Analysis of the preparation process of battery grade lithium carbonate
Aug,06,24
Lithium carbonate is a fundamental raw material widely used in industries such as batteries, ceramics, glass, pharmaceuticals, refrigeration, and new energy storage.
It comes in two forms: amorphous white powder and prismatic colorless monoclinic crystals.
The national industry standard divides lithium carbonate into industrial grade lithium carbonate, battery grade lithium carbonate,
and high-purity lithium carbonate.
Battery grade lithium carbonate is a key raw material for producing positive electrode materials
and electrolyte additives for lithium-ion batteries such as LiCoO2, LiFePO4, LiMn2O4, etc.
At present, the main production methods for battery grade lithium carbonate include extracting lithium from salt lake brine, extracting lithium from lithium ore,
and extracting lithium from waste lithium batteries.
With the rapid increase in demand for lithium-ion batteries in industries such as electronics and new energy vehicles,
the demand for battery grade lithium carbonate is growing, and the quality requirements are also increasing.
Therefore, further research is needed on the preparation process technology of battery grade lithium carbonate.
1、 Process method for preparing battery grade lithium carbonate from salt lake brine
1.1 Process method for preparing crude lithium carbonate from salt lake brine
1.1.1 Carbonization and lithium extraction process method
The carbonization process for lithium extraction utilizes the reaction of carbon dioxide, lithium carbonate, and water to generate lithium bicarbonate,
which separates lithium from brine containing impurities such as magnesium.
Then, impurities and water are removed by vacuum suction to form lithium bicarbonate crystals, which are decomposed to obtain lithium carbonate.
The carbonization lithium extraction process has the advantages of requiring fewer raw materials, simple operation, short production cycle, and low process cost.
However, due to the general effectiveness of this method in removing impurities such as magnesium,
it is only suitable for lithium extraction from salt lake brines with low magnesium content.
Otherwise, magnesium reduction treatment must be carried out first, which limits its industrial application and requires further optimization research.
A method designed by Zhong Hui et al. for the preparation of lithium carbonate by carbonizing and separating magnesium
and lithium from high magnesium or lithium magnesium sulfate salt lake brines [4] has been optimized for the lithium extraction process by carbonization.
1.1.2 Precipitation lithium extraction process method
The precipitation lithium extraction process uses solar energy to heat the brine raw material and naturally evaporate and concentrate it.
When a certain concentration is reached, a precipitant is added to remove impurities such as magnesium and calcium from the brine.
Then, the precipitate is filtered and sodium carbonate is added to precipitate and obtain lithium carbonate.
According to different precipitants, the lithium extraction process can be divided into carbonate precipitation extraction,
aluminate precipitation extraction, boron magnesium and boron lithium co precipitation extraction, etc.
Among them, the carbonate precipitation lithium process has been widely used in industrial production.
The precipitation method for lithium extraction mainly uses solar energy as brine evaporation energy to concentrate lithium salt brine solution,
which relatively reduces production energy consumption and has a simple process and low production cost.
1.1.3 Extraction and lithium extraction process method
The extraction and lithium extraction process involves heating, evaporating,
and concentrating salt lake brine raw materials to precipitate some soluble sodium chloride, sulfate, and potassium salts.
Then, impurities such as boron and magnesium are removed, and ferric chloride solution is added as an extractant to obtain LiFeC14 · 2TBP extract.
The extract is acid washed and then back extracted with hydrochloric acid. Finally, the extract is evaporated, roasted, and dried to obtain lithium carbonate [5].
The use of extraction method for lithium extraction results in less loss of raw materials, but the process is relatively complex and has a certain degree of corrosion.
1.2 Process method for directly preparing battery grade lithium carbonate from salt lake brine
1.2.1 Ion exchange adsorption process method
The process of preparing battery grade lithium carbonate by ion exchange adsorption is to extract potassium from salt lake brine,
evaporate and concentrate to reduce the sodium and potassium content,
then add industrial hydrochloric acid acidification to prepare new brine,
and then add a mixture of sodium hydroxide and sodium carbonate to the new brine to prepare a lithium rich solution.
Next, the lithium rich solution is subjected to ion dialysis to reduce the magnesium impurity content, and lithium is extracted using manganese based adsorbents.
Then, it is desorbed using acid solution, filtered and concentrated to achieve a lithium content of over 30 g/L.
Industrial sodium carbonate is added to the solution, filtered to remove sodium chloride, and washed and dried again to prepare battery grade lithium carbonate.
The use of ion exchange adsorption technology to directly prepare battery grade lithium carbonate from salt lake brine can effectively control the impurity content and recover
the adsorbed and separated magnesium to form by-products.
A method designed by Wang Min et al. for extracting lithium from brine using ion exchange to prepare battery grade lithium carbonate was studied for the ion exchange adsorption process [6].
