Lithium ion battery and preparation method thereof

Abstract

The invention provides a lithium ion battery and a preparation method thereof in order to solve the problems of high temperature rise, high current density, lithium ion accumulation and lithium separation in the position, close to a negative tab, of a single-sided area of a battery negative electrode in the prior art. The lithium ion battery comprises a positive plate and a negative plate, wherein each of the positive plate and the negative plate comprises a current collector and an active material layer; the part, provided with the negative tab, of the negative plate is a negative tab connecting part; an etching region is formed on at least one of the active material layer adjacent to the negative tab connecting part on the negative plate and the active material layer opposite to the negative tab connecting part on the positive plate, and a plurality of etching grooves are formed in the active material layer of the etching region. According to the invention, the etching region with the plurality of etching grooves is arranged on the positive plate to reduce the separation of lithium ions from the positive electrode adjacent to the negative tab connecting part, or the etching region is arranged on the negative plate to provide a rapid embedding channel for the lithium ions from the negative electrode adjacent to the negative tab connecting part, so that the lithium separation risk is reduced; and the cycle performance and the safety of the lithium ion battery are improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium ion batteries, and in particular relates to a lithium ion battery and a preparation method thereof. Background Art

[0002] The current mobile phone battery industry has increasingly higher requirements for battery energy density. The coating surface density of the negative electrode has increased, the dynamics of the battery system has decreased, and the battery capacity has become higher and higher. The charging temperature has increased, and the temperature near the cell tabs (the single-sided area of ​​the negative electrode in the conventional structure) has increased, resulting in an increase in current density near the tabs. The negative electrode cannot be embedded with lithium in time, and lithium ions undergo side reactions on the surface of the negative electrode to form by-products. The closer to the tab, the more by-products there are, resulting in the loss of active lithium ions, reduced battery capacity, reduced cycle performance, and reduced safety performance.

[0003] The main reason for the generation of side reaction products in the single-sided area of ​​the conventional structure negative electrode is the insufficient kinetics on the negative electrode side of the battery system. The existing technology mainly improves the system kinetics through the following methods: reducing the negative electrode coating surface density, increasing the diaphragm porosity, improving the electrolyte kinetics and reducing the positive electrode kinetics. However, the existing methods all have disadvantages. The reduction in the negative electrode surface density will reduce the corresponding battery capacity and the battery energy density; increasing the diaphragm porosity will reduce the battery safety performance; improving the electrolyte kinetics will reduce the battery safety and storage performance; reducing the positive electrode kinetics will reduce the high-temperature cycle performance of the battery. How to improve the lithium insertion capacity of the negative electrode without sacrificing the battery energy density is the main problem that needs to be solved at present. Summary of the invention

[0004] Aiming at the problem that the temperature of the single-sided area of ​​the negative electrode of the battery near the negative electrode ear rises and the current density is large in the prior art, lithium ions are easily accumulated in this area and lithium precipitation occurs, a lithium ion battery and a preparation method thereof are provided.

[0005] The technical solution adopted by the present invention to solve the above technical problems is as follows: In one aspect, the present invention provides a lithium ion battery, comprising a positive electrode sheet, a negative electrode sheet, and a separator arranged between the positive electrode sheet and the negative electrode sheet, wherein the positive electrode sheet, the negative electrode sheet and the separator are stacked or wound to form a pole core; The positive electrode sheet and the negative electrode sheet each include a current collector and an active material layer disposed on the surface of the current collector; The positive electrode sheet further comprises a positive electrode ear connected to the current collector thereof, and the negative electrode sheet further comprises a negative electrode ear connected to the current collector thereof; The portion of the negative electrode sheet where the negative electrode ear is provided is a negative electrode ear connecting portion; An etching area is formed on the active material layer adjacent to the negative electrode tab connection portion on the negative electrode sheet, or on the active material layer opposite to the negative electrode tab connection portion on the positive electrode sheet; a plurality of etching grooves are arranged on the active material layer in the etching area.

[0006] Optionally, the etching region includes a first negative electrode etching region formed on the negative electrode sheet, the first negative electrode etching region and the negative electrode ear are located on the same side of the negative electrode sheet, and the first negative electrode etching region is located in a region of the active material layer adjacent to the negative electrode ear connection portion; or, The etching region includes a second negative electrode etching region formed on the negative electrode sheet, the second negative electrode etching region and the negative electrode tab are respectively located on both sides of the negative electrode sheet, and the second negative electrode etching region is located in a region of the active material layer adjacent to the negative electrode tab connection portion.

[0007] Optionally, the first negative electrode etching region includes a plurality of etching grooves distributed in a direction gradually away from the middle of the negative electrode ear connecting portion; and / or, The second negative electrode etching region includes a plurality of etching grooves distributed along a direction gradually away from the middle of the negative electrode ear connecting portion.

[0008] Optionally, the etching region includes a first positive electrode etching region formed on the positive electrode sheet; the first positive electrode etching region faces a side of the negative electrode sheet where the negative electrode ear is provided; and / or, The etching region includes a second positive electrode etching region formed on the positive electrode sheet, and the second positive electrode etching region faces a side of the negative electrode sheet away from the negative electrode ear.

[0009] Optionally, the portion of the positive electrode sheet opposite to the negative electrode ear connecting portion is the negative electrode ear alignment portion; The first positive electrode etching region includes a plurality of etching grooves distributed in a direction gradually away from the negative electrode ear alignment portion; and / or, The second positive electrode etching region includes a plurality of etching grooves distributed along a direction gradually away from the negative electrode ear alignment portion.

[0010] Optionally, the first positive electrode etching region and / or the second positive electrode etching region further includes a plurality of etching grooves arranged on the active material layer at the negative electrode ear alignment portion.

[0011] Optionally, a pole piece adhesive tape is provided on a side of the positive pole sheet facing the negative pole ear, and / or on a side of the positive pole sheet facing the negative pole sheet and away from the negative pole ear; the pole piece adhesive tape is directly opposite to the negative pole ear.

[0012] Optionally, a plurality of etching grooves are arranged in parallel and at intervals on the active material layer of the corresponding etching area.

[0013] Optionally, the extension direction of the plurality of etching grooves is parallel to or coincides with the extension direction of the negative electrode ear.

[0014] Optionally, in the lithium-ion battery, the length direction of the etched area is consistent with the width direction of the negative electrode ear, and the width direction of the etched area is consistent with the length direction of the negative electrode ear; The etching groove penetrates the active material layer and extends along one side or both sides of the negative electrode ear in the extension direction.

[0015] Optionally, on the negative electrode sheet or the positive electrode sheet: the length of the etching area is 50 mm to 300 mm, and the width of the etching area is 20 mm to 150 mm.

