CN103762335A - Lithium titanate electrode plate and lithium ion battery - Google Patents

Abstract

The invention relates to a lithium titanate electrode sheet and a lithium ion battery. The lithium titanate electrode sheet includes a current collector, a lithium titanate coating layered on the current collector, and a carbon coating layered on the lithium titanate coating. The carbon coating material includes carbon materials, the first A binder and a first conductive agent. The electrolyte in the lithium-ion battery reacts with the carbon coating at a lower potential to form an SEI film, which separates the active material in the lithium titanate coating from the electrolyte and prevents the battery from bulging due to the reaction between the active material and the electrolyte due to overpotential ; Moreover, the carbon coating has a certain ability to intercalate lithium, which does not affect the transportation of lithium ions. Therefore, the lithium ion battery using the lithium titanate electrode sheet has good cycle performance.

Description

Lithium titanate electrode sheet and lithium ion battery

technical field

The invention relates to the technical field of lithium ion batteries, in particular to a lithium titanate electrode sheet and a lithium ion battery.

Background technique

A lithium-ion battery is a rechargeable battery that primarily relies on the movement of lithium ions between the positive and negative electrodes to function. Due to the advantages of high operating voltage, high specific energy, wide operating temperature range, and stable discharge, lithium-ion batteries are widely used in mobile communication equipment, tablet computers, digital products, power tools, automobiles, and energy storage systems.

Lithium titanate is a material with a spinel structure. Because the volume change is very small, almost zero, during the charging and discharging process of lithium ion insertion and extraction, it is called a "zero strain" material, and it has a very stable discharge platform. , its potential to lithium is close to 1.55V, it is not easy to precipitate lithium dendrites, and it is very safe. The diffusion coefficient of lithium ions in lithium titanate crystals is 2×10 ^-8 cm ² /s, which is an order of magnitude higher than that of graphite anodes. It can be quickly charged and discharged. At present, lithium titanate material has become a research hotspot in the field of lithium-ion batteries.

However, lithium titanate has a high lithium intercalation potential, and it is difficult to form an SEI (solid electrolyte interface) film. In actual use, especially when charging with a large current, it is easy to generate overpotential, which makes lithium titanate react with the electrolyte. And produce gas to cause the battery to bulge, affecting the cycle performance of the battery.

Contents of the invention

Based on this, it is necessary to provide a lithium titanate electrode sheet to solve the gas problem of the lithium titanate battery and improve its cycle performance.

A lithium titanate electrode sheet, comprising a current collector, a lithium titanate coating layered on the current collector, and a carbon coating layered on the lithium titanate coating, the material of the carbon coating includes carbon material, a first binder and a first conductive agent.

In one embodiment, the carbon material is selected from at least one of artificial graphite, natural graphite, soft carbon, mesocarbon microspheres and hard carbon.

In one embodiment, the average particle diameter of the carbon material is 500 nanometers to 5 micrometers.

In one embodiment, the first binder is selected from at least one of polyvinylidene fluoride, carboxymethyl cellulose and styrene-butadiene rubber, and the first conductive agent is acetylene black.

In one of the embodiments, the carbon coating is by mass percentage:

The carbon material accounts for 80% to 98%;

The first binder accounts for 0.5% to 10%; and

The first conductive agent accounts for 0.5-10%.

In one embodiment, the carbon coating has a thickness of 10 microns to 20 microns.

In one embodiment, the lithium titanate coating material includes lithium titanate, a second binder and a second conductive agent.

In one embodiment, the second binder is selected from at least one of polyvinylidene fluoride, carboxymethyl cellulose and styrene-butadiene rubber, and the second conductive agent is acetylene black.

In one of the embodiments, the lithium titanate coating is by mass percentage:

The lithium titanate accounts for 80% to 98%;

The second binder accounts for 0.5% to 10%; and

The second conductive agent accounts for 0.5-10%.

A lithium-ion battery, comprising a casing, an electric core disposed in the casing, and an electrolyte filled in the casing, the electric core includes a positive electrode sheet, a diaphragm, and a negative electrode sheet stacked in sequence, and the negative electrode The sheet is the aforementioned lithium titanate electrode sheet.

