Halogenated electrolyte modified low impedance positive electrode and its preparation process and application

Abstract

The application relates to the technical field of lithium ion batteries, in particular to a halide electrolyte modified low-impedance positive electrode and a preparation process and application thereof; the existing lithium ion battery has the problem of high impedance of the positive electrode material; the preparation method uses carbon-coated aluminum foil as the positive electrode current collector, has low contact impedance and high adhesion, reduces the charge transfer resistance and the battery internal resistance, and improves the rate performance and the cycle performance of the battery; the positive electrode active material is added, C6H 12 O6*H2O is used for carbon coating to improve the electronic transmission capacity of lithium iron phosphate, titanium-vanadium co-doping is used for synergistically improving the electronic conductivity and reducing the electronic conduction impedance; halide solid electrolyte coating lithium iron phosphate inhibits the side reaction and reduces the interface impedance; carbon nanotube coating inhibits particle agglomeration and reduces the charge transfer impedance; the modified conductive agent and the modified binder are added, so that the lithium ion battery has higher cycle stability, higher electrochemical activity and lower impedance.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of lithium ion batteries, in particular to a halogenated electrolyte modified low-impedance positive electrode and a preparation process and application thereof. BACKGROUND

[0002] In the field of lithium ion batteries, lithium ion batteries as an important rechargeable power source have been widely used in electronic devices, electric vehicles and energy storage systems, and the design and optimization of positive electrode materials are the focus of research. Lithium iron phosphate as a positive electrode material has been widely concerned due to its high safety, long cycle life and good stability. Secondly, lithium iron phosphate positive electrode material is considered to be one of the most potential lithium ion battery positive electrode materials due to its high theoretical capacity, low cost, good cycle performance and excellent thermal stability.

[0003] However, the performance of lithium ion batteries is limited by the impedance problem of the positive electrode material. The low electronic conductivity of lithium iron phosphate itself limits the overall performance of the battery, especially the high impedance in the pores of the lithium iron phosphate material, which affects the overall efficiency and cycle stability of the battery. In order to solve the above problems, researchers have explored many methods to reduce the impedance of lithium iron phosphate positive electrode material, including improving the structure and electrochemical performance of the material by surface modification and element doping.

[0004] Therefore, it is of great significance to develop a halogenated electrolyte modified low-impedance positive electrode. SUMMARY

[0005] In order to overcome the above technical problems, the purpose of the present application is to provide a halogenated electrolyte modified low-impedance positive electrode and a preparation process and application thereof. The modified lithium iron phosphate, the modified binder and the modified conductive agent are dry-mixed to obtain a mixed powder. N-methyl pyrrolidone is added to the mixed powder for cis-trans kneading, and then high-speed dispersion is carried out to obtain a positive electrode slurry. The positive electrode slurry is coated on both sides of the carbon-coated aluminum foil, dried in an oven, and then cut by a mold to obtain a halogenated electrolyte modified low-impedance positive electrode, which solves the problem of high impedance of the positive electrode material of the lithium ion battery.

[0006] The purpose of the present application can be achieved by the following technical solutions:

[0007] In a first aspect, the application provides a halogenated electrolyte modified low-impedance positive electrode, which comprises the following components by mass:

[0008] Modified lithium iron phosphate 90-95 parts, modified binder 3-5 parts and modified conductive agent 3-5 parts;

[0009] The modified lithium iron phosphate is prepared by the following steps:

[0010] Step a1: Fe(NO3)3·9H2O, NaH2PO4, TiO2and V2O5are mixed and added to a planetary ball mill, anhydrous ethanol is added, the ball-to-material ratio is 10:1, the rotation speed is 300 r / min, and ball milling is performed for 6 h. The ball and material are separated, the material and a surfactant are added to a three-necked flask equipped with a stirrer and a thermometer, mixed and stirred for 1-2 h, urea is added, the three-necked flask is placed in a 95℃ water bath for heating reaction for 2 h, and after the reaction is completed, precipitation aging, filtration, washing and drying are performed to obtain titanium-vanadium-doped iron phosphate;

[0011] Step a2: titanium-vanadium-doped iron phosphate, LiOH·H2O and C6H 12 O6·H2O are mixed and added to a planetary ball mill, anhydrous ethanol is added, the ball-to-material ratio is 5:1, the rotation speed is 600 r / min, and ball milling is performed for 10 h. After the ball and material are separated, the material is dried at 80℃ and ground, and then placed in a tube furnace. The sintering schedule is set as follows: 4 h of heat preservation at 25℃, then heating to 680℃, constant temperature reaction for 10 h, and finally natural cooling to 25℃. After sintering is completed, the product is ground through a 200-mesh sieve to obtain a precursor;

[0012] Step a3: the precursor and deionized water are added to a three-necked flask equipped with a stirrer and a thermometer, mixed and stirred for 30 min, LiCl and InCl3are added, stirred for 30 min, heated to 65℃ under continuous stirring for 2-3 h, placed in a mortar and ground for 15-30 min, and then dehydrated in a vacuum tube furnace by heating from 25℃ to 200℃ at a rate of 2℃ / min for 2 h. After the heat preservation is completed, the material is naturally cooled to 25℃, and then sieved through a 400-mesh sieve to obtain Li3InCl6-coated lithium iron phosphate;

[0013] Step a4: carbon nanotubes are added to a mixed acid and ultrasonically dispersed for 20 min, placed in an oil bath at 120℃ and magnetically stirred at 600 r / min for 3-4 h, then washed with deionized water for 2-3 times to obtain acid-treated carbon nanotubes. Then a dispersant and a solvent are added, mixed and stirred, and ultrasonically dispersed for 30 min each time. Subsequently, Li3InCl6-coated lithium iron phosphate is added, and then ultrasonically dispersed and stirred for 15 min each time. The mixture is washed with anhydrous ethanol for 3-4 times to remove the dispersant not involved in the compounding, free carbon nanotubes and water. The mixture is placed in an oven and dried at 80℃ to obtain modified lithium iron phosphate.

[0014] As a preferred embodiment of the present application, the amount ratio of Fe(NO3)3·9H2O, NaH2PO4, TiO2, V2O5, anhydrous ethanol, a surfactant and urea in step a1 is 0.496-0.992 mol: 2-4 mol: 0.0015-0.003 mol: 0.0012-0.0025 mol: 100-200 mL: 0.012 g: 18.02 g.

[0015] As a preferred embodiment of the present application, the surfactant in step a1 is polyethylene glycol 2000.

[0016] As a preferred embodiment of the present application, the amount ratio of the titanium-vanadium-doped iron phosphate, LiOH·H2O, C6H 12 O6·H2O and anhydrous ethanol in step a2 is 80 g: 42.6 g: 55 g: 400 mL.

