A phosphate type positive electrode material, a preparation method thereof, a lithium ion battery and an electrical device
By preparing a mixed slurry of phosphate-type cathode material and reacting it with a lithium source, the density and conductivity issues of lithium iron phosphate cathode material were solved, achieving high-density and high-rate performance phosphate-type cathode material, simplifying the process and reducing costs.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- GUIZHOU CNGR XINGYANG ENERGY STORAGE TECHNOLOGY CO LTD
- Filing Date
- 2024-12-27
- Publication Date
- 2026-06-30
Smart Images
Figure CN122301153A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of lithium-ion battery cathode material technology, specifically to a phosphate-type cathode material and its preparation method, lithium-ion batteries, and related electrical equipment. Background Technology
[0002] Lithium iron phosphate cathode materials have become the preferred choice for power and energy storage batteries due to their advantages such as high safety performance, long cycle life, low price, and environmental friendliness. With the rapid development of the new energy industry and the support of industry policies, the market demand and market share of lithium iron phosphate cathode materials are also increasing.
[0003] Because the theoretical density of lithium iron phosphate (LFP) cathode material is only 3.6 g / cm³, its tap density and compaction density are relatively low, resulting in batteries made using LFP cathode material having a low volumetric energy density. Furthermore, LFP has low electrical conductivity. While carbon-coated small-particle LFP prepared via a liquid-phase method can improve its conductivity and enable high-current charge-discharge, its compaction density and tap density are further reduced, having a more detrimental effect on volumetric energy density. Summary of the Invention
[0004] The purpose of this invention is to provide a method for preparing phosphate-type cathode materials with high tap density and compaction density, excellent rate performance, and simple preparation process.
[0005] To achieve the above objectives, a first aspect of the present invention provides a method for preparing a phosphate-type cathode material, the method comprising the following steps:
[0006] (1) Containing (Fe x M y )3(PO4)2 and (Fe a M b A mixture of HPO4 and lithium source is mixed and reacted to obtain a phosphate-type cathode material precursor.
[0007] Where M is selected from one or more of Mn, V, Ti, Mg, Ca, Zn, Cu, Co, Ni, Al, Ga, In, La, Cr, and W, 0 < x ≤ 1, 0 ≤ y < 1, 0.9 < x + y < 1.1; 0 < a ≤ 1, 0 ≤ b < 1, 0.9 < a + b < 1.1;
[0008] (2) The phosphate-type cathode material precursor is subjected to sand milling, drying and sintering to obtain the phosphate-type cathode material.
[0009] In some embodiments, the mixed slurry contains (Fe x M y )3(PO4)2 and (Fe a Mb The molar ratio of HPO4 is 1:0.5-2.
[0010] In some implementations, x = a.
[0011] In some implementations, y = b.
[0012] In some embodiments, the molar ratio of lithium in the lithium source to iron in the mixed slurry is 1.02-1.10:1.
[0013] In some embodiments, the lithium source is selected from at least one of lithium carbonate, lithium hydroxide, and amorphous lithium phosphate.
[0014] In some embodiments, the temperature at which the mixed slurry reacts with the lithium source is 80-100°C and the reaction time is 2-10 hours.
[0015] In some embodiments, the method further includes: before step (1), mixing and reacting an iron source with phosphoric acid to obtain the mixed slurry; wherein the iron source is a slurry containing elemental iron and ferric iron.
[0016] In some embodiments, the trivalent iron source includes at least one of iron hydroxide, iron oxide, iron carbonate, iron manganese oxide, and iron manganese carbonate.
[0017] In some embodiments, the molar ratio of the elemental iron to the trivalent iron source is 1:1-2.
[0018] In some embodiments, the molar ratio of elemental iron to phosphoric acid is 1:2.1-3.1.
[0019] In some embodiments, the mass concentration of the phosphoric acid is 40%-85%.
[0020] In some embodiments, the reaction temperature of the iron source slurry with phosphoric acid is 45-100°C.
