A method and apparatus for preparing lithium manganese iron phosphate from waste lithium manganese oxide and waste lithium iron phosphate.

Abstract

This invention relates to the field of waste battery recycling technology, specifically disclosing a method for preparing lithium manganese iron phosphate from waste lithium manganese oxide and waste lithium iron phosphate, comprising the following steps: solid-phase mixing of waste lithium manganese oxide (LiMn2O4) and lithium phosphate (Li3PO4) to obtain a first mixture; using phosphoric acid (H3PO4) as a medium, milling the first mixture with a sand mill; filtering the slurry to obtain lithium manganese phosphate (LiMnPO4); measuring the XRD of the lithium manganese phosphate, and if impurities are present, continuing to use fresh phosphoric acid as a medium to mill the mixture and filter the slurry again. The automatic trimming mechanism for exhaust valve box covers provided by this invention offers a new method that solves the recycling problem of waste lithium manganese oxide and waste lithium iron phosphate, while simultaneously generating lithium manganese iron phosphate, thus recycling waste materials, conforming to the national green environmental protection concept, and saving resources and energy.

Description

Technical Field

[0001] This invention relates to the field of waste battery recycling technology, specifically to a method and apparatus for preparing lithium manganese iron phosphate from waste lithium manganese oxide and waste lithium iron phosphate. Background Technology

[0002] Spinel lithium manganese oxide, first synthesized by Hunter in 1981, is a cathode material with three-dimensional lithium-ion channels. It boasts advantages such as low cost, high potential, environmental friendliness, and high safety performance, and is widely used in electric bicycles, 3C digital products, and other fields. Olivine-structured lithium iron phosphate, after extensive research by Goodenough, is currently widely used in automobiles, energy storage, and other fields due to its advantages such as long cycle life, high safety, and low cost. After the end of the lifespan of lithium-ion batteries, green recycling is generally achieved through lithium extraction. However, for lithium manganese oxide and lithium iron phosphate batteries, only lithium has recycling value; the extraction of manganese and iron is not economically viable. Therefore, the market price of waste lithium manganese oxide and waste lithium iron phosphate is generally very low.

[0003] Due to the scarcity of nickel and cobalt, ternary lithium batteries are expensive and have low safety. As a result, lithium manganese iron phosphate (LFP) is gradually replacing ternary lithium batteries in the automotive battery field. Directly preparing LFP from spent lithium manganese oxide and spent lithium iron phosphate from waste batteries not only solves the environmental and economic problems of recycling spent lithium manganese oxide and spent lithium iron phosphate, but also yields the LFP needed for automotive batteries. Therefore, realizing this technology is a challenging problem that needs to be solved. Summary of the Invention

[0004] The purpose of this invention is to provide an automatic trimming mechanism for exhaust valve box covers to overcome the above-mentioned shortcomings in the prior art.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] A method for preparing lithium manganese iron phosphate from waste lithium manganese oxide and waste lithium iron phosphate, including a sand milling device.

[0007] Includes the following steps:

[0008] Waste lithium manganese oxide (LiMn2O4) and lithium phosphate (Li3PO4) were mixed in a solid phase to obtain a first mixture;

[0009] The first mixture was milled using phosphoric acid (H3PO4) as a medium and a sand milling device.

[0010] The slurry was filtered to obtain lithium manganese phosphate (LiMnPO4).

[0011] The XRD of the lithium manganese phosphate was determined. If there was an impurity phase, fresh phosphoric acid was used as the medium. The mixture was then further milled and filtered into a slurry using a sand mill until high-purity lithium manganese phosphate was finally obtained.

[0012] High-purity lithium manganese phosphate is mixed with waste lithium iron phosphate and a carbon source to obtain a second mixture;

[0013] The second mixture was subjected to solid-state sintering at 650~750℃ to obtain LMFP / C.

[0014] Furthermore, the characteristic is that the molar ratio of lithium manganese oxide, lithium phosphate, and phosphoric acid satisfies 3:1:5.

[0015] Furthermore, the carbon source is characterized by being one or more of the following: sucrose, glucose, fructose, citric acid, phenolic resin, polyvinyl alcohol, polyethylene glycol, starch, carbon black, acetylene black, graphite, graphene, and conductive carbon nanotubes.

