Lithium iron phosphate composite material, preparation method and application thereof
By ultrasonic treatment and polyanionic cellulose salt modification of the lithium iron phosphate surface, combined with in-situ polymerization of PEDOT/PSS, the problems of low conductivity and interfacial compatibility of lithium iron phosphate materials were solved, achieving high-efficiency conductivity and improved cycle stability.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- QINGDAO UNIV OF SCI & TECH
- Filing Date
- 2026-03-30
- Publication Date
- 2026-06-09
AI Technical Summary
Lithium iron phosphate materials have low ionic conductivity and poor cycle performance, and the conductive polymer binder PEDOT/PSS has poor interfacial compatibility with them, resulting in poor adhesion.
The surface of lithium iron phosphate was pre-modified with ultrasound-assisted polyanionic cellulose salt, and then PEDOT/PSS was synthesized on its surface. A mixture of sodium carboxymethyl cellulose and lithium was used as a modifier, combined with stearate dispersant and peroxy acid catalyst, to carry out in-situ polymerization to form a stable composite material.
It significantly improves the conductivity and cycle stability of lithium iron phosphate, reduces resistivity by 84%, and improves cycle performance to 98.73%, making it suitable for industrial production.
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Figure CN122177797A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of lithium-ion battery cathode material technology, specifically relating to a lithium iron phosphate composite material modified in situ by a conductive polymer, its preparation method, and its application. Background Technology
[0002] Lithium iron phosphate (LiFePO4, LFP) is a common cathode material for lithium batteries. It has advantages such as high safety, strong stability and low price, and is therefore widely used in electric vehicles and energy storage systems.
[0003] Lithium iron phosphate has a unique crystal lattice structure. While this structure brings many advantages, it also introduces some unavoidable drawbacks, such as the fact that Li... + The diffusion channels in its lattice are strictly limited, allowing diffusion only in the (010) direction. Furthermore, the distortion of these diffusion channels is exacerbated by the truncation of the FeO6 octahedrons by the PO4 tetrahedra. + The diffusion difficulty is further increased, which ultimately leads to poor electrochemical performance of lithium iron phosphate, and the problem of performance degradation is also common.
[0004] In recent years, conductive polymer binders have received increasing attention, and their introduction into lithium iron phosphate materials has become an effective means to improve their electrochemical performance. As an intermediate material that tightly bonds the electrode material to the current collector, the conductive polymer binder ensures the mechanical and electronic integrity of the electrode, prevents the separation of the active material during lithium insertion / extraction, and thus helps to improve the electrode's lifespan.
[0005] PEDOT / PSS is a water-soluble composite conductive polymer composed of the conductive monomer PEDOT and the dopant polystyrene sulfonic acid PSS. Due to its high conductivity and good film-forming properties, it has become a popular choice for conductive polymer binders. For example, patent CN118104011A describes a method of coating the positive electrode matrix material using an ion-conductive polymer and PEDOT:PSS crosslinking; patent CN109721713A describes a gel-like polymer generated through polymerization and PEDOT-PSS doped with composite activated carbon; and patent CN108400334A describes coating the electrode sheet with PEDOT:PSS as a binder, etc., to improve the electrochemical performance of the positive electrode material. However, because the surface of lithium iron phosphate particles is highly inorganically polar, and the PEDOT / PSS molecular chain has a special structure with a hydrophobic framework and hydrophilic sulfonic acid groups, the interfacial compatibility between the two is extremely poor.
[0006] Therefore, developing a modification strategy that can enhance the interfacial bonding between PEDOT / PSS and lithium iron phosphate and improve coating stability has become a key issue that urgently needs to be addressed in the field of lithium-ion battery cathode materials. This is of great practical significance for promoting the performance upgrade of lithium iron phosphate electrodes and expanding their application in power batteries and energy storage. Summary of the Invention
[0007] To address the issues of low ionic conductivity and poor cycle performance of lithium iron phosphate (LFP) as the positive electrode material in lithium-ion batteries, as well as the problem of poor adhesion when modifying LFP with conductive polymer binder PEDOT / PSS, a lithium iron phosphate composite material specifically for lithium battery positive electrodes is proposed, along with its preparation method and application.
