Negative electrode sheet, electrochemical device, and electronic device

Abstract

The utility model relates to electrochemical energy storage technical field discloses a kind of negative plate, electrochemical device and electronic equipment, negative plate, including current collector and first active material layer, current collector has first surface along the side of thickness direction;First active material layer includes multiple first silicon-doped sections and multiple first non-silicon-doped sections, first silicon-doped section and first non-silicon-doped section are connected to first surface, at least one first non-silicon-doped section is equipped with at least one first recess, to reduce the risk of electrochemical device self-discharge.

Description

Technical Field

[0001] This utility model relates to the field of electrochemical energy storage technology, specifically to a negative electrode, an electrochemical device, and an electronic device. Background Technology

[0002] With the development of the industry, the energy density requirements for battery cells are becoming increasingly stringent. Due to the high theoretical specific capacity of silicon-based materials, the energy density of lithium-ion batteries can be improved by doping the negative electrode with silicon. For silicon-doped negative electrodes, one way to increase the charging rate is to process grooves on the negative electrode sheet. However, during the groove processing, it is unavoidable to break silicon-carbon particles, and the broken silicon-carbon particles increase the risk of self-discharge in lithium batteries. Utility Model Content

[0003] This invention aims to solve at least one of the technical problems existing in the prior art. To this end, this invention proposes a negative electrode sheet that can reduce the risk of self-discharge in electrochemical devices.

[0004] This invention also proposes an electrochemical device having the above-mentioned negative electrode, and an electronic device having the electrochemical device.

[0005] According to a first aspect of the present invention, the negative electrode includes a current collector and a first active material layer. The current collector has a first surface on one side along the thickness direction. The first active material layer includes a plurality of first silicon-doped segments and a plurality of first undoped segments. The first silicon-doped segments and the first undoped segments are all connected to the first surface. At least one first undoped segment is provided with at least one first groove.

[0006] The negative electrode sheet according to the embodiments of this utility model has at least the following beneficial effects: By providing multiple first silicon-doped sections and multiple first undoped sections in the active material layer, the lithium storage capacity of the negative electrode sheet is improved, thereby increasing the energy density of the electrochemical device. By providing at least one first groove in at least one first undoped section, the first groove can shorten the lithium-ion migration path, thereby improving the charging rate of the electrochemical device. Furthermore, since the first groove is located in the first undoped section, the reduction in silicon content due to its location in the first silicon-doped section can be avoided, thus preventing a decrease in the energy density of the electrochemical device. It also avoids the breakage of silicon-carbon particles during the processing of the first groove in the first silicon-doped section, thereby helping to prevent the free accumulation of silicon-carbon particles in the pores of the separator, and thus reducing the risk of self-discharge in the electrochemical device.

[0007] According to some embodiments of the present invention, the first undoped silicon segment has a first edge and a second edge spaced apart from each other along the width direction of the negative electrode sheet; the first groove extends along the width direction and penetrates at least one of the first edge and the second edge.

[0008] According to some embodiments of the present invention, along the winding direction of the negative electrode sheet, the width of the first groove is ≥30 micrometers and ≤90 micrometers.

[0009] According to some embodiments of the present invention, 30% of the thickness of the first undoped silicon segment along the thickness direction is less than 70% of the thickness of the first undoped silicon segment along the thickness direction.

[0010] According to some embodiments of the present invention, the first silicon-doped segment and the first undoped segment are alternately distributed along the winding direction of the negative electrode sheet; along the winding direction, the length of the first undoped segment / the length of the first silicon-doped segment is ≥1 / 10 and ≤1 / 2.

[0011] According to some embodiments of the present invention, the length of the first undoped silicon section along the winding direction is ≥0.5 mm and ≤1 mm; and / or, the length of the first doped silicon section along the winding direction is ≥1 mm and ≤5 mm.