[0017] As a preferred embodiment of the present application, the amount ratio of the precursor, deionized water, LiCl and InCl3 in step a3 is 100 g: 300 mL: 7.45 g: 4.29 g.

[0018] As a preferred embodiment of the present application, the amount ratio of the carbon nanotube, mixed acid, dispersant, solvent and Li3InCl6-coated lithium iron phosphate in step a4 is 2-3 g: 150-200 mL: 0.5 g: 400 mL: 98 g.

[0019] As a preferred embodiment of the present application, the outer diameter of the carbon nanotube in step a4 is 1-2 nm, and the length is 5-30 μm.

[0020] As a preferred embodiment of the present application, the mixed acid in step a4 is a mixed acid of mass fraction 98% sulfuric acid and mass fraction 68% nitric acid in a volume ratio of 1:3; the dispersant is polyvinylpyrrolidone LUVITECK 90 Powder; and the solvent is anhydrous ethanol.

[0021] As a preferred embodiment of the present application, the modified binder is prepared by the following steps:

[0022] Step b1: polyacrylic acid, deionized water and LiOH·H2O are added to a three-necked flask equipped with a stirrer and a thermometer, mixed and stirred for 15-30 min, polyethylene oxide is added, electromagnetic stirring is performed for 30 min, and then the mixture is placed in a 60℃ water bath for heating and stirring for 6 h to obtain a modified binder.

[0023] As a preferred embodiment of the present application, the amount ratio of the polyacrylic acid, deionized water, LiOH H2O and polyethylene oxide in step b1 is 25 mL:275 mL:4.66 g:3.4 g.

[0024] As a preferred embodiment of the present application, the polyacrylic acid in step b1 is of model llb75354; and the polyethylene oxide is of model P432440 produced by Aladdin.

[0025] As a preferred embodiment of the present application, the modified conductive agent is prepared by the following steps:

[0026] Step c1: acetylene black, dopamine, tris-hydroxymethyl aminomethane hydrochloride, deionized water and Na2S2O8 are added into a three-necked flask equipped with a stirrer and a thermometer, and mixed and stirred in a 60°C water bath for 24 hours. The obtained solution is suction filtered, the filter cake is washed with deionized water for 2-3 times, and the filter cake is transferred to a vacuum oven and dried at 70°C for 10 hours to obtain a modified conductive agent.

[0027] As a preferred embodiment of the present application, the amount ratio of the acetylene black, dopamine, tris-hydroxymethyl aminomethane hydrochloride, deionized water and Na2S2O8 in step c1 is 5 g:1 g:24 g:200-400 mL:24 g.

[0028] As a preferred embodiment of the present application, the acetylene black in step c1 is of model N754.

[0029] In a second aspect, the present application provides a preparation process of a halogenated electrolyte modified low-impedance positive electrode, comprising the following steps:

[0030] Step one: the modified lithium iron phosphate 90-95 parts, the modified binder 3-5 parts, the modified conductive agent 3-5 parts and N-methyl pyrrolidone 85-90 parts are weighed according to the weight components;

[0031] Step two: the modified lithium iron phosphate, the modified binder and the modified conductive agent are dry-mixed, the dry-mixing conditions are stirring speed of 20 r / min and dispersion speed of 200 r / min, and the time is 30 min to obtain a mixed powder; the N-methyl pyrrolidone is added to the mixed powder for kneading, and the forward and reverse kneading is alternately performed, and then high-speed dispersion is performed, the high-speed dispersion conditions are stirring speed of 30 r / min and dispersion speed of 1500 r / min, and the dispersion time is 2-3 h to obtain a positive electrode slurry;

[0032] Step three: the positive electrode slurry is uniformly coated on both sides of the carbon-coated aluminum foil, and the coating process is controlled to have a surface density of 23 mg / cm 2The coated carbon-coated aluminum foil is dried in an oven, and then the halogenated electrolyte modified low-impedance anode is obtained by cutting with a mold.

[0033] In a third aspect, the application provides the use of the halogenated electrolyte modified low-impedance anode as described in the first aspect in a lithium ion battery.

[0034] The application has the following advantages:

[0035] The halogenated electrolyte modified low-impedance anode and its preparation process and application of the application are as follows: the modified lithium iron phosphate, the modified binder and the modified conductive agent are dry-mixed, N-methyl pyrrolidone is added for cis-trans kneading, and then high-speed dispersion is performed to obtain anode slurry; the anode slurry is coated on both sides of the carbon-coated aluminum foil, leaving the tab area; the coated electrode piece is dried in an oven, and then the halogenated electrolyte modified low-impedance anode is obtained by cutting with a mold; the preparation process uses carbon-coated aluminum foil as the anode current collector, has low contact impedance and high adhesion, reduces the charge transfer resistance and the internal resistance of the battery, weakens the internal polarization of the battery, inhibits the corrosion of the electrolyte to the aluminum foil, improves the diffusion rate of lithium ions in the material, and thus improves the rate performance and cycle performance of the battery; the modified lithium iron phosphate is used as the anode active material, which improves the electronic conductivity, prevents the oxidation of the electrolyte, inhibits the occurrence of interface side reactions, improves the interface stability, enhances the Li + The diffusion rate, so that it has good electrochemical performance, the coating of carbon nanotubes enhances the conductivity of the material, reduces the charge transfer impedance, and by adding the modified conductive agent and the modified binder, the cycle stability is higher, the electrochemical activity is improved, and the impedance is reduced; during the drying process of the electrode piece, the -NH- in the polydopamine reacts with the -COOH in the polyacrylic acid to form an amide bond, and there is crosslinking between them to form a crosslinked network, which improves the bonding performance of the modified binder, and the polydopamine is deposited on the surface of acetylene black, which helps to build a more complete conductive network for the electrode.

