Porous carbon supported metal oxide modified lithium iron phosphate cathode material and preparation method thereof

Abstract

This invention relates to the field of lithium iron phosphate, specifically to a porous carbon-supported metal oxide-modified lithium iron phosphate cathode material and its preparation method; it addresses the problems of poor electronic conductivity and poor cycle performance of existing lithium iron phosphate. The porous carbon-supported metal oxide-modified lithium iron phosphate cathode material comprises B / F / N-doped porous carbon-supported yttrium oxide-modified lithium iron phosphate, conductive carbon black, sodium carboxymethyl cellulose, and N-methylpyrrolidone. The preparation method first prepares lithium iron phosphate, using 4-formylphenylboronic acid and 2,3,5,6-tetrafluoro-1,4-phenylenediamine to prepare a precursor, which is then combined with copper bromide to prepare B / F / N-doped porous carbon. Yttrium oxide is then loaded onto the porous carbon and modified onto the surface of the lithium iron phosphate. This provides better ion transport channels during charge and discharge, enhancing the kinetic performance and stability of lithium iron phosphate during charge and discharge, ultimately improving the overall performance of the battery.

Description

Technical Field

[0001] This invention relates to the field of lithium iron phosphate, specifically to porous carbon-supported metal oxide-modified lithium iron phosphate cathode materials and their preparation methods. Background Technology

[0002] Lithium iron phosphate (LFP) has attracted widespread attention in the lithium-ion battery field as a cathode material due to its excellent thermal stability, high cycle life, and good safety. However, LFP materials also have some limitations, such as poor cycle performance and low conductivity, which restricts their application in electric vehicles and energy storage systems. Summary of the Invention

[0003] In order to overcome the above-mentioned technical problems, the present invention aims to provide: a porous carbon-supported metal oxide modified lithium iron phosphate cathode material and its preparation method, which solves the problems of poor electronic conductivity and poor cycle performance of existing lithium iron phosphate.

[0004] The objective of this invention can be achieved through the following technical solutions:

[0005] In a first aspect, this application provides a porous carbon-supported metal oxide-modified lithium iron phosphate cathode material, comprising the following components in parts by weight:

[0006] 40-56 parts of B / F / N doped porous carbon-supported yttrium oxide-modified lithium iron phosphate, 5-7 parts of conductive carbon black, and 5-7 parts of sodium carboxymethyl cellulose;

[0007] The B / F / N doped porous carbon-supported yttrium oxide-modified lithium iron phosphate is prepared by the following steps:

[0008] Step A1: Add iron phosphate, lithium carbonate and glucose to a mortar and mix for 10 min. Transfer to a ball mill jar with a raw material to grinding ball mass ratio of 1:6. Ball mill at 800 r / min for 4 h. After drying, place in a sintering furnace, introduce nitrogen gas, calcine at 750℃ for 5 h, and cool to 24-26℃ to obtain lithium iron phosphate.

[0009] Step A2: Add 4-formylphenylboronic acid, 2,3,5,6-tetrafluoro-1,4-phenylenediamine, N,N-dimethylformamide, and mesitylene to a reaction vessel, sonicate for 10 min, add acetic acid and sonicate for 5 min, heat at 130-140℃ for 4-5 h, cool to 24-26℃, filter, extract with dichloromethane using Soxhlet extraction, place in a drying oven and vacuum dry at 45℃ for 2-3 h to obtain the intermediate product;

[0010]

[0011] Step A3: Add the intermediate product and anhydrous copper bromide to a mortar and mix. Under a nitrogen atmosphere, heat to 700-900℃ at 3℃ / min, hold for 2h, cool to 24-26℃, add sulfuric acid, hydrogen peroxide and deionized water to a single-necked flask, stir at 100-200r / min for 12h, wash with distilled water 5-7 times, filter, and place in a drying oven to vacuum dry at 120℃ for 8-10h to obtain B / F / N doped porous carbon.

[0012] Step A4: Add B / F / N doped porous carbon and N,N-dimethylformamide to a three-necked flask equipped with a thermometer and a stirrer, sonicate for 10 min, add yttrium nitrate, sonicate for 10 min, add sodium hydroxide solution to adjust the pH to 8-9, stir at 90℃ for 4 h, cool to 24-26℃, centrifuge, wash 3 times with ethanol, place in a drying oven and vacuum dry at 80℃ for 4-6 h, place in a muffle furnace and calcine at 500℃ for 3 h at a rate of 2℃ / min to obtain B / F / N doped porous carbon supported yttrium oxide;

[0013] Step A5: Add lithium iron phosphate and deionized water to a ball mill jar and ball mill at 400-500 r / min for 15-20 min. Add B / F / N doped porous carbon-supported yttrium oxide and mix at 400-500 r / min for 4-5 h. Transfer to an oven and dry at 80 °C to obtain B / F / N doped porous carbon-supported yttrium oxide modified lithium iron phosphate.