[0016] Optionally, along a direction away from the negative electrode ear connecting portion, a width of at least one of the etched regions gradually decreases.

[0017] Optionally, the maximum width of the etching area is 25 mm to 85 mm.

[0018] Optionally, along a direction away from the middle of the negative electrode ear connecting portion, the width of the plurality of etching grooves of at least one of the etching regions in the direction in which the length of the electrode piece extends gradually decreases.

[0019] Optionally, the width of the etched groove is 50 μm to 200 μm.

[0020] Optionally, along a direction away from the middle of the negative electrode tab connecting portion, the depth of the plurality of etching grooves of at least one of the etching regions in the thickness direction of the electrode sheet gradually decreases.

[0021] Optionally, the depth of the etched groove is 8 μm to 60 μm.

[0022] Optionally, the negative electrode tab is located at an end of the current collector, or the negative electrode tab is located between two ends of the current collector.

[0023] In another aspect, the present invention provides a method for preparing a lithium ion battery, comprising the following operations: Obtain a negative electrode sheet precursor and the positive electrode sheet without the etching area; or obtain a positive electrode sheet precursor and the negative electrode sheet without the etching area; The negative electrode sheet precursor comprises the corresponding current collector, the negative electrode ear integrally connected to the current collector, and the active material layer coated on the current collector; a plurality of etching grooves are formed on the active material layer of the negative electrode sheet precursor; and the negative electrode sheet is obtained; or, The negative electrode sheet precursor comprises the corresponding current collector, the active material layer coated on the current collector, and the current collector is provided with a negative electrode empty foil area without the active material layer; a plurality of etching grooves are formed by etching the active material layer of the negative electrode sheet precursor; the negative electrode ear is welded on the negative electrode empty foil area; and the negative electrode sheet is obtained; or, The negative electrode sheet precursor comprises the corresponding current collector and the active material layer coated on the current collector on its entire surface; cleaning part of the active material layer of the negative electrode sheet precursor to expose the negative electrode hollow foil area; etching the active material layer of the negative electrode sheet precursor to form a plurality of etching grooves; welding the negative electrode ear on the negative electrode hollow foil area; obtaining the negative electrode sheet; The positive electrode sheet precursor comprises the corresponding current collector, the positive electrode ear integrally connected to the current collector, and the active material layer coated on the current collector; a plurality of etching grooves are formed on the active material layer of the positive electrode sheet precursor; and the positive electrode sheet is obtained; or, The positive electrode sheet precursor comprises the corresponding current collector, the active material layer coated on the current collector, and the current collector is provided with a positive electrode empty foil area without the active material layer; a plurality of etching grooves are formed by etching the active material layer of the positive electrode sheet precursor; the positive electrode ear is welded on the positive electrode empty foil area; and the positive electrode sheet is obtained; or, The positive electrode sheet precursor comprises the corresponding current collector and the active material layer coated on the current collector on its entire surface; cleaning part of the active material layer of the positive electrode sheet precursor to expose the positive electrode hollow foil area; etching the active material layer of the positive electrode sheet precursor to form a plurality of etching grooves; welding the positive electrode ear on the positive electrode hollow foil area; obtaining the positive electrode sheet; obtaining the diaphragm; The positive electrode sheet, the negative electrode sheet, and the separator are stacked or wound to form the electrode core.

[0024] Optionally, the etching method is laser etching.

[0025] The beneficial effects of the present invention are: The lithium ion battery provided by the present invention forms an etching area with multiple etching grooves on the active material layer adjacent to the negative electrode ear connection part on the negative electrode sheet or the active material layer opposite to the negative electrode ear connection part on the positive electrode sheet. The etching grooves on the negative electrode sheet are used to provide embedding sites and channels for the embedding of lithium ions in the negative electrode, so that the lithium ions can be quickly embedded in the negative electrode active material layer, and the negative electrode dynamics and the lithium embedding capacity of the negative electrode can be improved. Alternatively, the etching grooves on the positive electrode sheet can be used to reduce the escape of lithium ions from the positive electrode adjacent to the negative electrode ear connection part, thereby avoiding the accumulation of lithium ions at the negative electrode ear position, reducing the risk of lithium plating, and improving the cycle performance and safety of the lithium ion battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 is a schematic diagram of the structure of a negative electrode sheet provided by an embodiment of the present invention; Figure 2 is a schematic diagram of the cross-sectional structure of a negative electrode sheet provided by an embodiment of the present invention; Figure 3 is a schematic diagram of the structure of a negative electrode sheet provided by another embodiment of the present invention; Figure 4 is a schematic diagram of a cross-sectional structure of a negative electrode sheet provided by another embodiment of the present invention; Figure 5 is a schematic diagram of the structure of a negative electrode sheet provided by another embodiment of the present invention; Figure 6 is a schematic diagram of a cross-sectional structure of a negative electrode sheet provided by another embodiment of the present invention; Figure 7 is another structural schematic diagram of a negative electrode sheet provided by another embodiment of the present invention; Figure 8 is another schematic diagram of a cross-sectional structure of a negative electrode sheet provided by another embodiment of the present invention; Fig. 9 is a schematic diagram of the structure of a negative electrode sheet provided by another embodiment of the present invention; Fig.10 is a schematic diagram of a cross-sectional structure of a negative electrode sheet provided by another embodiment of the present invention; Fig.11 is another structural schematic diagram of a negative electrode sheet provided by another embodiment of the present invention; Fig.12 is a schematic diagram of the structure of a positive electrode sheet provided by an embodiment of the present invention; Fig.13 is a schematic diagram of the cross-sectional structure of a positive electrode sheet provided by an embodiment of the present invention; Fig.14 is another structural schematic diagram of a positive electrode sheet provided by another embodiment of the present invention; Fig.15 is another schematic diagram of a cross-sectional structure of a positive electrode sheet provided by another embodiment of the present invention; Fig.16 is a schematic diagram of the structure of a positive electrode sheet provided by another embodiment of the present invention; Fig.17 is a schematic diagram of a cross-sectional structure of a positive electrode sheet provided by another embodiment of the present invention; Fig.18 is a schematic diagram of the structure of a positive electrode sheet provided by an embodiment of the present invention; Fig.19 is a schematic diagram of the cross-sectional structure of a positive electrode sheet provided by an embodiment of the present invention; Fig. 20 is another structural schematic diagram of a positive electrode sheet provided by another embodiment of the present invention; Fig.21 is another schematic diagram of a cross-sectional structure of a positive electrode sheet provided by another embodiment of the present invention; Fig. 22 is a schematic diagram of the structure of a positive electrode sheet provided by another embodiment of the present invention; Fig.23 It is a schematic diagram of the cross-sectional structure of a positive electrode sheet provided in another embodiment of the present invention.