[0036] In the process of preparing the halogenated electrolyte modified low-impedance anode, a modified lithium iron phosphate is first prepared: Fe(NO3)3·9H2O, NaH2PO4, TiO2 and V2O5 are mixed and ball milled, a surfactant is added and stirred, urea is added and heated in a water bath, and then precipitation aging, filtration, washing and drying are performed to obtain titanium-vanadium doped iron phosphate; the titanium-vanadium doped iron phosphate, LiOH·H2O and C6H 12 O6·H2O are mixed and ball milled, dried and ground, then put into a tube furnace for sintering, naturally cooled, and the product is ground to a certain mesh size to obtain a precursor; C6H 12O6·H2O is used to coat lithium iron phosphate once to improve the electron transmission capacity between particles, and the carbon coating can limit the growth of lithium iron phosphate grains during high-temperature sintering, so as to maintain a smaller particle size, which is beneficial to the deintercalation of lithium ions; the precursor and deionized water are mixed and stirred, LiCl and InCl3 are added, and the temperature is raised under continuous stirring, grinding, dehydration, and sieving to obtain halide solid electrolyte Li3InCl6 coated lithium iron phosphate; carbon nanotubes are added to the mixed acid, ultrasonic dispersion is carried out, magnetic stirring is carried out in an oil bath, water washing is carried out, a dispersing agent and a solvent are added, mixing, stirring and ultrasonic dispersion are carried out, then Li3InCl6 coated lithium iron phosphate is added, and continuous ultrasonic dispersion and stirring are carried out, and then washing and drying are carried out to obtain modified lithium iron phosphate; Ti-V co-doping cooperatively broadens the band gap of lithium iron phosphate, and the lithium ion diffusion coefficient is improved, the charge transfer resistance is reduced, Ti + , and the specific capacity is improved. 4+ It is easy to produce cation vacancies, form p-type semiconductor, reduce the band gap of lithium iron phosphate, thereby effectively improve the conductivity of bulk material, accelerate the migration rate of ions, and improve the electrochemical performance of the material. 5+ V 5+ doping produces Fe 2+ vacancies, forms ion vacancies and cooperatively diffuses, increases the diffusion coefficient, reduces the resistance, and Ti-V electrons cooperatively promote Fe 2+ / Fe 3+ mixed valence state, improves electronic conductivity and reduces electronic conduction resistance; Cl - in Li3InCl6 reacts with O 2- on the surface of lithium iron phosphate to form Cl-O bridge bonds, reduce the interface energy barrier, reduce the interface defects, isolate the positive electrode material from the electrolyte, inhibit the side reaction, and reduce the interface impedance; carbon nanotube coating enhances the conductivity of the material and promotes the transmission of electrons; inhibits the agglomeration between lithium iron phosphate particles, reduces the diffusion path of Li + , reduces the charge transfer resistance, and at the same time increases the local lithium ion concentration gradient during the reaction, thereby promoting the diffusion of Li + at a small rate.

[0037] In the process of preparing a halide electrolyte modified low impedance positive electrode, a modified binder is first prepared, polyacrylic acid, deionized water, polyethylene oxide and LiOH·H2O are mixed and stirred, and then heated in a water bath, -COOH on polyacrylic acid reacts with C-O-C bond in polyethylene oxide to form crosslinking through hydrogen bond, and a modified binder is obtained, the crystallinity is reduced through hydrogen bond crosslinking reaction, the conductivity of the binder is improved, the ether oxygen bond of polyethylene oxide coordinates with Cl - in Li3InCl6, and the interface impedance between the electrode and the electrolyte is reduced.

[0038] In the process of preparing the halogenated electrolyte modified low impedance positive electrode, a modified conductive agent is first prepared, acetylene black, dopamine, tris (hydroxymethyl) aminomethane hydrochloride, deionized water and Na2S2O8 are mixed and stirred in a water bath, filtered, the filter cake is washed and dried to obtain the modified conductive agent; Na2S2O8 is used as an oxidizing agent, tris (hydroxymethyl) aminomethane hydrochloride is used as a buffer reagent, dopamine is polymerized and deposited on the acetylene black substrate, acetylene black provides effective adhesion space and polymerization space for dopamine, and through the strong oxidation effect of Na2S2O8, the catechol structure in dopamine is converted into quinone bond, the electrochemical activity is improved, the polydopamine coated acetylene black, and the surface amine group enhances the particle adsorption force and reduces the interparticle contact resistance. BRIEF DESCRIPTION OF DRAWINGS

[0039] In order to facilitate those skilled in the art to understand, the present application will be further described below with reference to the drawings.

[0040] Figure 1 The powder resistivity test results of the halogenated electrolyte modified low impedance positive electrode of examples 1-3 and comparative examples 1-3 are shown in the following figure.

[0041] Figure 2 The interface impedance test results of the halogenated electrolyte modified low impedance positive electrode of examples 1-3 and comparative examples 1-3 are shown in the following figure.

[0042] Figure 3 The 5C cycle 500 times capacity retention rate test results of the halogenated electrolyte modified low impedance positive electrode of examples 1-3 and comparative examples 1-3 are shown in the following figure. DETAILED DESCRIPTION

[0043] The technical solutions in the embodiments of the present application will be described below in conjunction with the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0044] Example 1:

[0045] A preparation process of a halogenated electrolyte modified low impedance positive electrode, comprising the following steps:

[0046] Step S1: 0.496 mol Fe(NO3)3·9H2O, 2 mol NaH2PO4, 0.0015 mol TiO2 and 0.0012 mol V2O5 were mixed and added into a planetary ball mill, 100 mL of anhydrous ethanol was added, the ball-to-material ratio was 10:1, the rotation speed was 300 r / min, and ball milling was performed for 6 h. The ball and the material were separated, 0.012 g of polyethylene glycol 2000 was added into a three-necked flask equipped with a stirrer and a thermometer, and mixed and stirred for 1 h. 18.02 g of urea was added, the three-necked flask was placed in a water bath at 95℃, and heated for reaction for 2 h. After the reaction was completed, precipitation aging, filtration, washing and drying were performed to obtain titanium-vanadium-doped iron phosphate;

[0047] Step S2: 80 g of titanium-vanadium-doped iron phosphate, 42.6 g of LiOH·H2O and 55 g of C6H 12 O6·H2O were mixed and added into a planetary ball mill, 400 mL of anhydrous ethanol was added, the ball-to-material ratio was 5:1, the rotation speed was 600 r / min, and ball milling was performed for 10 h. The ball and the material were separated, the material was dried at 80℃ and then ground, and then placed in a tube furnace. The sintering schedule was set as follows: 4 h of heat preservation at 25℃, then heating to 680℃, 10 h of constant temperature reaction, and finally natural cooling to 25℃. After sintering was completed, the product was ground through a 200-mesh sieve to obtain a precursor;

[0048] Step S3: 100 g of the precursor and 300 mL of deionized water were added into a three-necked flask equipped with a stirrer and a thermometer, mixed and stirred for 30 min, 7.45 g of LiCl and 4.29 g of InCl3 were added, stirred for 30 min, heated to 65℃ under continuous stirring for 2 h, placed in a mortar and ground for 15 min, and then added into a vacuum tube furnace for dehydration. The temperature was increased from 25℃ to 200℃ at a rate of 2℃ / min, and heat preservation was performed for 2 h. After heat preservation was completed, the material was naturally cooled to 25℃, and then sieved through a 400-mesh sieve to obtain Li3InCl6-coated lithium iron phosphate;