[0014] As a further aspect of the present invention: the ratio of iron phosphate, lithium carbonate and glucose used in step A1 is 196-392 mmol: 100-200 mmol: 7-14 mmol.

[0015] As a further aspect of the present invention: the ratio of 4-formylphenylboronic acid, 2,3,5,6-tetrafluoro-1,4-phenylenediamine, N,N-dimethylformamide, mesitylene and acetic acid in step A2 is 67.6-135.2 mmol: 33.8-67.6 mmol: 150-300 mL: 150-300 mL: 6.76-13.52 mmol.

[0016] As a further aspect of the present invention: the ratio of the intermediate product, anhydrous copper bromide, sulfuric acid, hydrogen peroxide and deionized water in step A3 is 0.5-1g: 5-10g: 8-16mL: 8-16mL: 285-570mL.

[0017] As a further aspect of the present invention: the mass fraction of sulfuric acid in step A3 is 98%.

[0018] As a further aspect of the present invention: the mass fraction of hydrogen peroxide in step A3 is 30%.

[0019] As a further aspect of the present invention: the ratio of B / F / N doped porous carbon, N,N-dimethylformamide and yttrium nitrate used in step A4 is 0.1-0.2g: 500-1000mL: 4-8mmol.

[0020] As a further aspect of the present invention: the molar concentration of the sodium hydroxide solution in step A4 is 1 mol / L.

[0021] As a further aspect of the present invention: the ratio of lithium iron phosphate, deionized water and B / F / N doped porous carbon supported yttrium oxide in step A5 is 0.5-1g: 5-10mL: 0.1-0.2g.

[0022] Secondly, this invention provides a method for preparing a porous carbon-supported metal oxide-modified lithium iron phosphate cathode material, comprising the following steps:

[0023] Step 1: Weigh out 40-56 parts of B / F / N doped porous carbon-supported yttrium oxide-modified lithium iron phosphate, 5-7 parts of conductive carbon black, and 5-7 parts of sodium carboxymethyl cellulose according to the weight ratio, and set aside.

[0024] Step 2: B / F / N doped porous carbon-supported yttrium oxide-modified lithium iron phosphate, conductive carbon black, and sodium carboxymethyl cellulose are ground. Then, N-methylpyrrolidone is added to adjust the solid content to 45-55% and grinding is continued. After grinding, the mixture is coated on an aluminum foil current collector and placed in a constant temperature vacuum drying oven to dry for 8-12 hours. It is then compacted in a roller press and finally punched into a circular electrode using a slicing machine to obtain a porous carbon-supported metal oxide-modified lithium iron phosphate cathode material.

[0025] The beneficial effects of this invention are:

[0026] The porous carbon-supported metal oxide-modified lithium iron phosphate cathode material of the present invention is doped with B, F and N during the synthesis of porous carbon and loaded with yttrium oxide, which is then modified on the surface of lithium iron phosphate to enhance the electron and lithium ion transport efficiency and improve the cycle stability of the electrode material.

[0027] To prepare porous carbon-supported metal oxide-modified lithium iron phosphate cathode materials, lithium iron phosphate was first synthesized from iron phosphate and lithium carbonate. An intermediate product was synthesized using 4-formylphenylboronic acid and 2,3,5,6-tetrafluoro-1,4-phenylenediamine. This intermediate product was then used as an activator to prepare B / F / N-doped porous carbon with a layered porous structure. The porous carbon possesses abundant pores, effectively improving the specific surface area and electrochemical performance of the material, enhancing lithium-ion diffusion and transport efficiency. Fluorine doping introduces semi-ionic CF bonds, increasing carbon layer defects, generating more adsorption active sites, and improving electron transport efficiency. Boron exhibits low electronegativity. With electron-withdrawing capabilities, it can promote the increase of carrier concentration and charge density on the surface of carbon materials, thereby improving the conductivity of carbon materials. Nitrogen doping mainly exists in the form of pyridine nitrogen and pyrrole nitrogen, increasing the electrochemical active sites on the material surface. Yttrium oxide is loaded into B / F / N doped porous carbon using a solvothermal method and heat treatment. Yttrium oxide can fill the lattice defects of lithium iron phosphate and suppress lattice deformation during charging and discharging. During charging and discharging, B / F / N doped porous carbon and yttrium oxide jointly promote the rapid transport of electrons and lithium ions, thereby significantly improving the overall cycle performance and conductivity of the electrode material, thus improving the performance and life of the battery. Detailed Implementation

