Aqueous lithium iron positive electrode sheet and preparation method thereof

Abstract

The application discloses a water-based lithium iron positive plate and a preparation method thereof. The positive plate is a water-based positive slurry, and comprises LFP, carbon nanotubes CNT, a conductive agent SP, a water-based binder, a dispersing agent and deionized water. The preparation method of the water-based lithium iron positive plate is started from aspects of a positive formula, coating parameters and process technology, and the like. By adding an NMP+PC (1:2) mixed solution in mixing, strictly controlling slurry viscosity, and low-speed stirring in a turnover tank, guarantee is provided for slurry coating. By controlling coating temperature, installing a humidifying device, and starting from a single side, and controlling workshop temperature and humidity, the water-based lithium iron positive plate is coated on a single side without edge curling, edge cracking, hardness and brittleness, and generation breakage. The water-based positive plate has solved the problem that the water-based positive plate cannot be mass-produced all the time, and a feasible preparation method of the water-based lithium iron positive plate is successfully developed. The prepared battery has similar performance to that of an oil-based lithium battery, is lower in cost, and is green and pollution-free.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of lithium ion batteries, in particular to a water-based lithium iron positive electrode sheet and a preparation method thereof. BACKGROUND

[0002] The positive electrode mixing process of a lithium ion battery is divided into oil-based and water-based, and the oil-based, mainly NMP solvent + PVDF binder, is widely used at present. In the past two years, with the rapid development of PVDF and NMP prices, the cost of lithium batteries is high, and NMP is an organic solvent with certain toxicity, and long-term contact with personnel is not conducive to health.

[0003] Deionized water is used as a solvent, which is low in cost and has no toxic side effects, and is a research hotspot in the industry to replace NMP. However, the water-based adhesive on the market cannot solve the hard and brittle problems of the product, and when used as a positive electrode, it is easy to roll, crack and break at the edge when single-sided coating, and cannot be mass-produced. SUMMARY

[0004] The purpose of the present application is to overcome the shortcomings of the prior art, provide a water-based lithium iron positive electrode sheet and a preparation method thereof, and the temperature of the coating oven plays a key role. The oil-based coating has no high requirement on the temperature of the oven, and the set value of +10 DEG C is not a problem, while the water-based coating has strict requirements on the temperature of the oven and needs to be accurately controlled to ensure that the set value is within +5 DEG C. Through accurate temperature control, the positive electrode sheet is in a humid state under the premise of ensuring that the single side does not stick to the roller, which can ensure that the positive electrode sheet does not roll, crack and break at the edge, and the problem of mass production of water-based positive electrodes is solved.

[0005] A water-based lithium iron positive electrode sheet, the positive electrode sheet is a water-based positive electrode slurry, the water-based positive electrode slurry comprises lithium iron phosphate LFP, carbon nanotube CNT, conductive agent SP, water-based binder, dispersant and deionized water; the mass ratio of lithium iron phosphate LFP, carbon nanotube CNT, conductive agent SP and water-based binder is (93.8%~94.2%) :(0.5%~1.5%) :(1.5%~2.5%) :(2.8%~3.2%); the mass of deionized water is 55.9% of the mass of lithium iron phosphate LFP, and the dispersant accounts for 3% of the mass of deionized water.

[0006] Preferably, the water-based binder is a high molecular polymer polymerized from polyacrylonitrile-based multi-component copolymer and acrylic active monomer, and the dispersant is any one or two of N-methyl pyrrolidone, ethylene carbonate and propylene carbonate.

[0007] A preparation method of a water-based lithium iron positive electrode sheet, comprising the following steps:

[0008] Step one: according to the above formula, 35% to 50% of deionized water is weighed, the water-based adhesive is added, the revolution is 15 rpm, the rotation is 500 rpm, and the stirring time is 20 min to 30 min;

[0009] Step two: the conductive agent SP and the carbon nanotube CNT are added to the stirring cylinder, the slow revolution is 15 rpm, the rotation is 500 rpm, the stirring time is 10 min to 20 min, the high-speed revolution is 32 rpm, the rotation is 1200 rpm, and the stirring time is 70 min to 110 min;

