Dispersing flexibilizer, its preparation method and application, lithium iron phosphate positive electrode slurry, lithium iron phosphate positive electrode sheet

Abstract

The present application relates to the technical field of lithium battery positive electrode material, in particular to a dispersing and softening agent, a preparation method and application thereof, a lithium iron phosphate positive electrode slurry and a lithium iron phosphate positive electrode sheet. The dispersing and softening agent has a structure shown in formula (I), wherein X is a core skeleton composed of a starter containing two or more than two conjugated aromatic rings and having a functionality of 1-3; R1 is a polyether segment and / or a saturated alkane chain; R2 is selected from one or more of a phosphate group, a sulfonate group, a carbonate group, a carboxyl group and a hydrogen atom; n is an integer greater than or equal to 0, and m is an integer of 1-3; the dispersing and softening agent has a number average molecular weight of 300-3000 g / mol. The dispersing and softening agent has both strong adsorption and dispersion capacity and positive electrode sheet softening effect, and also has excellent system compatibility and process controllability.

Description

Technical Field

[0001] This invention relates to the field of lithium battery cathode material technology, specifically to a dispersant and softening agent and its preparation method and application, lithium iron phosphate cathode slurry, and lithium iron phosphate cathode sheet. Background Technology

[0002] Lithium iron phosphate (LFP) has become the mainstream cathode material in the fields of power batteries and energy storage batteries due to its advantages such as high theoretical capacity (175mAh / g), excellent cycle stability, outstanding thermal safety, and low raw material cost. To improve the low intrinsic electronic conductivity of lithium iron phosphate, carbon coating modification is commonly used in industry, and conductive agents such as carbon black are added to the cathode slurry to construct a continuous electron transport network and improve the electrochemical performance of the battery.

[0003] As lithium-ion batteries develop towards higher energy density, improving the coating thickness and areal density of the positive electrode sheet has become a key technical path, which requires the positive electrode slurry to have high solid content. However, there are two major technical pain points in the preparation and electrode processing of high solid content lithium iron phosphate positive electrode slurry: (1) The carbon coating layer and carbon black are non-polar / weakly polar, with poor wettability with polar solvents such as NMP, and the particles are easy to agglomerate; the carbon black has a high specific surface area and a strong tendency to agglomerate, resulting in high slurry viscosity and poor fluidity, and the coating is prone to defects such as pinholes, scratches, and shrinkage cavities. Agglomerates will also block the transmission of electrons and lithium ions, reducing the rate performance and cycle stability of the battery. (2) LFP particles are rigid crystals, and both the carbon coating layer and carbon black are brittle materials. The flexibility adjustment ability of traditional PVDF binders is limited, and the electrode sheet is not flexible enough. Microcracks are easily generated during rolling and winding, resulting in damage to the conductive network and uneven electrolyte wetting, which seriously affects the mechanical stability and long-term cycle life of the battery.

[0004] In existing technologies, dispersants mostly have only a single dispersing function, and flexible agents mostly focus on improving electrode flexibility. There is a lack of efficient additives that integrate dispersion and flexibleization and are highly compatible with LFP systems. Moreover, some additives have problems such as weak adsorption, easy desorption, poor compatibility with the system, and complex processes, making it difficult to simultaneously meet the synergistic requirements of low viscosity, high dispersion, high electrode flexibility, and high compaction density of high solids content slurries.

[0005] Therefore, developing an integrated additive for lithium iron phosphate cathode slurry that combines efficient dispersion and excellent flexibility, has a simple preparation process, and is highly adaptable, is of significant industrial application value for improving the processing performance, electrochemical performance, and long-term reliability of lithium iron phosphate batteries. Summary of the Invention

[0006] This invention addresses the problems of easy particle agglomeration, high slurry viscosity, poor electrode flexibility, and low compaction density in existing lithium iron phosphate cathode slurries. It provides an integrated dispersant-flexible agent that combines strong adsorption and dispersion capabilities with electrode flexibility, while also exhibiting excellent system compatibility and process controllability. Furthermore, the preparation method of this dispersant-flexible agent is simple, uses readily available raw materials, and is suitable for industrial production. The cathode slurry prepared using this dispersant-flexible agent has the advantages of low viscosity and high dispersibility, and the electrode prepared using this slurry combines high flexibility with high compaction density.

[0007] To achieve the above objectives, in a first aspect, the present invention provides a dispersing softener having the structure shown in formula (I), , Wherein, X is the core skeleton composed of an initiator containing two or more conjugated aromatic rings and having a functionality of 1 to 3; R1 is a polyether segment and / or a saturated alkane chain; R2 is selected from one or more of the following groups: phosphate ester group, sulfonate group, carbonate group, carboxyl group, and hydrogen atom; n is an integer ≥ 0, and m is an integer from 1 to 3; The number average molecular weight of the dispersant and softener is 300~3000 g / mol.

[0008] Preferably, the initiator is selected from one or more of naphthalene derivatives, bisphenols, biphenyls, phenanthrene derivatives, anthracene derivatives, pyrene derivatives, 9,9-bis(4-hydroxyphenyl)fluorene, and 2,8-dihydroxydibenzothiophene.

[0009] More preferably, the initiator is selected from one or more of 2-naphthol, 1-naphthol, 1,6-naphthodiol, 1,5-naphthodiol, 2,6-naphthodiol, 1,5-naphthodiamine, 1,8-naphthodiamine, bisphenol A, bisphenol F, bisphenol S, 4,4'-dihydroxybiphenyl, 9-hydroxyphenanthrene, 9,10-anthraquinone, 1-hydroxypyrene, 9,9-bis(4-hydroxyphenyl)fluorene, and 2,8-dihydroxydibenzothiophene.

[0010] More preferably, the initiator is selected from one or more of 1,6-naphthol, bisphenol A, and 4,4'-dihydroxybiphenyl.

[0011] Preferably, R1 has the structure shown in formula (II). , Where R3 is -CH2-CH2-, EO is -CH2-CH2-O-, PO is -CH(CH3)-CH2-O-, n1, n2 and n3 are each independent integers ≥0, and 6≤n1+n2+n3≤20; R3, EO and PO are connected by block copolymerization.

[0012] Preferably, the molar ratio of EO to PO is 1:0.3~3, and the block arrangement is EO first and then PO.

[0013] Preferably, the number average molecular weight of the dispersant and softener is 400~2000 g / mol.

[0014] Secondly, the present invention provides a method for preparing a dispersing softener as described in the present invention, the method comprising the following steps: 1) Block polyether synthesis: The initiator and catalyst are dehydrated by reflux using a dehydrating agent. Under an inert atmosphere, they undergo a first polymerization reaction with ethylene oxide and a second polymerization reaction with propylene oxide. After removing impurities, an antioxidant is added to obtain block polyether. 2) Phosphorylation reaction: The block polyether is esterified with phosphorus pentoxide, hydrolyzed with water, and the pH of the product is adjusted to obtain the phosphorylated product; 3) Dehydration and solution preparation: The phosphorylated product is dehydrated and then dissolved in an organic polar solvent to obtain a dispersing and softening agent.

[0015] Preferably, in step 1), the dehydrating agent is selected from one or more of toluene, xylene, cyclohexane, and n-heptane.

