CN106299524A - A carbon-coated current collector that is easy to separate powder from foil and its application and recycling method - Google Patents

Abstract

The invention discloses a carbon-coated current collector easy for separating powder from foil, which comprises a current collector foil, wherein one side or two sides of the current collector foil are provided with water-soluble carbon coatings, and the water-soluble carbon coatings are composed of the following raw materials in percentage by weight: 20-50% of water-soluble resin, 40-70% of carbon material and 0-20% of dispersing agent, wherein the thickness of the current collector foil is 5-25 μm, and the thickness of the water-soluble carbon coating is 1-4 μm. The water-soluble carbon coating layer is easy to dissolve by water, and has electrolyte resistance and NMP resistance. The invention also discloses a recovery method of the carbon coating current collector easy for separating the powder from the foil, which enables the water-soluble carbon coating layer between the anode material and the aluminum foil to be fully dissolved through the steps of soaking, stirring, filtering and the like, thereby realizing the effective separation of the anode material and the aluminum foil current collector.

Description

A carbon-coated current collector that is easy to separate powder from foil and its application and recycling method

technical field

The invention belongs to the field of lithium ion battery material recovery, in particular to a carbon-coated current collector which is easy to separate powder from foil and its application.

Background technique

The problem of environmental pollution is becoming more and more serious, and people's awareness of environmental protection is gradually getting stronger. Traditional energy produces huge carbon emissions, and its impact on the global climate is becoming more and more obvious. In particular, vehicles fueled by traditional fossil fuels have put a heavy pressure on the environment. As the proportion of new energy in the energy structure gradually increases, future new energy vehicles will gradually replace traditional vehicles. my country's support for new energy vehicles is gradually increasing. At present, the batteries used in new energy vehicles are mainly lithium-ion batteries. Lithium-ion batteries have the advantages of high energy density, high voltage, long life and no memory effect, making them the first choice for electric vehicles.

With the large-scale use of lithium-ion batteries in electric vehicles, the recycling of used batteries will be a huge problem. The main parts of the battery are the battery cell, the electrolyte and the battery case. The battery case can be easily recycled by cutting and dismantling. The electrolyte is a volatile liquid and is relatively easy to separate. However, the positive and negative active materials in the battery are not easy to separate from the aluminum foil, copper foil, etc. The positive electrode active material is closely combined with the aluminum foil through PVDF; the negative electrode active material is firmly adhered to the copper substrate through SBR glue. In current industrial applications, the main method to separate the active material from the base material is to destroy the adhesive force of the binder by heating at high temperature, then mechanically pulverize, and separate the metal base material from the active material through a blast system. This method has many operating procedures, and the heating and crushing links consume a large amount of energy, and cause pollution such as air and dust. The resulting isolates were of limited purity.

The key to separate the active material from the foil is to eliminate the adhesion between PVDF, SBR, etc. force interaction. Using some organic solvents such as NMP, xylene, etc. can effectively dissolve these binders, destroy the bonding, and achieve separation, but these solvents are harmful to the human body, pollute the environment and have high costs.

Contents of the invention

The purpose of the present invention is to overcome the prior art and provide a carbon-coated current collector that is easy to separate the powder from the foil and its application and recovery method. The method has the advantages of high efficiency, no pollution, simple process, low cost and low energy consumption. advantage.

The purpose of the present invention can be achieved through the following technical solutions:

A carbon-coated current collector that is easy to separate powder from the foil, comprising a current collector foil, characterized in that one or both sides of the current collector foil have a water-soluble carbon coating, and the water-soluble carbon The coating is composed of the following raw materials in weight percentage: 20-50% water-soluble resin, 40-70% carbon material, 0-20% dispersant, the thickness of the current collector foil is 5-25μm, and the water-soluble carbon coating The layer thickness is 1-4 μm.

The water-soluble resin is one or more of polyurethane, acrylic resin, polyester resin, water-soluble polymer, alkyd resin, and acrylonitrile multi-polymer.

The carbon material is one or more of carbon black, SP, acetylene black, graphene, graphite, and carbon nanotubes.

The dispersant is one or more of supramolecular dispersants, alkylphenol polyvinyl ethers, polyacrylates, alkyl polyoxyethylene ethers, metal phosphates, and polysiloxane dispersants.