[0028] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0029] Example 1:

[0030] This embodiment describes a method for preparing a porous carbon-supported metal oxide-modified lithium iron phosphate cathode material, including the following steps:

[0031] Step A1: Add 196 mmol of iron phosphate, 100 mmol of lithium carbonate and 7 mmol of glucose to a mortar and mix for 10 min. Transfer to a ball mill jar with a raw material to grinding ball mass ratio of 1:6. Ball mill at 800 r / min for 4 h. After drying, place in a sintering furnace, introduce nitrogen gas, calcine at 750 °C for 5 h, and cool to 24 °C to obtain lithium iron phosphate.

[0032] Step A2: 67.6 mmol of 4-formylphenylboronic acid, 33.8 mmol of 2,3,5,6-tetrafluoro-1,4-phenylenediamine, 150 mL of N,N-dimethylformamide, and 150 mL of mesitylene were added to a reaction vessel and sonicated for 10 min. Then, 6.76 mmol of acetic acid was added and sonicated for 5 min. The mixture was heated at 130 °C for 4 h, cooled to 24 °C, filtered, and extracted with dichloromethane using a Soxhlet extract. The mixture was then placed in a drying oven and vacuum dried at 45 °C for 2 h to obtain the intermediate product.

[0033] Step A3: Add 0.5g of intermediate product and 5g of anhydrous copper bromide to a mortar and mix. Heat to 700℃ at 3℃ / min under a nitrogen atmosphere, keep warm for 2h, cool to 24℃, add 8mL of sulfuric acid, 8mL of hydrogen peroxide and 285mL of deionized water to a single-necked flask, stir at 100r / min for 12h, wash 5 times with distilled water, filter and place in a drying oven to vacuum dry at 120℃ for 8h to obtain B / F / N doped porous carbon;

[0034] Step A4: Add 0.1g of B / F / N-doped porous carbon and 500mL of N,N-dimethylformamide to a three-necked flask equipped with a thermometer and a stirrer. Sonicate for 10min, add 4mmol of yttrium nitrate, sonicate for 10min, adjust the pH to 8 by adding sodium hydroxide solution dropwise, stir at 90℃ for 4h, cool to 24℃, centrifuge, wash 3 times with ethanol, place in a drying oven and vacuum dry at 80℃ for 4h, place in a muffle furnace and calcine at 500℃ for 3h by increasing the temperature at 2℃ / min to obtain B / F / N-doped porous carbon supported yttrium oxide;

[0035] Step A5: Add 0.5g of lithium iron phosphate and 5mL of deionized water to a ball mill jar, and ball mill at 400r / min for 15min. Add 0.1g of B / F / N doped porous carbon-supported yttrium oxide, mix at 400r / min for 4h, and transfer to an oven to dry at 80℃ to obtain B / F / N doped porous carbon-supported yttrium oxide modified lithium iron phosphate.

[0036] Step A6: Weigh out 40 parts by weight of B / F / N doped porous carbon-supported yttrium oxide-modified lithium iron phosphate, 5 parts by weight of conductive carbon black and 5 parts by weight of sodium carboxymethyl cellulose, and set aside.

[0037] Step A7: B / F / N doped porous carbon-supported yttrium oxide-modified lithium iron phosphate, conductive carbon black, and sodium carboxymethyl cellulose are ground. Then, N-methylpyrrolidone is added to adjust the solid content to 45% and grinding is continued. After grinding, the mixture is coated on an aluminum foil current collector and placed in a constant temperature vacuum drying oven to dry for 8 hours. It is then placed in a roller press to compact it and finally punched into a circular electrode using a slicing machine to obtain a porous carbon-supported metal oxide-modified lithium iron phosphate cathode material.

[0038] Example 2:

[0039] This embodiment describes a method for preparing a porous carbon-supported metal oxide-modified lithium iron phosphate cathode material, including the following steps:

[0040] Step A1: Add 294 mmol of iron phosphate, 150 mmol of lithium carbonate and 10.5 mmol of glucose to a mortar and mix for 10 min. Transfer to a ball mill jar with a raw material to grinding ball mass ratio of 1:6. Ball mill at 800 r / min for 4 h. After drying, place in a sintering furnace, introduce nitrogen gas, calcine at 750 °C for 5 h, and cool to 25 °C to obtain lithium iron phosphate.

