Negative electrode sheet and battery

Abstract

This application relates to the field of battery technology, specifically to a negative electrode sheet and a battery. The negative electrode sheet includes: a current collector; a negative electrode active material layer disposed on at least one surface of the current collector, the negative electrode active material layer having a first region and a second region on the surface of the negative electrode active material layer away from the current collector; a lithium replenishment layer disposed on the first region; and a solid electrolyte layer disposed on the surface of the lithium replenishment layer away from the negative electrode active material layer, and also disposed on the second region. This negative electrode sheet can improve battery life and solve the problem of electrolyte consumption caused by direct contact between the lithium replenishment layer and the electrolyte.

Description

Technical Field

[0001] This application relates to the field of battery technology, and more specifically, to negative electrode sheets and batteries. Background Technology

[0002] As the battery industry continues to advance, customers have increasingly higher demands for battery cycle performance. One of the main reasons for battery cycle performance degradation is the continuous consumption of active lithium during cycling, leading to sustained capacity decay. Currently, one of the main solutions is lithium replenishment to the battery, replacing the active lithium consumed by the continuous reaction. The primary manufacturing method involves adding a lithium replenishment layer to the surface of the active material at the negative electrode. However, this method doesn't consider the direct contact between the lithium replenishment layer and the electrolyte, which can lead to electrolyte consumption. When electrolyte consumption reaches a certain level, it causes a sharp increase in the battery's internal resistance, resulting in a drastic decline in the battery's electrochemical performance.

[0003] Therefore, it is necessary to provide a technical solution that can improve battery life and solve the problem of electrolyte consumption caused by direct contact between the lithium replenishment layer and the electrolyte. Utility Model Content

[0004] In view of this, this application aims to at least partially solve one of the technical problems in the related art. To this end, this application provides a negative electrode and a battery that can improve battery lifespan and solve the problem of electrolyte consumption caused by direct contact between the lithium replenishment layer and the electrolyte.

[0005] To solve the above-mentioned technical problems, this application is implemented as follows:

[0006] According to one aspect of this application, an embodiment of this application provides a negative electrode sheet, the negative electrode sheet comprising:

[0007] current collector(100);

[0008] A negative electrode active material layer (200) is disposed on at least one side surface of the current collector (100), and the side surface of the negative electrode active material layer (200) away from the current collector (100) includes a first region and a second region.

[0009] A lithium replenishment layer (300) is disposed on the first region;

[0010] A solid electrolyte layer (400) is disposed on the surface of the lithium replenishment layer (300) on the side away from the negative electrode active material layer (200), and the solid electrolyte layer (400) is also disposed on the second region.

[0011] In one alternative implementation, the first region is located at the center of the surface of the negative electrode active material layer (200) on the side away from the current collector (100);

[0012] The second region is located around the first region.

[0013] In one alternative implementation, the first region is located at the center of the surface of the negative electrode active material layer (200) on the side away from the current collector (100);

[0014] The second region is located on both sides of the first region along the length of the current collector.

[0015] In one alternative implementation, the first region accounts for 60% to 80% of the total area of ​​the negative electrode active material layer (200) on the side away from the surface of the current collector (100).

[0016] In one alternative implementation, the second region accounts for 20% to 40% of the total area of ​​the negative electrode active material layer (200) on the side away from the surface of the current collector (100).

[0017] In one optional implementation, the thickness of the negative electrode active material layer (200) is 110 μm to 180 μm.

[0018] In one alternative implementation, the thickness of the lithium replenishment layer (300) is 1 μm to 10 μm.

[0019] In one alternative embodiment, the solid electrolyte layer (400) disposed on the lithium replenishment layer (300) has a thickness of 2 μm to 15 μm.

[0020] In one alternative implementation, the thickness of the solid electrolyte layer (400) on the second region is set to 3 μm to 25 μm.

[0021] In one alternative embodiment, the negative electrode active material layer (200) includes an active material, which includes a carbon negative electrode material or an alloy negative electrode material.

[0022] In one alternative implementation, the lithium replenishment layer (300) comprises lithium foil or lithium powder.

[0023] In one alternative embodiment, the solid electrolyte layer (400) comprises an oil-based binder.

[0024] In one alternative embodiment, the oil-based binder includes polyvinylidene fluoride, polyacrylonitrile, or polyimide.