[0012] According to some embodiments of the present invention, the current collector has a second surface on the side opposite to the first surface along the thickness direction; the negative electrode also includes a second active material layer, which includes a plurality of second silicon-doped segments and a plurality of second undoped segments, both of which are connected to the second surface and are alternately distributed along the winding direction of the negative electrode.

[0013] According to some embodiments of the present invention, at least one second undoped silicon segment is provided with at least one second groove.

[0014] An electrochemical device according to a second aspect of the present invention includes an electrode assembly, which includes a positive electrode, a negative electrode as described in any of the above embodiments, and a separator disposed between the positive electrode and the negative electrode. The positive electrode, the separator, and the negative electrode are stacked and wound into a core structure along the winding direction.

[0015] An electronic device according to a third aspect of the present invention includes the electrochemical device described in the above embodiments.

[0016] Additional aspects and advantages of this invention 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 the invention. Attached Figure Description

[0017] The present invention will be further described below with reference to the accompanying drawings and embodiments, wherein: Figure 1 A schematic diagram of the negative electrode sheet provided in this embodiment of the present invention is shown; Figure 2 It shows Figure 1 Enlarged structural diagram at point II; Figure 3 This shows a structural schematic diagram of the negative electrode sheet provided in an embodiment of the present invention from another perspective; Figure 4 It shows Figure 3 Enlarged structural diagram at point IV; Figure 5 The following is a histogram of K-values ​​for the electrochemical device provided in the embodiments of the present invention and related electrochemical devices; Figure 6 The capacity histogram of the electrochemical device provided in the embodiments of the present invention and the electrochemical device of related technologies is shown.

[0018] Figure label: Negative electrode 100; Current collector 110; First surface 111; Second surface 113; First active material layer 130; First silicon-doped section 131; First undoped section 133; First groove 1331; First edge 1333; Second edge 1335; Second active material layer 150; Second silicon-doped section 151; Second undoped section 153; Second groove 1531; Tab 170; Winding direction X; width direction Y; thickness direction Z. Detailed Implementation

[0019] The embodiments of this utility model are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this utility model, and should not be construed as limiting this utility model.

[0020] In the description of this utility model, it should be understood that the directional descriptions, such as up, down, front, back, left, right, etc., indicate the directional or positional relationship based on the directional or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this utility model.

[0021] In the description of this utility model, "several" means one or more, "multiple" means two or more, "greater than," "less than," and "exceeding" are understood to exclude the stated number, while "above," "below," and "within" are understood to include the stated number. The use of "first" and "second" in the description is merely for distinguishing technical features and should not be construed as indicating or implying relative importance, or implicitly indicating the number of indicated technical features, or implicitly indicating the order of the indicated technical features.

[0022] In the description of this utility model, unless otherwise explicitly defined, terms such as "setting," "installation," and "connection" should be interpreted broadly, and those skilled in the art can reasonably determine the specific meaning of the above terms in this utility model in conjunction with the specific content of the technical solution.

[0023] In the description of this utility model, the terms "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of this utility model. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0024] This application provides an electronic device, which includes an electrochemical device. The electronic device in this application is not particularly limited and can be any electronic device known in the prior art.

[0025] The electronic devices described in this application are not particularly limited in their application and can be used with any electronic device known in the prior art. These electronic devices include, but are not limited to, mobile phones, smartphones, laptops, tablets, wearable devices, smartwatches, smart bracelets, smart glasses, power banks, televisions, game consoles, game controllers, digital cameras, smart speakers, headphones, keyboards, mice, monitors, drones, audio equipment, home appliances, toys, power tools, automobiles, motorcycles, electric bicycles, bicycles, robots, robotic dogs, industrial robots, and android robots.

[0026] In some embodiments, the electrochemical device includes any device in which an electrochemical reaction occurs to interconvert chemical energy and electrical energy, and specific, non-limiting examples include all types of primary batteries, secondary batteries, fuel cells, solar cells, or capacitors. In particular, the electrochemical device is a lithium secondary battery, including lithium metal secondary batteries, lithium-ion secondary batteries, lithium polymer secondary batteries, or lithium-ion polymer secondary batteries.