[0008] In this invention, conductive polymer binder PEDOT / PSS is used to modify lithium iron phosphate. However, PEDOT / PSS has a linear structure and is typically used at low concentrations, resulting in weak adhesion. Therefore, without modifying or treating the lithium iron phosphate, directly loading the binder does not significantly improve conductivity. Based on this, the inventors first used ultrasound-assisted polyanionic cellulose salt to pre-modify the surface of lithium iron phosphate. Ultrasonic treatment was used to adjust its adhesion to lithium iron phosphate. Simultaneously, using this as a substrate, PEDOT / PSS was directly synthesized on its surface. This process exhibits higher stability and a more significant improvement in conductivity compared to the physical adhesion of PEDOT / PSS.
[0009] The technical solution provided by this invention is as follows:
[0010] The first aspect of this invention is to provide a method for preparing a lithium iron phosphate composite material, specifically comprising the following steps:
[0011] Surface modification of S1 lithium iron phosphate: Polyanionic cellulose salt is dissolved in an organic solvent system, lithium iron phosphate powder is added, and the surface of lithium iron phosphate powder is modified under ultrasonic conditions to obtain surface-modified lithium iron phosphate powder.
[0012] The polyanionic cellulose salt is selected from at least one of sodium carboxymethyl cellulose, potassium carboxymethyl cellulose, lithium carboxymethyl cellulose, and ammonium carboxymethyl cellulose.
[0013] The organic solvent system is a mixture of alcohols and carbonate reagents, wherein the volume fraction of alcohols is 5% to 20%.
[0014] The mass ratio of lithium iron phosphate powder to polyanionic cellulose salt is 5~15:1, preferably 8~12:1, and more preferably 10:1;
[0015] Loading of S2 binder: PEDOT / PSS is used as a binder and loaded onto the surface-modified lithium iron phosphate powder in S1 to obtain the lithium iron phosphate composite material.
[0016] In the preparation method of the above-mentioned lithium iron phosphate composite material provided by the present invention, preferably, in S1, the polyanionic cellulose salt is a mixture of sodium carboxymethyl cellulose and lithium carboxymethyl cellulose; more preferably, the mass ratio of sodium carboxymethyl cellulose to lithium carboxymethyl cellulose is 1:1 to 5; and most preferably, the mass ratio of sodium carboxymethyl cellulose to lithium carboxymethyl cellulose is 1:4.
[0017] Preferably, the volume fraction of alcohols in the organic solvent system in S1 is 10%, and the alcohols are selected from at least one of methanol, ethanol, and glycols; the carbonates are selected from at least one of dimethyl carbonate (DMC), diethyl carbonate (DEC), and ethylene carbonate (EC). This is because an appropriate concentration of alcohols is beneficial for promoting the dispersion of stearate dispersants and coupling agents, while too much will affect the conductivity of lithium iron phosphate.
[0018] Preferably, in S1, the ultrasonic conditions are: ultrasonic power 120~200 W, ultrasonic duration 20~40 min; more preferably, the ultrasonic power is 200 W and the ultrasonic duration is 30 min.
[0019] The inventors discovered that the degree of ultrasonic treatment directly determines the degree of bonding of polyanionic cellulose salts to the surface of lithium iron phosphate, thus affecting the bonding effect of PEDOT / PSS. The composite material with the best conductivity was obtained when the ultrasonic frequency was 200 W and the time was 30 min. Meanwhile, the type and ratio of polyanionic cellulose salts are also crucial, directly determining the conductivity of the lithium iron phosphate composite material. When the mass of the mixture is fixed, the higher the proportion of CMC-Na, the worse the conductivity of the resulting composite material. Only when the polyanionic cellulose salts are CMC-Na and CMC-Li, and their mass ratio is 1:4, does the obtained composite material exhibit the best conductivity and cycling performance.
[0020] Preferably, the loading of the binder in S2 is specifically carried out as follows: the surface-modified lithium iron phosphate powder is added to the same organic solvent system as in S1, then a dispersant and a coupling agent are added, the mixture is stirred evenly and ultrasonically treated for 3 to 10 minutes, and finally the conductive polymer monomer EDOT, peroxy acid and sodium polystyrene sulfonate are added. The mixture is stirred and polymerized at 50 to 70°C, preferably 60°C. After the reaction is completed, the solvent is removed and the mixture is vacuum dried at 50 to 80°C to obtain the lithium iron phosphate composite material.
[0021] The dispersant is selected from at least one of polyglycerol monostearate and polyoxyethylene stearate, more preferably polyglycerol monostearate;
[0022] The coupling agent is selected from at least one of 3-aminopropylmethyldimethylsilane and 3-methacryloyloxypropyltrimethoxysilane, more preferably 3-aminopropylmethyldimethylsilane;
[0023] The peroxy acid is selected from either peroxyformic acid or peracetic acid, and more preferably 20% peroxyformic acid.
