CN113745682A

CN113745682A - Method for disassembling lithium metal cathode from lithium battery

Info

Publication number: CN113745682A
Application number: CN202010461094.8A
Authority: CN
Inventors: 孔德钰; 郇庆娜; 陈强; 牟瀚波; 李振宇; 张月
Original assignee: China Energy Lithium Co ltd
Current assignee: China Energy Lithium Co ltd
Priority date: 2020-05-27
Filing date: 2020-05-27
Publication date: 2021-12-03

Abstract

The invention discloses a method for safely disassembling a lithium metal cathode from a lithium battery, which comprises the following steps: step one, preprocessing of a single battery is obtained; punching holes at the positive and negative lugs; step three, injecting passivation solution into the cathode hole; step four, standing; and fifthly, breaking the shell or the outer package of the single battery to take out the metal lithium cathode. The disassembly step of the invention is safe, can be carried out in the atmosphere, does not need protective atmosphere, and reduces the disassembly difficulty.

Description

Method for disassembling lithium metal cathode from lithium battery

Technical Field

The invention belongs to the technical field of energy batteries, relates to a lithium battery treatment method, and particularly relates to a method for safely disassembling a metal lithium cathode from a lithium battery.

Background

The battery is used as an electrochemical energy storage device and is widely applied to the fields of communication, new energy automobiles, daily consumer goods and the like. In the research field of electrode materials, a lithium metal negative electrode is always a hot point of research due to the high theoretical capacity (3860mAh/g) and the lowest electrochemical potential (-3.04V versus standard hydrogen electrode). Particularly, as the performance of lithium batteries tends to be ceiling and people desire high energy density of batteries, people look to advanced battery systems including all-solid-state batteries, lithium-sulfur batteries, lithium-oxygen batteries and the like, and the advanced battery systems all adopt metal lithium as a negative electrode material. However, because the international dependency of lithium resources in China is high and the usage amount of the lithium metal in the advanced battery system is large, the lithium metal cathode in the advanced battery system is bound to be recycled for maintaining national energy safety and realizing the full-life cycle management of the battery.

In the battery circulation process, the current densities of the surface areas of the metal lithium are different due to the difference of the surface states of the metal lithium negative electrodes; dendrite is easily generated in a region where the current density is large; along with the volume change of the lithium metal negative electrode, the dendrite can be continuously broken and accumulated to form dead lithium; when the metal lithium battery fails, a layer of loose and porous dead lithium is formed on the surface of the metal lithium negative electrode. Because the dead lithium is very active, after the battery pole piece is released from a tight assembly state, the dead lithium is easy to generate heat and spontaneously combust when meeting air; therefore, particular attention should be paid to safety issues when disassembling lithium metal negative electrodes from lithium metal batteries. At present, a safe disassembly process for the metal lithium cathode is not available.

Disclosure of Invention

The invention aims to realize the safe disassembly of the metal lithium battery by a method for safely disassembling the metal lithium cathode from the metal lithium battery, thereby achieving the aim of maximally recovering and enriching the metal lithium material.

The technical scheme adopted by the invention comprises the following steps:

in some embodiments, there is provided a method of safely disassembling a lithium metal anode from a lithium battery, comprising:

step one, preprocessing of a single battery is obtained;

punching holes at the positive and negative lugs;

step three, injecting passivation solution into the cathode hole;

step four, standing;

and fifthly, breaking the shell of the single battery or the outer package and taking out the metal lithium cathode.

The method of the invention can have the following beneficial effects:

(1) the disassembling step is safe;

(2) the method can be carried out under the atmosphere, does not need protective atmosphere, and reduces the disassembling difficulty.

Drawings

Fig. 1 is a flow chart of a method for safely disassembling a metallic lithium negative electrode from a lithium battery according to the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

The following examples are typical examples of the product structure parameters, the reaction participants and the process conditions, but through the experiments of the present inventors, the other structure parameters, the reaction participants and other process conditions listed above are also applicable and all the claimed technical effects can be achieved.

Fig. 1 is a flow chart illustrating a method for safely disassembling a lithium metal negative electrode from a lithium battery according to the present invention. As shown in fig. 1, the method for safely disassembling a lithium metal negative electrode from a lithium battery according to the present invention can be roughly divided into 5 steps: step one, a pretreatment step, namely obtaining a single battery; punching holes at the positive and negative lugs; step three, injecting passivation solution into the cathode hole; step four, standing; and fifthly, breaking the shell or the outer package of the single battery to take out the metal lithium cathode.

The pretreatment stage can comprise appearance cleaning, module discharging, module splitting, single battery discharging and the like, and aims to obtain the low-voltage single battery. For example, module disassembly first removes a module case, and then removes a Battery Management System (BMS), a module cooling system, a module frame, a conductive connector, etc., to obtain a unit battery. In order to obtain the single battery with low voltage, the module can be discharged first, and then the single battery with higher voltage is discharged after the module is disassembled. Wherein, the module discharges with 0.5C (C is module capacity) for about 2 hours, then the module is left for about 0.5 hour, and then discharges with 0.5C for 1 hour; after the module is disassembled to obtain the single battery, voltage detection is carried out on the single battery, and the single battery with the voltage higher than 2.7V is discharged at the constant voltage of 2.7V until the current is less than 0.05C (wherein C is the capacity of the single battery). The unit cells below 2.7V do not need to be discharged.

