Method for realizing direct regeneration of waste lithium iron phosphate by in-situ coating of conductive polymer

Abstract

The invention provides a method for realizing direct regeneration of waste lithium iron phosphate by in-situ coating of a conductive polymer. The method comprises the following steps: firstly, completely discharging a recycled waste lithium iron phosphate battery, then disassembling, separating and collecting to obtain a waste lithium iron phosphate positive electrode active material; and mixing the waste lithium iron phosphate with benzodifuran diketone, a lithium salt and a solvent, and reacting for a certain time at a certain temperature to realize direct regeneration of the waste lithium iron phosphate, thereby finally obtaining the regenerated lithium iron phosphate positive active material with excellent cycle performance and rate capability.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery cathode material recycling technology, specifically to a method for directly regenerating waste lithium iron phosphate by in-situ coating with conductive polymer. Background Technology

[0002] Lithium-ion batteries are widely used in energy storage, power, and everyday consumer electronics due to their ability to store, convert, and utilize energy. Currently, the lifespan of lithium-ion batteries is approximately 6-8 years. How to achieve green and resource-efficient recycling of such a large number of lithium-ion batteries at the end of their lifespan has become a key issue.

[0003] Lithium iron phosphate (LFP) cathode materials possess significant advantages such as long cycle life, low cost, and excellent safety performance, making them one of the most important cathode materials for lithium-ion batteries, accounting for more than one-third of the lithium-ion battery market. Therefore, recycling LFP cathode materials has become a crucial issue. Currently, the main methods for recycling LFP are wet recycling and pyrometallurgical recycling. Wet recycling involves dissolving valuable elements in a solution using chemical methods, followed by a series of chemical reactions for precipitation, separation, purification, and recovery. Pyrometallurgical recycling achieves recovery through a series of processes including roasting, dissolution, and separation. It's clear from the process flow that both pyrometallurgical and wet recycling require large amounts of acid / alkali solutions. More importantly, compared to ternary cathode materials, LFP does not contain precious metals such as cobalt and nickel. Therefore, neither pyrometallurgical nor wet recycling is the optimal green, environmentally friendly, and economical recycling strategy. How to directly regenerate waste LFP cathode materials has become a current research hotspot. Summary of the Invention

[0004] Research has found that lithium iron phosphate batteries, used as the positive electrode active material, inevitably develop lithium vacancy defects during cycling. The presence of these defects leads to the formation of Fe... 2+ Inevitably oxidized to Fe 3+ This results in the long-term existence of the FePO4 phase. During cycling, lithium iron phosphate also develops lithium iron phosphate reverse site defects, which block lithium-ion transport channels. The presence of these two defects is the primary cause of capacity decay in lithium-ion batteries using lithium iron phosphate as the positive electrode active material.

[0005] To address the environmental pain points of existing waste lithium iron phosphate recycling technologies, such as large acid and alkali inputs, difficult waste liquid treatment, and high energy consumption, as well as the poor recycling performance and rate performance of directly regenerated waste lithium iron phosphate, this invention provides a method for the direct regeneration of waste lithium iron phosphate using in-situ coating with a conductive polymer. The method utilizes Fe... 3+The natural oxidizing properties of lithium iron phosphate, combined with the reducing environment provided by the conductive polymer benzodifuran dione polymerized by oxidation reaction, enable the successful regeneration of waste lithium iron phosphate while coating the surface of lithium iron phosphate particles with a conductive polymer layer. This results in the regenerated lithium iron phosphate with conductive polymer coating exhibiting excellent cycle performance and rate performance during electrochemical testing.

[0006] The objective of this invention is achieved through the following technical solution:

[0007] A method for direct regeneration of waste lithium iron phosphate using in-situ coating with a conductive polymer, the method comprising the following steps:

[0008] (1) Disassemble the recycled waste lithium iron phosphate batteries after they are fully discharged, and separate and collect the waste lithium iron phosphate positive electrode active materials.

[0009] (2) Mix the waste lithium iron phosphate positive electrode active material, benzodifuran dione, solvent and lithium salt from step (1) and react to prepare the conductive polymer-coated lithium iron phosphate positive electrode active material, so as to realize the direct regeneration of waste lithium iron phosphate.

