Method for preparing lithium iron manganese phosphate precursor and application thereof
By combining co-precipitation and ion exchange methods to prepare lithium manganese iron phosphate precursors, and using brewer's grains biochar for carbon coating, the problems of low conductivity and structural instability of lithium manganese iron phosphate materials were solved, and high-performance cathode materials were prepared.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- HEFEI GUOXUAN HIGH TECH POWER ENERGY
- Filing Date
- 2024-05-07
- Publication Date
- 2026-06-05
Abstract
Description
Technical Field
[0001] This invention belongs to the field of lithium-ion battery cathode material preparation technology, specifically relating to a method and application for preparing lithium manganese iron phosphate precursor. Background Technology
[0002] Compared to lithium iron phosphate, lithium manganese phosphate (LiMnPO4) (LMP), which also has an olivine-type structure, has a higher operating voltage (4.1V) and energy density (701Wh / kg). However, LMP has extremely low conductivity (<10). -10 S / cm) and Mn during charging and discharging 3+ The resulting Jahn-Teller effect has a significant impact on the structural stability of LMP.
[0003] Researchers have discovered that Fe-doped LMP synthesized lithium manganese iron phosphate (LiMn) 1-x Fe x PO4 (LMFP) not only improves the electrical conductivity of the material, but also inhibits the growth of Mn. 3+ The Jahn-Teller effect allows LMFPs to possess both the high energy density of LMPs and the good kinetic performance of LFPs, thus making them an ideal upgrade to LFP cathode materials. However, the relatively low conductivity and structural instability of LMFPs still hinder their commercial application.
[0004] Currently, the industrial production of lithium manganese iron phosphate (LFP) typically employs a two-step method, involving secondary coating and secondary sintering to address the low conductivity of LFP. However, this method suffers from complex processes and high production costs. Research indicates that a one-step sintering process using a suitable precursor is the optimal choice for LFP production. However, current precursors such as ferromanganese oxalate, ferromanganese carbonate, ferromanganese phosphate, and ferrous manganese ammonium phosphate generally result in LFP batteries with low capacity and unstable electrical performance. Therefore, developing a more stable LFP precursor to achieve industrial-scale production of LFP is imperative. Summary of the Invention
[0005] The purpose of this invention is to provide a method and application for preparing lithium manganese iron phosphate precursors. By combining co-precipitation and ion exchange, the grain morphology, size and distribution of the MnFe-PO3-OH precursor can be easily controlled. Furthermore, by adding brewer's grains biochar, the dual purpose of in-situ N and P doping and graphitized carbon coating is achieved, thereby improving the electronic conductivity of lithium manganese iron phosphate and obtaining high-performance lithium manganese iron phosphate materials.
[0006] To achieve the above objectives, the present invention provides the following technical solution:
[0007] In a first aspect, the present invention provides a method for preparing a lithium manganese iron phosphate hydroxide precursor, comprising the following steps:
[0008] S1. Manganese source, iron source, alkali source and carbonate are mixed and subjected to hydrothermal reaction, crystallization, to obtain MnFe-CO3-OH precursor;
[0009] S2. Add water to the MnFe-CO3-OH precursor obtained in step S1 to form a slurry, add dihydrogen phosphate salts, reflux, filter, wash and dry the resulting precipitate to obtain lithium manganese iron phosphate hydroxide precursor (MnFe-PO3-OH).
[0010] In step S1, the Mn of the manganese source 2+ Fe with the iron source 3+ molar ratio n(Mn) 2+ ) / n(Fe 3+ ) is (1-4): 1.
[0011] In step S1, the alkali source is selected from one or more of NaOH, KOH and ammonia water.
[0012] In step S1, the OH- of the alkali source - With Mn 2+ and Fe 3+ The total molar ratio n(OH) - ) / [n(Mn 2+ )+n(Fe 3+ )] is (1.5-4):1.
[0013] In step S1, the carbonate is selected from one or more of NaHCO3, Na2CO3 and K2CO3.
[0014] In step S1, the CO3 of the carbonate 2- Fe with the iron source 3+ molar ratio n(CO3) 2- ) / n(Fe 3+ (2-4): 1.
[0015] In step S1, the conditions for the hydrothermal reaction are: reaction temperature of 60-75℃, reaction time of 1-4h, and pH of 9.5-10.5.