[0027] The reference numerals in the drawings of the specification are as follows: 1. Current collector; 11. Active material layer; 12. Etching area; 121. Etching groove; 2. Pole piece adhesive tape; 3. Positive electrode sheet; 31. Positive electrode ear; 32. First positive electrode etching area; 33. Second positive electrode etching area; 4. Negative electrode sheet; 41. Negative electrode ear; 42. First negative electrode etching area; 43. Second negative electrode etching area. DETAILED DESCRIPTION

[0028] In order to make the technical problems, technical solutions and beneficial effects solved by the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0029] In the description of the present invention, it should be understood that the terms "longitudinal", "radial", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In the description of the present invention, unless otherwise specified, "plurality" means two or more.

[0030] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0031] Reference Figures 1 to 23 On the one hand, the present invention provides a lithium ion battery, comprising a positive electrode sheet 3, a negative electrode sheet 4, and a separator arranged between the positive electrode sheet 3 and the negative electrode sheet 4, wherein the positive electrode sheet 3, the negative electrode sheet 4 and the separator are stacked or wound to form a pole core; The positive electrode sheet 3 and the negative electrode sheet 4 both include a current collector 1 and an active material layer 11 disposed on the surface of the current collector 1; specifically, the current collector 1 of the positive electrode sheet 3 is a positive electrode current collector, the active material layer 11 of the positive electrode sheet 3 is a positive electrode active material layer, the current collector 1 of the negative electrode sheet 4 is a negative electrode current collector, and the active material layer 11 of the negative electrode sheet 4 is a negative electrode active material layer; The positive electrode sheet 3 further includes a positive electrode ear 31 connected to its current collector 1 (i.e., the positive electrode current collector), and the negative electrode sheet 4 further includes a negative electrode ear 41 connected to its current collector 1 (i.e., the negative electrode current collector); The portion of the negative electrode sheet 4 where the negative electrode ear 41 is provided is the negative electrode ear connection portion; the negative electrode ear connection portion corresponds to the negative electrode ear 41 one by one; specifically, if the negative electrode sheet 4 is provided with one negative electrode ear 41, then the negative electrode sheet has one negative electrode ear connection portion, and if the negative electrode sheet 4 is provided with multiple negative electrode ears 41, then the negative electrode sheet has multiple negative electrode ear connection portions; An etching area 12 is formed on the active material layer 11 (i.e., the negative electrode active material layer) adjacent to the negative electrode ear connection portion on the negative electrode sheet 4 or on the active material layer 11 (positive electrode active material layer) opposite to the negative electrode ear connection portion on the positive electrode sheet 3; a plurality of etching grooves 121 are provided on the active material layer 11 of the etching area 12.

[0032] It should be noted that the temperature near the negative electrode ear 41 of the battery rises, the current density is large, and lithium ions accumulate near the negative electrode ear 41. The lithium ions will undergo side reactions on the negative electrode surface to form byproducts or lithium precipitation. Therefore, it is necessary to allow the lithium ions accumulated on the negative electrode surface to be quickly embedded in the negative electrode, or to reduce the release of lithium ions on the positive electrode near the negative electrode ear.

[0033] Etching is a process that forms specific patterns or textures on the surface of a material. By creating holes or grooves with a high specific surface area on the electrode, the surface properties of the material can be improved and its functionality can be increased. In the production of battery electrode sheets, etching can be used to increase the surface area of ​​the active material and improve its contact efficiency with the electrolyte, thereby improving the overall performance of the battery.

[0034] The lithium ion battery provided by the present invention comprises a positive electrode sheet 3 and a negative electrode sheet 4, and both the positive electrode sheet 3 and the negative electrode sheet 4 comprise a current collector 1 and an active material layer 11; like Figures 1 to 11, an etched area 12 may be formed on the active material layer 11 adjacent to the negative electrode ear connection portion on the negative electrode sheet 4, and a plurality of etched grooves 121 may be provided on the active material layer 11 of the etched area 12. By providing the etched area 12 and providing a plurality of etched grooves 121 on the active material layer 11 of the etched area 12, the etched grooves 121 are used to provide embedding sites and channels for the embedding of lithium ions in the negative electrode, so that lithium ions can be quickly embedded into the negative electrode active material layer, and the negative electrode kinetics and the lithium embedding capacity of the negative electrode can also be improved. The above-mentioned arrangement avoids the accumulation of lithium ions at the position of the negative electrode ear 41, reduces the risk of lithium precipitation, and ensures that the cycle performance and safety of the lithium ion battery are improved without reducing the energy density of the lithium ion battery as much as possible.

[0035] like Figures 12 to 23 , or an etching area 12 is formed on the active material layer 11 on the positive electrode sheet 3 opposite to the negative electrode ear connection portion, and a plurality of etching grooves 121 are provided on the active material layer 11 of the etching area 12. By providing the etching area 12 and providing a plurality of etching grooves 121 on the active material layer 11 of the etching area 12, it is beneficial to reduce the release of lithium ions from the positive electrode near the negative electrode ear 41, avoid the accumulation of lithium ions at the position of the negative electrode ear 41, reduce the risk of lithium precipitation, and ensure that the cycle performance and safety of the lithium ion battery are improved without reducing the energy density of the lithium ion battery as much as possible; Reference Figure 1~2 , Figures 5 and 6 and Figures 10-11 , Figure 3 and Figure 7 ; and reference Figure 4 , Figure 8-9 In some embodiments, the etching region 12 includes a first negative electrode etching region 42 formed on the negative electrode sheet 4, the first negative electrode etching region 42 and the negative electrode ear 41 are located on the same side of the negative electrode sheet 4, and the first negative electrode etching region 42 is located in the region adjacent to the negative electrode ear connection portion of the active material layer 11; Reference Figure 4 as well as Figures 8 and 9 The etching region 12 includes a second negative electrode etching region 43 formed on the negative electrode sheet 4. The second negative electrode etching region 43 and the negative electrode ear 41 are respectively located on both sides of the negative electrode sheet 4. The second negative electrode etching region 43 is located in the region adjacent to the negative electrode ear connection portion of the active material layer 11.

