Negative electrode sheet and preparation method therefor, and lithium battery

Abstract

The present disclosure relates to the technical field of lithium batteries. Disclosed are a negative electrode sheet and a preparation method therefor, and a lithium battery. The negative electrode sheet comprises a current collector and an active layer arranged on the surface of the current collector. The components of the active layer comprise a negative electrode active material, a conductive agent, a binder, and an additive. The additive is a metal oxide having an inverse opal structure. The metal oxide having an inverse opal structure is added to the active layer of the negative electrode sheet, and the metal oxide can impart a special pore structure to the negative electrode sheet, thereby improving the porosity of the negative electrode sheet, improving the wettability of an electrolyte to the negative electrode sheet, and improving the liquid retention amount of the negative electrode sheet.

Description

Negative electrode sheet and its preparation method and lithium battery

[0001] Cross-references to related applications

[0002] This disclosure claims priority to Chinese Patent Application No. 2024115503702, filed on November 1, 2024, entitled “Negative Electrode Sheet and Preparation Method Thereof and Lithium Battery”, the entire contents of which are incorporated herein by reference. Technical Field

[0003] This disclosure relates to the field of lithium battery technology, and more specifically, to negative electrode sheets, their preparation methods, and lithium batteries. Background Technology

[0004] Lithium-ion rechargeable battery technology is developing rapidly and its applications are becoming increasingly widespread. Currently, the market demands higher performance from lithium-ion batteries, requiring them to achieve both high energy density and high rate capability. For conventional graphite and silicon anode lithium-ion batteries, increasing the coating amount and compaction density of the electrode to improve energy density can lead to a significant increase in electrode tortuosity due to the solid, non-porous structure of these materials. This reduces electrolyte wetting and ion transport rate, resulting in decreased rate capability and a loss of battery power performance. To simultaneously achieve high energy density and high rate capability in lithium-ion batteries, it is essential to increase the specific surface area of ​​the anode material, improve the porosity of the anode electrode, and optimize the microporous structure of the electrode to enhance energy density while maintaining the lithium-ion transport rate.

[0005] Currently, the main ways to improve the porosity of the negative electrode sheet and enhance electrolyte wettability include adding pore-forming agents and laser drilling. However, adding pore-forming agents has limitations because these agents do not have lithium storage capacity, and their residue can increase the proportion of impurities, affecting the performance and energy density of lithium batteries. Laser drilling is costly and involves additional drilling steps.

[0006] In view of this, this disclosure is hereby made. Summary of the Invention

[0007] The purpose of this disclosure is to provide a negative electrode sheet, a method for preparing the same, and a lithium battery.

[0008] This disclosure is implemented as follows:

[0009] In a first aspect, this disclosure provides a negative electrode sheet, including a current collector and an active layer disposed on the surface of the current collector;

[0010] The active layer consists of negative electrode active material, conductive agent, binder and additives;

[0011] The additive is a metal oxide with an inverse opal structure.

[0012] In an optional implementation, the active layer has a multilayer structure;

[0013] Along the direction away from the current collector, the additive content of each layer in the multilayer active layer gradually increases.

[0014] In an optional embodiment, the additive content of each layer in the multilayer structure of the active layer satisfies the following formula: The active layer is defined as the layer closest to the current collector, where a1 represents the percentage of additives in the first layer relative to the total mass of the active layer. n The percentage of the additive in the nth layer relative to the total active mass, where n is the current layer number. 总 n is the total number of active layers. 总 ≥2, where p is the mass percentage of the additive in the entire active layer, 0.1% ≤ p ≤ 50%;

[0015] When n 总 ≥2, 0≤a1<p / n 总 a n Starting from the current collector side, the layer gradually increases towards the outermost layer.

[0016] In an optional implementation, the metal oxide satisfies:

[0017] The D50 of the metal oxide is 1–40 μm; and / or the internal pore size of the metal oxide particles is 0.05–20 μm, and the internal pore volume accounts for 50–90% of the particle volume.

[0018] In an optional embodiment, the metal oxide is selected from at least one of titanium dioxide, tin dioxide, and germanium dioxide.

[0019] In an optional embodiment, the active layer comprises, by mass percentage, 43-97.9% negative electrode active material, 0.5-3% conductive agent, 1-2.5% binder, and 0.1-50% additives.

