Kinetics of Ni and Co Recovery via Oxygen-Enriched Pressure Leaching from Waste Lithium-Ion Batteries

Abstract

In the process of the comprehensive recovery and utilization of discarded lithium-ion batteries via acid leaching, a large number of NiS and CoS mixed materials are produced. To improve the metal recovery rate, the kinetics and rate-determining step of the oxygen-rich pressurized acid leaching of Ni and Co were investigated. The results showed that the leaching rates of Ni and Co were greater than 99% under the following conditions: sulfuric acid (leaching agent) concentration of 95 g/L, liquid-to-solid ratio of 6:1, leaching time of 120 min, temperature of 110 °C, stirring speed of 400 r/min, 90% oxygen-rich atmosphere, and pressure of 1.2 MPa. The leaching of Ni and Co was described by the shrinking unreacted core model, and the leaching rates of Ni and Co conformed to the kinetic equation 1 − (1 − x)^1/3 = k·t. The apparent activation energies of the Ni and Co leaching reactions were 50.87 and 45.6 kJ/mol, respectively, and the leaching process was found to be controlled by the chemical reaction at the interface.

1. Introduction

According to data released by the China Automotive Power Battery Industry Innovation Alliance [1], the total sales volume of power batteries in 2019 was 75.6 GWh, a year-on-year increase of 21.4%. The sales volume of NMC (short for nickel, manganese, and cobalt composite) series ternary batteries amounted to 53.0 GWh, a year-on-year increase of 53.4%; in addition, the sales volume of lithium iron phosphate batteries was 20.6 GWh, a year-on-year decrease of 15.6%. Overall, ternary batteries accounted for 70.0% of the total sales, a year-on-year increase of 15%. With the increase in the market demand for power batteries, the number of scrapped batteries will inevitably increase. In 2020, the global mass of waste lithium-ion batteries exceeded 500,000 tons. It is estimated that by 2023, the global scrapped amount will reach approximately 1.16 million tons and 3 million tons by 2027. If comprehensive recycling and utilization are not conducted, there will be severe environmental pollution and waste of valuable metal resources. Therefore, considering the related resource utilization, environmental protection, and economic benefits, the development and implementation of effective recycling and utilization methods for waste power batteries are urgently needed. Moreover, to ensure the sustainable development of the emerging electric vehicle industry, power batteries in the late life cycle stage must be recycled, forming a closed loop.

The comprehensive recycling of waste lithium-ion batteries via the acid leaching method produces a leaching solution containing high concentrations of Ni and Co and low concentrations of Al, Si, and other impurities. The Al and Si impurities are generally removed from the leaching solution via a chemical method whereby light calcium carbonate is used as a neutralizing agent. After the chemical impurity removal, the Al and Si contents of the leaching solution are controlled at approximately 0.05 g/L. Subsequently, iron removal is performed, during which a large amount of Al and Si slag is produced. During the removal of Al and Si using light calcium carbonate, the pH is controlled at approximately 5.0, and under such a pH, part of the Ni and Co in the leaching solution precipitates into NiCO₃ and CoCO₃ and mixes with the aluminum–silicon slag, reducing the recovery rates of the Ni and Co. At present, the handling of aluminum–silicon slag containing a high Ni content is performed via acid leaching [2,3,4,5,6,7,8,9,10,11,12,13] and pressure acid leaching [14,15,16,17,18,19,20]. The leaching solution with high Ni and low Co and Al contents obtained after acid leaching is treated with Na₂S to precipitate the Ni, Co, and Al from the Ni mother liquor, producing a mixture of high-grade NiS and CoS. However, NiS and CoS have relatively stable chemical properties and cannot be completely converted into NiSO₄ and CoSO₄ solutions by sulfuric acid leaching at normal pressure. Therefore, the focus of this study was the efficient conversion of NiS and CoS into NiSO₄ and CoSO₄ solutions to ensure the subsequent preparation of electrodeposited Ni and Co, thereby achieving the comprehensive recovery and utilization of Ni and Co from waste batteries.

Although several studies on the pressurized acid leaching of nickel ore have been reported [21,22,23,24,25], there are no reports of kinetic studies of a mixture of high-grade NiS and CoS obtained via chemical precipitation in a high-pressure oxygen-rich environment. In this study, the reaction mechanism and feasibility of the oxygen-rich pressure leaching of a mixture of high-grade NiS and CoS were analyzed. The effects of the stirring rate, reaction temperature, initial acidity, and reaction time on the leaching rate were investigated. The kinetic factors controlling Ni and Co leaching were also discussed to provide technical support for the wet refining and electrodeposition of NiSO₄ and CoSO₄ from NiS and CoS mixed materials.