[0021] In some embodiments, the phosphate-type cathode material precursor described in step (2) is also mixed with a carbon source.
[0022] A second aspect of the present invention provides a phosphate-type cathode material prepared by the method described in the first aspect above.
[0023] A third aspect of the present invention provides a lithium-ion battery comprising the lithium-ion battery cathode material as described in the second aspect above.
[0024] A fourth aspect of the present invention provides an electrical device comprising a lithium-ion battery as described in the third aspect above.
[0025] Compared with the prior art, the technical solution provided by the present invention has at least the following advantages:
[0026] The method for preparing phosphate-type cathode materials provided by this invention uses materials containing (Fe) x M y )3(PO4)2 and (Fe a M b The phosphate-type cathode material prepared by reacting the HPO4 mixture with a lithium source not only has high tap density and compaction density, but also excellent rate performance.
[0027] The method for preparing phosphate-type cathode materials provided by this invention does not introduce other impurities during the entire process, does not require filtration and washing, simplifies the process route, and reduces costs.
[0028] The features and advantages of the present invention will be described below, or will become apparent from the following description. Attached Figure Description
[0029] Figure 1 This is a SEM image of the phosphate-type cathode material prepared in Example 1 of this invention;
[0030] Figure 2 This is the electrochemical performance test curve of the phosphate-type cathode material prepared in Example 1 of this invention. Detailed Implementation
[0031] 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.
[0032] As mentioned above, a first aspect of the present invention provides a method for preparing a phosphate-based cathode material, the method comprising the following steps:
[0033] (1) Containing (Fe x M y )3(PO4)2 and (Fe a M b A mixture of HPO4 and lithium source is mixed and reacted to obtain a phosphate-type cathode material precursor.
[0034] Where M is selected from one or more of Mn, V, Ti, Mg, Ca, Zn, Cu, Co, Ni, Al, Ga, In, La, Cr, and W, 0 < x ≤ 1, 0 ≤ y < 1, 0.9 < x + y < 1.1; 0 < a ≤ 1, 0 ≤ b < 1, 0.9 < a + b < 1.1;
[0035] (2) The phosphate-type cathode material precursor is subjected to sand milling, drying and sintering to obtain the phosphate-type cathode material.
[0036] This invention uses (Fe) x M y )3(PO4)2 and (Fe a M b The phosphate-type cathode material prepared by reacting a mixture of HPO4 slurry with a lithium source has high tap density, high tap density and excellent rate performance.
[0037] The underlying principle is speculated to be: using (Fe) a M b Phosphate-type cathode materials prepared with HPO4 exhibit small primary particles and dense secondary particles, resulting in high tap density and high rate capability, but relatively low compaction density. x M y The primary particles of the phosphate-type cathode material prepared by 3(PO4)2 are large and the tap density is low. Mixing it with cathode material with smaller primary particles can improve the compaction density.
[0038] In addition, (Fe) x M y Lithium iron phosphate prepared by 3(PO4)2 also has crystal facet selectivity, which can suppress the growth of lithium ion intercalation and deintercalation, reduce the impact of poor rate performance caused by the presence of large primary particles, and thus ensure that lithium iron phosphate has excellent rate performance.
[0039] In the general chemical formula provided by this invention, the value of x can be, for example, any value between 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, or 0-1; the value of y can be, for example, any value between 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, or 0-1; the value of a can be, for example, any value between 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, or 0-1; and the value of b can be, for example, any value between 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, or 0-1.
[0040] In some embodiments, the mixed slurry contains (Fex M y )3(PO4)2 and (Fe a M b The molar ratio of HPO4 is 1:0.5-2, for example, it can be any ratio between 1:0.5, 1:1, 1:1.5, 1:2 or 1:0.5-2.
[0041] (Fe x M y )3(PO4)2 and (Fe a M b When the molar ratio of HPO4 is within this range, the prepared lithium iron phosphate exhibits excellent tap density, compaction density, and rate performance.
[0042] In some implementations, x = a.
[0043] In some implementations, y = b.