The invention also discloses the application of a carbon-coated current collector which is easy to separate the powder material from the foil material in the lithium-ion battery.

The invention also discloses a method for recycling carbon-coated current collectors that are easy to separate powder and foil materials, including the following steps:

(1) Cut the positive electrode sheet of the lithium-ion battery into slices of a certain size;

(2) Soak in water at a certain temperature for a certain period of time;

(3) Stir with a mixer at a speed of 20-1000r/min for 0-3h;

(4) Filtrate with a sieve with a pore size ≥ 10mm to obtain the current collector foil;

(5) Filter through a 50-1000 mesh screen to obtain the active material isolate.

The positive pole piece of the lithium ion battery is formed by adhering lithium iron phosphate, lithium cobaltate, lithium manganate or ternary materials on a carbon-coated current collector.

The slice area is between 0.001-0.02m ² .

The temperature of the water is between 0-100°C, and the soaking time is between 0-48h.

The mixer is one of paddle, wheel, screw and anchor mixers.

Carbon-coated aluminum foil is a composite material coated with a carbon conductive layer on the aluminum foil current collector. Carbon-coated aluminum foil has the advantages of reducing internal resistance, improving cycle performance and extending life, and has been widely used in lithium iron phosphate-based batteries. The carbon material conductive layer of the carbon-coated aluminum foil has a thickness of 1-4 μm. The aqueous slurry for preparing carbon-coated aluminum foil is mainly composed of graphite particles or carbon black, dispersant and binder. Binders and dispersants make up between 20-50% of the coating. The use of carbon-coated aluminum foil also brings greater flexibility to battery recycling. When the active material is coated on the surface of carbon-coated aluminum foil, the PVDF in it is combined with the carbon material and binder on the surface. On aluminum foil, resulting in better adhesion. In order to realize the separation of the aluminum foil and the active material, it is necessary to destroy the force between the binder and the aluminum foil in the original carbon coating layer.

When designing the carbon coating layer of carbon-coated aluminum foil, resins with better water solubility are used as binders. These resins are characterized by containing more water-soluble groups, including hydroxyl groups, carboxyl groups, anions and cations. In particular, salinized resins containing more anions (such as COO ^- ) in the main chain or side chain have good water solubility and cannot be dissolved by organic solvents such as NMP and electrolyte. There is no cross-linking between the resins after film formation, and the resin has excellent corrosion resistance to ester, alcohol and ketone solvents. The positive electrode slurry uses NMP as a solvent, and the solvents such as EC, DEC, and DMC in the electrolyte have no corrosive effect on the coating, but the coating can quickly dissolve when it encounters water again. When the battery is recycled, soak the positive electrode sheet in water and stir it with a certain amount of machinery, so that the positive electrode active material can be quickly separated from the current collector, and the aluminum foil and the positive electrode active material can be quickly and effectively separated. The separation method uses water as a solvent and has no pollution problem. During the stirring process, only an appropriate amount of stirring force needs to be provided, and the energy consumption is relatively small.

Beneficial effects of the present invention: the water-based carbon-coated aluminum foil current collector of the present invention has high water solubility, strong resistance to NMP and electrolyte, and good processing and use performance. The design method of the present invention is beneficial to the separation of the positive electrode active material and the current collector when recycling the positive electrode sheet of the lithium battery, and the separation link uses water as the solvent, the process is simple and effective, the cost is low, and the energy consumption is low. A green and efficient method.

Description of drawings

Fig. 1 is an effect diagram of wiping the carbon-coated aluminum foil obtained in Example 1 of the present invention with water, NMP and electrolyte.

In the figure: 1. Cotton swab soaked in water; 2. Coating peeling off; 3. Water-soluble carbon coating layer; 4. Aluminum foil substrate; 5. Cotton swab soaked in NMP; 6. Cotton swab soaked in electrolyte.

detailed description

The present invention will be described in further detail below in conjunction with the accompanying drawings and specific embodiments.

In the present invention, the current collector foil material is the same material as the aluminum foil and the current collector aluminum foil.

