[0088] (2) Dissolve 15 mmol of lithium acetate in 20 mL of deionized water, mix well to obtain a second solution, add the second solution dropwise to the first solution at a uniform rate, stir for 20 min to mix well to obtain a mixed solution;

[0089] (3) The prepared mixed solution was reacted at a constant temperature of 220℃ for 12h, filtered and washed, and dried under vacuum at 60℃ for 3h to obtain the precursor.

[0090] (4) Grind and mix 5g of the obtained precursor with 20mg of glucose, 10mg of conductive carbon black and 15mg of graphene oxide evenly, and sinter in sections under the protection of N2. After holding at 200℃ for 3h, the temperature is raised to 700℃ and sintered for 5h to obtain the lithium-ion energy storage battery.

[0091] Compared to Example 1, this comparative example only underwent carbon coating.

[0092] Comparative Example 2

[0093] A method for preparing a lithium-ion energy storage battery includes the following steps:

[0094] (1) Dissolve 4.8 mmol ferric sulfate, 0.2 mmol manganese dioxide, 5 mmol phosphoric acid and 2.5 mmol ascorbic acid in 30 mL of deionized water, mix well to obtain the first solution;

[0095] (2) Dissolve 15 mmol of lithium acetate in 20 mL of deionized water, mix well to obtain a second solution, add the second solution dropwise to the first solution at a uniform rate, stir for 20 min to mix well to obtain a mixed solution;

[0096] (3) The prepared mixed solution was ultra-fine ground until the particle D50 of slurry 1 was 80-100nm, reacted at 220℃ for 12h, filtered and washed, and vacuum dried at 60℃ for 3h to obtain the lithium-ion energy storage battery.

[0097] Compared to Example 1, this comparative example does not undergo carbon coating.

[0098] Comparative Example 3

[0099] A method for preparing a lithium-ion energy storage battery includes the following steps:

[0100] (1) Dissolve 5 mmol ferric sulfate, 5 mmol phosphoric acid and 2.5 mmol ascorbic acid in 30 mL of deionized water, mix well to obtain the first solution;

[0101] (2) Dissolve 15 mmol of lithium acetate in 20 mL of deionized water, mix well to obtain a second solution, add the second solution dropwise to the first solution at a uniform rate, stir for 20 min to mix well to obtain a mixed solution;

[0102] (3) The prepared mixed solution was ultra-fine ground until the particle D50 of slurry 1 was 80-100 nm, reacted at 220℃ for 12 h, filtered and washed, and vacuum dried at 60℃ for 3 h to obtain the precursor.

[0103] (4) Grind and mix 5g of the obtained precursor with 20mg of glucose, 10mg of conductive carbon black and 15mg of graphene oxide evenly, refine the slurry particles until the D50 is 40-50nm, sinter in sections under N2 protection, keep at 200℃ for 3h and then heat to 700℃ for 5h to obtain the lithium-ion energy storage battery.

[0104] Compared with Example 1, this comparative example does not use manganese source, and the insufficient part is made up with iron source component.

[0105] Comparative Example 4

[0106] A method for preparing a lithium-ion energy storage battery includes the following steps:

[0107] (1) Dissolve 4.8 mmol ferric sulfate, 0.2 mmol manganese dioxide, 5 mmol phosphoric acid and 2.5 mmol ascorbic acid in 30 mL of deionized water, mix well to obtain the first solution;

[0108] (2) Dissolve 15 mmol of lithium acetate in 20 mL of deionized water, mix well to obtain a second solution, add the second solution dropwise to the first solution at a uniform rate, stir for 20 min to mix well to obtain a mixed solution;

[0109] (3) The prepared mixed solution was reacted at a constant temperature of 220℃ for 12h, filtered and washed, and dried under vacuum at 60℃ for 3h to obtain the precursor.