[0041] Step A2: 101.4 mmol of 4-formylphenylboronic acid, 50.7 mmol of 2,3,5,6-tetrafluoro-1,4-phenylenediamine, 225 mL of N,N-dimethylformamide, and 225 mL of mesitylene were added to a reaction vessel and sonicated for 10 min. Then, 10.14 mmol of acetic acid was added and sonicated for 5 min. The mixture was heated at 135 °C for 4.5 h, cooled to 25 °C, filtered, and extracted with dichloromethane using a Soxhlet extract. The mixture was then placed in a drying oven and vacuum dried at 45 °C for 2.5 h to obtain the intermediate product.

[0042] Step A3: Add 0.75g of intermediate product and 7.5g of anhydrous copper bromide to a mortar and mix. Heat to 800℃ at 3℃ / min under a nitrogen atmosphere, hold for 2h, cool to 25℃, add 12mL of sulfuric acid, 12mL of hydrogen peroxide and 428mL of deionized water to a single-necked flask, stir at 150r / min for 12h, wash 6 times with distilled water, filter, and place in a drying oven to vacuum dry at 120℃ for 9h to obtain B / F / N doped porous carbon.

[0043] Step A4: Add 0.15g of B / F / N-doped porous carbon and 750mL of N,N-dimethylformamide to a three-necked flask equipped with a thermometer and a stirrer. Sonicate for 10min, add 6mmol of yttrium nitrate, sonicate for 10min, adjust the pH to 8 by adding sodium hydroxide solution dropwise, stir at 90℃ for 4h, cool to 25℃, centrifuge, wash 3 times with ethanol, place in a drying oven and vacuum dry at 80℃ for 5h, place in a muffle furnace and calcine at 500℃ for 3h by increasing the temperature at 2℃ / min to obtain B / F / N-doped porous carbon supported yttrium oxide;

[0044] Step A5: Add 0.75g of lithium iron phosphate and 8mL of deionized water to a ball mill jar, and ball mill at 450r / min for 17min. Add 0.15g of B / F / N doped porous carbon-supported yttrium oxide, mix at 450r / min for 4.5h, transfer to an oven and dry at 80℃ to obtain B / F / N doped porous carbon-supported yttrium oxide modified lithium iron phosphate.

[0045] Step A6: Weigh out 48 parts by weight of B / F / N doped porous carbon-supported yttrium oxide-modified lithium iron phosphate, 6 parts by weight of conductive carbon black, and 6 parts by weight of sodium carboxymethyl cellulose, and set aside.

[0046] Step A7: B / F / N doped porous carbon-supported yttrium oxide-modified lithium iron phosphate, conductive carbon black, and sodium carboxymethyl cellulose are ground. Then, N-methylpyrrolidone is added to adjust the solid content to 50% and grinding is continued. After grinding, the mixture is coated on an aluminum foil current collector and placed in a constant temperature vacuum drying oven to dry for 10 hours. It is then placed in a roller press to compact it and finally punched into a circular electrode using a slicing machine to obtain a porous carbon-supported metal oxide-modified lithium iron phosphate cathode material.

[0047] Example 3:

[0048] This embodiment describes a method for preparing a porous carbon-supported metal oxide-modified lithium iron phosphate cathode material, including the following steps:

[0049] Step A1: Add 392 mmol of iron phosphate, 200 mmol of lithium carbonate and 14 mmol of glucose to a mortar and mix for 10 min. Transfer to a ball mill jar with a raw material to grinding ball mass ratio of 1:6. Ball mill at 800 r / min for 4 h. After drying, place in a sintering furnace, introduce nitrogen gas, calcine at 750 °C for 5 h, and cool to 26 °C to obtain lithium iron phosphate.

[0050] Step A2: 135.2 mmol of 4-formylphenylboronic acid, 67.6 mmol of 2,3,5,6-tetrafluoro-1,4-phenylenediamine, 300 mL of N,N-dimethylformamide, and 300 mL of mesitylene were added to a reaction vessel and sonicated for 10 min. Then, 13.52 mmol of acetic acid was added and sonicated for 5 min. The mixture was heated at 140 °C for 5 h, cooled to 26 °C, filtered, and extracted with dichloromethane using a Soxhlet extract. The mixture was then placed in a drying oven and vacuum dried at 45 °C for 3 h to obtain the intermediate product.

[0051] Step A3: Add 1g of intermediate product and 10g of anhydrous copper bromide to a mortar and mix. Under a nitrogen atmosphere, heat to 900℃ at 3℃ / min and hold for 2h. Cool to 26℃ and add to a single-necked flask with 16mL of sulfuric acid, 16mL of hydrogen peroxide and 570mL of deionized water. Stir at 200r / min for 12h. Wash 7 times with distilled water, filter and place in a drying oven to vacuum dry at 120℃ for 10h to obtain B / F / N doped porous carbon.