[0020] In an optional embodiment, the active layer further comprises 0.5 to 1.5% dispersant by mass percentage;

[0021] The dispersant is selected from at least one of sodium carboxymethyl cellulose, lithium carboxymethyl cellulose, and sodium carboxyethyl cellulose.

[0022] In an optional implementation, at least one of the following features (1)-(4) is also included:

[0023] (1) The conductive agent is selected from at least one of carbon black, graphite sheets, carbon nanotubes and graphene;

[0024] (2) The adhesive is selected from at least one of styrene-butadiene rubber, sodium polyacrylate, sodium alginate and polyacrylonitrile;

[0025] (3) The negative electrode active material is selected from at least one of graphite, hard carbon, soft carbon, lithium titanate and mesophase carbon microspheres;

[0026] (4) An active layer is provided on both opposite sides of the current collector.

[0027] Secondly, this disclosure provides a method for preparing a negative electrode sheet, which is used to prepare a negative electrode sheet as described in any of the foregoing embodiments, comprising coating a negative electrode slurry containing various components of the active layer onto the surface of a current collector, followed by drying and cold pressing.

[0028] Thirdly, this disclosure provides a lithium battery, including a negative electrode as described in any of the foregoing embodiments.

[0029] This disclosure has the following beneficial effects:

[0030] The negative electrode provided in this embodiment incorporates an inverse opal-structured metal oxide in its active layer. This metal oxide imparts a unique pore structure to the negative electrode, increasing its porosity, improving electrolyte wettability, and enhancing electrolyte retention. Furthermore, when a lithium-storage metal oxide is selected as an additive, the lithium-storage capacity of the negative electrode is not reduced. Therefore, adding an inverse opal-structured metal oxide to the active layer of the negative electrode increases its rate performance, reduces internal resistance, and maintains the lithium-ion transport rate. This negative electrode addresses the problem of reduced electrolyte wettability and ion transport rate, which can lead to decreased rate performance and power loss in lithium-ion batteries when increasing the coating amount and material compaction density to improve energy density. Attached Figure Description

[0031] To more clearly illustrate the technical solutions of the embodiments of this disclosure, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of this disclosure and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0032] Figure 1 is a schematic diagram of the simulated structure of the active layer of the negative electrode sheet prepared in Example 2;

[0033] Figure 2 is a schematic diagram of the simulated structure of the active layer of the negative electrode sheet prepared in Example 3.

[0034] Icons: 1- Inverse opal porous layer; 2- Graphite layer; 3- Current collector; 4- Mixed porous layer of inverse opal and graphite. Detailed Implementation

[0035] To make the objectives, technical solutions, and advantages of the embodiments of this disclosure clearer, the technical solutions in the embodiments of this disclosure will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0036] The features and performance of this disclosure will be further described in detail below with reference to embodiments.

[0037] An embodiment of this disclosure provides a negative electrode sheet, including a current collector and an active layer disposed on the surface of the current collector;

[0038] The active layer consists of negative electrode active material, conductive agent, binder and additives;

[0039] The additive is a metal oxide with an inverse opal structure.

[0040] The negative electrode provided in this embodiment incorporates an inverse opal-structured metal oxide in its active layer. This metal oxide imparts a unique pore structure to the negative electrode, increasing its porosity, electrolyte wettability, and electrolyte retention. Therefore, by adding an inverse opal-structured metal oxide to the active layer, the rate performance of the negative electrode can be increased, the internal resistance of the cell reduced, and the lithium-ion transport rate maintained. This negative electrode addresses the problem of reduced electrolyte wettability and ion transport rate, leading to decreased rate performance and power loss, that occurs when increasing the coating amount and material compaction density of lithium-ion batteries to improve energy density.

[0041] It should be noted that the preparation of metal oxides with an inverse opal structure is already existing technology, so it will not be elaborated on in this case.

[0042] Optionally, the active layer can be disposed on either side or on both opposite sides of the current collector.

[0043] Optionally, to better improve the wettability and liquid retention of the negative electrode, the active layer has a multi-layer structure; along the direction away from the current collector, the additive content of each layer in the multi-layer active layer gradually increases, and the additive is evenly distributed in each active layer.