[0036] Specifically, the first negative electrode etching region 42 and the negative electrode ear 41 are located on the same side of the negative electrode sheet 4, and the first negative electrode etching region 42 is located in the region of the active material layer 11 adjacent to the negative electrode ear connection portion. During the charging process, when lithium ions are released from the positive electrode, they can quickly find an embedding site and enter the negative electrode active material. Due to the presence of the etching groove 121, lithium ions can more easily penetrate the active material layer 11, reducing the accumulation of lithium ions near the negative electrode ear 41, thereby reducing the risk of lithium precipitation. When the second negative electrode etching area 43 and the negative electrode ear 41 are respectively arranged on both sides of the negative electrode sheet 4, the second negative electrode etching area 43 is located in the area of ​​the active material layer 11 adjacent to the negative electrode ear connection portion. By arranging etching areas 12 on both sides of the negative electrode sheet 4, the flow path of lithium ions can be further dispersed, reducing stress and lithium deposition in local areas, which helps to improve the overall performance and life of the battery.

[0037] In some embodiments, the first cathode etched region 42 includes a plurality of etched grooves 121 distributed in a direction gradually away from the middle of the cathode tab connecting portion.

[0038] In some embodiments, the second cathode etched region 43 includes a plurality of etched grooves 121 distributed in a direction gradually away from the middle of the cathode tab connecting portion.

[0039] Specifically, the etching grooves 121 of the first negative electrode etching zone 42 are distributed in a direction gradually away from the middle of the negative electrode ear connection part, which helps to gradually guide the lithium ions to move and embed into the interior of the negative electrode sheet 4 starting from the vicinity of the negative electrode ear 41. Similarly, the etching grooves 121 of the second negative electrode etching zone 43 are distributed in a direction gradually away from the middle of the negative electrode ear connection part. By utilizing the bidirectional distribution of the etching grooves 121 of the first negative electrode etching zone 42 and the etching grooves 121 of the second negative electrode etching zone 43, the lithium ions can be more evenly dispersed, and the concentrated deposition near the negative electrode ear 41 can be reduced, thereby reducing the risk of lithium plating and further enhancing the cycle stability and safety of the battery.

[0040] Reference Figures 12 to 17 In some embodiments, the etching region 12 may include a first positive electrode etching region 32 formed on the positive electrode sheet 3; the first positive electrode etching region 32 faces a side of the negative electrode sheet 4 where the negative electrode ear 41 is provided; Reference Figures 18 to 22 In some embodiments, the etching region 12 may include a second positive electrode etching region 33 formed on the positive electrode sheet 3, the second positive electrode etching region 33 facing the side of the negative electrode sheet 4 away from the negative electrode ear 41; Preferably, the etching zone 12 may include the above-mentioned first positive electrode etching zone 32 and the second positive electrode etching zone 33 at the same time, and the first positive electrode etching zone 32 and the second positive electrode etching zone 33 are respectively arranged on two layers of positive electrode sheets 3 adjacent to the negative electrode ear connection part, specifically, it can be two positive electrode sheets 3 stacked in a stacked electrode core or a wound electrode core, with two positive electrode sheets 3 wound on the layers.

[0041] Specifically, a first positive electrode etching area 32 is provided on the positive electrode sheet 3 and faces the side of the negative electrode sheet 4 where the negative electrode ear 41 is provided, so that lithium ions are reduced from escaping from the positive electrode sheet 3 and moving to the negative electrode active layer near the negative electrode ear 41 for accumulation, thereby reducing the risk of lithium plating; in addition, when the etching area 12 also includes a second positive electrode etching area 33 provided on the side of the negative electrode sheet 4 away from the negative electrode ear 41, lithium ions are reduced from escaping from the positive electrode sheet 3 and moving to the negative electrode active layer near the negative electrode ear 41 for accumulation, thereby reducing the risk of lithium plating; thereby, the cycle stability and safety of the battery are improved by alleviating or inhibiting lithium plating.

[0042] In some embodiments, the portion of the positive electrode sheet 3 opposite to the negative electrode ear connection portion is the negative electrode ear alignment portion; The first positive electrode etching area 32 includes a plurality of etching grooves 121 distributed in a direction gradually away from the middle of the negative electrode ear alignment portion; reducing the de-lithiation of the positive electrode to the negative electrode active material layer within a certain range near the negative electrode ear, avoiding the accumulation of lithium ions on the negative electrode active layer near the negative electrode ear 41, thereby reducing the risk of lithium plating.

[0043] In some embodiments, the portion on the positive electrode sheet 3 opposite to the negative electrode ear connection portion is the negative electrode ear alignment portion; the second positive electrode etching area 33 includes a plurality of etching grooves 121 distributed in a direction gradually away from the middle of the negative electrode ear alignment portion; the delithiation of the positive electrode is reduced to the negative electrode active material layer within a certain range near the negative electrode ear, and the accumulation of lithium ions on the negative electrode active layer near the negative electrode ear 41 is avoided, thereby reducing the risk of lithium plating.

[0044] In some embodiments, a pole piece adhesive tape 2 is provided on the side of the positive electrode sheet 3 facing the negative electrode ear 41; or, a pole piece adhesive tape 2 is provided on the side of the positive electrode sheet 3 facing the negative electrode sheet 4 and away from the negative electrode ear 41; or, a pole piece adhesive tape 2 is provided on the side of the positive electrode sheet 3 facing the negative electrode ear 41 and on the side of the positive electrode sheet 3 facing the negative electrode sheet 4 and away from the negative electrode ear 41; The electrode tape 2 faces the negative electrode ear 41 .

[0045] Specifically, the electrode tape 2 is arranged on the side of the positive electrode sheet 3 facing the negative electrode ear 41, which not only plays a corresponding insulating role, but also can enhance the adhesion between the electrodes, improve the structural integrity of the battery, and reduce the electrode damage caused by local stress concentration; The electrode tape 2 is arranged on the side of the positive electrode sheet 3 facing the negative electrode sheet 4 away from the negative electrode ear 41, which also helps to enhance the structural integrity of the electrode and ensure that the battery remains stable during the charging and discharging process.

[0046] The configuration of the electrode tape 2 facing the negative electrode ear 41 helps to enhance the structural stability of the battery and prevent relative movement between electrode layers.

[0047] In some embodiments, a plurality of etching grooves 121 are disposed in parallel and spaced apart on the active material layer 11 of the corresponding etching region 12 .

[0048] Specifically, the etching grooves 121 are arranged in parallel and at intervals on the active material layer 11 of the corresponding etching area 12, which helps to ensure the uniform transmission of lithium ions on the electrode and reduce local stress concentration, thereby improving the cycle stability and safety of the battery.

[0049] In some embodiments, the extending direction of the etched groove 121 is parallel to the extending direction of the negative electrode tab 41 .

[0050] Specifically, the extension direction of the etching groove 121 is parallel to the extension direction of the negative electrode ear 41, which is conducive to the rapid embedding of lithium ions at the position of the negative electrode ear 41 through the etching groove 121, improving the accumulation of lithium ions at the position of the negative electrode ear 41, or reducing the escape of lithium ions from the positive electrode near the negative electrode ear 41, thereby avoiding the accumulation of lithium ions at the position of the negative electrode ear 41.

