81 results about "Lithium hydroxide monohydrate" patented technology

The invention provides a preparation method and application of lithium sulfide. The preparation method comprises the following steps: reacting a lithium source with a sulfur source; the lithium source is a solid lithium-containing substance with the purity of 99% or above and the whiteness of 86 or above; the solid lithium-containing substance is selected from one or more of anhydrous lithium hydroxide, lithium hydroxide monohydrate, lithium carbonate, lithium chloride, lithium bromide and lithium nitrate. According to the method, a solid lithium-containing substance with the purity of 99% or above and the whiteness of 86 or above is used as a lithium source and reacts with a sulfur source, and the ionic conductivity value of the Li6PS5Cl solid electrolyte prepared from the obtained lithium sulfide is stable. Experimental results show that the ionic conductivity can stably reach more than 2mS / cm.

The invention discloses a preparation method of battery-grade lithium hydroxide monohydrate, which comprises the following steps: causticizing a lithium sulfate concentrated solution, freezing and crystallizing to obtain a frozen solution, precisely filtering the frozen solution, filtering by adopting an alkali-resistant nanofiltration membrane, collecting a penetrating fluid, and when the permeability of the alkali-resistant nanofiltration membrane is reduced, filtering by adopting an alkali-resistant nanofiltration membrane to obtain the battery-grade lithium hydroxide monohydrate. The alkali-resistant nanofiltration membrane is cleaned by lithium bicarbonate thermal decomposition mother liquor of a lithium carbonate production line, and all collected penetrating fluid is subjected to evaporative crystallization and centrifugal drying to obtain the battery-grade lithium hydroxide monohydrate. By adopting a method of nanofiltration membrane impurity removal and primary evaporative crystallization, the nanofiltration membrane impurity removal is used for replacing the primary evaporative crystallization in the prior art, so that the energy consumption can be effectively reduced, the production cost is saved, the Si content of the nanofiltration solution is lower than 3ppm and lower than that of the primary evaporative crystallization heavy solution, and the method can be used for preparing high-quality battery-grade lithium carbonate. The Si content of the prepared lithium carbonate is lower than 20 ppm.

This invention provides a method for preparing a positive electrode lithium supplement, comprising the following steps: Step S1: Mixing and grinding lithium nitrate and lithium hydroxide monohydrate; Step S2: Melting the material after mixing and grinding in Step S1 to obtain a mixed lithium salt of lithium nitrate and lithium hydroxide; Step S3: Mixing the mixed lithium salt with an iron source and glucose, and then pressing it into tablets; Step S4: Calcining the material after tableting in Step S3 under inert gas protection; Step S5: Cooling and sieving the calcined material after Step S4 to obtain the positive electrode lithium supplement Li5FeO4. The method of this invention for preparing Li5FeO4 has excellent properties such as small particle size, low energy consumption, short sintering time, low cost, and low calcination temperature.

A process for producing lithium hydroxide monohydrate from lithium chloride, the process comprising: (a) adding an aqueous potassium ion and hydroxide ion-containing solution to an aqueous lithium chloride-containing solution, thereby obtaining a mixture comprising lithium hydroxide, potassium chloride and water, (b) selectively precipitating potassium chloride from the mixture, thereby obtaining potassium chloride precipitate and a first mother liquor solution, (c) separating the potassium chloride precipitate from the first mother liquor solution, (d) processing the potassium chloride precipitate to obtain an aqueous potassium hydroxide-containing solution, (e) adding the aqueous potassium hydroxide-containing solution to the separated first mother liquor solution, thereby obtaining a potassium hydroxide-enriched first mother liquor solution, and (f) selectively precipitating lithium hydroxide monohydrate from the potassium hydroxide-enriched first mother liquor solution, thereby obtaining lithium hydroxide monohydrate precipitate and a second mother liquor solution.

