THE PATENT ACT 1970
(39 of 1970)
&
The Patents Rules, 2003
COMPLETE SPECIFICATION
[See sections 10 and Rule 13]
1.TITLE
A Process to recover lithium as a lithium
carbonate from effluent/ processed solution of
lithium-ion batteries
2.APPLICANT(s)
Evergreen Recyclekaro (India) Private Limited
Gut No. 113/A, Shingadapada Aapti Road
VADA PALGHAR, PALI, Maharashtra, 421303
COMPLETE SPECIFICATION
TITLE OF THE PATENT
A Process to recover lithium as a lithium carbonate from effluent/ processed
solution of lithium-ion batteries
FIELD OF INVENTION
The present invention is in the field of Technology for recovery of lithium as a
lithium carbonate (Li2CO3) from effluent/ processed solution of lithium-ion
batteries using carbon dioxide gas as a precipitant. The effluent generated
after the extraction of cobalt, nickel and manganese were collected and
analyzed which contains 2-4 g/L lithium (Li). Thereafter, concentration of
lithium was increased up-to 15 g/L by evaporation to effectively precipitate
the lithium. Further, carbon dioxide gas was sparged into the lithium
enriched solution at following conditions (solution temperature: 90˚C, pH: 10-
12) to precipitate the lithium carbonate with precipitation efficiency close to
98.5%.
BACKGROUND OF THE INVENTION
Lithium carbonate (Li2CO3) is produced commercially from three Sources: (1)
extraction from mineral Sources Such as Spodumene; (2) lithium-containing
brines, or (3) from Sea Water.
There are a number of commercial applications of lithium carbonate
including: as an additive in aluminum molten Salt electrolysis and in enamels
and glasses. In its purer forms, (for example, having 99.1 wt % (Li2CO3) Li2CO3
is used to control manic depression, in the production of electronic grade
crystals of lithium niobate, tantalate and fluoride. High purity lithium
carbonate is also required in the emerging technologies of lithium batteries.
(There are two major classes of rechargeable lithium batteries, those using
lithium ion and thin film polymer electrolyte-lithium metal.)
In the case of the lithium ion battery, purified lithium carbonate is required
for the cathode. In the case of thin film batteries using polymer electrolytes,
lithium metal is obtained by chlorinating lithium carbonate to form lithium
chloride and Subsequent electrolysis to metallic lithium. The key to obtaining
lithium of the grade required for lithium batteries is to use purified lithium
chloride and carrying out electrolysis in the virtual absence of air and
humidity to minimize lithium's rapid reactions with these Substances.
Electrolytic production of lithium metal is practiced commercially using an
eutectic melt of LiCl and KCl (45 and 55 wt %, respectively) at 450° C. under
anhydrous conditions. During electrolysis, lithium metal produced typically
at a Steel cathode rises to the Surface of the melt due to its significantly lower
density (0.5 g/ml relative to 1.5 g/ml for the melt). At the anode, chlorine gas
is evolved. In Some cell designs, there is a diaphragm between the anode and
cathode to prevent or at least partially prevent recombination of chlorine and
lithium.
As the natural resources of lithium is almost negligible in Indian context and
we entirely depend on the foreign country to meet our demand and supply of
lithium. Thus, it needs to explore the alternative resources of lithium to fulfil
supply of lithium up-to certain extent by recycling the discarded batteries.
Therefore, the main objective of the present invention is to develop the
indigenous technology for recovery of analytical grade lithium carbonate from
effluent of discarded batteries, that can be re-used in the manufacturing of
lithium-ion batteries, nickel metal hydride batteries or any other energy
storage devices.
Amouzegar et al. (2000) reported the lithium carbonate precipitation from
spodumene (lithium minerals), brine and sea water using carbon dioxide as a
precipitant. But our invention focused on the precipitation of lithium
carbonate from effluent of spent lithium-ion batteries. The composition and
nature of effluent/processed solution of spent lithium-ion batteries is totally
different from the previous invention as reported by Amouzegar et al. 2000.
Sea water and brine contain high concentration of Ca, Mg and Boron; whereas
these elements are not present in the effluent of spent lithium-ion batteries.
Harris and White claims the precipitation of lithium carbonate from leach
liquor of spent lithium-ion batteries using a mixture of sodium carbonate
(Na2CO3) and sodium bicarbonate (NaHCO3). It requires several stages of water
washing to remove the impurities like sodium to get the pure lithium
carbonate. They (Harris et al. 2018) have not claim the purity of precipitated
lithium carbonate (Li2CO3). But we have claimed the precipitation of highly
pure lithium carbonate using carbon dioxide as a precipitant. The precipitated
lithium carbonate can be re-used in the manufacturing of cathodic material
of energy storage materials like lithium-ion batteries, nickel metal hydride
batteries, electric vehicle etc.
OBJECT OF INVENTION
It is the object of Invention to provide for a process for recovery of lithium as
a lithium carbonate (Li2CO3) from effluent/ processed solution of lithium-ion
batteries using carbon dioxide gas as a precipitant.
Yet another object of the Invention is to provide an analytical grade Lithium
carbonate with its purity close to 99.5%.
SUMMARY OF INVENTION
The present invention addresses these and other problems in the prior art by
providing, in one aspect, a process in which an impure feed of LiCO2 is mixed
with an aqueous solution and reacted with CO2, preferably under pressure,
to produce dissolved aqueous LiHCO3. Insoluble impurities such as iron,
magnesium and calcium are removed by physical means such as filtration or
centrifugation. Soluble divalent or trivalent ions such as magnesium, calcium
and iron are adsorbed by selective ion exchange or other similar methods.
Carbon dioxide is then completely or partially removed by raising the solution
temperature or otherwise and pure Li2CO3 precipitates. Preferably, at least a
part of the Solution is returned to the bicarbonation reaction Zone to enhance
the economics of the process. Undesirable impurities remain in solution. The
unrecycled Solution can be neutralized to give technical grade lithium
carbonate (i.e., having maximum impurity levels ppm of: Na(25), Ca(20),
Mg(5), Fe(0.5), K(5), SO’ (25) and B(2)). Bicarbonation can be carried out with
an excess of CO up to about 10 times the Stoichiometric requirement. Excess
CO2 can be separated and recycled to enhance process economics. In another
aspect of the present invention, bicarbonation can be carried out in a series
of reactors. Similarly, Li2CO3 precipitation can be in a series of reactors
operating at increasingly higher temperatures close to the boiling point of
Water.
Wang et al., 2011 [6th European Metallurgical Conference (EMC)] reported
the recovery of Co-Ni-Mn and precipitation of Li as carbonate from scrap EV
batteries. However, main drawback of the reported process includes the lack
of discussion on Li extraction at different parameters. Choubey et al., 2020
[Rare Metal Technology, 275-281] which reported the recovery of Mn and Cc
as oxides from discarded toy batteries. However, the major drawback of the
reported process is the lack of information on the Li extraction from
subsequent leach liquor. Jian et al., 2012 [Procedia Environmental Sciences,
16, 495-499] investigated a process to recover Li and Co using H2SO4 with
H2O2, followed by separation of Co and Li using P507 and finally
sedimentation with oxalic acid and carbonic acid were carried out to get Co
salt. However, drawback of the reported process includes the lack of
investigation on the extraction of Li from processed leached solution. Guo et
al 2017 [Journal of Environmental management, 198 (1), 84-89] which
reported two-stage precipitation process using Na2CO3 and Na3PO4 to recover
Li as 74.72% Li2CO3 and 92.21% Li3PO4, respectively from effluent. However,
drawback of the reported investigation is the lack of studies on the role of
temperature during Li precipitation. The literature review shows that, there is
a lack of detail study on the recovery of lithium from effluent of discarded
lithium-ion batteries generated after extraction of copper, nickel cobalt and
manganese.

