阅读说明：本技术 单水合氢氧化锂及其制备方法和用途以及锂离子电池正极材料和锂离子电池 (Lithium hydroxide monohydrate, preparation method and application thereof, lithium ion battery anode material and lithium ion battery ) 是由 徐云玲 李阳 曹文玉 徐茶清 周虎 于 2018-08-14 设计创作，主要内容包括：本公开涉及一种单水合氢氧化锂及其制备方法和用途以及锂离子电池正极材料和锂离子电池,该单水合氢氧化锂的粒径大小为100～380nm,以重量计,所述单水合氢氧化锂中Cu的含量小于1ppm,Cr的含量小于1ppm,Ni的含量为2ppm以下,Zn的含量为2ppm以下,Fe的含量为4ppm以下。该单水合氢氧化锂具有较低的磁性元素含量,用于制备锂离子电池正极材料时能够改善锂离子电池的使用寿命并降低其自放电效应。(The present disclosure relates to lithium hydroxide monohydrate, a preparation method and a use thereof, a lithium ion battery positive electrode material and a lithium ion battery, wherein the lithium hydroxide monohydrate has a particle size of 100-380 nm, and by weight, the content of Cu in the lithium hydroxide monohydrate is less than 1ppm, the content of Cr is less than 1ppm, the content of Ni is less than 2ppm, the content of Zn is less than 2ppm, and the content of Fe is less than 4 ppm. The lithium hydroxide monohydrate has low magnetic element content, and can improve the service life of the lithium ion battery and reduce the self-discharge effect of the lithium ion battery when being used for preparing the lithium ion battery anode material.)

1. The lithium hydroxide monohydrate is characterized in that the particle size of the lithium hydroxide monohydrate is 100-380 nm, and the lithium hydroxide monohydrate contains less than 1ppm of Cu, less than 1ppm of Cr, less than 2ppm of Ni, less than 2ppm of Zn and less than 4ppm of Fe by weight.

2. The lithium hydroxide monohydrate according to claim 1, wherein the purity of the lithium hydroxide monohydrate is 99.53 to 99.89%.

3. A process for preparing lithium hydroxide monohydrate from a lithium-containing brine, comprising the steps of:

s1, contacting lithium-containing brine with a lithium adsorbent for adsorption treatment, and then contacting pure water with the adsorbed lithium adsorbent for leaching and washover treatment to obtain a lithium-containing desorption solution;

s2, performing membrane separation treatment on the lithium-containing desorption solution to obtain lithium-rich brine; the membrane separation treatment comprises nanofiltration treatment, reverse osmosis treatment and electrodialysis treatment;

s3, carrying out chemical precipitation treatment or ion exchange treatment on the lithium-rich brine to obtain a refined lithium-rich solution;

s4, performing bipolar membrane electrodialysis treatment on the refined lithium-rich solution to obtain a crude lithium hydroxide aqueous solution;

and S5, evaporating and crystallizing the crude lithium hydroxide aqueous solution, and collecting crystal precipitates.

4. The method according to claim 3, wherein in step S1, the lithium adsorbent is an aluminum salt adsorbent, an ion sieve type oxide adsorbent, an amorphous hydroxide adsorbent, a manganese-based adsorbent, or a titanium-based adsorbent; based on the volume of the lithium-containing brine, the dosage of the lithium adsorbent is 30-180 g/L;

the leaching treatment conditions comprise: the weight ratio of the leaching water to the lithium adsorbent is (0.6-3): 1, leaching at the speed of 6-12 BV/h;

the conditions of the washover treatment comprise: the weight ratio of the washing water to the lithium adsorbent is (2.5-8): 1.

5. the method of claim 3, wherein in step S1, the washover process comprises:

contacting the leached lithium adsorbent with secondary washing liquid to perform first washing treatment to obtain lithium-containing desorption liquid;

contacting the lithium adsorbent subjected to the first set of washing treatment with a primary set of washing liquid to perform second set of washing treatment to obtain a secondary set of washing liquid;

and contacting the lithium adsorbent subjected to the second set of washing treatment with pure water to perform third set of washing treatment to obtain the primary set of washing liquid.

6. The method according to claim 3, wherein in step S1, Li in the lithium-containing desorption solution⁺100 to 800ppm of Mg²⁺The content is 500-5000 ppm, and the total content of magnetic element ions is below 23 ppm.

7. The method of claim 3, wherein the nanofiltration treatment conditions comprise: the operating pressure is 0.2-4.0 MPa, preferably 0.5-3.5 MPa; the operation temperature is 10-40 ℃, and preferably 20-30 ℃;

adopting a reverse osmosis membrane to carry out reverse osmosis concentration treatment, wherein the conditions of the reverse osmosis concentration treatment comprise: the operation pressure is 2.0-4.0 MPa, and the operation temperature is 10-40 ℃;

performing electrodialysis treatment by adopting an electrodialysis membrane, wherein the electrodialysis membrane is one of an alloy membrane, a homogeneous membrane and a divalent ion separation membrane; the conditions of the electrodialysis treatment comprise: the single pair of membrane voltage is 0.1-3V, preferably 0.2-2.5V; the operation temperature is 5-40 ℃, and preferably 20-30 ℃.