[0010] Step three: the lithium iron phosphate LFP is added to the stirring cylinder in two equal parts, the slow revolution is 15 rpm, the rotation is 500 rpm, the stirring time is 10 min to 20 min, the high-speed revolution is 32 rpm, the rotation is 1200 rpm, and the stirring time is 120 min to 180 min;

[0011] Step four: 30% of deionized water is added, the high-speed revolution is 32 rpm, the rotation is 1200 rpm, and the stirring time is 30 min to 60 min;

[0012] Step five: a 3% NMP and PC mixed solution is added, the mass ratio of NMP and PC is 1:2;

[0013] Step six: the viscosity is adjusted by the remaining deionized water, the slurry viscosity is controlled at 3500-5000 mPa.s, a 4# rotor is used for viscosity testing at 60 rpm, and the slurry temperature is controlled at 25-30℃;

[0014] Step seven: the slurry is passed through a 150-mesh sieve, and then punched into a turnover tank, and the revolution is started at 15 rpm to ensure that the slurry is in a low-speed stirring state;

[0015] Step eight: the slurry is coated and high-vacuum dried in the workshop, the oven temperature is divided into eight sections, the single-side temperature is 50℃-85℃, and the double-side temperature is 75℃-105℃.

[0016] Preferably, the oven temperature is divided into eight sections by setting the middle high and the two ends low, the single-side temperature is 50℃-85℃, and the double-side temperature is 75℃-105℃.

[0017] Preferably, the workshop environment control requirements in step eight are: temperature 25℃±5℃, humidity 25%-55%.

[0018] Compared with the closest prior art, the technical scheme provided by the present application has the following beneficial effects:

[0019] 1、The present application adopts deionized water as a solvent, low cost, no toxic side effects; by adding NMP+PC (1:2) mixed solution in the mixing, through 4# rotor, 60 rpm viscosity test and 25~30℃ slurry temperature strict control slurry viscosity, and low speed stirring in the turnover tank, provide guarantee for slurry coating; prevent viscosity too high, easy pseudoplastic, coating uneven, viscosity too low, coating easy to explode, can't be coated;

[0020] 2, the prior art is generally oil-based coating, the oven temperature requirement is not high, the set value ±10℃ is no problem, while the water-based coating is strict to the oven temperature, needs accurate control, ensures that the set value is within ±5℃; the coating temperature and humidity control in the present application is the key to the success of the water-based lithium iron positive plate, through the coating temperature section setting, installation of humidifying device single side start, and control of workshop temperature and humidity research, make the water-based lithium iron positive single coating no edge curling, no edge cracking, no hard brittle, no generation problem, solve the problem that the water-based positive electrode has been unable to mass produce for a long time;

[0021] 3, install a humidifier at the coating out of the oven position, turn it on when single coating, increase the flexibility of the plate, solve the problems of hard brittle, edge cracking, curling and generation of the plate after drying in the oven. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 The present application is a water-based lithium iron positive plate preparation method flow chart;

[0023] Figure 2 The present application is a water-based lithium iron positive plate preparation method flow chart;

[0024] Figure 3 The present application is a water-based lithium iron positive plate preparation method flow chart;

[0025] Figure 4 The present application is a water-based lithium iron positive plate preparation method flow chart; DETAILED DESCRIPTION

[0026] The technical solutions in the embodiments of the present application will be described in detail below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, not all. 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.

[0027] Please refer to Figures 1 to 4 :

[0028] Figure 2 The present application is a water-based lithium iron positive plate preparation method flow chart; The present application is a water-based lithium iron positive plate preparation method flow chart;

[0029] Figure 3 For the rate performance comparison chart of Example 7 and Comparative Example 1, the upper curve in the figure is the oil-based positive electrode lithium-iron battery (0.2C), the middle curve is the water-based positive electrode lithium-iron battery (1.0C), and the lower curve is the oil-based positive electrode lithium-iron battery (1.0C);

[0030] Figure 4 For the discharge performance comparison chart at different temperatures of Example 7 and Comparative Example 1, the uppermost curve in the figure is the water-based positive electrode lithium-iron battery (60℃), followed by the oil-based positive electrode lithium-iron battery (60℃), then the water-based positive electrode lithium-iron battery (-20℃), and the lowermost is the oil-based positive electrode lithium-iron battery (-20℃).