[0016] Preferably, the initiator is selected from one or more of naphthalene derivatives, bisphenols, biphenyls, phenanthrene derivatives, anthracene derivatives, pyrene derivatives, 9,9-bis(4-hydroxyphenyl)fluorene, and 2,8-dihydroxydibenzothiophene.

[0017] More preferably, the initiator is selected from one or more of 2-naphthol, 1-naphthol, 1,6-naphthodiol, 1,5-naphthodiol, 2,6-naphthodiol, 1,5-naphthodiamine, 1,8-naphthodiamine, bisphenol A, bisphenol F, bisphenol S, 4,4'-dihydroxybiphenyl, 9-hydroxyphenanthrene, 9,10-anthraquinone, 1-hydroxypyrene, 9,9-bis(4-hydroxyphenyl)fluorene, and 2,8-dihydroxydibenzothiophene.

[0018] More preferably, the initiator is selected from one or more of 1,6-naphthol, bisphenol A, and 4,4'-dihydroxybiphenyl.

[0019] Preferably, the catalyst is selected from one or more of potassium hydroxide, sodium hydroxide, potassium methoxide, and sodium methoxide.

[0020] Preferably, the reflux dehydration conditions include: reflux dehydration for 2-3 hours at a temperature of 110-120°C until no obvious water droplets are separated from the water separator.

[0021] Preferably, the inert gas is nitrogen and / or argon.

[0022] Preferably, the conditions for the first polymerization reaction include: a temperature of 100~110℃, a reaction pressure of 0.2~0.4 MPa, and a reaction time of 3~5 h.

[0023] Preferably, the block polymerization conditions include: a temperature of 110~120℃, a reaction pressure of 0.3~0.5MPa, and a reaction time of 4~6h.

[0024] Preferably, the conditions for impurity removal include: vacuum distillation for 2-3 hours under vacuum conditions of ≤-0.090 MPa and temperature of 100-110℃.

[0025] Preferably, the antioxidant is selected from one or more of BHT, tris(2,4-di-tert-butylphenyl) phosphite, tris(nonylphenyl) phosphite, and pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate].

[0026] Preferably, in step 2), the mass ratio of the block polyether, phosphorus pentoxide and water is 40:4~6:0.8~1.2.

[0027] Preferably, the esterification reaction conditions include: a rotation speed of 40~60 r / min, a temperature of 80~90℃, and a time of 4~6 h.

[0028] Preferably, the esterification reaction is preheated for 1-2 hours at a rotation speed of 40-60 r / min and a temperature of 50-70°C.

[0029] Preferably, the hydrolysis conditions include a temperature of 75-85°C and a time of 1-2 hours.

[0030] Preferably, the conditions for adjusting the pH of the product include: adjusting the pH to 6.5-7.5 using a sodium hydroxide solution with a mass fraction of 20-40% under the conditions of a rotation speed of 30-50 r / min and a temperature of 40-50°C.

[0031] Preferably, in step 3), the dehydration conditions include: first, purging the air in the dehydration device twice with inert gas, then dehydrating for 2-3 hours at a rotation speed of 20-30 r / min, a temperature of 80-90℃, and a vacuum degree of ≥-0.095 MPa until the product moisture content is ≤0.5%.

[0032] Preferably, the inert gas is nitrogen and / or argon.

[0033] Preferably, the organic polar solvent is selected from one or more of N-methylpyrrolidone, dimethylformamide, dimethylacetamide, dimethyl sulfoxide, and γ-butyrolactone.

[0034] Preferably, the dissolution conditions include: a rotation speed of 40~60 r / min, a temperature of 50~60℃, and a stirring time of 30~60 min.

[0035] Preferably, the solid content of the resulting dispersant and softener is 50%.

[0036] Thirdly, the present invention provides an application of the dispersant and softener described herein in lithium iron phosphate cathode slurry.

[0037] Fourthly, the present invention provides a lithium iron phosphate cathode slurry, wherein the lithium iron phosphate cathode slurry comprises carbon-coated lithium iron phosphate, carbon black, polyvinylidene fluoride, dispersant and softener, and organic polar solvent. The dispersing and softening agent is the dispersing and softening agent described in this invention.

[0038] Preferably, the solid content of the positive electrode slurry is 65-70%.

[0039] Preferably, based on the mass of solid components, the mass fraction of carbon-coated lithium iron phosphate is 96-98 wt%, the mass fraction of carbon black is 0.5-1.5 wt%, the mass fraction of polyvinylidene fluoride is 1-2 wt%, and the mass fraction of dispersant and softener is 0.05-0.3 wt%.

[0040] Fifthly, the present invention provides a lithium iron phosphate positive electrode sheet, comprising a current collector and a positive electrode coating coated on the current collector, wherein the positive electrode coating is formed by coating and rolling the lithium iron phosphate positive electrode slurry as described in claim 9.

[0041] In the above technical solution, the dispersant and softener of the present invention forms a strong π-π stacking adsorption with carbon-coated LFP and carbon black through a conjugated aromatic ring skeleton, achieving targeted and efficient dispersion of carbon-coated LFP particles and carbon black conductive agent. This, combined with multi-point anchoring of phosphate ester groups and steric hindrance and flexible plasticization provided by EO-PO block polyether, significantly inhibits particle agglomeration and efficiently disperses carbon-coated lithium iron phosphate and carbon black, significantly reducing the viscosity of the lithium iron phosphate cathode slurry. At the same solid content, the slurry's output viscosity is reduced by more than 40% compared to traditional systems, filtration time is shortened by more than 50%, and the viscosity rebound rate after 48 hours is ≤41%. This improves the flexibility and interfacial stability of the resulting cathode sheet.

[0042] Meanwhile, the preparation method of the dispersant and softener of the present invention adopts a controllable process of EO followed by PO block polymerization, phosphoric acid esterification, neutralization and dehydration and non-aqueous polar solvent preparation. It has the advantages of readily available raw materials, mild reaction, simple process, high product purity, and suitability for industrial scale-up. It also has excellent compatibility with NMP, PVDF and electrolyte, no risk of migration and precipitation, and is suitable for large-scale application in LFP cathode systems of power batteries and energy storage batteries.

[0043] Furthermore, the positive electrode slurry prepared using the dispersant and softener of this invention maintains low viscosity even with high solids content, exhibits fast filtration speed, low viscosity rebound rate after 48 hours, and excellent processing and coating performance. The polyether segment plasticizing PVDF binder in the dispersant and softener of this invention reduces crystallinity and glass transition temperature, improving the stress distribution within the electrode. The number of times the electrode can be folded increases from the traditional 2 times to 3-4 times, significantly enhancing its resistance to bending, powdering, and brittleness. Moreover, the improved dispersion uniformity results in a denser electrode structure, achieving a compaction density of 2.72-2.77 g / cm³ under the same rolling pressure. 3 Compared to the traditional system, it improves by 0.05~0.10 g / cm³. 3 The conductivity and ion transport pathways are more continuous and smoother, significantly improving the cycle stability and long-term reliability of lithium iron phosphate batteries.

[0044] Other features and advantages of the present invention will be described in detail in the following detailed description section. Attached Figure Description

[0045] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with the following detailed description to explain the invention, but do not constitute a limitation thereof. In the drawings: Figure 1 The image shows the Fourier Transform Infrared (FTIR) spectrum of the dispersant softener prepared in Example 1 of this invention. Detailed Implementation

[0046] The following provides a detailed description of specific embodiments of the present invention. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the scope of the invention.