[0051] In some embodiments, the length direction of the etched region 12 is consistent with the width direction of the negative electrode ear 41 , and the width direction of the etched region 12 is consistent with the length direction of the negative electrode ear 41 ; The etched groove 121 penetrates one side or both sides of the active material layer 11 along the extending direction of the negative electrode tab 41 .

[0052] In some embodiments, on the negative electrode sheet 4 or the positive electrode sheet 3 , the length of the etched area 12 is 50 mm to 300 mm, and the width of the etched area 12 is 20 mm to 150 mm.

[0053] Specifically, the length of the etching area 12 may be 50 mm, 80 mm, 100 mm, 120 mm, 150 mm, 180 mm, 230 mm, 280 mm or 300 mm; The width of the etching area 12 may be 20 mm, 25 mm, 50 mm, 60 mm, 75 mm, 85 mm, 100 mm, 110 mm, 120 mm, 130 mm or 150 mm. In a preferred embodiment, the length of the etching area 12 may be set to 120 mm.

[0054] In some embodiments, Figure 1 , Figure 3 , Fig.14 and Fig.18 , along the direction away from the middle of the negative electrode ear connecting portion, the width of at least one etched area 12 gradually decreases.

[0055] Specifically, when the negative electrode ear connection portion is located at the end of the negative electrode sheet 4, the width of the etched area 12 on at least one side of the negative electrode sheet 4 can be gradually reduced (eg Figure 1As shown in FIG. 1 ), the width of the etched area 12 on at least one side of the positive electrode sheet 3 may also be gradually reduced (as shown in FIG. 1 ). Fig.14 shown); Specifically, when the negative electrode ear connection portion is located between the two ends of the negative electrode sheet 4, the negative electrode ear connection portion has an active material layer on both sides of the negative electrode ear width direction. The width of the etched area 12 on at least one side of the negative electrode sheet 4 can be set to be the largest in the middle area in the width direction facing the negative electrode ear, and the width of the etched area 12 gradually decreases in the direction away from the middle of the negative electrode ear connection portion toward the two ends of the negative electrode sheet 4 (such as Figure 3 As shown), the width of the etched area 12 on at least one side of the positive electrode sheet 3 may be set to be the largest in the middle area in the width direction opposite to the negative electrode ear, and the width of the etched area 12 gradually decreases in the direction away from the middle of the negative electrode ear toward the two ends of the positive electrode sheet 3 (as shown Fig.18 as shown).

[0056] Specifically, it should be noted that the closer the negative electrode active material layer area is to the negative electrode ear connection part, the easier it is to deposit lithium. If the width, length and depth of the etching groove of each part of the etching area are set to the same, the etching may damage the structural integrity of the electrode sheet, causing the positive electrode sheet 3 or the negative electrode sheet 4 to be more easily deformed or broken under mechanical stress. In addition, in the battery, the electrochemical properties of the positive electrode sheet 3 or the negative electrode sheet 4 depend on its surface area and the distribution of active materials. If the width, length and depth of the etching groove of each part of the etching area are set to the same, the battery's charge and discharge efficiency, cycle stability, and energy density will be reduced.

[0057] Specifically, along the direction away from the middle of the negative electrode ear connection, the width of at least one etching area 12 is gradually reduced. On the one hand, the etching groove 121 set on the etching area 12 of the positive electrode sheet 3 can reduce the escape of positive electrode lithium ions adjacent to the negative electrode ear connection. On the other hand, the etching groove 121 set on the etching area 12 of the negative electrode sheet 4 can provide sufficient lithium insertion channels and sites for lithium ions near the negative electrode ear 41, thereby avoiding the accumulation of lithium ions near the negative electrode ear 41 and causing lithium precipitation. At the same time, the mechanical strength and lithium insertion capacity of the positive electrode sheet 3 or the negative electrode sheet 4 are guaranteed, thereby avoiding deformation or breakage of the positive electrode sheet 3 or the negative electrode sheet 4 due to the setting of the etching area 12, or affecting the energy density of the lithium-ion battery.

[0058] In some embodiments, the maximum width of the etched region 12 is 25 mm to 85 mm.

[0059] Specifically, the maximum width of the etched area 12 may be 25 mm, 50 mm, 60 mm, 75 mm, 83 mm or 85 mm; like Figure 1~2 as well as Figures 14 and 15As shown, in some embodiments of the present application, the negative electrode ear 41 or the positive electrode ear 31 is arranged at one end of the current collector 1, and an etching area 12 is arranged near the negative electrode ear connection portion or the negative electrode ear alignment portion, and the etching area 12 extends along the length direction of the current collector 1 to a position away from the negative electrode ear connection portion. At this time, the width of the etching area 12 decreases proportionally from the maximum width (for example, 25 mm) to 0, and the width and depth of all etching grooves 121 of the etching area 12 are the same; like Figure 3~4 as well as Figures 18 and 19 As shown, in some other embodiments of the present application, the negative electrode ear 41 is arranged between the two ends of the current collector 1, and along the length direction of the current collector 1, the etching zone 12 extends from the middle of the negative electrode ear connection part or the middle of the negative electrode ear counter-position part to a position away from the middle of the electrode ear connection part or the middle of the negative electrode ear counter-position part, respectively. At this time, the width of the etching zone 12 decreases proportionally from the maximum width (for example, 25 mm) to 0, and the width and depth of all etching grooves 121 in the etching zone 12 are the same.

[0060] In some embodiments, along the direction away from the middle of the negative electrode tab connection portion, the width of the plurality of etching grooves 121 of at least one etching region 12 gradually decreases in the direction in which the length of the electrode piece extends.

[0061] Specifically, when the negative electrode ear connection portion is located at the end of the negative electrode sheet 4, the width of the multiple etching grooves 121 of the etching area 12 on at least one side of the negative electrode sheet 4 can be gradually reduced in the extension direction of the length of the electrode sheet (such as Fig.11 As shown), the width of the multiple etching grooves 121 of the etching area 12 on at least one side of the positive electrode sheet 3 can also be gradually reduced in the extension direction of the length of the electrode sheet (as shown in Fig.17 shown); Specifically, when the negative electrode ear connection portion is located between the two ends of the negative electrode sheet 4, the negative electrode ear connection portion has an active material layer on both sides of the negative electrode ear width direction. The width of the etching area 12 on at least one side of the negative electrode sheet 4 can be set to be the largest in the middle area in the width direction facing the negative electrode ear, and the width of the multiple etching grooves 121 of the etching area 12 in the extension direction of the electrode sheet length gradually decreases in the direction away from the middle of the negative electrode ear connection portion toward the two ends of the negative electrode sheet 4 (such as Fig. 9 As shown), the width of the etching area 12 on at least one side of the positive electrode sheet 3 can also be set to be the largest in the middle area in the width direction opposite to the negative electrode ear, and the width of the multiple etching grooves 121 in the etching area 12 in the extension direction of the electrode length gradually decreases along the direction away from the middle of the negative electrode ear alignment portion toward the two ends of the positive electrode sheet 3 (as shown in FIG. Fig.23 as shown).

