Recycling method of positive electrode material and regenerated positive electrode material

Abstract

The invention provides a recovery method of a positive electrode material and a regenerated positive electrode material, and the method comprises the following steps: mixing a ternary lithium battery positive electrode material with a first acid solution to obtain a first mixed system; performing first acid leaching treatment on the first mixed system to obtain first filtrate and manganese slag; adjusting the pH value of the first filtrate to 8.5-12 to obtain a second filter residue and a second filtrate; according to the recovery method of the positive electrode material, separation of manganese from metals such as lithium, nickel and cobalt is simply and efficiently achieved by adjusting acid leaching reaction parameters, reaction conditions are mild, introduction of new impurities is avoided, and the recovery method has the advantages of being good in element separation effect, mild in condition and low in cost.

Description

Technical Field

[0001] The invention relates to the field of lithium ion battery positive electrode material recovery, and in particular to a positive electrode material recovery method and a regenerated positive electrode material. Background Art

[0002] Lithium-ion battery positive electrode materials contain metal elements with high economic value. Recycling waste lithium-ion battery positive electrode materials can reduce the cost of remanufacturing positive electrode materials. At present, this field mainly recycles lithium, nickel, and cobalt elements. However, most existing recycling methods leach all valuable metals (usually including manganese, lithium, nickel, and cobalt elements). Since the value of manganese is relatively low and there is an overlap with the precipitation pH of nickel and cobalt, manganese needs to be separated from the nickel and cobalt to be recovered by extraction. The extraction process is complicated and costly, and the extractant will pollute the environment, which makes the recovery method have the defects of complex process, high cost, and pollution.

[0003] In order to solve the above defects, some processes consider suppressing the leaching of manganese in the early stage, while increasing the leaching rate of lithium, nickel and cobalt, so as to complete the separation of manganese elements. For example, Chinese patent CN117477084A discloses a method for recovering manganese dioxide and regenerating positive electrode materials from retired lithium-ion batteries. The method mixes waste positive electrode materials with inorganic acid aqueous solution, and performs hydrothermal reaction under closed conditions to obtain a leachate containing valuable metal ions and a leaching residue rich in manganese dioxide; add appropriate amounts of nickel salts, cobalt salts and manganese salts, and obtain positive electrode material precursors and lithium carbonate by carbonate coprecipitation; mix the precursors and lithium carbonate in the required proportions and roast them to obtain regenerated positive electrode materials. Although this method solves the defects of complex process and pollution, it places high demands on equipment due to the harsh reaction conditions. In addition, this method requires the addition of nickel, cobalt and manganese salts and carbonates when preparing regenerated positive electrode materials, so there is still a defect of high cost.

[0004] Therefore, developing a positive electrode material recovery method with good manganese separation effect, mild conditions and low cost has become a research direction in this field. Summary of the invention

[0005] The invention provides a method for recovering positive electrode materials, which has the characteristics of good element separation effect, mild conditions and low cost.

[0006] The present invention also provides a lithium manganese iron phosphate positive electrode material, which has the characteristics of high purity and low preparation cost.

[0007] The present invention also provides a method for preparing a lithium iron manganese phosphate positive electrode material, which has the characteristics of low cost and capable of preparing a high-purity lithium iron manganese phosphate positive electrode material.

[0008] The present invention provides a method for recovering positive electrode materials, which comprises the following steps:

[0009] Mixing the positive electrode material of the ternary lithium battery with the first acid solution to obtain a first mixed system;

[0010] performing a first acid leaching treatment on the first mixed system to obtain a first filtrate and manganese slag;

[0011] Adjusting the pH value of the first filtrate to 8.5-12 to obtain a second filter residue and a second filtrate;

[0012] In the ternary positive electrode material, the molar ratio of lithium element, nickel element, cobalt element and manganese element is a:x:y:(1-xy);

[0013] The first acid solution includes sulfuric acid, and the ratio M of the amount of sulfuric acid in the first acid solution to the ternary positive electrode material satisfies the following relationship:

[0014] 0.65×(a+2x+2y)≤M≤0.8×(a+2x+2y);

[0015] The solid-liquid ratio of the first mixed system is 120-220 g / L;

[0016] The treatment temperature of the first acid leaching treatment is 75-100°C;

[0017] The treatment time of the first acid leaching treatment is greater than or equal to 180 minutes.

[0018] In the above-mentioned method for recovering positive electrode materials, the ratio M of the amount of substance of the ternary positive electrode material to the sulfuric acid in the first acid solution satisfies the following relationship:

[0019] 0.7×(a+2x+2y)≤M≤0.75×(a+2x+2y).

[0020] In the above-mentioned method for recovering positive electrode materials, the solid-liquid ratio of the first mixed system is 150-200 g / L.

[0021] In the above-mentioned method for recovering positive electrode materials, the treatment temperature of the first acid leaching treatment is 80-95°C.

[0022] The present invention also provides a method for preparing a lithium manganese iron phosphate positive electrode material, which comprises the following steps:

[0023] Using any of the above-mentioned positive electrode material recovery methods to prepare manganese slag and a second filtrate;

[0024] Mixing the lithium iron phosphate positive electrode material with the second acid solution and the oxidant to obtain a second mixed system;

[0025] performing a second acid leaching treatment on the second mixed system to obtain a third filtrate and iron phosphate slag;

[0026] mixing the second filtrate, the third filtrate and phosphoric acid to obtain a third mixed system;

[0027] Adjusting the pH of the third mixed system to 10-11 to obtain lithium phosphate;

[0028] Mixing the manganese slag, the iron phosphate slag and the lithium phosphate to obtain a fourth mixed system;

[0029] The fourth mixed system is calcined to obtain the lithium manganese iron phosphate positive electrode material.