8. The method of claim 3, wherein in step S2, the membrane separation process comprises the following steps in sequence: primary nanofiltration treatment, reverse osmosis treatment, secondary nanofiltration treatment and electrodialysis treatment.

9. The method of claim 3, wherein in step S2, Li in the lithium-rich brine⁺The content of the Mg is 4800-16370 ppm²⁺The content is 20-200 ppm, and the total content of magnetic element ions is below 14 ppm;

in step S3, the chemical precipitation process includes: mixing an alkaline reagent with the lithium-rich brine, and removing precipitates to obtain the refined lithium-rich solution; the alkaline reagent is sodium carbonate, ammonium carbonate, potassium carbonate, sodium hydroxide or potassium hydroxide;

in step S4, the conditions of the bipolar membrane electrodialysis treatment include: the voltage of the single pair of membranes is 0.5-3V, and the current density of the membrane is 100-1000A/m²Run ofThe temperature is 10-40 ℃.

10. The method according to claim 3, further comprising the steps of washing and drying after collecting the crystallized precipitate.

11. Lithium hydroxide monohydrate prepared by the process according to any one of claims 3 to 10.

12. Use of the lithium hydroxide monohydrate of any one of claims 1-2 and 11 in the preparation of a positive electrode material for a lithium ion battery.

13. A lithium ion battery positive electrode material, characterized in that it comprises the lithium hydroxide monohydrate according to any one of claims 1 to 2 and 11.

14. A lithium ion battery comprising the lithium ion battery positive electrode material according to claim 13.

Technical Field

The disclosure relates to the technical field of membrane separation, in particular to lithium hydroxide monohydrate, a preparation method and application thereof, a lithium ion battery anode material and a lithium ion battery.

Background

The lithium hydroxide monohydrate is used as an important industrial raw material and is widely applied to the fields of chemical industry, national defense, aerospace and energy storage. The lithium-based lubricating grease produced by the lithium hydroxide monohydrate has the advantages of good oxidation resistance and fire resistance, wide applicable temperature range, stable cycle performance and the like. In the field of national defense, the metal surface protective agent can be used as a heat carrier of a nuclear reactor and a protective agent for metal surfaces. In the aerospace field, lithium hydroxide monohydrate can be used to purify air in submarines, and as a respiratory mask for aviation pilots. Particularly, with the rapid development of the lithium battery industry, the demand of lithium hydroxide monohydrate as one of important lithium salts for preparing the positive electrode material of the lithium battery is greatly increased.

It is known that the lithium ion battery positive electrode material has high requirements on magnetic substances, because the introduction of the magnetic substances will aggravate the self-discharge behavior of the battery and cause a series of safety problems. Therefore, the production process of the power battery positive electrode material can strictly control the magnetic substances from the screening of raw materials to the control of the production environment and process. Lithium hydroxide is the first choice lithium salt raw material for synthesizing the ternary cathode material by the solid phase method at present, so the content of the magnetic substance of the lithium hydroxide is also a key index for judging whether the lithium hydroxide is qualified or not. In addition, the residual lithium amount of the cathode material is also a key parameter, the lithium salt and the ternary precursor are mixed uniformly to the extent that the residual lithium amount of the cathode material is directly influenced, the better the mixing uniformity is, the more beneficial the reduction of the residual lithium amount is, the lithium hydroxide monohydrate with nano-sized primary particles is easily and uniformly mixed with the ternary precursor, so that the development of the lithium hydroxide with nano-sized primary particles is urgently needed.

At present, because the magnetic elements in lithium ore are numerous and the removal process is very complicated, the content of impurity elements and magnetic substances of lithium hydroxide produced by most manufacturers cannot meet the requirement of lithium hydroxide for batteries based on the consideration of production cost. Secondly, because the synthesis method and conditions are not controlled, the obtained lithium hydroxide has larger primary particle size, and is not beneficial to the uniform mixing with the ternary precursor. In addition, the resource reserve of ore lithium in China is very limited, and the method for extracting lithium from lithium ore is difficult to meet the requirement of increasing battery capacity.