[0044] Furthermore, to ensure better high-rate performance of the negative electrode, the additive content of each layer in the multilayer structure of the active layer satisfies the following formula: The active layer is defined as the layer closest to the current collector, where a1 represents the percentage of additives in the first layer relative to the total mass of the active layer. nThe percentage of the additive in the nth layer relative to the total active mass, where n is the current layer number. 总 n is the total number of active layers. 总 ≥2, where p is the mass percentage of the additive in the entire active layer, 0.1% ≤ p ≤ 50%;

[0045] When n 总 ≥2, 0≤a1<p / n 总 a n Starting from the current collector side, the layer gradually increases towards the outermost layer.

[0046] Preferably, the metal oxide is a metal oxide with lithium storage capacity. When the added metal oxide is a metal oxide with lithium storage capacity, it can ensure that the negative electrode has better lithium storage capacity and better energy density.

[0047] Optionally, to further ensure the electrochemical performance of the negative electrode, the D50 of the metal oxide in the active layer is 1 to 40 μm. Within this range, D50 can not only improve the porosity of the negative electrode and the wettability of the electrolyte to the negative electrode, but also enable the negative electrode to have a higher energy density. When D50 is less than 1 μm, the particle size is too small and cannot improve the porosity of the negative electrode. When D50 is greater than 40 μm, it will reduce the compaction density of the negative electrode, thereby reducing the energy density of the lithium-ion battery. Preferably, D50 is 10 μm, 20 μm, or 30 μm.

[0048] Similarly, further, the internal pore size of the metal oxide particles is 0.05–20 μm. Within this range, not only can the porosity of the negative electrode be improved and the wettability of the electrolyte to the negative electrode be enhanced, but the negative electrode can also have a higher energy density. Preferably, the internal pore size is 1 μm, 3 μm, 5 μm, 7 μm, 9 μm, 11 μm, 13 μm, 15 μm, 17 μm, or 19 μm. When the internal pore size of the metal oxide particles is less than 0.05 μm, the particle pore size is too small and cannot effectively improve the porosity of the negative electrode. When the internal pore size of the metal oxide particles is greater than 20 μm, the compaction density of the negative electrode will be reduced, thereby reducing the energy density of the lithium-ion battery.

[0049] Similarly, further, the internal pore volume accounts for 50-90% of the particle volume. Within this range, not only can the porosity of the negative electrode be improved and the wettability of the electrolyte to the negative electrode be enhanced, but the negative electrode can also have a higher energy density. Preferably, the internal pore volume accounts for 60%, 70%, and 80% of the particle volume. When the internal pore volume accounts for less than 50% of the particle volume, the porosity of the negative electrode cannot be effectively improved. When the internal pore volume accounts for more than 90% of the particle volume, the compaction density of the negative electrode will be reduced, thereby reducing the energy density of the lithium-ion battery.

[0050] Optionally, the metal oxide is selected from at least one of titanium dioxide, tin dioxide, and germanium dioxide.

[0051] Optionally, the active layer comprises, by weight percentage, 43-97.9% negative electrode active material, 0.5-3% conductive agent, 1-2.5% binder, and 0.1-50% additives.

[0052] Optionally, to ensure better performance of the negative electrode, the coating density of the active layer is 40–400 g / m². 2 .

[0053] Optionally, the negative electrode active material is selected from at least one of graphite, hard carbon, soft carbon, lithium titanate, and mesophase carbon microspheres.

[0054] Optionally, the conductive agent is selected from at least one of carbon black, graphite sheets, carbon nanotubes, and graphene.

[0055] Optionally, the adhesive is selected from at least one of styrene-butadiene rubber, sodium polyacrylate, sodium alginate, and polyacrylonitrile.

[0056] Optionally, the active layer may also include 0.5 to 1.5% dispersant by mass percentage.

[0057] Optionally, the dispersant is selected from at least one of sodium carboxymethyl cellulose, lithium carboxymethyl cellulose, and sodium carboxyethyl cellulose.

[0058] The method for preparing the negative electrode sheet provided in this disclosure includes coating a negative electrode slurry containing various components of the active layer onto the surface of a current collector, followed by drying and cold pressing.

[0059] Specifically, if the active layer is a single-layer structure, the negative electrode slurry is coated with one layer and then dried and cold-pressed; if the active layer is a multi-layer structure, the negative electrode slurry corresponding to different layers is coated sequentially and then dried and cold-pressed.