[0030] The method for preparing the lithium iron manganese phosphate positive electrode material as described above, wherein the second acid solution comprises sulfuric acid, and the ratio of the amount of sulfuric acid in the second acid solution to the amount of the lithium iron manganese phosphate positive electrode material is 0.5-1.5; and / or,

[0031] The oxidant includes hydrogen peroxide, and the ratio of the amount of the hydrogen peroxide to the amount of the lithium manganese iron phosphate positive electrode material is 1-3.

[0032] In the method for preparing the lithium manganese iron phosphate positive electrode material as described above, the treatment temperature of the second acid leaching treatment is 25-90°C.

[0033] In the method for preparing the lithium manganese iron phosphate positive electrode material as described above, in the third mixed system, the molar ratio of lithium element, manganese element, iron element and phosphorus element is (0.9-1.1): (0.3-0.5): (0.5-0.7): (0.9-1.1).

[0034] In the method for preparing the lithium manganese iron phosphate positive electrode material as described above, the treatment temperature of the calcination treatment is 600-800° C. and the treatment time is 10-14 hours.

[0035] The present invention also provides a lithium iron manganese phosphate positive electrode material, wherein the material is prepared using any of the above-mentioned methods for preparing the lithium iron manganese phosphate positive electrode material.

[0036] The positive electrode material recovery method provided by the present invention can simply and efficiently separate manganese from metals such as lithium, nickel and cobalt by adjusting the acid leaching reaction parameters. The reaction conditions are mild and the introduction of new impurities is avoided. It has the characteristics of good element separation effect, mild conditions and low cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application.

[0038] Figure 1 A schematic diagram of a method for preparing the lithium iron manganese phosphate positive electrode material provided by the present invention.

[0039] The above drawings have shown clear embodiments of the present application, which will be described in more detail later. These drawings and text descriptions are not intended to limit the scope of the present application in any way, but to illustrate the concept of the present application to those skilled in the art by referring to specific embodiments. DETAILED DESCRIPTION

[0040] Exemplary embodiments will be described in detail herein, examples of which are shown in the accompanying drawings. When the following description refers to the drawings, the same numbers in different drawings represent the same or similar elements unless otherwise indicated. The implementations described in the following exemplary embodiments do not represent all implementations consistent with the present application. Instead, they are merely examples of devices and methods consistent with some aspects of the present application as detailed in the appended claims.

[0041] The prior art can separate manganese from other metal elements by mixing waste positive electrode materials with inorganic acid aqueous solution and then conducting hydrothermal reaction. However, this method has harsh reaction conditions. The inventor speculates that the above defects are due to the fact that the conditions for the reaction between waste positive electrode materials and inorganic acid aqueous solution are not suitable, resulting in the need for a more harsh treatment method to separate manganese from other metal elements. Therefore, if the conditions for the reaction between waste positive electrode materials and inorganic acid aqueous solution can be changed, the above problems can be solved.

[0042] Based on this, the first aspect of the present invention provides a method for recovering a positive electrode material, which includes the following process:

[0043] Mixing the ternary positive electrode material with the first acid solution to obtain a first mixed system;

[0044] performing a first acid leaching treatment on the first mixed system to obtain a first filtrate and manganese slag;

[0045] Adjusting the pH value of the first filtrate to 8.5-12 to obtain a second filter residue and a second filtrate;

[0046] In the ternary cathode material, the molar ratio of lithium, nickel, cobalt and manganese is a:x:y:(1-xy);

[0047] The first acid solution includes sulfuric acid, and the ratio M of the amount of sulfuric acid in the first acid solution to the ternary positive electrode material satisfies the following relationship:

[0048] 0.65×(a+2x+2y)≤M≤0.8×(a+2x+2y);

[0049] The solid-liquid ratio of the first mixed system is 120-220 g / L;

[0050] The treatment temperature of the first acid leaching treatment is 75-100°C;

[0051] The treatment time of the first acid leaching treatment is greater than or equal to 180 minutes.

[0052] Among them, the ternary positive electrode material refers to the nickel cobalt manganese oxide material used in the ternary lithium battery, and the molar ratio of lithium element, nickel element, cobalt element and manganese element is a:x:y:(1-xy).

[0053] Due to the large variety of ternary cathode materials in the art, the present invention does not specifically limit the molecular formula of the ternary cathode material. In one embodiment, the molecular formula of the ternary cathode material is Li a Ni x Co y Mn (1-x-y) M b O 2 , wherein the M element is a modifying element. The present invention does not limit the specific selection of the M element, and commonly used modifying elements in the art, such as silver, copper, etc., can be used. In addition, the present invention does not limit the source of the M element, and the M element can come from a doping process or a coating process.

[0054] The present invention does not limit the source of the ternary positive electrode material. In one embodiment, the material can come from retired ternary lithium batteries. Specifically, the retired ternary lithium batteries can be soaked in salt water and fully discharged and then disassembled. After removing other components such as the current collector, the positive electrode material is obtained. After grinding, washing, and drying, the ternary positive electrode material can be obtained. The content of other elements (i.e., M element) in the ternary positive electrode material obtained by the above process is relatively low, so it is generally believed that the above positive electrode material is a pure product.