[0031] A water-based lithium-iron positive electrode sheet, the positive electrode sheet is a water-based positive electrode slurry, the water-based positive electrode slurry comprises lithium-iron phosphate LFP, carbon nanotube CNT, conductive agent SP, water-based binder, dispersant, and deionized water; the mass ratio of lithium-iron phosphate LFP, carbon nanotube CNT, conductive agent SP, and water-based binder is (93.8%~94.2%):(0.5%~1.5%):(1.5%~2.5%):(2.8%~3.2%); the mass of deionized water is 55.9% of the mass of lithium-iron phosphate LFP, and the dispersant accounts for 3% of the mass of deionized water. Deionized water is used as the solvent, which is low in cost and has no toxic side effects.

[0032] Preferably, the water-based binder is a polyacrylonitrile-based multi-component copolymer, a high-molecular polymer polymerized from acrylic acid active monomers, and the dispersant is any one or two of N-methyl pyrrolidone, ethylene carbonate, and propylene carbonate.

[0033] A preparation method of a water-based lithium-iron positive electrode sheet, comprising the following steps:

[0034] Step one: according to the above formula, 35%~50% of deionized water is weighed and added to the water-based binder, with 15 rpm of revolution and 500 rpm of rotation, and the stirring time is 20 min~30 min;

[0035] Step two: the conductive agent SP and carbon nanotube CNT are added to the stirring cylinder, with 15 rpm of slow revolution and 500 rpm of rotation; the stirring time is 10 min~20 min; with 32 rpm of high-speed revolution and 1200 rpm of rotation; the stirring time is 70 min~110 min;

[0036] Step three: lithium-iron phosphate LFP is added to the stirring cylinder in two equal parts, with 15 rpm of slow revolution and 500 rpm of rotation; the stirring time is 10 min~20 min; with 32 rpm of high-speed revolution and 1200 rpm of rotation; the stirring time is 120 min~180 min;

[0037] Step four: add 30% deionized water, high revolution 32 rpm, rotation 1200 rpm; stirring time 30 min-60 min;

[0038] Step five: add 3% NMP and PC mixed solution, mass ratio of NMP and PC 1:2;

[0039] Step six: adjust the viscosity by the remaining deionized water, ensure the slurry viscosity control in 3500-5000 mPa.s; use 4# rotor, 60 rpm for viscosity test, slurry temperature control in 25-30℃; 4# rotor, 60 rpm refers to the viscosity test requirements, because the results measured by different rotors and different speeds are different. 25-30℃ refers to the slurry temperature, because the viscosity of the slurry is different at different temperatures; the slurry viscosity should be controlled in 3500-5000 mPa.s because too high viscosity is easy to be pseudoplastic, uneven coating, too low viscosity is easy to blow edge, and cannot be coated.

[0040] Step seven: sieve the slurry through 150 mesh, then put into the turnover tank, open revolution 15 rpm, ensure the slurry in low speed stirring state;

[0041] Step eight: coat and high vacuum drying treatment to the slurry, oven temperature is divided into eight sections, the temperature is set as eight sections, single side coating temperature: 50℃-85℃; double side coating temperature: 75℃-105℃, workshop environment control requirements in step eight: temperature 25℃±5℃, humidity 25%-55%, coating temperature and humidity control is the key to the success of water-based lithium iron positive plate, through coating temperature section setting, installation of humidifying device, single side start, and control of workshop temperature and humidity, make water-based lithium iron positive plate single side coating without edge cracking, no edge cracking, no hard and brittle, no broken generation problem, solve the problem of water-based positive plate which has been unable to mass production for a long time.

[0042] Further, the oven temperature is divided into eight sections by setting high in the middle and low at both ends, single side temperature: 50℃-85℃; double side temperature: 75℃-105℃, workshop environment control requirements in step eight: temperature 25℃±5℃, humidity 25%-55%, coating temperature and humidity control is the key to the success of water-based lithium iron positive plate, through coating temperature section setting, installation of humidifying device, single side start, and control of workshop temperature and humidity, make water-based lithium iron positive plate single side coating without edge cracking, no edge cracking, no hard and brittle, no broken generation problem, solve the problem of water-based positive plate which has been unable to mass production for a long time.