[0052] Step A4: Add 0.2g of B / F / N-doped porous carbon and 1000mL of N,N-dimethylformamide to a three-necked flask equipped with a thermometer and a stirrer. Sonicate for 10min, add 8mmol of yttrium nitrate, sonicate for 10min, adjust the pH to 9 by adding sodium hydroxide solution dropwise, stir at 90℃ for 4h, cool to 26℃, centrifuge, wash 3 times with ethanol, place in a drying oven and vacuum dry at 80℃ for 6h, place in a muffle furnace and calcine at 500℃ for 3h by increasing the temperature at 2℃ / min to obtain B / F / N-doped porous carbon supported yttrium oxide;

[0053] Step A5: Add 1g of lithium iron phosphate and 10mL of deionized water to a ball mill jar, and ball mill at 500r / min for 20min. Add 0.2g of B / F / N doped porous carbon-supported yttrium oxide, mix at 500r / min for 5h, and transfer to an oven to dry at 80℃ to obtain B / F / N doped porous carbon-supported yttrium oxide modified lithium iron phosphate.

[0054] Step A6: Weigh out 56 parts by weight of B / F / N doped porous carbon-supported yttrium oxide-modified lithium iron phosphate, 7 parts by weight of conductive carbon black, and 7 parts by weight of sodium carboxymethyl cellulose, and set aside.

[0055] Step A7: B / F / N doped porous carbon-supported yttrium oxide-modified lithium iron phosphate, conductive carbon black, and sodium carboxymethyl cellulose are ground. Then, N-methylpyrrolidone is added to adjust the solid content to 55% and grinding is continued. After grinding, the mixture is coated on an aluminum foil current collector and placed in a constant temperature vacuum drying oven to dry for 12 hours. It is then placed in a roller press to compact it and finally punched into a circular electrode using a slicing machine to obtain a porous carbon-supported metal oxide-modified lithium iron phosphate cathode material.

[0056] Comparative Example 1:

[0057] This comparative example illustrates a method for preparing a porous carbon-supported metal oxide-modified lithium iron phosphate cathode material, comprising the following steps:

[0058] Step A1: Add 392 mmol of iron phosphate, 200 mmol of lithium carbonate and 14 mmol of glucose to a mortar and mix for 10 min. Transfer to a ball mill jar with a raw material to grinding ball mass ratio of 1:6. Ball mill at 800 r / min for 4 h. After drying, place in a sintering furnace, introduce nitrogen gas, calcine at 750 °C for 5 h, and cool to 26 °C to obtain lithium iron phosphate.

[0059] Step A2: Add 5g glucose, 5g potassium bicarbonate and 20mL deionized water to a single-necked flask, sonicate for 30min, place in an oven and dry at 60℃ for 12h, transfer to a tube furnace, introduce nitrogen gas, heat to 750℃ at 5℃ / min and hold for 2h, wash with 1mol / L hydrochloric acid and distilled water until pH is 7, dry to obtain porous carbon;

[0060] Step A3: Add 0.2g of porous carbon and 1000mL of N,N-dimethylformamide to a three-necked flask equipped with a thermometer and a stirrer, sonicate for 10min, add 8mmol of yttrium nitrate, sonicate for 10min, adjust the pH to 9 by adding sodium hydroxide solution dropwise, stir at 90℃ for 4h, cool to 26℃, centrifuge, wash 3 times with ethanol, place in a drying oven and vacuum dry at 80℃ for 6h, place in a muffle furnace and calcine at 500℃ for 3h by increasing the temperature at 2℃ / min to obtain porous carbon-supported yttrium oxide;

[0061] Step A4: Add 1g of lithium iron phosphate and 10mL of deionized water to a ball mill jar, and ball mill at 500r / min for 20min. Add 0.2g of porous carbon-supported yttrium oxide, mix at 500r / min for 5h, and transfer to an oven to dry at 80℃ to obtain porous carbon-supported yttrium oxide-modified lithium iron phosphate.

[0062] Step A5: Weigh out 56 parts of porous carbon-supported yttrium oxide-modified lithium iron phosphate, 7 parts of conductive carbon black, and 7 parts of sodium carboxymethyl cellulose according to the weight ratio, and set aside;

[0063] Step A6: The porous carbon-supported yttrium oxide-modified lithium iron phosphate, conductive carbon black, and sodium carboxymethyl cellulose are ground. Then, N-methylpyrrolidone is added to adjust the solid content to 55% and grinding is continued. After grinding, the mixture is coated on an aluminum foil current collector and placed in a constant temperature vacuum drying oven to dry for 12 hours. It is then placed in a roller press to compact it and finally punched into a circular electrode using a slicing machine to obtain the porous carbon-supported metal oxide-modified lithium iron phosphate cathode material.