[0062] The purpose of the multiple etching grooves 121 set in the etching area 12 is to improve the problem of lithium plating caused by the accumulation of lithium ions near the negative electrode ear. Along the direction away from the middle of the negative electrode ear connection, the width of the multiple etching grooves 121 of at least one etching area 12 in the extension direction of the electrode length gradually decreases. Conversely, the closer to the middle of the negative electrode ear connection, the greater the width of the etching groove 121, which is conducive to ensuring that the positive electrode sheet 3 passes through the etching groove 121 with a larger width, reducing the escape of lithium ions on the positive electrode active material layer closer to the negative electrode ear connection, and ensuring that the negative electrode sheet 4 passes through the etching groove 121 with a larger width, providing sufficient embedding channels for the embedding of lithium ions in the positive electrode active material layer closer to the negative electrode ear connection, thereby avoiding the accumulation of lithium ions at the negative electrode ear position, reducing the risk of lithium plating, and ensuring that the cycle performance and safety of the lithium ion battery are improved without reducing the energy density of the lithium ion battery.

[0063] In some embodiments, the width of the etched groove 121 is 50 μm-200 μm.

[0064] Specifically, the width of the etched groove 121 may be 50 μm, 80 μm, 100 μm, 120 μm, 150 μm, 180 μm or 200 μm.

[0065] In some embodiments of the present application, Figure 2 , Figure 4 , Figure 6 , Figure 8 as well as Fig.12 , Fig.14 , Fig.18 as well as Fig.21 As shown, regardless of whether the positive electrode ear 31 or the negative electrode ear 41 is arranged in the middle of the current collector 1 or the positive electrode ear 31 and the negative electrode ear 41 are arranged at the end of the current collector 1, a plurality of etching grooves 121 are evenly distributed in the etching area 12. At this time, the widths of the plurality of etching grooves 121 in the above figure are consistent. Under the condition that the widths of the etching grooves 121 are consistent, the width of the etching grooves 121 can be 50 μm to 200 μm; as shown Fig. 9 , Fig.11 , Fig.17 as well as Fig.23 As shown, the widths of different etching grooves 121 in the multiple etching grooves 121 set in the same etching area 12 are inconsistent. At this time, the width of the etching groove 121 decreases proportionally from 200μm to 50μm. Under the condition of ensuring that the electrode has corresponding uniform stress, a suitable width is set between adjacent etching grooves 121.

[0066] In some embodiments, along a direction away from the middle of the negative electrode tab connection portion, the depth of the plurality of etching grooves 121 of at least one etching region 12 in the thickness direction of the electrode sheet gradually decreases.

[0067] Specifically, when the negative electrode ear connection portion is located at the end of the negative electrode sheet 4, the depth of the multiple etching grooves 121 of the etching area 12 on at least one side of the negative electrode sheet 4 in the thickness direction of the electrode sheet can be gradually reduced (such as Figure 6 As shown), the depth of the etching area 12 on at least one side of the positive electrode sheet 3 in the thickness direction of the electrode sheet can also be gradually reduced (as shown in FIG. Fig.13 shown); Specifically, when the negative electrode ear connection portion is located between the two ends of the negative electrode sheet 4, the negative electrode ear connection portion has an active material layer on both sides of the negative electrode ear width direction. The width of the etching area 12 on at least one side of the negative electrode sheet 4 can be set to be the largest in the middle area in the width direction facing the negative electrode ear, and the depth of the multiple etching grooves 121 of the etching area 12 in the thickness direction of the electrode sheet gradually decreases in the direction away from the middle of the negative electrode ear connection portion toward the two ends of the negative electrode sheet 4 (such as Figure 8 As shown), the width of the etched area 12 on at least one side of the positive electrode sheet 3 can also be set to be the largest in the middle area in the width direction opposite to the negative electrode ear, and the depth of the etched area 12 in the thickness direction of the electrode sheet gradually decreases along the direction away from the middle of the negative electrode ear alignment portion toward the two ends of the positive electrode sheet 3 (as shown in FIG. Fig.21 as shown).

[0068] It should be noted that the negative electrode of the battery is close to the negative electrode ear 41, the temperature rises and the current density is large, and lithium ions accumulate in this area. If the negative electrode cannot be embedded with lithium in time, the lithium ions will react on the surface of the negative electrode to form by-products or lithium precipitation.

[0069] Specifically, in order to solve the problem of lithium ions reacting on the surface of the negative electrode to form by-products and lithium deposition, the present application sets an etching area 12 and an etching groove 121 in the etching area 12 to suppress excessive lithium desorption of the positive electrode and provide more lithium insertion channels and sites for the negative electrode, thereby improving lithium deposition; along the direction away from the middle of the negative electrode ear connection, the depth of the multiple etching grooves 121 in at least one etching area gradually decreases in the thickness direction of the electrode sheet. Taking the negative electrode ear 41 as a reference, by adjusting the depth of the etching grooves 121 away from and close to the negative electrode ear 41, the transmission path of lithium ions inside the battery is optimized, the diffusion impedance is reduced, and the transmission efficiency of lithium ions is improved.

[0070] In some embodiments, the depth of the etched groove 121 is 8 μm to 60 μm.

[0071] Specifically, the depth of the etched groove 121 may be 8 μm, 10 μm, 15 μm, 20 μm, 30 μm, 40 μm, 45 μm, 48 μm, 55 μm, 60 μm, 70 μm or 80 μm; Figure 6 , Figure 8 Fig.13 as well as Fig.21 As shown, Figure 6In the embodiment, along the length direction of the current collector 1, the depth of the etching groove 121 extending away from the positive electrode ear 31 or the negative electrode ear 41 gradually decreases. At this time, the depth of the etching groove 121 decreases proportionally from 60 μm to 10 μm. Figure 8 In the embodiment, the depth of the etched groove 121 is proportionally reduced from 48 μm to 8 μm.

[0072] In some embodiments, the negative electrode tab 41 is located at an end of the current collector 1 , or the negative electrode tab 41 is located between two ends of the current collector 1 .

[0073] Specifically, when the negative electrode tab 41 is located at the end of the current collector 1 , it can ensure uniform distribution of current and reduce local overheating, thereby improving the safety and cycle stability of the battery.