[0044] In some embodiments, the molar ratio of lithium in the lithium source to iron in the mixed slurry is 1.02-1.10:1, for example, it can be any ratio between 1.02:1, 1.05:1, 1.08:1, 1.10:1 or 1.02-1.10:1.
[0045] In some embodiments, the lithium source is selected from at least one of lithium carbonate, lithium hydroxide, and amorphous lithium phosphate.
[0046] According to a preferred embodiment of the present invention, the lithium source is amorphous lithium phosphate.
[0047] The amorphous lithium phosphate described in this invention refers to amorphous lithium phosphate. This material is used as a lithium source because amorphous lithium phosphate has a smaller particle size, more thorough mixing of Li, Fe, and P elements, and a more uniform product composition.
[0048] In some embodiments, the reaction temperature between the mixed slurry and the lithium source is 80-100°C, for example, it can be any value between 80°C, 82°C, 84°C, 86°C, 88°C, 90°C, 92°C, 94°C, 96°C, 98°C, 100°C or 80-100°C; the reaction time is 2-10h, for example, it can be any value between 2h, 3h, 4h, 5h, 6h, 7h, 8h, 9h, 10h or 2-10h.
[0049] By controlling the temperature of the reaction between the mixed slurry and the lithium source within the range required by this invention, a phosphate-type cathode material precursor with smaller primary particles can be prepared, thereby preparing a phosphate-type cathode material with smaller primary particles.
[0050] In some embodiments, the method further includes: before step (1), mixing and reacting an iron source with phosphoric acid to obtain the mixed slurry; wherein the iron source is a slurry containing elemental iron and ferric iron.
[0051] This invention uses elemental iron as a reducing agent and ferric iron as an oxidizing agent to generate (Fe) under acidic conditions. x M y )3(PO4)2 and (Fe a M b The HPO4 system was used to prepare phosphate cathode materials with better performance.
[0052] According to some preferred embodiments of the present invention, the entire process from elemental iron to the generation of the cathode material does not introduce other impurities, does not require filtration and washing, and generates (Fe) x M y )3(PO4)2 and (Fe a M b The process for mixing HPO4 requires only one step, simplifying the process route and reducing costs.
[0053] The present invention does not impose any particular limitation on the size or form of the elemental iron. Those skilled in the art can choose from forms known in the art. For example, the elemental iron is iron powder and / or iron block. The present invention will not be described in detail here, and those skilled in the art should not understand it as a limitation of the present invention.
[0054] In some embodiments, the trivalent iron source includes at least one of iron hydroxide, iron oxide, iron carbonate, iron manganese oxide, and iron manganese carbonate.
[0055] In some embodiments, the molar ratio of the elemental iron to the trivalent iron source is 1:1-2, for example, it can be any ratio between 1:1, 1:1.5, 1:2 or 1:1-2.
[0056] In some embodiments, the molar ratio of elemental iron to phosphoric acid is 1:2.1-3.1, for example, it can be 1:2.1, 1:2.2, 1:2.3, 1:2.4, 1:2.5, 1:2.6, 1:2.7, 1:2.8, 1:2.9, 1:3.0, 1:3.1, or any value between 1:2.1 and 3.1.
[0057] By controlling the molar ratio of elemental iron and phosphoric acid under these conditions, the hydrolysis of ferric iron and the oxidation of ferrous iron can be suppressed, producing a product containing (Fe2+) phosphoric acid. x M y )3(PO4)2 and (Fe a M bA phosphate-type cathode material with higher tap density and compaction density and superior rate performance was prepared by mixing HPO4 slurry.
[0058] In some embodiments, the mass concentration of the phosphoric acid is 40%-85%, for example, it can be 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, or any value between 40% and 85%.
[0059] In some embodiments, the reaction temperature of the iron source slurry with phosphoric acid is 45-100°C, for example, it can be 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, 95°C, 100°C, or any value between 45-100°C.
[0060] In some embodiments, the phosphate-type cathode material precursor described in step (2) is also mixed with a carbon source.
