A method for preparing a lithium iron phosphate positive electrode material precursor from a laterite nickel ore hydrochloric acid leaching solution by ultrasonic intensification

Abstract

The application discloses a method for preparing a lithium iron phosphate positive electrode material precursor from laterite nickel ore hydrochloric acid leaching solution by ultrasonic intensification, and comprises the following steps: adding phosphoric acid into the laterite nickel ore hydrochloric acid leaching solution to obtain a mixed solution under the conditions of heating and stirring; adding a neutralizing agent to adjust the pH under the condition of ultrasonic field intensification of the mixing to obtain a neutralized slurry; performing solid-liquid separation on the obtained neutralized slurry to obtain dihydrate iron phosphate and a low-iron leaching solution; and washing and filtering the obtained dihydrate iron phosphate, and dehydrating the dihydrate iron phosphate at a certain temperature to obtain the lithium iron phosphate positive electrode material precursor. The application has the advantages of green recyclability, low loss rate of nickel and cobalt, low cost and environmental friendliness; no phosphorus pollution is generated in the solution, the neutralizing agent can be recycled, the prepared lithium iron phosphate precursor has high specific capacity, high-value utilization of impurity iron in the laterite nickel ore hydrochloric acid leaching solution is effectively realized, and the method is especially suitable for a system with high iron concentration in the leaching solution.

Description

Technical Field

[0001] This invention belongs to the field of wet process impurity removal technology for laterite nickel ore, and relates to a method for preparing lithium iron phosphate cathode material precursors by ultrasonic enhancement of hydrochloric acid leaching solution of laterite nickel ore. Background Technology

[0002] Nickel is a primary raw material for the production of stainless steel and non-ferrous metal alloys. In recent years, with the rapid expansion of the electric vehicle market, the demand for nickel, a key component of ternary cathode materials, has further increased. Currently, the most exploited nickel deposits globally are sulfide nickel ores, accounting for 30% of land-based nickel reserves. However, with the further increase in nickel demand and the gradual depletion of sulfide nickel ores, laterite nickel ores, accounting for approximately 70% of land-based nickel reserves, have attracted widespread attention. Currently, laterite nickel ores of the ferrosilicon-magnesium nickel ore type, with low iron content, are mainly processed using pyrometallurgical processes, which have very high grade requirements and can only produce ferronickel products, causing serious environmental problems. These drawbacks make hydrometallurgical processes increasingly attractive.

[0003] CN 111254281A discloses a method for pressurized phosphoric acid leaching of lateritic nickel ore. The method involves pressurizing a mixed slurry containing lateritic nickel ore and phosphoric acid solution under a temperature of 110–150°C and a pressure of 0.2–0.5 MPa for phosphoric acid leaching. Subsequent solid-liquid separation yields a leaching solution enriched with nickel and cobalt, and a micron-sized two-dimensional iron phosphate leaching residue. This method is environmentally friendly, but the process conditions are relatively harsh, the treatment cost is high, phosphorus-containing wastewater is difficult to treat, and the use of phosphoric acid as the leaching agent also increases the process cost.

[0004] Hydrochloric acid leaching of lateritic nickel ore offers significant advantages, including mild reaction conditions, high leaching rates, low technical risks, low equipment investment, and wider applicability to various mineral types. CN 109457112A discloses a method for treating lateritic nickel ore leaching solutions. The ore is first leached with hydrochloric acid under normal pressure, forming an acidic leaching solution containing Fe, Ni, Co, Cr, Al, Mn, and Mg. Then, an alkaline neutralizing agent is used to remove Fe, Cr, and Al from the acidic leaching solution, ultimately forming an acidic solution containing Ni, Co, Mn, and Mg. In the first impurity removal step, a large amount of Fe forms hydroxide precipitates with other impurities, resulting in low iron utilization value.

[0005] CN 113023701A discloses a method and application for separating nickel-iron from laterite nickel ore leaching solution and preparing ferric phosphate. The method involves adjusting the pH of the laterite nickel ore leaching solution to 0.5–1.5, adding a composite sulfide precipitant dropwise for reaction, adding a coagulant, filtering to obtain nickel sulfide precipitate and filtrate, then adding an oxidant and phosphoric acid solution to the filtrate, adjusting the pH, reacting, and then heating to concentrate and crystallize to obtain ferric phosphate. This invention achieves good separation results, but the introduction of neutralizing agents such as ammonia and composite sulfides increases the difficulty of subsequent processing and may cause environmental pollution.