[0110] (4) Grind and mix 5g of the obtained precursor with 20mg of glucose, 10mg of conductive carbon black and 15mg of graphene oxide evenly, refine the slurry particles until the D50 is 40-50nm, sinter in sections under N2 protection, keep at 200℃ for 3h and then heat to 700℃ for 5h to obtain the lithium-ion energy storage battery.

[0111] Compared with Example 1, this comparative example does not undergo ultrafine grinding.

[0112] Comparative Example 5

[0113] A method for preparing a lithium-ion energy storage battery includes the following steps:

[0114] (1) Dissolve 4.8 mmol ferric sulfate, 0.2 mmol manganese dioxide, 5 mmol phosphoric acid and 2.5 mmol ascorbic acid in 30 mL of deionized water, mix well to obtain the first solution;

[0115] (2) Dissolve 15 mmol of lithium acetate in 20 mL of deionized water, mix well to obtain a second solution, add the second solution dropwise to the first solution at a uniform rate, stir for 20 min to mix well to obtain a mixed solution;

[0116] (3) The prepared mixed solution was ultra-fine ground until the particle D50 of slurry 1 was 80-100 nm, reacted at 220℃ for 12 h, filtered and washed, and vacuum dried at 60℃ for 3 h to obtain the precursor.

[0117] (4) Grind and mix 5g of the obtained precursor with 20mg of glucose, 10mg of conductive carbon black and 15mg of graphene oxide evenly, and sinter in sections under the protection of N2. After holding at 200℃ for 3h, the temperature is raised to 700℃ and sintered for 5h to obtain the lithium-ion energy storage battery.

[0118] Compared with Example 1, this comparative example is not refined.

[0119] Comparative Example 6

[0120] A method for preparing a lithium-ion energy storage battery includes the following steps:

[0121] (1) Dissolve 4.8 mmol ferric sulfate, 0.2 mmol manganese dioxide, 5 mmol phosphoric acid and 2.5 mmol ascorbic acid in 30 mL of deionized water, mix well to obtain the first solution;

[0122] (2) Dissolve 15 mmol of lithium acetate in 20 mL of deionized water, mix well to obtain a second solution, add the second solution dropwise to the first solution at a uniform rate, stir for 20 min to mix well to obtain a mixed solution;

[0123] (3) The prepared mixed solution was reacted at a constant temperature of 220℃ for 12h, filtered and washed, and dried under vacuum at 60℃ for 3h to obtain the precursor.

[0124] (4) Grind and mix 5g of the obtained precursor with 20mg of glucose, 10mg of conductive carbon black and 15mg of graphene oxide evenly, and sinter in sections under the protection of N2. After holding at 200℃ for 3h, the temperature is raised to 700℃ and sintered for 5h to obtain the lithium-ion energy storage battery.

[0125] Compared with Example 1, this comparative example does not undergo ultrafine grinding or refining treatment.

[0126] The above samples were subjected to performance testing. The specific testing process included: using the materials prepared in each embodiment and comparative example as the positive electrode and graphite as the negative electrode, adding propylene carbonate, ethylene sulfate and lithium difluorophosphate to the low-temperature electrolyte, and testing the electrochemical performance of the battery.

[0127] like Figure 1a and Figure 1b As shown, in Example 1 of this invention, the first-cycle discharge specific capacity at -20℃ and 0.5C was 163.1 mAh / g, with a first-cycle coulombic efficiency of 96.38%. After 48 cycles, the discharge specific capacity was 166.6 mAh / g, with a capacity retention rate of 102%. Due to incomplete activation, the capacity showed a slight increase in the first five charge-discharge cycles, ultimately resulting in a capacity retention rate greater than 1. At 1C, the first-cycle discharge specific capacity was 147.8 mAh / g. Before 100 cycles, the discharge specific capacity gradually increased and then plateaued, with a first-cycle coulombic efficiency of 88.9%. As the number of cycles increased, the coulombic efficiency remained at 99%. At the 120th cycle, the discharge specific capacity was 163.6 mAh / g, and at the 320th cycle, it reached 163.3 mAh / g, with a retention rate of 110%. This may be due to the increasing activation level of the battery in the first 100 cycles, which led to a corresponding increase in discharge specific capacity.