The salt lake brine in China contains abundant lithium resources and has great exploitation value, so that the heat of extracting lithium from the salt lake brine is higher and higher in recent years. Then, because most of the salt lake brine in China has the characteristic of high magnesium-lithium ratio, the mining difficulty is huge, for example, the document CN107720785A discloses a method for preparing lithium hydroxide based on a membrane separation technology, in the document, diluted old brine is directly used as nanofiltration stock solution, because the Mg ion concentration in the salt lake old brine is very high (70000-100000ppm), a large amount of pure water is consumed to dilute the brine (more than 10 times of the volume of the brine), so as to meet the requirement that the concentration of divalent ions in the nanofiltration stock solution is lower than 8000ppm, which not only greatly increases the water amount to be treated in the nanofiltration and the subsequent processes, causes large equipment scale and high equipment cost, and because the diluted old brine contains more divalent and multivalent ions including magnetic elements, the impurity removal effect in the nanofiltration membrane separation process is not ideal, and the lithium hydroxide monohydrate with low magnetic content is not favorably obtained. Secondly, hydrochloric acid is needed to adjust the acidity in the patent process, which is not beneficial to environmental protection. In addition, the ion exchange section of the patent is positioned after the nanofiltration process, so that the use amount of the resin is increased, and the corresponding impurity ion concentration is increased in the subsequent lithium enrichment and concentration process, thereby possibly causing the content of the impurity ions containing magnetic elements in the final product, namely the lithium hydroxide monohydrate, to be higher. Therefore, the development of the technology for preparing the lithium hydroxide monohydrate with low magnetism, high purity and nano-scale primary particles from the salt lake brine is of great significance.

Disclosure of Invention

The purpose of the disclosure is to solve the problem that the existing technology is difficult to obtain the lithium hydroxide monohydrate with low magnetic substance content and nano-scale primary particles, and provide the lithium hydroxide monohydrate, the preparation method and the application thereof, the lithium ion battery anode material and the lithium ion battery.

To achieve the above object, a first aspect of the present disclosure: provided is lithium hydroxide monohydrate having a particle size of 100 to 380nm, wherein the lithium hydroxide monohydrate has a Cu content of less than 1ppm, a Cr content of less than 1ppm, a Ni content of 2ppm or less, a Zn content of 2ppm or less, and an Fe content of 4ppm or less, by weight.

Optionally, the purity of the lithium hydroxide monohydrate is 99.53-99.89%.

In a second aspect of the present disclosure: there is provided a process for preparing lithium hydroxide monohydrate from a lithium-containing brine comprising the steps of:

s1, contacting lithium-containing brine with a lithium adsorbent for adsorption treatment, and then contacting pure water with the adsorbed lithium adsorbent for leaching and washover treatment to obtain a lithium-containing desorption solution;

s2, performing membrane separation treatment on the lithium-containing desorption solution to obtain lithium-rich brine; the membrane separation treatment comprises nanofiltration treatment, reverse osmosis treatment and electrodialysis treatment;

s3, carrying out chemical precipitation treatment or ion exchange treatment on the lithium-rich brine to obtain a refined lithium-rich solution;

s4, performing bipolar membrane electrodialysis treatment on the refined lithium-rich solution to obtain a crude lithium hydroxide aqueous solution;

and S5, evaporating and crystallizing the crude lithium hydroxide aqueous solution, and collecting crystal precipitates.

Alternatively, in step S1, the lithium adsorbent is an aluminum salt adsorbent, an ion sieve type oxide adsorbent, an amorphous hydroxide adsorbent, a manganese-based adsorbent, or a titanium-based adsorbent; based on the volume of the lithium-containing brine, the dosage of the lithium adsorbent is 30-180 g/L;

the leaching treatment conditions comprise: the weight ratio of the leaching water to the lithium adsorbent is (0.6-3): 1, leaching at the speed of 6-12 BV/h;

the conditions of the washover treatment comprise: the weight ratio of the washing water to the lithium adsorbent is (2.5-8): 1.

Optionally, in step S1, the washover process includes:

contacting the leached lithium adsorbent with secondary washing liquid to perform first washing treatment to obtain lithium-containing desorption liquid;

contacting the lithium adsorbent subjected to the first set of washing treatment with a primary set of washing liquid to perform second set of washing treatment to obtain a secondary set of washing liquid;

and contacting the lithium adsorbent subjected to the second set of washing treatment with pure water to perform third set of washing treatment to obtain the primary set of washing liquid.

Optionally, in step S1, Li in the lithium-containing desorption solution ⁺100 to 800ppm of Mg²⁺The content is 500-5000 ppm, and the total content of magnetic element ions is below 23 ppm.

Optionally, performing nanofiltration treatment by using a nanofiltration membrane, wherein the aperture of the nanofiltration membrane is 1-2 nm; the nanofiltration membrane is a polyamide nanofiltration membrane, a polyether sulfone nanofiltration membrane, an aromatic polyamide composite membrane or a mixed composite nanofiltration membrane; the nanofiltration treatment conditions comprise: the operating pressure is 0.2-4.0 MPa, preferably 0.5-3.5 MPa; the operation temperature is 10-40 ℃, and preferably 20-30 ℃;

adopting a reverse osmosis membrane to carry out reverse osmosis concentration treatment, wherein the conditions of the reverse osmosis concentration treatment comprise: the operation pressure is 2.0-4.0 MPa, and the operation temperature is 10-40 ℃;

performing electrodialysis treatment by adopting an electrodialysis membrane, wherein the electrodialysis membrane is one of an alloy membrane, a homogeneous membrane and a divalent ion separation membrane; the conditions of the electrodialysis treatment comprise: the single pair of membrane voltage is 0.1-3V, preferably 0.2-2.5V; the operation temperature is 5-40 ℃, and preferably 20-30 ℃.