[0016] In step S1, the crystallization conditions are: crystallization temperature of 70-100℃ and crystallization time of 10-20h.
[0017] In step S1, the crystallized product is filtered, washed, and dried.
[0018] In step S2, the concentration of the slurry is 30%-50%.
[0019] In step S2, the dihydrogen phosphate compound is selected from one or more of KH2PO4, NaH2PO4, and NH4H2PO4.
[0020] In step S2, the molar ratio of the dihydrogen phosphate compound to the MnFe-CO3-OH precursor is (3-5):1.
[0021] In step S2, the reflux conditions are: reflux temperature 50-70℃, reflux time 2-4h.
[0022] In step S2, the precipitate obtained after reflux is filtered, washed, and dried.
[0023] Secondly, the present invention further provides a precursor of lithium manganese iron phosphate hydroxide, MnFe-PO3-OH, obtained by the above preparation method, with the chemical formula MnFe-PO3-OH. x Fe 1-x (OH) z PO4, where x ranges from 0.8 to 0.5, y ranges from 0.2 to 0.5, x:y = (1-3):1, and z ranges from 1 to 3.
[0024] Thirdly, the present invention further provides a lithium manganese iron phosphate material, comprising the following components: the above-mentioned lithium manganese iron phosphate hydroxide precursor MnFe-PO3-OH, a carbon source, brewer's grains biochar, and a lithium source.
[0025] The lithium source contains Li + The molar ratio of the hydroxide lithium manganese iron phosphate precursor MnFe-PO3-OH to the hydroxide is (1-1.2):1.
[0026] The brewer's grain biochar is obtained by pyrolysis of brewer's grains.
[0027] The amount of brewer's grain biochar added is 2000-4000 ppm.
[0028] Fourthly, the present invention further provides a method for preparing the lithium manganese iron phosphate material, comprising the following steps:
[0029] (1) Pyrolysis of beer lees yields beer lees biochar;
[0030] (2) Add carbon source, crushed brewer's grain biochar, lithium source and lithium manganese iron phosphate hydroxide precursor to water, and then grind and spray to obtain a mixture.
[0031] (3) Sinter the mixture obtained in step (2) to obtain lithium manganese iron phosphate material.
[0032] In step (1), the pyrolysis conditions are: pyrolysis temperature of 500-700℃ and pyrolysis time of 10-20h.
[0033] In step (2), the carbon source is selected from one or more of glucose, sucrose, starch, cyclodextrin, citric acid, polyethylene glycol, polyvinyl alcohol, glycerol, polyethylene oxide, polystyrene, styrene-butadiene-styrene block copolymer and carbon nanotubes.
[0034] In step (2), the carbon content in the mixture is 0.8-1.5% based on lithium iron phosphate.
[0035] In step (2), the particle size of the sand mill is controlled to be 0.4-0.6μm.
[0036] In step (3), the sintering conditions are: temperature of 550-750℃ and time of 15-24h.
[0037] In step (3), the lithium manganese iron phosphate material is pulverized to an average particle size of 0.8-3.0 μm.
[0038] Fifthly, the present invention further provides a lithium-ion battery, comprising a positive electrode and a negative electrode; wherein the material of the positive electrode is the lithium manganese iron phosphate material.
[0039] Compared with the prior art, the beneficial effects achieved by the present invention are:
[0040] 1. The method provided by this invention achieves the goal of easily controlling the grain morphology, size, and distribution of the MnFe-PO3-OH precursor. In actual production, according to the requirements of the final product, by adjusting process conditions such as solution concentration, reaction temperature, reaction time, and pH, morphological structures such as plate-like, rod-like, needle-like, and honeycomb-like structures can be generated.
[0041] 2. By adding brewer's grain biochar as a composite carbon source, the present invention can form an in-situ N and P doped carbon layer during calcination, which enhances the conductivity of the material. Moreover, heteroatom doping can also adjust the electronic structure of the carbon material, enhance its chemical activity, and promote the contact between the carbon material and the active material. In addition, the pyrolyzed brewer's grain biochar has more graphitized carbon, which further improves the conductivity of the material. Detailed Implementation
[0042] The present invention will be further described below with reference to specific embodiments, but the present invention is not limited to the following embodiments.