2. Experimental Section

2.1. Materials and Equipment

The chemical composition of the NiS and CoS mixed materials used in this study was analyzed by means of chemical analysis, and the results are listed in

Table 1. Analysis results of the NiS and CoS mixed materials (%).

Element	Ni	Co	Fe	Al	Si	S	H2O
Content	32.48	0.45	1.08	<0.001	<0.001	28.62	37.37

.

All the chemical reagents used in this study, such as H₂SO₄ and O₂, were of industrial grade. More specifically, 98% H₂SO₄ produced by Yunnan Copper Industry and 99% O₂ produced by Kunming Tianbei Special Gas Co., Ltd. (Kunming, China) were used. The oxygen pressure acid leaching was performed in a 2 L titanium high-pressure reactor, as shown in Figure 1. Atomic absorption spectrophotometry (AA-7000, Shimadzu, Guangzhou, China) was used to determine the concentrations.

2.2. Experimental Methods

This study was carried out using a 2 L titanium-lined autoclave. A dry mass of 200 g of mixed NiS and CoS was accurately weighed and placed in the reactor (under high pressure). Sulfuric acid (75–100 g/L) was added to control the liquid-to-solid ratio at 6:1. The stirring speed was adjusted to a predetermined value (250–550 r/min), O₂ was blown into the reactor to the required pressure (0.8–1.6 MPa), and the reactor was heated to the required temperature. After a predetermined reaction time (1–3 h), cooling water was passed through the kettle body to cool the reactor. When the temperature dropped below 90 °C, the kettle was opened, and the reaction materials were extracted for liquid–solid separation.

2.3. Process Flow Chart

In order to remove impurities such as Al and Si from the leaching solution obtained via the acid leaching of waste lithium-ion batteries, a chemical impurity removal method is generally adopted. Such a method typically uses light calcium carbonate as a neutralization and impurity removal agent to remove Al and Si from the leaching solution. After the chemical impurity removal, the contents of Al and Si in the leaching solution can be controlled within 0.05 g/L. After the impurity removal, the solution enters the extraction separation system for deep purification and impurity separation, and the purification solution is obtained for the production of nickel sulfate (cobalt sulfate)/electrolytic nickel (cobalt) products. Ni and Co are included in the aluminum–silicon slag obtained by removing aluminum–silicon₃ and CoCO₃ for the recovery of Ni and Co from aluminum silicon slag. Adding sulfuric acid to dissolve the aluminum silicon slag means that Si will not leach, leading to a high Ni and low Co and Al leaching solution. In this case, a chemical precipitation method is used, with Na₂S being used as the precipitator to sink Ni and Co and Al being opened from the mother liquor of the nickel sedimentation to obtain high-grade NiS/CoS mixed materials. The NiS/CoS mixed materials are obtained via oxygen-rich pressure acid leaching, and the leaching solution is incorporated into the extraction separation system. The process flow chart is shown in Figure 2.

2.4. Analysis Method

(1)

Moisture analysis method

Weigh 100 g of NiS/CoS mixed materials, put them in a disk with a volume of about 250 mL, put the materials in the oven, open the oven, and dry at 105 °C for 24 h before taking them out. After cooling in indoor air and weighing, an air-dried sample can be obtained. The H₂O content can be calculated as follows: (1 − weight after drying/mass before drying) × 100%.

(2)

Metal content analysis method

Take 1.0 g of dried NiS/CoS mixed material, put it into a beaker with magnetons, add 40 mL dilute HNO₃ solution (HNO₃ is produced by Xinxiang Senfeng Chemical Co., Ltd., Xinxiang, China), cover with 20% dilute HNO₃ solution, put the beaker into a water bath with magnetic stirring, and turn on the magnetic stirring. Heat at 80 °C for 1 h until the solution is a clear green liquid. Filter out the sulfur element on the upper layer, wash the filter paper with deionized water 3 times, combine the filtrate, and keep the volume at 250 mL. The solid solution can be detected in an AA-7000 Shimadzu atomic absorption spectrophotometer to determine the metal content.