[0060] The lithium battery provided in this disclosure includes a negative electrode sheet provided in this disclosure. Because the battery includes the negative electrode sheet provided in this disclosure, it has superior electrochemical performance.

[0061] The present disclosure will be further described below with reference to several embodiments and comparative examples.

[0062] Example 1

[0063] A negative electrode sheet is prepared by the following method:

[0064] Graphite, inverse opal-structured titanium dioxide, conductive carbon black, styrene-butadiene rubber (SBR) binder, and sodium carboxymethyl cellulose (CMC) dispersant were mixed with water in a mass ratio of 47.5%:47.5%:2%:1.8%:1.2% to obtain a negative electrode slurry with a solid content of 45%. The titanium dioxide particles had a D50 of 20 μm, an internal pore size of 1–5 μm, and a pore volume ratio of 70%.

[0065] The negative electrode slurry is coated on both sides of the current collector, dried, cold-pressed, and cut to obtain the negative electrode sheet, wherein the surface density of the active layer coating is 300 g / m². 2 .

[0066] Example 2

[0067] A composite negative electrode sheet is prepared by the following method:

[0068] Graphite, conductive carbon black, binder styrene-butadiene rubber, and dispersant sodium carboxymethyl cellulose were mixed with water in a mass ratio of 95%:2%:1.8%:1.2% to obtain a negative electrode slurry a with a solid content of 45%.

[0069] A negative electrode slurry b with a solid content of 45% was obtained by mixing titanium dioxide with an inverse opal structure, conductive carbon black, styrene-butadiene rubber as a binder, and sodium carboxymethyl cellulose as a dispersant in a mass ratio of 95%:2%:1.8%:1.2%. The titanium dioxide particles had a D50 of 20 μm, an internal pore size of 1–5 μm, and a pore volume ratio of 70%.

[0070] Slurry a is coated on both sides of the current collector, and slurry b is coated on slurry a. After drying, cold pressing, and cutting, the negative electrode sheet is obtained, wherein the surface density of the active layer coating is 300 g / m². 2 The first layer is 150g / m³ 2 The second layer is 150g / m³ 2 .

[0071] In the prepared negative electrode sheet, the titanium dioxide with an inverse opal structure is concentrated and dispersed on the side away from the current collector. The graphite, titanium dioxide, conductive agent, binder and dispersant in the negative electrode sheet are in the following mass ratios: 47.5%: 47.5%: 2%: 1.8%: 1.2%.

[0072] The structure of the obtained negative electrode sheet is shown in Figure 1. A graphite layer 2 and an inverse opal porous layer 1 are formed sequentially on the two opposite sides of the current collector 3.

[0073] Example 3

[0074] A composite negative electrode sheet is prepared by the following method:

[0075] Graphite, conductive agent carbon black, binder styrene-butadiene rubber, and dispersant sodium carboxymethyl cellulose were mixed with water in a mass ratio of 95%:2%:1.8%:1.2% to obtain a negative electrode slurry a with a solid content of 45%.

[0076] Graphite, inverse opal-structured titanium dioxide, conductive carbon black, binder styrene-butadiene rubber, and dispersant sodium carboxymethyl cellulose were mixed with water in a mass ratio of 47.5%:47.5%:2%:1.8%:1.2% to obtain a negative electrode slurry b with a solid content of 45%. The titanium dioxide particles had a D50 of 20 μm, an internal pore size of 1–5 μm, and a pore volume ratio of 70%.

[0077] Inverse opal-structured titanium dioxide, conductive carbon black, binder styrene-butadiene rubber, and dispersant sodium carboxymethyl cellulose were mixed with water in a mass ratio of 95%:2%:1.8%:1.2% to obtain a negative electrode slurry c with a solid content of 45%. The titanium dioxide particles had a diameter of 20 μm, an internal pore size of 1–5 μm, and a pore volume ratio of 70%.

[0078] The arrangement of the active layers satisfies the formula. n 总 =3, a1=0, p=47.5%; that is, the additive content of the first layer of the active layer is 0%, the content of the second layer is 15.83%, and the content of the third layer is 31.67%. Slurry a is coated on both sides of the current collector, slurry b is coated on slurry a, and slurry c is coated on slurry b. After drying, cold pressing, and cutting, the negative electrode sheet is obtained, wherein the surface density of the active layer coating is 300 g / m². 2 The first layer is 100g / m 2 The second layer is 100g / m 2 The third layer is 100g / m³ 2 .