The above-mentioned lithium titanate electrode sheet includes sequentially laminating current collector, lithium titanate coating and carbon coating, and the electrolyte and carbon coating react at a lower potential to form an SEI film, which separates the active material in the lithium titanate coating from the electrolyte. Open to prevent the battery from swelling due to the reaction between the active material and the electrolyte caused by the overpotential; moreover, the carbon coating has a certain ability to intercalate lithium and does not affect the transportation of lithium ions. Therefore, the lithium titanate electrode sheet can improve the cycle performance of the lithium ion battery.

Description of drawings

Fig. 1 is the structural representation of the lithium titanate electrode sheet of an embodiment;

FIG. 2 is a graph comparing cycle curves of the lithium ion battery of Example 1 and the lithium ion battery of the comparative example.

Detailed ways

In order to make the above objects, features and advantages of the present invention more comprehensible, specific implementations of the present invention will be described in detail below in conjunction with the accompanying drawings. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. However, the present invention can be implemented in many other ways different from those described here, and those skilled in the art can make similar improvements without departing from the connotation of the present invention, so the present invention is not limited by the specific implementations disclosed below.

Please refer to FIG. 1 , a lithium titanate electrode sheet 100 according to an embodiment includes a carbon coating 10 , a lithium titanate coating 20 and a current collector 30 . The lithium titanate coating 20 is stacked on the current collector 30 , and the carbon coating 10 is stacked on the lithium titanate coating 20 .

The material of the carbon coating 10 includes a carbon material, a first binder and a first conductive agent.

The carbon material is a carbon material with a small particle size. Preferably, the average particle diameter (D50) of the carbon material is 500 nanometers to 5 micrometers.

Preferably, the carbon material is selected from at least one of artificial graphite, natural graphite, soft carbon, mesocarbon microspheres and hard carbon.

The average particle diameter D50 of artificial graphite, natural graphite, soft carbon, mesocarbon microspheres and hard carbon is preferably 500 nanometers to 5 micrometers.

The first binder is selected from at least one of polyvinylidene fluoride (PVDF), carboxymethyl cellulose (CMC) and styrene-butadiene rubber (SBR). The first conductive agent is acetylene black.

The lithium titanate electrode piece 100 is used as a negative electrode in a lithium-ion battery. After the lithium-ion battery is precharged and formed, since the lithium titanate electrode piece 100 includes a carbon coating 10, an SEI film can be formed on the surface of the negative electrode to prevent The electrolyte is in contact with the surface of the lithium titanate electrode sheet 100, avoiding the reaction between the electrolyte and the active material in the lithium titanate coating 20, and solving the problem of gas production in the traditional lithium titanate battery; meanwhile, the SEI film itself is a good Lithium-ion conductor, will not affect the performance of lithium-ion batteries.

In the carbon coating 10, the carbon material has a lithium intercalation effect, so that the normal transportation of lithium ions in the lithium titanate electrode sheet 100 can still be guaranteed after the carbon coating 10 is installed, so as to realize the normal insertion and extraction of lithium ions without affecting the lithium ion battery. performance.

The first binder acts as a bonding agent for bonding the carbon material and the first conductive agent, and makes the carbon coating 10 adhere better to the lithium titanate coating 20 .

The first conductive agent is used to improve conductivity. Lithium titanate coatings of traditional lithium-ion batteries all contain conductive agents, and generally no additional conductive agents are added. Since the carbon coating 10 covers the surface of the lithium titanate coating 20, in order to further increase the migration rate of lithium ions, thereby increasing the charging and discharging rate. An appropriate amount of first conductive agent is added to the carbon coating 10 .

Preferably, in the carbon coating 10 , by mass percentage, the carbon material accounts for 80%-98%, the first binder accounts for 0.5%-10%, and the first conductive agent accounts for 0.5%-10%.

Materials of the lithium titanate coating 20 include lithium titanate, a second binder and a second conductive agent.

The second binder is at least one selected from polyvinylidene fluoride, carboxymethyl cellulose and styrene-butadiene rubber, and the second conductive agent is acetylene black.

Preferably, in the lithium titanate coating 20 , by mass percentage, lithium titanate accounts for 80%-98%, the second binder accounts for 0.5%-10%, and the second conductive agent accounts for 0.5-10%.

According to the above ratio, the lithium titanate coating 20 can better realize the insertion and extraction of lithium ions, and improve the performance of the lithium ion battery.