[0055] Specifically, first, the ternary positive electrode material can be mixed with the first acid solution to obtain a first mixed system. The first acid solution includes sulfuric acid. In one embodiment, the first acid solution can be prepared by diluting concentrated sulfuric acid with water. The amount M of sulfuric acid in the first acid solution satisfies the following relationship:

[0056] 0.65×(a+2x+2y)≤M≤0.8×(a+2x+2y), for the following reasons:

[0057] The reaction between the ternary cathode material and hydrogen ions follows the following reaction formula:

[0058]

[0059] Therefore, 0.5×(a+2x+2y)mol of sulfuric acid is required to react with 1mol of the ternary cathode material to completely decompose it. That is, according to the theoretical dosage, the molar ratio of the ternary cathode material to sulfuric acid is 0.5×(a+2x+2y).

[0060] In the positive electrode material recovery method provided by the present invention, the molar ratio of the ternary positive electrode material to sulfuric acid needs to be controlled to be 130% to 160% of the theoretical amount. Therefore, the molar amount M of sulfuric acid in the first acid solution satisfies the following relationship: 0.65×(a+2x+2y)≤M≤0.8×(a+2x+2y).

[0061] In addition, the solid-liquid ratio of the first mixed system is 120-220 g / L. Specifically, the first mixed system includes a ternary cathode material and a first acid solution, wherein the ternary cathode material is solid and the first acid solution is liquid, and the solid-liquid ratio of the first mixed system is the ratio of the mass of the ternary cathode material to the volume of the first acid solution.

[0062] Specifically, in the actual production process, the ICP method can be used to determine the a, x, and y values ​​in the molecular formula of the ternary positive electrode material, and then determine the molecular weight of the ternary positive electrode material. The molecular weight is combined with the mass of the material to obtain the amount of substance of the material, and then the range of values ​​of the amount of sulfuric acid in the first acid solution can be determined based on the a, x, and y values. Subsequently, the volume of water used to dilute the sulfuric acid can be obtained in combination with the solid-liquid ratio range of the first mixed system.

[0063] The first mixed system is subjected to a first acid leaching treatment, wherein the treatment temperature of the first acid leaching treatment is 75-100° C., the treatment time of the first acid leaching treatment is greater than or equal to 180 minutes, and after the treatment is completed, the treatment system is subjected to solid-liquid separation to obtain a first filtrate and manganese slag. The manganese slag contains manganese dioxide, and the first filtrate contains lithium ions, divalent nickel ions, and divalent cobalt ions.

[0064] Further, the pH value of the first filtrate can be adjusted to 8.5-12 to obtain a second filter residue and a second filtrate. In this pH range, the divalent nickel ions and divalent cobalt ions in the first filtrate form hydroxide precipitation to obtain the second filter residue, and the remaining second filtrate includes lithium ions.

[0065] The inventors found that when the positive electrode material recovery method provided by the present invention is used to recover the positive electrode material, the manganese content in the first filtrate obtained is relatively low. The inventors believe that the reason may be that the nickel, cobalt, and manganese in the ternary positive electrode material are mostly in a high-valent state, and lithium is more easily leached. When sufficient sulfuric acid is added to the ternary positive electrode material, its layered structure is destroyed, and Li + and a small amount of nickel and cobalt ions are released into the leaching solution. When the acid leaching temperature is higher than 75°C, due to the 3+ The stability is very poor, and it is very easy to undergo disproportionation reaction to generate Mn under acidic conditions. 2+ and Mn 4+ , Mn 2+It can be dissolved in the liquid phase. Therefore, the leaching rate of manganese is high at the beginning of the reaction, and it cannot be separated from nickel. When the reaction time exceeds 180min, the produced Mn 2+ The amount is sufficient and shows reducing properties, and Ni 3+ 、Co 3+ The reaction generates Ni 2+ 、Co 2+ and Mn 3+ , which further increases the leaching rate of nickel and cobalt. As the reaction time continues to increase, the Mn generated by the redox reaction 3+ Continue the disproportionation reaction to generate Mn again 2+ and Mn 4+ . Mn 2+ Redox reactions and Mn 3+ The continuous occurrence of disproportionation reaction makes Mn 4+ The content of manganese dioxide gradually increases and exists in the solid phase in the form of manganese dioxide. Because manganese dioxide has a stable structure, it does not react with concentrated sulfuric acid even at a temperature of 57-100°C and can be further used for high value. The ion reactions involved in the above process are as follows.

[0066]

[0067] Furthermore, if more manganese is leached while lithium, nickel and cobalt are fully leached, the elemental composition in the leached residue will be complex, making it difficult to consider recycling and reuse. At the same time, the presence of nickel, cobalt and manganese in the leaching solution still requires subsequent element separation, resulting in a complex process flow and increased costs. Therefore, the conversion of this reaction requires strict control of reaction parameters. Specifically, if the temperature is too low, the acid leaching reaction and Mn 2+ The driving force of the redox reaction is reduced, which reduces the leaching rate of lithium nickel cobalt. 2+ The degree of conversion to manganese dioxide decreases, and the leaching rate of manganese will increase. If the reaction time is too short, the disproportionation reaction and redox reaction have not been completed, which will cause the lithium nickel cobalt leaching rate to decrease and the manganese leaching rate to increase. If the amount of sulfuric acid added is too low, the degree of manganese disproportionation reaction is low at the beginning, and the generated Mn 2+ The decrease in the redox reaction of nickel and cobalt ions reduces the degree of redox reaction, which makes it impossible to effectively improve the leaching rate of nickel and cobalt. At the same time, it is difficult to maintain the alternation of manganese disproportionation reaction and redox reaction, making it difficult for all manganese ions entering the leaching solution to be converted back to the solid phase, resulting in a decrease in the leaching rate of lithium, nickel and cobalt, while an increase in the leaching rate of manganese. If the solid-liquid ratio is too low, and the amount of sulfuric acid added remains unchanged, H + The concentration of is reduced, which reduces the leaching rate of lithium, nickel and cobalt, and slightly increases the leaching rate of manganese.