[0079] In the prepared negative electrode sheet, the titanium dioxide with an inverse opal structure is dispersed in a gradient on the side away from the current collector. The graphite, titanium dioxide, conductive agent, binder and dispersant in the negative electrode sheet are in the following mass ratios: 47.5%: 47.5%: 2%: 1.8%: 1.2%.

[0080] The structure of the obtained negative electrode sheet is shown in Figure 2. A graphite layer 2 and a porous layer of inverse opal and graphite mixed are formed sequentially on the two opposite sides of the current collector 3.

[0081] Example 4

[0082] This embodiment is basically the same as embodiment 3, except that this embodiment does not satisfy the formula. The first layer of additives contains 15.83%, the second layer contains 31.67%, and the third layer contains 0%.

[0083] Prepare slurries a, b, and c as in Example 3. Coat slurry b on both sides of the current collector, coat slurry c on slurry b, and coat slurry a on slurry c. Dry, cold press, and cut to obtain the negative electrode sheet.

[0084] The titanium dioxide with an inverse opal structure in the prepared negative electrode sheet was not distributed according to the formula. The graphite, titanium dioxide, conductive agent, binder and dispersant in the negative electrode sheet were in the mass ratio of 47.5:47.5%:2%:1.8%:1.2%.

[0085] Example 5

[0086] This embodiment is basically the same as embodiment 2, except that the coating order of slurry a and slurry b is reversed.

[0087] Example 6

[0088] This embodiment is basically the same as Embodiment 2, except that the composition of slurry a is graphite: conductive agent carbon black: binder styrene-butadiene rubber: dispersant sodium carboxymethyl cellulose = 95%: 2%: 1.8%: 1.2%;

[0089] The components of slurry b are graphite: opal-structured titanium dioxide: conductive agent carbon black: binder styrene-butadiene rubber: dispersant sodium carboxymethyl cellulose in a mass ratio of 94.8%:0.2%:2%:1.8%:1.2%.

[0090] In the prepared negative electrode sheet, the titanium dioxide with an inverse opal structure is concentrated and dispersed on the side away from the current collector. The mass ratio of graphite, titanium dioxide, conductive agent, binder and dispersant in the negative electrode sheet is 94.9%:0.1%:2%:1.8%:1.2%, of which the content of the first layer additive is 0% and the content of the second layer is 0.1%.

[0091] Similarly, the surface density of the active layer coating is 300 g / m². 2 The first layer is 150g / m³ 2 The second layer is 150g / m³ 2 .

[0092] Example 7

[0093] This embodiment is basically the same as Embodiment 2, except that the composition of slurry a is graphite: conductive agent carbon black: binder styrene-butadiene rubber: dispersant sodium carboxymethyl cellulose = 95%: 2%: 1.8%: 1.2%;

[0094] The components of slurry b are graphite: opal-structured titanium dioxide: conductive agent carbon black: binder styrene-butadiene rubber: dispersant sodium carboxymethyl cellulose in a mass ratio of 75%:20%:2%:1.8%:1.2%.

[0095] In the prepared negative electrode sheet, the inverse opal structure of titanium dioxide is concentrated and dispersed on the side away from the current collector. The mass ratio of graphite, titanium dioxide, conductive agent, binder, and dispersant in the negative electrode sheet is 85%:10%:2%:1.8%:1.2%. The first layer of additives has a content of 0%, and the second layer has a content of 10%.

[0096] Similarly, the surface density of the active layer coating is 300 g / m². 2 The first layer is 150g / m³ 2 The second layer is 150g / m³ 2 .

[0097] Example 8

[0098] This embodiment is basically the same as Embodiment 2, except that the composition of slurry a is graphite: conductive agent carbon black: binder styrene-butadiene rubber: dispersant sodium carboxymethyl cellulose = 95%: 2%: 1.8%: 1.2%;

[0099] The components of slurry b are graphite: opal-structured titanium dioxide: conductive agent carbon black: binder styrene-butadiene rubber: dispersant sodium carboxymethyl cellulose in a mass ratio of 55%:40%:2%:1.8%:1.2%.