[0010] According to an embodiment of the present invention, in step (1), the waste lithium iron phosphate battery is not specifically defined, and it can be a lithium iron phosphate battery whose capacity has decayed to less than 80% after a number of charge-discharge cycles; for example, a lithium iron phosphate battery whose capacity has decayed to less than 70% after 2000 charge-discharge cycles.

[0011] According to an embodiment of the present invention, in step (1), the recycled waste lithium iron phosphate batteries are fully discharged using methods known in the art; the recycled waste lithium iron phosphate batteries are disassembled using methods known in the art; and the recycled waste lithium iron phosphate positive electrode active materials are separated and collected using methods known in the art.

[0012] According to an embodiment of the present invention, in step (1), the waste lithium iron phosphate positive electrode active material in the waste lithium iron phosphate battery contains a FePO4 phase, and the mass percentage of the FePO4 phase is, for example, 5% or more, such as 10% or more, 20% or more, or 30% or more. The waste lithium iron phosphate positive electrode active material in the waste lithium iron phosphate battery also contains a LiFePO4 phase.

[0013] According to an embodiment of the present invention, in step (2), the solvent is selected from N,N-dimethylformamide and / or dimethylacetamide.

[0014] According to an embodiment of the present invention, in step (2), the lithium salt is selected from at least one of lithium carbonate, lithium hydroxide and lithium acetate.

[0015] According to an embodiment of the present invention, in step (2), the CAS number of the benzodifuran dione is 30272-74-3.

[0016] According to an embodiment of the present invention, in step (2), the structural formula of the benzodifurandione is:

[0017]

[0018] According to an embodiment of the present invention, in step (2), the temperature of the reaction is 80°C-120°C, for example, 80°C, 90°C, 100°C, 110°C or 120°C.

[0019] According to an embodiment of the present invention, in step (2), the reaction time is 1 hour to 3 hours, for example, 1 hour, 2 hours or 3 hours.

[0020] According to an embodiment of the present invention, in step (2), the mass ratio of the waste lithium iron phosphate positive electrode active material to benzodifuran dione is 7-10:1, for example, 7:1, 8:1, 9:1 or 10:1.

[0021] According to an embodiment of the present invention, in step (2), the mass ratio of the waste lithium iron phosphate positive electrode active material to the lithium salt is 100:3-10, for example, 100:3, 100:4, 100:5, 100:6, 100:7, 100:8, 100:9 or 100:10.

[0022] According to an embodiment of the present invention, in step (2), the mass-to-volume ratio of the waste lithium iron phosphate positive electrode active material to the solvent is 40-80:1 (unit mg / ml), for example, 40:1, 45:1, 50:1, 55:1, 60:1, 65:1, 70:1, 75:1 or 80:1.

[0023] According to an embodiment of the present invention, in step (2), the reaction is carried out under normal pressure conditions.

[0024] According to an embodiment of the present invention, in step (2), the reaction is carried out in an air atmosphere.

[0025] According to an embodiment of the present invention, in step (2), the reaction is carried out under stirring conditions, and the stirring speed is 300 r / min-600 r / min, for example 300 r / min, 350 r / min, 400 r / min, 450 r / min, 500 r / min, 550 r / min or 600 r / min.

[0026] According to the embodiment of the present invention, in step (2), the addition of benzodifurandione provides a reducing environment for the liquid phase system (including the system of waste lithium iron phosphate positive electrode active material, lithium salt and solvent). The addition of benzodifurandione can also promote the insertion of lithium ions and the repair of lithium iron phosphate antisite defects. This is mainly because benzodifurandione undergoes a polymerization reaction under liquid phase conditions during the reaction process to generate a conductive polymer (polybenzodifurandione) and coat the surface of the regenerated lithium iron phosphate. At the same time, the FePO4 phase in the waste lithium iron phosphate is reduced to the LiFePO4 phase, achieving the effect of in-situ coating of conductive polymer while regenerating the waste lithium iron phosphate.

[0027] According to an embodiment of the present invention, in step (2), the lithium iron phosphate positive electrode active material in situ coated with the conductive polymer does not contain the FePO4 phase.

[0028] According to an embodiment of the present invention, in step (2), after the reaction is completed, the reaction product is post-processed, the post-processing including washing and drying; exemplarily, the washing is to place the reaction product in a vacuum filter and wash it sequentially with N,N-dimethylformamide and deionized water; the drying is to place the washed reaction product in an 80°C constant temperature oven for vacuum drying for 12-24 hours.