[0027] Please see Figure 1 In some embodiments, the electrochemical device includes an electrode assembly, which includes a positive electrode plate, a negative electrode plate 100, and a separator disposed between the positive electrode plate and the negative electrode plate 100. The positive electrode plate, the separator, and the negative electrode plate 100 are stacked and wound into a core structure along the winding direction X. This utility model does not limit the specific structure of the core, as long as it can achieve the purpose of this utility model.

[0028] In some embodiments, the electrochemical device further includes a housing and an electrolyte, with the electrode assembly housed within the housing and the electrolyte filling the housing to wet the electrode assembly. The housing can be a steel shell or a flexible encapsulation shell.

[0029] As an example, taking a steel casing as an example, the casing may include a positive conductive part and a negative conductive part, which may be insulated from each other to avoid short circuits. The electrode assembly may also include a positive tab and a negative tab. One end of the positive tab may be connected to the positive electrode plate, and the other end may be directly connected to the positive conductive part or connected to the positive conductive part through a first conductive element. One end of the negative tab may be connected to the negative electrode plate 100, and the other end may be directly connected to the negative conductive part or connected to the negative conductive part through a second conductive element, thereby forming a charging and discharging circuit.

[0030] Please see Figures 1 to 2 In some embodiments, the negative electrode 100 includes a current collector 110 and a first active material layer 130.

[0031] The first active material layer 130 includes multiple first silicon-doped segments 131 and multiple first undoped segments 133. The current collector 110 has a first surface 111 on one side along the thickness direction Z. Both the first silicon-doped segments 131 and the first undoped segments 133 are connected to the first surface 111. Thus, by setting the first silicon-doped segments 131, the lithium storage capacity of the negative electrode 100 is improved, thereby increasing the energy density of the electrochemical device. "Multiple" can refer to two or more.

[0032] Both the first silicon-doped segment 131 and the first undoped silicon segment 133 can be coated onto the first surface 111 using a coating process. The first silicon-doped segment 131 may refer to a negative electrode active material containing silicon, and the first undoped silicon segment 133 may refer to a negative electrode active material without silicon.

[0033] As an example, the first undoped silicon segment 133 can be an active material containing graphite material.

[0034] The distribution of the multiple first silicon-doped segments 131 and multiple first undoped segments 133 can be flexibly configured according to requirements. For example, the multiple first silicon-doped segments 131 and multiple first undoped segments 133 can be alternately distributed along the width direction Y of the negative electrode 100, or alternately distributed along the winding direction X of the negative electrode 100, or distributed along other directions. Any adjacent first silicon-doped segments 131 and multiple first undoped segments 133 can be connected or spaced apart. Understandably, any two of the winding direction X, width direction Y, and thickness direction Z are perpendicular to each other.

[0035] At least one first undoped silicon section 133 is provided with at least one first groove 1331. Thus, the first groove 1331 can shorten the migration path of lithium ions, thereby improving the charging rate of the electrochemical device. In addition, since the first groove 1331 is provided in the first undoped silicon section 133, the silicon content can be reduced due to the first groove 1331 being located in the first doped silicon section 131, thereby affecting the energy density of the electrochemical device. It can also prevent the silicon carbon particles from being broken during the processing of the first groove 1331 in the first doped silicon section 131, thereby helping to prevent the free accumulation of silicon carbon particles in the pores of the separator, thereby reducing the risk of self-discharge of the electrochemical device. Furthermore, it also helps to prevent the silicon carbon particles with high hardness from piercing the separator, improving the safety performance of the electrochemical device.

[0036] At least one first undoped silicon segment 133 is provided with at least one first groove 1331. It can be that only one first undoped silicon segment 133 is provided with a first groove 1331, or only one first undoped silicon segment 133 is provided with multiple first grooves 1331, or multiple first undoped silicon segments 133 are each provided with a first groove 1331, or multiple first undoped silicon segments 133 are each provided with multiple first grooves 1331, or each first undoped silicon segment 133 is provided with multiple first grooves 1331.