Alternatively, in step S2, the membrane separation process includes the following steps in order: primary nanofiltration treatment, reverse osmosis treatment, secondary nanofiltration treatment and electrodialysis treatment.

Optionally, in step S2, Li in the lithium-rich brine⁺The content of the Mg is 4800-16370 ppm²⁺The content is 20-200 ppm, and the total content of magnetic element ions is below 14 ppm;in step S3, performing the ion exchange treatment with an ion exchange resin, wherein the ion exchange resin is a cationic ion exchange resin;

in step S3, the chemical precipitation process includes: mixing an alkaline reagent with the lithium-rich brine, and removing precipitates to obtain the refined lithium-rich solution; the alkaline reagent is sodium carbonate, ammonium carbonate, potassium carbonate, sodium hydroxide or potassium hydroxide;

in step S4, the conditions of the bipolar membrane electrodialysis treatment include: the voltage of the single pair of membranes is 0.5-3V, and the current density of the membrane is 100-1000A/m²The operation temperature is 10-40 ℃.

Optionally, the method further comprises the steps of washing and drying after collecting the crystallized precipitate.

A third aspect of the disclosure: lithium hydroxide monohydrate prepared by the method of the second aspect of the present disclosure is provided.

A fourth aspect of the present disclosure: the application of the lithium hydroxide monohydrate described in the first aspect or the third aspect of the disclosure in preparing a lithium ion battery cathode material is provided.

The fifth aspect of the present disclosure: there is provided a lithium ion battery cathode material comprising the lithium hydroxide monohydrate according to the first or third aspect of the present disclosure.

A sixth aspect of the present disclosure: there is provided a lithium ion battery comprising the lithium ion battery cathode material according to the fifth aspect of the present disclosure.

According to the technical scheme, firstly, the lithium adsorbent is adopted to carry out preliminary lithium extraction and impurity removal on the lithium-containing brine, and then the separation, concentration and deep impurity removal are further carried out through the treatment processes such as membrane separation and the like, so that divalent and multivalent ions including magnetic elements in the lithium-containing brine can be removed, and high-purity lithium hydroxide monohydrate is obtained; and the acidity adjusting procedure in the prior art is not needed in the treatment process, so that the method is more environment-friendly. The lithium hydroxide monohydrate disclosed by the invention is nanoscale, and is beneficial to being uniformly mixed with a ternary precursor when being used for preparing a lithium ion battery cathode material, so that the low residual lithium amount on the surface of the ternary cathode material is realized; in addition, the lithium hydroxide monohydrate of the present disclosure has a lower content of magnetic elements, which can improve the service life of the lithium ion battery and reduce its self-discharge effect.

Additional features and advantages of the disclosure will be set forth in the detailed description which follows.

Drawings

The accompanying drawings, which are included to provide a further understanding of the disclosure and are incorporated in and constitute a part of this specification, illustrate embodiments of the disclosure and together with the description serve to explain the disclosure without limiting the disclosure. In the drawings:

FIG. 1 is a scanning electron micrograph of lithium hydroxide monohydrate of example 1 of the present disclosure at 50000 Xmagnification;

FIG. 2 is a scanning electron micrograph of lithium hydroxide monohydrate of example 1 of the present disclosure at a magnification of 20000 times;

FIG. 3 is a scanning electron micrograph of lithium hydroxide monohydrate of example 1 of the present disclosure at 10000 times magnification;

figure 4 is an XRD spectrum of lithium hydroxide monohydrate of example 1 of the present disclosure;

Detailed Description

The following detailed description of specific embodiments of the present disclosure is provided in connection with the accompanying drawings. It should be understood that the detailed description and specific examples, while indicating the present disclosure, are given by way of illustration and explanation only, not limitation.

The first aspect of the disclosure: provided is lithium hydroxide monohydrate having a particle size of 100 to 380nm, wherein the lithium hydroxide monohydrate has a Cu content of less than 1ppm, a Cr content of less than 1ppm, a Ni content of 2ppm or less, a Zn content of 2ppm or less, and an Fe content of 4ppm or less, by weight.

According to the present disclosure, the lithium hydroxide monohydrate is white powder in appearance, and primary particles of the lithium hydroxide monohydrate are nano-sized, so that the lithium hydroxide monohydrate is beneficial to being uniformly mixed with a ternary precursor when being used for preparing a lithium ion battery cathode material, and low residual lithium on the surface of the ternary cathode material is achieved.