[0068] The positive electrode material recovery method provided by the present invention does not require the addition of a reducing agent, and achieves zero or low leaching of manganese elements by strictly controlling the reaction parameters of simple acid leaching. The reaction conditions are mild, the separation effect is good, and there is no need to separate manganese from nickel and cobalt subsequently, thereby reducing the difficulty and cost of subsequent processing; in addition, manganese is converted from solid phase to liquid phase to solid phase, so that it exists in the form of manganese dioxide in the leached residue, and the manganese residue can be reused subsequently, thereby improving the economic benefit.

[0069] In one embodiment, in order to further reduce the leaching rate of manganese, the ratio M of the amount of the ternary positive electrode material to the amount of sulfuric acid in the first acid solution can be controlled to satisfy the following relationship: 0.7×(a+2x+2y)≤M≤0.75×(a+2x+2y), more preferably 0.75×(a+2x+2y). The appropriate amount of sulfuric acid added can increase the degree of manganese disproportionation reaction and generate more Mn. 2+ At the same time, the degree of redox reaction of nickel and cobalt ions is increased synchronously, which effectively improves the leaching rate of nickel and cobalt while maintaining the alternation of manganese disproportionation reaction and redox reaction, so that more manganese ions entering the leaching solution are converted back to the solid phase.

[0070] Furthermore, the solid-liquid ratio of the first mixed system can be controlled to be 150-200 g / L, preferably 200 g / L. The appropriate solid-liquid ratio can maintain the hydrogen ion concentration in the first mixed system within an appropriate range when the amount of sulfuric acid remains unchanged, thereby increasing the leaching rate of lithium, nickel and cobalt while reducing the leaching rate of manganese.

[0071] In addition, the treatment temperature of the first acid leaching treatment can be controlled to be 80-95°C, preferably 95°C, and / or the treatment time of the first acid leaching treatment can be controlled to be 960 minutes. The treatment temperature of the appropriate acid leaching treatment can be increased, and the Mn 2+ The driving force of the redox reaction increases the leaching rate of lithium nickel and cobalt while increasing the Mn 2+ The degree of conversion to manganese dioxide; the appropriate treatment time for the first acid leaching treatment can allow the disproportionation reaction and the redox reaction to be completed, further improving the lithium nickel cobalt leaching rate while reducing the manganese leaching rate.

[0072] A second aspect of the present invention provides a lithium manganese iron phosphate positive electrode material, which is prepared by a method comprising the following process:

[0073] Using the positive electrode material recovery method provided by the first aspect of the present invention to prepare manganese slag and a second filtrate;

[0074] Mixing the lithium iron phosphate positive electrode material with the second acid solution and the oxidant to obtain a second mixed system;

[0075] performing a second acid leaching treatment on the second mixed system to obtain a third filtrate and iron phosphate slag;

[0076] mixing the second filtrate, the third filtrate and phosphoric acid to obtain a third mixed system;

[0077] adjusting the pH of the third mixed system to 10-11 to obtain lithium phosphate;

[0078] mixing manganese slag, iron phosphate slag and lithium phosphate to obtain a fourth mixed system;

[0079] The fourth mixed system is calcined to obtain lithium manganese iron phosphate positive electrode material.

[0080] Lithium iron phosphate positive electrode material refers to a positive electrode material used for lithium iron phosphate batteries. The present invention does not limit the source of the lithium iron phosphate positive electrode material. In one embodiment, the material can come from retired lithium iron phosphate batteries. Specifically, retired lithium iron phosphate batteries can be soaked in salt water and fully discharged and then disassembled. After removing other components such as current collectors, the positive electrode material is obtained. After grinding, washing, and drying, the lithium iron phosphate positive electrode material can be obtained.

[0081] Specifically, first, the lithium iron phosphate positive electrode material is mixed with a second acid solution and an oxidant to obtain a second mixed system, wherein the second acid solution may include an inorganic acid commonly used in the art, such as sulfuric acid; and the oxidant may include an oxidant commonly used in the art, such as hydrogen peroxide. During the second acid leaching treatment of the second mixed system, 1 mol of the lithium iron phosphate positive electrode material reacts with 1 mol of hydrogen ions and 1 mol of hydrogen peroxide to generate iron phosphate, water, lithium ions and oxygen. The present invention does not limit the specific composition of the lithium iron phosphate positive electrode material, and lithium iron phosphate positive electrode materials commonly used in the art that include or do not include modifying elements can be used.

[0082] The second mixed system is subjected to a second acid leaching treatment to obtain a third filtrate and iron phosphate slag, wherein the third filtrate includes lithium ions and the iron phosphate slag includes iron phosphate.

[0083] The present invention does not limit the dosage of the second acid solution and the oxidant, and the dosage commonly used in the art can be used to meet the requirement of decomposing the lithium iron phosphate positive electrode material into iron phosphate and lithium ions. The present invention also does not limit the specific treatment conditions of the second acid leaching treatment, and the commonly used conditions in the art can be used.

[0084] Next, the second filtrate, the third filtrate and phosphoric acid are mixed to obtain a third mixed system; the pH of the third mixed system is adjusted to 10-11 to obtain lithium phosphate.

