WO2023240681A1 - Mass transfer acceleration and expansion reduction material for negative electrode and use - Google Patents

Abstract

The present invention relates to a mass transfer acceleration and expansion reduction material for a negative electrode and the use. The mass transfer acceleration and expansion reduction material for a negative electrode comprises at least one of a mass transfer acceleration component I and a mass transfer acceleration component II, wherein the mass transfer acceleration component I is a multipolymer, the multipolymer comprising styrene, olefin and mass transfer functional segments, and the mass transfer acceleration component II is one or a combination of carboxymethyl cellulose lithium and polyacrylic/(iso)butenoic acid-carboxymethyl cellulose lithium copolymer. Said two components can improve the charging capacity of a negative electrode, suppress lithium plating and control the cycle expansion rate, thereby improving the cycle, rate and low-temperature properties of a high-energy electrochemical device. Furthermore, when the mass transfer acceleration material simultaneously contains both of the mass transfer acceleration component I and the mass transfer acceleration component II, the improvement effect on the comprehensive properties of the electrochemical device is relatively remarkable.

Description

Materials and applications of negative electrodes to accelerate mass transfer and improve expansion Technical field

The invention belongs to the fields of electrochemical technology and electrochemical energy storage, and specifically relates to a material and application for accelerating mass transfer and improving expansion of a negative electrode.

Background technique

In order to extend the battery life of electronic devices, it is necessary to increase the energy density of battery cells. The development and application of negative electrodes with high compaction density (referred to as high compaction negative electrodes) can effectively increase the energy density and specific energy of the battery core; however, there are also some problems, such as: high cyclic expansion stress of the negative electrode material, The thickness of the pole piece increases rapidly, causing the thickness of the battery core to exceed the standard; the high-pressure compacted negative electrode has low porosity, large tortuosity, small net liquid volume, poor lithium ion transmission conditions, and large reaction polarization. In addition, the high-pressure compacted negative electrode active material has Charging capacity is often poor, and lithium precipitation side reactions are prone to occur, causing capacity attenuation and thickness expansion of the battery core. Therefore, high-energy electrochemical devices containing high-pressure anodes have average rate and cycle performance, and the cell thickness expansion rate is high. In particular, the capacity retention rate and thickness control of low-temperature cycles are not ideal.

Contents of the invention

The purpose of the present invention is to overcome the shortcomings of the prior art and provide a material and application for accelerating mass transfer and improving expansion of the negative electrode;

In order to achieve the above objects, the technical solutions adopted by the present invention are:

A material for accelerating mass transfer and improving expansion of the negative electrode, which is characterized in that it includes at least one component of a mass transfer accelerating component I and a mass transfer accelerating component II;

The accelerated mass transfer component I is a multi-component copolymer; the multi-component copolymer is formed by copolymerization of styrene, olefins and mass transfer functional monomers; wherein the molar ratio of styrene:olefin is ≥3.0; the mass transfer functional monomer : The molar ratio of the sum of the amounts of styrene and olefins is 0.05-0.25; the mass transfer functional monomer is one or a combination of an enoate ester monomer and a lithium olefin monomer;

It should be pointed out that the multi-component copolymer in this application can adopt random copolymerization, graft copolymerization or block copolymerization; its preparation method can adopt the existing preparation process, and only needs to meet its molar ratio.

The accelerated mass transfer component II is a polymer, and the polymer is carboxymethylcellulose lithium, polyacrylic acid-carboxymethylcellulose lithium copolymer, polybutyric acid-carboxymethylcellulose lithium copolymer One or a combination of polymethacrylic acid-lithium carboxymethyl cellulose copolymer.

It should be pointed out that traditional binders, such as styrene-butadiene rubber (containing carboxyl groups), although they have relatively strong interaction with current collectors and have good toughness, do not significantly promote the transmission of electrolyte. Especially when it is applied to a high-pressure anode, the rate and low-temperature performance are poor; another example is styrene-acrylate polymer, although it significantly promotes the transmission of electrolyte and has excellent low-temperature performance, but the adhesive force Poor, with poor deformation resistance, the pole piece is easy to swell, and the cycle expansion at room temperature and high temperature is large.