[0128] The low-temperature cycling performance of Example 1 and Comparative Example 1 was tested at -40°C and 0.5°C. Figure 2a and Figure 2b As shown, in Example 1, the initial discharge specific capacity and coulombic efficiency were 79.23 mAh / g and 102.02%, respectively. After 50 cycles, the capacity and coulombic efficiency were 71.82 mAh / g and 100.05%, respectively, with a capacity retention of 90.66%. In contrast, in Comparative Example 1, the initial discharge specific capacity and coulombic efficiency were 55.60 mAh / g and 154.87%, respectively. After 50 cycles, the capacity and coulombic efficiency were 42.44 mAh / g and 100.02%, respectively, with a capacity retention of 76.33%. After 100 cycles, the capacity and coulombic efficiency were 38.68 mAh / g and 99.98%, respectively, with a capacity retention of 69.57%.

[0129] Meanwhile, the charge-discharge performance of Example 1 and Comparative Example 1 was tested at -40℃ and 0.5C. Figure 3a and Figure 3b As shown, the first-cycle capacity of Example 1 is 79.23 mAh / g, the voltage plateau during charging is above 3.5V, and the voltage plateau during discharging is above 3.3V; while the first-cycle capacity of Comparative Example 1 is 55.60 mAh / g, its charging voltage plateau is higher and its discharging voltage plateau is lower, the difference between the charging and discharging voltage plateaus is increased, the polarization of the battery is greater, the energy loss is higher, and therefore the capacity is reduced to a certain extent.

[0130] The low-temperature cycling performance of each embodiment and comparative example is shown in Table 1:

[0131] Table 1 Low-temperature cycling performance of Examples 1-3 and Comparative Examples 1-6

[0132]

[0133] As shown in Table 1, Examples 1-3 of the present invention exhibit more stable low-temperature cycling performance and discharge specific capacity, demonstrating excellent low-temperature electrochemical performance at -20℃ and -40℃. Comparative Example 1, which only underwent carbon coating, showed relatively stable low-temperature cycling performance, but its discharge specific capacity was low and could not be compared with the other examples. Comparative Example 2, without carbon coating, had low discharge specific capacity and poor cycling performance at -20℃, and its electrochemical performance rapidly declined at -40℃, making testing impossible. Comparative Example 3, without ion doping, had a low discharge specific capacity. Comparative Example 4, without ultrafine grinding, showed a rapid performance decline after 100 cycles. Comparative Example 5, without refining treatment, had poor cycle stability. Comparative Example 6, without both ultrafine grinding and refining treatment, showed significantly lower low-temperature cycling performance compared to the other examples.

[0134] The present invention aims to protect a method for preparing a low-temperature resistant lithium-ion energy storage battery and the battery obtained therefrom, which has the following effects:

[0135] 1. Carbon-coated manganese-doped lithium iron phosphate batteries were prepared by hydrothermal method. Carbon coating prevented the oxidation of Fe in lithium iron phosphate materials, improved the electrical contact between materials, and increased the electronic conductivity of the materials, effectively improving the low-temperature electrochemical performance of lithium-ion energy storage batteries.

[0136] 2. The doping of manganese ions replaces the Fe sites in lithium iron phosphate in a non-equivalent manner, thereby improving the rate performance of the material, reducing resistance, and increasing the conductivity and charge / discharge specific capacity of the material.

[0137] 3. Through ultrafine grinding, the contact area between materials can be effectively increased, allowing magnesium ions to be fully dispersed and doped into lithium iron phosphate, increasing the active sites for reaction, increasing the specific surface area of ​​the material, and improving the cycle reversibility and low-temperature performance of the material. Subsequently, the refining process can fully coat the carbon layer on the particle surface, hindering further particle growth, reducing the contact area between particles, reducing the possibility of particle agglomeration, and obtaining a lithium-ion energy storage battery with excellent charge-discharge specific capacity, good cycle performance, and excellent low-temperature electrochemical performance.