Preferably, the lithium titanate coating 20 has a thickness of 40 microns to 200 microns.

The current collector 30 is preferably copper foil or aluminum foil.

Since the lithium titanate electrode sheet 100 is provided with the carbon coating 10 stacked on the lithium titanate coating 20, the electrolyte and the carbon coating 10 react at a lower potential to form an SEI film, and the activity in the lithium titanate coating 20 The material is separated from the electrolyte to prevent the battery from bulging due to the reaction between the active material and the electrolyte due to overpotential. The SEI film itself is a good lithium ion conductor and will not affect the performance of the lithium ion battery.

Moreover, since the carbon coating 10 contains carbon materials, it has a certain lithium intercalation capability and does not affect the transportation of lithium ions. Therefore, the lithium titanate electrode sheet 100 can improve the cycle performance of the lithium ion battery.

If the thickness of the carbon coating 10 is too small, the preparation process requires high requirements; if the thickness of the carbon coating 10 is too large, it is not conducive to exert the advantages of the lithium titanate coating 20 . Therefore, preferably, the thickness of the carbon coating 10 is 10 microns to 20 microns.

More preferably, the carbon coating 10 has a thickness of 15 microns.

Compared with the lithium titanate negative electrode coated with insulating oxide on the surface of the lithium titanate electrode sheet 100, the carbon coating 10 is formed on the lithium titanate coating 20, and the lithium ion battery is pre-charged and formed on the surface of the negative electrode. The SEI film prevents the electrolyte from reacting with the electrode surface, and solves the problem of gas production in lithium titanate batteries; at the same time, the SEI film itself is a good lithium ion conductor and will not affect the performance of the battery.

Compared with the carbon-coated lithium titanate material on the microscopic level, the above-mentioned lithium titanate electrode sheet 100 forms a carbon coating 10 on the lithium titanate coating 20, which can avoid the problem that the uneven coating affects the performance of the battery .

The above-mentioned lithium titanate electrode sheet 100 is prepared as follows:

Step S110: preparing lithium titanate coating slurry.

Add the lithium titanate, the second binder and the second conductive agent into the second solvent, and stir evenly to obtain the lithium titanate coating slurry.

Preferably, the mass ratio of the lithium titanate, the second binder and the second conductive agent is 80-98:0.5-10:0.5-10.

The second solvent is N-methylpyrrolidone or water.

Step S120: coating the lithium titanate coating slurry on the current collector, and forming a lithium titanate coating on the current collector after drying.

Preferably, drying is performed at 80° C. to 110° C. to volatilize the second solvent to form a lithium titanate coating on the current collector.

The stirring speed is preferably 3000r/min to 5000r/min.

Step S130: Prepare carbon coating slurry.

Add the carbon material, the first binder and the first conductive agent into the first solvent, and stir evenly to obtain a carbon coating slurry.

Preferably, the mass ratio of the carbon material, the first binder and the first conductive agent is 80-98:0.5-10:0.5-10.

The first solvent is N-methylpyrrolidone or water.

The stirring speed is preferably 3000r/min to 5000r/min.

Step S140: coating the carbon coating slurry on the lithium titanate coating, and forming a carbon coating on the lithium titanate coating after drying to obtain a lithium titanate electrode sheet.

Preferably, drying is performed at 80° C. to 110° C. to volatilize the first solvent to form a carbon coating on the lithium titanate coating to obtain a lithium titanate electrode sheet.

A lithium-ion battery according to an embodiment includes a casing, a battery cell disposed in the casing, and an electrolyte filled in the casing.

The battery cell includes a positive electrode sheet, a separator and a negative electrode sheet stacked in sequence.

The positive sheet includes a current collector and a positive active layer stacked on the current collector. The material of the positive active layer includes positive active material, conductive agent and binder. The positive electrode active material is at least one selected from lithium cobalt oxide, lithium manganate, lithium iron phosphate, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide and lithium nickel manganese oxide.

The negative electrode sheet is the aforementioned lithium titanate electrode sheet 100 .

The reaction of the carbon coating 10 in the negative electrode sheet with the electrolyte to form the SEI film needs to consume lithium ions, so the positive electrode is designed in excess. Preferably, the positive electrode excess design coefficient is 1.01-1.25.