[0029] The present invention also provides a lithium iron phosphate positive electrode active material in situ coated with a conductive polymer prepared by the above method.

[0030] According to an embodiment of the present invention, the conductive polymer-coated lithium iron phosphate cathode active material has a core-shell structure, including a core and a shell, wherein the core is lithium iron phosphate and the shell is polybenzodifurandione.

[0031] According to an embodiment of the present invention, the lithium iron phosphate does not contain the FePO4 phase.

[0032] According to an embodiment of the present invention, the average particle size of the core is 200-500 nm, for example, 200 nm, 250 nm, 300 nm, 350 nm, 400 nm, 450 nm or 500 nm.

[0033] According to an embodiment of the present invention, the thickness of the shell layer is 1-3 nm, for example, 1 nm, 1.5 nm, 2 nm, 2.5 nm or 3 nm.

[0034] According to an embodiment of the present invention, the conductive polymer-coated lithium iron phosphate positive electrode active material is formed by polymerizing benzodifurandione monomer and coating it in situ onto the surface of regenerated lithium iron phosphate.

[0035] According to an embodiment of the present invention, the lithium iron phosphate positive electrode active material in situ coated with the conductive polymer is designated as RSLFP@PBFDO.

[0036] The present invention also provides the use of the above-mentioned conductive polymer in-situ coated lithium iron phosphate positive electrode active material for use in lithium-ion batteries.

[0037] According to an embodiment of the present invention, the conductive polymer-coated lithium iron phosphate positive electrode active material is used as the positive electrode of a lithium-ion battery.

[0038] The beneficial effects of this invention are:

[0039] This invention provides a method for the direct regeneration of spent lithium iron phosphate batteries using in-situ coating with conductive polymers. The method involves first fully discharging and disassembling the recycled spent lithium iron phosphate batteries, separating and collecting the spent lithium iron phosphate cathode active material; then mixing this material with benzodifuran dione, lithium salt, and a solvent, and reacting it at a specific temperature for a specific time to achieve direct regeneration of the spent lithium iron phosphate, ultimately obtaining a regenerated lithium iron phosphate cathode active material with excellent cycle performance and rate capability.

[0040] Specifically, the regeneration method of the present invention has the following advantages:

[0041] (1) Compared with the traditional wet / fired recycling methods for lithium-ion battery cathode materials, this invention has the advantages of being green and environmentally friendly, as it does not require the input of acid / alkali solutions and does not generate a large amount of harmful waste liquid. It retains the original structure of waste lithium iron phosphate, which greatly reduces the input of energy and chemical reagents during the recycling process. The recycling process of this invention is simple and has few steps, resulting in a very short regeneration cycle. Moreover, the regenerated products can be directly used as active materials for lithium-ion battery cathodes without any other treatment.

[0042] (2) Compared with the current direct regeneration method of waste lithium iron phosphate, the present invention does not have a solid-phase high-temperature sintering process, so there will be no large energy consumption input, and no large amount of greenhouse gases will be generated, which is more in line with the original intention of green environmental protection. Compared with the current direct regeneration method of waste lithium iron phosphate by adding carbon source to coat carbon layer, the direct regeneration method of the present invention directly regenerates lithium iron phosphate with conductive polymer coating in liquid phase system, and the conductive polymer coating layer obtained by this method is more uniform and has better conductivity.

[0043] (3) By utilizing reducing conductive polymer monomers to create a reducing environment, Fe 3+ The natural matching of oxidation properties enables targeted repair of lithium vacancy defects and lithium iron phosphate antisite defects, with high repair efficiency. The resulting conductive polymer-coated lithium iron phosphate cathode active material does not contain the FePO4 phase and can be directly used as a cathode active material for lithium-ion batteries.

[0044] (4) The conductive polymer-coated lithium iron phosphate cathode active material obtained in this invention can be directly used as the cathode of lithium-ion batteries and exhibits excellent cycle performance and rate performance. For example, the battery assembled with RSLFP@PBFDO can achieve an initial discharge capacity of 160.9 mAh·g at 1C rate. -1 After 300 cycles, it remained at 143.3 mAh·g. -1 After 1000 cycles at 10C, the battery capacity can be maintained at 116.0 mAh·g. -1 In rate performance testing, after 10 cycles each at high rates of 2C, 5C, and 10C, the specific capacity recovered to 148.0 mAh·g when the rate was reduced to 0.1C. -1 above. Attached Figure Description

[0045] Figure 1 The image shows the X-ray diffraction (XRD) pattern of the conductive polymer-coated lithium iron phosphate cathode active material prepared in situ in Example 1.