[0061] Optionally, the carbon source is selected from at least two of polyethylene glycol, sucrose, glucose, and polycarboxylic acid polymers.
[0062] Optionally, the carbon source is a combination of polyethylene glycol and glucose. Optionally, the mass ratio of polyethylene glycol to glucose is 1:0.5-2. By using a composite carbon source under these conditions, the conductivity of lithium iron phosphate can be further improved.
[0063] In some embodiments, the particle size D50 of the phosphate-type cathode material precursor after milling is controlled to be 0.1-0.3 μm. Milling within this range is beneficial for improving the tap density of the phosphate-type cathode material.
[0064] Optionally, the drying method described in step (2) is spray drying. Spray drying is beneficial for granulation of phosphate cathode material precursors, forming porous secondary spherical particles.
[0065] Optionally, the sintering conditions in step (2) include: a temperature of 680-760℃ and a time of 8-24h.
[0066] Optionally, the sintering is carried out in the presence of a protective atmosphere selected from at least one of nitrogen, carbon dioxide, and carbon monoxide.
[0067] As previously stated, a second aspect of the present invention provides a phosphate-type cathode material prepared by the method described in the first aspect.
[0068] As previously stated, a third aspect of the present invention provides a lithium-ion battery comprising the lithium-ion battery cathode material as described in the second aspect above.
[0069] This invention does not impose any particular limitation on the specific method for preparing the lithium-ion battery. Those skilled in the art can choose from known techniques. For example, the above-mentioned positive electrode material, conductive carbon black, and binder are mixed and coated onto aluminum foil to form a positive electrode sheet; the positive electrode sheet, negative electrode sheet, electrolyte, and separator are then assembled into the battery. This invention will not be described in detail here, and those skilled in the art should not construe this as a limitation of the invention.
[0070] As previously described, a fourth aspect of the present invention provides an electrical device including a lithium-ion battery as described in the third aspect above.
[0071] The present invention will be described in detail below through examples. In the following examples, unless otherwise specified, all raw materials used are commercially available products.
[0072] Example 1
[0073] S1: Mix iron powder and ferric iron source to form an iron source slurry; mix and react the iron source with phosphoric acid to form a mixed slurry;
[0074] S2: First, prepare the lithium source slurry (i.e., add water to the lithium salt and stir to form a uniform slurry). Add the prepared lithium source to the mixed slurry obtained in step S1. After adding, continue stirring for 30 minutes. Then, heat to the specified temperature to carry out the reaction. Keep the temperature and let it cool naturally after the reaction is completed to obtain a mixed system containing phosphate-type cathode material precursor.
[0075] S3: Add a carbon source to the mixed system containing the phosphate-type cathode material precursor obtained in step S2, disperse it evenly, transfer it to a sand mill, then spray dry the material, and sinter it under a protective atmosphere of nitrogen to obtain a carbon-coated phosphate-type cathode material.
[0076] The types and amounts of raw materials involved, and the content of Fe in the mixed slurry. x M y )3(PO4)2 and (Fe a M b The ratios, types, and process parameters of HPO4 are shown in Table 1.
[0077] Examples 2-6
[0078] The process was basically the same as in Example 1, except for the types and amounts of raw materials involved, and the amount of Fe in the mixed slurry. x M y )3(PO4)2 and (Fe a M b The ratio and type of HPO4, as well as other process parameters, vary, as shown in Table 1.
[0079] A carbon-coated phosphate cathode material was prepared.
[0080] Table 1 Reaction conditions of Examples 1-6
[0081]
[0082] Example 7
[0083] The process is basically the same as in Example 1, except that the lithium source in step S2 is directly added to the mixed slurry obtained in step S1 without the lithium source slurry adjustment operation, and then the operations of steps S2 and S3 are continued.
[0084] A carbon-coated phosphate cathode material was prepared.