[0016] An apparatus for preparing lithium manganese iron phosphate from waste lithium manganese oxide and waste lithium iron phosphate, and a method for preparing lithium manganese iron phosphate from the aforementioned waste lithium manganese oxide and waste lithium iron phosphate, characterized in that the grinding equipment includes an equipment body, a grinding cylinder is provided on the equipment body, a grinding cavity is opened inside the grinding cylinder, a rotor is provided inside the grinding cavity, the interior of the grinding cylinder is filled with abrasive, a drive source is provided at the input end of the rotor, and grinding components are provided outside the rotor;

[0017] The grinding component includes a grinding disc and a rotating cylinder connected to the rotor. The grinding disc is responsible for driving the abrasive to undergo intense collisions and friction within the grinding chamber to grind the first mixture.

[0018] A driving component is provided on the inner side of the sand grinding disc. The driving component includes a driving block. The sand grinding disc is in contact with the driving block. The driving component is responsible for driving the driving block to move when it rotates with the driving source, so that multiple sand grinding discs extend outward intermittently in sequence.

[0019] Furthermore, a reciprocating block is provided at the bottom of the grinding disc, and a first inclined groove and a second inclined groove are respectively opened on the reciprocating block, and a pair of driving blocks are respectively on the first inclined groove and the second inclined groove.

[0020] Furthermore, the driving component also includes a first driving bar and a second driving bar that are slidably connected to the outer wall of the rotor. The ends of the first driving bar and the second driving bar are each provided with a first irregular ring. The rotor is also movably fitted with a second irregular ring. The first irregular ring and the second irregular ring are adapted to each other, and the first irregular ring moves relative to the second irregular ring when working.

[0021] Furthermore, the first and second irregular rings are provided with crests and troughs. During the rotation of the irregular rings, the first and second drive bars reciprocate by contacting the second irregular ring, and the sand grinding disc is driven to extend outward by the drive block.

[0022] Furthermore, a telescopic rod is provided between the rotor and the reciprocating block. The telescopic rod includes a hollow rod and a piston rod. A strong spring is fixedly connected between the bottom of the piston rod and the inner wall of the hollow rod. A slot is provided on the first drive bar, and the telescopic rod is located inside the slot.

[0023] In the above technical solution, the automatic trimming mechanism for the exhaust valve box cover provided by the present invention has the following advantages:

[0024] This invention provides a novel method that solves the recycling problem of waste lithium manganese oxide and waste lithium iron phosphate, while simultaneously generating lithium manganese iron phosphate. This method recycles and utilizes waste materials, aligning with the national green and environmentally friendly concept, and saving resources and energy. The method is simple, effective, and low-cost, and has broad market prospects.

[0025] When the grinding disc moves outward, it forces the surrounding abrasive to move. The abrasive not only changes its original trajectory and applies compressive and cutting forces to the material, but also indirectly causes the abrasive around the grinding disc to change its movement by changing its trajectory. This allows the material on the periphery to also experience compressive forces that were not there before, making the movement of the abrasive inside the grinding chamber more full and uniform, and ultimately improving the grinding efficiency of the abrasive on the material.

[0026] It should be understood that the foregoing general description and the following detailed description are exemplary and illustrative only, and are not intended to limit this disclosure.

[0027] This application provides an overview of various implementations or examples of the technology described in this disclosure, and is not a full disclosure of the entire scope or all features of the disclosed technology. Attached Figure Description

[0028] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this invention. For those skilled in the art, other drawings can be obtained based on these drawings.

[0029] Figure 1 This is a schematic diagram of the overall external structure provided in an embodiment of the present invention;

[0030] Figure 2 This is a schematic diagram of the internal structure of the grinding cylinder provided in an embodiment of the present invention;

[0031] Figure 3 This is a schematic diagram of the drum and rotor separation structure provided in an embodiment of the present invention;

[0032] Figure 4 This is a schematic diagram of the drive component structure provided in an embodiment of the present invention;

[0033] Figure 5 This is a schematic diagram of the structure below the grinding disc provided in an embodiment of the present invention;

[0034] Figure 6 This is a schematic diagram of the structure of the first drive bar and the second drive bar provided in an embodiment of the present invention;

[0035] Figure 7 Provided for embodiments of the present invention Figure 6 A magnified structural diagram at point A.