[0037] The winding direction X of the negative electrode 100 can be the direction in which the negative electrode 100, the separator, and the positive electrode are stacked and wound into a core structure. When the negative electrode 100 is in a flat and unfolded state, the winding direction X of the negative electrode 100 can be the length direction of the negative electrode 100.

[0038] In some embodiments, the first silicon-doped segment 131 and the first undoped segment 133 are alternately distributed along the winding direction X of the negative electrode 100, which helps the first silicon-doped segment 131 and the first undoped segment 133 to be periodically distributed, making the distribution more uniform and reducing the situation where multiple first undoped segments 133 are concentrated, resulting in poor kinetics of lithium ions in some areas of the negative electrode 100.

[0039] In some embodiments, along the winding direction X, the length L of the first silicon-doped segment 131 is greater than or equal to the length N of the first undoped segment 133. On the one hand, increasing the length L of the first silicon-doped segment 131 helps to improve the lithium storage capacity of the negative electrode 100 and further improves the energy density of the electrochemical device. On the other hand, by shortening the length N of the first undoped segment 133, the area of ​​the first undoped segment 133 participating in the reaction can be reduced, and lithium ions can diffuse better in the first silicon-doped segment 131, improving the situation of lithium plating caused by excessive lithium ion insertion into the first undoped segment 133 and improving the safety performance of the electrochemical device.

[0040] In some embodiments, along the winding direction X, the length N of the first undoped silicon segment 133 and the length L of the first doped silicon segment 131 are ≥1 / 10 and ≤1 / 2, thereby further optimizing the distribution of the first undoped silicon segment 133 and the first doped silicon segment 131, which helps to further improve the lithium storage capacity of the negative electrode 100 and further reduce the lithium plating of the first undoped silicon segment 133.

[0041] As an example, the length N of the first undoped silicon segment 133 along the winding direction X / the length L of the first doped silicon segment 131 along the winding direction X can be 1 / 10, 1 / 9, 1 / 5, 1 / 2 or any other value between any two of the above.

[0042] In some embodiments, the length N of the first undoped silicon segment 133 along the winding direction X is ≥ 0.5 mm and ≤ 1 mm. This allows the length L of the first doped silicon segment 131 to be ensured by controlling the length of the first undoped silicon segment 133 along the winding direction X, thereby further improving the energy density of the electrochemical device. In addition, it can reduce the reaction area of ​​the first undoped silicon segment 133, improve the lithium plating situation of the first undoped silicon segment 133, and also help ensure that the first undoped silicon segment 133 has sufficient length along the winding direction X, reducing the coating difficulty of the first undoped silicon segment 133 and the difficulty of processing the first groove 1331 in the first undoped silicon segment 133.

[0043] As an example, the length N of the first undoped silicon segment 133 along the winding direction X can be 0.5 mm, 0.6 mm, 0.85 mm, 1 mm, or any other value between any two of the above.

[0044] In some embodiments, along the winding direction X, the length L of the first silicon-doped segment 131 is ≥1 mm and ≤5 mm, thereby increasing the length L of the first silicon-doped segment 131 and further improving the energy density of the electrochemical device.

[0045] As an example, the length L of the first silicon-doped segment 131 along the winding direction X can be 1 mm, 1.9 mm, 3.8 mm, 5 mm, or any other value between any two of the above.

[0046] In some embodiments, the first undoped silicon segment 133 has a first edge 1333 and a second edge 1335.

[0047] The first edge 1333 and the second edge 1335 can be spaced apart relative to each other along the width direction Y of the negative electrode 100.

[0048] The opening of the first groove 1331 can be located on the surface of the first undoped silicon segment 133 facing away from the current collector 110. The first groove 1331 extends along the width direction Y and penetrates at least one of the first edge 1333 and the second edge 1335, thereby increasing the extension length of the first groove 1331 along the width direction Y, which helps to provide a larger area migration channel for lithium ions and further improves the charging rate of the electrochemical device.