[0025] According to a second aspect of this application, an embodiment of this application provides a battery including a negative electrode sheet, the negative electrode sheet including the aforementioned negative electrode sheet.

[0026] The technical solution of this application has at least the following beneficial effects:

[0027] In this embodiment, the provided negative electrode sheet has a lithium replenishment layer disposed on the surface of the negative electrode active material layer away from the current collector. Since the lithium replenishment layer undergoes a volume change while replenishing active lithium, placing it on the outer surface of the negative electrode active material layer prevents the active material from detaching from the current collector. Simultaneously, placing it on the outer surface of the solid-state battery reduces the contact between the lithium replenishment layer and the electrolyte, minimizing electrolyte consumption during battery cycling. Furthermore, this structural arrangement of the solid-state battery also prevents the solid electrolyte layer from detaching after the lithium replenishment layer is consumed.

[0028] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description

[0029] Figure 1 The diagram shown is a cross-sectional view of a negative electrode sheet provided in Embodiment 1 of this application;

[0030] Figure 2 The figure shown is a schematic diagram of a longitudinal section structure of a negative electrode sheet provided in Embodiment 1 of this application;

[0031] Figure 3 The diagram shown is a cross-sectional view of a negative electrode sheet provided in Embodiment 11 of this application.

[0032] Figure 4 The diagram shown is a schematic diagram of the longitudinal section structure of a negative electrode sheet provided in Embodiment 11 of this application.

[0033] 100 current collectors;

[0034] 200 negative electrode active material layer;

[0035] 300 lithium replenishment layer;

[0036] 400 solid electrolyte layer. Detailed Implementation

[0037] The present application will be further described below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the present application.

[0038] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges or individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0039] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0040] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0041] Unless otherwise specified, the terms "comprising" and "including" as used in this application can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other components not listed may also be included, or that only the listed components may be included.

[0042] In related technologies, lithium replenishment is used to address the issue of battery cycle performance degradation. However, the contact between the lithium replenishment layer on the surface of the negative electrode active material layer and the electrolyte can lead to electrolyte consumption. When the electrolyte consumption reaches a certain level, it can cause a sharp increase in the battery's internal resistance, which in turn leads to a sharp decline in the battery's electrochemical performance.

[0043] To address the aforementioned problems, embodiments of this application provide a negative electrode sheet. For example... Figure 1 As shown, some embodiments of this application provide a negative electrode sheet, which includes:

[0044] current collector(100);

[0045] A negative electrode active material layer (200) is disposed on at least one side surface of the current collector (100), and the side surface of the negative electrode active material layer (200) away from the current collector (100) includes a first region and a second region.

[0046] A lithium replenishment layer (300) is disposed on the first region;

[0047] A solid electrolyte layer (400) is disposed on the surface of the lithium replenishment layer (300) on the side away from the negative electrode active material layer (200), and the solid electrolyte layer (400) is also disposed on the second region.

[0048] refer to Figure 1The lithium replenishment layer (300) is disposed on the first region of the negative electrode active material layer (200); the solid electrolyte layer (400) is disposed on the surface of the lithium replenishment layer (300) away from the negative electrode active material layer (200), and the solid electrolyte layer (400) is also disposed on the second region of the negative electrode active material layer (200).

[0049] This application places the lithium replenishment layer (300) on the surface of the negative electrode active material layer (200) away from the current collector (100). Since the lithium replenishment layer (300) undergoes a volume change while replenishing active lithium, placing the lithium replenishment layer (300) on the outer surface of the negative electrode active material layer (200) can prevent the active material from falling off the current collector (100). At the same time, placing it on the outer surface of the solid-state battery can reduce the contact between the lithium replenishment layer (300) and the electrolyte, reducing the consumption of the electrolyte by the lithium replenishment layer (300) during battery cycling. Furthermore, this structural arrangement of the solid-state battery can also prevent the solid electrolyte layer (400) from falling off after the lithium replenishment layer (300) is consumed.

[0050] In some embodiments of this application, reference is made to Figure 1 , Figure 2 The first region is located at the center of the surface of the negative electrode active material layer (200) on the side away from the current collector (100); the second region is located around the first region. This structural arrangement ensures that the solid electrolyte layer (400) completely covers the lithium replenishment layer (300), preventing the solid electrolyte layer (400) from falling off after the lithium replenishment layer (300) is consumed.