[0043] Example 1:

[0044] Mixing:

[0045] 1) according to the formula, weigh 42% deionized water, add water-based binder, revolution 15 rpm, rotation 500 rpm, stirring time 25 min;

[0046] 2) Add conductive agent SP and carbon nanotube CNT into the stirring cylinder, slow revolution 15 rpm, rotation 500 rpm; stirring time 15 min; high revolution 32 rpm, rotation 1200 rpm; stirring time 90 min;

[0047] 3) Add lithium iron phosphate into the stirring cylinder in two equal portions, slow revolution 15 rpm, rotation 500 rpm; stirring time 15 min; high revolution 32 rpm, rotation 1200 rpm; stirring time 150 min;

[0048] 4) Add 30% deionized water, high revolution 32 rpm, rotation 1200 rpm; stirring time 60 min;

[0049] 5) Add 3% NMP+PC (1:2) mixed solution;

[0050] 6) Add 25% deionized water, slurry viscosity 4200 mPa.s (4# rotor, 60 rpm 25-30°C);

[0051] Coating parameters:

[0052]

[0053] Table 1 Oven temperature zone settings for Example 1

[0054] Example 2:

[0055] Mixing:

[0056] 1) Weigh 42% deionized water according to the formula, add water-based binder, revolution 15 rpm, rotation 500 rpm, stirring time 25 min;

[0057] 2) Add conductive agent SP and carbon nanotube CNT into the stirring cylinder, slow revolution 15 rpm, rotation 500 rpm; stirring time 15 min; high revolution 32 rpm, rotation 1200 rpm; stirring time 90 min;

[0058] 3) Add lithium iron phosphate into the stirring cylinder in two equal portions, slow revolution 15 rpm, rotation 500 rpm; stirring time 15 min; high revolution 32 rpm, rotation 1200 rpm; stirring time 150 min;

[0059] 4) Add 30% deionized water, high revolution 32 rpm, rotation 1200 rpm; stirring time 60 min;

[0060] 5) Add 3% NMP+PC (1:2) mixed solution;

[0061] 6) Add 25% deionized water, slurry viscosity 4200 mPa.s (4# rotor, 60 rpm 25~30°C);

[0062] Coating parameters:

[0063]

[0064] Table 2 Oven temperature zone settings for Example 2

[0065] Example 3:

[0066] Mixing:

[0067] 1) Weigh 42% deionized water according to the formula, add water-based binder, revolution 15 rpm, rotation 500 rpm, stirring time 25 min;

[0068] 2) Add conductive agent SP and carbon nanotube CNT to the stirring cylinder, slow revolution 15 rpm, rotation 500 rpm; stirring time 15 min; high revolution 32 rpm, rotation 1200 rpm; stirring time 90 min;

[0069] 3) Add lithium iron phosphate in two equal parts to the stirring cylinder, slow revolution 15 rpm, rotation 500 rpm; stirring time 15 min; high revolution 32 rpm, rotation 1200 rpm; stirring time 150 min;

[0070] 4) Add 30% deionized water, high revolution 32 rpm, rotation 1200 rpm; stirring time 60 min;

[0071] 5) Add 3% NMP+PC (1:2) mixed solution;

[0072] 6) Add 25% deionized water, slurry viscosity 4200 mPa.s (4# rotor, 60 rpm 25~30°C);

[0073] Coating parameters:

[0074]

[0075] Table 3 Oven temperature zone settings for Example 3

[0076] Example 4:

[0077] Mixing:

[0078] 1) Weigh 42% deionized water according to the formula, add water-based binder, revolution 15 rpm, rotation 500 rpm, stirring time 25 min;

[0079] 2) Add conductive agent SP and carbon nanotube CNT into the stirring cylinder, slow revolution 15 rpm, rotation 500 rpm; stirring time 15 min; high revolution 32 rpm, rotation 1200 rpm; stirring time 90 min;

[0080] 3) Add lithium iron phosphate into the stirring cylinder in two equal portions, slow revolution 15 rpm, rotation 500 rpm; stirring time 15 min; high revolution 32 rpm, rotation 1200 rpm; stirring time 150 min;

[0081] 4) Add 30% deionized water, high revolution 32 rpm, rotation 1200 rpm; stirring time 60 min;

[0082] 5) Add 28% deionized water, slurry viscosity 4350 mPa.s (4# rotor, 60 rotation speed 25-30°C);

[0083] Coating parameters:

[0084]