Example 1

A carbon-coated current collector that is easy to separate powder from the foil, comprising a current collector foil, one side of the current collector foil has a water-soluble carbon coating, and the water-soluble carbon coating is composed of the following raw materials in weight percentage: Water-soluble acrylic resin 50%, carbon black 50%. The thickness of the water-soluble carbon coating is 2 μm, the thickness of the current collector aluminum foil is 15 μm, the front and back are coated with lithium iron phosphate cathode material, and the thickness of the front and back is 70 μm after rolling.

The application of the carbon-coated current collector which is easy to separate the powder and the foil material in the lithium ion battery. The carbon-coated current collector is a composite material coated with a carbon conductive layer on the aluminum foil current collector. Carbon-coated aluminum foil has the advantages of reducing internal resistance, improving cycle performance and extending life, and has been widely used in lithium iron phosphate-based batteries. The carbon material conductive layer of the carbon-coated aluminum foil has a thickness of 1-4 μm. The aqueous slurry for preparing carbon-coated aluminum foil is mainly composed of graphite particles or carbon black, dispersant and binder. Binders and dispersants make up between 20-50% of the coating. The use of carbon-coated aluminum foil also brings greater flexibility to battery recycling. When the active material is coated on the surface of carbon-coated aluminum foil, the PVDF in it is combined with the carbon material and binder on the surface. On aluminum foil, resulting in better adhesion. In order to realize the separation of the aluminum foil and the active material, it is necessary to destroy the force between the binder and the aluminum foil in the original carbon coating layer.

Take 1kg of the positive electrode sheet, of which the mass of the aluminum foil is: 70g; the material of the positive electrode is: 930g. Cut the pole piece into slices with an average area of ^0.01m2 .

After soaking in 5 kg of water at a temperature of 50°C for 3 hours, transfer to a paddle mixer and stir for 1 hour at a speed of 100 r/min.

Filter through a wire mesh with a pore size of 15 mm to obtain an aluminum foil, dry it, and weigh 74 g.

Filter through a 150-mesh sieve to obtain a positive electrode material isolate, dry it, and weigh 770 g. The rest of the turbid liquid was discharged into the settling tank, and after settling for 1 hour, the upper layer of clear water was taken. The sediment was part of the positive electrode material, which was dried and weighed as 120g.

The calculated positive electrode material recovery rate is 95.7%; the current collector aluminum foil recovery rate is close to 100%. The recovered aluminum foil recovered its metallic color, and no visible black substance was attached.

Example 2

A carbon-coated current collector that is easy to separate powder from the foil, comprising a current collector foil, one side of the current collector foil has a water-soluble carbon coating, and the water-soluble carbon coating is composed of the following raw materials in weight percentage: Water-soluble silicone modified PVA 20%, acetylene black 70%, supramolecular dispersant 10%. The thickness of the water-soluble carbon coating is 1 μm, the current collector aluminum foil is 5 μm, the front and back are coated with lithium iron phosphate cathode material, and the thickness of the front and back is 70 μm after rolling.

Take 1kg of the positive electrode sheet, of which the mass of the aluminum foil is: 70g; the material of the positive electrode is: 930g. Cut the pole piece into slices with an average area of ^0.015m2 .

After soaking in 6kg of water at a temperature of 100°C for 0.5h, transfer to a paddle mixer and stir for 2h at a speed of 20r/min.

Filter through a wire mesh with a pore size of 20 mm to obtain an aluminum foil, dry it, and weigh 71 g.

Filter through a 50-mesh sieve to obtain the positive electrode material isolate, dry it, and weigh 720 g. The rest of the turbid liquid was discharged into the settling tank, and after settling for 1 hour, the upper layer of clear water was taken. The sediment was part of the positive electrode material, which was dried and weighed as 185g.

Calculate the recovery rate of cathode material: 97.3%; the recovery rate of aluminum foil is close to 100%. There is no visible black substance attached to the surface of the recovered aluminum foil.

Example 3

A carbon-coated current collector that is easy to separate the powder from the foil, including the current collector foil, the two sides of the current collector foil have a water-soluble carbon coating, and the water-soluble carbon coating is composed of the following raw materials in weight percentage: Water-soluble polyester resin 40%, graphene 40%, polyacrylate dispersant 20%. The thickness of the water-soluble carbon coating is 4 μm, the aluminum foil is 25 μm, the front and back are coated with lithium iron phosphate cathode material, and the thickness of the front and back is 70 μm after rolling.