[0051] In one alternative implementation, the first region is located at the center of the surface of the negative electrode active material layer (200) on the side away from the current collector (100); the second region is located on both sides of the first region along the length of the current collector.

[0052] In some embodiments of this application, reference is made to Figure 3 , Figure 4 Compared with the above-mentioned technical solution where the solid electrolyte layer (400) completely covers the lithium replenishment layer (300), this solution not only reduces electrolyte consumption and improves the peel strength between the solid electrolyte layer (400) and the active material layer (200), but also takes into account the continuous coating process, thus greatly improving production efficiency.

[0053] In some embodiments of this application, the first region occupies 60% to 80% of the total area of ​​the side of the negative electrode active material layer (200) away from the surface of the current collector (100). As an example, the first region can be any one of 60%, 70%, or 80%, or a range between any two, based on the total area of ​​the side of the negative electrode active material layer (200) away from the surface of the current collector (100). The proportion of the first region within this range ensures that the negative electrode has a good lithium replenishment effect, while also providing good structural stability.

[0054] In some embodiments of this application, the second region accounts for 20% to 40% of the total area of ​​the side of the negative electrode active material layer (200) away from the surface of the current collector (100). As an example, the second region can be any one of 20%, 30%, or 40%, or a range between any two, based on the total area of ​​the side of the negative electrode active material layer (200) away from the surface of the current collector (100). If the proportion of the second region is small, the contact area between the solid electrolyte layer (400) and the negative electrode active material layer (200) is too small, which can easily lead to the solid electrolyte layer (400) falling off, resulting in an unstable structure of the negative electrode sheet; if the proportion of the second region is large, the lithium replenishment layer (300) is too small, resulting in an insignificant lithium replenishment effect.

[0055] In some embodiments of this application, the thickness of the negative electrode active material layer (200) is 110 μm to 180 μm. As an example, the thickness of the negative electrode active material layer (200) can be any one of 110 μm, 130 μm, 160 μm, or 180 μm, or a range between any two. Within this range, the thickness of the negative electrode active material layer (200) can balance energy density and power density. If the thickness of the negative electrode active material layer (200) is too small, the battery energy density is insufficient; if the thickness of the negative electrode active material layer (200) is too large, the battery power density is insufficient.

[0056] In some embodiments of this application, the thickness of the lithium replenishment layer (300) is 1 μm to 10 μm. As an example, the thickness of the lithium replenishment layer (300) can be any one of 1 μm, 3 μm, 7 μm, or 10 μm, or a range between any two. A thickness within this range can meet the lithium-ion demand during battery cycling. If the thickness of the lithium replenishment layer (300) is too small, the replenished lithium-ions will be insufficient, resulting in little improvement in cycle performance; if the thickness of the lithium replenishment layer (300) is too large, the reversible specific capacity of the lithium replenishing agent will be much lower than that of the active material, leading to insufficient utilization of the reversible specific capacity of the electrode.

[0057] In some embodiments of this application, the thickness of the solid electrolyte layer (400) disposed on the lithium replenishment layer (300) is 2 μm to 15 μm. As an example, the thickness of the solid electrolyte layer (400) disposed on the lithium replenishment layer (300) can be any one of 2 μm, 5 μm, 10 μm, or 15 μm, or a range between any two. If the thickness of the solid electrolyte layer (400) disposed on the lithium replenishment layer (300) is too small, the current deposition or coating technology will not meet the requirements; if the thickness of the solid electrolyte layer (400) disposed on the lithium replenishment layer (300) is too large, the fast charging capability of the battery will decrease.

[0058] In some embodiments of this application, the thickness of the solid electrolyte layer (400) on the second region is set to 3 μm to 25 μm. As an example, the thickness of the solid electrolyte layer (400) on the second region can be any one of 3 μm, 6 μm, 10 μm, 15 μm, 20 μm, or 25 μm, or a range between any two. If the thickness of the solid electrolyte layer (400) on the second region is too small, the protection of the lithium replenishment layer will be insufficient; if the thickness of the solid electrolyte layer (400) on the second region is too large, the fast charging capability of the battery will decrease.