Prepare above-mentioned lithium ion battery as follows:

The positive electrode sheet, separator, and negative electrode sheet are stacked and wound in sequence, and then put into the casing, and electrolyte solution is injected into the casing to assemble a lithium-ion battery. After the assembly is completed, the formation is carried out. The formation system is to charge at 0.1C-5C constant current and constant voltage to 2.8V-4.0V, and the cut-off current is 0.01C-0.05C.

The lithium-ion battery uses the lithium titanate electrode sheet 100 as the negative electrode sheet, which solves the problem of gas production in the traditional lithium titanate battery. Therefore, the cycle performance of the lithium ion battery is better.

Further elaborate below by specific embodiment.

Example 1

Preparation of lithium titanate electrode sheet and lithium ion battery

1. Take 100g of polyvinylidene fluoride binder, 20g of acetylene black conductive agent and 2kg of lithium titanate, and evenly disperse them in 2kg of N-methylpyrrolidone, stir and disperse at a high speed of 3000r/min, and stir evenly to obtain lithium titanate coating slurry;

2. Coat the lithium titanate coating slurry on the copper foil and dry it at 90°C to form a lithium titanate coating on the copper foil. The thickness of the lithium titanate coating is 150 microns;

3. Take 10g of polyvinylidene fluoride binder, 15g of acetylene black conductive agent, and 200g of artificial graphite with an average particle size of 500nm, and uniformly disperse them in 200g of N-methylpyrrolidone, stir and disperse at a high speed of 3000r/min, stir Uniformly obtain carbon coating slurry;

4. Coat the carbon coating slurry on the lithium titanate coating, dry it at 90°C, form a carbon coating on the lithium titanate coating, and obtain a lithium titanate electrode sheet; wherein, the carbon coating The thickness is 15 microns;

5. Provide a positive electrode sheet and a negative electrode sheet. The positive electrode sheet includes aluminum foil and a positive electrode active layer laminated on the aluminum foil. The material of the positive electrode active layer includes lithium manganate with a mass ratio of 1:50:10, polyvinylidene fluoride binder and acetylene black conductive agent, and the negative electrode sheet is the above-mentioned lithium titanate electrode sheet. After winding and injecting liquid, it is assembled into a lithium-ion battery. It is formed into a constant current and constant voltage of 0.1C to 3.9V, and the cut-off current is 0.05C. The capacity retention rate after 500 cycles at 1C was 98%.

Example 2

Preparation of lithium titanate electrode sheet and lithium ion battery

1. Take 60g of polyvinylidene fluoride binder, 30g of acetylene black conductive agent and 2kg of lithium titanate, and evenly disperse them in 2.5kg of N-methylpyrrolidone, stir and disperse at a high speed of 4000r/min, and stir evenly to obtain titanic acid Lithium coating paste;

2. Coat the lithium titanate coating slurry on the copper foil and dry it at 95°C to form a lithium titanate coating on the copper foil. The thickness of the lithium titanate coating is 80 microns;

3. Take 15g of polyvinylidene fluoride binder, 15g of acetylene black conductive agent and 200g of artificial graphite with an average particle size of 800nm, and evenly disperse them in 220g of N-methylpyrrolidone, and stir and disperse at a high speed of 3500r/min. Stir evenly to obtain carbon coating slurry;

4. Coat the carbon coating slurry on the lithium titanate coating, dry it at 100°C, form a carbon coating on the lithium titanate coating, and obtain a lithium titanate electrode sheet; wherein, the carbon coating The thickness is 14 microns;

5. Provide a positive electrode sheet and a negative electrode sheet. The positive electrode sheet includes aluminum foil and a positive electrode active layer laminated on the aluminum foil. The material of the positive electrode active layer includes nickel cobalt lithium manganese oxide with a mass ratio of 1:30:15, polyvinylidene fluoride binder and acetylene black conductive agent, and the negative electrode sheet is the above-mentioned lithium titanate electrode sheet. After winding and liquid injection, it is assembled into a lithium-ion battery. It is formed into a constant current and constant voltage of 0.2C to 3.8V, and the cut-off current is 0.05C. The capacity retention rate after 500 cycles at 1C was 99%.