[0064] Comparative Example 2:

[0065] This comparative example illustrates a method for preparing porous carbon-modified lithium iron phosphate cathode material, comprising the following steps:

[0066] Step A1: Add 392 mmol of iron phosphate, 200 mmol of lithium carbonate and 14 mmol of glucose to a mortar and mix for 10 min. Transfer to a ball mill jar with a raw material to grinding ball mass ratio of 1:6. Ball mill at 800 r / min for 4 h. After drying, place in a sintering furnace, introduce nitrogen gas, calcine at 750 °C for 5 h, and cool to 26 °C to obtain lithium iron phosphate.

[0067] Step A2: 135.2 mmol of 4-formylphenylboronic acid, 67.6 mmol of 2,3,5,6-tetrafluoro-1,4-phenylenediamine, 300 mL of N,N-dimethylformamide, and 300 mL of mesitylene were added to a reaction vessel and sonicated for 10 min. Then, 13.52 mmol of acetic acid was added and sonicated for 5 min. The mixture was heated at 140 °C for 5 h, cooled to 26 °C, filtered, and extracted with dichloromethane using a Soxhlet extract. The mixture was then placed in a drying oven and vacuum dried at 45 °C for 3 h to obtain the intermediate product.

[0068] Step A3: Add 1g of intermediate product and 10g of anhydrous copper bromide to a mortar and mix. Under a nitrogen atmosphere, heat to 900℃ at 3℃ / min and hold for 2h. Cool to 26℃ and add to a single-necked flask with 16mL of sulfuric acid, 16mL of hydrogen peroxide and 570mL of deionized water. Stir at 200r / min for 12h. Wash 7 times with distilled water, filter and place in a drying oven to vacuum dry at 120℃ for 10h to obtain B / F / N doped porous carbon.

[0069] Step A4: Add 1g of lithium iron phosphate and 10mL of deionized water to a ball mill jar, and ball mill at 500r / min for 20min. Add 0.2g of B / F / N doped porous carbon, mix at 500r / min for 5h, and transfer to an oven to dry at 80℃ to obtain B / F / N doped porous carbon modified lithium iron phosphate.

[0070] Step A5: Weigh out 56 parts of B / F / N doped porous carbon modified lithium iron phosphate, 7 parts of conductive carbon black, and 7 parts of sodium carboxymethyl cellulose according to the weight ratio, and set aside.

[0071] Step A6: B / F / N doped porous carbon modified lithium iron phosphate, conductive carbon black and sodium carboxymethyl cellulose are ground, then N-methylpyrrolidone is added to adjust the solid content to 55% and grinding is continued. After grinding, it is coated on aluminum foil current collector and placed in a constant temperature vacuum drying oven to dry for 12 hours. It is then placed in a roller press to compact, and finally punched into a circular electrode by a slicing machine to obtain porous carbon modified lithium iron phosphate cathode material.

[0072] Comparative Example 3:

[0073] This comparative example illustrates a method for preparing porous carbon-modified lithium iron phosphate cathode material, comprising the following steps:

[0074] Step A1: Add 392 mmol of iron phosphate, 200 mmol of lithium carbonate and 14 mmol of glucose to a mortar and mix for 10 min. Transfer to a ball mill jar with a raw material to grinding ball mass ratio of 1:6. Ball mill at 800 r / min for 4 h. After drying, place in a sintering furnace, introduce nitrogen gas, calcine at 750 °C for 5 h, and cool to 26 °C to obtain lithium iron phosphate.

[0075] Step A2: Add 5g glucose, 5g potassium bicarbonate and 20mL deionized water to a single-necked flask, sonicate for 30min, place in an oven and dry at 60℃ for 12h, transfer to a tube furnace, introduce nitrogen gas, heat to 750℃ at 5℃ / min and hold for 2h, wash with 1mol / L hydrochloric acid and distilled water until pH is 7, dry to obtain porous carbon;

[0076] Step A3: Add 1g of lithium iron phosphate and 10mL of deionized water to a ball mill jar, ball mill at 500r / min for 20min, add 0.2g of porous carbon, mix at 500r / min for 5h, transfer to an oven and dry at 80℃ to obtain porous carbon modified lithium iron phosphate;

[0077] Step A4: Weigh out 56 parts of porous carbon-modified lithium iron phosphate, 7 parts of conductive carbon black, and 7 parts of sodium carboxymethyl cellulose according to the weight ratio, and set aside.