[0085] Example 8:
[0086] The process is basically the same as in Example 1, except that in step S2, the reaction temperature of the lithium source after slurry preparation and the mixed slurry is 60°C, and then the subsequent operations of step S2 and the operation of step S3 are continued.
[0087] A carbon-coated phosphate cathode material was prepared.
[0088] Example 9
[0089] The process is basically the same as in Example 1, except that in step S1, after the reaction to obtain the mixed slurry, it is allowed to stand for 48 hours; then the mixed slurry after standing is continued to undergo the operations of steps S2 and S3.
[0090] A carbon-coated phosphate cathode material was prepared.
[0091] Example 10
[0092] The process was basically the same as in Example 1, except that a titanium source (tetrabutyl titanate, Ti / Fe molar ratio = 1:252) was added to the iron source slurry in S1 to obtain an iron source slurry containing a titanium source; the iron source slurry containing a titanium source was mixed and reacted with phosphoric acid to obtain a mixed slurry; and then the mixed slurry was further processed in steps S2 and S3.
[0093] A carbon-coated phosphate cathode material was prepared.
[0094] Comparative Example 1
[0095] The difference from Example 1 is that lithium iron phosphate is prepared using ferrous phosphate. The specific process is as follows:
[0096] S1: Dissolve ferrous sulfate in deoxygenated pure water to obtain a ferrous solution; dissolve ammonium dihydrogen phosphate in deoxygenated pure water to obtain an ammonium dihydrogen phosphate solution.
[0097] Ferrous solution was slowly added to ammonium dihydrogen phosphate solution at a ratio of Fe:P = 1.51:1 to form an iron-phosphorus solution. Nitrogen gas was simultaneously introduced to inhibit the oxidation of ferrous iron. The reaction temperature was controlled at 45°C and the pH was adjusted. Ferrous phosphate precipitate was obtained by aging.
[0098] S2: The ferrous phosphate formed in the reaction in S1 is filtered, washed to remove impurities, and dried to obtain ferrous phosphate dried product. The ferrous phosphate dried product, amorphous lithium phosphate and lithium carbonate are mixed with water in a molar ratio of 1:1:0.025 to obtain a mixed slurry.
[0099] S3: Add glucose and polyethylene glycol to the mixed slurry at 6% and 8% of the total mass of dried ferrous phosphate, amorphous lithium phosphate, and lithium carbonate, respectively. After dispersing evenly, transfer to a sand mill. After the particle size reaches the set range of 0.1-0.3μm, discharge the material and spray dry it. Sinter at 740℃ for 8 hours under a nitrogen atmosphere to obtain carbon-coated phosphate cathode material.
[0100] The physical and chemical properties of the phosphate-type cathode materials obtained in the aforementioned embodiments and comparative examples were tested, and the specific results are shown in Table 2.
[0101] Compacted density test method: The compacted density of phosphate-type cathode material was tested using a Sansi Zongheng UIM 7305 compacted density meter. The specific test process is as follows: 1g of phosphate-type cathode material was weighed on a balance and placed in a clean mold with a hole radius of 6.5mm. The mold was then placed on the pressure plate of the equipment, and the test pressure was set to 3T.
[0102] Test method for tap density: According to the national standard GB / T 21354-2008, the tap density of phosphate-type cathode materials is tested. Specifically, the powder is placed in a graduated glass cylinder, the cylinder is raised to a certain height, and then dropped freely. This process is repeated multiple times until the volume of the powder no longer decreases. The tap density of the powder is obtained by dividing the mass of the powder by the volume of the powder after tapping.
[0103] Span value testing method: The particle size distribution is measured using a laser particle size analyzer to obtain the relevant D95, D5, and D50 data, and the Span95 is calculated using the following formula:
[0104] Span95=(D95-D5) / D50
[0105] Electrochemical testing method: A slurry was prepared by mixing phosphate-based positive electrode material with conductive carbon black and PVDF (polyvinylidene fluoride) binder in an 8:1:1 ratio. This slurry was coated onto aluminum foil to form the positive electrode sheet. A lithium metal sheet was used as the negative electrode sheet. The electrolyte was a 1 mol / L LiPF6 / EC:DMC:EMC solution (volume ratio 1:1:1). The battery casing, positive and negative electrodes, separator, spring contacts, and gaskets were assembled into a coin cell in a vacuum glove box. A Blue Electric testing system was used to test the 0.1C and 1C currents at 2.0-3.75V (the specific capacity used for current calculation was 170 mAh g). -1 Charge and discharge tests.