The invention discloses a lithium lanthanum zirconium tantalum oxide solid electrolyte with a lithium tantalate composite garnet structure and a preparation method of the lithium lanthanum zirconium tantalum oxide solid electrolyte, and belongs to the technical field of all-solid-state lithium ion batteries. The preparation method comprises the following steps: heating lanthanum oxide, ball-milling and uniformly mixing the lanthanum oxide, lithium hydroxide monohydrate, zirconium oxide and tantalum oxide in isopropanol, and pre-sintering to obtain a precursor; and performing secondary ball milling on LiTaO3 accounting for 1-10% of the mass of the precursor and the precursor, uniformly mixing, drying, tabletting, and sintering at high temperature to obtain the solid electrolyte material. The ionic conductor LiTaO3 is introduced into the grain boundary of the lithium lanthanum zirconium tantalum oxide solid electrolyte, the porosity is reduced, the grain boundary bonding strength is enhanced, the resistance and activation energy of the electrolyte are reduced in the sintering process, lithium tantalate does not react with the garnet structure solid electrolyte, impurities hindering ion transmission are not generated, the ionic conductivity at the room temperature is improved, and the service life of the lithium lanthanum zirconium tantalum oxide solid electrolyte is prolonged. The migration activation potential barrier of lithium ions is reduced, and the problem of low total ionic conductivity caused by the grain boundary problem is effectively solved.

This invention belongs to the field of battery materials technology, specifically relating to a one-step continuous dehydration and sulfidation method for preparing lithium sulfide from lithium hydroxide monohydrate. This invention uses LiOH·H₂O as the lithium source for preparing lithium sulfide, significantly reducing costs. The dehydration and sulfidation steps are completed continuously and uninterruptedly within the same reaction vessel, using the same batch of materials, through program control. There are no intermediate material transfer, separation, or intermediate processing steps, avoiding exposure to air for moisture absorption, oxidation, and the introduction of impurities, thus ensuring high product purity.

The invention relates to the technical field of lithium hydroxide extraction, and discloses a method for preparing battery-grade lithium hydroxide monohydrate by using salt lake brine. The method comprises the following steps: extracting lithium by adsorption, removing calcium and magnesium by a membrane separation method, performing electrodialysis concentration, deeply removing calcium and magnesium, removing boron by chelating resin, performing bipolar membrane dialysis, electrolyzing in an electrolytic tank, performing reduced pressure evaporation and drying. According to the method for preparing the battery-grade lithium hydroxide monohydrate by using the salt lake brine, the battery-grade lithium hydroxide monohydrate with relatively low Cl <-> content can be simply and conveniently prepared.

The invention belongs to the technical field of lithium salt preparation, and provides a method for preparing battery-grade lithium hydroxide monohydrate by causticizing lithium carbonate. According to the method, raw material washing and ion exchange purification are combined with a multi-stage crystallization impurity removal process including evaporation concentration, rotational flow classification and elutriation to achieve a synergistic effect, so that the impurity content of the product is effectively controlled, and a lithium carbonate component causing scaling is actively removed; therefore, the scaling problem of evaporative crystallization equipment is remarkably relieved while the product purity is improved, and the lithium hydroxide monohydrate meeting the battery-grade quality requirement is stably and continuously produced by taking the industrial-grade lithium carbonate as the raw material.

The invention discloses a method for producing battery-grade lithium hydroxide monohydrate by a suspension roasting method, which comprises the following steps: S1, preheating a raw material, transforming and roasting, cooling and discharging; s2, mixing the roasted material with sulfuric acid, acidifying and roasting; s3, water is added for size mixing, calcium carbonate powder is added for neutralization and leaching, and leaching clear liquid is obtained; s4, adding caustic soda liquid and sodium carbonate, and filtering to obtain purified clear liquid; s5, evaporating and concentrating the purified clear liquid, adding caustic soda liquid for reaction, and filtering to obtain conversion liquid; s6, freezing crystallization and centrifugal separation are performed to obtain frozen liquid and sodium sulfate decahydrate; s7, sodium sulfate decahydrate is subjected to redissolution, MVR sodium thermal precipitation, drying, cooling and packaging, and anhydrous sodium sulphate is obtained; s8, evaporating, concentrating and centrifugally separating the frozen solution to obtain a crude product mother solution and a crude product lithium hydroxide; s9, re-dissolving the crude product lithium hydroxide; s10, evaporating and concentrating the heavy solution, and separating to obtain a lithium hydroxide refined product; s11, drying, screening, crushing, batch mixing and demagnetizing are conducted, and a finished product is obtained. The production efficiency and the product quality are effectively improved through the method.