[0049] Step S4: 2 g of carbon nanotubes with an outer diameter of 1 nm and a length of 5 μm were added to 150 mL of a mixed acid of 98% by mass sulfuric acid and 68% by mass nitric acid in a volume ratio of 1:3, ultrasonic dispersion was performed for 20 min, it was placed in an oil bath at 120°C and magnetically stirred at 600 r / min for 3 h, then it was washed with deionized water twice to obtain acid-treated carbon nanotubes, 0.5 g of polyvinylpyrrolidone LUVITEC K90 Powder and 400 mL of anhydrous ethanol were added, mixing, stirring, ultrasonic dispersion were each performed for 30 min, then 98 g of Li3InCl6-coated lithium iron phosphate was added, ultrasonic dispersion and stirring were each performed for 15 min, it was washed with anhydrous ethanol three times to remove polyvinylpyrrolidone LUVITEC K90 Powder that did not participate in the compounding, free carbon nanotubes and water, it was placed in an oven and dried at 80°C to obtain modified lithium iron phosphate;

[0050] Step S5: 25 mL of polyacrylic acid llb75354, 275 mL of deionized water and 4.66 g of LiOH·H2O were added to a three-necked flask equipped with a stirrer and a thermometer, mixing and stirring were performed for 15 min, 3.4 g of polyethylene oxide P432440 was added, electromagnetic stirring was performed for 30 min, then it was placed in a water bath at 60°C and heated and stirred for 6 h to obtain a modified binder;

[0051] Step S6: 5 g of acetylene black N754, 1 g of dopamine, 24 g of tris-hydroxymethyl aminomethane hydrochloride, 200 mL of deionized water and 24 g of Na2S2O8 were added to a three-necked flask equipped with a stirrer and a thermometer, mixing and stirring were performed for 24 h in a water bath at 60°C, the obtained solution was suction filtered, the filter cake was washed with deionized water twice, the filter cake was transferred to a vacuum oven and vacuum dried at 70°C for 10 h to obtain a modified conductive agent;

[0052] Step S7: the modified lithium iron phosphate was weighed at 90 parts, the modified binder was weighed at 3 parts, the modified conductive agent was weighed at 3 parts and N-methyl pyrrolidone was weighed at 85 parts;

[0053] Step S8: the modified lithium iron phosphate, the modified binder and the modified conductive agent were subjected to dry mixing operation, the dry mixing conditions were a stirring speed of 20 r / min, a dispersion speed of 200 r / min and a time of 30 min to obtain a mixed powder; N-methyl pyrrolidone was added to the mixed powder for kneading operation, forward and reverse kneading was alternately performed, then high-speed dispersion operation was performed, the high-speed dispersion conditions were a stirring speed of 30 r / min, a dispersion speed of 1500 r / min and a dispersion time of 2 h to obtain a positive electrode slurry;

[0054] Step S9: the positive electrode slurry was uniformly coated on both sides of a carbon-coated aluminum foil with a thickness of 13 μm, the coating process was controlled to have a surface density of 23 mg / cm 2The coated carbon-coated aluminum foil is dried in an oven, and then cut by a mold to obtain a halogenated electrolyte modified low-impedance positive electrode.

[0055] Example 2:

[0056] A preparation process of a halogenated electrolyte modified low-impedance positive electrode, comprising the following steps:

[0057] Step S1: 0.784 mol Fe(NO3)3·9H2O, 3 mol NaH2PO4, 0.0023 mol TiO2 and 0.0018 mol V2O5 are mixed and added to a planetary ball mill, 150 mL of anhydrous ethanol is added, the ball-to-material ratio is 10:1, the rotation speed is 300 r / min, and ball milling is performed for 6 h. The ball and the material are separated, 0.012 g of polyethylene glycol 2000 is added to a three-necked flask equipped with a stirrer and a thermometer, and mixed and stirred for 1.5 h. 18.02 g of urea is added, the three-necked flask is placed in a water bath at 95℃, and heated for 2 h. After the reaction is completed, precipitation aging, filtration, washing and drying are performed to obtain titanium-vanadium-doped iron phosphate;

[0058] Step S2: 80 g of titanium-vanadium-doped iron phosphate, 42.6 g of LiOH·H2O and 55 g of C6H 12 O6·H2O are mixed and added to a planetary ball mill, 400 mL of anhydrous ethanol is added, the ball-to-material ratio is 5:1, the rotation speed is 600 r / min, and ball milling is performed for 10 h. The ball and the material are separated, the material is dried at 80℃ and ground, then placed in a tube furnace, and the sintering schedule is set as follows: 4 h of heat preservation at 25℃, then heating to 680℃, 10 h of constant temperature reaction, and finally natural cooling to 25℃. After sintering is completed, the product is ground through a 200-mesh sieve to obtain a precursor;

[0059] Step S3: 100 g of the precursor and 300 mL of deionized water are added to a three-necked flask equipped with a stirrer and a thermometer, mixed and stirred for 30 min, 7.45 g of LiCl and 4.29 g of InCl3 are added, stirred for 30 min, heated to 65℃ while continuously stirring for 2.5 h, placed in a mortar and ground for 25 min, and then dehydrated in a vacuum tube furnace at a rate of 2℃ / min from 25℃ to 200℃ for 2 h. After the heat preservation is completed, the material is naturally cooled to 25℃, and then sieved through a 400-mesh sieve to obtain Li3InCl6-coated lithium iron phosphate;

[0060] Step S4: 2.5 g of carbon nanotubes with an outer diameter of 2 nm and a length of 20 μm were added to 175 mL of a mixture of 98% by mass sulfuric acid and 68% by mass nitric acid in a volume ratio of 1:3, ultrasonically dispersed for 20 min, placed in an oil bath at 120°C and magnetically stirred at 600 r / min for 4 h, then washed with deionized water 3 times to obtain acid-treated carbon nanotubes, and then 0.5 g of polyvinylpyrrolidone LUVITEC K90 Powder, 400 mL of anhydrous ethanol were added, mixed and stirred, and ultrasonically dispersed for 30 min each time, then 98 g of Li3InCl6-coated lithium iron phosphate was added, and ultrasonic dispersion and stirring were continued for 15 min each time, then washed with anhydrous ethanol 4 times to remove polyvinylpyrrolidone LUVITEC K90 Powder that did not participate in the compounding, free carbon nanotubes and water, and then placed in an oven and dried at 80°C to obtain modified lithium iron phosphate;

[0061] Step S5: 25 mL of polyacrylic acid llb75354, 275 mL of deionized water and 4.66 g of LiOH·H2O were added to a three-necked flask equipped with a stirrer and a thermometer, mixed and stirred for 20 min, 3.4 g of polyethylene oxide P432440 was added, and electromagnetic stirring was performed for 30 min, and then the mixture was placed in a water bath at 60°C and stirred for 6 h to obtain a modified binder;

[0062] Step S6: 5 g of acetylene black N754, 1 g of dopamine, 24 g of tris-hydroxymethyl aminomethane hydrochloride, 300 mL of deionized water and 24 g of Na2S2O8 were added to a three-necked flask equipped with a stirrer and a thermometer, mixed and stirred in a water bath at 60°C for 24 h, the obtained solution was suction filtered, the filter cake was washed with deionized water 3 times, and then the filter cake was transferred to a vacuum oven and dried at 70°C for 10 h to obtain a modified conductive agent;