2.5. Evaluation Indicators

The Ni and Co contents of the leaching solution and slag were analyzed using the flame atomic absorption method, and the leaching rates of Ni and Co (η) were calculated.

$$\eta =\left(1-\frac{w_1\times m_1}{w_0\times m_0}\right)\times 100\%$$

where w₁ is the mass fraction of Ni and Co in the leaching residue (%), m₁ is the mass of the leaching residue (g), w₀ is the ma ss fraction of Ni and Co in the NiS and CoS mixture (%), and m₀ is the mass of the NiS and CoS mixture (g).

3. Results and Discussion

3.1. Effect of the Initial Concentration of Sulfuric Acid on the Leaching Rates of Ni and Co

In the experiment, industrial sulfuric acid was used as the leaching agent, the liquid-to-solid ratio was 6:1, the leaching time was 120 min, the leaching temperature was 110 °C, the stirring speed was 400 r/min, the atmosphere was 90% oxygen-rich, and the pressure was controlled at 1.2 MPa. The effect of the initial sulfuric acid concentration on the leaching rates of Ni and Co was investigated, and the test results are shown in Figure 3.

As shown in Figure 3, the leaching rates of Ni and Co gradually increased with an increasing initial sulfuric acid concentration. At initial sulfuric acid concentrations exceeding 95 g/L, the leaching rates of Ni and Co did not increase significantly and were approximately 99.5% and 99.0%, respectively. Therefore, it was appropriate to maintain the initial sulfuric acid concentration at 95 g/L. An increase in the initial acidity increases the amount of H⁺ per unit volume of the solution. Under the same solid–liquid contact area, more H⁺ reacts with a variety of minerals, creating a concentration difference between the leaching solution and the surface of the ore particles and the reaction product layer inside and outside, thereby increasing the void and fracture space [26].

3.2. Effect of Stirring Speed on the Leaching Rates of Ni and Co

This experiment was conducted under the following conditions: sulfuric acid concentration of 95 g/L, liquid-to-solid ratio of 6:1, leaching time of 120 min, leaching temperature of 110 °C, 90% oxygen-rich atmosphere, and pressure of 1.2 MPa. The effect of the stirring speed on the leaching rates of Ni and Co was investigated, and the test results are shown in Figure 4.

The stirring speed is an important factor that affects diffusion [23]. As shown in Figure 4, the Ni and Co leaching rates increased with an increasing stirring speed, which is attributed to the acceleration of the mass transfer. The leaching rates of Ni and Co did not increase significantly at stirring rates exceeding 400 rpm. As a result, when the stirring rate reached 400 r/min, the leaching rates of Ni and Co were no longer affected by the diffusion of the liquid boundary layer; hence, it is appropriate to control the stirring speed at 400 r/min.

3.3. Effect of Reaction Temperature on the Leaching Rates of Ni and Co

This experiment was conducted under the following conditions: 95 g/L industrial sulfuric acid concentration, liquid-to-solid ratio of 6:1, leaching time of 120 min, stirring speed of 400 r/min, 90% oxygen-rich atmosphere, and pressure of 1.2 MPa. The effect of the leaching temperature on the leaching rates of Ni and Co was investigated, and the results are shown in Figure 5.

As shown in Figure 5, the effect of the leaching temperature on the leaching rates of Ni and Co was studied in the range of 95–120 °C. During the oxygen pressure leaching, the leaching reaction rate accelerated with an increasing temperature. Under the employed reaction conditions, the leaching rates of Ni and Co reached 99.63% and 98.92%, respectively, at 110 °C and did not increase significantly with further increases in temperature to 120 °C; therefore, 110 °C was considered the optimum reaction temperature.

3.4. Effect of Leaching Time on the Leaching Rates of Ni and Co

This experiment was conducted under the following conditions: 95 g/L industrial sulfuric acid concentration, liquid-to-solid ratio of 6:1, leaching temperature of 110 °C, stirring speed of 400 r/min, 90% oxygen-rich atmosphere, and pressure of 1.2 MPa. The effect of the leaching time on the Ni and Co leaching rates at different leaching temperatures was investigated. The test results are shown in Figure 6 and Figure 7.