The invention discloses a method for reducing magnetic foreign matters by a tubular vibratory feeding conveyor for producing lithium hydroxide monohydrate, and aims to solve the problems of deliquescence dust pollution, material adhesion and blockage and the like caused by easy introduction of magnetic foreign matters, insufficient sealing and the like of existing lithium hydroxide monohydrate conveying equipment. By constructing a totally-closed conveying system of a de-ironing separator surge bin, an electromagnetic de-ironing separator, a tubular vibrating feeding conveyor and a small packing machine bin and combining with an ultra-high molecular weight polyethylene lining arranged in a key component, the problems of deliquescence, carbonization, pollution and the like of lithium hydroxide monohydrate are effectively solved, the harsh requirements of battery-grade (the purity is greater than or equal to 99.5%) products are met, and the product quality is improved. Meanwhile, magnetic foreign matter control and conveying stability are achieved.

The invention provides a lithium carbonate lithium supplement agent as well as a preparation method and application thereof, and relates to the technical field of secondary batteries. The preparation method of the lithium carbonate lithium supplementing agent comprises the following step: enabling ethyl carbamate and lithium hydroxide monohydrate to react in water to obtain the lithium carbonate lithium supplementing agent. The prepared lithium carbonate lithium supplement agent is lithium carbonate with a three-dimensional porous skeleton structure, and the lithium carbonate is lower in decomposition voltage compared with existing commercially-purchased lithium carbonate, and can be directly used as the lithium supplement agent in the preparation of a lithium ion battery without being compounded with other metals. The preparation method of the lithium carbonate lithium supplement agent is easy and convenient to operate, reaction products are convenient to post-treat, operability is high, a high-performance lithium supplement agent material can be efficiently obtained, and the preparation method is suitable for large-scale production of lithium ion batteries.

A method for producing battery-grade lithium hydroxide monohydrate with low carbonate content from impure lithium feedstock, the method comprising: forming a concentrated lithium hydroxide solution saturated or nearly saturated with lithium hydroxide monohydrate; removing at least some lithium carbonate from the solution; crystallizing the lithium hydroxide monohydrate; and separating the crystallized lithium hydroxide monohydrate from the solution.

The present invention relates to the recovery of lithium from solid resources with minimized energy consumption, for example for commercial products such as lithium hydroxide monohydrate, lithium carbonate or low sodium lithium carbonate.

The invention discloses a lithium iron phosphate battery preparation method, which comprises: 1, mixing lithium hydroxide monohydrate, iron phosphate and glucose, carrying out manual wet grinding by using an agate mortar, and drying after the grinding is completed to obtain mixed powder; step 2, putting the mixed powder into a tubular furnace, heating in an argon atmosphere for high-temperature solid-phase synthesis to obtain lithium iron phosphate, and then grinding and sieving to obtain lithium iron phosphate powder; and step 3, stirring and mixing the lithium iron phosphate powder, a conductive agent, a binder and N-methyl pyrrolidone, then coating an aluminum foil with the mixture, drying and cutting to obtain a positive plate, and then assembling the positive plate into the battery in a glove box. The material synthesized by the invention has the advantages of high specific discharge capacity, small charge transfer resistance, strong lithium ion transmission capability, better reaction kinetics and chemical reversibility of an electrode, maximum peak current and large capacitance.

A process for producing high purity lithium hydroxide monohydrate from a material containing a lithium salt selected from Li2SO4, LiCl, Li2CO3 or mixtures thereof, comprising membrane electrolysis of an aqueous solution of said lithium salt using a cation exchange membrane and nickel-plated stainless steel. The catholyte is drawn from the circulation stream and evaporated to obtain lithium hydroxide monohydrate crystals which are separated from the mother liquor, washed with water and dried to obtain the final high purity lithium hydroxide monohydrate. Part of the used wash liquor is fed to the catholyte evaporation process. Part of the mother liquor formed after separation of the lithium hydroxide monohydrate crystals is returned to the catholyte evaporation process. The reverse flow of the anolyte is replenished with a concentrated lithium salt solution prepared from the original lithium salt. Part of the used catholyte drawn from the evaporation process is directed to Li2CO3 production.

The invention relates to the field of lithium hydroxide production, in particular to a method for improving the lithium yield in the process of producing lithium hydroxide through a sulfuric acid method. The method comprises the following steps: step 1, mixing crude lithium phosphate with an acid solution for reaction to obtain a re-dissolution material solution; 2, the re-dissolution feed liquid in the step 1 is subjected to precise filtration treatment, and filtrate is obtained; step 3, adding a calcium source into the filtrate obtained in the step 2, and removing phosphate radicals in the filtrate to obtain feed liquid containing precipitates; and 4, filtering the material liquid containing the precipitate in the step 3 to obtain filter residues and filtrate. And 5, merging the filtrate obtained in the step 4, and feeding the merged filtrate into a production system for producing lithium hydroxide monohydrate. The invention aims to primarily purify the crude lithium phosphate obtained by recovering the residual lithium resource from the production process and then return to the production system for continuously producing the lithium hydroxide, the whole process flow is short, the operation is simple and convenient, the effect of improving the lithium yield in the production process is obvious, and the industrial production can be quickly realized.