[0006] CN 101575092A discloses a method for preparing lithium iron phosphate precursors by comprehensively utilizing laterite nickel ore. The method includes: fully leaching laterite nickel ore with acid; adding an oxidant and a precipitant to the leachate; controlling the morphology with a complexing agent or surfactant; controlling the pH of the system with an alkaline aqueous solution; reacting in a stirred reactor; washing, filtering, and drying the resulting precipitate to obtain the precursor of lithium iron phosphate, a cathode material for lithium-ion batteries. While this method comprehensively utilizes laterite nickel ore resources, the addition of oxidants, precipitants, complexing agents, and surfactants in the precipitation step introduces impurities, making subsequent purification of the nickel-cobalt solution difficult.

[0007] Therefore, how to provide a simple, clean, low-cost, and sustainable separation method to selectively remove and effectively utilize the large amount of iron impurities in the hydrochloric acid leaching solution of laterite nickel ore has become an urgent problem to be solved. Summary of the Invention

[0008] The purpose of this invention is to provide a method for the ultrasonic-enhanced and recyclable preparation of lithium iron phosphate cathode material precursors from laterite nickel ore leaching solution. The method uses the by-product MgO as a neutralizing agent and uses ultrasonic enhancement to adjust the morphology. This method can achieve the recycling of the neutralizing agent without introducing other impurities. Moreover, the process is environmentally friendly, simple to operate, and produces products with high purity.

[0009] To achieve this objective, the present invention adopts the following technical solution:

[0010] A method for preparing lithium iron phosphate cathode material precursors using laterite nickel ore hydrochloric acid leaching solution with ultrasonic enhancement, the method comprising the following steps:

[0011] (1) Add phosphoric acid to the hydrochloric acid leaching solution of laterite nickel ore and obtain a mixed solution under heating and stirring conditions;

[0012] (2) Under the condition of ultrasonic external field enhanced mixing, a neutralizing agent is added to adjust the pH to obtain a neutralized slurry;

[0013] (3) The obtained neutralized slurry is subjected to solid-liquid separation to obtain iron phosphate dihydrate and low iron leachate. The obtained iron phosphate dihydrate is washed, filtered, and dehydrated at a certain temperature to obtain lithium iron phosphate cathode material precursor.

[0014] Preferably, in step (1), the concentration of iron ions in the laterite nickel ore hydrochloric acid leaching solution is 2-200 g / L.

[0015] Preferably, in step (1), the amount of phosphoric acid added is 0.5-1.05 times the theoretical molar amount that will completely precipitate iron ions in the hydrochloric acid leaching solution of laterite nickel ore;

[0016] Preferably, in step (1), the heating reaction temperature is 40-90℃;

[0017] Preferably, in step (1), the stirring speed is 300-700 r / min.

[0018] Preferably, in step (2), the neutralizing agent used for neutralization and hydrolysis is magnesium oxide produced by the pyrolysis of magnesium chloride in the hydrochloric acid leaching waste liquid of laterite nickel ore, and the mass percentage concentration of magnesium oxide in the neutralizing agent slurry is 10%-50%.

[0019] Preferably, in step (2), the endpoint of neutralization is the pH value of the slurry after precipitation being 0-3;

[0020] Preferably, in step (2), the frequency of the ultrasonic field in the external ultrasonic field is 30-80kHz, and the power is 100-400W / cm². 2 ;

[0021] Preferably, in step (3), the detergent used for washing is any one or two of dilute hydrochloric acid and dilute phosphoric acid, and the acid wash is followed by 2-4 water washes.

[0022] Preferably, in step (3), the dehydration temperature is 400℃-700℃ and the dehydration time is 2-6 hours.

[0023] As a preferred embodiment of the method described in this invention, the method includes the following steps:

[0024] (1) Add phosphoric acid to the hydrochloric acid leaching solution of limonite-type laterite nickel ore, wherein the amount of phosphoric acid added is 0.5-1 times the theoretical molar amount for complete precipitation of iron ions, and obtain a mixed solution under the conditions of heating at 40-90℃ and stirring at 300-700r / min.