Description:Novelty of present invention is the recovery of lithium from effluent generated during the recycling of spent lithium-ion batteries. initially, effluent was collected and analyzed to determine the concentration of lithium along with other impurities like sodium. As per the analysis report 2-4 g/L lithium and 30-40 g/L sodium present in the solution. This effluent was used as feed material for recovery of lithium. As per the literature review, sodium carbonate is widely used for the recovery of lithium carbonate from spent lithium-ion batteries. But, sodium content of sodium carbonate also incorporates with the lithium carbonate, which decreases its purity. Alternatively, we have replaced the sodium carbonate with carbon dioxide gas for precipitation of lithium carbonate. Thus, purity of lithium carbonate was increased up-to analytical grade, which may be re-used in the manufacturing of lithium cobalt oxide of lithium-ion batteries.
Various experiments have been carried out at different experimental conditions such as pH of the solution, temperature, CO2 flow rate etc., to enhance the precipitation efficiency of lithium carbonate and its purity.
Finally, we have successfully recovered the analytical grade lithium carbonate
with its purity close to 99.5%.
Based on the laboratory and pilot scale experimental data and purity of product lithium carbonate), the developed process will also be cost effective. The techno economic of the lithium carbonate precipitation from effluent using carbon dioxide will be calculated after commercialization of the process.