The invention relates to a preparation method of high-purity lithium carbonate, in particular to a method for preparing high-purity lithium carbonate in ethanol by taking a mixture of urea and carbon dioxide as a carbon source and lithium hydroxide or lithium hydroxide monohydrate as a lithium source, and belongs to the technical field of chemical synthesis. The method comprises the following steps: firstly, adding a proper amount of lithium hydroxide or lithium hydroxide monohydrate into a reaction kettle, then adding a certain amount of urea into the reaction kettle, then adding a proper amount of ethanol into the reaction kettle, and stirring the mixture to fully dissolve solids to obtain a lithium hydroxide solution with the mass percent concentration of 0.1-12%; and introducing carbon dioxide, stirring at the constant temperature of 100-130 DEG C for 2-8 hours, separating a solid phase and a liquid phase after the reaction is finished, and drying the separated solid to obtain high-purity lithium carbonate powder. Therefore, the method disclosed by the invention is safe and environment-friendly, is simple and convenient to operate, and can be used for efficiently preparing high-purity lithium carbonate at low cost.

The application discloses a preparation method of a lithium iron phosphate battery, and comprises the following steps: step one, mixing lithium hydroxide monohydrate, iron phosphate and glucose, and then manually wet grinding the mixture in a agate mortar, and drying the mixture after grinding to obtain a mixed powder; step two, placing the mixed powder into a tube furnace, and performing high-temperature solid-phase synthesis under an argon atmosphere to obtain lithium iron phosphate, and then grinding and sieving the lithium iron phosphate to obtain lithium iron phosphate powder; and step three, stirring and mixing the lithium iron phosphate powder, a conductive agent, a binder and N-methyl pyrrolidone, then coating the mixture on an aluminum foil, cutting the mixture after drying to obtain a positive electrode sheet, and then assembling the positive electrode sheet into a battery in a glove box. The material synthesized by the application has high specific discharge capacity, small charge transfer resistance, strong lithium ion transmission capacity, better reaction kinetics and chemical reversibility of the electrode, maximum peak current and large electric capacity.

The present invention relates to the field of chemical engineering, and more particularly to methods and devices for obtaining lithium hydroxide from brines by bipolar electrodialysis. The present method utilizes energy-efficient purification and electrochemical conversion techniques in the processing of mineral brines. The proposed method and plant for the implementation thereof make it possible to obtain high-purity lithium hydroxide monohydrate from natural calcium chloride-type brines, inter alia in the form of produced water that is a byproduct of the oil production process.

The present application relates to the technical field of high polymer antibacterial health protection materials, in particular to a preparation method of a universal copper-based nanometer material, wherein copper hydroxide precipitate is obtained by adding sodium hydroxide solution into copper chloride water solution step by step, and then copper oxide nanoparticles are obtained by drying and grinding; copper nitrate trihydrate, lithium hydroxide monohydrate and water are mixed and then hydrothermally dispersed to obtain copper hydroxide nanowires; copper chloride dihydrate, lithium hydroxide monohydrate and water are mixed to obtain copper oxide nanosheet; finally, copper oxide nanoparticles, copper hydroxide nanowires and copper oxide nanosheet are dispersed and mixed to obtain a copper-based nanometer compound. The present application is a new type of copper-based nanometer antibacterial material with regular prism / rod microstructure, high dispersibility, strong base material compatibility, high temperature resistance and excellent durability. The material can be truly embedded in different base materials instead of only staying on the surface, and can be universally applied in various material systems such as silica gel, latex and yarn.