[0043] Unless otherwise specified, the experimental methods used in the following examples are conventional methods.
[0044] Unless otherwise specified, all reagents, materials, instruments, etc. used in the following examples are commercially available.
[0045] Example 1
[0046] The preparation steps of the MnFe-PO3-OH precursor are as follows:
[0047] 1) Dissolve Fe(NO3)3 (1mol / L) and Mn(NO3)2 (1mol / L) in 100mL of deionized water and stir with a magnetic stirrer for 30min to form solution A;
[0048] According to n(CO3) 2- ) / n(Fe 3+ )=2,n(NaOH) / [n(Mn 2+ )+n(Fe 3+ [ ] = 2, add NaOH and NaHCO3 to water to form solution B;
[0049] After uniformly mixing solutions B and A, the mixture was added to a hydrothermal reactor and reacted at 60°C for 1 hour, maintaining the pH at 9.5-10.5.
[0050] After the reaction was completed, the reaction solution was placed at 70℃ for crystallization for 10 hours, and then filtered, washed and dried to obtain the MnFe-CO3-OH precursor.
[0051] 2) Add the MnFe-CO3-OH precursor obtained in step 1) to water to make a uniformly dispersed slurry, and add 10% KH2PO4 solution to the slurry. Reflux the slurry at 50°C for 2 hours using a reflux device. Then filter, wash and dry the precipitate to obtain the MnFe-PO3-OH precursor.
[0052] The preparation steps of lithium manganese iron phosphate material are as follows:
[0053] 3) Place 100g of brewer's grains into a tube furnace and pyrolyze it at 500℃ under N2 atmosphere for 10 hours. After grinding and sieving, brewer's grains biochar is obtained.
[0054] 4) The carbon source, the brewer's grain biochar obtained in step 3), the lithium source, and the MnFe-PO3-OH precursor obtained in step 2) are sequentially added to water. The carbon content (calculated as carbon in glucose) is controlled at 0.8% (based on the final lithium manganese iron phosphate product), the amount of brewer's grain biochar added is 2000ppm (based on the final lithium manganese iron phosphate product), the molar ratio of Li:MnFe-PO3-OH is controlled at 1:1, the slurry is sand-milled to 0.6µm, and spray-dried to obtain a mixture.
[0055] 5) The mixture obtained in step 4) is sintered at 550℃ for 15h, and finally crushed to obtain lithium manganese iron phosphate material with a particle size of 0.8-3.0um.
[0056] Example 2
[0057] The preparation steps of the MnFe-PO3-OH precursor are as follows:
[0058] 1) Dissolve Fe(NO3)3 (1mol / L) and Mn(NO3)2 (1.5mol / L) in 100mL of deionized water and stir with a magnetic stirrer for 30min to form solution A;
[0059] According to n(CO3) 2- ) / n(Fe 3+ )=3,n(NaOH) / [n(Mn 2+ )+n(Fe 3+ [ ] = 2, add NaOH and NaHCO3 to water to form solution B;
[0060] After uniformly mixing solutions B and A, the mixture was added to a hydrothermal reactor and reacted at 65°C for 2 hours, maintaining the pH at 9.5-10.5.
[0061] After the reaction was completed, the reaction solution was placed at 80℃ for crystallization for 16 hours, and then filtered, washed and dried to obtain the MnFe-CO3-OH precursor.
[0062] 2) Add the MnFe-CO3-OH precursor obtained in step 1) to water to make a uniformly dispersed slurry, and add 10% KH2PO4 solution to the slurry. Reflux the slurry at 60°C for 3 hours using a reflux device. Then filter, wash and dry the precipitate to obtain the MnFe-PO3-OH precursor.
[0063] The preparation steps of lithium manganese iron phosphate material are as follows:
[0064] 3) Place 100g of brewer's grains into a tube furnace and pyrolyze it at 600℃ under N2 atmosphere for 15 hours. After grinding and sieving, brewer's grains biochar is obtained.