1.2.2 Electrodialysis process method
The process of preparing battery grade lithium carbonate by electrodialysis is to extract potassium from salt lake brine,
naturally evaporate it to form boron lithium new brine, filter and acidify it with industrial hydrochloric acid to obtain solid boric acid and acidified lithium brine.
The electrodialysis process is used to prepare lithium ion concentrated refined solution, and lithium hydroxide is added to remove impurities such as magnesium.
Subsequently, a low magnesium lithium solution was obtained by adding hydrochloric acid and adjusting the pH value.
Impurities such as sulfate ions, magnesium, and boron were removed by electroosmotic adsorption to obtain a lithium concentrate with calcium
and magnesium ions below 20 mg/L and lithium ion concentration above 30 g/L.
Industrial sodium carbonate was then added to the lithium concentrate for two-stage filtration precipitation,
followed by cleaning and drying to prepare battery grade lithium carbonate.
The process of directly preparing battery grade lithium carbonate from salt lake brine using electrodialysis technology is relatively complex,
but it can obtain high-purity battery grade lithium carbonate.
Ma Peihua et al. designed an electrodialysis method for directly preparing battery grade lithium carbonate from salt lake brine, and studied the electrodialysis process method [7].
2、 Process method for extracting lithium from lithium ore to prepare battery grade lithium carbonate
2.1 Sulfuric acid lithium extraction process method
The process of lithium extraction by sulfuric acid method involves roasting and ball milling lithium ore at high temperature,
and then adding excess concentrated sulfuric acid in an acidification kiln for acidification treatment to obtain lithium sulfate solution.
The solution is then transferred to a leaching tank where calcium carbonate slurry is added to remove lithium slag
and sodium carbonate is added to remove calcium and magnesium impurities;
Add sodium hydroxide to remove magnesium impurities through a causticization reaction to obtain a mixed solution of lithium carbonate and sodium sulfate,
and remove sodium sulfate through freezing treatment;
Further dense separation and centrifugal separation are carried out,
and carbon dioxide is introduced into the carbonization tank for carbonization precipitation and decomposition.
After thermal precipitation and drying, battery grade lithium carbonate is obtained [8].
The sulfuric acid lithium extraction process is a widely used lithium extraction process in the domestic industrial sector.
Its process is simple, controllable, with high yield and stable and reliable product quality.
2.2 Chlorination roasting process for lithium extraction
The process of chloride roasting for lithium extraction is to grind lithium ore and place it in a high-temperature furnace.
Chlorine gas is added while high-temperature roasting is carried out to generate chloride.
The chloride is separated and solidified by air cooling to obtain lithium chloride.
After water leaching, sodium hydroxide is added to precipitate and remove aluminum and magnesium impurities.
Electroosmotic concentration is used to obtain concentrated lithium rich solution.
Subsequently, sodium carbonate solution was added to the lithium rich solution, and wet lithium carbonate was obtained by settling and centrifuging.
The lithium carbonate was then prepared by circulating and aging the lithium settling mother liquor to obtain battery grade lithium carbonate.
The process of chloride roasting for lithium extraction has relatively low energy consumption, short production cycle, and high lithium yield.
A battery grade lithium carbonate preparation method based on lithium mica designed by Hu Wei et al. was studied for the chlorination roasting process.
3、 Process method for preparing battery grade lithium carbonate from industrial grade lithium carbonate
3.1 Hydrogenation process method
There are two process methods for preparing battery grade lithium carbonate through hydrogenation purification:
hydrogenation precipitation and hydrogenation decomposition.
The hydrogenation precipitation process involves mixing industrial grade lithium carbonate with deionized water,
introducing high-purity carbon dioxide gas into the mixed aqueous solution,
stirring at a certain temperature for a certain period of time, removing calcium and magnesium impurities to obtain high-purity lithium bicarbonate solution,
and then adding high-purity lithium hydroxide for reaction and precipitation to obtain battery grade lithium carbonate.
The chemical reaction formula is: Li2CO3+CO2+H2O → LiHCO3 (1) LiHCO3+LiOH → Li2CO3 (s)+H2O (2).
The difference between the hydrogenation decomposition process and the hydrogenation precipitation is that after producing high-purity lithium bicarbonate,
the lithium bicarbonate is heated and decomposed to obtain battery grade lithium carbonate. The chemical reaction formula [10] is: 2LihCO3 → Li2CO3+CO2+H2O (3)
3.2 Precipitation process method
There are two process methods for preparing battery grade lithium carbonate through precipitation purification:
ammonium bicarbonate precipitation and carbon dioxide precipitation.
The precipitation process of ammonium bicarbonate involves adding lime milk to industrial grade lithium carbonate to prepare lithium hydroxide solution,
and then adding high-purity ammonium bicarbonate to prepare battery grade lithium carbonate.
