A method for recycling lithium resources in waste lithium batteries for lithium battery negative electrode lithium supplement

Abstract

The application discloses a method for recycling lithium resources in waste lithium batteries for anode lithium supplement of lithium batteries, and belongs to the technical field of lithium battery recycling. The method comprises the following steps: recycling the positive electrode of the waste lithium battery, and connecting an external circuit to control the amount of lithium electrodeposited on the aluminum foil. A layer of aluminum-lithium alloy is formed on the surface of the aluminum foil. The aluminum-lithium alloy is used as a modification layer on the surface of the negative electrode of the lithium ion battery. The aluminum-lithium alloy not only provides a lithium supplement effect for lithium loss caused by the formation of the SEI film of the negative electrode, but also provides a high reversible capacity as a part of the negative electrode material. The recycling method is simple to operate, avoids the invalid waste of the positive electrode in the waste lithium battery, and can achieve precise control of the prelithiation degree compared with a commonly used negative electrode lithium supplement method. The aluminum foil used is low in price, reduces production cost, is simple to operate, and has small safety hazards.

Description

Technical Field

[0001] This invention belongs to the field of lithium battery recycling technology, and specifically relates to a method for recycling lithium resources from waste lithium batteries for lithium replenishment of the negative electrode of lithium batteries. Background Technology

[0002] Lithium-ion batteries (LIBs) possess advantages such as high energy density, long cycle life, and no memory effect, making them one of the most promising electrochemical energy storage systems. However, the formation of the solid electrolyte interface (SEI) on the negative electrode of a LIB consumes a large number of lithium ions, leading to low initial coulombic efficiency (ICE) and severe energy density decay. To address these issues, additional active lithium ions are introduced through various lithium sources. These extra lithium ions are sacrificed to form the SEI, ultimately resulting in improved battery capacity and energy density.

[0003] Currently, the common method for lithium replenishment in negative electrodes is to directly mix lithium foil, lithium powder, or other lithium-containing metal materials into the negative electrode or press them onto the surface of the negative electrode active material. Insufficient lithium replenishment cannot adequately improve the battery's initial coulombic efficiency, while excessive replenishment may lead to the formation of a metallic lithium coating on the negative electrode surface. Lithium foil requires extremely thin layers to achieve precise lithium replenishment; foils thinner than 20 μm are mechanically brittle. Due to the high activity of lithium powder posing safety risks, FMC proposed a lithium carbonate-coated lithium powder (SLMP) solution to improve lithium powder stability. However, while lithium carbonate protects the lithium metal, it inhibits lithium replenishment efficiency and requires a hydrostatic pressing process to activate SLMP and the use of large amounts of toxic and harmful solvents such as toluene for dispersion. Therefore, it is essential to develop a negative electrode lithium replenishment agent with precise lithium replenishment, good stability, and safety to improve battery performance. Summary of the Invention

[0004] The purpose of this invention is to propose a method for recovering lithium resources from waste lithium batteries and using them for lithium replenishment of the negative electrode of lithium batteries. The positive electrode of the recovered waste lithium battery is used as the positive electrode, and the degree of pre-lithiation on aluminum foil is controlled by an external circuit. The aluminum-lithium alloy formed on the surface of the aluminum foil replenishes lithium to the negative electrode of the lithium battery.

[0005] To achieve the above-mentioned objectives, the present invention provides the following technical solution: a method for recycling lithium resources from waste lithium batteries for lithium replenishment of the negative electrode of lithium batteries, comprising the following steps:

[0006] Step 1, with a surface density of 2-6 mg / cm³ 2 Aluminum foil is used as the negative electrode, waste lithium battery as the positive electrode, and waste lithium battery separator as the separator. After adding electrolyte, they are assembled into a half cell. The aluminum foil is pre-lithiated with a current of 0.1 to 1.0 mA to ensure that the pre-lithiation degree is 20% to 60%.

[0007] Step 2: Use the pre-lithiated aluminum foil from Step 1 as a modification layer on the negative electrode surface of the lithium-ion battery to assemble a full cell.