[0024] Preferably, in S2, the mass ratio of the dispersant to lithium iron phosphate powder is 0.01~0.05:1, the mass ratio of the coupling agent to lithium iron phosphate powder is 0.01~0.1:1, and the molar ratio of the conductive polymer monomer EDOT: peroxy acid: sodium polystyrene sulfonate is 1:0.5~0.8:0.8~1.2.
[0025] A second aspect of the present invention is to provide a lithium iron phosphate composite material, wherein the lithium iron phosphate composite material is specifically prepared by the preparation method described above.
[0026] A third aspect of the present invention is the application of the lithium iron phosphate composite material in a battery, specifically, the lithium iron phosphate composite material is used as a positive electrode material in a lithium battery. Naturally, lithium-ion battery products containing the lithium iron phosphate composite material also fall within the protection scope of the present invention.
[0027] The present invention has the following advantages and effects compared with the prior art:
[0028] This invention first uses a carboxymethyl cellulose (CMC) mixture to encapsulate and modify the surface of lithium iron phosphate (LFP) powder in an organic solvent system. Then, using this as a matrix, stearate surfactants as dispersants, and oxyacids such as peroxyformic acid as catalysts, an in-situ catalytic reaction is carried out to directly generate a PEDOT / PSS polymer on the surface-modified LFP surface, ultimately obtaining a PEDOT / PSS-modified LFP composite electrode material. Experimental results show that when the mass ratio of CMC-Na to CMC-Li in the CMC material is 1:4, the resistivity of the obtained composite material is optimal. Depending on the type of catalyst, the resistivity ranges from 3.18 to 5.76 Ω·cm, which is about 84% lower than the resistivity of the material modified with a single sodium / lithium CMC material (20.2 Ω·cm / 14.43 Ω·cm), indicating a significant improvement in conductivity. When the mass ratio of CMC-Na in the CMC material increases, the conductivity of the obtained composite material decreases to some extent.
[0029] Furthermore, the modification method for positive electrode materials provided by this invention has simple steps, easy temperature control, and produces a uniform particle size of the resulting powder, which is suitable for industrial-scale production. Attached Figure Description
[0030] Figure 1 This is a projection electron microscope image of the lithium iron phosphate composite material prepared in Example 1 of the present invention;
[0031] Figure 2 This is a particle size distribution diagram of the lithium iron phosphate composite material prepared in Example 1 of the present invention;
[0032] Figure 3 The graph shows the change in specific capacity of lithium iron phosphate composite materials prepared by each experimental group of this invention during battery cycle discharge.
[0033] Figure 4 The graph shows the change in capacitance retention rate of the lithium iron phosphate composite materials prepared by each experimental group of this invention during battery cycle discharge. Detailed Implementation
[0034] To enable those skilled in the art to better understand the present invention, the present invention will now be further described in conjunction with specific embodiments.
[0035] Example 1
[0036] A lithium iron phosphate composite material is prepared by the following method:
[0037] Surface modification of S1 lithium iron phosphate: 0.1 g sodium carboxymethyl cellulose (CMC-Na) and 0.4 g lithium carboxymethyl cellulose (CMC-Li) were mixed and added to 50 mL of dimethyl carbonate system containing methanol (volume fraction of methanol was 10%). Then 5 g lithium iron phosphate powder was added to the mixture. The mixture was ultrasonically mixed for 30 min at an ultrasonic power of 200 W. After filtration, the mixture was vacuum dried at 60 °C for 6 h to obtain surface-modified lithium iron phosphate powder.
[0038] Loading of S2 binder: The surface-modified lithium iron phosphate powder obtained in S1 was added to 80 mL of dimethyl carbonate system containing 10% methanol, 0.15 g of triglyceride monostearate and 0.25 g of 3-aminopropylmethyldimethylsilane coupling agent were added, stirred evenly, and ultrasonically treated for 5 min with an ultrasonic power of 200 W. Then, 1.42 g of conductive polymer monomer EDOT, 18.5 g of 20% peroxyformic acid and 1.7 g of sodium polystyrene sulfonate were added, and the mixture was stirred at 60 °C for 6 h to carry out the polymerization reaction. After the reaction was completed, the solvent was removed, and the mixture was vacuum dried at 60 °C for 12 h to obtain the lithium iron phosphate composite material.