[0085] Table 4 Oven temperature zone settings for Example 4

[0086] Example 5:

[0087] Mixing:

[0088] 1) Weigh 42% deionized water according to the formula, add water-based binder, revolution 15 rpm, rotation 500 rpm, stirring time 25 min;

[0089] 2) Add conductive agent SP and carbon nanotube CNT into the stirring cylinder, slow revolution 15 rpm, rotation 500 rpm; stirring time 15 min; high revolution 32 rpm, rotation 1200 rpm; stirring time 90 min;

[0090] 3) Add lithium iron phosphate into the stirring cylinder in two equal portions, slow revolution 15 rpm, rotation 500 rpm; stirring time 15 min; high revolution 32 rpm, rotation 1200 rpm; stirring time 150 min;

[0091] 4) Add 30% deionized water, high revolution 32 rpm, rotation 1200 rpm; stirring time 60 min;

[0092] 5) Add 28% deionized water, slurry viscosity 4350 mPa.s (4# rotor, 60 rotation speed 25-30°C);

[0093] Coating parameters:

[0094]

[0095]

[0096] Table 5 Oven temperature zone settings for Example 5

[0097] Example 6:

[0098] Mixing:

[0099] 1) Weigh 42% deionized water according to the formula, add the water-based binder, 15 rpm revolution, 500 rpm rotation, stirring time 25 min;

[0100] 2) Add conductive agent SP and carbon nanotube CNT to the stirring cylinder, slow revolution 15 rpm, rotation 500 rpm; stirring time 15 min; high revolution 32 rpm, rotation 1200 rpm; stirring time 90 min;

[0101] 3) Add lithium iron phosphate in two equal parts to the stirring cylinder, slow revolution 15 rpm, rotation 500 rpm; stirring time 15 min; high revolution 32 rpm, rotation 1200 rpm; stirring time 150 min;

[0102] 4) Add 30% deionized water, high revolution 32 rpm, rotation 1200 rpm; stirring time 60 min;

[0103] 5) Add 28% deionized water, slurry viscosity 4350 mPa.s (4# rotor, 60 rpm 25-30°C);

[0104] Coating parameters:

[0105]

[0106] Table 6 Oven temperature zone settings for Example 6

[0107] Example 7:

[0108] Mixing:

[0109] 1) Weigh 42% deionized water according to the formula, add the water-based binder, 15 rpm revolution, 500 rpm rotation, stirring time 25 min;

[0110] 2) Add conductive agent SP and carbon nanotube CNT to the stirring cylinder, slow revolution 15 rpm, rotation 500 rpm; stirring time 15 min; high revolution 32 rpm, rotation 1200 rpm; stirring time 90 min;

[0111] 3) Add lithium iron phosphate into the stirring cylinder in two equal portions, slow revolution 15 rpm, rotation 500 rpm; stirring time 15 min; high revolution 32 rpm, rotation 1200 rpm; stirring time 150 min;

[0112] 4) Add 30% deionized water, high revolution 32 rpm, rotation 1200 rpm; stirring time 60 min;

[0113] 5) Add 28% deionized water, slurry viscosity 4350 mPa.s (4# rotor, 60 rpm 25-30°C);

[0114] Coating parameters:

[0115]

[0116] Table 7 Oven temperature zone settings for Example 7

[0117] 6) Subsequent processes such as rolling, slitting, punching, lamination, packaging, liquid injection, formation, and separation are performed to complete the lithium iron phosphate battery production, and the battery cycle performance, different temperature discharge performance, and rate performance are compared.

[0118] Comparative Example 1:

[0119] Mixing:

[0120] 1) Weigh 80% of the total amount of NMP according to the formula, add PVDF, first slow, then high speed stirring 33 rpm, high speed dispersion 1300 rpm, stirring time 150 min;

[0121] 2) Add conductive agent SP and CNT to the stirring cylinder according to the formula, first slow, then high speed stirring speed 32 rpm, high speed dispersion speed 1400 rpm, stirring time 90 min;

[0122] 3) Add lithium iron phosphate material and remaining NMP to the stirring cylinder according to the formula, first slow, then high speed stirring speed 32 rpm, high speed dispersion speed 1400 rpm, stirring time 180 min;

[0123] 4) Stirring temperature 20-55°C, vacuum degree ≤-80 kPa;

[0124] 5) Slurry viscosity control at 7350 mPa.s (4# rotor, 60 rpm 25-30°C);

[0125] 6) Slurry passes through a 150 mesh sieve, then punches into a turnover tank, opens revolution 15 rpm, ensures that the slurry is in a low speed stirring state;

[0126] Coating parameters: (temperature: set value ±10°C)

[0127]

[0128] Table 8 oven temperature zone setting of comparative example 1

[0129] 7) Subsequent roll - strip - blanking - lamination - packaging - injection - formation - separate process operation, complete lithium iron phosphate battery production, battery cycle performance, different temperature discharge performance, rate performance comparison.