[0036] Explanation of reference numerals in the attached figures:

[0037] 1. Equipment body; 2. Grinding cylinder; 21. Abrasive feeding cylinder; 22. Feed pipe; 23. Sealing disc; 3. Rotor; 4. Grinding components; 41. Grinding disc; 42. Rotary cylinder; 5. Drive components; 51. Drive block; 52. Reciprocating block; 53. First inclined groove; 54. Second inclined groove; 55. First drive bar; 56. Second drive bar; 57. First irregular ring; 58. Second irregular ring; 59. Crest section; 510. Valley section. Detailed Implementation

[0038] To make the objectives, technical solutions, and advantages of the embodiments of this disclosure clearer, the technical solutions of the embodiments of this disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this disclosure. All other embodiments obtained by those skilled in the art based on the described embodiments of this disclosure without creative effort are within the scope of protection of this disclosure.

[0039] A method for preparing lithium manganese iron phosphate from waste lithium manganese oxide and waste lithium iron phosphate, including a sand milling device.

[0040] Includes the following steps:

[0041] Waste lithium manganese oxide (LiMn2O4) and lithium phosphate (Li3PO4) were mixed in a solid phase to obtain a first mixture;

[0042] The first mixture was milled using phosphoric acid (H3PO4) as a medium and a sand milling device.

[0043] The slurry was filtered to obtain lithium manganese phosphate (LiMnPO4).

[0044] The XRD of the lithium manganese phosphate was determined. If there was an impurity phase, fresh phosphoric acid was used as the medium. The mixture was then further milled and filtered into a slurry using a sand mill until high-purity lithium manganese phosphate was finally obtained.

[0045] High-purity lithium manganese phosphate is mixed with waste lithium iron phosphate and a carbon source to obtain a second mixture;

[0046] The second mixture was subjected to solid-state sintering at 650~750℃ to obtain LMFP / C.

[0047] The molar ratio of lithium manganese oxide, lithium phosphate, and phosphoric acid is 3:1:5.

[0048] The carbon source is one or more of the following: sucrose, glucose, fructose, citric acid, phenolic resin, polyvinyl alcohol, polyethylene glycol, starch, carbon black, acetylene black, graphite, graphene, and conductive carbon nanotubes.

[0049] Example 1

[0050] (1) Solid-phase mixing of waste lithium manganese oxide (LiMn2O4) and lithium phosphate (Li3PO4) yields a first mixture with a molar ratio of 3:1 between lithium manganese oxide and lithium phosphate. (2) Using phosphoric acid (H3PO4) as the medium, the first mixture is milled in a vertical mill with a molar ratio of 3:1:5 between lithium manganese oxide, lithium phosphate, and phosphoric acid. The mill is vertical with a zirconium bead diameter of 0.5 mm, and the milled lithium phosphate can achieve a particle size of 0.5 μm. The reaction equation for lithium manganese oxide, lithium phosphate, and phosphoric acid is: 12LiMn2O4 + 4Li3PO4 + 20H3PO4 = 24LiMnPO4 + 30H2O + 9O2↑. (3) Filter the slurry to obtain lithium manganese phosphate (LiMnPO4); (4) Measure the XRD of the lithium manganese phosphate. If there is an impurity phase, continue to use fresh phosphoric acid as the medium and continue to mill and filter the mixture with a sand mill until high-purity lithium manganese phosphate is finally obtained; (5) Mix the high-purity lithium manganese phosphate with waste lithium iron phosphate and sucrose to obtain a second mixture; (6) Sinter the second mixture at 650°C to obtain lithium manganese iron phosphate / carbon composite LMFP / C. The reaction equation of lithium manganese phosphate and lithium iron phosphate is: .

[0051] The particle size of the lithium manganese iron phosphate material was tested, showing a D50 of 1.1 μm. The powder resistivity of the lithium manganese iron phosphate material was tested to be 92 Ω·cm. Formation tests were conducted on a coin cell assembled with this lithium manganese iron phosphate material. The initial charge capacity at 0.1C was 156.1 mAh / g, the initial discharge capacity at 0.1C was 149.2 mAh / g, the initial efficiency was 95.6%, the specific capacity at 1C was 135.4 mAh / g, and the ratio of 1C to 0.1C was 90.8%.