[0059] It should be noted that the thickness of the solid electrolyte layer (400) on the second region should be greater than the thickness of the solid electrolyte layer (400) on the lithium replenishment layer (300) to ensure the overall flatness of the solid electrolyte layer (400).

[0060] In some embodiments of this application, the negative electrode active material layer (200) includes an active material, which may be a carbon negative electrode material or an alloy negative electrode material. As an example, the active material may be a carbon negative electrode material or an alloy negative electrode material. For instance, the carbon negative electrode material may be selected from one or more of natural graphite, artificial graphite, hard carbon, soft carbon, and mesophase carbon microspheres; the alloy negative electrode material may be a Si alloy.

[0061] It should be noted that there are no special requirements for the type of active material in the negative electrode active material layer (200), and those skilled in the art can select it as needed.

[0062] In some embodiments of this application, the lithium replenishment layer (300) comprises lithium foil or lithium powder. As an example, the lithium replenishment material of the lithium replenishment layer (300) may be lithium foil or lithium powder.

[0063] In some embodiments of this application, the solid electrolyte layer (400) comprises an oil-based binder. The use of an oil-based binder avoids the reaction between an aqueous binder and the lithium replenishment layer (300), which could lead to the loss of the lithium replenishment layer (300) or even safety issues.

[0064] In some embodiments of this application, the oil-based adhesive includes polyvinylidene fluoride, polyacrylonitrile, or polyimide. As an example, the oil-based adhesive may be polyvinylidene fluoride or polyacrylonitrile.

[0065] Some embodiments of this application also provide a method for preparing a negative electrode, comprising the following steps:

[0066] S1. After mixing the active material, the first conductive agent, and the first binder in a solvent, a negative electrode active material layer (200) slurry is obtained; the negative electrode active material layer (200) slurry is coated on the surface of the current collector along its own thickness direction, and after drying, a negative electrode active material layer (200) is obtained.

[0067] S2. Mix the lithium replenishing material and the second binder in a solvent to obtain a lithium replenishing slurry. Coat the lithium replenishing slurry in the first region and dry it under an inert atmosphere to obtain a lithium replenishing layer (300).

[0068] S3. Mix the solid electrolyte and oil-based binder in a solvent to obtain a solid electrolyte slurry. Coat the solid electrolyte onto the surface of the second region and the lithium replenishment layer (300) on the side away from the negative electrode active material layer (200). Dry the slurry under an inert atmosphere to obtain a solid electrolyte layer (400).

[0069] In some embodiments of this application, the mass ratio of the active material, the first binder, and the conductive agent is (95-96):(3-4):1. As an example, the mass ratio of the active material, the first binder, and the conductive agent can be any one of 95:3:1, 95.5:3.5:1, or 96:4:1, or a range between any two.

[0070] In some embodiments of this application, the mass ratio of the lithium replenishing material to the second binder is (1-3):(7-9). As an example, the mass ratio of the lithium replenishing material to the second binder can be any one of 1:7, 2:8, or 3:9, or a range between any two.

[0071] In some embodiments of this application, the mass ratio of solid electrolyte to oil-based binder is (80-90):(10-20). As an example, the mass ratio of solid electrolyte to oil-based binder can be any one of 80:20, 90:10, or 85:15, or a range between any two. If the content of the oil-based binder is too low, the solid electrolyte layer (400) will detach from the surface of the lithium replenishment layer and the active material layer; if the content of the oil-based binder is too high, it will affect lithium-ion transport and significantly degrade kinetic performance.

[0072] In some embodiments of this application, the conductive agent includes at least one of conductive carbon black, conductive graphite, carbon fiber, or carbon nanotubes. For example, the conductive agent may be conductive carbon black or conductive graphite.

[0073] In some embodiments of this application, the first adhesive and the second adhesive each independently include at least one of styrene-butadiene rubber, sodium carboxymethyl cellulose, polyvinylidene fluoride, polyacrylic acid, or polyvinyl alcohol. For example, the adhesive may be styrene-butadiene rubber or polyacrylic acid.

[0074] In some embodiments of this application, the solid electrolyte includes at least one of polymer solid electrolyte, oxide solid electrolyte, or sulfide solid electrolyte.

[0075] According to a second aspect of this application, an embodiment of this application provides a battery including a negative electrode sheet, the negative electrode sheet including the aforementioned negative electrode sheet.