[0046] Figure 2 This is a scanning electron microscope (SEM) image of the lithium iron phosphate positive electrode active material in situ coated with conductive polymer prepared in Example 1.

[0047] Figure 3 The image shows the X-ray photoelectron spectroscopy (XPS) spectrum of the lithium iron phosphate cathode active material in situ coated with conductive polymer prepared in Example 1.

[0048] Figure 4 The results show the 1C cycle performance of a lithium-ion battery assembled using the conductive polymer in situ coated lithium iron phosphate positive electrode active material prepared in Example 1 as the positive electrode material.

[0049] Figure 5 The results show the rate performance test results of a lithium-ion battery assembled using the conductive polymer in situ coated lithium iron phosphate positive electrode active material prepared in Example 1 as the positive electrode material.

[0050] Figure 6 The results show the ultra-high rate cycle performance of a lithium-ion battery assembled using the conductive polymer in situ coated lithium iron phosphate cathode active material prepared in Example 1 as the cathode material.

[0051] Figure 7 The results are obtained by electrochemical impedance spectroscopy (EIS) of lithium-ion batteries assembled using lithium iron phosphate positive electrode active material in situ coated with conductive polymer prepared in Example 1 as the positive electrode material.

[0052] Figure 8 The image shows the XRD pattern of waste lithium iron phosphate black powder from Comparative Example 1.

[0053] Figure 9 The image shows the SEM image of waste lithium iron phosphate black powder from Comparative Example 1.

[0054] Figure 10 XPS plot of waste lithium iron phosphate black powder from Comparative Example 1.

[0055] Figure 11 The results show the 1C cycle performance of the lithium-ion battery assembled using waste lithium iron phosphate black powder from Comparative Example 1 as the positive electrode material.

[0056] Figure 12 The results show the rate performance test results of the lithium-ion battery assembled using waste lithium iron phosphate black powder from Comparative Example 1 as the positive electrode material.

[0057] Figure 13 The results of electrochemical impedance spectroscopy (EIS) are shown for the lithium-ion battery assembled using waste lithium iron phosphate black powder from Comparative Example 1 as the positive electrode material. Detailed Implementation

[0058] The method of the present invention will be further described in detail below with reference to specific embodiments. It should be understood that the following embodiments are merely illustrative and explanatory of the present invention and should not be construed as limiting the scope of protection of the present invention. All technologies implemented based on the above content of the present invention are covered within the scope of protection intended by the present invention.

[0059] Unless otherwise specified, the experimental methods used in the following examples are conventional methods; unless otherwise specified, the reagents and materials used in the following examples are commercially available.

[0060] The instruments and operating instructions used in the tests involved in the following examples and comparative examples are as follows:

[0061] 1) X-ray diffraction (XRD) test: The instrument model is UltimaIV-185, manufactured by Rigaku Corporation, Japan;

[0062] 2) Scanning electron microscope (SEM) test: The instrument model is S-4800, manufactured by Hitachi, Japan;

[0063] 3) X-ray photoelectron spectroscopy (XPS) test: The instrument model is AXIS Supra+, manufactured by Shimadzu Corporation, Japan;

[0064] 4) AC impedance testing: Electrochemical workstation, China, test frequency range 0.1Hz-0.1MHz;

[0065] 5) Cyclic performance test: CT2001A Land battery testing system, manufactured by Wuhan Landian Electronics Co., Ltd.

[0066] 6) Assembly of CR2032 button cell batteries:

[0067] Lithium iron phosphate, conductive carbon black (Super P), and polyvinylidene fluoride (PVDF) were weighed and ground in a mass ratio of 8:1:1, then an appropriate amount of NMP was added and ground to form a slurry. This slurry was then evenly coated onto copper foil using a scraper and dried in a 60℃ oven for 12 hours, followed by drying in a vacuum oven at 120℃ for 3 hours. The dried electrode sheets were cut into pieces using a cutting machine and used as the positive electrode. The counter electrode was a lithium metal sheet. The electrolyte was a solution prepared by mixing ethylene carbonate (EC) and dimethyl carbonate (DMC) in a 1:1 volume ratio, with 1 mol / L LiPF6 as the solute. The separator was Celgard 2500. The cells were assembled into CR2032 button cells in an argon glove box (water <0.01 ppm, oxygen <0.01 ppm).