[0052] Example 2

[0053] (1) Solid-phase mixing of waste lithium manganese oxide (LiMn2O4) and lithium phosphate (Li3PO4) yields a first mixture with a molar ratio of 3:1 between lithium manganese oxide and lithium phosphate. (2) Using phosphoric acid (H3PO4) as the medium, the first mixture is milled in a vertical mill with a molar ratio of 3:1:5 between lithium manganese oxide, lithium phosphate, and phosphoric acid. The mill is horizontal with a zirconium bead diameter of 1 mm, and the milled lithium phosphate can reach a particle size of 1 μm. The reaction equation for lithium manganese oxide, lithium phosphate, and phosphoric acid is: 12LiMn2O4 + 4Li3PO4 + 20H3PO4 = 24LiMnPO4 + 30H2O + 9O2↑. (3) Filter the slurry to obtain lithium manganese phosphate (LiMnPO4); (4) Measure the XRD of the lithium manganese phosphate. If there is an impurity phase, continue to use fresh phosphoric acid as the medium and continue to mill and filter the mixture with a sand mill until high-purity lithium manganese phosphate is finally obtained; (5) Mix the high-purity lithium manganese phosphate with waste lithium iron phosphate and sucrose to obtain a second mixture; (6) Sinter the second mixture at 750°C to obtain lithium manganese iron phosphate / carbon composite LMFP / C. The reaction equation of lithium manganese phosphate and lithium iron phosphate is: .

[0054] The particle size analysis of the lithium manganese iron phosphate (LFP) material showed a D50 of 1.0 μm. The powder resistivity of the LFP material was 98 Ω·cm. Formation tests were conducted on a coin cell assembled with this LFP material. The initial charge capacity at 0.1C was 155.8 mAh / g, the initial discharge capacity at 0.1C was 148.7 mAh / g, the initial efficiency was 95.4%, and the specific capacity at 1C was 134.1 mAh / g. The ratio of 1C to 0.1C was 90.2%.

[0055] Comparative Example 1

[0056] (1) Solid-state mixing of waste lithium manganese oxide (LiMn2O4) and lithium phosphate (Li3PO4) yields a first mixture with a molar ratio of 3:1 between lithium manganese oxide and lithium phosphate. (2) Adding phosphoric acid (H3PO4) to the first mixture and stirring the mixture, with a molar ratio of 3:1:5 between lithium manganese oxide, lithium phosphate, and phosphoric acid. (3) Filtering the slurry and drying it. (4) Continuing to react the dried material with phosphoric acid, filtering the slurry, drying it, and measuring the XRD of the solid. (5) Mixing the solid with waste lithium iron phosphate and sucrose yields a second mixture. (6) Solid-state sintering of the second mixture at 650°C yields the lithium manganese iron phosphate / carbon composite LMFP / C.

[0057] The XRD of the solid was tested as follows Figure 1As shown, the solid is a mixture of lithium manganese phosphate and lithium manganese oxide. This is mainly because, without a sand mill, lithium manganese phosphate is only formed on the surface of lithium manganese oxide. The surface lithium manganese phosphate then prevents the internal lithium manganese oxide from reacting to form lithium manganese phosphate. Without a sand mill, even with repeated additions of phosphoric acid, lithium manganese oxide cannot be completely converted to lithium manganese phosphate, resulting in impure lithium iron phosphate and poor performance. The particle size of the lithium manganese iron phosphate material was tested, showing a D50 of 1.1 μm. The powder resistivity of the lithium manganese iron phosphate material was tested to be 92 Ω·cm. Formation tests were conducted on a coin cell assembled with this lithium manganese iron phosphate material. The initial charge at 0.1C was 140.5 mAh / g, the initial discharge at 0.1C was 121.5 mAh / g, the initial efficiency was 86.5%, the 1C specific capacity was 106.7 mAh / g, and 1C / 0.1C = 87.8%.

[0058] Comparative Example 2

[0059] (1) Solid-phase mixing of waste lithium manganese oxide (LiMn2O4) and lithium phosphate (Li3PO4) yields a first mixture with a molar ratio of 3:1 between lithium manganese oxide and lithium phosphate. (2) Using phosphoric acid (H3PO4) as the medium, the first mixture is milled in a vertical mill with a molar ratio of 3:1:5 between lithium manganese oxide, lithium phosphate, and phosphoric acid. The mill is horizontal with a zirconium bead diameter of 1 mm, and the milled lithium phosphate can reach a particle size of 1 μm. The reaction equation for lithium manganese oxide, lithium phosphate, and phosphoric acid is: 12LiMn2O4 + 4Li3PO4 + 20H3PO4 = 24LiMnPO4 + 30H2O + 9O2↑. (3) Filter the slurry to obtain lithium manganese phosphate (LiMnPO4); (4) Measure the XRD of the lithium manganese phosphate. If there is an impurity phase, continue to use fresh phosphoric acid as the medium and continue to mill and filter the mixture with a sand mill until high-purity lithium manganese phosphate is finally obtained; (5) Mix the high-purity lithium manganese phosphate with waste lithium iron phosphate and glucose to obtain a second mixture; (6) Sinter the second mixture at 800°C to obtain lithium manganese iron phosphate / carbon composite LMFP / C. The reaction equation of lithium manganese phosphate and lithium iron phosphate is: .