And step two, punching holes at the positive and negative lugs to provide an injection port and an overflow port for the passivation solution, wherein the injection port is a hole on the negative side of the metal lithium, and the hole on the positive side is used as the overflow port for the passivation solution, so that the internal pressure of the battery is not increased during liquid injection. For safety reasons, the preferred perforation is mechanical perforation or needle punching. The punching depth penetrates through the single battery packaging material. The diameter of the holes should not be too large to prevent a large amount of air from entering the inside of the battery, so the diameter of the holes should be less than 5mm, preferably less than 2 mm.

Injecting passivation solution, wherein the passivation solution can firstly play a liquid sealing role to isolate the contact between air and dead lithium; secondly, the passivating solution can coat or react to consume the highly reactive "dead lithium". The injection amount of the passivation solution is at least to ensure that the negative electrode of the battery is completely soaked, and at most, the passivation solution is discharged from the overflow port. The passivating liquid is typically composed of a solvent and a lithium reactive solute. The solvent may be an anhydrous solvent, including polar solvents and non-polar solvents, such as tetrahydrofuran, n-hexane, and other alkane solvents, and the like. The solute can be inorganic acid, organic acid, such as phosphoric acid, polyalkyl phosphonic acid, etc., and can also be a macromolecular compound containing a group capable of reacting with the metallic lithium and a hydrophobic group, for example, the reactive group can comprise phosphoric acid group, carboxylic acid group, etc.; the hydrophobic group may include C₄-C₂₂Alkyl radical, C₆-C₂₄At least one of an aryl group and a siloxane group; comprisesThe high molecular compound having a group reactive with lithium metal and a hydrophobic group may include oleic acid, octadecylphosphoric acid, and the like. Taking the passivation efficiency as an index, the tetrahydrofuran solution dissolved with phosphoric acid crystals or polyalkyl phosphonic acid is a preferred combination. In addition, the proportion of the phosphoric acid crystal and the solvent is also important, and the proper proportion (for example, the proportion of the solvent to the phosphoric acid is 1000: 1-10: 1 in terms of mass ratio) can achieve the passivation effect, reduce the consumption of the phosphoric acid and reduce the passivation cost.

And step four, standing to ensure that sufficient coating or reaction time exists between the dead lithium and the passivation solution and ensure that the dead lithium cannot have safety accidents in the subsequent steps. Usually, the mixture is allowed to stand at normal temperature for 2 to 24 hours. In addition, the environmental temperature can be properly increased during standing, the diffusion speed of the passivation solution is increased on the premise of ensuring safety, and the coating or reaction time is shortened.

And fifthly, cracking the single battery shell or the outer package. The optimal solution may use mechanical disassembly. The purpose is to take out the metallic lithium cathode so as to realize the recovery and enrichment of the metallic lithium cathode.

All steps can be carried out at ambient temperature in the atmosphere, without the need for a protective atmosphere.

The method for disassembling the metallic lithium cathode from the lithium battery can be applied to various battery systems containing the metallic lithium cathode, such as all-solid-state batteries, lithium-sulfur batteries, lithium-oxygen batteries and the like.

Example 1

And carrying out voltage detection on the 5Ah soft package single metal lithium battery.

After detection is finished, the metal lithium battery with the voltage lower than 2.7V does not need to discharge. The battery having a voltage higher than 2.7V was subjected to constant voltage discharge, the voltage was set to 2.7V, and the discharge cutoff current was 0.25A.

And (3) carrying out needle punching perforation on the pretreated metal lithium battery, using a steel needle with the diameter of 2mm, carrying out needle punching on the anode tab and the cathode tab of the battery, and piercing the single-layer aluminum-plastic film.

And (3) injecting the tetrahydrofuran solution dissolved with the phosphoric acid crystals into the battery by using an injector, injecting the tetrahydrofuran solution into the negative electrode tab, stopping injecting when a small amount of liquid overflows from an overflow port at the positive electrode tab, and injecting passivation solution which is a solution of 1g of phosphoric acid crystals dissolved in 1L of tetrahydrofuran.

And standing the single battery injected with the passivation solution for 4 hours at the standing temperature of 45 ℃.

And after standing, cutting the aluminum plastic film packaging bag by using scissors, and collecting the positive plate, the diaphragm and the lithium metal negative electrode in a classified manner to obtain the lithium metal negative electrode.

It should be understood that the above-mentioned embodiments are merely preferred embodiments of the present invention, and not intended to limit the present invention, and any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for safely disassembling a metal lithium cathode from a lithium battery is characterized in that: the method comprises the following steps:

step one, preprocessing of a single battery is obtained;

punching holes at the positive and negative lugs;

step three, injecting passivation solution into the cathode hole;

step four, standing; and

and fifthly, breaking the shell or the outer package of the single battery to take out the metal lithium cathode.

2. The method of claim 1, wherein: the pretreatment comprises at least one of appearance cleaning, module discharging, module disassembling and single battery discharging treatment.

3. The method of claim 1, wherein: the passivating solution is composed of a solvent and a lithium reactive solute.

4. The method of claim 3, wherein: the solvent includes a polar solvent and a non-polar solvent.

5. The method of claim 4, wherein: the solvent comprises tetrahydrofuran or an alkane solvent.

6. The method of claim 3, wherein: the lithium-reactive solute includes an inorganic acid, an organic acid, or a polymer compound having a group reactive with metallic lithium and having a hydrophobic group.

7. The method of claim 3, wherein: the lithium reactive solute includes at least one of phosphoric acid, polyalkylphosphonic acids, oleic acid, and octadecylphosphoric acid.

8. The method of claim 1, wherein: the standing is carried out at ambient temperature for 2-24 hours.

9. The method of claim 1, wherein: the lithium battery includes an all-solid-state battery, a lithium sulfur battery, or a lithium oxygen battery.

10. The method according to any one of claims 1-9, wherein: the steps one to five are carried out under the atmosphere.