[0068] Example 1

[0069] 1) The recycled waste lithium iron phosphate batteries (lithium iron phosphate batteries whose capacity has decayed to less than 70% after 2000 charge-discharge cycles) are completely discharged and disassembled, and the positive electrode active material is separated and collected to obtain waste lithium iron phosphate black powder.

[0070] 2) Weigh 0.072g of benzodifurandione and 10ml of N,N-dimethylformamide into a small glass bottle, and stir with a magnetic stirrer at 350r / min for 5 minutes to dissolve.

[0071] 3) Weigh 0.624g of waste lithium iron phosphate black powder and 0.044g of lithium carbonate into the small glass bottle mentioned above, set the temperature of the magnetic stirrer to 100℃, and stir the reaction at 500r / min for 2h.

[0072] 4) The product obtained from the reaction was placed in a vacuum filter and washed sequentially with 5 ml of N,N-dimethylformamide and 30 ml of deionized water. The washed product was then placed in an 80℃ constant temperature oven for vacuum drying for 12 h to obtain the conductive polymer-coated lithium iron phosphate positive electrode active material (RSLFP@PBFDO).

[0073] The RSLFP@PBFDO obtained in Example 1 was assembled into CR2032 button cells according to the above method, and its 1C cycle performance, rate performance, 10C ultra-high rate cycle performance and electrochemical impedance were tested.

[0074] The XRD pattern and SEM image of RSLFP@PBFDO obtained in Example 1 are as follows: Figure 1 and Figure 2 XRD analysis revealed that the RSLFP@PBFDO sample of Example 1 exhibited distinct characteristic peaks of the LiFePO4 phase and showed good crystallinity, while simultaneously lacking the FePO4 phase. SEM images showed a clear coating layer on the surface of the RSLFP@PBFDO sample particles and significant inter-particle adhesion. The XPS full spectrum of the RSLFP@PBFDO obtained in Example 1 was obtained from... Figure 3 As shown in the XPS full spectrum, the ratio of C1s peak intensity to O1s peak intensity in the RSLFP@PBFDO sample of Example 1 is significantly enhanced, which is due to the abundant C element in the conductive polymer.

[0075] The 1C cycle performance, rate performance, 10C ultra-high rate cycle performance, and electrochemical impedance spectroscopy results of the battery assembled using RSLFP@PBFDO as the cathode material obtained in Example 1 are as follows: Figures 4 to 7 Expanding from... Figure 4 As can be seen, the battery retains a capacity of 143.3 mAh·g after 300 cycles at a 1C rate. -1 ;from Figure 5 As can be seen, the battery capacity can be maintained at 100.0 mAh·g even at a super-high rate of 10C. -1 The above, and after the rate of change is reduced to 0.1C, it recovers to its original capacity (148.0 mAh·g). -1 ).from Figure 6 As can be seen, the battery can stably cycle for more than 1000 times at a super-high rate of 10C, while maintaining a capacity of 116.0 mAh·g. -1 The above demonstrates excellent high-rate cycling stability; from Figure 7 As can be seen from this, the battery has a small charge transfer resistance R. ct It is approximately 105.2Ω.

[0076] Comparative Example 1

[0077] The recycled waste lithium iron phosphate batteries (those whose capacity has decayed to less than 70% after 2000 charge-discharge cycles) are completely discharged and disassembled. The positive electrode active material is separated and collected to obtain waste lithium iron phosphate black powder.

[0078] The waste lithium iron phosphate black powder obtained in Comparative Example 1 was assembled into CR2032 button batteries according to the above method, and 1C cycle performance, rate performance and electrochemical impedance were tested.

[0079] The XRD pattern and SEM image of the waste lithium iron phosphate black powder of Comparative Example 1 are as follows: Figure 8 and Figure 9XRD analysis shows that the characteristic peaks of the waste lithium iron phosphate black powder in Comparative Example 1 correspond perfectly with those of the LiFePO4 and FePO4 phases, proving that the waste lithium iron phosphate black powder in Comparative Example 1 is composed of LiFePO4 and FePO4 phases, with the FePO4 phase accounting for approximately 30% by mass. Figure 9 As can be seen, the waste lithium iron phosphate black powder of Comparative Example 1 has distinct particles and some binder residue. The XPS full spectrum of the waste lithium iron phosphate black powder of Comparative Example 1 is shown in the figure. Figure 10 The exhibition, from Figure 10 As can be seen from the data, the ratio of C1s peak intensity to O1s peak intensity of the waste lithium iron phosphate black powder in Comparative Example 1 is relatively low.