[0063] Step S7: the modified lithium iron phosphate was weighed as 93 parts, the modified binder was weighed as 4 parts, the modified conductive agent was weighed as 4 parts, and N-methyl pyrrolidone was weighed as 88 parts;

[0064] Step S8: the modified lithium iron phosphate, the modified binder and the modified conductive agent were dry-mixed, the dry-mixing conditions were a stirring speed of 20 r / min, a dispersing speed of 200 r / min and a time of 30 min to obtain a mixed powder; N-methyl pyrrolidone was added to the mixed powder for kneading, and the forward and reverse kneading was alternately performed, and then high-speed dispersion was performed, the high-speed dispersion conditions were a stirring speed of 30 r / min, a dispersing speed of 1500 r / min and a dispersion time of 2.5 h to obtain a positive electrode slurry;

[0065] Step S9: the positive electrode slurry was uniformly coated on both sides of a carbon-coated aluminum foil with a thickness of 13 μm, and the coating process was controlled to have a surface density of 23 mg / cm2.2 The coated carbon-coated aluminum foil is dried in an oven, and then cut by a mold to obtain a halogenated electrolyte modified low-impedance positive electrode.

[0066] Example 3:

[0067] A preparation process of a halogenated electrolyte modified low-impedance positive electrode, comprising the following steps:

[0068] Step S1: 0.992 mol Fe(NO3)3·9H2O, 4 mol NaH2PO4, 0.003 mol TiO2 and 0.0025 mol V2O5 are mixed and added to a planetary ball mill, 200 mL of anhydrous ethanol is added, the ball-to-material ratio is 10:1, the rotation speed is 300 r / min, and ball milling is performed for 6 h. The ball and the material are separated, 0.012 g of polyethylene glycol 2000 is added to a three-necked flask equipped with a stirrer and a thermometer, and mixed and stirred for 2 h. 18.02 g of urea is added, the three-necked flask is placed in a water bath at 95°C, and heated for 2 h. After the reaction is completed, precipitation aging, filtration, washing and drying are performed to obtain titanium-vanadium-doped iron phosphate;

[0069] Step S2: 80 g of titanium-vanadium-doped iron phosphate, 42.6 g of LiOH·H2O and 55 g of C6H 12 O6·H2O are mixed and added to a planetary ball mill, 400 mL of anhydrous ethanol is added, the ball-to-material ratio is 5:1, the rotation speed is 600 r / min, and ball milling is performed for 10 h. The ball and the material are separated, the material is dried at 80°C and ground, then placed in a tube furnace, and the sintering schedule is set as follows: 4 h of heat preservation at 25°C, then heating to 680°C, 10 h of constant temperature reaction, and finally natural cooling to 25°C. After sintering is completed, the product is ground through a 200-mesh sieve to obtain a precursor;

[0070] Step S3: 100 g of the precursor and 300 mL of deionized water are added to a three-necked flask equipped with a stirrer and a thermometer, mixed and stirred for 30 min, 7.45 g of LiCl and 4.29 g of InCl3 are added, stirred for 30 min, heated to 65°C while continuously stirring for 3 h, placed in a mortar and ground for 30 min, and then dehydrated in a vacuum tube furnace at a rate of 2°C / min from 25°C to 200°C for 2 h. After the heat preservation is completed, the material is naturally cooled to 25°C, and then sieved through a 400-mesh sieve to obtain Li3InCl6-coated lithium iron phosphate;

[0071] Step S4: 3 g of carbon nanotubes with an outer diameter of 2 nm and a length of 30 μm were added to 200 mL of a mixture of 98% mass fraction sulfuric acid and 68% mass fraction nitric acid in a volume ratio of 1:3, ultrasonic dispersion was performed for 20 min, and the mixture was placed in an oil bath at 120°C and magnetically stirred at 600 r / min for 4 h, then washed with deionized water 3 times, to obtain acid-treated carbon nanotubes, then 0.5 g of polyvinylpyrrolidone LUVITEC K90 Powder, 400 mL of anhydrous ethanol were added, mixed and stirred, and ultrasonic dispersion was performed for 30 min, then 98 g of Li3InCl6-coated lithium iron phosphate was added, and ultrasonic dispersion and stirring were continued for 15 min each, then washed with anhydrous ethanol 4 times to remove the dispersant that did not participate in the compounding, free carbon nanotubes and water, and placed in an oven to dry at 80°C, to obtain modified lithium iron phosphate;

[0072] Step S5: 25 mL of polyacrylic acid llb75354, 275 mL of deionized water and 4.66 g of LiOH H2O were added to a three-necked flask equipped with a stirrer and a thermometer, mixed and stirred for 30 min, 3.4 g of polyethylene oxide P432440 was added, electromagnetic stirring was performed for 30 min, then placed in a water bath at 60°C and heated and stirred for 6 h, to obtain a modified binder;

[0073] Step S6: 5 g of acetylene black N754, 1 g of dopamine, 24 g of tris-hydroxymethyl aminomethane hydrochloride, 400 mL of deionized water and 24 g of Na2S2O8 were added to a three-necked flask equipped with a stirrer and a thermometer, mixed and stirred in a water bath at 60°C for 24 h, the obtained solution was suction filtered, the filter cake was washed with deionized water 3 times, and the filter cake was transferred to a vacuum oven and vacuum dried at 70°C for 10 h, to obtain a modified conductive agent;

[0074] Step S7: the modified lithium iron phosphate was weighed at 95 parts, the modified binder was weighed at 5 parts, the modified conductive agent was weighed at 5 parts, and N-methyl pyrrolidone was weighed at 90 parts;

[0075] Step S8: the modified lithium iron phosphate, the modified binder and the modified conductive agent were dry mixed, the dry mixing conditions were a stirring speed of 20 r / min, a dispersion speed of 200 r / min and a time of 30 min, to obtain a mixed powder; N-methyl pyrrolidone was added to the mixed powder for kneading, and the forward and reverse kneading was alternately performed, then high-speed dispersion was performed, the high-speed dispersion conditions were a stirring speed of 30 r / min, a dispersion speed of 1500 r / min and a dispersion time of 3 h, to obtain a positive electrode slurry;

[0076] Step S9: the positive electrode slurry was uniformly coated on both sides of a carbon-coated aluminum foil with a thickness of 13 μm, and the coating process was controlled to have a surface density of 23 mg / cm 2The coated carbon-coated aluminum foil is dried in an oven, and then cut by a mold to obtain a halogenated electrolyte modified low-impedance positive electrode.