[0008] Preferably, in step 1, the aluminum foil is pre-lithiated with a current of 0.1 to 0.5 mA to ensure that the degree of pre-lithiation is 20% to 60%.

[0009] Preferably, in step 1, the positive electrode of the discarded lithium battery is the electrode sheet after discharge.

[0010] Preferably, in step 1, the positive electrode of the waste lithium battery is selected from any one of lithium iron phosphate, ternary lithium, and lithium manganese iron phosphate.

[0011] Preferably, in step 2, the negative electrode of the full cell is a graphite electrode.

[0012] Specifically, the areal density of the active material in the graphite electrode is 5–15 mg / cm³. 2 .

[0013] Preferably, in step 2, the positive electrode of the full cell is selected from any one of lithium iron phosphate, ternary lithium, and lithium manganese iron phosphate.

[0014] Specifically, the areal density of the active material in the positive electrode is 10–30 mg / cm³. 2 .

[0015] Preferably, pre-lithiated aluminum foil is roll-bonded to the negative electrode surface of the full cell to achieve lithium replenishment.

[0016] Compared with the prior art, the present invention has the following advantages:

[0017] This invention, through in-situ pre-lithiation, allows for precise control of the amount of electrodeposited lithium on aluminum foil, forming an aluminum-lithium alloy layer on the foil surface. This alloy forms a strong bond with the underlying aluminum foil, resulting in excellent conductivity. Using this aluminum-lithium alloy as a modification layer on the negative electrode surface of a lithium-ion battery not only replenishes lithium lost due to SEI film formation but also serves as part of the negative electrode material, providing high reversible capacity. Furthermore, this lithium replenishment method avoids the ineffective waste of positive electrodes in discarded lithium batteries by recycling the pre-lithiated aluminum foil from the positive electrode, and the low cost of the aluminum foil reduces battery material costs. Compared to commonly used negative electrode lithium replenishment methods, this method offers higher stability and safety, and the process conditions are simpler and more convenient. Attached Figure Description

[0018] Figure 1 The first charge-discharge curve of the pre-lithiated aluminum foil used as the negative electrode for lithium replenishment in a lithium iron phosphate full battery, as shown in Example 1.

[0019] Figure 2 The first charge-discharge curve of the pre-lithiated aluminum foil used for lithium replenishment of the negative electrode in a lithium iron phosphate full battery, as shown in Example 2.

[0020] Figure 3 The first charge-discharge curve of the pre-lithiated aluminum foil used for lithium replenishment of the negative electrode in a lithium iron phosphate full battery is shown in Example 3.

[0021] Figure 4 The image shows the XRD pattern of the pre-lithiated aluminum foil from Example 3.

[0022] Figure 5 The first charge-discharge curve of the lithium iron phosphate full battery is shown in Comparative Example 1.

[0023] Figure 6 The first charge-discharge curve of the lithium iron phosphate half-cell is shown in Comparative Example 2. Detailed Implementation

[0024] The preferred embodiments of the present invention will be described in detail below so that the advantages and features of the present invention can be more easily understood by those skilled in the art, thereby making a clearer and more explicit definition of the scope of protection of the present invention.

[0025] The lithium replenishment method of this invention recycles the pre-lithiated aluminum foil of the positive electrode from lithium batteries. The recycling method is simple to operate, avoids the ineffective waste of the positive electrode in discarded lithium batteries, and uses inexpensive aluminum foil, thus reducing battery material costs. Compared with commonly used negative electrode lithium replenishment methods, this method offers higher stability and safety, allows for precise control of the pre-lithiation degree, and has simpler and more convenient process conditions during use.

[0026] The aluminum foil used in this invention has an areal density of 2–6 mg / cm³. 2 The aluminum foil of this areal density has a moderate thickness, allowing it to serve as a negative electrode active material while simultaneously supplementing lithium, thus improving battery energy density. The external circuit current is 0.1–1.0 mA, preferably 0.1–0.5 mA, under which pre-lithiation on the aluminum foil surface is more uniform. The degree of pre-lithiation of the aluminum foil is 20%–60%, preferably 30%–50%, under which the good mechanical properties and excellent lithium supplementation effect of the aluminum-lithium alloy foil can be guaranteed.