[0047] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0048] In a first aspect, the present invention provides a dispersing softener having the structure shown in formula (I). , Wherein, X is the core skeleton composed of an initiator containing two or more conjugated aromatic rings and having a functionality of 1 to 3; R1 is a polyether segment and / or a saturated alkane chain; R2 is selected from one or more of the following groups: phosphate ester group, sulfonate group, carbonate group, carboxyl group, and hydrogen atom; n is an integer ≥ 0, and m is an integer from 1 to 3; In this invention, in order to balance steric hindrance and solubility and achieve a balance between low viscosity and high dispersion of the slurry, the number average molecular weight of the dispersant and softener is 300~3000g / mol, preferably 400~2000g / mol.

[0049] In this invention, the initiator is selected from one or more of naphthalene derivatives, bisphenols, biphenyls, phenanthrene derivatives, anthracene derivatives, pyrene derivatives, 9,9-bis(4-hydroxyphenyl)fluorene, and 2,8-dihydroxydibenzothiophene; preferably selected from one or more of 2-naphthol, 1-naphthol, 1,6-naphthodiol, 1,5-naphthodiol, 2,6-naphthodiol, 1,5-naphthodiamine, 1,8-naphthodiamine, bisphenol A, bisphenol F, bisphenol S, 4,4'-dihydroxybiphenyl, 9-hydroxyphenanthrene, 9,10-anthraphenadiol, 1-hydroxypyrene, 9,9-bis(4-hydroxyphenyl)fluorene, and 2,8-dihydroxydibenzothiophene; more preferably selected from one or more of 1,6-naphthodiol, bisphenol A, and 4,4'-dihydroxybiphenyl. The initiator of this invention has a multi-aryl aromatic plane that interacts with the carbon layer on the C-LFP surface and the π electron cloud of graphite in a face-to-face / side-to-side π-π stacking manner. The interaction force is much stronger than van der Waals forces, forming irreversible, multi-point adsorption that firmly "pins" the particle surface and prevents desorption.

[0050] In this invention, the long alkane chains and polyether segments in R1 fully extend in the solvent to form a steric hindrance layer, effectively inhibiting particle agglomeration, reducing slurry viscosity, and improving dispersion uniformity. During electrode forming, the long alkane chains and polyether segments plasticize the polyvinylidene fluoride binder, reducing its crystallinity and glass transition temperature, improving the internal stress distribution of the electrode, enhancing the toughness of the binder film, and improving the electrode's flexibility and interfacial bonding, thereby significantly improving the electrode's resistance to bending, powder shedding, and brittleness. R1 has the structure shown in Formula (II). , Where R3 is -CH2-CH2-, EO is -CH2-CH2-O-, PO is -CH(CH3)-CH2-O-, n1, n2 and n3 are each independent integers ≥0, and 6≤n1+n2+n3≤20; R3, EO and PO are connected by block copolymerization.

[0051] In this invention, in order to achieve hydrophilic-hydrophobic balance, improve slurry stability, and enhance electrode flexibility and interfacial bonding, the molar ratio of EO to PO is 1:0.3~3, and the block arrangement is EO first and then PO.

[0052] Secondly, the present invention provides a method for preparing a dispersing and softening agent as described herein, the method comprising the following steps: 1) Block polyether synthesis: The initiator and catalyst are dehydrated by reflux using a dehydrating agent. Under an inert atmosphere, they undergo a first polymerization reaction with ethylene oxide and a second polymerization reaction with propylene oxide. After removing impurities, an antioxidant is added to obtain block polyether. 2) Phosphorylation reaction: The block polyether is esterified with phosphorus pentoxide, hydrolyzed with water, and the pH of the product is adjusted to obtain the phosphorylated product; 3) Dehydration and solution preparation: The phosphorylated product is dehydrated and then dissolved in an organic polar solvent to obtain a dispersing and softening agent.

[0053] In this invention, in order to quickly remove moisture from the system, avoid moisture damaging the catalyst and triggering side reactions, and ensure controllable polymerization, the dehydrating agent in step 1) is selected from one or more of toluene, xylene, cyclohexane, and n-heptane.

[0054] In this invention, the initiator is selected from one or more of naphthalene derivatives, bisphenols, biphenyls, phenanthrene derivatives, anthracene derivatives, pyrene derivatives, 9,9-bis(4-hydroxyphenyl)fluorene, and 2,8-dihydroxydibenzothiophene; preferably selected from one or more of 2-naphthol, 1-naphthol, 1,6-naphthodiol, 1,5-naphthodiol, 2,6-naphthodiol, 1,5-naphthodiamine, 1,8-naphthodiamine, bisphenol A, bisphenol F, bisphenol S, 4,4'-dihydroxybiphenyl, 9-hydroxyphenanthrene, 9,10-anthraphenadiol, 1-hydroxypyrene, 9,9-bis(4-hydroxyphenyl)fluorene, and 2,8-dihydroxydibenzothiophene; more preferably selected from one or more of 1,6-naphthodiol, bisphenol A, and 4,4'-dihydroxybiphenyl. The initiator of this invention has a multi-aryl aromatic plane that interacts with the carbon layer on the C-LFP surface and the π electron cloud of graphite in a face-to-face / side-to-side π-π stacking manner. The interaction force is much stronger than van der Waals forces, forming irreversible, multi-point adsorption that firmly "pins" the particle surface and prevents desorption.

[0055] In this invention, the catalyst is selected from one or more of potassium hydroxide, sodium hydroxide, potassium methoxide, and sodium methoxide.

[0056] In this invention, the conditions for reflux dehydration include: reflux dehydration for 2-3 hours at a temperature of 110-120°C until no obvious water droplets are separated from the water separator.

[0057] In this invention, the inert gas is nitrogen and / or argon.

[0058] In this invention, the conditions for the first polymerization reaction include: a temperature of 100~110℃, a reaction pressure of 0.2~0.4 MPa, and a reaction time of 3~5 h.

[0059] In this invention, the block polymerization conditions include: a temperature of 110~120℃, a reaction pressure of 0.3~0.5MPa, and a reaction time of 4~6h.

[0060] In this invention, the conditions for impurity removal include: vacuum distillation for 2-3 hours under conditions of vacuum degree ≤ -0.090 MPa and temperature of 100~110℃.

[0061] In this invention, the antioxidant is selected from one or more of BHT, tris(2,4-di-tert-butylphenyl) phosphite, tris(nonylphenyl) phosphite, and pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate].

[0062] In this invention, in step 2), the mass ratio of the block polyether, phosphorus pentoxide and water is 40:4~6:0.8~1.2.

[0063] In this invention, the conditions for the esterification reaction include: a rotation speed of 40~60 r / min, a temperature of 80~90℃, and a time of 4~6 h.

[0064] In this invention, the esterification reaction is preheated for 1 to 2 hours at a rotation speed of 40 to 60 r / min and a temperature of 50 to 70°C.

[0065] In this invention, the hydrolysis conditions include a temperature of 75~85℃ and a time of 1~2h.

[0066] In this invention, the conditions for adjusting the pH of the product include: adjusting the pH to 6.5-7.5 using a sodium hydroxide solution with a mass fraction of 20-40% under the conditions of a rotation speed of 30-50 r / min and a temperature of 40-50℃.