[0085] Since both the second filtrate and the third filtrate contain lithium ions, the second filtrate, the third filtrate and phosphoric acid are mixed to obtain a third mixed system, the pH of the third mixed system is adjusted to 10-11, phosphate radicals combine with lithium ions to form lithium phosphate, and lithium phosphate can be obtained after solid-liquid separation of the third mixed system.

[0086] The present invention does not limit the specific method for adjusting the pH of the third mixed system to 10-11. In one embodiment, sodium hydroxide can be used to achieve the above process.

[0087] Subsequently, manganese slag, iron phosphate slag and lithium phosphate are mixed to obtain a fourth mixed system; the fourth mixed system is calcined to obtain a manganese iron phosphate lithium positive electrode material. Among them, the component of manganese slag is manganese dioxide, and the component of iron phosphate slag is iron phosphate. The mixed system including manganese dioxide, iron phosphate and lithium phosphate is calcined, and the above raw materials can undergo a chemical reaction to generate a manganese iron phosphate lithium positive electrode material.

[0088] The present invention does not limit the mixing ratio of manganese slag, iron phosphate slag and lithium phosphate in the above process, and the specific treatment conditions of calcination treatment, and the common mixing ratio and treatment conditions in the art can be used.

[0089] The lithium iron manganese phosphate positive electrode material provided in the second aspect of the present invention is prepared using a ternary positive electrode material and a lithium iron manganese phosphate positive electrode material as raw materials. The metal salts required in the preparation process are all recycled, and no other metal salts need to be added, which has the characteristic of low preparation cost.

[0090] The third aspect of the present invention provides a method for preparing a lithium manganese iron phosphate positive electrode material. Figure 1 As shown, the method includes the following process:

[0091] Using the positive electrode material recovery method provided by the first aspect of the present invention to prepare manganese slag and a second filtrate;

[0092] Mixing the lithium iron phosphate positive electrode material with the second acid solution and the oxidant to obtain a second mixed system;

[0093] performing a second acid leaching treatment on the second mixed system to obtain a third filtrate and iron phosphate slag;

[0094] mixing the second filtrate, the third filtrate and phosphoric acid to obtain a third mixed system;

[0095] adjusting the pH of the third mixed system to 10-11 to obtain lithium phosphate;

[0096] mixing manganese slag, iron phosphate slag and lithium phosphate to obtain a fourth mixed system;

[0097] The fourth mixed system is calcined to obtain lithium manganese iron phosphate positive electrode material.

[0098] Among them, the meanings of terms such as lithium iron phosphate positive electrode material, second acid solution, oxidant, second acid leaching treatment, third filtrate, and iron phosphate slag are the same as above and will not be repeated here.

[0099] The preparation method of the lithium iron manganese phosphate positive electrode material provided by the present invention proposes a new direction for the coordinated recovery of retired lithium iron phosphate batteries and ternary lithium batteries to prepare lithium iron manganese phosphate. The metal salts required in the preparation process are all recycled, and there is no need to add other metal salts. It has the advantages of simple process flow and low preparation cost.

[0100] Further, in one embodiment, the second acid solution includes sulfuric acid, and the ratio of the amount of sulfuric acid in the second acid solution to the amount of manganese iron phosphate lithium positive electrode material is 0.5-1.5. Furthermore, the ratio of the amount of hydrogen peroxide to the amount of manganese iron phosphate lithium positive electrode material can also be controlled to be 1-3. Appropriate amounts of sulfuric acid and hydrogen peroxide can react with the lithium iron phosphate positive electrode material more efficiently, thereby improving the efficiency of the preparation method of the manganese iron phosphate lithium positive electrode material provided by the present invention.

[0101] In another specific embodiment, the treatment temperature of the second acid leaching treatment can be controlled to be 25-90° C. Furthermore, the treatment time of the second acid leaching treatment can be controlled to be 0-180 min. The appropriate treatment temperature and treatment time can inhibit the leaching of phosphorus and iron while ensuring the full leaching of lithium.

[0102] In one embodiment, the molar ratio of lithium, manganese, iron and phosphorus in the third mixed system can be controlled to be (0.9-1.1): (0.3-0.5): (0.5-0.7): (0.9-1.1), preferably 1: 0.4: 0.6: 1. The appropriate element ratio can make the prepared lithium manganese iron phosphate positive electrode material have higher purity; in addition, the treatment temperature of the calcination treatment can be controlled to be 600-800°C and the treatment time to be 10-14h, preferably the treatment temperature is 700°C and the treatment time is 12h. The appropriate treatment time and treatment temperature can make the raw materials fully react, and improve the crystallinity and particle size uniformity of the product, thereby improving its electrochemical performance.

[0103] The following is a further description of the method for recycling waste positive electrode materials provided by the present invention through specific implementation methods.