[0025] (2) At a frequency of 30-80kHz and a power of 100-400W / cm 2 Under ultrasonic field enhanced mixing conditions, MgO slurry was added to adjust the pH to 0-3, resulting in a neutralized slurry.

[0026] (3) The obtained neutralized slurry is subjected to solid-liquid separation to obtain iron phosphate dihydrate and low iron leachate. The obtained iron phosphate dihydrate is acid washed, water washed, filtered, and dehydrated at 400℃-700℃ for 2-6 hours to obtain lithium iron phosphate cathode material precursor.

[0027] This invention uses magnesium oxide, a byproduct of the hydrochloric acid wet process system of laterite nickel ore, as a neutralizing agent to perform ultrasonic-assisted co-precipitation treatment on the hydrochloric acid leachate of laterite nickel ore, directly preparing lithium iron phosphate precursor in a complex system with high iron concentration, and obtaining nickel-cobalt-rich low iron leachate.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] The method described in this invention uses MgO, a byproduct of the hydrochloric acid wet process in laterite nickel ore, as a neutralizing agent. This not only allows for the recycling of the neutralizing agent without introducing other impurities, but also avoids the formation of ferric hydroxide precipitate due to excessive local alkali concentration caused by the addition of a strong alkaline neutralizing agent. It offers advantages such as low cost and environmental friendliness. The use of ultrasonic external field-assisted precipitation enhances local turbulence and micro-mixing, reducing the loss of key elements such as nickel and cobalt caused by excessively high local pH during neutralizing agent addition. This results in a high-purity, highly uniform, spherical, and high-specific-capacity lithium iron phosphate cathode material precursor. The prepared ferric phosphate is added to the acid washing step to avoid the oxidation and precipitation of divalent iron during water washing, which would affect product quality. The nickel and cobalt recovery rates of this invention both reach over 99%, and the solution is completely free of phosphorus. Using the ferric phosphate as raw material, the final prepared lithium iron phosphate can achieve a discharge capacity of over 160 mAh / g at 0.1C, effectively realizing the high-value utilization of iron impurities in the hydrochloric acid leaching solution of laterite nickel ore, and is particularly suitable for leaching systems with high iron content. Attached Figure Description

[0030] Figure 1 Here is a SEM image of the iron phosphate prepared according to this invention;

[0031] Figure 2 This is a TEM image of the iron phosphate prepared according to the present invention. Detailed Implementation

[0032] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0033] To demonstrate the treatment effect of the method described in this invention, the hydrochloric acid leaching solution of laterite nickel ore used in the specific embodiment of this invention is the same laterite nickel ore hydrochloric acid leaching solution, with the following concentrations: iron ion concentration of 34.67 g / L, nickel ion concentration of 0.74 g / L, cobalt ion concentration of 0.08 g / L, manganese ion concentration of 0.62 g / L, aluminum ion concentration of 1.75 g / L, chromium ion concentration of 0.73 g / L, and magnesium ion concentration of 0.62 g / L.

[0034] Example 1

[0035] This embodiment provides a method for preparing lithium iron phosphate cathode material precursors using laterite nickel ore hydrochloric acid leaching solution with ultrasonic enhancement, comprising the following steps:

[0036] (1) Add phosphoric acid to the hydrochloric acid leaching solution of laterite nickel ore, wherein the amount of phosphoric acid added is 1 times the theoretical molar amount that can completely precipitate iron ions, and obtain a mixed solution under the conditions of heating at 50°C and stirring at 500 r / min.

[0037] (2) At a frequency of 40kHz and a power of 200W / cm 2Under ultrasonic field enhanced mixing conditions, 20% MgO slurry was added to adjust the pH to 1, resulting in a neutralized slurry.

[0038] (3) The obtained neutralized slurry was subjected to solid-liquid separation to obtain iron phosphate dihydrate and low iron leachate. The obtained iron phosphate dihydrate was acid washed, water washed, filtered, and dehydrated at 650°C for 4 hours to obtain lithium iron phosphate cathode material precursor.

[0039] The measurements showed that the recovery rates of nickel and cobalt were 99.47% and 99.1%, respectively, and the iron ion removal rate was 95.75%. The solution after iron removal was completely free of phosphorus, and the iron-to-phosphorus ratio of the ferric phosphate product was 0.99. Figure 1 and Figure 2 As shown, the particles are uniformly distributed, and the secondary grain size is about 260 nm. The lithium iron phosphate cathode material was prepared and assembled into a CR2032 half cell. The discharge specific capacity was measured to be 162 mAh / g using the Blue Electric test system.