[0067] In this invention, in step 3), the dehydration conditions include: first, purging the air in the dehydration device twice with an inert gas, then dehydrating for 2-3 hours at a rotation speed of 20-30 r / min, a temperature of 80-90℃, and a vacuum degree of ≥-0.095 MPa until the product moisture content is ≤0.5%.

[0068] In this invention, the inert gas is nitrogen and / or argon.

[0069] In this invention, the organic polar solvent is selected from one or more of N-methylpyrrolidone, dimethylformamide, dimethylacetamide, dimethyl sulfoxide, and γ-butyrolactone.

[0070] In this invention, the dissolution conditions include: a rotation speed of 40~60 r / min, a temperature of 50~60℃, and a stirring time of 30~60 min.

[0071] In this invention, the solid content of the obtained dispersant softener is 50%.

[0072] Thirdly, the present invention provides an application of the dispersant and softener described herein in lithium iron phosphate cathode slurry.

[0073] Fourthly, the present invention provides a lithium iron phosphate cathode slurry, wherein the lithium iron phosphate cathode slurry comprises carbon-coated lithium iron phosphate, carbon black, polyvinylidene fluoride, dispersant and softener, and organic polar solvent. The dispersing and softening agent is the dispersing and softening agent described in this invention.

[0074] In this invention, the solid content of the positive electrode slurry is 65-70%.

[0075] In this invention, based on the mass of solid components, the mass fraction of carbon-coated lithium iron phosphate is 96-98 wt%, the mass fraction of carbon black is 0.5-1.5 wt%, the mass fraction of polyvinylidene fluoride is 1-2 wt%, and the mass fraction of dispersant and softener is 0.05-0.3 wt%.

[0076] Fifthly, the present invention provides a lithium iron phosphate positive electrode sheet, comprising a current collector and a positive electrode coating coated on the current collector, wherein the positive electrode coating is formed by coating and rolling the lithium iron phosphate positive electrode slurry as described in claim 9.

[0077] The present invention will be described in detail below through embodiments. Unless otherwise specified, all instruments and materials used in the following embodiments are commercially available products.

[0078] Example 1: Preparation of block polyether phosphate dispersant and softener using 1,6-naphthol as an initiator: (1) Block polyether synthesis: After checking the cleanliness of the polymerization reactor and confirming that there are no residual impurities, add 1.000 kg of 1,6-naphthol, 0.010 kg of KOH and 4.000 kg of toluene in sequence, close the reactor lid and tighten the seal. Turn on the stirrer and adjust the speed to 40 r / min. Purge the air in the reactor with nitrogen three times, with a pressure of 0.1 MPa each time. Hold the pressure for 5 min and then release the air. Turn on the jacket heating and raise the temperature to 115℃. Reflux and dehydrate for 2 hours until no obvious water droplets are separated from the water separator. Stop heating and cool to below 80℃. Under nitrogen protection, the temperature was raised to 105℃, and the pressure inside the reactor was adjusted to 0.3MPa. 1.650kg of EO monomer was slowly introduced through a flow meter, and the introduction rate was controlled to avoid a sudden pressure rise. After the introduction was completed, the temperature and pressure were maintained for 4 hours until the pressure inside the reactor stabilized and dropped to near atmospheric pressure, confirming that the EO polymerization was complete. The temperature was raised to 115℃, and the pressure inside the reactor was adjusted to 0.4MPa. 2.176kg of PO monomer was slowly introduced through a flow meter. After the introduction was completed, the temperature and pressure were maintained for 5 hours until the pressure inside the reactor stabilized and dropped to near atmospheric pressure, confirming that the PO polymerization was complete.

[0079] The vacuum level was adjusted to ≤-0.090MPa by turning on the pressure reducing device, and the temperature was raised to 105℃ to remove toluene solvent and unreacted monomers for 2 hours. After cooling to below 60℃, 0.018kg of antioxidant BHT was added and stirred for 30 minutes until completely dissolved to obtain 1,6-naphthobis(EO3-b-PO3) block polyether (theoretical yield 3.550kg), which was then transferred to a phosphorylation reactor.

[0080] (2) Phosphorylation reaction: Turn on the phosphorylation reactor and adjust the stirring speed to 50 r / min. After confirming that the polyether has been transferred, raise the temperature to 60℃. Add 0.444 kg P2O5 into the reactor in 5 batches, with an interval of 20 min between each batch to avoid local overheating and charring of the material. After the addition is complete, continue stirring for 30 min, raise the temperature to 85℃, and keep the reaction at this temperature for 5 h. During this period, take a sample every 1 h to observe the state of the material (it should be a homogeneous viscous liquid with no obvious particles). Maintaining the temperature at 80℃, add 0.089 kg of deionized water and stir for 1.5 h to complete the phosphorylation reaction. Transfer the phosphorylation product to a neutralization vessel, start stirring and adjust the speed to 40 r / min, and cool to 45℃. Slowly add 0.830 kg of 30% NaOH solution at a dropping rate of 0.05 kg / min, while monitoring the pH value online. After the addition is complete, continue stirring for 30 min to ensure the pH stabilizes at 6.5~7.5, obtaining an aqueous solution of sodium polyether phosphate.

[0081] (3) Dehydration and solution preparation: The above-mentioned sodium polyether phosphate aqueous solution was transferred to a vacuum dehydration device, and a vacuum pump, condenser, and receiving tank were connected. Nitrogen gas was purged twice. The stirring speed was turned on and adjusted to 25 r / min. The temperature was raised to 85℃, and the vacuum degree was adjusted to above -0.095 MPa. Dehydration was carried out for 2.5 h. During this period, the distillation of the condenser was observed. When no obvious water droplets were distilled out, a sample was taken and the moisture content was tested to be ≤0.5%. Dehydration was stopped, and the product was cooled to 55℃. The dehydrated product was transferred to a solution preparation vessel, and the stirring speed was turned on and adjusted to 50 r / min. 4.243 kg NMP was added as a solvent. The temperature was maintained at 55℃, and the mixture was stirred for 45 min until the material was completely dissolved. The system was a light yellow, transparent, and homogeneous liquid with no layering or precipitation. The product of the dispersing softener with a solid content of 50% was obtained and was designated as B1.

[0082] Depend on Figure 1 It can be seen that the characteristic absorption peaks of all designed structures appear in B1, specifically assigned as follows: 3421.92 cm⁻¹ -1 The broad and strong absorption peak at 2877.00 cm⁻¹ is attributed to the stretching vibrations of the polyether chain ends and possibly residual hydroxyl groups (-OH); -1 The absorption peak at 1667.05 cm⁻¹ is attributed to the CH bond stretching vibrations of the methylene (-CH₂-) and methyl (-CH₃) bonds on the ethylene oxide (EO) and propylene oxide (PO) segments in the block polyether; -1 The weak absorption peak at 1506.29 cm⁻¹ originates from the C=O stretching vibration of the amide group in the solvent N-methylpyrrolidone (NMP), confirming that the sample is an NMP solution system; -1 and 1458.51 cm -1 The absorption peak appearing nearby is attributed to the characteristic peak of the C=C stretching vibration of the naphthalene ring skeleton in the initiator 1,6-naphthol, proving the existence of the aromatic ring initiator structure; 1258.21 cm⁻¹ -1 The absorption peak appearing at 1109.04 cm⁻¹ is attributed to the stretching vibration of the P=O bond in the phosphate ester group, confirming a successful phosphorylation reaction; -1 The strong and broad absorption peak at 843.08 cm⁻¹ is attributed to the stretching vibration of the COC ether bond in the block polyether segment and is a characteristic peak of the polyether structure. -1 The absorption peak appearing at [location] is attributed to the out-of-plane bending vibration characteristic peak of the 1,6-disubstituted naphthalene ring, further confirming the core structure of the initiator. FTIR spectroscopy results show that the target product simultaneously contains the designed structure of naphthalene ring, polyether segment, and phosphate ester group, and the functional group composition is consistent with expectations.