[0049] It should be noted that during the electrode fabrication process, a silicon-doped negative electrode active material layer and an undoped negative electrode active material layer can be coated on the foil first. Then, a groove structure is processed on the undoped active material layer, which can be done by laser etching or other methods. The foil coated with the negative electrode active material is then die-cut to form multiple negative electrode sheets 100. The first groove 1331 is configured to extend along the width direction Y and penetrate through the first edge 1333 and the second edge 1335. During the processing of the groove structure, a complete groove structure can be processed directly without processing a broken groove structure. The die-cut groove structure forms the first groove 1331 on each negative electrode sheet 100, thereby reducing the processing difficulty of the groove structure and improving the electrode fabrication efficiency.

[0050] Please see Figures 3 to 4 In some embodiments, the width W of the first groove 1331 along the winding direction X is ≥30 micrometers and ≤90 micrometers, which helps to provide a larger migration channel for lithium ions and further improves the charging rate of the electrochemical device.

[0051] As an example, the width W of the first groove 1331 can be 30 micrometers, 44 micrometers, 60 micrometers, 82 micrometers, 90 micrometers, or any other value between any two of the above.

[0052] In some embodiments, 30% of the thickness M of the first undoped silicon segment 133 along the thickness direction Z is less than or equal to 70% of the thickness M of the first undoped silicon segment 133 along the thickness direction Z towards the current collector 110. This ensures that the first groove 1331 has a sufficiently deep depth to improve the migration speed of lithium ions. Additionally, a portion of the undoped silicon active material is retained between the first groove 1331 and the current collector 110 to separate the current collector 110, which helps to avoid the laser thermal effect generated during laser processing of the first groove 1331 from affecting the mechanical strength of the current collector 110.

[0053] As an example, the depth H of the first groove 1331 extending toward the current collector 110 along the thickness direction Z from its opening can be 30%, 40%, 55%, 68%, 70% of the thickness M of the first undoped silicon segment 133 along the thickness direction Z, or any other percentage value between any two of the above percentage values.

[0054] It should be noted that the thickness of the first undoped silicon segment 133 and the first doped silicon segment 131 is approximately the same.

[0055] In some embodiments, the current collector 110 has a second surface 113 on the side opposite to the first surface 111 along the thickness direction Z, and the negative electrode 100 may also include a second active material layer 150.

[0056] The second active material layer 150 includes a second silicon-doped section 151 and a second undoped section 153. Both the second silicon-doped section 151 and the second undoped section 153 are connected to the second surface 113, thereby allowing active materials to be disposed on both sides of the current collector 110, which helps to improve the energy storage performance of the electrochemical device. In addition, by setting the second silicon-doped section 151, it helps to further improve the lithium storage capacity of the negative electrode 100, and further improve the energy density of the electrochemical device.

[0057] Both the second silicon-doped segment 151 and the second undoped segment 153 can be coated onto the second surface 113 using a coating process.

[0058] The second silicon-doped segment 151 can refer to a negative electrode active material containing silicon material, and the second undoped silicon segment 153 can refer to a negative electrode active material without silicon material.

[0059] The second silicon-doped section 151 and the second undoped section 153 can be alternately distributed along the winding direction X, which helps to make the distribution of the second silicon-doped section 151 and the second undoped section 153 more uniform and reduces the poor lithium-ion kinetics in some areas of the negative electrode 100.

[0060] In some embodiments, at least one second undoped silicon section 153 is provided with at least one second groove 1531. Thus, the second groove 1531 can shorten the migration path of lithium ions, thereby improving the charging rate of the electrochemical device. In addition, since the second groove 1531 is provided in the second undoped silicon section 153, the silicon content can be reduced due to the second groove 1531 being provided in the second doped silicon section 151, thereby affecting the energy density of the electrochemical device. It can also prevent the silicon carbon particles from being broken during the processing of the second groove 1531 in the second doped silicon section 151, thereby preventing the free accumulation of silicon carbon particles in the membrane through-holes, thereby further reducing the risk of self-discharge of the electrochemical device. In addition, it also helps to prevent the silicon carbon particles with high hardness from piercing the membrane, improving the safety performance of the electrochemical device.