The chemical reaction formula is: 2LiOH+NH4HCO3 → Li2CO3+NH3+2H2O (4).
The carbon dioxide precipitation process involves adding high-purity carbon dioxide to the obtained lithium hydroxide solution,
followed by precipitation reaction to obtain battery grade lithium carbonate.
The chemical reaction formula is: 2LiOH+CO2 → Li2CO3+H2O (5)
3.3 Recrystallization process method
The process method for preparing battery grade lithium carbonate by recrystallization purification is to utilize the characteristic that
the solubility of lithium carbonate decreases with increasing temperature in water.
Ionic water is added to industrial grade lithium carbonate and then heated. At this point, lithium carbonate crystallizes, and other impurities dissolve into the ionized water.
The impurities are then removed by vacuum filtration to prepare battery grade lithium carbonate.
3.4 Electrolytic process method
The process method for preparing battery grade lithium carbonate by electrolytic purification is to react industrial grade lithium carbonate with sulfuric acid
or carbon dioxide to produce lithium sulfate or lithium bicarbonate,
and then perform electrolytic treatment in an ion exchanger. Lithium sulfate serves as the anode, and high-purity lithium hydroxide is obtained by cathodic electrolysis.
Then, high-purity carbon dioxide is used for carbonization reaction to produce lithium carbonate,
and impurities are separated and removed to prepare battery grade lithium carbonate.
When preparing battery grade lithium carbonate using the electrolysis process, an electrolysis reaction occurs between the positive and negative electrodes.
Therefore, it is necessary to control the electrolyte of the positive and negative electrodes,
otherwise excess impurities will be formed by the generation of sulfate ions at the cathode.
At the same time, further research is needed to solve the problem of sulfuric acid corrosion at the anode.
3.5 Caustic process method
The process method for preparing battery grade lithium carbonate by causticization purification is to add ionized water
and calcium oxide to industrial grade lithium carbonate to prepare a lithium hydroxide solution.
The calcium and magnesium impurities in the solution are respectively converted into insoluble calcium sulfate and magnesium hydroxide.
After precipitation, the calcium and magnesium impurities are filtered and removed to obtain high-purity lithium hydroxide.
Then, high-purity carbon dioxide gas is introduced to prepare battery grade lithium carbonate.
The process of caustic purification can be operated cyclically, resulting in a higher yield of lithium and cleaner removal of impurities such as calcium and magnesium.
However, it requires higher purity of calcium oxide and caustic temperature.
Xue Fengfeng et al. [11] studied the effect of calcium oxide dosage on the causticization reaction,
and found that excessive calcium oxide dosage would increase the calcium content, but had little effect on the lithium yield.
4、 Purification and preparation process of battery grade carbonic acid from waste lithium batteries
4.1 Recycling and lithium extraction process for waste lithium batteries
4.1.1 Chemical lithium extraction process method
The electrochemical extraction process is a process in which waste lithium batteries
such as lithium iron phosphate are placed in an electrolytic cell formed by an inorganic water-soluble salt solution or organic electrolyte,
and then a certain voltage is applied. Under the action of external charges,
lithium in the positive electrode material of the lithium battery migrates to the electrolytic cell solution in the form of lithium ions to extract lithium elements.
Some scholars have used electrochemical experiments to achieve a lithium migration rate exceeding 90%.
Experiments have shown that the electrochemical extraction process does not use acids, bases, etc.,
and only consumes a certain amount of electricity, thus having advantages such as low pollution emissions and green environmental protection.
However, this process method generates certain energy consumption when processing waste batteries into electrode materials,
and also has disadvantages such as low production efficiency and the need to consume expensive cation exchange consumables [12].
4.1.2 Dry metallurgical lithium extraction process method
The dry metallurgical lithium extraction process, also known as pyrometallurgical lithium extraction,
involves placing waste lithium batteries in a high-temperature incinerator
and removing the binder of the electrode material in the lithium battery through high-temperature combustion.
At the same time, the metal and its compounds in the battery undergo oxidation-reduction reactions to form slag,
which is cooled and solidified to form low boiling point slag containing lithium.
After screening, pyrolysis, magnetic separation or chemical treatment of the slag, the lithium metal element is extracted from it.
The dry metallurgy process for lithium extraction is simple and easy to operate, suitable for the recycling of most waste lithium batteries.
However, it is prone to producing exhaust gas during high-temperature incineration, which can cause certain pollution to the environment.
Therefore, it is necessary to carry out exhaust gas purification treatment to prevent secondary pollution [13].
4.1.3 Acid soaked metallurgical lithium extraction process method
The acid wet metallurgical lithium extraction process uses chemical solvents to dissolve waste lithium battery cathode materials,
forming a lithium containing chemical solution,
and then separating, leaching, and extracting lithium metal elements from the lithium containing chemical solution.