[0074] When the negative electrode tab 41 is located between the two ends of the current collector 1 , it helps to balance the current density inside the battery and avoid electrode damage caused by current concentration.

[0075] In another embodiment of the present invention, a method for preparing a lithium ion battery is provided, comprising the following operations: Obtaining a negative electrode sheet precursor and the positive electrode sheet 3 without the etching area 12; The negative electrode sheet precursor comprises the corresponding current collector 1, the negative electrode ear 41 integrally connected to the current collector 1, and the active material layer 11 coated on the current collector 1; a plurality of etching grooves 121 are formed by etching the active material layer 11 of the negative electrode sheet precursor; and the negative electrode sheet 4 is obtained; or, The negative electrode sheet precursor comprises the corresponding current collector 1, the active material layer 11 coated on the current collector 1, and the current collector 1 is provided with a negative electrode empty foil area without the active material layer 11; a plurality of etching grooves 121 are formed by etching the active material layer 11 of the negative electrode sheet precursor; the negative electrode ear 41 is welded on the negative electrode empty foil area; and the negative electrode sheet 4 is obtained; or, The negative electrode sheet precursor comprises the corresponding current collector 1, and the active material layer 11 coated on the entire surface of the current collector 1; cleaning a part of the active material layer 11 of the negative electrode sheet precursor to expose the negative electrode empty foil area; etching a plurality of etching grooves 121 on the active material layer 11 of the negative electrode sheet precursor; welding the negative electrode ear 41 on the negative electrode empty foil area; obtaining the negative electrode sheet 4; obtaining the diaphragm; The positive electrode sheet 3 , the negative electrode sheet 4 , and the separator are stacked or wound to form the electrode core.

[0076] Specifically, the preparation method of the above-mentioned lithium-ion battery forms a plurality of etching grooves 121 by etching on the active material layer 11 of the negative electrode sheet precursor. These etching grooves 121 provide more positions for lithium ion embedding and extraction, and more lithium ions can be accommodated inside the negative electrode instead of being accumulated near the negative electrode ear 41, which helps to reduce the risk of lithium ion precipitation near the negative electrode ear; whether the negative electrode sheet with the negative electrode ear 41 integrally connected to the current collector 1, specifically directly reserving the negative electrode ear 41 on the current collector 1 through a die-cutting process, or reserving a negative electrode empty foil area on the current collector 1 and then welding the negative electrode ear 41 on the negative electrode empty foil area, the transmission efficiency of lithium ions can be improved by providing an etching area 12 with etching grooves 121, thereby reducing the risk of local overcharge and lithium precipitation caused by poor lithium ion transmission; thereby ensuring that the cycle performance and safety of the lithium ion battery are improved without reducing the energy density of the lithium ion battery as much as possible; The negative electrode empty foil area can be an area reserved when the active material layer 11 is intermittently coated on the current collector 1, or it can be an area on the current collector 1 where part of the active material layer 11 is exposed after being washed; the formation method of the negative electrode empty foil area does not limit the setting of the etching groove 121; specifically, for the negative electrode empty foil area exposed by washing part of the active material layer 11 on the current collector 1, a negative electrode empty foil area and an etching area can be formed on the negative electrode sheet 4 by staged laser processing.

[0077] In another embodiment of the present invention, a method for preparing a lithium ion battery is provided, comprising the following operations: Obtaining a positive electrode sheet precursor and the negative electrode sheet 4 without the etching area 12; The positive electrode sheet precursor comprises the corresponding current collector 1, the positive electrode ear 31 integrally connected to the current collector 1, and the active material layer 11 coated on the current collector 1; a plurality of etching grooves 121 are formed by etching the active material layer 11 of the positive electrode sheet precursor; and the positive electrode sheet 3 is obtained; or, The positive electrode sheet precursor comprises the corresponding current collector 1, the active material layer 11 coated on the current collector 1, and the current collector 1 is provided with a positive electrode empty foil area without the active material layer 11; a plurality of etching grooves 121 are formed by etching the active material layer 11 of the positive electrode sheet precursor; the positive electrode ear 31 is welded on the positive electrode empty foil area; and the positive electrode sheet 3 is obtained; or, The positive electrode sheet precursor comprises the corresponding current collector 1, and the active material layer 11 coated on the entire surface of the current collector 1; cleaning a part of the active material layer 11 of the positive electrode sheet precursor to expose the positive electrode hollow foil area; etching a plurality of etching grooves 121 on the active material layer 11 of the positive electrode sheet precursor; welding the positive electrode ear 31 on the positive electrode hollow foil area; obtaining the positive electrode sheet 3; obtaining the diaphragm; The positive electrode sheet 3 , the negative electrode sheet 4 , and the separator are stacked or wound to form the electrode core.

[0078] Specifically, a plurality of etching grooves 121 are formed by etching the active material layer 11 of the positive electrode sheet precursor. These etching grooves 121 can reduce the release of lithium ions from the positive electrode sheet adjacent to the negative electrode ear area, avoid the accumulation of lithium ions near the negative electrode ear 41, and help reduce the risk of lithium ion precipitation near the negative electrode ear; whether the positive electrode sheet 3 with the positive electrode ear 31 integrally connected to the current collector 1, specifically, the positive electrode ear 31 is directly reserved on the current collector 1 through a die-cutting process, or the positive electrode empty foil area is reserved on the current collector 1, and then the positive electrode ear 31 is welded on the positive electrode empty foil area, the etching area 12 with the etching grooves 121 can be provided, and the setting position of the etching area 12 is not based on the position of the positive electrode ear 31, but based on the position of the negative electrode ear 41, so as to ensure that the cycle performance and safety of the lithium ion battery are improved without reducing the energy density of the lithium ion battery as much as possible; The positive electrode empty foil area can be an area reserved when the active material layer 11 is intermittently coated on the current collector 1, or it can be an area on the current collector 1 where part of the active material layer 11 is exposed after cleaning; the formation method of the positive electrode empty foil area does not limit the setting of the etching groove 121; specifically, for the scheme of exposing the positive electrode empty foil area by cleaning part of the active material layer 11 on the current collector 1, a positive electrode empty foil area and an etching area can be formed on the positive electrode sheet 4 through staged laser processing.

[0079] In some embodiments, the etching method is laser etching.

[0080] The present invention is further described below by way of examples.