[0061] The layout and size parameters of the second silicon-doped segment 151, the second undoped segment 153, and the second groove 1531 can all refer to the layout and size parameters of the first silicon-doped segment 131, the first undoped segment 133, and the first groove 1331 in the above embodiments, and will not be repeated here.

[0062] In some embodiments, the negative electrode 100 may include a negative electrode tab 170, which may be partially connected to the first surface 111 or the second surface 113 and partially extend outside the edge of the current collector 110 along the width direction Y.

[0063] Take the tab 170 connected to the first surface 111 as an example.

[0064] As an example, the first surface 111 may include a first coated area and a first uncoated area connected together, the first coated area and the first uncoated area being distributed along the winding direction X, and the first uncoated area being located at one end of the current collector 110 along the winding direction X. The first silicon-doped segment 131 and the first undoped segment 133 may both be connected to the first coated area, and the negative electrode tab 170 may be connected to the first uncoated area.

[0065] As another example, a first undoped silicon segment 133 is provided with a tab groove to expose a portion of the first surface 111 and form a blank area, and a tab 170 may be partially disposed in the tab groove and connected to the blank area.

[0066] It should be noted that the tab 170 can also be connected to the second surface 113. The connection position can be referred to the connection position of the tab 170 on the first surface 111 in the example above, and will not be repeated here.

[0067] Figure 5 and Figure 6 The figures are histograms of the electrochemical device provided in the embodiments of this application and the electrochemical device in related technologies, respectively, regarding the K value (K value refers to the voltage drop of the battery per unit time) and capacity. The solid line represents the electrochemical device in the related technologies, and the dashed line represents the electrochemical device provided in the embodiments of this application. Wherein: In electrochemical devices of related technologies (i.e.) Figure 5 and Figure 6 Scheme 1) The negative electrode includes a current collector and an active material layer. The current collector is coated with an active material layer on both opposite surfaces in the thickness direction. The active material is doped with 10% silicon (i.e., the silicon content accounts for 10% of the total active material). Each active material layer is provided with multiple grooves spaced apart along the winding direction. The area with grooves accounts for 90% of the total length of the negative electrode along the winding direction.

[0068] The electrochemical device described in this application (i.e.) Figure 5 and Figure 6(Scheme 2) The negative electrode 100 provided in the embodiments of this application is adopted, wherein the length of the first undoped silicon section 133 and the second undoped silicon section 153 along the winding direction X is 1 mm, and the length of the first doped silicon section 131 and the second doped silicon section 151 along the winding direction X is 3 mm. The first doped silicon section 131 and the second doped silicon section 151 are doped with 10% silicon (i.e., the silicon content accounts for 10% of the total active material). The first undoped silicon section 133 and the second undoped silicon section 153 are respectively provided with a first groove 1331 and a second groove 1531, and the area provided with the first groove 1331 and the second groove 1531 accounts for 90% of the total length of the negative electrode 100 along the winding direction X.

[0069] Given that both Scheme 1 and Scheme 2 use the same positive electrode, the same manufacturing process, and the ratio of theoretical lithium insertion capacity of the negative electrode to theoretical lithium extraction capacity of the positive electrode (Cell Balance value, CB value) is 1.05, from Figure 5 The K-value histogram clearly shows that the K-value of the electrochemical device in Scheme 2 is significantly lower than that in Scheme 1. A lower K-value indicates a lower risk of self-discharge, suggesting that the electrochemical device in this embodiment has a lower risk of self-discharge and better performance. Figure 6 The capacity histogram clearly shows that the capacity of the electrochemical device in Scheme 2 is significantly higher than that in Scheme 1, further demonstrating that the electrochemical device provided in this application has superior performance. Therefore, the experimental results show that the electrochemical device using the negative electrode 100 provided in this application has a lower K value and a higher capacity, indicating superior performance.