[0060] The particle size analysis of the lithium manganese iron phosphate (LFP) material showed a D50 of 1.3 μm. The powder resistivity of the LFP material was 153 Ω·cm. Formation tests were conducted on a coin cell assembled with this LFP material. The initial charge capacity at 0.1C was 154.2 mAh / g, the initial discharge capacity at 0.1C was 143.9 mAh / g, the initial efficiency was 93.3%, the specific capacity at 1C was 122.1 mAh / g, and the ratio of 1C to 0.1C was 84.9%.

[0061] Combining Example 1 and Comparative Example 1, without using a sand mill, even with repeated additions of phosphoric acid, lithium manganese oxide could not be completely converted into lithium manganese phosphate, resulting in impurities and poor performance in the final lithium iron phosphate. Compared to Example 1, the lithium manganese iron phosphate powder generated in Comparative Example 1 had high resistivity, leading to a low 0.1C first discharge capacity and reduced first efficiency in the button cell material test. The 1C capacity was also significantly reduced, and the 1C / 0.1C ratio showed poor rate performance. Combining Example 2 and Comparative Example 2, increasing the solid-state sintering temperature in Comparative Example 2 increased the particle size D50, leading to increased powder resistivity and a decrease in the final 1C / 0.1C rate performance of the material.

[0062] In summary, this invention provides a novel method that solves the recycling problems of waste lithium manganese oxide and waste lithium iron phosphate, while simultaneously generating lithium manganese iron phosphate. The method of this invention is simple, effective, and low-cost, and has broad market prospects.

[0063] Please see Figure 1-7 An apparatus for preparing lithium manganese iron phosphate from waste lithium manganese oxide and waste lithium iron phosphate, the sand milling equipment includes an equipment body 1, a sand milling cylinder 2 is provided on the equipment body 1, a grinding cavity is opened inside the sand milling cylinder 2, a rotor 3 is provided inside the grinding cavity, the inside of the sand milling cylinder 2 is filled with abrasive, a drive source is provided at the input end of the rotor 3, and a sand milling component 4 is provided outside the rotor 3;

[0064] Specifically, the grinding cylinder 2 also includes an abrasive feed cylinder 21 disposed above it, as well as a feed pipe 22 and a liquid outlet pipe disposed on the outside.

[0065] The grinding component 4 includes a grinding disc 41 and a rotating cylinder 42 connected to the rotor 3. The grinding disc 41 is responsible for driving the abrasive to undergo violent collisions and friction in the grinding chamber to grind the first mixture.

[0066] Specifically, the rotating drum 42 has multiple movable holes, and a flexible sealing sleeve is provided between the sand grinding disc 41 and the movable holes to ensure its sealing performance.

[0067] A driving component 5 is provided on the inner side of the sand grinding disc 41. The driving component 5 includes a driving block 51. The sand grinding disc 41 is in contact with the driving block 51. The driving component 5 is responsible for driving the driving block 51 to move when it rotates with the driving source, so that multiple sand grinding discs 41 extend outward intermittently in sequence.

[0068] Abrasive is filled according to actual needs, with an abrasive filling rate of 60-85%. The grinding disc 41 carries the abrasive and moves irregularly in the grinding chamber. During the movement, the abrasive repeatedly collides and rubs against the material, so that the material eventually reaches the specifications of the gaps between the abrasive particles. In order to ensure the rotation speed of the abrasive and the material, the abrasive should not be added too much, because this will lead to too small an internal working space, too much resistance, and reduce its movement speed. However, since the collision and friction force between the abrasive and the material is insufficient when the abrasive is filled too little, a drive block 51 is set up. The drive block 51 intermittently carries the grinding disc 41 outward, thereby carrying the abrasive to further squeeze and rub against the material, which further improves the grinding efficiency of the material.