Example 3

Preparation of lithium titanate electrode sheet and lithium ion battery

1. Take 10g of polyvinylidene fluoride binder, 10g of acetylene black conductive agent and 0.98kg of lithium titanate, and evenly disperse them in 2.3kg of N-methylpyrrolidone, stir and disperse at a high speed of 3000r/min, and stir evenly to obtain titanium Lithium acid coating slurry;

2. Coat the lithium titanate coating slurry on the copper foil and dry it at 105°C to form a lithium titanate coating on the copper foil. The thickness of the lithium titanate coating is 60 microns;

3. Take 5g of polyvinylidene fluoride binder, 9g of acetylene black conductive agent and 190g of soft carbon with an average particle size of 1 micron, and evenly disperse them in 250g of N-methylpyrrolidone, and stir and disperse at a high speed of 5000r/min. Stir evenly to obtain carbon coating slurry;

4. Coat the carbon coating slurry on the lithium titanate coating, dry it at 110°C, form a carbon coating on the lithium titanate coating, and obtain a lithium titanate electrode sheet; wherein, the carbon coating The thickness is 13 microns;

5. Provide a positive electrode sheet and a negative electrode sheet. The positive electrode sheet includes aluminum foil and a positive electrode active layer laminated on the aluminum foil. The material of the positive electrode active layer includes nickel cobalt lithium manganese oxide with a mass ratio of 1:40:20, polyvinylidene fluoride binder and acetylene black conductive agent, and the negative electrode sheet is the above lithium titanate electrode sheet. After winding and liquid injection, it is assembled into a lithium-ion battery. It is formed into a constant current and constant voltage of 0.3C to 3.7V, and the cut-off current is 0.05C. The capacity retention rate after 500 cycles at 1C was 98%.

Example 4

Preparation of lithium titanate electrode sheet and lithium ion battery

1. Take 100g of polyvinylidene fluoride binder, 20g of acetylene black conductive agent and 0.88kg of lithium titanate, and evenly disperse them in 200g of N-methylpyrrolidone, stir and disperse at a high speed of 3000r/min, and stir evenly to obtain titanic acid Lithium coating paste;

2. Coat the lithium titanate coating slurry on the aluminum foil and dry it at 85°C to form a lithium titanate coating on the aluminum foil. The thickness of the lithium titanate coating is 100 microns;

3. Take 18g of polyvinylidene fluoride binder, 2g of acetylene black conductive agent and 380g of hard carbon with an average particle size of 2 microns, and evenly disperse them in 400g of N-methylpyrrolidone, and stir and disperse at a high speed of 5000r/min. Stir evenly to obtain carbon coating slurry;

4. Coat the carbon coating slurry on the lithium titanate coating, dry at 90°C, form a carbon coating on the lithium titanate coating, and obtain a lithium titanate electrode sheet; wherein, the carbon coating The thickness is 16 microns;

5. Provide a positive electrode sheet and a negative electrode sheet. The positive electrode sheet includes aluminum foil and a positive electrode active layer laminated on the aluminum foil. The material of the positive electrode active layer includes lithium manganate with a mass ratio of 1:50:10, polyvinylidene fluoride binder and acetylene black conductive agent, and the negative electrode sheet is the above-mentioned lithium titanate electrode sheet. After winding and liquid injection, it is assembled into a lithium-ion battery. It is formed into a constant current and constant voltage of 0.4C to 3.6V, and the cut-off current is 0.05C. The capacity retention rate after 500 cycles at 1C was 97%.

Example 5

Preparation of lithium titanate electrode sheet and lithium ion battery

1. Take 50g of polyvinylidene fluoride binder, 10g of acetylene black conductive agent and 0.94kg of lithium titanate, and evenly disperse them in 2.1kg of N-methylpyrrolidone, stir and disperse at a high speed of 4000r/min, and stir evenly to obtain titanium Lithium acid coating slurry;

2. Coat the lithium titanate coating slurry on the aluminum foil and dry it at 95°C to form a lithium titanate coating on the aluminum foil. The thickness of the lithium titanate coating is 120 microns;

3. Take 30g of polyvinylidene fluoride binder, 15g of acetylene black conductive agent, and 600g of mesocarbon microspheres with an average particle size of 5 microns, and evenly disperse them in 600g of N-methylpyrrolidone, at a high speed of 4000r/min Stir to disperse, and stir evenly to obtain carbon coating slurry;