The accelerated mass transfer component I contains both rigid segments and mass transfer functional segments. On the one hand, the rigid segment with the above-mentioned styrene:olefin molar ratio makes the accelerated mass transfer component I have sufficient stiffness and good toughness. , which can suppress the violent expansion of the volume of the negative active material; on the other hand, the mass transfer functional chain segment with the above content has a certain polarity and is well wetted with the electrolyte, which can accelerate the transmission of lithium ions and prevent the lithium evolution reaction. occurrence, improve the capacity retention rate and reduce the thickness expansion rate; in addition, when the accelerating mass transfer chain segment contains removable lithium, the rate and cycle performance of the battery core can be further improved.

The polymerized monomer of olefin is butadiene, propylene, or butene.

The mass transfer functional segment includes an oxygen-containing mass transfer polymer segment.

The polymerized monomer of the oxygen-containing mass transfer polymer segment is one or a combination of acrylate monomers and lithium acrylate monomers, and the above components are used to improve electrolyte infiltration and ion transmission kinetics.

Wherein, the acrylic acid ester monomer is one or a combination of acrylate, crotonic acid ester, methacrylate or derivatives of the above monomers; the acrylic acid lithium monomer is lithium acrylate, butyl acrylate. Lithium acrylate, lithium methacrylate, lithium acrylate-lithium propionate, lithium crotonic acid-lithium propionate, lithium methacrylate-propionate, lithium phenyl acrylate, lithium phenyl propionate crotose, phenylpropyl methacrylate Lithium acid or one or a combination of derivatives of the above monomers. Lithium enoate monomers contain free lithium, which is beneficial to lithium ion transport.

Wherein, the polymerized monomer of the oxygen-containing mass transfer polymer segment may also include substructural segments containing lone pairs of electrons, such as polyethylene glycol or polyethyleneimine.

The medium particle size (D50) range of the accelerated mass transfer component I is 100-250 nm, ensuring that it has sufficient contact points with the negative active material and current collector.

Accelerated mass transfer component II is carboxymethyl cellulose lithium, polyacrylic acid-carboxymethyl cellulose lithium copolymer, polybutyric acid-carboxymethyl cellulose lithium copolymer, polymethacrylic acid-carboxymethyl cellulose lithium copolymer One or a combination of copolymers. The accelerated mass transfer component II itself contains freely migrating lithium ions, which promotes the transport of lithium ions.

This application also includes an application of the extremely accelerated mass transfer material, which is applied to negative electrode powder;

The negative electrode powder includes a negative electrode active material and a binder including the accelerating mass transfer component I in the negative electrode accelerating mass transfer material;

Or the negative electrode powder includes a negative electrode active material and a binder including the accelerated mass transfer component II in the negative electrode accelerated mass transfer material;

Or the negative electrode powder includes a negative electrode active material, a binder including the mass transfer accelerating component I and the mass transfer accelerating component II in the negative electrode accelerating mass transfer material;

Or the negative electrode powder includes a negative electrode active material, a binder including the mass transfer accelerating component I and the mass transfer accelerating component II in the negative electrode accelerating mass transfer material, and a conductive agent;

The sum of the mass fractions of the accelerated mass transfer component I and the accelerated mass transfer component II in the negative electrode powder layer is 0.5-3.5%.

In one form of this application, the mass proportion of mass transfer accelerating component I in the negative electrode powder layer is 0.7-1.3%; the mass proportion of mass transfer accelerating mass transfer component II in the negative electrode powder layer is 0.5-1.0%.

This application does not limit the negative active material as long as it meets the purpose of this application. The negative active material may include, but is not limited to, graphite, silicon, silicon oxygen, prelithiated silicon oxygen, silicon carbon, and prelithiated silicon carbon. , tin, phosphorus, oxides, prelithiated oxides, sulfides, prelithiated sulfides and other materials. The negative active material must meet the processing requirements of high-pressure compacted pole pieces. The surface of the rolled pole pieces is flat and smooth, without wrinkles or overpressure, and the negative electrode material will not be broken.