[0138] It should be understood that the specific embodiments described above are merely illustrative or explanatory of the principles of the invention and do not constitute a limitation thereof. Therefore, any modifications, equivalent substitutions, improvements, etc., made without departing from the spirit and scope of the invention should be included within the protection scope of the invention. Furthermore, the appended claims are intended to cover all variations and modifications falling within the scope and boundaries of the appended claims, or equivalent forms of such scope and boundaries.

Claims

1. A method for preparing a low-temperature resistant lithium-ion energy storage battery, characterized in that, include: S100: Iron source, manganese source, phosphorus source and ascorbic acid are dissolved in deionized water and mixed evenly to obtain the first solution; S200, dissolve the lithium source in deionized water, mix well to obtain the second solution; S300, the second solution is added dropwise to the first solution at a uniform rate and stirred until uniform to obtain a mixed solution. The mixed solution is then subjected to ultrafine grinding to obtain a first slurry. The median diameter (D50) of the particles in the first slurry obtained after ultrafine grinding is 80nm to 100nm. S400, the first slurry is subjected to a constant temperature reaction at 200℃~220℃, then filtered, washed, and vacuum dried to obtain the precursor; S500: The precursor, carbon source, conductive carbon black, and graphene oxide are ground and mixed evenly, and then refined to obtain a second slurry. The median diameter (D50) of the particles in the second slurry after refinement is 40nm to 50nm. The second slurry is sintered in segments in an N2 environment. The segmented sintering conditions are: holding at 200°C for 3 hours, then raising the temperature to 700°C and sintering for 5 to 7 hours to obtain a low-temperature resistant lithium-ion energy storage battery.

2. The method for preparing a low-temperature resistant lithium-ion energy storage battery according to claim 1, characterized in that, The iron source includes at least one of iron oxide, ferric sulfate, ferric phosphate, ferrous oxalate, and ferric nitrate. The manganese source includes at least one of manganese dioxide, manganese tetroxide, and manganese acetate. The phosphorus source includes at least one of phosphoric acid, ammonium monohydrogen phosphate, and ammonium dihydrogen phosphate. The lithium source includes at least one of lithium hydroxide, lithium acetate, lithium carbonate, lithium nitrate, and lithium fluoride.

3. The method for preparing a low-temperature resistant lithium-ion energy storage battery according to claim 1, characterized in that, In the first solution, the molar ratio of iron to ascorbic acid is Fe:C6H8O6=1:(0.4~0.6).

4. The method for preparing a low-temperature resistant lithium-ion energy storage battery according to claim 1, characterized in that, In the mixed solution, the molar ratio of lithium, iron, manganese and phosphorus is Li:Fe:Mn:P = 3:0.96:0.04:

1.

5. The method for preparing a low-temperature resistant lithium-ion energy storage battery according to claim 1, characterized in that, In S300, the second solution and the first solution are stirred for 10 min to 30 min.

6. The method for preparing a low-temperature resistant lithium-ion energy storage battery according to claim 1, characterized in that, In S400, the first slurry is reacted at a constant temperature for 12 hours. The vacuum drying temperature is 60℃~80℃, and the time is 2 h~3 h.

7. The method for preparing a low-temperature resistant lithium-ion energy storage battery according to claim 1, characterized in that, The carbon source includes at least one of glucose, fructose, white sugar, citric acid, sucrose, and activated carbon.

8. The method for preparing a low-temperature resistant lithium-ion energy storage battery according to claim 1, characterized in that, In the second slurry, the mass ratio of precursor, carbon source, conductive carbon black and graphene oxide is precursor: carbon source: conductive carbon black: graphene oxide = 1:(0.04~0.06):0.02:0.

03.

9. A low-temperature resistant lithium-ion energy storage battery, characterized in that, The lithium-ion energy storage battery is prepared by the method described in any one of claims 1-8.

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