[0040] Example 2

[0041] This embodiment provides a method for preparing lithium iron phosphate cathode material precursors using laterite nickel ore hydrochloric acid leaching solution with ultrasonic enhancement, comprising the following steps:

[0042] (1) Add phosphoric acid to the hydrochloric acid leaching solution of laterite nickel ore, wherein the amount of phosphoric acid added is 0.5 times the theoretical molar amount that can completely precipitate iron ions, and obtain a mixed solution under the conditions of heating at 50°C and stirring at 500 r / min;

[0043] (2) At a frequency of 40kHz and a power of 200W / cm 2 Under ultrasonic field enhanced mixing conditions, 20% MgO slurry was added to adjust the pH to 1, resulting in a neutralized slurry.

[0044] (3) The obtained neutralized slurry was subjected to solid-liquid separation to obtain iron phosphate dihydrate and low iron leachate. The obtained iron phosphate dihydrate was acid washed, water washed, filtered, and dehydrated at 650°C for 4 hours to obtain lithium iron phosphate cathode material precursor.

[0045] After testing, the recovery rates of nickel and cobalt were 99.7% and 99.5%, respectively, the removal rate of iron ions was 49.5%, the iron-to-phosphorus ratio of the iron phosphate product was 1.09, the particle distribution was uniform, and the secondary grain size was about 220 nm. The lithium iron phosphate cathode material was prepared and assembled into a CR2032 half cell. The discharge specific capacity was measured to be 160 mAh / g using the Blue Electric test system.

[0046] Example 3

[0047] This embodiment provides a method for the ultrasonic-enhanced recyclable preparation of lithium iron phosphate cathode materials from limonite-type laterite nickel ore leaching solution, comprising the following steps:

[0048] (1) Phosphoric acid is added to the hydrochloric acid leaching solution of limonite-type laterite nickel ore, wherein the amount of phosphoric acid added is 1 times the theoretical molar amount for complete precipitation of iron ions, and a mixed solution is obtained under the conditions of heating at 50°C and stirring at 500 r / min.

[0049] (2) At a frequency of 40kHz and a power of 400W / cm 2 Under ultrasonic field enhanced mixing conditions, 20% MgO slurry was added to adjust the pH to 1, resulting in a neutralized slurry.

[0050] (3) The obtained neutralized slurry was subjected to solid-liquid separation to obtain iron phosphate dihydrate and low iron leachate. The obtained iron phosphate dihydrate was acid washed, water washed, filtered, and dehydrated at 650°C for 4 hours to obtain lithium iron phosphate cathode material precursor.

[0051] After testing, the recovery rates of nickel and cobalt were 99.5% and 99.16%, respectively, the removal rate of iron ions was 96.1%, the iron-to-phosphorus ratio of the iron phosphate product was 0.99, the particle distribution was uniform, and the secondary grain size was about 170 nm. The lithium iron phosphate cathode material was prepared and assembled into a CR2032 half cell. The discharge specific capacity was measured to be 165 mAh / g using the Blue Electric test system.

[0052] Example 4

[0053] This embodiment provides a method for the ultrasonic-enhanced recyclable preparation of lithium iron phosphate cathode materials from limonite-type laterite nickel ore leaching solution, comprising the following steps:

[0054] (1) Phosphoric acid is added to the hydrochloric acid leaching solution of limonite-type laterite nickel ore, wherein the amount of phosphoric acid added is 1 times the theoretical molar amount for complete precipitation of iron ions, and a mixed solution is obtained under the conditions of heating at 50°C and stirring at 500 r / min.

[0055] (2) At a frequency of 25kHz and a power of 200W / cm 2 Under ultrasonic field enhanced mixing conditions, 20% MgO slurry was added to adjust the pH to 1, resulting in a neutralized slurry.

[0056] (3) The obtained neutralized slurry was subjected to solid-liquid separation to obtain iron phosphate dihydrate and low iron leachate. The obtained iron phosphate dihydrate was acid washed, water washed, filtered, and dehydrated at 650°C for 4 hours to obtain lithium iron phosphate cathode material precursor.