[0077] Comparative Example 1

[0078] A preparation process of a halogenated electrolyte modified low-impedance positive electrode, comprising the following steps:

[0079] Step S1: 0.784 mol Fe(NO3)3·9H2O and 3 mol NaH2PO4 are mixed and added to a planetary ball mill, 150 mL of anhydrous ethanol is added, the ball-to-material ratio is 10:1, the rotation speed is 300 r / min, and ball milling is performed for 6 h. The ball and the material are separated, 0.012 g of polyethylene glycol 2000 is added to a three-necked flask provided with a stirrer and a thermometer, and mixed and stirred for 1.5 h. Then, 18.02 g of urea is added, the three-necked flask is placed in a water bath at 95°C, and heated for reaction for 2 h. After the reaction is completed, precipitation aging, filtration, washing, and drying are performed to obtain iron phosphate;

[0080] Step S2: 80 g of iron phosphate, 42.6 g of LiOH·H2O, and 55 g of C6H 12 O6·H2O are mixed and added to a planetary ball mill, 400 mL of anhydrous ethanol is added, the ball-to-material ratio is 5:1, the rotation speed is 600 r / min, and ball milling is performed for 10 h. The ball and the material are separated, the material is dried at 80°C and ground, and then placed in a tube furnace. The sintering schedule is set as follows: 4 h of heat preservation at 25°C, then heating to 680°C, 10 h of constant temperature reaction, and finally natural cooling to 25°C. After sintering is completed, the product is ground through a 200-mesh sieve to obtain a precursor;

[0081] Step S3: 100 g of the precursor and 300 mL of deionized water are added to a three-necked flask provided with a stirrer and a thermometer, mixed and stirred for 30 min, 7.45 g of LiCl and 4.29 g of InCl3 are added, stirred for 30 min, heated to 65°C under continuous stirring for 2.5 h, placed in a mortar and ground for 25 min, and then dehydrated in a vacuum tube furnace at a rate of 2°C / min from 25°C to 200°C for 2 h. After the heat preservation is completed, the material is naturally cooled to 25°C, taken out, and sieved through a 400-mesh sieve to obtain Li3InCl6-coated lithium iron phosphate;

[0082] Step S4: Li3InCl6-coated lithium iron phosphate 93 parts, lithium polyacrylate TOB-PAALi 4 parts, acetylene black N754 4 parts, and N-methyl pyrrolidone 88 parts are weighed according to the weight components;

[0083] Step S5: Li3InCl6-coated lithium iron phosphate, lithium polyacrylate TOB-PAALi and acetylene black N754 are subjected to dry mixing operation, the dry mixing conditions are: stirring speed 20 r / min, dispersion speed 200 r / min, time 30 min, to obtain a mixed powder; N-methyl pyrrolidone is added to the mixed powder for kneading operation, using cis-trans kneading alternately, and then high-speed dispersion operation is performed, the high-speed dispersion conditions are: stirring speed 30 r / min, dispersion speed 1500 r / min, dispersion time 2.5 h, to obtain a positive electrode slurry;

[0084] Step S6: the positive electrode slurry is uniformly coated on both sides of an aluminum foil with a thickness of 13 μm, the coating process controls the area density to be 23 mg / cm 2 ; the coated aluminum foil is dried in an oven, and then cut by a mold to obtain a halogenated electrolyte modified low-impedance positive electrode.

[0085] Comparative Example 2:

[0086] A preparation process of a halogenated electrolyte modified low-impedance positive electrode, comprising the following steps:

[0087] Step S1: 0.784 mol Fe(NO3)3·9H2O, 3 mol NaH2PO4, 0.0023 mol TiO2 and 0.0018 mol V2O5 are mixed and added to a planetary ball mill, 150 mL of anhydrous ethanol is added, the ball-to-material ratio is 10:1, the rotation speed is 300 r / min, and ball milling is performed for 6 h, the ball and the material are separated, 0.012 g of polyethylene glycol 2000 is added to a three-necked flask equipped with a stirrer and a thermometer, and mixed and stirred for 1.5 h, 18.02 g of urea is added, the three-necked flask is placed in a water bath at 95℃, and heated for reaction for 2 h, after the reaction is completed, precipitation aging, filtration, washing and drying are performed, to obtain titanium-vanadium-doped iron phosphate;

[0088] Step S2: 80 g of titanium-vanadium-doped iron phosphate, 42.6 g of LiOH·H2O and 55 g of C6H 12 O6·H2O are mixed and added to a planetary ball mill, 400 mL of anhydrous ethanol is added, the ball-to-material ratio is 5:1, the rotation speed is 600 r / min, and ball milling is performed for 10 h, the ball and the material are separated, the material is dried and ground at 80℃, and then put into a tube furnace, the sintering schedule is set as: keeping at 25℃ for 4 h, then heating to 680℃, keeping at constant temperature for 10 h, and finally naturally cooling to 25℃, after the sintering is completed, the product is ground through a 200-mesh sieve, to obtain a precursor;

[0089] Step S3: 100 g of the precursor, 300 mL of deionized water were added to a three-necked flask equipped with a stirrer, a thermometer, mixed and stirred for 30 min, 7.45 g of LiCl and 4.29 g of InCl3 were added, stirred for 30 min, heated to 65°C at a constant stirring state for 2.5 h, placed in a mortar and ground for 25 min, dehydrated in a vacuum tube furnace, heated from 25°C to 200°C at a rate of 2°C / min for 2 h, and then naturally cooled to 25°C. After the completion of the incubation, the material was removed and sieved through a 400-mesh sieve to obtain Li3InCl6-coated lithium iron phosphate;

[0090] Step S4: 2.5 g of carbon nanotubes with an outer diameter of 2 nm and a length of 20 μm were added to 175 mL of a mixture of 98% sulfuric acid and 68% nitric acid in a volume ratio of 1:3, ultrasonically dispersed for 20 min, placed in an oil bath at 120°C and magnetically stirred at 600 r / min for 4 h, then washed with deionized water 3 times to obtain acid-treated carbon nanotubes, then 0.5 g of polyvinylpyrrolidone LUVITEC K90 Powder and 400 mL of anhydrous ethanol were added, mixed and stirred, and ultrasonically dispersed for 30 min each, then 98 g of Li3InCl6-coated lithium iron phosphate was added, and ultrasonic dispersion and stirring were continued for 15 min each, then washed with anhydrous ethanol 4 times to remove polyvinylpyrrolidone LUVITEC K90 Powder and free carbon nanotubes that did not participate in the compounding and water, and then placed in an oven and dried at 80°C to obtain modified lithium iron phosphate;

[0091] Step S5: The modified lithium iron phosphate, lithium polyacrylate TOB-PAALi, acetylene black N754, and N-methylpyrrolidone were weighed according to the weight components, and the modified lithium iron phosphate, lithium polyacrylate TOB-PAALi, and acetylene black N754 were dry mixed to obtain a mixed powder; N-methylpyrrolidone was added to the mixed powder and kneaded, and then subjected to high-speed dispersion to obtain a positive electrode slurry.