[0078] Step A5: The porous carbon-modified lithium iron phosphate, conductive carbon black and sodium carboxymethyl cellulose are ground, and then N-methylpyrrolidone is added to adjust the solid content to 55% and the grinding continues. After grinding, the mixture is coated on an aluminum foil current collector and placed in a constant temperature vacuum drying oven to dry for 12 hours. It is then placed in a roller press to compact it and finally punched into a circular electrode using a slicing machine to obtain the porous carbon-modified lithium iron phosphate cathode material.

[0079] Performance testing

[0080] The lithium iron phosphate cathode materials of Examples 1-3 and Comparative Examples 1-3 were used as the cathodes, lithium sheets as the anodes, Celgard 2400 as the battery separator, and 1M LiPF6 / EC+DEC+EMC (1:1:1, v / v / v) as the electrolyte. The batteries were assembled using CR2032 button cell casings. After injecting the electrolyte, a 12kN pressure was applied using a packaging machine to seal the batteries, ensuring that the sealing rings were fully pressed together to obtain the lithium batteries. These lithium batteries were used as sample batteries.

[0081] Conduct the conductivity test on the sample battery. Set the multimeter knob to the resistance setting, connect the two probes of the multimeter to the positive and negative terminals of the battery respectively, record the voltage values ​​at the battery terminals, and calculate the battery conductivity.

[0082] The sample batteries were subjected to 0.1C cycle performance testing at 25℃ using a Blue Electric Tester: the prepared sample batteries were placed in a constant temperature chamber at 25℃ for charge and discharge testing, with a voltage range of 2.5-3.75V, and charged and discharged at a current of 0.1C (constant current charging was used) for 100 cycles. The relevant data of 0.1C discharge specific capacity and capacity retention rate after 100 cycles were obtained.

[0083] Table 1 Comparison of Sample Conductivity, Discharge Specific Capacity, and Turnover Retention Rate

[0084]

[0085] Referring to Table 1, based on the comparison between Examples 1-3 and Comparative Examples 1-3, it can be seen that B / F / N doped porous carbon-supported yttrium oxide modified lithium iron phosphate has high conductivity and good cycle performance.

[0086] Because boron atoms introduce hole carriers, fluorine atoms optimize the interface charge distribution, and nitrogen atoms mainly exist in the form of pyridine nitrogen and pyrrole nitrogen, the three work together to improve electron mobility. The conductivity of Example 3 is significantly improved compared with Comparative Example 1, which proves that the B / F / N doped porous carbon added in Example 3 is significantly better than the porous carbon added in Comparative Example 1. This indicates that the cathode material obtained by loading yttrium oxide onto B / F / N doped porous carbon to modify lithium iron phosphate has high conductivity.

[0087] In Example 3, yttrium oxide was doped. Yttrium oxide, as an electron bridging medium, optimized the interfacial charge transport path between B / F / N doped carbon and lithium iron phosphate. The conductivity of Example 3 was significantly improved compared with Comparative Example 2, indicating that the cathode material obtained by modifying lithium iron phosphate with yttrium oxide supported by B / F / N doped porous carbon has high conductivity.

[0088] In Comparative Example 3, ordinary porous carbon lacks elemental doping and is not loaded with yttrium oxide, so it can only provide limited conductive channels through its physical pore structure. In contrast, in Example 3, the co-doping of B / F / N introduces defect states into the carbon framework through chemical bonding, forming a continuous conductive network that shortens the electron migration path. Yttrium oxide acts as an electron bridging medium, optimizing the interfacial charge transport path and improving conductivity. The conductivity of Example 3 is significantly higher than that of Comparative Example 3, indicating that the cathode material obtained by modifying lithium iron phosphate with yttrium oxide loaded on B / F / N doped porous carbon has higher conductivity.

[0089] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0090] The above description is merely an example and illustration of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described or use similar methods to replace them, as long as they do not deviate from the invention or exceed the scope defined in this application, they should all fall within the protection scope of the present invention.