[0057] After testing, the recovery rates of nickel and cobalt were 99.3% and 99%, respectively, the removal rate of iron ions was 95.9%, the iron-to-phosphorus ratio of the iron phosphate product was 0.99, the particle distribution was uniform, and the secondary grain size was about 310 nm. The lithium iron phosphate cathode material was prepared and assembled into a CR2032 half cell. The discharge specific capacity was measured to be 160 mAh / g using the Blue Electric test system.

[0058] Example 5

[0059] This embodiment provides a method for the ultrasonic-enhanced recyclable preparation of lithium iron phosphate cathode materials from limonite-type laterite nickel ore leaching solution, comprising the following steps:

[0060] (1) Phosphoric acid is added to the hydrochloric acid leaching solution of limonite-type laterite nickel ore, wherein the amount of phosphoric acid added is 1 times the theoretical molar amount for complete precipitation of iron ions, and a mixed solution is obtained under the conditions of heating at 50°C and stirring at 500 r / min.

[0061] (2) At a frequency of 40kHz and a power of 200W / cm 2 Under ultrasonic field enhanced mixing conditions, 80% MgO was added to adjust the pH to 1, resulting in a neutralized slurry.

[0062] (3) The obtained neutralized slurry was subjected to solid-liquid separation to obtain iron phosphate dihydrate and low iron leachate. The obtained iron phosphate dihydrate was acid washed, water washed, filtered, and dehydrated at 650°C for 4 hours to obtain lithium iron phosphate cathode material precursor.

[0063] After testing, the recovery rates of nickel and cobalt were 97.16% and 98.2%, respectively, the removal rate of iron ions was 96.3%, the iron-to-phosphorus ratio of the iron phosphate product was 0.99, the particle distribution was uniform, and the secondary grain size was about 290 nm. The lithium iron phosphate cathode material was prepared and assembled into a CR2032 half cell. The discharge specific capacity was measured to be 155 mAh / g using the Blue Electric test system.

[0064] Example 6

[0065] This embodiment provides a method for the ultrasonic-enhanced recyclable preparation of lithium iron phosphate cathode materials from limonite-type laterite nickel ore leaching solution, comprising the following steps:

[0066] (1) Phosphoric acid is added to the hydrochloric acid leaching solution of limonite-type laterite nickel ore, wherein the amount of phosphoric acid added is 1 times the theoretical molar amount for complete precipitation of iron ions, and a mixed solution is obtained under the conditions of heating at 50°C and stirring at 500 r / min.

[0067] (2) At a frequency of 40kHz and a power of 200W / cm 2 Under ultrasonic field enhanced mixing conditions, 20% MgO slurry was added to adjust the pH to 2, resulting in a neutralized slurry.

[0068] (3) The obtained neutralized slurry was subjected to solid-liquid separation to obtain iron phosphate dihydrate and low iron leachate. The obtained iron phosphate dihydrate was acid washed, water washed, filtered, and dehydrated at 650°C for 4 hours to obtain lithium iron phosphate cathode material precursor.

[0069] After testing, the recovery rates of nickel and cobalt were 97.2% and 98.5%, respectively, the removal rate of iron ions was 97%, the iron-to-phosphorus ratio of the iron phosphate product was 0.99, the particle distribution was uniform, and the secondary grain size was about 200 nm. The lithium iron phosphate cathode material was prepared and assembled into a CR2032 half cell. The discharge specific capacity was measured to be 165 mAh / g using the Blue Electric test system.

[0070] Example 7

[0071] This embodiment provides a method for the ultrasonic-enhanced recyclable preparation of lithium iron phosphate cathode materials from limonite-type laterite nickel ore leaching solution, comprising the following steps:

[0072] (1) Phosphoric acid is added to the hydrochloric acid leaching solution of limonite-type laterite nickel ore, wherein the amount of phosphoric acid added is 1 times the theoretical molar amount for complete precipitation of iron ions, and a mixed solution is obtained under the conditions of heating at 50°C and stirring at 700 r / min.

[0073] (2) At a frequency of 40kHz and a power of 200W / cm 2 Under ultrasonic field enhanced mixing conditions, 20% MgO slurry was added to adjust the pH to 1, resulting in a neutralized slurry.

[0074] (3) The obtained neutralized slurry was subjected to solid-liquid separation to obtain iron phosphate dihydrate and low iron leachate. The obtained iron phosphate dihydrate was acid washed, water washed, filtered, and dehydrated at 650°C for 4 hours to obtain lithium iron phosphate cathode material precursor.