[0092] Step S6: The modified lithium iron phosphate, lithium polyacrylate TOB-PAALi, and acetylene black N754 were dry mixed to obtain a mixed powder; N-methylpyrrolidone was added to the mixed powder and kneaded, and then subjected to high-speed dispersion to obtain a positive electrode slurry.

[0093] Step S7: The positive electrode slurry was uniformly coated on both sides of a carbon-coated aluminum foil with a thickness of 13 μm, and the coating process was controlled to have a surface density of 23 mg / cm 2 ; The coated carbon-coated aluminum foil was dried in an oven, and then cut with a mold to obtain a halogen electrolyte-modified low-impedance positive electrode.

[0094] Comparative Example 3:

[0095] A preparation process of a halogenated electrolyte modified low-impedance positive electrode, comprising the following steps:

[0096] Step S1: 0.784 mol Fe(NO3)3·9H2O, 3 mol NaH2PO4 are mixed and added into a planetary ball mill, 150 mL of anhydrous ethanol is added, the ball-to-material ratio is 10:1, the rotation speed is 300 r / min, ball milling is performed for 6 h, the ball and the material are separated, the material and 0.012 g of polyethylene glycol 2000 are added into a three-necked flask provided with a stirrer and a thermometer, and mixed and stirred for 1.5 h, 18.02 g of urea is added, the three-necked flask is placed in a water bath at 95℃, and heating reaction is performed for 2 h; after the reaction is completed, precipitation aging, filtration, washing and drying are performed to obtain iron phosphate;

[0097] Step S2: 80 g of iron phosphate, 42.6 g of LiOH·H2O and 55 g of C6H 12 O6·H2O are mixed and added into a planetary ball mill, 400 mL of anhydrous ethanol is added, the ball-to-material ratio is 5:1, the rotation speed is 600 r / min, ball milling is performed for 10 h, the ball and the material are separated, the material is dried at 80℃ and then ground, and then the material is placed in a tube furnace, a sintering schedule is set: 4 h of heat preservation at 25℃, then heating to 680℃, 10 h of constant temperature reaction, and finally natural cooling to 25℃; after the sintering is completed, the product is ground through a 200-mesh sieve to obtain a precursor;

[0098] Step S3: 100 g of the precursor and 300 mL of deionized water are added into a three-necked flask provided with a stirrer and a thermometer, mixed and stirred for 30 min, 7.45 g of LiCl and 4.29 g of InCl3 are added, stirred for 30 min, heated to 65℃ under continuous stirring for 2.5 h, placed in a mortar and ground for 25 min, and then dehydrated in a vacuum tube furnace, heated to 200℃ at a rate of 2℃ / min from 25℃ and kept for 2 h, and after the heat preservation is completed, the material is naturally cooled to 25℃, and then sieved through a 400-mesh sieve to obtain Li3InCl6-coated lithium iron phosphate;

[0099] Step S4: 25 mL of polyacrylic acid llb75354, 275 mL of deionized water and 4.66 g of LiOH·H2O are added into a three-necked flask provided with a stirrer and a thermometer, mixed and stirred for 20 min, 3.4 g of polyethylene oxide P432440 is added, electromagnetic stirring is performed for 30 min, and then the three-necked flask is placed in a water bath at 60℃ and heated and stirred for 6 h to obtain a modified binder;

[0100] Step S5: 5 g of acetylene black N754, 1 g of dopamine, 24 g of tris-hydroxymethyl aminomethane hydrochloride, 300 mL of deionized water, and 24 g of Na2S2O8 were added to a three-necked flask equipped with a stirrer and a thermometer, and placed in a 60°C water bath for mixing and stirring for 24 h. The obtained solution was suction filtered, the filter cake was washed with deionized water for 3 times, and the filter cake was transferred to a vacuum oven for vacuum drying at 70°C for 10 h to obtain a modified conductive agent;

[0101] Step S6: Li3InCl6-coated lithium iron phosphate 93 parts, modified binder 4 parts, modified conductive agent 4 parts, and N-methyl pyrrolidone 88 parts were weighed according to the weight components;

[0102] Step S7: The Li3InCl6-coated lithium iron phosphate, modified binder, and modified conductive agent were dry-mixed, the dry-mixing conditions were: stirring speed 20 r / min, dispersion speed 200 r / min, and time 30 min, to obtain a mixed powder. N-methyl pyrrolidone was added to the mixed powder for kneading, and the pro-anti kneading was alternately performed, followed by high-speed dispersion, the high-speed dispersion conditions were: stirring speed 30 r / min, dispersion speed 1500 r / min, and dispersion time 2.5 h, to obtain a positive electrode slurry;

[0103] Step S8: The positive electrode slurry was uniformly coated on both sides of a carbon-coated aluminum foil with a thickness of 13 μm, and the coating process was controlled to have a surface density of 23 mg / cm 2 ; the coated carbon-coated aluminum foil was dried in an oven, and then cut by a mold to obtain a halogen electrolyte modified low-impedance positive electrode.

[0104] The halogen electrolyte modified low-impedance positive electrode of Examples 1-3 and Comparative Examples 1-3 was used as a battery positive electrode, and a negative electrode slurry with graphite as an active material was uniformly coated on both sides of a copper foil with a thickness of 10 μm, and the coating surface density was 15 mg / cm 2 ; the coated copper foil was dried in an oven at a speed of 3 m / s for 20 m long at 100°C, and then cut by a mold to obtain a negative electrode sheet; LiPF6 was dissolved in a mixed solvent of ethylene carbonate, dimethyl carbonate, and methyl ethyl carbonate mixed at a volume ratio of 1:1:1 to obtain an electrolyte with a concentration of 1 mol / L; the positive electrode, the negative electrode sheet, a polyethylene UTEC 4041 separator, and the electrolyte were prepared into a battery; the powder resistivity was tested according to the GB / T 45324-2025 standard; the interface impedance was tested by EIS; and the electrochemical performance test results are shown in the accompanying drawings according to the GB / T 42260-2022 standard:

[0105] Referring to Figure 1 , Figure 2 and Figure 3As shown, according to the comparison between Example 2 and Comparative Example 1, it can be known that the doping of titanium-vanadium, the coating of carbon nanotubes, the coating of Li3InCl6, the addition of modified conductive agent and modified binder can obviously reduce the powder conductivity of the lithium iron phosphate positive electrode, the interface impedance and improve the capacity retention rate of the battery at 5C cycle; according to the comparison between Example 2 and Comparative Example 2, it can be known that the addition of the doping of titanium-vanadium, the coating of carbon nanotubes and the coating of Li3InCl6 can effectively reduce the powder conductivity and the interface impedance and improve the electrochemical performance; according to the comparison between Example 2 and Comparative Example 3, it can be known that the coating of Li3InCl6, the addition of modified conductive agent and modified binder can reduce the powder conductivity.