As shown in Figure 6 and Figure 7, the effect of the leaching temperature on the leaching rates of Ni and Co was investigated in the range of 90–110 °C. The leaching reaction accelerated with an increasing temperature. Under the given conditions, at 120 min, the leaching rates of Ni and Co reached 99.16% and 99.02%, respectively, at 110 °C, whereas they reached 80.79% and 81.16%, respectively, at 90 °C. This indicates that the time required for Ni and Co leaching to reach equilibrium was reduced at a higher reaction temperature. At a reaction temperature of 110 °C, the leaching rates of Ni and Co did not significantly improve after 120 min, so 120 min was considered the optimum reaction time.

3.5. Reproducible Experimental Study

Based on the optimal conditions determined in the above-mentioned single-factor experiments, under the conditions of 95 g/L sulfuric acid concentration, 6:1 liquid-to-solid ratio, 120 min leaching time, 110 °C temperature, 400 r/min stirring speed, an atmosphere with 90% oxygen content, and 1.2 MPa pressure, three groups of reproducibility experiments were performed. The results are presented in

Table 2. Reproducibility of pressure leaching of an oxygen-rich NiS/CoS mixture.

Experiment Number	Leaching Rate (%)		Content in Leached Residue (%)
	Ni	Co	Ni	Co
1	99.48	99.24	0.42	0.015
2	99.62	99.52	0.48	0.018
3	99.36	99.39	0.45	0.016
Average	99.49	99.38	0.45	0.016

.

By analyzing the data in Table 2, it can be seen that under the optimized conditions for oxygen-rich pressure leaching, the Ni and Co in the NiS/CoS mixed raw materials were leached into the leaching solution at an average leaching rate of 99.49% and 99.38% for Ni and Co, respectively, producing a leaching residue with Ni and Co contents of less than 0.5% and 0.02%, respectively. This shows a higher recovery of Ni and Co. No Fe content was detected in the leaching residue, indicating that the Fe was 100% leached.

3.6. Analysis of the Effect of Oxygen Pressure on Acid Leaching of the Mixture of NiS and CoS

3.6.1. Oxidation Reaction of Sulfur

During the acid leaching of NiS and CoS, S takes on multiple oxidation states because the oxidation of S²⁻ is a complex process. The stable S-containing compounds include H₂S, HS⁻, S²⁻, HSO⁴⁻, and elemental S, as well as the unstable intermediate products S₂O₃²⁻ and S₂O₆²⁻. E–pH diagrams for different systems at 110 °C and 1.0 MPa are shown in Figure 8. As shown in the potential–pH diagram of the S–H–O system in Figure 8a [27], the S²⁻ in the NiS and CoS is easily oxidized into SO₄²⁻ under alkaline conditions, its potential is low (–0.48 V), and the reaction process is efficient. While elemental S only forms in an acidic medium with a pH < 6, at higher redox potentials, the formed elemental S can be oxidized into thiosulfuric acid or sulfate, although it must undergo two higher-potential state (S₂O₃²⁻ and S₂O₆²⁻) changes. The reaction process is complex, and the oxidation process is difficult. The lower limit of the pH in the stable zone of S changes with changes in the H₂SO₄ concentration.

Controlling the reaction temperature allows the oxidation reaction to occur at a higher oxygen partial pressure and in a shorter time, which maintains the sulfuric acid concentration in the reaction system. The oxygen pressure leaching of NiS and CoS changes the process, producing acid instead of consuming it. In the end, the reaction is controlled in the stable region of sulfur, and S²⁻ generates elemental S.

3.6.2. Oxidation Leaching Mechanism for NiS and CoS

The potential–pH diagram of the Ni–S–H–O system in Figure 8b [27] shows that the standard oxidation–reduction potential of NiS is –0.145 V, indicating that it is easy to oxidize. In an acid medium (pH < 4), NiS is oxidized to form Ni²⁺ and S; in a near-neutral solution, HSO₄⁻, NiO, S, and SO₄²⁻ are formed; and in an alkaline solution, SO₄²⁻ and HNiO²⁻ are formed. The elemental S is stable in the Ni²⁺ solution. Therefore, at a pH < 4, the oxidation of NiS proceeds to the formation of S.

The potential–pH diagram of the Co–S–H–O system in Figure 8c [27] shows that the standard oxidation–reduction potential of CoS is −0.277 V, indicating that it is easy to oxidize. Figure 8c shows that in an acidic medium (pH < 4), CoS is oxidized to form Co²⁺, S, and HSO₄⁻; in a near-neutral solution, Co₃O₄, S, and SO₄²⁻ are formed; and in an alkaline solution, SO₄²⁻, Co (OH)₂, and Co(OH)₃ are formed. The elemental S is stable in the Co²⁺ solution. Therefore, at a pH < 4, the oxidation of CoS proceeds to form S.