This application does not limit whether a conductive agent is added to the negative electrode, as long as it meets the purpose of this application. The conductive agent can include one or a combination of conductive carbon black and one-dimensional carbon nanomaterials. One-dimensional carbon nanomaterials include multi-walled carbon nanotubes, single-walled carbon nanotubes, carbon nanofibers, etc., which can form a long-range continuous conductive network, reduce ohmic voltage drop, and improve the voltage platform; or they can be used with high-capacity negative electrodes such as silicon and tin. , enhance the continuity of the conductive network.

This application also includes a negative electrode, including a negative electrode current collector and the negative electrode powder. This application does not have special requirements for the negative electrode current collector, as long as it meets the purpose of this application, it can include but is not limited to copper foil, coated copper foil, carbon-coated copper foil, lithium-plated copper foil, alloy foil, perforated foil, Foam metal, etc.

In this application, there are no special restrictions on the negative electrode slurry preparation, electrode processing, etc., as long as they meet the purpose of this application. The rolling process involved in this application can be a single rolling process to reach the specified compaction density, or it can be two or more times of rolling to reach the specified compaction density. It is necessary to ensure that the pole pieces do not over-pressure.

The application also includes an electrochemical device, including a positive electrode, the negative electrode, a porous separator, and an electrolyte.

The electrochemical device of this application has no special limitations on the positive electrode piece of the positive electrode, as long as it meets the purpose of this application. The positive electrode piece includes a positive electrode powder layer. The positive electrode powder layer includes positive electrode active materials, and the positive electrode active materials include but are not limited to one or more of lithium-transition metal oxides, lithium-transition metal phosphates, lithium-fluorinated transition metal phosphates, etc.; among the above materials, A "transition metal" can be one transition metal element or two or more transition metal elements. The positive electrode powder layer may also include a positive electrode binder. The positive electrode binder includes but is not limited to one or more types of polyvinylidene fluoride, polyacrylic acid, lithium polyacrylate, and the like. The positive electrode powder layer may also include a conductive agent for the positive electrode. The conductive agent for the positive electrode includes but is not limited to one or more types of carbon black, carbon tube, graphene, and carbon fiber.

In this application, the positive electrode sheet can also include a positive current collector. This application does not place special restrictions on the positive current collector, which only needs to meet the requirements of this application; the positive current collector can be but is not limited to aluminum foil, coated aluminum foil, carbon-coated aluminum foil, Alloy foil, foam metal, etc.

The electrochemical device of the present application may also include a porous separator that isolates the positive and negative electrodes and conducts the electrolyte. The electrochemical device of the present application has no special limitations on the separator, as long as it meets the purpose of the present application. The porous separator can be, but is not limited to, PE separator, PP separator, multi-layer composite separator (such as PP/PE/PP), rubber-coated separator, rubber-coated ceramic separator, aramid separator, non-woven separator, etc.

The electrochemical device of this application also includes an electrolyte. The electrolyte can be in a liquid state, a semi-gel state, a gel state, etc. This application does not impose special restrictions on the electrolyte solution, as long as it meets the purpose of this application.

The electrochemical device of this application also includes a collector ear and a packaging shell. This application does not impose special restrictions on this, as long as it meets the purpose of this application.

The structure of the electrochemical device of the present application can be, but is not limited to, any of winding, lamination, etc. The type of electrochemical device is not limited and may be, but is not limited to, primary batteries, secondary batteries, supercapacitors, ion-supercapacitor hybrid devices, etc. The manufacturing process of the electrochemical device of this application is well known in the industry and is not particularly limited.

The present application also includes an electronic device including the electrochemical device described above. This application does not specifically limit electronic equipment, which may include but is not limited to laptop computers, wearable devices, mobile phones, game consoles, cameras, televisions, recording equipment, video equipment, lighting equipment, power tools, energy storage modules, automobiles , unmanned aircraft, etc.

Compared with the prior art, the beneficial effects of the present invention are:

The accelerating mass transfer component I of the present application can simultaneously enhance the charge and discharge capacity and control the cyclic expansion of high temperature, medium temperature and low temperature. The main function of the accelerating mass transfer component II is to enhance the charging capacity and control the low temperature cyclic expansion; preferably, when accelerating mass transfer The mass material group contains both accelerated mass transfer components I and accelerated mass transfer components II, which can significantly improve the comprehensive performance of electrochemical devices such as cycle, rate, and low temperature. The accelerating mass transfer component I, accelerating mass transfer component II and one-dimensional carbon nanomaterials are simultaneously applied to the high-pressure anode to build an effective ion and electronic conductive network, further reducing the impedance of electrochemical reactions and mass transfer, and improving power. Learn to reduce the occurrence of side effects.