[0100] In the prepared negative electrode sheet, the inverse opal structure of titanium dioxide is concentrated and dispersed on the side away from the current collector. The mass ratio of graphite, titanium dioxide, conductive agent, binder, and dispersant in the negative electrode sheet is 75%:20%:2%:1.8%:1.2%. The first layer of additives has a content of 0%, and the second layer has a content of 20%.

[0101] Similarly, the surface density of the active layer coating is 300 g / m². 2 The first layer is 150g / m³ 2 The second layer is 150g / m³ 2 .

[0102] Comparative Example

[0103] A negative electrode sheet is prepared by the following method:

[0104] Graphite, conductive carbon black, binder styrene-butadiene rubber, dispersant sodium carboxymethyl cellulose, and water are mixed to obtain a negative electrode slurry with a solid content of 45%. This slurry is coated on both sides of the current collector, dried, cold-pressed, and cut to obtain the negative electrode sheet.

[0105] Experimental Example

[0106] The negative electrode sheets described in the various embodiments and comparative examples are assembled into a pouch lithium-ion battery, wherein the positive electrode sheet, separator, and electrolyte involved are specifically as follows:

[0107] Preparation of positive electrode sheet: Lithium iron phosphate, conductive agent, and binder are mixed with N-methylpyrrolidone in a mass ratio of 95.5%:2.5%:2% to obtain a positive electrode slurry with a solid content of 55%. The slurry is coated on both sides of an aluminum foil current collector, dried, cold-pressed, and cut to obtain the positive electrode sheet.

[0108] Separator: Polypropylene diaphragm with a thickness of 16μm.

[0109] Electrolyte preparation: Dimethyl carbonate, ethylene carbonate, and diethyl carbonate are mixed in a ratio of 1:1:1, and lithium hexafluorophosphate is added, wherein the concentration of lithium hexafluorophosphate is 1.1 mol / L.

[0110] (1) Electrode porosity test: Cut an electrode of a certain size, calculate the apparent volume V1, use a true density tester to test the true volume V2 of the electrode, and then calculate the porosity according to (V1-V2) / V1×100%.

[0111] (2) Rate discharge performance test: Charge to 3.65V at 1C constant current and constant voltage at 25℃, cut off the current at 0.05C, let stand for 30min, discharge to 2.2V at nC constant current, record the discharge capacity retention rate, n=1, 3, 5, the discharge capacity retention rate is nC discharge capacity / 1C discharge capacity×100%.

[0112] (3) DC internal resistance (DCR) test: Adjust to 50% SOC at 25℃, let stand for 1 hour, record OCV1, discharge at 3C for 10 seconds, record OCV2, and then calculate DCR according to (OCV1-OCV2) / 3C×1000. Record the test results in Table 1.

[0113] Table 1 Test results for each embodiment and comparative example

[0114] As can be seen from the test data in Table 1, the negative electrode sheets prepared in each embodiment of this disclosure all exhibit good performance after being assembled into batteries.

[0115] Comparing Examples 1-3 with the comparative examples, the additive content is high, the porosity is significantly higher, the capacity retention rate is significantly higher, and the DC internal resistance is significantly lower.

[0116] Comparing Example 5 with Example 2, Example 2 showed better performance. Comparing Example 1 with Example 2, Example 2 showed better performance, indicating that titanium dioxide with an inverse opal structure concentrated on the outer side of the negative electrode has better electrochemical performance.

[0117] Comparing Example 2 with Examples 6, 7, and 8, Example 2 showed better electrochemical performance, indicating that when titanium dioxide is distributed on the outer side, the higher the content, the better the rate performance and the lower the DC internal resistance.

[0118] Comparing Example 4 with Example 3, Example 3 showed better performance, indicating that the electrochemical performance was better when the content was higher closer to the outer side and the formula requirements provided in this disclosure were met.

[0119] In summary, the negative electrode provided in this embodiment incorporates an inverse opal-structured metal oxide in its active layer. This metal oxide imparts a unique pore structure to the negative electrode, increasing its porosity, improving the electrolyte's wettability, and enhancing its liquid retention capacity. Furthermore, the use of a lithium-storage-functional metal oxide as an additive does not reduce the negative electrode's lithium-storage capacity. Therefore, by adding an inverse opal-structured lithium-storage-functional metal oxide to the active layer of the negative electrode, the energy density and rate performance of the negative electrode can be increased while maintaining the lithium-ion transport rate. This negative electrode addresses the problem of reduced electrolyte wettability and decreased ion transport rate, leading to decreased rate performance and power loss, when increasing the coating amount and material compaction density of lithium-ion batteries to improve energy density.