[0027] The positive electrode of a discarded lithium battery is the electrode sheet after discharge. Positive electrode types include lithium iron phosphate, ternary lithium, and lithium manganese iron phosphate, among others. The discarded separator can completely cover the surface of the positive electrode. By using discarded lithium-rich electrodes and separators, recycling costs are significantly reduced, enabling the secondary use of waste batteries.

[0028] The electrolyte is a diluted conventional lithium-ion battery electrolyte. This is because lithium salts will precipitate after the electrodes of waste lithium batteries are dried. Using a diluted electrolyte can promote the dissolution of lithium salts and facilitate the diffusion of lithium ions during charging and discharging.

[0029] The areal density of the active material in graphite electrodes is 5–15 mg / cm³. 2Aluminum-lithium alloys can be used as both lithium supplements and anodes. By properly combining them with graphite anodes of this areal density, it is beneficial to reduce the processing cost of anodes.

[0030] The areal density of the active material in the positive electrode is 10–30 mg / cm³. 2 Since aluminum itself has a high theoretical specific capacity, aluminum-lithium alloy can be used to supplement lithium while also serving as a negative electrode, which is beneficial to improving the capacity of the negative electrode. Therefore, it is used in conjunction with a positive electrode sheet with a higher areal density of active material.

[0031] The pre-lithiated aluminum foil is rolled and bonded to the surface of the negative electrode to achieve lithium replenishment. This helps to improve the contact between the aluminum-lithium alloy and the electrode, reduce ohmic resistance, and also helps to stabilize the performance of the electrode.

[0032] Example 1

[0033] (1) The areal density is 3 mg / cm³ 2 Aluminum foil was used as the negative electrode, waste lithium battery positive electrode was used as the positive electrode, and waste separator was used as the separator. After a small amount of electrolyte was added, the battery was assembled. The aluminum foil was then lithium-intercalated (aluminum-lithium alloy foil) with a current of 0.3mA, and the pre-lithiation degree was 30%.

[0034] (2) The areal density of the active substance is 7 mg / cm³. 2 The areal density of the graphite electrode and active material is approximately 16 mg / cm³. 2 The lithium iron phosphate electrode was placed in a vacuum drying oven at 80°C for 4 hours. After the pre-lithiation was completed, the battery was disassembled in a vacuum glove box filled with argon gas. The aluminum-lithium alloy foil was taken out, rolled and attached to the surface of the graphite electrode. After adding the separator and electrolyte, it was assembled with the dried lithium iron phosphate positive electrode to form a full battery.

[0035] Figure 1 The figure shows the first charge-discharge curve of a pre-lithiated aluminum foil used as the negative electrode for lithium iron phosphate full battery in Example 1. As can be seen from the figure, the battery exhibits a charge specific capacity of 156 mAh g⁻¹ at 0.05C. -1 The discharge specific capacity is 142mAhg. -1 The coulombic efficiency is 91%, and the discharge specific capacity is approximately 15 mAh higher than that of Comparative Example 1. -1 This portion of the capacity is provided by the active lithium extracted from the aluminum-lithium alloy, used for the SEI formed by the sacrificial anode.

[0036] Example 2

[0037] This embodiment is basically the same as Embodiment 1, except that the degree of pre-lithiation of the aluminum foil is 40% by changing the lithium insertion time.

[0038] Figure 2The figure shows the first charge-discharge curve of a pre-lithiated aluminum foil used as the negative electrode for lithium iron phosphate full battery in Example 2. As can be seen from the figure, the battery exhibits a charge-discharge specific capacity of 160 mAh g⁻¹ at 0.05C. -1 The discharge specific capacity is 148mAhg. -1 The coulombic efficiency is 92%. Compared to Comparative Example 1, the discharge specific capacity is approximately 21 mAh / g higher. -1 This portion of the capacity is provided by the active lithium extracted from the aluminum-lithium alloy, used for the SEI formed by the sacrificial anode.

[0039] Example 3

[0040] This embodiment is basically the same as Embodiment 1, except that the degree of pre-lithiation of the aluminum foil is 50% by changing the lithium insertion time.