In this application, if the expansion of high temperature (generally refers to the temperature range 40~60°C), medium temperature (generally refers to the temperature range 15~30°C), and low temperature (generally refers to the temperature range -30~10°C) is simultaneously improved, it must at least include Mass transfer accelerating component I, if it only improves expansion at medium and low temperatures, may contain at least one of mass transfer accelerating component I and mass transfer accelerating component II. If you only need to improve the cycle capacity retention rate, it is enough to include at least one of the mass transfer accelerating component I and the mass transfer accelerating component II.

This application also proposes a negative electrode, an electrochemical device and an electronic device including the negative electrode. The negative electrode includes a negative electrode accelerating mass transfer material. Each component is flexibly matched. The accelerating mass transfer material can improve material transmission efficiency and prevent lithium precipitation. Improve capacity retention. In summary, the technology of this application can significantly improve the low temperature, rate, cycle and other performance of high-energy electrochemical devices.

Description of the drawings

Figure 1 is a schematic diagram of the principle.

Figure 2 Comparison of the 0°C cycle capacity retention rate between the example and the blank control group (the capacity retention rate is based on the normal temperature nominal capacity).

Figure 3 is a comparison chart of the thickness expansion rates after the 0°C cycle between the Example and the blank control group.

Figure 4 is a comparison chart of the thickness expansion rates after the 45°C cycle between the embodiment and the blank control group.

Detailed ways

In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below in conjunction with the accompanying drawings and best embodiments.

It should be noted that the electrochemical devices used in the following examples are lithium ion secondary batteries, but the electrochemical devices involved in this application are not limited to lithium ion secondary batteries. In order to intuitively illustrate the function and effect of this technology, the following three tests were performed on the blank control group and example samples.

(1)25℃ DCIR test:

Let I ₀ be the current corresponding to 0.1C, and I ₁ be the current corresponding to 1C.

Fresh batteries that have not been tested for electrical performance are placed in a constant temperature box at 25°C for more than 1 hour, discharged to 3V with a constant current of I ₀ ; left to stand for 10 minutes; charged with a constant current of I ₀ for 5 hours (the final instantaneous voltage is recorded as U ₀ ), and then charge with a constant current I ₁ for 1 s (the final instantaneous voltage is recorded as U ₁ ).

25℃ DCIR＝(U ₁ -U ₀ )/(I ₁ -I ₀ )

(2)0℃ DCIR test:

Let I ₀₀ be the current corresponding to 0.1C, and I ₀₁ be the current corresponding to 0.5C.

Fresh batteries that have not been tested for electrical performance are placed in a constant temperature box at 0°C for more than 2 hours, discharged to 3V with a constant current of I ₀₀ ; left to stand for 10 minutes; charged with a constant current of I ₀₀ for 5 hours (the final instantaneous voltage is recorded as U ₀₀ ), and then charge with constant current I ₀₁ for 0.5s (the end instant voltage is recorded as U ₀₁ ).

0°C DCIR=(U ₀₁ -U ₀₀ )/(I ₀₁ -I ₀₀ );

(3)0℃ cycle test:

Record the cell thickness T ₀ before testing.

This test is carried out in a 0°C thermostat. Before running the cycle test, the battery core needs to be left in the thermostat for more than 3 hours.

Charge to 4.48V at a constant current of 0.33C, charge to 0.05C at a constant voltage of 4.48V, and leave for 10 minutes; discharge at a constant current of 0.5C to 3V, and leave for 10 minutes. Repeat the above test process until the number of cycles reaches 50, charge to 4.48V at a constant current of 0.33C, charge to 0.05C at a constant voltage of 4.48V, take out the battery and let it stand at room temperature for more than 1 hour, and record the thickness of the battery T ₁ .

Thickness expansion rate=(T ₁ /T ₀ -1)*100%

(4) 45℃ cycle test:

Record the cell thickness T ₀ before testing.

This test is carried out in a 45°C thermostat. Before running the cycle test, the battery core needs to be left in the thermostat for more than 1 hour.