[0075] After testing, the recovery rates of nickel and cobalt were 99.6% and 99.4%, respectively, the removal rate of iron ions was 95.6%, the iron-to-phosphorus ratio of the iron phosphate product was 0.99, the particle distribution was uniform, and the secondary grain size was about 210 nm. The lithium iron phosphate cathode material was prepared and assembled into a CR2032 half cell. The discharge specific capacity was measured to be 164 mAh / g using the Blue Electric test system.

[0076] Example 8

[0077] This embodiment provides a method for preparing lithium iron phosphate cathode material precursors using laterite nickel ore hydrochloric acid leaching solution with ultrasonic enhancement, comprising the following steps:

[0078] (1) Add phosphoric acid to the hydrochloric acid leaching solution of laterite nickel ore, wherein the amount of phosphoric acid added is 1 times the theoretical molar amount that can completely precipitate iron ions, and obtain a mixed solution under the conditions of heating at 50°C and stirring at 500 r / min.

[0079] (2) At a frequency of 40kHz and a power of 200W / cm 2 Under ultrasonic field enhanced mixing conditions, 20% MgO slurry was added to adjust the pH to 1, resulting in a neutralized slurry.

[0080] (3) The obtained neutralized slurry was subjected to solid-liquid separation to obtain iron phosphate dihydrate and low iron leachate. The obtained iron phosphate dihydrate was acid washed, water washed, filtered, and dehydrated at 650°C for 2 hours to obtain lithium iron phosphate cathode material precursor.

[0081] After testing, the recovery rates of nickel and cobalt were 99.5% and 99%, respectively, the removal rate of iron ions was 95%, the solution after iron removal was completely free of phosphorus, the iron-phosphorus ratio of the iron phosphate product was 0.99, the particle distribution was uniform, the secondary grain size was about 260nm, the lithium iron phosphate cathode material was prepared and assembled into a CR2032 half cell, and the discharge specific capacity was measured to be 158mAh / g using the Blue Electric test system.

[0082] Example 9

[0083] This embodiment provides a method for preparing lithium iron phosphate cathode material precursors using laterite nickel ore hydrochloric acid leaching solution with ultrasonic enhancement, comprising the following steps:

[0084] (1) Add phosphoric acid to the hydrochloric acid leaching solution of laterite nickel ore, wherein the amount of phosphoric acid added is 1 times the theoretical molar amount that can completely precipitate iron ions, and obtain a mixed solution under the conditions of heating at 50°C and stirring at 500 r / min.

[0085] (2) At a frequency of 40kHz and a power of 200W / cm 2 Under ultrasonic field enhanced mixing conditions, 20% MgO slurry was added to adjust the pH to 1, resulting in a neutralized slurry.

[0086] (3) The obtained neutralized slurry was subjected to solid-liquid separation to obtain iron phosphate dihydrate and low iron leachate. The obtained iron phosphate dihydrate was acid washed, water washed, filtered, and dehydrated at 450°C for 4 hours to obtain lithium iron phosphate cathode material precursor.

[0087] After testing, the recovery rates of nickel and cobalt were 99.4% and 99.2%, respectively, and the removal rate of iron ions was 95.8%. The solution after iron removal was completely free of phosphorus. The iron-phosphorus ratio of the iron phosphate product was 0.99, the particle distribution was uniform, and the secondary grain size was about 260 nm. The lithium iron phosphate cathode material was prepared and assembled into a CR2032 half-cell. The discharge specific capacity was measured to be 161 mAh / g using the Blue Electric test system.

[0088] Comparative Example 1

[0089] This comparative example provides a method for the ultrasonic-enhanced recyclable preparation of lithium iron phosphate cathode materials from limonite-type laterite nickel ore leaching solution, comprising the following steps:

[0090] (1) Phosphoric acid is added to the hydrochloric acid leaching solution of limonite-type laterite nickel ore, wherein the amount of phosphoric acid added is 1 times the theoretical molar amount for complete precipitation of iron ions, and a mixed solution is obtained under the conditions of heating at 50°C and stirring at 500 r / min.