The lithium hydroxide monohydrate disclosed by the invention is high in purity and low in magnetic element content, and when the lithium hydroxide monohydrate is used for preparing the lithium ion battery anode material, the service life of the lithium ion battery can be prolonged, and the self-discharge effect of the lithium ion battery can be reduced. Wherein the magnetic element may include Cu, Cr, Ni, Zn, or Fe, or a combination of two or three thereof. The purity of the lithium hydroxide monohydrate can be obtained by ICP-OES-plasma atomic emission spectrometry, and the purity of the lithium hydroxide monohydrate can be over 99.5%, and is preferably 99.53-99.89%.

In a second aspect of the present disclosure: there is provided a process for preparing lithium hydroxide monohydrate from a lithium-containing brine comprising the steps of:

s1, contacting lithium-containing brine with a lithium adsorbent for adsorption treatment, and contacting pure water with the adsorbed lithium adsorbent for leaching and washing to obtain a lithium-containing desorption solution;

s2, performing membrane separation treatment on the lithium-containing desorption solution to obtain lithium-rich brine; the membrane separation treatment comprises nanofiltration treatment, reverse osmosis treatment and electrodialysis treatment;

s3, carrying out chemical precipitation treatment or ion exchange treatment on the lithium-rich brine to obtain a refined lithium-rich solution;

s4, performing bipolar membrane electrodialysis treatment on the refined lithium-rich solution to obtain a crude lithium hydroxide aqueous solution;

and S5, evaporating and crystallizing the crude lithium hydroxide aqueous solution, and collecting crystal precipitates.

Firstly, carrying out preliminary lithium extraction and impurity removal on lithium-containing brine by using a lithium adsorbent, and further separating, concentrating and deeply removing impurities through treatment processes such as membrane separation and the like, so that various divalent and multivalent ions containing magnetic element ions in the lithium-containing brine can be removed, and high-purity lithium hydroxide monohydrate is obtained; and the acidity adjusting procedure in the prior art is not needed in the treatment process, so that the method is more environment-friendly.

According to the disclosure, the lithium-containing brine comprises salt lake brine and a self-prepared lithium-containing solution, and specifically, the salt lake brine can be one of salt lake old brine, potassium-removing old brine and tedded old brine. Wherein Li in the lithium-containing brine⁺The content can be 50-800ppm，Mg²⁺The content may be 60000 to 100000ppm, the ion content of the magnetic element may be 150 to 500ppm, and the magnetic element may include Cu, Cr, Ni, Zn, or Fe, or a combination of two or three thereof. Further, in the lithium-containing brine, Cu²⁺The content of Cr can be 10-50 ppm³⁺The content of Fe can be 15-45 ppm³⁺The content of Zn can be 100-350 ppm²⁺The content may be 20 to 150ppm, Ni²⁺The content may be 30 to 200 ppm.

According to the disclosure, in step S1, the lithium-containing brine is adsorbed by using a lithium adsorbent having preferential adsorption for lithium ions, and the lithium adsorbent hardly adsorbs or adsorbs divalent and polyvalent metal ions including magnetic element ions in a low amount, so as to achieve the purpose of extracting lithium and reducing the content of magnetic substances. The lithium adsorbent may be of a general kind capable of achieving the above-mentioned object, and may be, for example, an aluminum salt adsorbent, an ion sieve type oxide adsorbent, an amorphous hydroxide adsorbent, a manganese-based adsorbent or a titanium-based adsorbent. Preferably, the lithium adsorbent is an aluminum salt adsorbent or an ion sieve type oxide adsorbent, and the adsorption capacity of the adsorbent to lithium is higher. It is well known to those skilled in the art that when the adsorption treatment is performed using an ion sieve type adsorbent, a reducing agent (e.g., hydrazine hydrate) is added during the adsorption treatment to effect adsorption. The lithium adsorbent can be in the form of powder, and can also be mixed with a high molecular polymer to be made into various required shapes, such as cylindrical, long-strip, short rod or granular shapes, and the high molecular polymer can be polyethylene, polypropylene, polycarbonate, polyvinylidene fluoride, styrene, epoxy resin, polysulfone or poly sulfoxide, or a combination of two or three of the polyethylene, the polypropylene, the polycarbonate, the polyvinylidene fluoride, the styrene, the epoxy resin, the polysulfone or the poly sulfoxide. The amount of the lithium adsorbent can be adjusted according to the amount of the lithium-containing brine, for example, the amount of the lithium adsorbent is 30-180 g/L based on the volume of the lithium-containing brine. The adsorption mode can be a dynamic process of passing the lithium adsorbent through the column by using lithium-containing brine, or a static process of soaking the lithium adsorbent in the lithium-containing brine, the adsorption brine generated after adsorption treatment can be discharged back to a salt pan, and the elution treatment are carried out on the lithium adsorbent after adsorption treatment to complete desorption.