Charge at 0.8C constant current to 4.48V, charge at 4.48V constant voltage to 0.05C, and let it sit for 10 minutes; discharge at 0.5C constant current to 3V, and let it stand for 10 minutes. Repeat the above test process until the number of cycles reaches 400, charge to 4.48V at a constant current of 0.8C, charge to 0.05C at a constant voltage of 4.48V, take out the battery and let it stand at room temperature for more than 1 hour, and record the thickness of the battery T ₁ .

Thickness expansion rate=(T ₁ /T ₀ -1)*100%

Blank control group:

Negative electrode production: Mix artificial graphite, acetylene black, sodium carboxymethylcellulose, and styrene-butadiene rubber according to the mass ratio of 97.5:0.4:0.8:1.3, add deionized water to adjust the viscosity, and then apply and roll (compacted density 1.75 g/cm ³ ), shearing and other processes to complete the production of pole pieces. Positive electrode production: Mix lithium cobalt oxide, conductive carbon black, and polyvinylidene fluoride at a mass ratio of 98:1:1, add NMP to adjust the viscosity, and complete the production of the electrode piece through processes such as coating, rolling, and shearing. Battery core production: Use the above-mentioned negative electrode and positive electrode to make a wound battery core. After the battery core is chemically separated and sorted, the electrical performance test is performed.

Example 1 except "mix artificial graphite, acetylene black, sodium carboxymethylcellulose, styrene-butadiene rubber, and styrene-butadiene-isobutylene ester in a mass ratio of 97.5:0.4:0.8:0.6:0.7". Same as the blank control group.

Example 2: Except for "mixing artificial graphite, acetylene black, sodium carboxymethyl cellulose, and styrene-butadiene-isobutylene ester according to the mass ratio of 97.5:0.4:0.8:1.3", everything else is the same as the blank control group .

Example 3: Except for "mixing artificial graphite, acetylene black, sodium carboxymethylcellulose, and styrene-butadiene-propylene ester according to the mass ratio of 97.5:0.4:0.8:1.3", everything else is the same as the blank control group .

Example 4: Except for "mixing artificial graphite, acetylene black, sodium carboxymethyl cellulose, and styrene-propylene-isobutylene ester in a mass ratio of 97.5:0.4:0.8:1.3", everything else was the same as the blank control group.

Example 5: Except for "mixing artificial graphite, acetylene black, sodium carboxymethylcellulose, and styrene-butadiene-lithium acrylate according to a mass ratio of 97.5:0.4:0.8:1.3", everything else is the same as the blank control group .

Example 6: Except for "mixing artificial graphite, acetylene black, sodium carboxymethyl cellulose, styrene-butadiene-methacrylate-acrylonitrile according to the mass ratio of 97.5:0.4:0.8:1.3", all others were mixed with The blank control group was the same.

Example 7: Except "mix artificial graphite, acetylene black, sodium carboxymethyl cellulose, styrene-butadiene-isobutylene (n-glycol) lithium diacrylate according to the mass ratio of 97.5:0.4:0.8:1.3" Except for this, everything else was the same as the blank control group.

Example 8: Except for "mixing artificial graphite, acetylene black, sodium carboxymethylcellulose, polyacrylic acid-lithium carboxymethylcellulose, and styrene-butadiene rubber in a mass ratio of 97.5:0.4:0.3:0.5:1.3", other All were the same as the blank control group.

Example 9: Except for "mixing artificial graphite, acetylene black, polyacrylic acid-lithium carboxymethylcellulose, and styrene-butadiene rubber in a mass ratio of 97.5:0.4:0.8:1.3", everything else was the same as the blank control group.

Example 10: Except for "mixing artificial graphite, acetylene black, polyacrylic acid-lithium carboxymethylcellulose, and styrene-butadiene rubber in a mass ratio of 97.5:0.4:1.0:1.1", everything else was the same as the blank control group.

Example 11: Except for "mixing artificial graphite, acetylene black, polyacrylic acid-lithium carboxymethyl cellulose, and styrene-butadiene-isobutylene ester according to the mass ratio of 97.5:0.4:0.8:1.3", the others were all with the blank The control group was the same.