A process for producing lithium iron phosphate, comprising the following steps: S1: Dispersing a lithium salt in a prepared solvent A and adjusting a pH of a resulting dispersion to 6.5-8.5 with an organic acid to obtain a mixed solution; and dispersing a porous iron phosphate in a prepared solvent B and adding an organic carbon source to obtain a mixed slurry A; wherein the prepared solvent A and the prepared solvent B are independently water or a dispersion of a volatile solvent and water; and the lithium salt is one or more selected from the group consisting of lithium oxide, lithium carbonate, lithium acetate, lithium hydroxide, lithium hydroxide monohydrate, and lithium nitrate; S2: Adding the mixed slurry A to the mixed solution, grinding the resulting slurry to obtain a ground material, adding a dispersant to the ground material, and stirring the dispersion to obtain a mixed slurry B; and S3: Aging and drying the mixed slurry B under a pressure of 100 Pa to 1,000 Pa to obtain a dry material, and sintering the dry material in an inert atmosphere to obtain the lithium iron phosphate.

An improved manufacturing process for lithium hydroxide monohydrate suitable for battery applications is provided. Preferably, potassium hydroxide (KOH) is added to an aqueous solution of lithium sulfate (Li₂SO₄), and the resulting aqueous solution is adjusted to a temperature in the range of 0 to 25°C. After quantitative removal of the K₂SO₄, LiOH can be crystallized in high yield and purity.

A process for producing lithium hydroxide monohydrate from lithium chloride, the process comprising: (a) adding an aqueous solution comprising sodium hydroxide to a first aqueous solution comprising lithium chloride, thereby obtaining a mixture comprising lithium hydroxide, sodium chloride and water; (b) cooling the mixture to selectively precipitate lithium hydroxide monohydrate; (c) separating the lithium hydroxide monohydrate precipitate from the first mother liquor; (d) adding a second aqueous solution containing lithium chloride into the separated first mother solution to obtain a first mother solution enriched with lithium chloride; and (e) removing (preferably evaporating) moisture from the lithium chloride enriched first mother liquor to selectively precipitate sodium chloride.

The invention provides a recovery method of a lithium ion battery positive electrode active material, which comprises the following steps: roasting the lithium ion battery positive electrode active material and an additive, performing water immersion, and treating the water immersion liquid by using a bipolar membrane system to obtain lithium hydroxide monohydrate solid powder; meanwhile, the water leaching residues are subjected to an acid leaching coprecipitation reaction to obtain a positive electrode active material precursor, and compared with a traditional mode that lithium-containing water leaching liquid is recycled in a lithium carbonate mode, lithium hydroxide prepared through the method is high in purity and can be directly used for preparing a high-nickel positive electrode active material. Besides, heavy metal ions such as nickel, cobalt and manganese are obtained through one-step coprecipitation in the form of precursors, the complex step of extracting each metal through multiple extraction agents in a traditional wet process is omitted, and the whole technological process is simplified and more environmentally friendly.

The application relates to the technical field of drug delivery, and particularly discloses a novel long-chain compound for small nucleic acid drug delivery and a synthesis method and application thereof. The synthesis method of the novel long-chain compound for small nucleic acid drug delivery comprises the following steps: reacting tris(hydroxymethyl)aminomethane and acrylonitrile, then reacting with sulfuric acid to obtain compound 3; first, reacting compound 3 and Boc anhydride, then reacting with lithium hydroxide monohydrate, then reacting with 2,3,5,6-tetrafluorophenol, and finally, reacting with tert-butyl (2-(2-(2-(2-aminoethoxy)ethoxy)ethoxy)ethyl)carbamate to obtain compound 7; and reacting compound 7 with (1R,8S,9s)-bicyclo[6.1.0]non-4-yn-9-ylmethyl succinimidyl carbonate to obtain a target product. The novel long-chain compound for small nucleic acid drug delivery can be flexibly connected with multiple drug molecules, targeting ligands or functional modules to optimize delivery efficiency, pharmacokinetics and targeting property, and enriches the selectivity of a small nucleic acid drug delivery system.

Provided are: a zigzag LiMnO2 type compound which can be produced on an industrial scale; and / or a method for producing same.　Provided is a method for producing a lithium composite oxide which is represented by the compositional formula LixMnO2 (0.80≤x≤1.20), which has a zigzag layer structure as a basic structure, and which has a domain having an α-NaFeO2 type layered structure. The method is characterized by having a step for heating a composition containing a manganese source that is dimanganese trioxide and / or manganese oxyhydroxide and one or more lithium sources selected from the group consisting of lithium carbonate, anhydrous lithium hydroxide and lithium hydroxide monohydrate in an inert gas atmosphere to an attainment temperature of 600-750ºC, and maintaining the attainment temperature for a period of 6 hours or less.