[0106] The present invention provides, by way of example, scanning electron microscope (SEM) images and electrochemical performance diagrams of the carbon-coated phosphate cathode material prepared in Example 1, as shown below. Figure 1 and Figure 2 As shown. From Figure 1 As can be seen, the primary particles are small, and there is good melting between the primary particles, which promotes internal melting and ensures both vibratory and compacted density. From Figure 2 As can be seen, the synthesized lithium iron phosphate exhibits good electrochemical performance, with a 1C / 0.1C ratio ≥ 95%, demonstrating excellent rate capability.
[0107] Table 2 Physical and electrochemical properties of cathode materials
[0108]
[0109] The results above show that the phosphate-type cathode material prepared by the technical solution provided by this invention has high tap density, high tap density and excellent rate performance without reducing capacity. Furthermore, the preparation method of the phosphate-type cathode material provided by this invention does not introduce other impurities in the entire process, does not require filtration and washing, simplifies the process route and reduces costs.
[0110] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.
Claims
1. A method for preparing a phosphate-based cathode material, characterized in that, The method includes the following steps: (1) a mixed slurry containing (Fe x M y )3(PO4)2 and (Fe a M b )HPO4 is mixed with a lithium source to obtain a phosphate-type positive electrode material precursor; Where M is selected from one or more of Mn, V, Ti, Mg, Ca, Zn, Cu, Co, Ni, Al, Ga, In, La, Cr, and W, 0 < x ≤ 1, 0 ≤ y < 1, 0.9 < x + y < 1.1; 0 < a ≤ 1, 0 ≤ b < 1, 0.9 < a + b < 1.1; (2) The phosphate-type cathode material precursor is subjected to sand milling, drying and sintering to obtain the phosphate-type cathode material.
2. The method according to claim 1, characterized in that, In the mixed slurry (Fe x M y )3(PO4)2 and (Fe a M b The molar ratio of HPO4 is 1:0.5-2; And / or, x = a; And / or, y = b.
3. The method according to claim 1 or 2, characterized in that, The molar ratio of lithium in the lithium source to iron in the mixed slurry is 1.02-1.10:1; And / or, the lithium source is selected from at least one of lithium carbonate, lithium hydroxide, and amorphous lithium phosphate; And / or, the temperature at which the mixed slurry reacts with the lithium source is 80-100℃, and the reaction time is 2-10h.
4. The method according to claim 1 or 2, characterized in that, The method further includes: before step (1), mixing and reacting the iron source with phosphoric acid to obtain the mixed slurry; The iron source is a slurry containing elemental iron and trivalent iron.
5. The method according to claim 4, characterized in that, The trivalent iron source includes at least one of iron hydroxide, iron oxide, iron carbonate, iron manganese oxide, and iron manganese carbonate.
6. The method according to claim 4, characterized in that, The molar ratio of the elemental iron to the trivalent iron source is 1:1-2; And / or, the molar ratio of the elemental iron to the phosphoric acid is 1:2.1-3.1; And / or, the mass concentration of the phosphoric acid is 40%-85%; And / or, the reaction temperature of the iron source slurry with phosphoric acid is 45-100℃.
7. The method according to claim 1 or 2, characterized in that, The phosphate-type cathode material precursor described in step (2) is also mixed with a carbon source.
8. The phosphate-type cathode material prepared by the method according to any one of claims 1-7.
9. A lithium-ion battery, characterized in that, Including the lithium-ion battery cathode material as described in claim 8.
10. An electrical-related device, characterized in that, Including the lithium-ion battery as described in claim 9.