[0083] Example 2: Preparation of block polyether phosphate dispersant and softener using 1-naphthol as an initiator: The method of Example 1 was implemented, except that in step (1), “1.000 kg 1,6-naphthol” was replaced with “1.000 kg 1-naphthol”, “0.010 kg KOH” was replaced with “0.011 kg KOH”, “1.650 kg EO monomer” was replaced with “0.917 kg EO monomer”, “2.176 kg PO monomer” was replaced with “1.210 kg PO monomer”, and “0.018 kg antioxidant BHT” was replaced with “0.020 kg antioxidant BHT”. In step (2), replace “0.444 kg P2O5” with “0.490 kg P2O5”, “0.089 kg deionized water” with “0.098 kg deionized water”, and “0.830 kg of 30% NaOH solution” with “0.910 kg of 30% NaOH solution”. Replace “4.243 kg NMP” in step (3) with “4.630 kg NMP”; With all other steps and conditions unchanged, the dispersing softener product is obtained and designated as B2.

[0084] Example 3: Preparation of block polyether phosphate dispersant and softener using bisphenol F as an initiator: The method of Example 1 was implemented, except that in step (1), “1.000 kg 1,6-naphthol” was replaced with “1.000 kg bisphenol F”, “0.010 kg KOH” was replaced with “0.009 kg KOH”, “1.650 kg EO monomer” was replaced with “1.320 kg EO monomer”, “2.176 kg PO monomer” was replaced with “1.740 kg PO monomer”, and “0.018 kg antioxidant BHT” was replaced with “0.016 kg antioxidant BHT”. In step (2), replace “0.444 kg P2O5” with “0.359 kg P2O5”, “0.089 kg deionized water” with “0.072 kg deionized water”, and “0.830 kg of 30% NaOH solution” with “0.675 kg of 30% NaOH solution”. Replace “4.243 kg NMP” in step (3) with “3.530 kg NMP”; With all other steps and conditions unchanged, the dispersing softener product is obtained and designated as B3.

[0085] Example 4: Preparation of block polyether phosphate dispersant and softener using 4,4'-dihydroxybiphenyl as an initiator: The method of Example 1 was implemented, except that in step (1), “1.000 kg 1,6-naphthol” was replaced with “1.000 kg 4,4'-dihydroxybiphenyl”, “1.650 kg EO monomer” was replaced with “1.420 kg EO monomer”, “2.176 kg PO monomer” was replaced with “1.872 kg PO monomer”, and “0.018 kg antioxidant BHT” was replaced with “0.017 kg antioxidant BHT”. In step (2), replace “0.444kg P2O5” with “0.392kg P2O5”, “0.089kg deionized water” with “0.078kg deionized water”, and “0.830kg of 30% NaOH solution” with “0.730kg of 30% NaOH solution”. Replace “4.243 kg NMP” in step (3) with “3.820 kg NMP”; With all other steps and conditions unchanged, the dispersing softener product is obtained and designated as B4.

[0086] Example 5: Preparation of block polyether phosphate dispersant and softener using 1-hydroxypyrene as an initiator: The method of Example 1 was implemented, except that in step (1), “1.000 kg 1,6-naphthol” was replaced with “1.000 kg 1-hydroxypyrene”, “0.010 kg KOH” was replaced with “0.008 kg KOH”, “1.650 kg EO monomer” was replaced with “0.605 kg EO monomer”, “2.176 kg PO monomer” was replaced with “0.799 kg PO monomer”, and “0.018 kg antioxidant BHT” was replaced with “0.015 kg antioxidant BHT”. In step (2), replace “0.444 kg P2O5” with “0.330 kg P2O5”, “0.089 kg deionized water” with “0.066 kg deionized water”, and “0.830 kg of 30% NaOH solution” with “0.620 kg of 30% NaOH solution”. Replace “4.243 kg NMP” in step (3) with “3.310 kg NMP”; With all other steps and conditions unchanged, the dispersing softener product is obtained and designated as B5.

[0087] Example 6: Preparation of block polyether phosphate dispersant and softener using 1,6-naphthol as an initiator: The method of Example 1 was implemented, except that in step (1), “1.000 kg 1,6-naphthol” was replaced with “1.000 kg 1,6-naphthol”, “1.650 kg EO monomer” was replaced with “1.100 kg EO monomer”, and “2.176 kg PO monomer” was replaced with “4.351 kg PO monomer”; all other steps and conditions remained unchanged, and the dispersing softener product was obtained, which was denoted as B6.

[0088] Example 7: Preparation of block polyether phosphate dispersant and softener using 1,6-naphthol as an initiator: The method of Example 6 was implemented, except that "4.351 kg PO monomer" was replaced with "5.802 kg PO monomer"; Replace “4.243 kg NMP” in step (3) with “4.247 kg NMP”; With all other steps and conditions unchanged, the dispersing softener product is obtained and designated as B7.

[0089] Example 8: Preparation of block polyether phosphate dispersant and softener using 1,6-naphthol as an initiator: The method of Example 6 was carried out, except that "1.100 kg EO monomer" was replaced with "3.300 kg EO monomer" and "4.351 kg PO monomer" was replaced with "1.450 kg PO monomer". All other steps and conditions remained unchanged, and the dispersing softener product was obtained, which was denoted as B8.

[0090] Example 9: Preparation of block polyether phosphate dispersant and softener using 1,6-naphthol as an initiator: The method of Example 6 was implemented, except that “1.100kg EO monomer” was replaced with “4.400kg EO monomer”, “4.351kg PO monomer” was replaced with “1.450kg PO monomer”; and “4.243kg NMP” in step (3) was replaced with “4.247 kg NMP”. With all other steps and conditions unchanged, the dispersing softener product is obtained and designated as B9.

[0091] Comparative Example 1: Preparation of dispersing and softening agents using phenol as an initiator: The method of Example 1 was implemented, except that in step (1), “1.000 kg 1,6-naphthol” was replaced with “1.000 kg phenol”, “0.010 kg KOH” was replaced with “0.017 kg KOH”, “1.650 kg EO monomer” was replaced with “1.872 kg EO monomer”, “2.176 kg PO monomer” was replaced with “2.469 kg PO monomer”, and “0.018 kg antioxidant BHT” was replaced with “0.022 kg antioxidant BHT”. In step (2), replace “0.444kg P2O5” with “0.755kg P2O5”, “0.089kg deionized water” with “0.152kg deionized water”, and “0.830kg of 30% NaOH solution” with “1.410kg of 30% NaOH solution”. Replace “4.243kg NMP” in step (3) with “6.508kg NMP”; With all other steps and conditions unchanged, the dispersing softener product is obtained and denoted as D1.