During oxygen pressure leaching, the oxidative dissolution of NiS and CoS into soluble sulfates is more complicated. The main reactions involved are as follows:

NiS + 2O₂ = NiSO₄

(1)

8NiS + O₂ + 2H₂SO₄ = 2Ni₃S₄↓+ 2NiSO₄ + 2H₂O

(2)

Ni₃S₄ + 6O₂ = 3NiSO₄ + S↓

(3)

2NiS + O₂ + 2H₂SO₄ = 2NiSO₄ + 2H₂O + 2S↓

(4)

CoS + 2O₂ = CoSO₄

(5)

2CoS + O₂ + 2H₂SO₄ = 2CoSO₄ + 2H₂O + 2S↓

(6)

These reactions eventually produce NiSO₄, CoSO₄, and S.

3.6.3. Oxidation of H₂S

During oxygen pressure acid leaching, the FeSO₄ in NiS and a small amount of added Na₂S react with H₂SO₄ to form H₂S and the corresponding sulfates, as shown in the following equations:

MeS + H₂SO₄ = MeSO₄ + H₂S↑

(7)

O₂ + 2H₂S = 2H₂O + S↓

(8)

3.6.4. Catalytic Oxidation of Fe Ions

The potential–pH diagram of the Fe–S–H–O system (Figure 8d) shows that the standard oxidation–reduction potentials of FeS and FeS2 are −0.065 and −0.423 V, respectively. FeS is easily oxidized in acidic solutions, and the main reactions are as follows:

2FeS + O₂ + 2H₂SO₄ = 2FeSO₄ + 2H₂O + 2S↓

(9)

FeS + H₂SO₄ = FeSO₄ + H₂S↑

(10)

4FeSO₄ + O₂ + 2H₂SO₄ = 2Fe₂(SO₄)₃ + 2H₂O

(11)

Fe³⁺ is only stable in acidic solutions. It is easily hydrolyzed into Fe₂O₃ under weakly acidic conditions (pH > 1):

Fe₂(SO₄)₃ + 3H₂O = Fe₂O₃ + 3H₂SO₄

(12)

Fe³⁺ is a strong oxidant that can oxidize NiS, CoS, and H₂S into their corresponding sulfates and elemental S during oxygen pressure leaching:

MeS + Fe₂(SO₄)₃ = 2FeSO₄ + MeSO₄ + S↓

(13)

2Fe^{3 +} +H₂S = 2Fe^{2 +} +2H ⁺ +S↓

(14)

As oxygen-rich high-pressure leaching is an acid-consuming process, some of the Fe can be hydrolyzed into Fe₂O₃ in the slag, as long as the acidity of the solution at the end point of the leaching is controlled at a low level. Under these conditions, it can also be hydrolyzed into jarosite (Na₂Fe₆(SO₄)₄(OH)₁₂) in the slag to reduce the Fe content of the leaching solution. Simultaneously, Fe³⁺ can oxidize elemental S into H₂SO₄, and the resulting FeSO₄ can be reoxidized into high-iron sulfate by the O₂ in the autoclave. Therefore, during oxygen pressure leaching, iron ions transfer electrons through the Fe³⁺ and Fe²⁺ valence changes, and “catalytic” oxidation through electron transfer occurs. This “catalytic” oxidation is a liquid-phase reaction. Compared with the gas–solid O₂ oxidation reaction of solid NiS and CoS, this reaction is faster, and it is a very important reaction step in oxygen pressure acid leaching.

According to Figure 8, NiS and CoS do not decompose at a pH = 7 when FeS exists in the material and the redox potential of the system is less than −0.5 V. At a certain potential and pH value, S is oxidized into SO₄²⁻, the acidity of the reaction system increases, the pH value decreases, and the potential increases. Fe is oxidized into Fe³⁺ and precipitates into the slag. At a pH = 2, the reaction system begins to stably accumulate ferric sulfate, and most of the FeS is oxidized into elemental S. The potential of the system increases to 0.10–0.15 V, and some of the NiS and CoS begins to oxidize and form Ni²⁺ and S. After the decomposition of FeS, the potential of the system increases to 0.20–0.25 V, and NiS and CoS begin to oxidize until complete decomposition.