[0076] This application also provides a battery in some embodiments, including: a negative electrode sheet as described in any of the above embodiments of this application; and / or a negative electrode sheet prepared by the method for preparing the negative electrode sheet as described in any of the above embodiments of this application.

[0077] In some embodiments of this application, the battery further includes a positive electrode, an electrolyte, and a separator. That is, the battery includes a positive electrode, a negative electrode, an electrolyte, and a separator.

[0078] In this embodiment, the materials and structures of the positive electrode current collector 1 and the conductive agent and binder in the positive electrode active material layer are not limited, and the positive electrode structure and composition known in the art that can be used in secondary batteries can be selected.

[0079] In this embodiment, the specific material or type of the separator is not limited, and any separator known in the art that can be used in secondary batteries can be selected.

[0080] It should also be noted that the battery in this application does not limit the specific material or type of electrolyte. Any components and types known in the art that can be used in secondary batteries can be selected, as long as the purpose of this application can be achieved.

[0081] Since the battery provided in this application adopts all the technical solutions of the above embodiments, it has at least all the beneficial effects brought about by the technical solutions of the above embodiments, and will not be described in detail here.

[0082] Since the battery provided in this application adopts all the technical solutions of the above embodiments, it has at least all the beneficial effects brought about by the technical solutions of the above embodiments, which will not be repeated here.

[0083] The present application will be described in detail below with reference to the accompanying drawings and examples. However, the implementation and protection of the present application are not limited thereto. The following embodiments are only some embodiments of the present application and are not intended to limit the present application.

[0084] Example 1

[0085] S1. The active materials artificial graphite, carboxymethyl cellulose (CMC), styrene-butadiene rubber (SBR), and conductive carbon black (Super-P) are placed in a mixing tank in a ratio of 95.5:1.5:2:1. After adding pure water and stirring evenly, an active material layer slurry is obtained.

[0086] The active material layer slurry is uniformly coated onto the current collector, and then dried in an oven to obtain the negative electrode active material layer.

[0087] S2. Lithium powder, polyvinylidene fluoride (PVDF), and N-methylpyrrolidone (NMP) are mixed evenly in a ratio of 2:8:90 to obtain a lithium replenishing slurry. The lithium replenishing slurry is coated on the first region and dried under an inert atmosphere to obtain a lithium replenishing layer.

[0088] S3. Li4SnS4 and polyvinylidene fluoride (PVDF) are uniformly dispersed in NMP solvent at a ratio of 90:10 to obtain a solid electrolyte slurry. The solid electrolyte is coated onto the second region and the surface of the lithium replenishment layer away from the negative electrode active material layer, and dried under an inert atmosphere to obtain a solid electrolyte layer.

[0089] The thickness of the negative electrode active material layer, the thickness of the lithium replenishment layer, the thickness of the solid electrolyte layer in the second region, the thickness of the solid electrolyte layer above the lithium replenishment layer, the percentage of the area of ​​the first region in the negative electrode active material layer, and the percentage of the area of ​​the second region in the negative electrode active material layer in Example 1 are shown in Table 1.

[0090] Examples 2-10

[0091] The specific differences between Examples 2-10 and Example 1 are shown in Table 1.

[0092] Example 11

[0093] The difference between Example 11 and Example 1 is that the second region in Example 11 is located on both sides of the first region along the length of the current collector. For details, please refer to the appendix of the specification. Figure 3 Included with instruction manual Figure 4 .

[0094] Comparative Example 1

[0095] The difference between Comparative Example 1 and Example 1 is that the negative electrode of Comparative Example 1 does not contain a lithium replenishment layer and a solid electrolyte layer.

[0096] Comparative Example 2

[0097] The difference between Comparative Example 2 and Example 1 is that the negative electrode of Comparative Example 2 does not contain a solid electrolyte layer.

[0098] Comparative Example 3

[0099] The difference between Comparative Example 3 and Example 1 is that the solid electrolyte layer of the negative electrode in Comparative Example 3 is only in contact with the lithium replenishment layer.