[0104] Embodiment 1:

[0105] 1) The retired ternary lithium battery is immersed in a salt solution for discharge. After full discharge, it is disassembled, ground, cleaned and dried to obtain a ternary positive electrode material. The molecular formula of the ternary positive electrode material is LiNi measured by ICP-OES. 0.6 Co 0.1 Mn 0.3 O 2 , then the molecular weight of the positive electrode material is 96.53, that is, a=1, x=0.6, y=0.1;

[0106] 2) Mix 96.53g (1 mol) of the above-mentioned ternary positive electrode material with 0.48L of the first acid solution to obtain a first mixed system with a solid-liquid ratio of 200g / L. According to the molecular formula of the ternary positive electrode material, the theoretical amount of sulfuric acid required for 1 mol of the ternary positive electrode material is 0.5×(1+2×0.6+2×0.1)=1.2 mol. The first acid solution is an aqueous sulfuric acid solution, and the amount of sulfuric acid contained is 1.8 mol, which is 150% of the theoretical amount. Set the temperature of the water bath to 95°C, and perform a first acid leaching treatment at a temperature of 95°C and a time of 960 min on the first mixed system. After the treatment, perform solid-liquid separation on the treated system to obtain a first filtrate and a manganese slag with the component of manganese dioxide;

[0107] 3) adjusting the pH of the first filtrate to 12 using a sodium hydroxide solution to precipitate nickel and cobalt, and obtaining a second filter residue and a second filtrate through solid-liquid separation;

[0108] 4) Soak the retired lithium iron phosphate battery in a salt solution for discharge, disassemble and grind it after full discharge to obtain lithium iron phosphate positive electrode material;

[0109] Mix 158g (1mol) of lithium iron phosphate battery positive electrode material, hydrogen peroxide, and the second acid solution to obtain a second mixed system with a solid-liquid ratio of 1000g / L. Among them, the amount of hydrogen peroxide in hydrogen peroxide is 2mol, which is 200% of the theoretical amount; the second acid solution is an aqueous sulfuric acid solution, and the amount of sulfuric acid contained is 0.5mol, which is 100% of the theoretical amount. Set the temperature of the water bath to 25°C, and perform a second acid leaching treatment on the second mixed system at a temperature of 25°C and a liquid phase time of 60min. After the treatment, perform solid-liquid separation on the treated system to obtain a third filtrate and iron phosphate slag with the component of iron phosphate;

[0110] 5) After the second filtrate and the third filtrate are mixed, 500 mL of the mixed solution is taken, and 20 g of a phosphoric acid solution with a concentration of 85% is added thereto to obtain a third mixed system, and the third mixed system is reacted at 80° C. for 1 hour to perform preliminary lithium precipitation;

[0111] 6) adjusting the pH of the third mixed system to 11 using a sodium hydroxide solution, reacting at 80° C. for 2 hours to perform deep lithium precipitation to obtain lithium phosphate solid;

[0112] 7) The lithium phosphate solid, iron phosphate slag and manganese slag prepared in the above steps are used as raw materials, mixed in a molar ratio of lithium: manganese: iron: phosphorus of 1:0.4:0.6:1, and calcined at 700°C for 12 hours to prepare a lithium iron manganese phosphate positive electrode material.

[0113] Example 2

[0114] This embodiment is substantially the same as embodiment 1, except that in step 2), the first acid solution comprises 140% of the theoretical amount of sulfuric acid solution.

[0115] Example 3

[0116] This embodiment is basically the same as embodiment 1, except that in step 2), the treatment temperature of the first acid leaching treatment is 80°C.

[0117] Example 4

[0118] This embodiment is basically the same as embodiment 1, except that in step 2), the treatment time of the first acid leaching treatment is 360 minutes.

[0119] Example 5

[0120] This embodiment is basically the same as embodiment 1, except that in step 3), a sodium hydroxide solution is used to adjust the pH of the first filtrate to 8.5.

[0121] Example 6

[0122] This embodiment is basically the same as embodiment 1, except that in step 4), the amount of sulfuric acid used is 200% of the theoretical amount.

[0123] Example 7

[0124] This embodiment is basically the same as embodiment 1, except that in step 4), the amount of hydrogen peroxide used is 100% of the theoretical amount.

[0125] Example 8

[0126] This embodiment is basically the same as embodiment 1, except that in step 4), the amount of hydrogen peroxide used is 300% of the theoretical amount.

[0127] Example 9

[0128] This embodiment is basically the same as embodiment 1, except that in step 4), the treatment temperature of the second acid leaching treatment is 90°C.

[0129] Example 10

[0130] This embodiment is basically the same as embodiment 1, except that in step 4), the treatment time of the second acid leaching treatment is 180 minutes.

[0131] Embodiment 11

[0132] This embodiment is basically the same as Embodiment 1, except that in step 6), the pH of the third mixed system is adjusted to 10 using sodium hydroxide solution.

[0133] Example 12

[0134] This embodiment is basically the same as Embodiment 1, except that in step 4), the second mixed system does not include hydrogen peroxide, but oxygen is introduced into the second mixed system during the second acid leaching process.

[0135] Example 13

[0136] This embodiment is basically the same as embodiment 1, except that in step 2), the amount of sulfuric acid used is 130% of the theoretical amount.

[0137] Embodiment 14

[0138] This embodiment is basically the same as embodiment 1, except that in step 2), the amount of sulfuric acid used is 160% of the theoretical amount.

[0139] Embodiment 15

[0140] This embodiment is basically the same as embodiment 1, except that in step 2), the amount of sulfuric acid in the first acid solution is kept unchanged, and the solid-liquid ratio of the first mixed system is set to 120 g / L by changing the volume of water in the aqueous sulfuric acid solution.

[0141] Example 16

[0142] This embodiment is basically the same as embodiment 1, except that in step 2), the amount of sulfuric acid in the first acid solution is kept unchanged, and the solid-liquid ratio of the first mixed system is set to 220 g / L by changing the volume of water in the aqueous sulfuric acid solution.

[0143] Comparative Example 1

[0144] This comparative example is substantially the same as Example 1, except that in step 2), the first acid solution comprises 120% of the theoretical amount of sulfuric acid solution.