Example 12: In addition to "mixing artificial graphite, acetylene black, polyacrylic acid-lithium carboxymethyl cellulose, styrene-butadiene-isobutylene ester, and carbon fiber according to the mass ratio of 97.5:0.3:0.8:1.3:0.1", Others were the same as the blank control group.

The differences between the blank control and each example are shown in Table 1. For the accelerated mass transfer component I in Examples 1-7, 11 and 12, the molar ratio of styrene segment: olefin segment is approximately equal to 4.0, and the mass transfer functional segment: styrene segment and olefin segment material The molar ratio of the sum of the quantities is approximately equal to 0.11; the medium particle diameter D ₅₀ of the accelerating component I is 135 nm.

Table 1

The 25°C and 0°C DCIR of the blank control and various examples are shown in Table 2.

Table 2

plan	25℃ DCIR(mΩ)	0℃DCIR(mΩ)
Blank control	54.8	152.8
Example 1	53.5	139.6
Example 2	53.0	131.1
Example 3	53.1	131.4
Example 4	53.2	131.0
Example 5	52.8	129.4
Example 6	53.1	131.8
Example 7	52.6	128.9
Example 8	53.7	138.3
Example 9	53.1	130.8
Example 10	53.3	130.5
Example 11	52.0	122.7
Example 12	51.5	121.0

The lower the temperature, the more difficult it is to transport lithium ions, so the 0°C DCIR for any given sample is significantly greater than the 25°C DCIR.

It can be seen from Table 2 that before and after the introduction of accelerated mass transfer materials, compared with the decrease in DCIR at 25°C, the decrease in DCIR at 0°C is more significant; indicating that the lower the temperature, the positive effect of accelerated mass transfer materials on lithium ion transmission The more significant it is, the easier it is to observe the difference from the blank control.

Comparing the blank control sample, Examples 1 and 2, it can be seen that as the proportion of accelerating mass transfer component I increases, the 0°C DCIR gradually decreases, indicating that accelerating mass transfer component I can improve the material transfer rate.

Comparing the blank control sample, Examples 8, 9 and 10, it can be seen that as the proportion of accelerated mass transfer component II (polyacrylic acid-lithium carboxymethyl cellulose) increases, the 0°C DCIR gradually decreases, indicating that the accelerated mass transfer component Sub-II can improve material transfer efficiency.

Comparing Examples 2, 3, 4, 5, 6 and 7, it can be seen that when the mass transfer functional segment in the accelerated mass transfer component I includes a polyethylene glycol segment, it helps to reduce the 0°C DCIR.

Comparing Examples 2, 9 and 11, it can be seen that having both the accelerated mass transfer component I and the accelerated mass transfer component II can further reduce the 0°C DCIR, reflecting the synergistic effect of the two components.

Comparing Examples 11 and 12, it can be seen that having the accelerating mass transfer component I, the accelerating mass transfer component II and the one-dimensional carbon nanomaterial (conductive agent) at the same time can further reduce the 0°C DCIR, and it can be seen that a smooth ion and electron network can be constructed. It plays a very important role in reducing system polarization.

Taking the 0°C cycle as an example to illustrate the role of accelerating mass transfer material groups. Figure 1 is a schematic diagram of the principle; as shown in Figures 2 and 3, the blank control sample uses a traditional binder, which has the worst kinetics, the cycle capacity retention rate continues to decay, the thickness after cycles expands by more than 9%, and the dissection found that the battery core analyzed Lithium; the low-temperature cycle performance of sample A (Example 2), sample B (Example 9), and sample C (Example 11) is significantly better than the blank control sample, which shows that the accelerated mass transfer material group can effectively increase the lithium ion transfer rate , inhibiting the occurrence of lithium evolution and improving the low-temperature cycle performance of electrochemical devices containing the above-mentioned high-compact negative electrode. The low-temperature cycle performance of sample C is better than that of sample A and sample B. The accelerated mass transfer component I and the accelerated mass transfer component II have a synergistic effect, and their simultaneous application can further enhance the improvement effect.

Taking the 45°C cycle as an example, Figure 4 is a comparison chart of the thickness expansion rates after the 45°C cycle of the embodiment and the blank control group. Explain the difference in the application effects of accelerated mass transfer component I and accelerated mass transfer component II. The cyclic expansion rate of sample A and sample C is less than that of the blank control, and the thickness expansion rate of sample B is similar to that of the blank control. This shows that the accelerated mass transfer component I has the effect of improving high temperature cycle expansion.