[0091] (2) Add 10% sodium hydroxide to adjust the pH to 1 without ultrasonic external field strengthening mixing to obtain neutralized slurry;

[0092] (3) The obtained neutralized slurry was subjected to solid-liquid separation to obtain iron phosphate dihydrate and low iron leachate. The obtained iron phosphate dihydrate was acid washed, water washed, filtered, and dehydrated at 650°C for 4 hours to obtain lithium iron phosphate cathode material precursor.

[0093] After testing, the recovery rates of nickel and cobalt were 92% and 90%, respectively, the removal rate of iron ions was 95%, the iron-to-phosphorus ratio of the iron phosphate product was 0.92, the particle distribution was uneven, and the secondary grain size was about 3μm. The lithium iron phosphate cathode material was prepared and assembled into a CR2032 half cell. The discharge specific capacity was measured to be 132mAh / g using the Blue Electric test system.

[0094] As shown in Comparative Example 1, ultrasonic field-enhanced precipitation plays an important role in reducing the loss of valuable nickel and cobalt elements and improving the quality of iron phosphate products.

[0095] In summary, the method of this invention uses MgO, a byproduct of the hydrochloric acid wet process in laterite nickel ore, as a neutralizing agent. This allows for the recycling of the neutralizing agent without introducing other impurities, offering advantages such as low cost and environmental friendliness. The use of ultrasonic external field-assisted precipitation enhances local turbulence and micro-mixing, reducing the loss of key elements like nickel and cobalt caused by excessively high local pH during neutralizing agent addition. This results in a high-purity, highly uniform, and spherical lithium iron phosphate cathode material precursor. The nickel and cobalt recovery rates of this invention both exceed 99%, and the iron removal rate exceeds 95%. Using the product iron phosphate as raw material, the final prepared lithium iron phosphate exhibits a discharge capacity of over 160 mAh / g at 0.1C, effectively realizing the high-value utilization of iron impurities in the hydrochloric acid leaching solution of limonite-type laterite nickel ore.

[0096] The upper and lower limits of the process parameters (such as temperature, time, etc.) and the range values ​​of the present invention can all achieve the method, and examples are not listed here.

[0097] All aspects not described in detail in this invention can be covered using conventional technical knowledge in the field.

[0098] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to the embodiments, those skilled in the art should understand that modifications or equivalent substitutions to the technical solutions of the present invention do not depart from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for preparing lithium iron phosphate cathode material precursors by ultrasonic enhancement of laterite nickel ore hydrochloric acid leaching solution, the method comprising the following steps: (1) Add phosphoric acid to the hydrochloric acid leaching solution of laterite nickel ore and obtain a mixed solution under heating and stirring conditions; (2) Under the condition of ultrasonic external field enhanced mixing, a neutralizing agent is added to adjust the pH to obtain a neutralized slurry; the neutralizing agent is magnesium oxide produced by the pyrolysis of magnesium chloride in the hydrochloric acid leaching waste liquid of laterite nickel ore, and the mass percentage concentration of magnesium oxide in the neutralizing agent slurry is 10%-50%. (3) The obtained neutralized slurry is subjected to solid-liquid separation to obtain iron phosphate dihydrate and low iron leachate. The obtained iron phosphate dihydrate is washed, filtered, and dehydrated at a certain temperature to obtain lithium iron phosphate cathode material precursor.

2. The method according to claim 1, characterized in that, In step (1), the concentration of iron ions in the laterite nickel ore hydrochloric acid leaching solution is 2-200 g / L; the amount of phosphoric acid added is 0.5-1.05 times the theoretical molar amount that can completely precipitate iron ions in the laterite nickel ore hydrochloric acid leaching solution; the heating reaction temperature is 40-90℃; and the stirring speed is 300-700 r / min.

3. The method according to claim 1, characterized in that, In step (2), the endpoint of the neutralizing agent adjusting the pH is the pH value of the slurry after precipitation being 0-3.

4. The method according to claim 1, characterized in that, In step (2), the ultrasonic field frequency of the external ultrasonic field is 30-80kHz, and the power is 100-400W / cm. 2 .

5. The method according to claim 1, characterized in that, In step (3), the detergent used for washing is any one or a mixture of two of dilute hydrochloric acid and dilute phosphoric acid, and the acid wash is followed by 2-4 water washes.

6. The method according to any one of claims 1-5, characterized in that, In step (3), the dehydration temperature is 400℃-700℃ and the dehydration time is 2-6 hours.

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