[0100] Performance testing

[0101] Battery manufacturing

[0102] Positive electrode sheet: The positive active material (lithium iron phosphate), conductive agent (conductive carbon black) and binder (PVDF) are mixed in a mass ratio of 97:2:1 to obtain a mixed material. The mixed material is thoroughly stirred in NMP to obtain a positive electrode slurry. The obtained slurry is coated on conventional aluminum foil, and after drying and rolling, a positive electrode sheet is obtained.

[0103] Separating membrane: PE porous polymer film is used as the separating membrane.

[0104] Electrolyte: Ethyl carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) are mixed in a volume ratio of 3:5:2. Then, fully dried lithium salt LiPF6 is dissolved in the mixed organic solvent at a ratio of 1.2 mol / L to prepare the electrolyte.

[0105] Battery assembly: The negative electrode sheets prepared in each embodiment and comparative example are arranged with the positive electrode sheets and separators. A separator is placed between each pair of positive and negative electrodes, and the cells are wound up to obtain bare cells. The bare cells are placed in an outer packaging shell, and the prepared electrolyte is injected into the dried bare cells. After vacuum sealing, settling, formation, and shaping, a lithium-ion battery is obtained.

[0106] 25℃ Cycle Life Test: Place the battery in a 25℃ incubator and let it rest for 6 hours; first charge it at a constant current of 1C to 3.65V, then charge it at a constant voltage of 3.65V to 0.05C, and let it rest for 10 minutes; then discharge it at a constant voltage of 1C to 2.5V, and let it rest for 10 minutes; record and mark the discharge capacity of each cycle, for example, the capacity of the first cycle is C1, and the capacity of the nth cycle is Cn; the SOH of the battery in the nth cycle is calculated as: Cn / C1*100%; record the number of cycles when the battery reaches 80% SOH, which is the battery's 25℃ cycle life.

[0107] 4C fast charging test: ① Place the battery in a 25℃ temperature chamber for 6 hours;

[0108] ② First, charge at a constant current of 0.33C to 3.65V, then charge at a constant voltage of 3.65V to 0.05C, and let stand for 10 minutes;

[0109] ③ Discharge at a constant voltage of 0.33C to 2.5V, and let stand for 10 minutes;

[0110] ④ Repeat the cycle 3 times, and record the discharge capacity of the last cycle as C0;

[0111] ⑤ First charge with 4C0 constant current to 3.65V, then charge with 3.65V constant voltage to 0.05C, and let stand for 10 minutes;

[0112] ⑥ Discharge 4C0 at a constant current to 2.5V and let it stand for 10 minutes;

[0113] After 50 cycles, the battery was removed and disassembled to observe the lithium plating at the negative electrode interface.

[0114] The results of the 25°C cycle life test and the 4C fast charging test for each embodiment and comparative example are shown in Table 1.

[0115] Table 1

[0116]

[0117]

[0118] Note: " / " in the table indicates that the data item does not exist.

[0119] As can be seen from the data in Table 1, comparing Examples 1 and 8, it shows that the addition of the solid electrolyte layer improves the cycle life while having little impact on the fast charging capability; comparing Examples 5, 6 and 8, it shows that the addition of the lithium replenishment layer improves the cycle life while having little impact on the fast charging capability; comparing Examples 2, 7 and 10, it shows that the increased contact area ratio between the solid electrolyte layer and the lithium replenishment layer improves the cycle life while having little impact on the fast charging capability.

[0120] Compared with Example 1, the coating method of the solid electrolyte layer on the lithium replenishment layer in Example 11 has changed from a U-shaped coating to a Z-shaped coating (see [link to example] for specific structural differences). Figures 1-4 Example 11 achieves the same contact area as Example 1 by increasing the contact width between the U-shaped solid electrolyte layer and the active material layer. Data shows a slight decrease in cycle performance, due to partial contact between the lithium replenishment layer and the electrolyte, leading to increased irreversible active lithium loss. However, compared to the comparative example, its cycle performance is still significantly improved, indicating that this coating method isolates most of the lithium replenishment layer surface, greatly reducing irreversible active lithium loss, while having little impact on fast charging performance.