It should be noted that accelerating mass transfer materials improves the rate and cycle performance of electrochemical devices at different temperatures; among them, Examples 2-7 and 11-12 are better than the blank in terms of thickness control at high rate cycles at room temperature. Control sample, content omitted.

The above are only preferred embodiments of the present invention. It should be noted that those skilled in the art can make several improvements and modifications without departing from the principles of the present invention. These improvements and modifications can also be made. should be regarded as the protection scope of the present invention.

Claims (9)

1. A material for accelerating mass transfer and improving expansion of the negative electrode, which is characterized in that it includes at least one component of a mass transfer accelerating component I and a mass transfer accelerating component II;

   The accelerated mass transfer component I is a multi-component copolymer; the multi-component copolymer is formed by copolymerization of styrene, olefin and mass transfer functional monomer; wherein the molar ratio of styrene:olefin is ≥3.0; the mass transfer functional monomer : the molar ratio of the sum of the amounts of styrene and olefins is 0.05-0.25; the mass transfer functional monomer is one or a combination of olefinic acid ester monomers and lithium olefinic acid monomers;

   The accelerated mass transfer component II is a polymer, and the polymer is carboxymethylcellulose lithium, polyacrylic acid-carboxymethylcellulose lithium copolymer, polybutyric acid-carboxymethylcellulose lithium copolymer One or a combination of polymethacrylic acid-lithium carboxymethyl cellulose copolymer.
2. The material for accelerating mass transfer and improving expansion of the negative electrode according to claim 1, characterized in that the acrylic acid ester monomer is an acrylic acid ester, a crotonic acid ester, a methacrylic acid ester or a derivative of the above monomer. species or combination.
3. The material for accelerating mass transfer and improving expansion of the negative electrode according to claim 1, characterized in that the lithium acrylate monomer is lithium acrylate, lithium crotonate, lithium methacrylate, acrylic acid-lithium propionate, butylene One or a combination of acid-lithium propionate, lithium methacrylate-lithium propionate, lithium phenyl acrylate, lithium crotonic acid phenylpropionate, lithium methacrylate phenylpropionate or derivatives of the above monomers.
4. The anode material for accelerating mass transfer and improving expansion according to claim 1, characterized in that the polymerized monomer of the oxygen-containing mass transfer polymer segment may also include substructure segments containing lone pairs of electrons; The substructural fragment mentioned above is polyethylene glycol or polyethyleneimine.
5. The anode material for accelerating mass transfer and improving expansion according to claim 1, characterized in that the medium particle size (D ₅₀ ) of the mass transfer accelerating component I ranges from 100 to 250 nm.
6. An application of extremely accelerated mass transfer materials and improved expansion according to any one of claims 1 to 5, characterized in that it is applied to negative electrode powder;

   The negative electrode powder includes a negative electrode active material and a binder including the accelerating mass transfer component I in the negative electrode accelerating mass transfer material;

   Or the negative electrode powder includes a negative electrode active material and a binder including the accelerated mass transfer component II in the negative electrode accelerated mass transfer material;

   Or the negative electrode powder includes a negative electrode active material, a binder including the mass transfer accelerating component I and the mass transfer accelerating component II in the negative electrode accelerating mass transfer material;

   Or the negative electrode powder includes a negative electrode active material, a binder including the mass transfer accelerating component I and the mass transfer accelerating component II in the negative electrode accelerating mass transfer material, and a conductive agent;
7. A material and application for accelerating mass transfer and improving expansion of the negative electrode according to any one of claims 1 to 6, characterized in that it is applied to negative electrode powder; the mass proportion of the accelerated mass transfer component I in the negative electrode powder It is 0.7-1.3%; the mass proportion of accelerated mass transfer component II in the negative electrode powder is 0.5-1.0%.
8. A negative electrode, characterized by comprising a negative electrode current collector and the negative electrode powder according to claim 7.
9. An electrochemical device, characterized by comprising a positive electrode, the negative electrode according to claim 8, a porous separator, and an electrolyte.

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