[0092] Comparative Example 2: Preparation of a dispersant and softening agent using 1,2-propanediol as an initiator: The method of Example 1 was implemented, except that in step (1), “1.000 kg 1,6-naphthol” was replaced with “1.000 kg 1,2-propanediol”, “0.010 kg KOH” was replaced with “0.021 kg KOH”, “1.650 kg EO monomer” was replaced with “4.631 kg EO monomer”, “2.176 kg PO monomer” was replaced with “6.106 kg PO monomer”, and “0.018 kg antioxidant BHT” was replaced with “0.038 kg antioxidant BHT”. In step (2), replace “0.444kg P2O5” with “0.934kg P2O5”, “0.089kg deionized water” with “0.188kg deionized water”, and “0.830kg of 30% NaOH solution” with “1.745kg of 30% NaOH solution”. Replace “4.243kg NMP” in step (3) with “8.050kg NMP”; With all other steps and conditions unchanged, the dispersing softener product is obtained and denoted as D2.

[0093] Application Example 1: The dispersants and softeners obtained in Examples 1-12 and Comparative Examples 1-2 were used to prepare lithium iron phosphate cathode slurry and cathode sheets according to the following methods.

[0094] 1. Preparation of lithium iron phosphate cathode slurry: (1) Positive electrode slurry formulation: The mass percentages of each component, based on the total mass of the solid components, are as follows: Carbon-coated lithium iron phosphate: 97.45% Carbon black (Super P): 1% Polyvinylidene fluoride (PVDF): 1.5% Dispersant and softener: 0.05% The slurry solids content is controlled at 68.5%, and the solvent is N-methylpyrrolidone (NMP).

[0095] (2) Preparation steps of positive electrode slurry: S1. Dry mixing: Weigh carbon-coated lithium iron phosphate, carbon black and PVDF according to the formula ratio, add them to a planetary mixer, and stir at 800 r / min for 20 min to make the powder materials initially mixed evenly.

[0096] S2. High-speed dispersion: Add NMP solvent and the dispersing and softening agents prepared in Examples 1-12 and Comparative Examples 1-2 to the above dry mixture, respectively. Start stirring and disperse at 2000 r / min for 180 min. During the dispersion process, turn on the vacuum system and introduce cooling water to control the slurry temperature to not exceed 50°C to ensure complete degassing.

[0097] S3. Slurry filtration: After dispersion, the slurry is filtered through a 200-mesh filter to remove any undispersed agglomerates and impurities, resulting in a uniform and stable positive electrode slurry.

[0098] 2. Preparation of positive electrode sheet: (1) Coating: The positive electrode slurry prepared above is uniformly coated onto an aluminum foil current collector with a thickness of 15 μm. During the coating process, the coating surface density is controlled to be 260 g / m². 2 The temperature of the coating machine oven is set to 100℃ to ensure that the weight loss rate of the electrode sheet is ≤0.3%.

[0099] (2) Roller pressing: The dried electrode sheets are cold-pressed using a roller press with fixed roller gap and pressure to ensure consistent test conditions.

[0100] Application Example 2: The method of Application Example 1 was followed, except that the dispersant and softening agent prepared in Example 1 was used, and the positive electrode slurry was prepared according to the following formulation. Other steps remained unchanged, and a positive electrode slurry and a positive electrode sheet were obtained.

[0101] The mass percentages of each component, based on the total mass of the solid components, are as follows: Carbon-coated lithium iron phosphate: 97.47% Carbon black (Super P): 1% Polyvinylidene fluoride (PVDF): 1.5% Dispersant and softener: 0.03% The slurry solids content is controlled at 68.5%, and the solvent is N-methylpyrrolidone (NMP).

[0102] Application Example 3: The method of Application Example 1 was followed, except that the dispersant and softening agent prepared in Example 1 was used, and the positive electrode slurry was prepared according to the following formulation. Other steps remained unchanged, and a positive electrode slurry and a positive electrode sheet were obtained.

[0103] The mass percentages of each component, based on the total mass of the solid components, are as follows: Carbon-coated lithium iron phosphate: 97.3% Carbon black (Super P): 1% Polyvinylidene fluoride (PVDF): 1.5% Dispersant and softener: 0.2% The slurry solids content is controlled at 68.5%, and the solvent is N-methylpyrrolidone (NMP).

[0104] Application Example 4: The method of Application Example 1 was followed, except that the dispersant and softening agent prepared in Example 1 was used, and the positive electrode slurry was prepared according to the following formulation. Other steps remained unchanged, and a positive electrode slurry and a positive electrode sheet were obtained.

[0105] The mass percentages of each component, based on the total mass of the solid components, are as follows: Carbon-coated lithium iron phosphate: 97.2% Carbon black (Super P): 1% Polyvinylidene fluoride (PVDF): 1.5% Dispersant and softener: 0.3% The slurry solids content is controlled at 68.5%, and the solvent is N-methylpyrrolidone (NMP).

[0106] Test Example 1: Performance tests were conducted on each group of positive electrode slurry and electrode sheets prepared corresponding to Test Examples 1-3. The test methods are as follows: • Slurry filterability test: Take 500 g of slurry, fold a 200 mesh filter into a triangular funnel shape and filter it. Pour the slurry in all at once and record the time required to filter out 300 mL of slurry.

[0107] • Slurry viscosity test: Use a rotational viscometer with a No. 12 rotor to measure the initial viscosity of the slurry at 25°C for 2 minutes and record the readings.

[0108] • Slurry viscosity rebound rate test: After testing the initial viscosity of the slurry, seal it and let it stand at 25°C for 48 hours. Then test the viscosity again using the same method and calculate the viscosity rebound rate. Viscosity rebound rate = (48h viscosity - initial viscosity) / initial viscosity × 100%; • Electrode flexibility test: Cut the positive electrode sheet prepared in Application Example 1 into a rectangular sample of 20 cm × 5 cm. Fold the electrode sheet along the length direction so that the two long sides are aligned. Place it on the test platform and roll it once with a 2 kg cylindrical roller along the direction perpendicular to the indentation. Observe the crease against the light. If it is not transparent, fold it in the opposite direction and repeat. Repeat the operation until the crease is transparent or a break occurs. Record the actual number of folds and take the average value of multiple tests as the evaluation index. Among them, the sample size is ≥4 pieces, and the positive electrode must be selected with no defects in appearance and small thickness fluctuations. The compaction density of the electrode is 2.75 g / cm³. 3 .

[0109] • Electrode compressibility test: Under the same coating weight, the positive electrode sheet prepared in Application Example 1 was cut into rectangular samples of 100cm × 40cm, rolled under a fixed pressure of 6t, and the electrode thickness was tested. The compaction density was calculated according to the following formula: Compacted density = surface density (mg / cm³) 2 ) / Electrode thickness (μm).

[0110] The test results are shown in Table 1.