4. Coat the carbon coating slurry on the lithium titanate coating, dry it at 90°C, form a carbon coating on the lithium titanate coating, and obtain a lithium titanate electrode sheet; wherein, the carbon coating The thickness is 15 microns;

5. Provide a positive electrode sheet and a negative electrode sheet. The positive electrode sheet includes aluminum foil and a positive electrode active layer laminated on the aluminum foil. The material of the positive electrode active layer includes lithium nickel cobalt aluminate with a mass ratio of 1:50:10, polyvinylidene fluoride binder and acetylene black conductive agent, and the negative electrode sheet is the above-mentioned lithium titanate electrode sheet. After winding and liquid injection, it is assembled into a lithium-ion battery. It is formed into a constant current and constant voltage of 0.4C to 3.6V, and the cut-off current is 0.05C. The capacity retention rate after 500 cycles at 1C was 98%.

Example 6

Preparation of lithium titanate electrode sheet and lithium ion battery

1. Take 100g of polyvinylidene fluoride binder, 100g of acetylene black conductive agent and 0.8kg of lithium titanate, and evenly disperse them in 2.1kg of N-methylpyrrolidone, stir and disperse at a high speed of 4000r/min, and stir evenly to obtain titanium Lithium acid coating slurry;

2. Coat the lithium titanate coating slurry on the copper foil and dry it at 95°C to form a lithium titanate coating on the copper foil. The thickness of the lithium titanate coating is 120 microns;

3. Take 20g of polyvinylidene fluoride binder, 10g of acetylene black conductive agent, 400g of artificial graphite with an average particle size of 3 microns and 400g of natural graphite with an average particle size of 3 microns, and uniformly disperse them in 800g of N-methylpyrrolidone , stir and disperse at a high speed of 4000r/min, stir evenly to obtain carbon coating slurry;

4. Coat the carbon coating slurry on the lithium titanate coating, dry it at 90°C, form a carbon coating on the lithium titanate coating, and obtain a lithium titanate electrode sheet; wherein, the carbon coating The thickness is 10 microns;

5. Provide a positive electrode sheet and a negative electrode sheet. The positive electrode sheet includes aluminum foil and a positive electrode active layer laminated on the aluminum foil. The material of the positive electrode active layer includes nickel cobalt lithium manganese oxide with a mass ratio of 1:50:10, polyvinylidene fluoride binder and acetylene black conductive agent, and the negative electrode sheet is the lithium titanate electrode sheet mentioned above. After winding and liquid injection, it is assembled into a lithium-ion battery. It is formed into a constant current and constant voltage of 0.5C to 3.6V, and the cut-off current is 0.05C. The capacity retention rate after 500 cycles at 1C was 99%.

Example 7

Preparation of lithium titanate electrode sheet and lithium ion battery

1. Take 40g of carboxymethyl cellulose binder, 60g of styrene-butadiene rubber binder, 5g of acetylene black conductive agent and 0.895kg of lithium titanate, and evenly disperse them in 2kg of water, stir and disperse at a high speed of 4000r/min, stir Uniformly obtain lithium titanate coating slurry;

2. Coat the lithium titanate coating slurry on the copper foil and dry it at 80°C to form a lithium titanate coating on the copper foil. The thickness of the lithium titanate coating is 200 microns;

3. Take 2g of carboxymethyl cellulose binder, 2g of styrene-butadiene rubber binder, 1g of acetylene black conductive agent and 98g of hard carbon with an average particle size of 4 microns, and evenly disperse them in 200g of water, at a speed of 4000r/min Stir at high speed to disperse, and stir evenly to obtain carbon coating slurry;

4. Coat the carbon coating slurry on the lithium titanate coating, dry it at 80°C, form a carbon coating on the lithium titanate coating, and obtain a lithium titanate electrode sheet; wherein, the carbon coating The thickness is 20 microns;

5. Provide a positive electrode sheet and a negative electrode sheet. The positive electrode sheet includes aluminum foil and a positive electrode active layer laminated on the aluminum foil. The material of the positive electrode active layer includes lithium cobaltate with a mass ratio of 1:50:10, polyvinylidene fluoride binder and acetylene black conductive agent, and the negative electrode sheet is the above-mentioned lithium titanate electrode sheet. After winding and injecting liquid, it is assembled into a lithium-ion battery. It is formed into a constant current and constant voltage of 0.1C to 3.9V, and the cut-off current is 0.05C. The capacity retention rate after 500 cycles at 1C was 98%.