[0070] In the negative electrode 100, electrochemical device, and electronic device provided in this application embodiment, the active material layer is provided with multiple first silicon-doped sections 131 and multiple first undoped sections 133. Thus, by providing the first silicon-doped sections 131, the lithium storage capacity of the negative electrode 100 is improved, thereby increasing the energy density of the electrochemical device. By providing at least one first groove 1331 in at least one first undoped section 133, the first groove 1331 can shorten the lithium-ion migration path, thereby improving the charging rate of the electrochemical device. Furthermore, since the first groove 1331 is located in the first undoped section 133, the reduction in silicon content due to its location in the first silicon-doped section 131 can be avoided, thus preventing a decrease in the energy density of the electrochemical device. It also prevents the crushing of silicon-carbon particles during the processing of the first groove 1331 in the first silicon-doped section 131, thereby helping to prevent the free accumulation of silicon-carbon particles in the pores of the separator, and thus reducing the risk of self-discharge of the electrochemical device.

[0071] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention. Furthermore, the embodiments of the present invention and the features thereof can be combined with each other unless otherwise specified.

Claims

1. A negative electrode sheet, characterized in that, include: The current collector has a first surface on one side along the thickness direction; The first active material layer includes a plurality of first silicon-doped segments and a plurality of first undoped segments, both of which are connected to the first surface, and at least one of the first undoped segments is provided with at least one first groove.

2. The negative electrode sheet according to claim 1, characterized in that, The first undoped silicon segment has a first edge and a second edge spaced apart from each other along the width direction of the negative electrode sheet; The opening of the first groove is located on the surface of the first undoped silicon section facing away from the current collector; The first groove extends along the width direction and passes through at least one of the first edge and the second edge.

3. The negative electrode sheet according to claim 2, characterized in that, Along the winding direction of the negative electrode sheet, the width of the first groove is ≥30 micrometers and ≤90 micrometers.

4. The negative electrode sheet according to claim 2, characterized in that, The thickness of the first undoped silicon segment along the thickness direction is 30% ≤ the depth of the first groove extending from its opening along the thickness direction toward the current collector is ≤ 70% of the thickness of the first undoped silicon segment along the thickness direction.

5. The negative electrode sheet according to claim 1, characterized in that, The first silicon-doped segment and the first undoped segment are alternately distributed along the winding direction of the negative electrode sheet; along the winding direction, the length of the first undoped segment / the length of the first silicon-doped segment is ≥1 / 10 and ≤1 / 2.

6. The negative electrode sheet according to claim 5, characterized in that, Along the winding direction, the length of the first undoped silicon segment is ≥0.5 mm and ≤1 mm; And / or, along the winding direction, the length of the first silicon-doped segment is ≥1 mm and ≤5 mm.

7. The negative electrode sheet according to any one of claims 1 to 6, characterized in that, The current collector also has a second surface on the side opposite to the first surface along the thickness direction; The negative electrode also includes a second active material layer, which includes a plurality of second silicon-doped segments and a plurality of second undoped segments. The second silicon-doped segments and the second undoped segments are both connected to the second surface and are alternately distributed along the winding direction of the negative electrode.

8. The negative electrode sheet according to claim 7, characterized in that, At least one of the second undoped silicon segments is provided with at least one second groove.

9. An electrochemical device, characterized in that, The device includes an electrode assembly comprising a positive electrode sheet, a negative electrode sheet according to any one of claims 1 to 8, and a separator disposed between the positive electrode sheet and the negative electrode sheet, wherein the positive electrode sheet, the separator and the negative electrode sheet are stacked and wound into a core structure along the winding direction.

10. An electronic device, characterized in that, Includes the electrochemical device according to claim 9.

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