[0106] In the description of the present specification, the description referring to the terms "one embodiment", "an example", "a specific example" and the like means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In the present specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0107] The above is only an example and description of the present application, and those skilled in the art can make various modifications or supplements or use similar ways to replace the described specific embodiments, as long as they do not deviate from the invention or exceed the scope defined in the present application, which shall belong to the protection scope of the present application.

Claims

1. A halogenated electrolyte modified low impedance positive electrode characterized in that, The following components are included by mass parts: Modified lithium iron phosphate 90-95 parts, modified binder 3-5 parts and modified conductive agent 3-5 parts; The modified lithium iron phosphate is prepared by the following steps: Step a1: Fe(NO3)3·9H2O, NaH2PO4, TiO2 and V2O5 are mixed and added to a ball mill, anhydrous ethanol is ball milled, the ball and the material are separated, the material and a surfactant are mixed and stirred, urea is added and heated in a water bath for reaction, after the reaction is completed, precipitation aging, filtration, washing and drying are performed to obtain titanium-vanadium doped iron phosphate; Step a2: titanium-vanadium-doped iron phosphate, LiOH H2O and C6H 12 O6H2O were mixed into a ball mill, ethanol was added for ball milling, the balls and materials were separated, the materials were dried and ground after drying and grinding, and then were put into a tube furnace for sintering, and finally were naturally cooled. After sintering, the product was ground and sieved to obtain a precursor. Step a3: the precursor and deionized water are mixed and stirred, LiCl and InCl3 are added, stirring is performed, and the material is heated and ground under continuous stirring, vacuum tube furnace dehydration is performed, the temperature is raised to 200°C for heat preservation, and the material is taken out and sieved after natural cooling to obtain Li3InCl6 coated lithium iron phosphate; Step a4: carbon nanotubes are added to mixed acid and ultrasonically dispersed, magnetic stirring is performed in an oil bath, deionized water is used for washing to obtain acid treated carbon nanotubes, a dispersing agent and a solvent are added, mixing, stirring and ultrasonic dispersion are performed, then Li3InCl6 coated lithium iron phosphate is added, and ultrasonic dispersion and stirring are continued, anhydrous ethanol is used for washing, and the material is placed in an oven for drying to obtain modified lithium iron phosphate; The modified binder is prepared by the following steps: Step b1: polyacrylic acid, deionized water and LiOH·H2O are added to a three-necked flask equipped with a stirrer and a thermometer, mixing and stirring are performed for 15-30 min, polyethylene oxide is added, electromagnetic stirring is performed for 30 min, and then the material is placed in a 60°C water bath for heating and stirring for 6 h to obtain a modified binder; The modified conductive agent is prepared by the following steps: Step c1: acetylene black, dopamine, tris-hydroxymethyl aminomethane hydrochloride, deionized water and Na2S2O8 are added to a three-necked flask equipped with a stirrer and a thermometer, mixing and stirring are performed in a 60°C water bath for 24 h, the obtained solution is subjected to suction filtration, the filter cake is washed with deionized water for 2-3 times, and the filter cake is transferred to a vacuum oven for vacuum drying at 70°C for 10 h to obtain a modified conductive agent.

2. The halogenated electrolyte-modified low-impedance positive electrode according to claim 1, characterized in that, The amount ratio of Fe(NO3)3·9H2O, NaH2PO4, TiO2, V2O5, anhydrous ethanol, a surfactant and urea in step a1 is 0.496-0.992 mol:2-4 mol:0.0015-0.003 mol:0.0012-0.0025 mol:100-200 mL:0.012 g:18.02 g; the surfactant is polyethylene glycol.

3. The halogenated electrolyte-modified low-impedance positive electrode according to claim 1, characterized in that, The amount ratio of the titanium-vanadium-doped iron phosphate, LiOH H2O, C6H 12 O6 H2O and anhydrous ethanol in step a2 is 80 g:42.6 g:55 g:400 mL; the amount ratio of the precursor, deionized water, LiCl and InCl3 in step a3 is 100 g:300 mL:7.45 g:4.29 g.

4. The halogenated electrolyte-modified low-impedance positive electrode according to claim 1, characterized in that, The amount ratio of carbon nanotubes, mixed acid, dispersing agent, solvent and Li3InCl6 coated lithium iron phosphate in step a4 is 2-3 g:150-200 mL:0.5 g:400 mL:98 g; the carbon nanotubes have an outer diameter of 1-2 nm and a length of 5-30 μm; the mixed acid is mixed acid of 98% sulfuric acid and 68% nitric acid in a volume ratio of 1:3; the dispersing agent is polyvinylpyrrolidone; and the solvent is anhydrous ethanol.

5. The halogenated electrolyte-modified low-impedance positive electrode according to claim 1, characterized in that, The amount ratio of polyacrylic acid, deionized water, LiOH H2O and polyethylene oxide in step b1 is 25 mL:275 mL:4.66 g:3.4 g.

6. The halogenated electrolyte-modified low-impedance positive electrode according to claim 1, characterized in that, The amount ratio of acetylene black, dopamine, tris-hydroxymethyl aminomethane hydrochloride, deionized water and Na2S2O8 in step c1 is 5 g:1 g:24 g:200-400 mL:24 g.

7. Process for the preparation of halogenated electrolyte modified low impedance positive electrodes, characterized in that, A method for preparing the halogenated electrolyte modified low impedance anode as claimed in any one of claims 1-6, comprising the following steps: Step one: according to the weight component, take modified lithium iron phosphate 90-95 parts, modified binder 3-5 parts, modified conductive agent 3-5 parts and N-methyl pyrrolidone 85-90 parts; Step two: dry mixing operation is carried out on the modified lithium iron phosphate, modified binder and modified conductive agent, the dry mixing condition is stirring speed 20 r / min and dispersion speed 200 r / min, time 30 min, to obtain mixed powder; kneading operation is carried out on the mixed powder by adding N-methyl pyrrolidone, using cis-trans kneading alternately, then high speed dispersion operation is carried out, the high speed dispersion condition is stirring speed 30 r / min and dispersion speed 1500 r / min, dispersion time 2-3 h, to obtain anode slurry; Step three: uniformly coat the positive electrode slurry on both sides of the carbon-coated aluminum foil, and control the surface density during the coating process to be 23 mg / cm 2 ; dry the coated carbon-coated aluminum foil in an oven, and then cut it with a mold to obtain a halogenated electrolyte modified low-impedance positive electrode.

8. The application of the halogenated electrolyte modified low impedance anode as claimed in any one of claims 1-6 in lithium ion battery.

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