To sum up, three main reactions occur during the oxygen pressure acid leaching of mixed NiS and CoS materials: direct oxidation of sulfides, H₂S oxidation, and Fe-ion-catalyzed oxidation of NiS, CoS, and H₂S. Although the direct oxidation of sulfides is slow, the leaching of Ni and Co can be completed at a relatively low oxygen pressure and in a relatively short time with the help of H₂S oxidation and Fe³⁺/Fe²⁺ electron migration-catalyzed oxidation. Most of the S ends up in an elemental form, and part of the iron remains in the leaching residue in the form of ferric red or sodium jarosite.

3.7. Leaching Kinetics Model

Multiple methods can be used to study the kinetics of liquid–solid multiphase reactions. Among them, the most commonly used reaction model is the shrinking unreacted core model [28]. The results in Section 3.2 show that at a stirring rate of 400 r/min, the effect of liquid boundary layer diffusion can be excluded. The leaching rate data in Figure 6 and Figure 7 were substituted into the shrinking unreacted core model, and the results satisfied the following equation: 1 − (1 − x)^1/3= k·t. That is, the kinetic curve controlled by the interfacial chemical reaction showed a good linear regression relationship (Figure 9 and Figure 10). This indicates that the leaching of Ni and Co followed the shrinking unreacted core model, which was controlled by the interfacial chemical reaction.

3.8. Apparent Activation Energy

The apparent activation energy is an important parameter in kinetic studies because the rate-controlling step of the leaching process can be determined by measuring the kinetic relationship and the apparent activation energy of the leaching system. The leaching rate constants of Ni and Co at different temperatures (k₁ and k₂) can be obtained by calculating the slopes in Figure 9 and Figure 10, respectively, as shown in

Table 3. Ni leaching rate constants at different temperatures.

Extraction Temperature K	Rate Constant min−1	Correlation Coefficient
363	0.0007	0.95
373	0.0012	0.98
383	0.0017	0.98

and

Table 4. Co leaching rate constants at different temperatures.

Extraction Temperature K	Rate Constant min−1	Correlation Coefficient
363	0.0007	0.96
373	0.00105	0.97
383	0.00115	0.96

.

Table 2 and Table 3 show that the rate constants of the Ni and Co leaching reactions increased significantly with an increasing temperature. This is consistent with the effect of the temperature on the leaching rates discussed in Section 3.3, indicating that the Ni–Co leaching reaction was controlled by the interfacial chemical reaction. To further verify the control steps of the reaction, ln k₁ and ln k₂ were plotted against T⁻¹ (Figure 11 and Figure 12, respectively). These figures show that ln k₁ and ln k₂ showed a very good linear relationship with T⁻¹, with correlation coefficients of −0.997 and −0.999 and slopes of −6118.584 and −5485.34, respectively. According to the Arrhenius equation, k = AE^−E/RT, the apparent activation energies of the Ni and Co leaching reactions are 50.87 and 45.6 kJ/mol, respectively. The calculated activation energies were within 40–300 kJ/mol, which further proves that the oxygen pressure acid leaching of Ni and Co from the mixture of NiS and CoS is controlled by the interfacial chemical reaction step.

4. Conclusions

Mixing at a rate of 400 r/min and higher eliminated the effect of liquid boundary layer diffusion. The leaching rates of Ni and Co significantly increased with an increasing temperature. The experimental results showed that the leaching rates of Ni and Co were more than 99% under the following conditions: sulfuric acid concentration of 95 g/L, liquid-to-solid ratio of 6:1, leaching time of 120 min, temperature of 110 °C, stirring speed of 400 r/min, atmosphere with 90% oxygen content, and pressure of 1.2 MPa. Kinetic studies showed that the kinetics of the Ni and Co leaching reactions can be described by the following equation: 1 − (1 − x)^1/3 = k·t. The leaching process followed the shrinking unreacted core model, as controlled by the interfacial chemical reaction, and the apparent activation energies of the Ni and Co leaching reactions were 50.87 and 45.6 kJ/mol, respectively.

The oxygen-rich pressure leaching process could be introduced into the waste battery recycling process to solve the problem of the loss of nickel and cobalt recovery in the process of desilication, improve the comprehensive recovery rate of nickel and cobalt throughout the whole process, and promote the optimization of the waste battery recovery process.