comparative example

Preparation of lithium titanate electrode sheet and lithium ion battery

1. Take 100g of polyvinylidene fluoride binder, 20g of acetylene black conductive agent and 2kg of lithium titanate, and evenly disperse them in 2kg of N-methylpyrrolidone, stir and disperse at a high speed of 3000r/min, and stir evenly to obtain lithium titanate coating slurry;

2. Coat the lithium titanate coating slurry on the copper foil, and dry it at 90°C to form a lithium titanate coating on the copper foil to obtain a lithium titanate electrode sheet; wherein, the lithium titanate coating The thickness is 150 microns;

3. Provide a positive electrode sheet and a negative electrode sheet. The positive electrode sheet includes an aluminum foil and a positive electrode active layer laminated on the aluminum foil. The material of the positive electrode active layer includes lithium manganate with a mass ratio of 1:50:10, polyvinylidene fluoride binder and acetylene black conductive agent, and the negative electrode sheet is the above-mentioned lithium titanate electrode sheet. After winding and injecting liquid, it is assembled into a lithium-ion battery. It is formed into a constant current and constant voltage of 0.1C to 3.9V, and the cut-off current is 0.05C. The capacity retention rate after 500 cycles at 1C was 82%.

Refer to FIG. 2 for a comparison of the cycle curves of the lithium-ion battery of Example 1 and the lithium-ion battery of the comparative example. It can be seen from FIG. 2 that the cycle performance of the lithium ion battery of Example 1 is better than that of the lithium ion battery of the comparative example.

The above-mentioned embodiments only express several implementation modes of the present invention, and the description thereof is relatively specific and detailed, but should not be construed as limiting the patent scope of the present invention. It should be pointed out that those skilled in the art can make several modifications and improvements without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent for the present invention should be based on the appended claims.

Claims (10)

1. a lithium titanate electrode slice, is characterized in that, comprises collector, is laminated in the lithium titanate coating on described collector and is laminated in the carbon coating in described lithium titanate coating, and the material of described carbon coating comprises material with carbon element, the first binding agent and the first conductive agent.

2. lithium titanate electrode slice according to claim 1, is characterized in that, described material with carbon element is selected from least one in Delanium, native graphite, soft carbon, carbonaceous mesophase spherules and hard carbon.

3. lithium titanate electrode slice according to claim 1 and 2, is characterized in that, the average grain diameter of described material with carbon element is 500 nanometer～5 micron.

4. lithium titanate electrode slice according to claim 1, is characterized in that, described the first binding agent is selected from least one in Kynoar, carboxymethyl cellulose and butadiene-styrene rubber, and described the first conductive agent is acetylene black.

5. lithium titanate electrode slice according to claim 1, is characterized in that, described carbon coating by mass percentage:

Described material with carbon element accounts for 80%～98%;

Described the first binding agent accounts for 0.5%～10%; And

Described the first conductive agent accounts for 0.5～10%.

6. lithium titanate electrode slice according to claim 1, is characterized in that, the thickness of described carbon coating is 10 microns～20 microns.

7. lithium titanate electrode slice according to claim 1, is characterized in that, the material of described lithium titanate coating comprises lithium titanate, the second binding agent and the second conductive agent.

8. lithium titanate electrode slice according to claim 7, is characterized in that, described the second binding agent is selected from least one in Kynoar, carboxymethyl cellulose and butadiene-styrene rubber, and described the second conductive agent is acetylene black.

9. lithium titanate electrode slice according to claim 7, is characterized in that, described lithium titanate coating by mass percentage:

Described lithium titanate accounts for 80%～98%;

Described the second binding agent accounts for 0.5%～10%; And

Described the second conductive agent accounts for 0.5～10%.

10. a lithium ion battery, comprise housing, be arranged at battery core and filling electrolyte in described housing in described housing, described battery core comprises the positive plate, barrier film and the negative plate that stack gradually, it is characterized in that, described negative plate is the lithium titanate electrode slice as described in claim 1～9 any one.

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