[0111] Table 1

[0112] As can be seen from the above content and the data in Table 1, the dispersing and softening agents prepared in Examples 1-9 of this invention can significantly reduce slurry viscosity, shorten filtration time, and reduce viscosity rebound rate. Their dispersion effect is far superior to the monobenzene ring dispersing and softening agent in Comparative Example 1 and the acyclic structure dispersing and softening agent prepared in Comparative Example 2. Among them, the EO / PO ratio of 1:1 in Examples 1-5 and 10-12 shows the optimal hydrophilic-hydrophobic balance and the best dispersion and softening effects. The positive electrode sheet containing the dispersing and softening agents prepared in Examples 1-12 of this invention has an increased folding frequency of 3-4 times and a significantly improved compaction density, achieving synergistic optimization of dispersion and softening. As can be seen from the above, the dispersant and softening agent provided by this invention exhibits excellent dispersing performance and softening effect in lithium iron phosphate cathode slurry. The dispersant and softening agents prepared in Examples 1-9 of this invention all contain two or more conjugated aromatic ring structures in their initiator core framework. Through π-π stacking, they form a strong adsorption anchor with carbon-coated lithium iron phosphate and carbon black particles. Simultaneously, the polyether segments fully extend in the solvent, forming steric hindrance, effectively inhibiting particle agglomeration. As can be seen from the test results in Table 1: Regarding dispersion performance, the initial viscosity of the slurries in Examples 1-9, which incorporated the dispersant and softener of this invention, was significantly lower than that in the comparative examples. Specifically, the initial viscosity of Example 1 was only 6321 mPa·s, while the initial viscosity of the dispersant and softener in Comparative Example 1, which used phenol as an initiator and had a single benzene ring structure, was 12008 mPa·s. The initial viscosity of the dispersant and softener in Comparative Example 2, which used propylene glycol as an initiator and had no aromatic ring structure, was as high as 16246 mPa·s. This indicates that initiator structures containing two or more conjugated aromatic rings can achieve efficient adsorption and dispersion of carbon-coated lithium iron phosphate and carbon black particles through stronger π-π stacking interactions. Furthermore, the filtration time of the slurries in Examples 1-9, at 33-49 s, was significantly shorter than the filtration time of 73 s in Comparative Example 1 and 102 s in Comparative Example 2, further demonstrating the improving effect of the dispersant and softener of this invention on the dispersibility and flowability of the slurry.

[0113] Regarding viscosity stability, the viscosity rebound rates of the slurries in Examples 1-9 after 48 hours were generally lower than those in the comparative examples. The viscosity rebound rate of Example 1 was only 20%, while that of Comparative Example 1 was 70%, and that of Comparative Example 2 was as high as 110%. This indicates that the dispersant and softener of the present invention can effectively maintain the dispersed state of particles and inhibit agglomeration rebound during slurry storage, which is beneficial to the stability and consistency of the coating process.

[0114] Regarding electrode flexibility, the electrodes in Examples 1-9, which incorporated the dispersing and softening agent of this invention, generally achieved 3-4 folds, while Comparative Examples 1 and 2 only achieved 2 folds. In Application Example 1, the positive electrode sheets prepared using Examples 3, 4, 5, 8, and 9, and in Application Examples 3-4, the positive electrode sheets prepared using Example 1, achieved 4 folds, demonstrating excellent flexibility. This is because the polyether segments can plasticize the PVDF binder during electrode molding, reducing its crystallinity and glass transition temperature, improving the internal stress distribution of the electrode, and thus significantly enhancing the electrode's bending resistance.

[0115] Regarding the compressibility of the electrode, the positive electrode containing the dispersant and softening agent of Examples 1-9 had a compaction density of 2.71~2.77 g / cm³ under a fixed pressure of 6t. 3 The compaction density of the positive electrode sheet containing the dispersant and softening agent of Comparative Example 1 is generally higher than that of the positive electrode sheet containing 2.68 g / cm³. 3 The positive electrode sheet containing the dispersant and softener of Comparative Example 2 was 2.67 g / cm³. 3 This indicates that the dispersant and softener of the present invention can improve the packing state of solid particles in the slurry, obtain higher compaction density during the rolling process, and thus improve the volumetric energy density of the battery.

[0116] Furthermore, comparing different structural parameters, the dispersant and softening agent of Example 1, which uses 1,6-naphthol as an initiator, has a bis-naphthyl ring structure; the dispersant and softening agent of Example 3, which uses bisphenol F as an initiator, has a bis-benzene ring structure; and the dispersant and softening agent of Example 4, which uses 4,4'-dihydroxybiphenyl as an initiator, has a biphenyl ring structure. Their dispersing performance and flexibility are significantly better than those of the dispersant and softening agent of Comparative Example 1, which uses phenol as an initiator and has a single-benzene ring structure, and the dispersant and softening agent of Comparative Example 2, which has no aromatic ring structure. This indicates that the more conjugated aromatic rings there are, the larger the conjugated system is, the stronger the π-π stacking effect is, and the better the dispersing performance and interfacial stability are.

[0117] Meanwhile, the slurry prepared with EO / PO ratio of 1:1 in Example 1 had the lowest initial viscosity of 6321 mPa·s, the lowest viscosity rebound rate of 20%, and the lowest folding time of 3 times. The initial viscosities of the slurries prepared with EO / PO ratio of 3:1 in Example 8 and 1:3 in Example 6 were 6813 mPa·s and 7737 mPa·s, respectively, both superior to those of Comparative Examples 1-2. This indicates that when the EO to PO ratio is 1:1, the hydrophilic-hydrophobic balance is optimal, and the steric hindrance effect and solvent compatibility achieve synergistic optimality.

[0118] The dispersant and softener prepared in Example 1 has a n1+n2+n3=6 ratio, therefore the initial viscosity of the resulting slurry is the lowest at 6321 mPa·s. As the chain segments increase, the initial viscosities of the slurries prepared with the dispersant and softener prepared in Example 6 (n1+n2+n3=12) and Example 7 (n1+n2+n3=15) increase to 7737 mPa·s and 8973 mPa·s, respectively. This indicates that when the polyether chain segments are too short, there is insufficient steric hindrance, and when the chain segments are too long, molecular chain entanglement easily occurs, leading to an increase in viscosity. Therefore, the viscosity needs to be controlled within a suitable range.

[0119] In summary, the dispersant and softener of this invention combines strong adsorption and dispersion capabilities with electrode softening effects. When applied to lithium iron phosphate cathode slurry, the slurry viscosity at the point of shipment is reduced by more than 40% compared to traditional systems at the same solid content, filtration time is shortened by more than 50%, and the viscosity rebound rate after 48 hours is ≤41%. The number of electrode folds is increased from the traditional 2 times to 3-4 times, significantly enhancing resistance to bending, powder shedding, and brittleness. Under the same rolling pressure, the compaction density can reach 2.72-2.77 g / cm³. 3 This represents an improvement of 0.05~0.10 g / cm³ compared to the traditional system. 3 Meanwhile, the dispersant and softening agent of this invention exhibits excellent compatibility with NMP, PVDF, and electrolytes, with no risk of migration or precipitation, making it suitable for large-scale application in LFP cathode systems for power batteries and energy storage batteries.

[0120] Meanwhile, the preparation method of the dispersant and softener of the present invention adopts a controllable process of EO followed by PO block polymerization, phosphoric acid esterification, neutralization and dehydration and preparation with non-aqueous polar solvent. It has the advantages of readily available raw materials, mild reaction, simple process, high product purity and suitability for industrial scale-up.

[0121] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

[0122] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

[0123] Furthermore, various different embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed by the present invention.