A process for producing high purity lithium hydroxide monohydrate from a material containing lithium salts selected from Li2SO4, LiCl, Li2CO3 or mixtures thereof, comprising membrane electrolysis of a specified aqueous lithium salt solution using a cation exchange membrane and a nickel-plated stainless steel cathode. Catholyte is withdrawn from the circulation stream, evaporated to obtain lithium hydroxide monohydrate crystals, which are separated from the mother liquor, washed with water and dried to obtain the final high purity lithium hydroxide monohydrate. A portion of the spent washing solution is fed to the catholyte evaporation process. A portion of the mother liquor formed after separation of the lithium hydroxide monohydrate crystals is returned to the catholyte evaporation process. The counterflowing anolyte is replenished with a concentrated lithium salt solution prepared from the original lithium salt. A portion of the spent catholyte withdrawn from the evaporation process is directed to the production of Li2CO3.

The invention relates to the field of lithium battery material preparation, and discloses a continuous industrial preparation method of battery-grade lithium dihydrogen phosphate, which comprises the following steps: carrying out continuous graded mixing reaction on a crude product lithium hydroxide monohydrate and phosphoric acid with specific mass concentration through a plurality of neutralization tanks to prepare a lithium dihydrogen phosphate solution with required pH and Li2O concentration; evaporating and concentrating the lithium dihydrogen phosphate solution, cooling and thickening, discharging, performing flash evaporation crystallization, and performing centrifugal separation to obtain a lithium dihydrogen phosphate wet product; drying the wet lithium dihydrogen phosphate product to obtain a battery-grade lithium dihydrogen phosphate product; the high-impurity lithium dihydrogen phosphate mother liquor obtained after multiple times of circulating evaporation reacts with the discharged crude lithium hydroxide evaporation mother liquor to generate lithium phosphate for recycling lithium resources, and lithium phosphate can be directly used as a raw material for synthesizing lithium dihydrogen phosphate. The method is a highly automatic and continuous industrial production method for producing the product, controls the quality of the crude product lithium hydroxide monohydrate raw material and co-treats the discharged mother liquor, improves the lithium yield, effectively utilizes redundant acid, alkali and phosphorus in the system, and reduces waste and environmental protection pressure.

The application discloses a motor lubricating grease composition, which comprises a thickening agent, base oil and an additive, and specifically, the thickening agent is 10-15%, the base oil is 85-90%, and the sum of the mass percentages of the two is 100%; the additive is additionally added in a proportion of 1-5%; the thickening agent is composed of mixture A and mixture B; a) the mixture A is a reactant of dodecahydroxy stearic acid, organic dibasic acid and saturated aqueous solution of lithium hydroxide monohydrate, and the molar ratio of the dodecahydroxy stearic acid to the organic dibasic acid is 1:0.1-1; b) the mixture B is an amide compound, and the amide compound is a mixture of one or more of dodecanamide, hexadecanamide, octadecanamide, octadecenoic acid amide, docosanamide, docosenoic acid amide, N,N-dimethyl dodecanamide and N,N'-ethylene bis-stearamide in an arbitrary ratio. The application can effectively prolong the service life of the lubricating grease, prolong the grease replenishing period and prolong the service life of the motor.

The invention discloses a battery-grade lithium hydroxide monohydrate production method based on combined efficient calcium removal, which comprises the following steps: carrying out roasting, ball milling, acidification, leaching and plate-frame pressure filtration on spodumene to obtain a lithium sulfate solution, and further alkalifying and removing impurities, namely adding liquid caustic soda and a Na2CO3 solution into the lithium sulfate solution subjected to pressure filtration to carry out purification and impurity removal; calcium hydroxide and calcium carbonate precipitates are formed; sequentially carrying out filtering separation, MVR concentration and secondary filtering separation to ensure that the calcium ion concentration of the concentrated lithium sulfate solution is controlled to be less than 20ppm; adding a sodium hydroxide solution into the clear liquid treated by the plate-and-frame filter press, and mixing to obtain a lithium hydroxide solution and a sodium sulfate solution; and carrying out plate-and-frame pressure filtration and fine filtration, freezing to separate out sodium, carrying out fine filtration, carrying out crude product MVR concentration, re-dissolving, and carrying out secondary plate-and-frame pressure filtration and fine filtration. The method has the advantages that calcium is deeply removed, the quality of the battery-grade lithium hydroxide product is guaranteed, the production efficiency is improved, the cost is reduced, the technological process is simplified, and high efficiency and environment friendliness are achieved.