During the experiments various process parameters like pH (7-12), temperature (50-90° C), reaction time (1-5 hours) and flow rate (0.4-0.8 L/hour) of carbon dioxide were varied to optimize the conditions for precipitation of lithium carbonate from effluent processed solution of spirit lithium-ion batteries. Result shows that 98.5% lithium precipitate as lithium carbonate at 90° C between pH 10-12, when carbon dioxide gas was spared at low rate of 0.8 L/h. Further, precipitated lithium carbonate was washed with, demineralized water to remove sodium entrapped in the lithium carbonate, as a result lithium carbonate, purity increased up-to 99.5%.

Example 1
Precipitation of Li from effluent of discarded batteries was carried out at various pH (Table 1) using carbon dioxide as a precipitant at 90 °C while sodium hydroxide used to maintain pH of solution between 7 to 12. Table 1 shows that precipitation of lithium increases with increased in pH due to decrease in the solubility of lithium carbonate with increase of pH of the solution. Above the pH 10, almost complete precipitation of lithium was occurred with carbon dioxide when sparged at a rate of 08 L/hour (Table 1).

Hence, 10-12 pH has been considered as optimum pH for maximum precipitation of lithium as lithium carbonate from effluent.

Table 1
pH Li2CO3 precipitation (%)
7-8 43.2
8-9 52.2
9-10 78.3
10-12 98.6
Example 2

Effect of solution temperature on Li precipitation was also studied varying the solution temperature between 50 to 90 °C using CO2 as a precipitant, while maintaining the pH of the solution between 10 to 12. The results presented in Table 2 indicate that 98.5% Li gets precipitated as lithium carbonate at 90 °C, while sparging the CO2 at a flow rate of 0.8 L/hour. The increased of precipitation efficiency with rise of temperature is due to decrease in the solubility of lithium carbonate. Thus, 90 °C temperature has been chosen as a optimum temperature for maximum precipitation of lithium carbonate.

Table 2
Temp (°C) Precipitation of Li2CO3 (%)
50 45.1
70 76.2
90 98.5

Example 3
In order to optimize the stoichiometric requirement of CO2 to precipitate the Li from effluent, experiments were carried by sparging the CO2 between the flow rate 0.4 to 0.8 L/hour at 90 °C while pH was kept constant between 10 to 12. Table 3 shows that precipitation efficacy of lithium carbonate increases with increase in the flow rate of carbon dioxide due to maximum availability of carbon dioxide to react with lithium. Finally, purity of lithium carbonate was analyzed by chemical process, which was found more than 99.5%.

Table 3
CO2 flow rate (L/hour) Precipitation of Li2CO3 (%)
0.4 L/hour 30.9
0.6 L/hour 65.8
0.8 L/hour 98.5
Example 4
Reaction time were varied from 1 hour to 5 hours to optimize the time for precipitation of lithium from effluent containing 15 g/L Li at 90 °C while maintaining the carbon dioxide flow rate 0.8L/hour. It was found that precipitation of lithium increases with increase in the reaction time. Table 4 shows that 98.5% Li precipitated in 5 hours at 90 °C while using the carbon dioxide as a precipitant. Finally, a complete process flow sheet drawn for recovery of lithium carbonate from effluent is presented in Fig. 1.
Table 4
Reaction time (hours) Precipitation of Li2CO3 (%)
1 19.3
3 62.3
5 98.5
, C , C , Claims:A process for the selective recovery of lithium (Li) from effluent of spent lithium- ion batteries, which comprises the following steps:
1. Collection and analysis of effluent left after the recovery of copper, nickel, manganese and cobalt from leach liquor of spent LIBS. Evaporation of effluent to enrich the lithium concentration up to 15 g/L for effective recovery of lithium from effluent. Optimization of equilibrium pH and temperature for precipitation of lithium carbonate from effluent of spent LIBS. A pH range of 10-12 was found adequate to precipitate the lithium from effluent of LIBs at 90 °C. Addition of carbon dioxide at different flow rate in the effluent obtained at steps to precipitate the lithium, in form of lithium carbonate (Li2CO3). CO2 was sparged in the effluent at a rate flow of 0.8 L/hour for 5 hours to completely precipitate the lithium carbonate. Washing of precipitated lithium carbonate with de-mineralized water to remove the sodium and enhance the purity of lithium carbonate. Finally recovered analytical grade lithium carbonate which has purity ~99.5% that can be re-used in manufacturing of lithium-ion batteries or any other energy storage devices.
2. A process as claimed in claim 1 above wherein a process which helps Evaporated effluent to enrich lithium concentration up to 15 g/L.
3. A process as claimed in claim 1 and 2 above wherein a pH range of 10-12 optimum equilibrium and enhances precipitation of lithium from effluent at 90°C.
4. A process as claimed in claim 1 to 3 above wherein precipitated lithium carbonate washed with mineral water helps to achieve 99.5% purity.
5. A process wherein analytical grade Lithium carbonate can be reused in manufacturing of lithium- ion batteries, pharmaceutical purposes and any other energy storage devices.