[0145] Comparative Example 2

[0146] This comparative example is basically the same as Example 1, except that in step 2), the treatment temperature of the first acid leaching treatment is 70°C.

[0147] Comparative Example 3

[0148] This comparative example is basically the same as Example 1, except that in step 2), the treatment time of the first acid leaching treatment is 120 minutes.

[0149] Comparative Example 4

[0150] This comparative example is basically the same as Example 1, except that in step 2), the solid-liquid ratio of the first mixed system is 100 g / L.

[0151] Comparative Example 5

[0152] This comparative example is basically the same as Example 1, except that in step 2), the sulfuric acid solution is replaced with a solution having the same molar amount of H + of hydrochloric acid solution.

[0153] Test example

[0154] The leaching rates of lithium, nickel, cobalt and manganese elements in the ternary positive electrode materials in each embodiment and comparative example, the leaching rates of lithium, iron and phosphorus elements in the lithium iron phosphate positive electrode materials, and the recovery rates of nickel, cobalt and lithium elements in lithium iron manganese phosphate were statistically analyzed, and the results are shown in Table 1.

[0155] Among them, the calculation method of the leaching rate of each element in the ternary positive electrode material and the lithium iron phosphate positive electrode material is as follows:

[0156]

[0157] Where η represents the leaching rate (%), ρ and V are the concentration of a certain element in the leachate (ppm) and the volume of the leachate (mL), respectively, and w and m are the initial content of the corresponding element in the positive electrode material (%) and the mass of the positive electrode material (g), respectively.

[0158] The statistical method of recovery rate of each element is as follows:

[0159]

[0160] Among them, a, V 1 are the concentration (ppm) and volume (mL) of an element in the filtrate after precipitation, b, V 2 are the concentration of the corresponding element in the solution before precipitation (ppm) and the volume of the solution (mL), respectively.

[0161] Table 1

[0162]

[0163] From Table 1, we can see that:

[0164] For Example 2 and Example 13, when the amount of sulfuric acid is reduced, Mn 3+ Mn generated by disproportionation reaction 2+ Reduced, Mn entering the solid phase 4+ The corresponding reduction reduces the leaching rate of lithium, nickel and cobalt, while the leaching rate of manganese increases.

[0165] For Example 3, when the acid leaching reaction temperature is lowered, the acid leaching reaction and Mn 2+ The driving force of the redox reaction is reduced, which reduces the leaching rate of lithium, nickel and cobalt, while the leaching rate of manganese increases.

[0166] For Example 4, when the reaction time is shortened, the disproportionation reaction and the redox reaction have not been completed, resulting in a decrease in the nickel and cobalt leaching rate and an increase in the manganese leaching rate.

[0167] For Example 5, the pH of the first filtrate is reduced, and the OH provided by the system - The reduction is not enough to completely precipitate nickel and cobalt, resulting in a lower recovery rate of nickel and cobalt.

[0168] For Example 6, the amount of sulfuric acid used for liquid phase oxidation leaching was increased, H + The increase in concentration promotes the positive leaching reaction and increases the leaching rates of lithium, phosphorus and iron.

[0169] For Example 7, the amount of hydrogen peroxide used in liquid phase oxidation was reduced, Fe 2+ The degree of conversion to iron phosphate precipitation decreases, which reduces the leaching rate of lithium, while the leaching rate of iron phosphate increases to a certain extent.

[0170] For Example 8, increasing the amount of hydrogen peroxide used in liquid phase oxidation promotes Fe 2+ The conversion to iron phosphate precipitation helps to increase the leaching rate of lithium, while the leaching rate of iron phosphate is reduced due to the production of iron phosphate precipitation.

[0171] For Example 9, by increasing the reaction temperature of the liquid phase oxidation, the hydrogen peroxide will undergo a self-decomposition side reaction, and the amount participating in the liquid phase oxidation reaction will decrease, thereby reducing the lithium leaching rate.

[0172] For Example 10, the reaction time of liquid phase oxidation is prolonged. Since the lithium element has been almost completely leached out, further prolonging the time will increase the lithium leaching rate, but the degree of influence is small.

[0173] For Example 11, the pH was lowered during the precipitation of lithium phosphate, and the reaction was not complete, resulting in a lower lithium recovery rate.

[0174] For Example 12, oxygen has a certain oxidizing ability, but since oxygen is more stable and less likely to acquire electrons than hydrogen peroxide, its oxidizing ability is weaker, which reduces the precipitation of iron phosphate, and thus the leaching rate of iron phosphate increases.

[0175] For Example 14, the amount of sulfuric acid in the first acid solution was increased. However, since lithium, nickel and cobalt were almost completely leached out, increasing the amount of sulfuric acid had little effect.

[0176] For Example 15, the solid-liquid ratio of the first mixed system is reduced. When the amount of sulfuric acid used is constant, the concentration of H+ decreases with the decrease of the solid-liquid ratio, so that the leaching reaction cannot be fully carried out, and the leaching rates of lithium, nickel and cobalt are reduced; the Mn2+ used for the redox reaction is reduced, so that the leaching rate of manganese is increased.

[0177] For Example 16, the solid-liquid ratio of the first mixed system is increased, the viscosity of the system is increased, resulting in an increase in mass transfer resistance, which is not conducive to the contact of the solid-liquid interface of the leaching system, and reduces the leaching rates of lithium, nickel and cobalt; the Mn2+ used for redox reaction is reduced, and the leaching rate of manganese is increased.