[0039] The lithium iron phosphate composite material prepared in this embodiment was characterized using transmission electron microscopy (TEM), and the results are as follows: Figure 1 As shown in the figure, the particle size of the lithium iron phosphate composite material is relatively uniform.
[0040] The composite material was characterized using a laser particle size analyzer, and the particle size distribution results are as follows: Figure 2 As shown in the figure, the D50 of the prepared lithium iron phosphate composite material is 0.493 μm. Combined with the TEM image, it is further proved that after surface pretreatment, the secondary agglomeration of LFP particles was effectively prevented during the synthesis of the composite material under the action of dispersants and coupling agents, which is beneficial to improving the conductivity of the composite material.
[0041] Example 2
[0042] A lithium iron phosphate composite material is prepared by the following method:
[0043] S1 is the same as in Example 1;
[0044] Loading of S2 binder: The surface-modified lithium iron phosphate powder obtained in S1 was added to 80 mL of dimethyl carbonate system containing 10% methanol, 0.15 g of triglyceride monostearate and 0.25 g of 3-aminopropylmethyldimethylsilane coupling agent were added, stirred evenly, and ultrasonically treated for 5 min at 200 W. Then, 1.42 g of conductive polymer monomer EDOT, 18.5 g of 20% peracetic acid and 1.7 g of sodium polystyrene sulfonate were added. The polymerization reaction was carried out at 60 °C for 6 h. After the reaction was completed, the solvent was removed and the mixture was vacuum dried at 60 °C for 12 h to obtain the lithium iron phosphate composite material.
[0045] Example 3
[0046] The difference from Example 1 is that the power of the ultrasonic treatment in S1 is 120W.
[0047] Example 4
[0048] The difference from Example 1 is that the mass ratio of CMC-Na:CMC-Li in S1 has been adjusted, as shown in Table 1 below.
[0049] Table 1. Mass ratio of carboxymethyl cellulose salt materials used for surface modification Carboxymethyl cellulose salt CMC-Na CMC-Li 4-1 0.25 0.25 4-2 0.1 0.3 4-3 0.4 0.1
[0050] Example 5
[0051] The difference from Example 1 is that in S2, a diethyl carbonate system containing methanol is used as the reaction solvent, while the remaining steps and operating conditions and parameters are exactly the same as in Example 1.
[0052] Example 6
[0053] The difference from Example 1 is that in S2, a methanol-containing propylene carbonate system is used as the reaction solvent, while the remaining steps and operating conditions and parameters are exactly the same as in Example 1.
[0054] Comparative Example 1
[0055] The only difference from Example 1 is:
[0056] In S1, the mixture of CMC-Na and CMC-Li is replaced with an equal mass of CMC-Na, that is, only 0.5 g of CMC-Na is added. The remaining steps and operating conditions and parameters are exactly the same as in Example 1.
[0057] Comparative Example 2
[0058] The only difference from Example 1 is:
[0059] In S1, 0.5 g of CMC-Li was used instead of the mixture of CMC-Na and CMC-Li, and the remaining steps and operating conditions and parameters were exactly the same as in Example 1.
[0060] Comparative Example 3
[0061] The only difference from Example 1 is:
[0062] In S2, deionized water was used instead of dimethyl carbonate as the reaction solvent, and the remaining steps and operating conditions and parameters were exactly the same as in Example 1.
[0063] Comparative Example 4
[0064] The only difference from Example 1 is:
[0065] In S2, no triglyceride monostearate was added, and the remaining steps and operating conditions and parameters were exactly the same as in Example 1.
[0066] Comparative Example 5
[0067] The only difference from Example 1 is:
[0068] In S2, 3-methacryloyloxypropyltrimethoxysilane was not added, and the remaining steps and operating conditions and parameters were exactly the same as in Example 1.
[0069] Comparative Example 6
[0070] The only difference from Example 1 is:
[0071] No dispersant or coupling agent was added in S2, and the remaining steps and operating conditions and parameters were exactly the same as in Example 1.
[0072] Comparative Example 7
[0073] The difference from Example 1 is that in S2, methanol is used as the reaction solvent and dimethyl carbonate is not added. The remaining steps and operating conditions and parameters are exactly the same as in Example 1.
[0074] Comparative Example 8
[0075] The difference from Example 1 is that in S2, only butanediol is used as the reaction solvent, while the remaining steps and operating conditions and parameters are exactly the same as in Example 1.