[0120] The above are merely preferred embodiments of this disclosure and are not intended to limit this disclosure. Various modifications and variations can be made to this disclosure by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this disclosure should be included within the scope of protection of this disclosure. Industrial applicability

[0121] The negative electrode sheet disclosed herein can increase the rate performance and reduce the internal resistance of the cell by adding a metal oxide with an inverse opal structure to the negative electrode active layer, while also ensuring the lithium-ion transport rate. This negative electrode sheet can improve the problem of reduced electrolyte wetting and ion transport rate, which leads to a decrease in rate performance and loss of battery power performance, when increasing the coating amount and compaction density of the electrode sheet to improve the energy density of lithium-ion batteries.

Claims

1. A negative electrode sheet, characterized in that, Includes a current collector and an active layer disposed on the surface of the current collector; The active layer comprises negative electrode active material, conductive agent, binder and additives; The additive is a metal oxide with an inverse opal structure.

2. The negative electrode sheet according to claim 1, characterized in that, The active layer has a multi-layer structure; Along the direction away from the current collector, the additive content in each layer of the active layer of the multilayer structure gradually increases.

3. The negative electrode sheet according to claim 2, characterized in that, The content of the additive in each layer of the multilayer structure of the active layer satisfies the following formula: The active layer is defined as the layer closest to the current collector, where a1 is the percentage of the additive in the first layer by mass of the entire active layer. n The percentage of the additive in the nth layer relative to the total active mass, where n is the current layer number. 总 n is the total number of active layers. 总 ≥2, where p is the mass percentage of the additive in the entire active layer, 0.1% ≤ p ≤ 50%; When n 总 ≥2, 0≤a1<p / n 总 a n Starting from the current collector side, the layer gradually increases towards the outermost layer.

4. The negative electrode sheet according to any one of claims 1 to 3, characterized in that, The metal oxide satisfies: The D50 of the metal oxide is 1–40 μm; and / or, The internal pore size of the metal oxide particles is 0.05 to 20 μm, and the internal pore volume accounts for 50 to 90% of the particle volume.

5. The negative electrode sheet according to claim 4, characterized in that, The metal oxide is selected from at least one of titanium dioxide, tin dioxide, and germanium dioxide.

6. The negative electrode sheet according to any one of claims 1 to 5, characterized in that, The active layer comprises, by mass percentage, 43-97.9% of the negative electrode active material, 0.5-3% of the conductive agent, 1-2.5% of the binder, and 0.1-50% of the additives.

7. The negative electrode sheet according to any one of claims 1 to 6, characterized in that, The coating density of the active layer is 40–400 g / m³. 2 .

8. The negative electrode sheet according to claim 6, characterized in that, The active layer also includes 0.5-1.5% dispersant by mass percentage.

9. The negative electrode sheet according to claim 8, characterized in that, The dispersant is selected from at least one of sodium carboxymethyl cellulose, lithium carboxymethyl cellulose, and sodium carboxyethyl cellulose.

10. The negative electrode sheet according to any one of claims 1 to 9, characterized in that, The conductive agent is selected from at least one of carbon black, graphite sheets, carbon nanotubes, and graphene.

11. The negative electrode sheet according to any one of claims 1 to 10, characterized in that, The adhesive is selected from at least one of styrene-butadiene rubber, sodium polyacrylate, sodium alginate, and polyacrylonitrile.

12. The negative electrode sheet according to any one of claims 1 to 11, characterized in that, The negative electrode active material is selected from at least one of graphite, hard carbon, soft carbon, lithium titanate, and mesophase carbon microspheres.

13. The negative electrode sheet according to any one of claims 1 to 12, characterized in that, The active layer is provided on both opposite sides of the current collector.

14. A method for preparing a negative electrode sheet, characterized in that, The method for preparing the negative electrode sheet as described in any one of claims 1 to 13 includes coating the surface of the current collector with a negative electrode slurry containing various components of the active layer, followed by drying and cold pressing.

15. A lithium battery, characterized in that, Includes the negative electrode sheet as described in any one of claims 1 to 13.

Images