According to the disclosure, in step S1, the rinsing treatment refers to contacting the adsorbed lithium adsorbent with a proper amount of rinsing water (generally pure water), which may be a dynamic process of passing the lithium adsorbent through a column or a static process of soaking the lithium adsorbent in pure water. The amount of the rinsing water can be adjusted according to the amount of the lithium adsorbent, for example, the weight ratio of the rinsing water to the lithium adsorbent can be (0.6-3): 1. preferably, the leaching treatment is performed in a dynamic column passing mode, and the leaching speed is 6-12 BV/h, so that impurity ions such as magnesium ions on the lithium adsorbent can be efficiently eluted, and the use amount of leaching water can be reduced. The leacheate after the leaching treatment can be discharged back to the salt pan.

According to the disclosure, in step S1, the washover treatment refers to a step of contacting the washed lithium adsorbent with a proper amount of washover water (generally pure water), collecting the washover liquid, and repeatedly contacting the washover liquid with the lithium adsorbent, so that the finally obtained washover liquid is the lithium-containing desorption liquid. The amount of the washing water can be adjusted according to the amount of the lithium adsorbent, for example, the weight ratio of the washing water to the lithium adsorbent can be (2.5-8): 1. as is well known to those skilled in the art, when the adsorption treatment is performed by using an ion sieve type adsorbent, an oxidizing agent (e.g., hydrogen peroxide with a concentration of 0.2 to 10 wt%) is added during the washover treatment to achieve desorption.

In a preferred embodiment of the present disclosure, the washover treatment may include: contacting the leached lithium adsorbent with secondary washing liquid to perform first washing treatment, and separating the lithium adsorbent after the first washing treatment to obtain a lithium-containing desorption liquid; then contacting the lithium adsorbent subjected to the first set washing treatment with the primary set washing liquid to perform second set washing treatment, separating the lithium adsorbent subjected to the second set washing treatment after the second set washing treatment is completed to obtain the secondary set washing liquid, and performing the secondary set washingThe liquid is used for carrying out the first set washing treatment; and then contacting the lithium adsorbent subjected to the second elution with pure water to perform third elution, separating the lithium adsorbent subjected to the third elution after the third elution is completed to obtain the primary elution, wherein the first elution is used for the second elution. That is, the first washout liquid is a washout liquid obtained by washing the lithium adsorbent with a pure water jacket (i.e., a first washout), and the Li in the washout liquid is⁺The content is relatively low; the secondary washing liquid is obtained by washing the lithium adsorbent with pure water and washing the lithium adsorbent with the primary washing liquid (namely, two times of washing), and the Li in the washing liquid⁺The content is relatively high; thus, the leached lithium adsorbent is first contacted with the second elution reagent to perform the first elution treatment, and the obtained elution reagent (actually, the third elution reagent) contains Li⁺The content is higher, and the subsequent operation of taking the lithium-containing desorption solution as the lithium-containing desorption solution is more beneficial to improving the purity of the product lithium hydroxide monohydrate; meanwhile, the leached lithium adsorbent is sequentially subjected to three-time washing treatment, wherein Li⁺Extracted to the maximum extent, and the Li in the obtained lithium-containing desorption liquid⁺The content is high, the content of divalent and polyvalent ions including magnetic element ions is reduced, and the amount of pure water consumed by the double washing is small.

According to the disclosure, in step S1, after the lithium-containing brine is subjected to lithium adsorbent adsorption treatment, and then pure water rinsing treatment and elution treatment are performed on the adsorbed lithium adsorbent, the contents of magnesium ions and magnetic element ions in the obtained lithium-containing desorption solution can be greatly reduced. Specifically, Li in the lithium-containing desorption solution⁺The content may be 100 to 800ppm, Mg²⁺The content may be 500 to 5000ppm, and the total content of the magnetic element ions may be less than 23 ppm. Further, in the lithium-containing desorption solution, Cu²⁺The content may be less than 1ppm, Cr³⁺The content may be less than 1ppm, Fe³⁺The content may be 10ppm or less, Zn²⁺The content may be 6ppm or less, Ni²⁺The content may be 5ppm or less.

According to the present disclosure, in step S2, the purpose of the membrane separation process is to realize the concentration of lithium ions and the further separation and impurity removal of various divalent and polyvalent metal ions including magnetic element ions. The membrane separation treatment may include various treatment processes for selectively separating the mixture using a filtration membrane to achieve the above object, and in the present disclosure, the membrane separation treatment may include a nanofiltration treatment, a reverse osmosis treatment, and an electrodialysis treatment.

The nanofiltration is performed to separate monovalent lithium ions from divalent and polyvalent metal ions including magnetic element ions, and may be performed by a method conventional in the art, for example, a nanofiltration membrane. The nanofiltration membrane can be a polyamide nanofiltration membrane, a polyether sulfone nanofiltration membrane, an aromatic polyamide composite membrane or a mixed composite nanofiltration membrane, and the separation principle of the nanofiltration membrane mainly comprises a pore size screening effect and a southward effect. The aperture of the nanofiltration membrane can be about 1-2 nm, so that ions, molecules and colloidal substances with the aperture of more than 2nm can be removed through the aperture screening effect. Further, the nanofiltration membrane can be a charged membrane; the charged membrane is charged with negative electricity in an alkaline medium and charged with positive electricity in an acidic medium, can show different south-of-the-road effects on ions with different charges and different valence states, and further improves the rejection rate of the nanofiltration membrane on polyvalent anions and polyvalent cations, so that lithium ions and various divalent and polyvalent cations including magnetic element ions are fully separated, the content of magnetic substances in the final product lithium hydroxide monohydrate is reduced, and the purity of the product is improved.