[0076] Application Example 1
[0077] Resistivity tests of lithium iron phosphate composite powders prepared in each experimental group (examples and comparative examples).
[0078] The resistivity of the lithium iron phosphate composite material powder obtained from the above examples and comparative examples was measured using the four-probe method, and the results are shown in Table 2.
[0079] Table 2. Resistivity of lithium iron phosphate composite materials prepared in each experimental group experimental group Example 1 Example 2 Example 3 Example 4-1 resistivity Ω·cm 3.18 5.76 3.27 7.5 experimental group Example 4-2 Example 4-3 Example 5 Example 6 resistivity Ω·cm 4.27 18.72 3.27 3.95 experimental group Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 resistivity Ω·cm 20.2 19.76 12.7 20.48 experimental group Comparative Example 5 Comparative Example 6 Comparative Example 7 Comparative Example 8 resistivity Ω·cm 22.64 26.61 8.36 10.63
[0080] The results in Table 2 show that the lithium iron phosphate composite powder prepared by the method of Example 1 has the lowest resistivity. According to the formula conductivity = 1 / resistivity, the sample of Example 1 has the highest conductivity.
[0081] In Example 2, based on Example 1, peracetic acid was used instead of performic acid as the catalyst for preparing the composite material in S2. The resistivity of the obtained composite material was higher than that of Example 1. It can be seen that although both belong to peroxyacid catalysts, their catalytic effects are different. The catalytic effect of performic acid is better than that of peracetic acid to a certain extent.
[0082] In Example 3, based on Example 1, the ultrasonic power during the surface modification treatment of S1 was reduced. Although the resistivity of the resulting composite material increased slightly, the change was very small, and the conductivity was almost the same as that in Example 1.
[0083] Example 4: Based on Example 1, the ratio of carboxymethyl cellulose material used in the surface modification treatment was changed. The results in Table 2 show that the conductivity of the prepared composite material increases significantly with the increase of CMC-Na content. When the mass ratio of CMC-Na to CMC-Li is 1:4, the conductivity of the composite material is at the highest level.
[0084] Based on Example 1, Examples 5 and 6 changed the solvents for surface pretreatment and in-situ polymerization. The results showed that when the organic solvents were dimethyl carbonate and diethyl carbonate, the resistivity of the products was not much different, while the effect of ethylene carbonate was slightly inferior.
[0085] Furthermore, in Comparative Examples 1 and 2 of the present invention, only a single carboxymethyl cellulose salt was used to modify the surface of lithium iron phosphate. Under the same treatment conditions, the resistivity of the prepared lithium iron phosphate composite products reached 20.2 Ω·cm and 14.43 Ω·cm, respectively, which were much higher than those of Example 1 (3.18 Ω·cm) or Examples 2-3. The conductivity of the composite material was significantly reduced, which shows that the carboxymethyl cellulose mixture can improve the conductivity of the composite material more than a single cellulose salt.
[0086] In Comparative Examples 3 to 8, the loading process of PEDOT / PSS polymer in the preparation of lithium iron phosphate composite materials was adjusted. The experimental results clearly show that the loading process of polymer binder, especially the parameters of solvent conditions, dispersant, and crosslinking agent in surface modification treatment, has a crucial impact on its loading effect. The dispersing effect of stearate surfactants and the crosslinking effect of coupling agents can both improve the conductivity of the composite.
[0087] The reason for the above phenomenon may be that the carboxymethyl cellulose mixture provides better bonding stability and good binding force with polymer binders compared with a single type of carboxymethyl cellulose salt. In addition, the dispersion effect of the stearate dispersant allows EDOT to be uniformly polymerized on lithium iron phosphate. At the same time, the dispersant and surfactant have the effect of inducing EDOT and promoting the polymerization of sodium styrene sulfonate into long-chain PEDOT, which ultimately improves the electrical conductivity of the composite material.
[0088] Application Example 2
[0089] The electrochemical performance of the lithium iron phosphate composite powders prepared in each experimental group (examples and comparative examples) was tested. The specific procedures were as follows:
[0090] The lithium iron phosphate composite powders prepared in Example 1 and Comparative Examples 1-5 were thoroughly ground with acetylene black and PVDF in a mortar, respectively. An appropriate amount of N-methylpyrrolidone solvent (NMP) was added, and the mixture was ground into a uniform fluid slurry. The slurry was then coated onto copper foil using a coating machine and then vacuum dried at 60°C to prepare LFP electrodes.