[0065] 4) The carbon source, the brewer's grain biochar obtained in step 3), the lithium source, and the MnFe-PO3-OH precursor obtained in step 2) are sequentially added to water. The carbon content (calculated as carbon in glucose) is controlled at 1.0% (based on the final lithium manganese iron phosphate product), the amount of brewer's grain biochar added is 3000ppm (based on the final lithium manganese iron phosphate product), and the molar ratio of Li:MnFe-PO3-OH is controlled at 1.05:1. The slurry is sand-milled to 0.55um and spray-dried to obtain a mixture.
[0066] 5) The mixture obtained in step 4) is sintered at 600℃ for 20h, and finally crushed to obtain lithium manganese iron phosphate material with a particle size of 0.8-3.0um.
[0067] Example 3
[0068] The preparation steps of the MnFe-PO3-OH precursor are as follows:
[0069] 1) Dissolve Fe(NO3)3 (1mol / L) and Mn(NO3)2 (2mol / L) in 100mL of deionized water and stir with a magnetic stirrer for 30min to form solution A;
[0070] According to n(CO3) 2- ) / n(Fe 3+ )=3,n(NaOH) / [n(Mn 2+ )+n(Fe 3+ [ ] = 2, add NaOH and NaHCO3 to water to form solution B;
[0071] After uniformly mixing solutions B and A, the mixture was added to a hydrothermal reactor and reacted at 65°C for 3 hours, maintaining the pH at 9.5-10.5.
[0072] After the reaction was completed, the reaction solution was placed at 90℃ for 2 hours to crystallize, and then filtered, washed and dried to obtain the MnFe-CO3-OH precursor.
[0073] 2) Add the MnFe-CO3-OH precursor obtained in step 1) to water to make a uniformly dispersed slurry, and add 20% KH2PO4 solution to the slurry. Reflux the slurry at 60°C for 3 hours using a reflux device. Then filter, wash and dry the precipitate to obtain the MnFe-PO3-OH precursor.
[0074] The preparation steps of lithium manganese iron phosphate material are as follows:
[0075] 3) Place 100g of brewer's grains into a tube furnace and pyrolyze it at 600℃ under N2 atmosphere for 20h. After grinding and sieving, brewer's grains biochar is obtained.
[0076] 4) The carbon source, the brewer's grain biochar obtained in step 3), the lithium source, and the MnFe-PO3-OH precursor obtained in step 2) are sequentially added to water. The carbon content (calculated as carbon in glucose) is controlled at 1.2% (based on the final lithium manganese iron phosphate product), the amount of brewer's grain biochar added is 3000ppm (based on the final lithium manganese iron phosphate product), and the molar ratio of Li:MnFe-PO3-OH is controlled at 1.05:1. The slurry is sand-milled to 0.50um and spray-dried to obtain a mixture.
[0077] 5) The mixture obtained in step 4) is sintered at 600℃ for 20h, and finally crushed to obtain lithium manganese iron phosphate material with a particle size of 0.8-3.0um.
[0078] Example 4
[0079] The preparation steps of the MnFe-PO3-OH precursor are as follows:
[0080] 1) Dissolve Fe(NO3)3 (1mol / L) and Mn(NO3)2 (2.5mol / L) in 100mL of deionized water and stir with a magnetic stirrer for 30min to form solution A;
[0081] According to n(CO3) 2- ) / n(Fe 3+ )=4,n(NaOH) / [n(Mn 2+ )+n(Fe 3+ [ ] = 2, add NaOH and NaHCO3 to water to form solution B;
[0082] After uniformly mixing solutions B and A, the mixture was added to a hydrothermal reactor and reacted at 70°C for 3 hours, maintaining the pH at 9.5-10.5.
[0083] After the reaction was completed, the reaction solution was placed at 90℃ for crystallization for 12 hours, and then filtered, washed and dried to obtain the MnFe-CO3-OH precursor.
[0084] 2) Add the MnFe-CO3-OH precursor obtained in step 1) to water to make a uniformly dispersed slurry, and add 20% KH2PO4 solution to the slurry. Reflux the slurry at 60°C for 3 hours using a reflux device. Then filter, wash and dry the precipitate to obtain the MnFe-PO3-OH precursor.
[0085] The preparation steps of lithium manganese iron phosphate material are as follows:
[0086] 3) Place 100g of brewer's grains into a tube furnace and pyrolyze it at 650℃ under N2 atmosphere for 20h. After grinding and sieving, brewer's grains biochar is obtained.