The operating pressure of the nanofiltration treatment can be selected within the range of 0.2-4.0 MPa. The selection of the operation pressure is closely related to the components of the nanofiltration raw liquid, and when the concentration of divalent and multivalent cations including magnesium ions in the nanofiltration raw liquid is higher (such as 500-5000 ppm), the preferable operation pressure is 2.0-4.0 MPa; when the concentration of divalent and multivalent cations including magnesium ions in the nanofiltration raw liquid is low (such as 10-300 ppm), the preferable operation pressure is 0.2-2.0 MPa. The operating temperature of the nanofiltration treatment can be 10-40 ℃, and preferably 20-30 ℃. Under the preferred pressure and temperature regulation, the removal rate of divalent and multivalent cations including magnesium ions can be further increased. The nanofiltration treatment can be constant voltage operation or constant flow operation; the difference is that when the constant pressure operation is carried out, the water production flow is variable and is gradually reduced; while in constant flux operation, the operating pressure is variable and gradually increases. But no matter which operation mode, the factor of the concentration of the nanofiltration treatment process is not influenced. The concentrated water generated after nanofiltration treatment can be discharged back to the salt pan, and the generated fresh water enters the next membrane separation treatment process.

The reverse osmosis treatment is performed by using a reverse osmosis membrane, for example, to perform a reverse diffusion process of water molecules from a high concentration solution to a low concentration solution under the action of an external pressure. The reverse osmosis membrane can be a non-porous compact membrane, and can almost realize the interception of all ions, thereby realizing the function of concentrating lithium ions. Furthermore, the reverse osmosis membrane can be a cellulose acetate membrane, and the membrane has stable performance and strong pollution resistance. The operating pressure of the reverse osmosis concentration treatment can be flexibly adjusted according to the required concentration multiple, generally speaking, the larger the operating pressure is, the higher the concentration multiple is, the higher the lithium concentration is, and preferably, the operating pressure can be 2.0-4.0 MPa. The operating temperature can be 10-40 ℃. After the reverse osmosis treatment and concentration, the concentration of lithium chloride in the concentrated solution can reach 1.0-2.5 wt%. The fresh water produced after the reverse osmosis treatment can be reused as the rinsing water and the backwashing water for the rinsing treatment and the backwashing treatment in step S1.

The electrodialysis treatment is performed for the purpose of further increasing the lithium ion concentration, and the method for performing the electrodialysis treatment may be conventional in the art, and may be performed using, for example, an electrodialysis membrane. The electrodialysis membrane may be one of an alloy membrane, a homogeneous membrane, and a divalent ion separation membrane. The conditions of the electrodialysis treatment may include: the single pair of membrane voltage is 0.1-3V, preferably 0.2-2.5V; the operation temperature is 5-40 ℃, and preferably 20-30 ℃. The concentrated water after the electrodialysis treatment can enter the next membrane separation treatment process, and the produced fresh water can be used as reverse osmosis treatment feed liquid or nanofiltration treatment feed liquid for secondary concentration and separation.

The order and number of the nanofiltration treatment, the reverse osmosis treatment and the electrodialysis treatment are not particularly limited according to the present disclosure, and may be flexibly combined and adjusted according to the separation concentration, for example, in step S2, the membrane separation treatment may be one-stage nanofiltration treatment-reverse osmosis treatment-electrodialysis treatment-second nanofiltration treatment, reverse osmosis treatment-one-stage nanofiltration treatment-electrodialysis treatment-second nanofiltration treatment, one-stage nanofiltration treatment-reverse osmosis treatment-second nanofiltration treatment-electrodialysis treatment, or one-stage nanofiltration treatment-second nanofiltration treatment-reverse osmosis treatment-electrodialysis treatment.

In a preferred embodiment according to the present disclosure, in step S2, the membrane separation process comprises the following steps in sequence: primary nanofiltration treatment, reverse osmosis treatment, secondary nanofiltration treatment and electrodialysis treatment. By adopting the membrane separation treatment process of the preferred embodiment, the content of magnetic impurity ions can be reduced to the greatest extent, so that the content of magnetic elements in the lithium hydroxide monohydrate product finally prepared is extremely low, and the lithium hydroxide monohydrate product is very suitable for being used as a raw material for synthesizing a lithium ion battery cathode material.