[0091] The mass ratio of LFP, acetylene black, and PVDF was 85 / 10 / 5. Self-assembled batteries were constructed, and the voltage was maintained between 3 and 3.5V. Different 1C discharge capacities and capacity retention rates were obtained. The specific discharge capacity of different composite materials and the capacity retention rates at different cycle numbers are shown in Table 3. Figure 3 , Figure 4 .
[0092] Table 3. Discharge capacity and capacity retention of the lithium iron phosphate composite material in the experimental group.
[0093] Table 3 combined Figures 3-4 It is evident that the lithium iron phosphate composite material prepared by the method of Example 1 of the present invention has the best conductivity cycling performance. After 100 cycles, its capacity retention rate can still be maintained at 98.73%. In contrast, the capacity retention rate of the composite materials prepared by Comparative Examples 1-2 is below 90%, and the capacity retention rate of the composite materials prepared by Comparative Examples 3-5 is even reduced to below 80%.
[0094] The above are merely preferred embodiments of the present invention and do not limit the scope of the patent. All equivalent changes and modifications made within the scope of the present invention should still fall within the scope of the present invention.
Claims
1. A method for preparing a lithium iron phosphate composite material, characterized in that, The steps include the following: Surface modification of S1 lithium iron phosphate: Polyanionic cellulose salt is dissolved in an organic solvent system, lithium iron phosphate powder is added, and the surface of lithium iron phosphate powder is modified under ultrasonic conditions to obtain surface-modified lithium iron phosphate powder. The polyanionic cellulose salt is selected from at least one of sodium carboxymethyl cellulose, potassium carboxymethyl cellulose, lithium carboxymethyl cellulose, and ammonium carboxymethyl cellulose. The organic solvent system is a mixture of alcohols and carbonate reagents, wherein the volume fraction of alcohols is 5% to 20%. The mass ratio of lithium iron phosphate powder to polyanionic cellulose salt is 5~15:1; Loading of S2 binder: PEDOT / PSS is used as binder and loaded onto the surface-modified lithium iron phosphate powder in S1 to obtain the lithium iron phosphate composite material.
2. The preparation method according to claim 1, characterized in that, In S1, a mixture of sodium carboxymethyl cellulose and lithium carboxymethyl cellulose is used to modify the surface of lithium iron phosphate.
3. The preparation method according to claim 2, characterized in that, In S1, the mass ratio of sodium carboxymethyl cellulose to lithium carboxymethyl cellulose is 1:1~5.
4. The preparation method according to claim 1, characterized in that, In S1, the alcohol is selected from at least one of methanol, ethanol, and glycol; the carbonate is selected from at least one of ethylene carbonate, dimethyl carbonate, and diethyl carbonate.
5. The preparation method according to claim 1, characterized in that, In S1, the ultrasonic conditions are: ultrasonic power 120~200 W, ultrasonic duration 20~40 min.
6. The preparation method according to claim 1, characterized in that, The loading of the binder described in S2 is specifically performed as follows: surface-modified lithium iron phosphate powder is added to the same organic solvent system as in S1, then a dispersant and a coupling agent are added, the mixture is stirred evenly and then ultrasonically treated for 3 to 10 minutes. Finally, conductive polymer monomer EDOT, peroxy acid, and sodium polystyrene sulfonate are added, and the mixture is stirred and polymerized at 50 to 70°C. After the reaction is completed, the solvent is removed and the mixture is vacuum dried to obtain the lithium iron phosphate composite material. The dispersant is selected from at least one of triglyceride monostearate and polyoxyethylene stearate; The coupling agent is selected from at least one of 3-aminopropylmethyldimethylsilane and 3-methacryloyloxypropyltrimethoxysilane; The peroxyacid is selected from either peroxyformic acid or peracetic acid.
7. The preparation method according to claim 6, characterized in that, The mass ratio of the dispersant to lithium iron phosphate powder is 0.01~0.05:1, the mass ratio of the coupling agent to lithium iron phosphate powder is 0.01~0.1:1, and the molar ratio of the conductive polymer monomer EDOT: peroxy acid: sodium polystyrene sulfonate is 1:0.5~0.8:0.8~1.
2.
8. A lithium iron phosphate composite material prepared by any one of the preparation methods described in claims 1 to 7.
9. The application of the lithium iron phosphate composite material according to claim 8 in a battery, characterized in that, The lithium iron phosphate composite material is used as a positive electrode material in lithium batteries.
10. A lithium-ion battery product containing the lithium iron phosphate composite material as described in claim 8.