[0080] The 1C cycle performance, rate performance, and electrochemical impedance spectroscopy results of the waste lithium iron phosphate black powder of Comparative Example 1 were as follows: Figures 11 to 13 Displayed in [the text]. From [the text] Figure 11 As can be seen, the battery capacity has decreased to 68.4 mAh·g after 300 cycles at 1C rate. -1 ;from Figure 12 As can be seen, with the development of tests at different rates, the battery exhibits serious problems such as extremely unstable cycling and inability to fully utilize its capacity; from Figure 13 As can be seen from this, the battery has a very large charge transfer resistance R. ct It is approximately 410.5Ω.

[0081] A comparison of Example 1 and Comparative Example 1 shows that the present invention utilizes a reducing conductive polymer monomer to create a reducing environment, Fe 3+ The natural matching of oxidation properties enables targeted repair of lithium vacancy defects and lithium iron phosphate reverse site defects with high repair efficiency. The regenerated RSLFP@PBFDO obtained by this invention can be directly used as the positive electrode of lithium-ion batteries and can exhibit excellent cycle performance and rate performance.

[0082] The embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiments. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for direct regeneration of waste lithium iron phosphate using in-situ coating with a conductive polymer, the method comprising the following steps: (1) Disassemble the recycled waste lithium iron phosphate batteries after they are fully discharged, and separate and collect the waste lithium iron phosphate positive electrode active materials. (2) Mix the waste lithium iron phosphate positive electrode active material, benzodifuran dione, solvent and lithium salt from step (1) and react to prepare the conductive polymer-coated lithium iron phosphate positive electrode active material, so as to realize the direct regeneration of waste lithium iron phosphate.

2. The method according to claim 1, wherein, In step (1), the waste lithium iron phosphate battery is a lithium iron phosphate battery whose capacity has decayed to less than 80% after several charge-discharge cycles.

3. The method according to claim 1 or 2, wherein, In step (1), the waste lithium iron phosphate positive electrode active material in the waste lithium iron phosphate battery contains FePO4 phase; the waste lithium iron phosphate positive electrode active material in the waste lithium iron phosphate battery also contains LiFePO4 phase.

4. The method according to any one of claims 1-3, wherein, In step (2), the solvent is selected from N,N-dimethylformamide and / or dimethylacetamide; And / or, in step (2), the lithium salt is selected from at least one of lithium carbonate, lithium hydroxide and lithium acetate; And / or, in step (2), the reaction temperature is 80℃-120℃; And / or, in step (2), the reaction time is 1 hour to 3 hours.

5. The method according to any one of claims 1-4, wherein, In step (2), the mass ratio of the waste lithium iron phosphate positive electrode active material to benzodifuran dione is 7-10:1; And / or, in step (2), the mass ratio of the waste lithium iron phosphate positive electrode active material to the lithium salt is 100:3-10; And / or, in step (2), the mass-to-volume ratio of the waste lithium iron phosphate positive electrode active material to the solvent is 40-80:1, in mg / ml.

6. The method according to any one of claims 1-5, wherein, In step (2), the lithium iron phosphate positive electrode active material coated in situ with the conductive polymer does not contain the FePO4 phase.

7. The conductive polymer-coated lithium iron phosphate cathode active material prepared by the method according to any one of claims 1-6.

8. The conductive polymer-coated lithium iron phosphate cathode active material according to claim 7, wherein, The conductive polymer-coated lithium iron phosphate cathode active material has a core-shell structure, including a core and a shell, wherein the core is lithium iron phosphate and the shell is polybenzodifurandione.

9. The conductive polymer-coated lithium iron phosphate cathode active material according to claim 8, wherein, The lithium iron phosphate does not contain the FePO4 phase. Preferably, the average particle size of the core is 200-500 nm; And / or, the thickness of the shell is 1-3 nm.

10. Use of the conductive polymer in-situ coated lithium iron phosphate positive electrode active material according to any one of claims 7-9, for use in lithium-ion batteries.

Images