[0121] Comparative Example 1, without the addition of a lithium replenishment layer and a solid electrolyte layer, had a poor cycle life, mainly because the loss of active lithium could not be replenished. Comparative Example 2, with only the addition of a lithium replenishment layer, showed a slightly improved cycle life compared to Comparative Example 1, but the cycle life degraded rapidly in the later stages. Disassembly revealed that the main reason was the side reaction between the electrolyte and the lithium powder in the lithium replenishment layer, which led to the complete consumption of the electrolyte. Comparative Example 3 contained both a lithium replenishment layer and a solid electrolyte layer, but the solid electrolyte layer only contacted the lithium replenishment layer. The cycle life was slightly improved compared to Comparative Example 2, indicating that the solid electrolyte layer reduced the side reaction between the electrolyte and the lithium replenishment layer, but the improvement in cycle life was small. Disassembly of the battery revealed that the solid electrolyte layer detached, and it could no longer effectively reduce the contact between the electrolyte and the lithium replenishment layer in the later stages.

[0122] The parts not described in detail in this application are techniques known to those skilled in the art.

[0123] The basic principles of this application have been described above with reference to specific embodiments. However, it should be noted that the advantages, benefits, and effects mentioned in this application are merely examples and not limitations, and should not be considered as essential features of each embodiment of this application. Furthermore, the specific details disclosed above are for illustrative and facilitative purposes only, and are not limitations. These details do not limit the application to the necessity of employing the aforementioned specific details for implementation.

[0124] It should be noted that the terms "and / or" or " / " used herein are merely descriptions of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. The singular forms "a," "the," and "the" used in the embodiments of this application and the appended claims are also intended to include the plural forms, unless the context clearly indicates otherwise.

[0125] In the detailed description and claims, a list of items connected by the terms "at least one of," "at least one of," "at least one of," or other similar terms may mean any combination of the listed items. For example, if items A and B are listed, then the phrase "at least one of A and B" means only A; only B; or A and B. In another example, if items A, B, and C are listed, then the phrase "at least one of A, B, and C" means only A; or only B; only C; A and B (excluding C); A and C (excluding B); B and C (excluding A); or all of A, B, and C. Item A may contain a single element or multiple elements. Item B may contain a single element or multiple elements. Item C may contain a single element or multiple elements.

[0126] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application.

Claims

1. A negative electrode sheet characterized by comprising: The negative electrode includes: current collector(100); A negative electrode active material layer (200) is disposed on at least one side surface of the current collector (100), and the side surface of the negative electrode active material layer (200) away from the current collector (100) includes a first region and a second region. A lithium replenishment layer (300) is disposed on the first region; A solid electrolyte layer (400) is disposed on the surface of the lithium replenishment layer (300) on the side away from the negative electrode active material layer (200), and the solid electrolyte layer (400) is also disposed on the second region.

2. The negative electrode sheet according to claim 1, characterized by The first region is located at the center of the surface of the negative electrode active material layer (200) on the side away from the current collector (100); The second region is located around the first region; Alternatively, the second region may be located on both sides of the first region along the length of the current collector.

3. The negative electrode sheet according to claim 1, characterized by Based on the total area of ​​the side of the negative electrode active material layer (200) away from the surface of the current collector (100), the first region accounts for 60% to 80%; And / or, based on the total area of ​​the negative electrode active material layer (200) on the side away from the surface of the current collector (100), the second region accounts for 20% to 40%.

4. The negative electrode sheet according to claim 1, characterized by The thickness of the negative electrode active material layer (200) is 110μm to 180μm.

5. The negative electrode sheet according to claim 1, wherein The thickness of the lithium replenishment layer (300) is 1 μm to 10 μm.

6. The negative electrode sheet according to claim 1, wherein The thickness of the solid electrolyte layer (400) disposed on the lithium replenishment layer (300) is 2μm to 15μm; And / or, the thickness of the solid electrolyte layer (400) on the second region is set to 3 μm to 25 μm.

7. The negative electrode sheet according to claim 1, wherein The negative electrode active material layer (200) includes an active material, which includes a carbon negative electrode material or an alloy negative electrode material.

8. The negative electrode sheet according to claim 1, characterized by The lithium replenishment layer (300) comprises lithium foil or lithium powder.

9. The negative electrode sheet according to claim 1, wherein The solid electrolyte layer (400) contains an oil-based binder; The oil-based binder includes polyvinylidene fluoride, polyacrylonitrile, or polyimide.

10. A battery comprising a negative electrode sheet, characterized by, The negative electrode includes the negative electrode as described in any one of claims 1 to 9.

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