[0087] 4) The carbon source, the brewer's grain biochar obtained in step 3), the lithium source, and the MnFe-PO3-OH precursor obtained in step 2) are sequentially added to water. The carbon content (calculated as carbon in glucose) is controlled at 1.3% (based on the final lithium manganese iron phosphate product), the amount of brewer's grain biochar added is 4000ppm (based on the final lithium manganese iron phosphate product), and the molar ratio of Li:MnFe-PO3-OH is controlled at 1.1:1. The slurry is sand-milled to 0.45um and spray-dried to obtain a mixture.
[0088] 5) The mixture obtained in step 4) is sintered at 650℃ for 20h, and finally crushed to obtain lithium manganese iron phosphate material with a particle size of 0.8-3.0um.
[0089] Example 5
[0090] The preparation steps of the MnFe-PO3-OH precursor are as follows:
[0091] 1) Dissolve Fe(NO3)3 (1mol / L) and Mn(NO3)2 (3mol / L) in 100mL of deionized water and stir with a magnetic stirrer for 30min to form solution A;
[0092] According to n(CO3) 2- ) / n(Fe 3+ )=4,n(NaOH) / [n(Mn 2+ )+n(Fe 3+ [ ] = 2, add NaOH and NaHCO3 to water to form solution B;
[0093] After uniformly mixing solutions B and A, the mixture was added to a hydrothermal reactor and reacted at 75°C for 3 hours, maintaining the pH at 9.5-10.5.
[0094] After the reaction was completed, the reaction solution was placed at 100℃ for 12 hours to crystallize, and then filtered, washed and dried to obtain the MnFe-CO3-OH precursor.
[0095] 2) Add the MnFe-CO3-OH precursor obtained in step 1) to water to make a uniformly dispersed slurry, and add 30% KH2PO4 solution to the slurry. Reflux the slurry at 60°C for 3 hours using a reflux device. Then filter, wash and dry the precipitate to obtain the MnFe-PO3-OH precursor.
[0096] The preparation steps of lithium manganese iron phosphate material are as follows:
[0097] 3) Place 100g of brewer's grains into a tube furnace and pyrolyze it at 650℃ under N2 atmosphere for 20h. After grinding and sieving, brewer's grains biochar is obtained.
[0098] 4) The carbon source, the brewer's grain biochar obtained in step 3), the lithium source, and the MnFe-PO3-OH precursor obtained in step 2) are sequentially added to water. The carbon content (calculated as carbon in glucose) is controlled at 1.5% (based on the final lithium manganese iron phosphate product), the amount of brewer's grain biochar added is 4000ppm (based on the final lithium manganese iron phosphate product), and the molar ratio of Li:MnFe-PO3-OH is controlled at 1.15:1. The slurry is sand-milled to 0.40um and spray-dried to obtain a mixture.
[0099] 5) The mixture obtained in step 4) is sintered at 700℃ for 20h, and finally crushed to obtain lithium manganese iron phosphate material with a particle size of 0.8-3.0um.
[0100] Comparative Example 1
[0101] The difference from Example 5 is that the MnFe-PO3-OH precursor in Example 5 is replaced with the conventional precursor Mn. 0.75 Fe 0.25 PO4.
[0102] Comparative Example 2
[0103] The difference from Example 5 is that the beer lees in Example 5 are replaced with glucose, a conventional carbon source.
[0104] Conductivity test of lithium manganese iron phosphate material
[0105] The lithium manganese iron phosphate materials prepared in Examples 1-5 and Comparative Examples 1 and 2 were used as positive electrode materials, and lithium iron phosphate positive electrode sheets were prepared with a mass ratio of positive electrode material: conductive agent SP: polyvinylidene fluoride = 8:1:1. The electrodes were assembled into CR2016 button cells and tested at 25°C. The test rates were 0.2C and 1C.