Claims

1. A porous carbon-supported metal oxide-modified lithium iron phosphate cathode material, characterized in that, Includes the following components by weight: 40-56 parts of B / F / N doped porous carbon-supported yttrium oxide-modified lithium iron phosphate, 5-7 parts of conductive carbon black, and 5-7 parts of sodium carboxymethyl cellulose; The B / F / N doped porous carbon-supported yttrium oxide-modified lithium iron phosphate is prepared by the following steps: Step A1: Mix iron phosphate, lithium carbonate and glucose, ball mill, dry, calcine and cool to obtain lithium iron phosphate; Step A2: 4-Formylphenylboronic acid, 2,3,5,6-tetrafluoro-1,4-phenylenediamine, N,N-dimethylformamide and mesitylene were sonicated, acetic acid was added and sonicated, heated, cooled, filtered, Soxhlet extracted, and dried to obtain the intermediate product; Step A3: Mix the intermediate product and anhydrous copper bromide, heat, keep warm, cool, stir with sulfuric acid, hydrogen peroxide and deionized water, wash, filter and dry to obtain B / F / N doped porous carbon. Step A4: B / F / N doped porous carbon and N,N-dimethylformamide were sonicated, yttrium nitrate was added and sonicated, pH was adjusted with sodium hydroxide solution, stirred, cooled, centrifuged, washed, dried and calcined to obtain B / F / N doped porous carbon supported yttrium oxide; Step A5: Ball mill lithium iron phosphate and deionized water, add B / F / N doped porous carbon-supported yttrium oxide, mix, and dry to obtain B / F / N doped porous carbon-supported yttrium oxide modified lithium iron phosphate.

2. The porous carbon-supported metal oxide-modified lithium iron phosphate cathode material according to claim 1, characterized in that, The ratio of iron phosphate, lithium carbonate and glucose used in step A1 is 196-392 mmol: 100-200 mmol: 7-14 mmol.

3. The porous carbon-supported metal oxide-modified lithium iron phosphate cathode material according to claim 1, characterized in that, The ratio of 4-formylphenylboronic acid, 2,3,5,6-tetrafluoro-1,4-phenylenediamine, N,N-dimethylformamide, mesitylene, and acetic acid used in step A2 is 67.6-135.2 mmol: 33.8-67.6 mmol: 150-300 mL: 150-300 mL: 6.76-13.52 mmol.

4. The porous carbon-supported metal oxide-modified lithium iron phosphate cathode material according to claim 1, characterized in that, The ratio of the intermediate product, anhydrous copper bromide, sulfuric acid, hydrogen peroxide and deionized water used in step A3 is 0.5-1g: 5-10g: 8-16mL: 8-16mL: 285-570mL.

5. The porous carbon-supported metal oxide-modified lithium iron phosphate cathode material according to claim 1, characterized in that, The sulfuric acid in step A3 has a mass fraction of 98%.

6. The porous carbon-supported metal oxide-modified lithium iron phosphate cathode material according to claim 1, characterized in that, The mass fraction of hydrogen peroxide mentioned in step A3 is 30%.

7. The porous carbon-supported metal oxide-modified lithium iron phosphate cathode material according to claim 1, characterized in that, In step A4, the ratio of B / F / N-doped porous carbon, N,N-dimethylformamide, and yttrium nitrate is 0.1-0.2 g: 500-1000 mL: 4-8 mmol; the molar concentration of the sodium hydroxide solution is 1 mol / L.

8. The porous carbon-supported metal oxide-modified lithium iron phosphate cathode material according to claim 1, characterized in that, In step A5, the ratio of lithium iron phosphate, deionized water, and B / F / N doped porous carbon-supported yttrium oxide is 0.5-1g: 5-10mL: 0.1-0.2g.

9. A method for preparing porous carbon-supported metal oxide-modified lithium iron phosphate cathode material, characterized in that, The preparation of the porous carbon-supported metal oxide-modified lithium iron phosphate cathode material as described in any one of claims 1-8 includes the following steps: Step 1: Weigh out 40-56 parts of B / F / N doped porous carbon-supported yttrium oxide-modified lithium iron phosphate, 5-7 parts of conductive carbon black, and 5-7 parts of sodium carboxymethyl cellulose according to the weight ratio, and set aside. Step 2: B / F / N doped porous carbon-supported yttrium oxide-modified lithium iron phosphate, conductive carbon black, and sodium carboxymethyl cellulose are ground. Then, N-methylpyrrolidone is added to adjust the solid content and grinding continues. After grinding, the mixture is coated onto an aluminum foil current collector and placed in a constant temperature vacuum drying oven to dry for 8-12 hours. It is then placed in a roller press to compact it and finally punched into a circular electrode using a slicing machine to obtain a porous carbon-supported metal oxide-modified lithium iron phosphate cathode material.

10. The method for preparing the porous carbon-supported metal oxide-modified lithium iron phosphate cathode material according to claim 9, characterized in that, The solid content is adjusted to 45-55%.

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