[0041] Figure 3 The figure shows the first charge-discharge curve of the pre-lithiated aluminum foil used as the negative electrode for lithium iron phosphate full battery in Example 3. As can be seen from the figure, the battery exhibits a charge specific capacity of 160 mAh g⁻¹ at 0.05C. -1 The discharge specific capacity is 153mAhg. -1 The coulombic efficiency is 95.6%. Compared to Comparative Example 1, the discharge specific capacity is approximately 26 mAh / g higher. -1 This portion of the capacity is provided by the active lithium extracted from the aluminum-lithium alloy, and the coulombic efficiency is comparable to that of Comparative Example 2, indicating that the lithium consumed by the formation of SEI at the negative electrode has been completely replenished.

[0042] Figure 4 The image shows the XRD pattern of the pre-lithiated aluminum foil in Example 3. It can be seen from the image that the Al-Li alloy formed by the pre-lithiated aluminum foil has the chemical composition of LiAl.

[0043] Comparative Example 1

[0044] The areal density of the active substance is approximately 7 mg / cm³. 2 The areal density of the graphite anode sheet and active material is approximately 16 mg / cm³. 2 The lithium iron phosphate cathode sheet was dried in a vacuum drying oven at 80°C for 4 hours before assembling the full cell.

[0045] Figure 5 The graph shows the charge-discharge curves of a lithium iron phosphate full battery at 0.05C. As can be seen from the graph, the specific capacity of the battery at 0.05C is 156 mAh g⁻¹. -1 The discharge specific capacity is 127mAh g. -1 The Coulomb efficiency is only 81.4%.

[0046] Comparative Example 2

[0047] The areal density of the active substance is approximately 16 mg / cm³. 2 The lithium iron phosphate positive electrode was dried in a vacuum drying oven at 80°C for 4 hours, and a half-cell was assembled using metallic lithium as the negative electrode.

[0048] Figure 6 The graph shows the charge-discharge curves of a lithium iron phosphate full battery at 0.05C. As can be seen from the graph, the specific capacity of the battery at 0.05C is 158 mAh g⁻¹. -1 The discharge specific capacity is 150mAh g. -1 The Coulomb efficiency is 95.0%.

Claims

1. A method for recycling lithium resources from waste lithium batteries for lithium replenishment of the negative electrode of lithium batteries, characterized in that, Includes the following steps: Step 1, with an areal density of 2 ~ 6 mg / cm³ 2 Aluminum foil is used as the negative electrode, waste lithium battery positive electrode is used as the positive electrode, and waste lithium battery separator is used as the separator. After adding electrolyte, they are assembled into a half cell. The aluminum foil is pre-lithiated with a current of 0.1 ~ 1.0 mA to ensure that the pre-lithiation degree is 20% ~ 60%. Step 2: Using the pre-lithiated aluminum foil from Step 1 as a modification layer on the negative electrode surface of the lithium-ion battery, the pre-lithiated aluminum foil is rolled and bonded to the negative electrode surface of the full battery to achieve lithium replenishment, and then assembled into a full battery.

2. The method as described in claim 1, characterized in that, In step 1, the aluminum foil is pre-lithiated with a current of 0.1 to 0.5 mA to ensure a pre-lithiation degree of 20% to 60%.

3. The method as described in claim 1, characterized in that, In step 1, the positive electrode of the waste lithium battery is the electrode sheet after discharge.

4. The method as described in claim 1, characterized in that, In step 1, the positive electrode of the waste lithium battery is selected from any one of lithium iron phosphate, ternary lithium, and lithium manganese iron phosphate.

5. The method as described in claim 1, characterized in that, In step 2, the negative electrode of the full cell is a graphite electrode.

6. The method as described in claim 5, characterized in that, The areal density of the active material in graphite electrodes is 5 ~ 15 mg / cm³. 2 .

7. The method as described in claim 1, characterized in that, In step 2, the positive electrode of the full cell is selected from any one of lithium iron phosphate, ternary lithium, and lithium manganese iron phosphate.

8. The method as described in claim 7, characterized in that, The areal density of the active material in the positive electrode is 10 ~ 30 mg / cm³. 2 .

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