[0178] It can be seen from Comparative Example 1 that when the amount of sulfuric acid is too low, H + The concentration is low, the initial disproportionation reaction of manganese is low, and the generated Mn 2+ The reduction reduces the degree of redox reaction of nickel and cobalt ions, making it impossible to effectively increase the leaching rate of nickel and cobalt. At the same time, the leaching rate of manganese increases due to the limited degree of conversion to the solid phase.

[0179] It can be seen from Comparative Example 2 that when the leaching temperature of acid leaching is too low, the acid leaching and Mn 2+ The driving force of the reduction reaction is insufficient, which reduces the leaching rate of lithium nickel cobalt. 2+ The degree of conversion to manganese dioxide decreases and the leaching rate of manganese increases.

[0180] It can be seen from Comparative Example 3 that when the reaction time of acid leaching is too short, most of the Mn 2+ The conversion has not yet begun, which reduces the leaching rate of lithium, nickel and cobalt, while increasing the leaching rate of manganese.

[0181] It can be seen from Comparative Example 4 that when the solid-liquid ratio of acid leaching is too low, the H + The concentration of is reduced, which reduces the leaching rate of lithium, nickel and cobalt, and slightly increases the leaching rate of manganese.

[0182] It can be seen from Comparative Example 5 that Cl - It is in the lowest oxidation state, has a certain reducibility, and has stronger reaction ability, which increases the leaching rate of lithium nickel cobalt, but the leaching rate of manganese is also relatively increased, and low-value leaching of manganese cannot be achieved.

[0183] Finally, it should be noted that those skilled in the art will readily conceive of other embodiments of the present invention after considering the specification and practicing the invention disclosed herein. The present invention is intended to cover any variations, uses or adaptations of the present invention, which follow the general principles of the present invention and include common knowledge or customary technical means in the art not disclosed by the present invention, are not limited to the precise structure described above and shown in the drawings, and may be modified and changed in various ways without departing from the scope thereof. The scope of the present invention is limited only by the appended claims.

Claims

1. A method for recovering positive electrode materials, characterized in that: The process includes the following: Mixing the positive electrode material of the ternary lithium battery with the first acid solution to obtain a first mixed system; performing a first acid leaching treatment on the first mixed system to obtain a first filtrate and manganese slag; Adjusting the pH value of the first filtrate to 8.5-12 to obtain a second filter residue and a second filtrate; In the ternary positive electrode material, the molar ratio of lithium element, nickel element, cobalt element and manganese element is a:x:y:(1-xy); The first acid solution includes sulfuric acid, and the ratio M of the amount of sulfuric acid in the first acid solution to the ternary positive electrode material satisfies the following relationship: 0.65×(a+2x+2y)≤M≤0.8×(a+2x+2y); The solid-liquid ratio of the first mixed system is 120-220 g / L; The treatment temperature of the first acid leaching treatment is 75-100°C; The treatment time of the first acid leaching treatment is greater than or equal to 180 minutes.

2. The method according to claim 1, characterized in that The ratio M of the amount of substance of the ternary positive electrode material to the sulfuric acid in the first acid solution satisfies the following relationship: 0.7×(a+2x+2y)≤M≤0.75×(a+2x+2y).

3. The method according to claim 1 or 2, characterized in that: The solid-liquid ratio of the first mixed system is 150-200 g / L.

4. The method according to any one of claims 1 to 3, characterized in that The treatment temperature of the first acid leaching treatment is 80-95°C.

5. A method for preparing a lithium manganese iron phosphate positive electrode material, characterized in that: The process includes the following: Using the positive electrode material recovery method according to any one of claims 1 to 4 to prepare manganese slag and a second filtrate; Mixing the lithium iron phosphate positive electrode material with the second acid solution and the oxidant to obtain a second mixed system; performing a second acid leaching treatment on the second mixed system to obtain a third filtrate and iron phosphate slag; mixing the second filtrate, the third filtrate and phosphoric acid to obtain a third mixed system; Adjusting the pH of the third mixed system to 10-11 to obtain lithium phosphate; Mixing the manganese slag, the iron phosphate slag, and the lithium phosphate to obtain a fourth mixed system; The fourth mixed system is calcined to obtain the lithium manganese iron phosphate positive electrode material.

6. The method for preparing the lithium iron manganese phosphate positive electrode material according to claim 5, characterized in that: The second acid solution includes sulfuric acid, and the ratio of the amount of sulfuric acid in the second acid solution to the amount of the lithium manganese iron phosphate positive electrode material is 0.5-1.5; and / or, The oxidant includes hydrogen peroxide, and the ratio of the amount of the hydrogen peroxide to the amount of the lithium manganese iron phosphate positive electrode material is 1-3.

7. The method for preparing the lithium iron manganese phosphate positive electrode material according to claim 5 or 6, characterized in that: The treatment temperature of the second acid leaching treatment is 25-90°C.

8. The method for preparing the lithium iron manganese phosphate positive electrode material according to any one of claims 5 to 7, characterized in that: In the third mixed system, the molar ratio of lithium element, manganese element, iron element and phosphorus element is (0.9-1.1): (0.3-0.5): (0.5-0.7): (0.9-1.1).

9. The method for preparing the lithium iron manganese phosphate positive electrode material according to any one of claims 5 to 8, characterized in that: The calcination treatment has a treatment temperature of 600-800° C. and a treatment time of 10-14 hours.

10. A lithium manganese iron phosphate positive electrode material, characterized in that: The method for preparing the lithium manganese iron phosphate positive electrode material according to any one of claims 5 to 9 is used to prepare the lithium manganese iron phosphate positive electrode material.

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