The main chemical solvents currently used are maleic acid, hydrochloric acid, malic acid, and iminodiacetic acid.
Ammonium carbonate, ammonium sulfite, ammonia mixtures, and sodium carbonate mixed with ultrasonic waves can also be used for lithium extraction.
Acid wet metallurgical lithium extraction is a mature process suitable for industrial scale production.
This process is sometimes used in conjunction with dry metallurgical lithium extraction to improve production efficiency and lithium yield.
4.1.4 Biometabolic lithium extraction process method
The biological metabolic lithium extraction process utilizes microorganisms to carry out metabolic reactions on metal elements such as lithium and cobalt in waste lithium batteries,
resulting in lithium containing metabolites, which are then leached out.
The use of biological metabolic lithium extraction process requires the cultivation of metabolic microorganisms.
Currently, the cultivated metabolic microorganisms mainly include iron oxidizing bacteria, sulfur oxidizing bacteria,
sulfur+acidophilic sulfur oxidizing bacteria, pyrite+iron loving leptospira, etc.
The biological metabolism lithium extraction process is a new type of lithium extraction process that does not require high-temperature calcination or chemical reactions,
thus reducing environmental pollution.
However, this process technology is not yet mature and stable, and further optimization research is needed [14].
4.1.5 Process method for lithium extraction by crushing suspension separation
The process of crushing suspension separation for lithium extraction is to first crush the lithium battery,
sort out the lithium containing electrode material, and then perform high-temperature heating treatment to remove the binder,
conductive agent, solvent and other substances on the electrode material.
The electrode materials such as lithium iron phosphate, lithium cobalt oxide, lithium manganese oxide or graphite are sorted out,
and then the physical and chemical properties of these materials with different surface hydrophilicity are used to suspend and extract lithium compounds by adding water.
4.2 Purification and preparation process of battery grade lithium carbonate from waste lithium batteries
The positive electrode materials of waste lithium batteries are mainly lithium iron phosphate, lithium cobalt oxide, etc.
To prepare battery grade lithium carbonate: first, completely discharge the waste lithium battery;
Secondly, the lithium iron phosphate positive electrode chip is peeled off as the raw material,
and the lithium ion solution is obtained by leaching using hydrochloric acid+hydrogen peroxide system or nitric acid+hydrogen peroxide system;
Add saturated sodium carbonate to the lithium-ion solution again to generate lithium carbonate,
which contains more impurities;
Finally, after transformation treatment with calcium chloride,
2-ethylhexyl phosphate is used as an extractant to remove impurities such as iron and phosphorus, resulting in a high-purity lithium solution.
Then, lithium carbonate or soda ash is used for lithium precipitation treatment, and after multiple cycles of purification, battery grade lithium carbonate is obtained.
When purifying lithium carbonate, it is necessary to control the following process parameters [16]:
firstly, leaching agents, which have different recovery effects and should be selected reasonably;
The second is the leaching time.
Within a certain period of time, the leaching amount of lithium increases with the extension of leaching time,
but after a certain period of time, the leaching amount of lithium will decrease;
The third is the leaching temperature.
Under a certain temperature limit, the leaching amount of lithium increases with the increase of temperature,
but beyond a certain temperature limit, the leaching amount of lithium begins to decrease;
The fourth is the liquid-solid ratio. Under larger liquid-solid ratios, the leaching amount of lithium increases significantly,
but as the liquid-solid ratio decreases, the leaching amount of lithium also gradually decreases.
Therefore, it is necessary to maintain the liquid-solid ratio within a certain range.
5、 Conclusion
Battery grade lithium carbonate can be prepared by extracting lithium from salt lake brine, lithium ore, waste lithium batteries, and other sources.
The carbonization and precipitation lithium extraction process of salt lake brine is relatively simple and cost-effective, and has been widely used in industrial production.
Through processes such as ion exchange adsorption and electrodialysis, battery grade lithium carbonate with standard purity can be produced through cyclic treatment.
The process of preparing battery grade lithium carbonate by sulfuric acid leaching and chloride roasting purification of lithium ore is relatively mature,
but there is still further research value in terms of production cost and lithium yield.
Industrial grade lithium carbonate can be purified by processes such as hydrogenation, precipitation, recrystallization, electrolysis, and causticization to prepare battery grade lithium carbonate.
The electrolysis process requires the use of acidic electrolytes and the need to address corrosion issues.
The recycling and extraction of lithium from waste lithium batteries is a sustainable development project that promotes resource regeneration and environmental protection.
It has good social and economic benefits. In the process of purifying and preparing battery grade lithium carbonate from waste lithium batteries,
it is necessary to control the process parameters such as leaching agent, leaching time, leaching temperature, and liquid-solid ratio.