[0069] In a further embodiment of the present invention, a reciprocating block 52 is provided at the bottom of the grinding disc 41. A first inclined groove 53 and a second inclined groove 54 are respectively provided on the reciprocating block 52, and a pair of driving blocks 51 are respectively provided on the first inclined groove 53 and the second inclined groove 54.

[0070] Each reciprocating block 52 corresponds to a pair of driving blocks 51. The pair of driving blocks 51 are located in the first inclined groove 53 and the second inclined groove 54 respectively. Each time, the pair of driving blocks 51 will only squeeze one of the first inclined groove 53 and the second inclined groove 54, thereby realizing the outward and inward movement of the reciprocating block 52.

[0071] The drive block 51 is made of hard metal material.

[0072] Furthermore, the driving component 5 also includes a first driving bar 55 and a second driving bar 56 slidably connected to the outer wall of the rotor 3. The ends of the first driving bar 55 and the second driving bar 56 are each provided with a first irregular ring 57. The rotor 3 is also movably fitted with a second irregular ring 58. The first irregular ring 57 and the second irregular ring 58 are adapted to each other, and the first irregular ring 57 moves relative to the second irregular ring 58 when working.

[0073] The rotor 3 has a guide groove, and a guide block is slidably disposed in the guide groove. The inner walls of the first drive bar 55 and the second drive bar 56 are fixedly connected to the guide block and slidably connected to the outer wall of the rotor through the guide block.

[0074] In a further embodiment of the present invention, the first irregular ring 57 and the second irregular ring 58 are provided with a crest portion 59 and a trough portion 510. During the rotation of the irregular ring, by abutting against the second irregular ring 58, the first drive bar 55 and the second drive bar 56 reciprocate, and the sand grinding disc 41 is driven to extend outward by the drive block 51.

[0075] Specifically, in this case, there are three first drive bars 55 and three second drive bars 56, which are distributed at intervals. The two ends of the three first drive bars 55 or second drive bars 56 are connected to a first irregular ring 57. Initially, the crest of the first irregular ring 57 corresponds to the trough of the nearby second irregular ring 58. In this way, when the first irregular ring 57 rotates, it will receive resistance and move.

[0076] A sealing disc 23 is provided between the rotating drum 42 and the grinding drum 2. The sealing disc 23 is fixedly connected to the grinding disc 41. A support ring is fixedly connected between the second irregular ring 58 and the sealing disc 23. The second irregular ring 58 is in a stationary state. During the rotation of the first irregular ring 57, it comes into contact with the second irregular ring 58, causing the first irregular ring 57 to reciprocate. During the reciprocating motion of the first irregular ring 57, it will also move the drive block 51 back and forth, pressing the corresponding first inclined groove 53 and second inclined groove 54, thereby realizing the intermittent outward extrusion of the grinding disc 41, which extrudes the surrounding abrasive and changes the original movement trajectory of the surrounding abrasive. This effectively avoids the problem that some materials are subjected to fewer collisions and frictions, and that the grinding force and number of times the materials are not uniform. It solves the problem that some materials are ground but some materials are not, thus prolonging the grinding time.

[0077] The abrasive around the grinding disc 41 rotates periodically, rubbing and slightly squeezing the material. However, when the grinding disc 41 moves outward, it forcibly moves the abrasive around it. The abrasive not only changes its original trajectory and applies squeezing and cutting forces to the material, but also indirectly causes the abrasive around the grinding disc 41 to change its movement by changing its trajectory. This allows the material on the periphery to also experience squeezing forces that were not originally present, making the movement of the abrasive inside the grinding cavity more full and uniform.

[0078] Specifically, a filter screen is also provided on the side of the sealing disc 23. When the material is ground to the smallest size, it can enter the outside of the filter screen and flow out from the pipe, thereby achieving the effect of grinding the material.

[0079] In a further embodiment of the present invention, a telescopic rod is provided between the rotor 3 and the reciprocating block 52. The telescopic rod includes a hollow rod and a piston rod. A strong spring is fixedly connected between the bottom of the piston rod and the inner wall of the hollow rod. A slot is provided on the first drive bar 55, and the telescopic rod is located inside the slot.