Claims

1. A dispersing and softening agent, characterized in that, The dispersant and softening agent has the structure shown in formula (I). ， Wherein, X is the core skeleton composed of an initiator containing two or more conjugated aromatic rings and having a functionality of 1 to 3; R1 is a polyether segment and / or a saturated alkane chain; R2 is selected from one or more of the following groups: phosphate ester group, sulfonate group, carbonate group, carboxyl group, and hydrogen atom; n is an integer ≥ 0, and m is an integer from 1 to 3; The number average molecular weight of the dispersant and softener is 300~3000 g / mol.

2. The dispersant and softening agent according to claim 1, characterized in that, The initiator is selected from one or more of the following: naphthalene derivatives, bisphenols, biphenyls, phenanthrene derivatives, anthracene derivatives, pyrene derivatives, 9,9-bis(4-hydroxyphenyl)fluorene, and 2,8-dihydroxydibenzothiophene. Preferably, the initiator is selected from one or more of 2-naphthol, 1-naphthol, 1,6-naphthodiol, 1,5-naphthodiol, 2,6-naphthodiol, 1,5-naphthodiamine, 1,8-naphthodiamine, bisphenol A, bisphenol F, bisphenol S, 4,4'-dihydroxybiphenyl, 9-hydroxyphenanthrene, 9,10-anthraquinone, 1-hydroxypyrene, 9,9-bis(4-hydroxyphenyl)fluorene, and 2,8-dihydroxydibenzothiophene. More preferably, the initiator is selected from one or more of 1,6-naphthol, bisphenol A, and 4,4'-dihydroxybiphenyl.

3. The dispersing and softening agent according to claim 1 or 2, characterized in that, R1 has the structure shown in formula (Ⅱ), ， Where R3 is -CH2-CH2-, EO is -CH2-CH2-O-, PO is -CH(CH3)-CH2-O-, n1, n2 and n3 are each independent integers ≥0, and 6≤n1+n2+n3≤20; R3, EO and PO are connected by block copolymerization; Preferably, the molar ratio of EO to PO is 1:0.3~3, and the block arrangement is EO first, then PO; Preferably, the number average molecular weight of the dispersant and softener is 400~2000 g / mol.

4. A method for preparing the dispersing and softening agent as described in any one of claims 1-3, characterized in that, The preparation method includes the following steps: 1) Block polyether synthesis: The initiator and catalyst are dehydrated by reflux using a dehydrating agent. Under an inert atmosphere, they undergo a first polymerization reaction with ethylene oxide and a second polymerization reaction with propylene oxide. After removing impurities, an antioxidant is added to obtain block polyether. 2) Phosphorylation reaction: The block polyether is esterified with phosphorus pentoxide, hydrolyzed with water, and the pH of the product is adjusted to obtain the phosphorylated product; 3) Dehydration and solution preparation: The phosphorylated product is dehydrated and then dissolved in an organic polar solvent to obtain a dispersing and softening agent.

5. The preparation method according to claim 4, characterized in that, In step 1), the dehydrating agent is selected from one or more of toluene, xylene, cyclohexane, and n-heptane; The initiator is selected from one or more of the following: naphthalene derivatives, bisphenols, biphenyls, phenanthrene derivatives, anthracene derivatives, pyrene derivatives, 9,9-bis(4-hydroxyphenyl)fluorene, and 2,8-dihydroxydibenzothiophene. Preferably, the initiator is selected from one or more of 2-naphthol, 1-naphthol, 1,6-naphthodiol, 1,5-naphthodiol, 2,6-naphthodiol, 1,5-naphthodiamine, 1,8-naphthodiamine, bisphenol A, bisphenol F, bisphenol S, 4,4'-dihydroxybiphenyl, 9-hydroxyphenanthrene, 9,10-anthraquinone, 1-hydroxypyrene, 9,9-bis(4-hydroxyphenyl)fluorene, and 2,8-dihydroxydibenzothiophene. More preferably, the initiator is selected from one or more of 1,6-naphthol, bisphenol A, and 4,4'-dihydroxybiphenyl; The catalyst is selected from one or more of potassium hydroxide, sodium hydroxide, potassium methoxide, and sodium methoxide. The conditions for reflux dehydration include: reflux dehydration for 2-3 hours at a temperature of 110-120℃ until no obvious water droplets are separated from the water separator; The inert gas is nitrogen and / or argon; The conditions for the first polymerization reaction include: a temperature of 100~110℃, a reaction pressure of 0.2~0.4 MPa, and a reaction time of 3~5 h; The block polymerization conditions include: a temperature of 110~120℃, a reaction pressure of 0.3~0.5MPa, and a reaction time of 4~6h; The conditions for impurity removal include: vacuum distillation for 2-3 hours at a vacuum degree ≤ -0.090 MPa and a temperature of 100~110℃; The antioxidant is selected from one or more of BHT, tris(2,4-di-tert-butylphenyl) phosphite, tris(nonylphenyl) phosphite, pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], and tris(2,4-di-tert-butylphenyl) phosphite.

6. The preparation method according to claim 4 or 5, characterized in that, In step 2), the mass ratio of the block polyether, phosphorus pentoxide, and water is 40:4~6:0.8~1.2; The conditions for the esterification reaction include: rotation speed of 40~60 r / min, temperature of 80~90℃, and time of 4~6 h; Before the esterification reaction, the mixture should be preheated for 1-2 hours at a speed of 40-60 r / min and a temperature of 50-70℃. The hydrolysis conditions include: a temperature of 75~85℃ and a time of 1~2h; The conditions for adjusting the pH of the product include: adjusting the pH to 6.5-7.5 using a sodium hydroxide solution with a mass fraction of 20-40% under the conditions of a rotation speed of 30-50 r / min and a temperature of 40-50℃.

7. The preparation method according to any one of claims 4-6, characterized in that, In step 3), the dehydration conditions include: first, purging the air in the dehydration device twice with inert gas; then, dehydrating for 2-3 hours at a rotation speed of 20-30 r / min, a temperature of 80-90℃, and a vacuum degree ≥-0.095 MPa, until the product moisture content is ≤0.5%. Preferably, the inert gas is nitrogen and / or argon; The organic polar solvent is selected from one or more of N-methylpyrrolidone, dimethylformamide (DMF), dimethylacetamide (DMAC), dimethyl sulfoxide (DMSO), and γ-butyrolactone (GBL); The dissolution conditions include: a rotation speed of 40~60 r / min, a temperature of 50~60℃, and a stirring time of 30~60 min; The solid content of the resulting dispersant and softener is 50%.

8. The application of the dispersant and softener as described in any one of claims 1-3 in lithium iron phosphate cathode slurry.

9. A lithium iron phosphate cathode slurry, characterized in that, The lithium iron phosphate cathode slurry comprises carbon-coated lithium iron phosphate, carbon black, polyvinylidene fluoride, dispersant and softener, and organic polar solvent. Wherein, the dispersing and softening agent is any one of the dispersing and softening agents according to claims 1-3; The solid content of the positive electrode slurry is 65-70%; Based on the mass of solid components, the mass fraction of carbon-coated lithium iron phosphate is 96~98wt%, the mass fraction of carbon black is 0.5~1.5wt%, the mass fraction of polyvinylidene fluoride is 1~2wt%, and the mass fraction of dispersant and softener is 0.05~0.3wt%.

10. A lithium iron phosphate positive electrode, characterized in that, It includes a current collector and a positive electrode coating coated on the current collector, the positive electrode coating being formed by coating and rolling the lithium iron phosphate positive electrode slurry as described in claim 9.

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