[0106] Table 1 Test Results
[0107] First-efficacy / % 0.2C gram capacity mAh / g 1C gram capacity mAh / g Example 1 94.56 160.8 143.5 Example 2 94.89 161.5 144.2 Example 3 95.37 162.8 145.6 Example 4 94.25 160.6 143.3 Example 5 94.11 160.3 143.1 Comparative Example 1 93.2 158.3 140.2 Comparative Example 2 93.5 159.2 140.8
[0108] As shown in Table 1, the batteries prepared using the lithium manganese iron phosphate materials provided in Examples 1-5 exhibit a first-cycle efficiency greater than 94% and a 1C capacity greater than 143 mAh / g, significantly higher than those in Comparative Examples 1 and 2. This demonstrates that the present invention, using a MnFe-PO3-OH precursor and coating it with brewer's grains and doping it with N and P, can significantly improve the electronic conductivity of lithium manganese iron phosphate, resulting in a high-performance lithium manganese iron phosphate material with promising application prospects.
[0109] Although the present invention has been described in detail above with general descriptions and specific embodiments, modifications or improvements can be made to it, which will be obvious to those skilled in the art. Therefore, all such modifications or improvements made without departing from the spirit of the present invention fall within the scope of protection claimed by the present invention.
Claims
1. A method for preparing a lithium manganese iron phosphate hydroxide precursor, comprising the following steps: S1. Manganese source, iron source, alkali source and carbonate are mixed and subjected to hydrothermal reaction, crystallization, to obtain MnFe-CO3-OH precursor; S2. Add water to the MnFe-CO3-OH precursor obtained in step S1 to form a slurry, add dihydrogen phosphate salts, reflux, filter, wash and dry the resulting precipitate to obtain lithium manganese iron phosphate hydroxide precursor. In step S2, the reflux conditions are: reflux temperature 50-70℃, reflux time 2-4h.
2. The method for preparing the lithium manganese iron phosphate hydroxide precursor according to claim 1, characterized in that: In step S1: The manganese source Mn 2+ Fe with the iron source 3+ molar ratio n (Mn) 2+ ) / n(Fe 3+ (1-4): 1; The alkali source is selected from one or more of NaOH, KOH, and ammonia water; The OH- of the alkaline source - With Mn 2+ and Fe 3+ The total molar ratio n(OH) - ) / [n(Mn 2+ )+n(Fe 3+ [1.5-4] is 1; The carbonate is selected from one or more of NaHCO3, Na2CO3 and K2CO3; The carbonate CO3 2- Fe with the iron source 3+ molar ratio n (CO3) 2- ) / n(Fe 3+ (2-4):
1.
3. The method for preparing the lithium manganese iron phosphate hydroxide precursor according to claim 1 or 2, characterized in that: In step S1: The conditions for the hydrothermal reaction are: reaction temperature of 60-75℃, reaction time of 1-4h, and pH of 9.5-10.
5. The crystallization conditions are: crystallization temperature of 70-100℃ and crystallization time of 10-20h.
4. The method for preparing the lithium manganese iron phosphate hydroxide precursor according to claim 1 or 2, characterized in that: In step S2: The concentration of the slurry is 30%-50%; The dihydrogen phosphate compound is selected from one or more of KH2PO4, NaH2PO4, and NH4H2PO4; The molar ratio of the dihydrogen phosphate salt compound to the MnFe-CO3-OH precursor is (3-5):
1.
5. The lithium manganese iron phosphate hydroxide precursor obtained by the preparation method according to any one of claims 1-4.
6. A lithium manganese iron phosphate material, comprising the following components: the lithium manganese iron phosphate hydroxide precursor as described in claim 5, a carbon source, brewer's grains biochar, and a lithium source.
7. The lithium manganese iron phosphate material according to claim 6, characterized in that: The lithium source contains Li + The molar ratio of the precursor to the lithium manganese iron phosphate hydroxide is (1-1.2):1; The brewer's grain biochar is obtained by pyrolysis of brewer's grain; The amount of brewer's grain biochar added is 2000-4000 ppm.
8. A method for preparing the lithium manganese iron phosphate material according to claim 6 or 7, comprising the following steps: (1) Pyrolysis of brewer's grains yields brewer's grains biochar; (2) Add the carbon source, crushed brewer's grains biochar, lithium source and the lithium manganese iron phosphate precursor of claim 5 to water, and then grind and spray to obtain a mixture. (3) Sinter the mixture obtained in step (2) to obtain lithium manganese iron phosphate material.
9. A lithium-ion battery, comprising a positive electrode and a negative electrode; wherein the material of the positive electrode is the lithium manganese iron phosphate material as described in claim 6 or 7.