According to the disclosure, in step S2, after the membrane separation treatment, the content of lithium ions in the obtained lithium-rich brine is greatly increased, and the content of magnesium ions and magnetic element ions is further decreased. In particular, Li in the lithium-rich brine⁺The content of Mg can be 4800-16370 ppm²⁺The content may be 20 to 200ppm, and the total content of the magnetic element ions may be 14ppm or less. Further, in the lithium-rich brine, Cu²⁺The content may be less than 1ppm, Cr³⁺The content may be less than 1ppm, Fe³⁺The content may be 5ppm or less, Zn²⁺The content may be 4ppm or less, Ni²⁺The content may be 3ppm or less.

According to the disclosure, in step S3, the lithium-rich brine is subjected to chemical precipitation treatment or ion exchange treatment, so as to achieve the purpose of deep impurity removal of the lithium-rich brine.

Among them, the method of performing the ion exchange treatment may be conventional in the art, and for example, the ion exchange treatment may be performed using an ion exchange resin. The ion exchange resin can be cationic ion exchange resin (such as strong acid cation resin and weak acid cation resin), preferably, the ion exchange resin is chelating resin, so as to sufficiently remove impurities such as divalent and polyvalent metal ions and obtain refined lithium-rich solution with higher purity. The amount of the ion exchange resin can be adjusted according to the amount of the lithium-rich brine and the content of impurity ions therein, and the adjustment method is well known to those skilled in the art.

Wherein the chemical precipitation treatment comprises: and mixing an alkaline reagent with the lithium-rich brine, and removing precipitates to obtain the refined lithium-rich solution. Thus, the alkaline ions in the alkaline reagent can be subjected to precipitation reaction with magnesium ions and/or calcium ions in the lithium-rich brine, so that the aim of removing the alkaline ions is fulfilled. The alkaline reagent can be sodium carbonate, ammonium carbonate, potassium carbonate, sodium hydroxide or potassium hydroxide; further, the alkaline agent may be in the form of an aqueous solution, for example, an aqueous solution of the above substance having a concentration of 0.5 to 6 mol/L. The amount of the alkaline reagent can be adjusted according to the amount of the lithium-rich brine and the content of magnesium ions and/or calcium ions in the lithium-rich brine, and the adjustment method is well known to those skilled in the art.

According to the present disclosure, in step S3, the content of impurities such as magnesium ions in the obtained refined lithium-rich solution is further reduced by the chemical precipitation treatment or the ion exchange treatment. Specifically, Li of the refined lithium-rich solution⁺The content of Mg can be 4800-16370 ppm²⁺The content may be 0 to 5ppm, and the total content of the magnetic element ions may be 10ppm or less. Further, in the refined lithium-rich brine, Cu²⁺The content may be less than 1ppm, Cr³⁺The content may be less than 1ppm, Fe³⁺The content may be 4ppm or less, Zn²⁺The content may be 2ppm or less, Ni²⁺The content may be 2ppm or less.

In step S4, the operation method of the bipolar membrane electrodialysis is well known to those skilled in the art, and the principle is that water molecules are electrolyzed on the membrane surface to generate hydrogen ionsAnd hydroxide ions which, due to the permselectivity of the positive and negative membranes, pass through the negative and positive membranes, respectively, to form a crude aqueous solution of lithium hydroxide and hydrochloric acid. The conditions of the bipolar membrane electrodialysis treatment may include: the voltage of the single pair of membranes is 0.5-3V, and the current density of the membranes is 100-1000A/m²The operation temperature is 10-40 ℃. The crude lithium hydroxide aqueous solution obtained after the bipolar membrane electrodialysis treatment also contains impurities such as sodium hydroxide, potassium hydroxide and the like.

According to the present disclosure, in step S5, since lithium hydroxide is low in solubility during the evaporation and crystallization process of the crude lithium hydroxide aqueous solution, it is precipitated first during the evaporation process, and thus the separation and purification can be achieved. The method of the present disclosure further comprises the steps of washing and drying after collecting the crystallized precipitate. And washing and drying the crystallized precipitate to obtain the lithium hydroxide monohydrate particles with low magnetic substance content and high purity.

A third aspect of the disclosure: lithium hydroxide monohydrate prepared by the method of the second aspect of the present disclosure is provided. The particle size of the lithium hydroxide monohydrate is 100-380 nm, and by weight, the content of Cu in the lithium hydroxide monohydrate particles can be less than 1ppm, the content of Cr can be less than 1ppm, the content of Ni can be less than 2ppm, the content of Zn can be less than 2ppm, and the content of Fe can be less than 4 ppm.

A fourth aspect of the present disclosure: the application of the lithium hydroxide monohydrate described in the first aspect or the third aspect of the disclosure in preparing a lithium ion battery cathode material is provided.

The fifth aspect of the present disclosure: there is provided a lithium ion battery cathode material comprising the lithium hydroxide monohydrate according to the first or third aspect of the present disclosure.

A sixth aspect of the present disclosure: there is provided a lithium ion battery comprising the lithium ion battery cathode material according to the fifth aspect of the present disclosure.

The present disclosure is further illustrated by the following examples, but is not to be construed as being limited thereby.