[0130] The pole piece coating effect comparison in examples 1-7 is shown in the following table 9:

[0131]

[0132] Table 9 pole piece coating effect comparison table in examples 1-7

[0133] From the pole piece coating effect comparison table, example seven is the best, that is, add 3% NMP + PC (1:2) mixed solution, set the temperature in the middle, open the humidifying device, the slurry effect is good, the pole piece surface density consistency is good, the pole piece is good, and it can be continuously batch produced.

[0134] The above examples are only used to illustrate the technical solutions of the present application, but not to limit it. Although the present application has been described in detail with reference to the above examples, the ordinary skilled in the art can still modify or equivalently replace the specific embodiments of the present application. Any modification or equivalent replacement that does not deviate from the spirit and scope of the present application is within the protection scope of the claims of the application.

Claims

1. A method for preparing an aqueous lithium iron phosphate cathode, characterized in that: The aqueous lithium iron phosphate (LFP) cathode sheet is an aqueous cathode slurry, which includes lithium iron phosphate (LFP), carbon nanotubes (CNTs), conductive agent (SP), aqueous binder, dispersant, and deionized water. The mass ratio of LFP, CNTs, SP, and aqueous binder is 93.8%~94.2% : 0.5%~1.5% : 1.5%~2.5% : 2.8%~3.2%. The deionized water accounts for 55.9% of the mass of LFP, and the dispersant accounts for 3% of the mass of deionized water. The aqueous binder is a high-molecular polymer synthesized from polyacrylonitrile-based multi-component copolymers and acrylic acid active monomers. The dispersant is any one or two of N-methylpyrrolidone, ethylene carbonate, and propylene carbonate. The preparation method of the aqueous lithium iron phosphate cathode sheet includes the following steps: Step 1: Weigh out 35%~50% deionized water according to the above formula, add water-based binder, rotate at 15 rpm and 500 rpm, and stir for 20 min~30 min. Step 2: Add conductive agent SP and carbon nanotubes CNT to the mixing tank, slowly rotate at 15 rpm and spin at 500 rpm; stirring time 10 min~20 min; high speed rotate at 32 rpm and spin at 1200 rpm; stirring time 70 min~110 min. Step 3: Add the lithium iron phosphate (LFP) in two equal portions to the mixing tank. Rotate slowly at 15 rpm and 500 rpm; stirring time: 10-20 minutes. Then rotate at 32 rpm and 1200 rpm; stirring time: 120-180 minutes. Step 4: Add 30% deionized water, rotate at high speed (32 rpm) and spin at 1200 rpm; stir for 30-60 minutes. Step 5: Add 3% NMP and PC mixed solution, with a mass ratio of NMP to PC of 1:2; Step 6: Adjust the viscosity using the remaining deionized water to ensure the slurry viscosity is controlled between 3500 and 5000 mPa·s; use a #4 rotor at 60 rpm to test the viscosity, and control the slurry temperature between 25 and 30°C. Step 7: Pass the slurry through a 150-mesh sieve, then pump it into a transfer tank and start the revolution at 15 rpm to ensure that the slurry is in a low-speed stirring state. Step 8: In the workshop, the slurry is coated and dried under high vacuum. The oven temperature is divided into eight sections with a high temperature in the middle and low temperatures at both ends. The temperature for one side is 50℃~85℃, and the temperature for both sides is 75℃~105℃. A humidifier is installed at the position where the coating exits the oven. It is turned on when coating one side and turned off when coating both sides.

2. The method for preparing an aqueous lithium iron phosphate cathode according to claim 1, characterized in that: The workshop environment control requirements in step eight are: temperature 25℃±5℃, humidity 25%~55%.

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