[0080] In this invention, by setting a telescopic rod, not only can the grinding disc 41 move freely in telescopic motion, but the power of the rotor 3 can also be transmitted to the rotating drum 42.

[0081] The foregoing has only described certain exemplary embodiments of the present invention by way of illustration. Undoubtedly, those skilled in the art can modify the described embodiments in various ways without departing from the spirit and scope of the present invention. Therefore, the foregoing drawings and descriptions are illustrative in nature and should not be construed as limiting the scope of protection of the claims of the present invention.

Claims

1. A method for preparing lithium manganese iron phosphate from waste lithium manganese oxide and waste lithium iron phosphate, comprising a sand milling device, characterized in that: Includes the following steps: Waste lithium manganese oxide (LiMn2O4) and lithium phosphate (Li3PO4) were mixed in a solid phase to obtain a first mixture; The first mixture was milled using phosphoric acid (H3PO4) as a medium and a sand milling device. The slurry was filtered to obtain lithium manganese phosphate (LiMnPO4). The XRD of the lithium manganese phosphate was determined. If there was an impurity phase, fresh phosphoric acid was used as the medium. The mixture was then further milled and filtered into a slurry using a sand mill until high-purity lithium manganese phosphate was finally obtained. High-purity lithium manganese phosphate is mixed with waste lithium iron phosphate and a carbon source to obtain a second mixture; The second mixture was subjected to solid-state sintering at 650~750℃ to obtain LMFP / C; The sand milling equipment includes a main body, a sand milling cylinder is provided on the main body, a grinding cavity is provided inside the sand milling cylinder, a rotor is provided inside the grinding cavity, abrasive is filled inside the sand milling cylinder, a drive source is provided at the input end of the rotor, and sand milling components are provided outside the rotor. The grinding component includes a grinding disc and a rotating cylinder connected to the rotor. The grinding disc is responsible for driving the abrasive to undergo intense collisions and friction within the grinding chamber to grind the first mixture. A driving component is provided on the inner side of the sand grinding disc. The driving component includes a driving block. The sand grinding disc is in contact with the driving block. The driving component is responsible for driving the driving block to move when it rotates with the driving source, so that multiple sand grinding discs extend outward intermittently in sequence.

2. The method for preparing lithium manganese iron phosphate from waste lithium manganese oxide and waste lithium iron phosphate according to claim 1, characterized in that, The molar ratio of lithium manganese oxide, lithium phosphate, and phosphoric acid is 3:1:

5.

3. The method for preparing lithium manganese iron phosphate from waste lithium manganese oxide and waste lithium iron phosphate according to claim 2, characterized in that, The carbon source is one or more of the following: sucrose, glucose, fructose, citric acid, phenolic resin, polyvinyl alcohol, polyethylene glycol, starch, carbon black, acetylene black, graphite, graphene, and conductive carbon nanotubes.

4. The method for preparing lithium manganese iron phosphate from waste lithium manganese oxide and waste lithium iron phosphate according to claim 1, characterized in that, The bottom of the grinding disc is provided with a reciprocating block, and the reciprocating block is provided with a first inclined groove and a second inclined groove, which correspond to a pair of drive blocks respectively.

5. The method for preparing lithium manganese iron phosphate from waste lithium manganese oxide and waste lithium iron phosphate according to claim 4, characterized in that, The driving component further includes a first driving bar and a second driving bar that are slidably connected to the outer wall of the rotor. The ends of the first driving bar and the second driving bar are each provided with a first irregular ring. The rotor is also movably fitted with a second irregular ring. The first irregular ring and the second irregular ring are adapted to each other, and the first irregular ring moves relative to the second irregular ring when working.

6. The method for preparing lithium manganese iron phosphate from waste lithium manganese oxide and waste lithium iron phosphate according to claim 5, characterized in that, The first and second irregular rings are provided with crests and troughs. During the rotation of the first irregular ring, it abuts against the second irregular ring, causing the first and second drive bars to move back and forth, and driving the grinding disc to extend outward through the drive block.

7. The method for preparing lithium manganese iron phosphate from waste lithium manganese oxide and waste lithium iron phosphate according to claim 6, characterized in that, A telescopic rod is provided between the rotor and the reciprocating block. The telescopic rod includes a hollow rod and a piston rod. A strong spring is fixedly connected between the bottom of the piston rod and the inner wall of the hollow rod. A slot is opened on the first drive bar, and the telescopic rod is located inside the slot.

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