Take 1kg of the positive electrode sheet, of which the mass of the aluminum foil is: 70g; the material of the positive electrode is: 930g. Cut the pole piece into slices with an average area of ^0.02m2 .

After soaking in 5 kg of water at a temperature of 0°C for 48 hours, transfer to a paddle mixer and stir for 3 hours at a speed of 500 r/min.

Filter through a wire mesh with a pore size of 10 mm to obtain an aluminum foil, dry it, and weigh 68 g.

Filter through a 200-mesh sieve to obtain the positive electrode material isolate, dry it, and weigh 697 g. The rest of the turbid liquid was discharged into the settling tank, and after settling for 1 hour, the upper layer of clear water was taken. The sediment was part of the positive electrode material, which was dried and weighed as 214g.

Calculate the recovery rate of cathode material: 98.0%; the recovery rate of aluminum foil is close to 97%. There is no visible black substance attached to the surface of the recovered aluminum foil.

Fig. 1 is the solvent resistance test of the water-soluble carbon-coated aluminum foil in Example 1 of the present invention. The foil is completely exposed after being wiped with water once, but it is still intact after being wiped with NMP and electrolyte for 300 times. It shows that the carbon coating designed by the present invention dissolves when it encounters water, and has better resistance to NMP and electrolyte. It is not corroded by organic solvents when used in lithium batteries, and is easily dissolved by water in the recycling process.

The above content is only an example and description of the structure of the present invention. Those skilled in the art make various modifications or supplements to the described specific embodiments or replace them in similar ways, as long as they do not deviate from the structure of the invention or Anything beyond the scope defined in the claims shall belong to the protection scope of the present invention.

Claims (10)

1. it is prone to the carbon coated collector that powder separates with foil, including collector foil, it is characterised in that described afflux The single or double of body foil has containing water-soluble carbon coating, former by following weight percent content of described water-soluble carbon coating Material composition: water-soluble resin 20-50%, material with carbon element 40-70%, dispersant 0-20%, described collector foil thickness is 5-25 μ M, water-soluble carbon coating layer thickness is 1-4 μm.

The most according to claim 1 it is prone to the carbon coated collector that powder separates with foil, it is characterised in that described water-soluble Property resin is in polyurethane, acrylic resin, polyester resin, water soluble polymer, alkyd resin, acrylonitrile multiple copolymer One or more.

The most according to claim 1 it is prone to the carbon coated collector that powder separates with foil, it is characterised in that described carbon material Material is one or more in white carbon black, SP, acetylene black, Graphene, graphite, CNT.

The most according to claim 1 it is prone to the carbon coated collector that powder separates with foil, it is characterised in that described dispersion Agent is supermolecule dispersant, polyacrylate, alkyl phenol polyvinylether, alkyl polyoxyethylene ether, metal tripolyphosphate salt, poly-silicon One or more in oxygen alkanes dispersant.

5. one kind is prone to the application in lithium ion battery of carbon coated collector that powder separates with foil.

6. the recovery method being prone to the carbon coated collector that powder separates with foil, it is characterised in that comprise the following steps:

(1) anode slice of lithium ion battery is cut into a certain size section；

(2) with the water soaking certain time of uniform temperature；

(3) 0-3h is stirred with blender with 20-1000r/min rotating speed；

(4) collector foil is obtained with the screen filtration of aperture >=10mm；

(5) it is filtrated to get active substance separator with 50-1000 eye mesh screen.

Method the most according to claim 6, it is characterised in that described anode slice of lithium ion battery by LiFePO4, Cobalt acid lithium, LiMn2O4 or ternary material stick to form in carbon coated collector.

Method the most according to claim 6, it is characterised in that described section area is at 0.001-0.02 m²Between.

Method the most according to claim 6, it is characterised in that described coolant-temperature gage is between 0-100 DEG C, and soak time exists 0-48h。

Method the most according to claim 6, it is characterised in that described blender is paddle, wheeled, spiral and anchor One in formula blender.