[0081] Example 1 This embodiment is used to illustrate a lithium ion battery and a preparation method thereof disclosed in the present invention, comprising the following steps: Preparation of negative electrode sheet: The negative electrode sheet precursor comprises a corresponding current collector 1, an active material layer 11 coated on the current collector 1, and a negative electrode empty foil area without the active material layer 11 is provided on the current collector 1; a plurality of etching grooves 121 are etched on the active material layer of the negative electrode sheet precursor near the negative electrode empty foil area to form an etching area, the etching area length L=120mm, the etching groove width W1=100μm, the etching gap G=1mm, the etching groove depth H=40μm, the etching area width W, and the maximum width of the etching area is 85mm (in the direction away from the middle of the negative electrode ear connection part, the width of the etching area 12 gradually decreases, that is, the farther away from the middle of the negative electrode ear connection part, the smaller the etching area width, and it decreases proportionally from 85mm to 0mm); the negative electrode ear 41 is welded in the negative electrode empty foil area to obtain a negative electrode sheet; Preparation of positive electrode: The positive electrode sheet precursor comprises a corresponding current collector 1, an active material layer 11 coated on the current collector 1, and a positive electrode empty foil area without the active material layer 11 is provided on the current collector 1; a plurality of etching grooves 121 are formed by etching the active material layer 11 of the positive electrode sheet precursor; a positive electrode ear 31 is welded on the positive electrode empty foil area; and a positive electrode sheet 3 is obtained; Preparation of lithium-ion batteries: The positive electrode sheet, negative electrode sheet and separator are stacked or wound to form a pole core, the pole core is dried in a packaging bag, and the electrolyte is injected. After vacuum packaging, standing, formation, shaping and other processes, the preparation of the lithium-ion battery is completed.

[0082] Example 2 This example is used to illustrate a lithium ion battery and a preparation method thereof disclosed in the present invention, and includes most of the operations in Example 1, except that: On the negative electrode sheet: no etching groove 121 is made; The steps of preparing the positive electrode sheet also include: A plurality of etching grooves 121 are etched on the active material layer 11 of the positive electrode precursor to form an etching zone, wherein the etching zone length L=120 mm, the etching groove width W1=100 μm, the etching gap G=1 mm, the etching groove depth H=28 μm, and the maximum width of the etching zone is 25 mm (in the direction away from the middle of the negative electrode ear connection part, the width of the etching zone 12 gradually decreases, decreasing proportionally from 25 mm to 0).

[0083] Example 3 This example is used to illustrate a lithium ion battery and a preparation method thereof disclosed in the present invention, and includes most of the operations in Example 1, except that: The width of the etching area on the negative electrode sheet is W = 85 mm; On the negative electrode sheet: the maximum depth of the etching groove is 60μm, (along the direction away from the middle of the negative electrode ear connection part, the depth of the multiple etching grooves 121 of the etching area 12 in the thickness direction of the electrode sheet gradually decreases, that is, the farther away from the middle of the negative electrode ear connection part, the smaller the depth of the etching groove, and decreases proportionally from 60μm to 10μm).

[0084] Example 4 This example is used to illustrate a lithium ion battery and a preparation method thereof disclosed in the present invention, and includes most of the operations in Example 2, except that: On the positive electrode sheet: etching zone width W = 83mm; etching zone length L = 120mm, etching groove width W1 = 100μm, etching gap G = 1mm, etching groove maximum depth 51μm (along the direction away from the middle of the negative electrode ear connection, the depth of the multiple etching grooves 121 of the etching zone 12 in the thickness direction of the electrode sheet gradually decreases, that is, the farther away from the middle of the negative electrode ear connection, the smaller the etching depth, and it decreases proportionally from 51μm to 8μm).

[0085] Example 5 This example is used to illustrate a lithium ion battery and a preparation method thereof disclosed in the present invention, and includes most of the operations in Example 2, except that: On the positive electrode sheet: etching zone width W = 83mm; etching zone length L = 120mm, etching groove width W1 = 100μm, etching gap G = 1mm, etching groove maximum depth 42μm (along the direction away from the middle of the negative electrode ear connection part, the depth of the multiple etching grooves 121 of the etching zone 12 in the thickness direction of the electrode sheet gradually decreases, that is, the farther away from the middle of the negative electrode ear connection part, the smaller the etching depth, and it decreases proportionally from 42μm to 8μm).

[0086] Example 6 This example is used to illustrate a lithium ion battery and a preparation method thereof disclosed in the present invention, and includes most of the operations in Example 1, except that: On the negative electrode sheet: the etching area width W = 85mm; the maximum width of the etching groove is 200μm (along the direction away from the middle of the negative electrode ear connection part, the width of the multiple etching grooves 121 of the etching area 12 in the extension direction of the electrode length gradually decreases, that is, the farther away from the middle of the negative electrode ear connection part, the smaller the etching groove width is, and it decreases proportionally from 200μm to 50μm).

[0087] Example 7 This example is used to illustrate a lithium ion battery and a preparation method thereof disclosed in the present invention, and includes most of the operations in Example 1, except that: On the negative electrode sheet: the etching area length L = 50mm.

[0088] Example 8 This example is used to illustrate a lithium ion battery and a preparation method thereof disclosed in the present invention, and includes most of the operations in Example 1, except that: On the negative electrode sheet: the etching area length L = 300mm.

[0089] Comparative Example 1 This comparative example is used to compare and illustrate a lithium ion battery and a preparation method thereof disclosed in the present invention, and includes most of the operations in Example 1, except that: When preparing the negative electrode sheet, no etching area is provided on the negative electrode sheet, and the negative electrode ear is located between the two ends of the current collector; When preparing the positive electrode sheet, no etching area is set on the positive electrode sheet, and the positive electrode ear is located between the two ends of the current collector.

[0090] Comparative Example 2 This comparative example is used to compare and illustrate a lithium ion battery and a preparation method thereof disclosed in the present invention, and includes most of the operations in Example 1, except that: When preparing the negative electrode sheet, no etching area is provided on the negative electrode sheet, and the negative electrode ear is located at the end of the current collector; When preparing the positive electrode sheet, no etching area is set on the positive electrode sheet, and the positive electrode ear is located at the end of the current collector.

[0091] Performance Testing The following performance tests were performed on Examples 1 to 6 and Comparative Examples 1 to 2 prepared as above: Battery cycle performance test: Test method: Charge the battery at 3C constant current and constant voltage to 4.5V, cut off at 0.05C, discharge at 0.5C, cycle 800 times, disassemble the battery, and confirm the degree of lithium deposition in the battery cell (no lithium deposition / slight lithium deposition / severe lithium deposition).

[0092] The above test results are filled in Table 1.

[0093] Table 1 From the test results in Table 1, it can be seen that Examples 1 to 8 do not precipitate lithium, which is better than Comparative Examples 1 to 2, indicating that setting an etching area on the positive electrode sheet 3 or the negative electrode sheet 4 can reduce the risk of lithium precipitation and improve the cycle performance and safety of the lithium-ion battery; The energy density of Example 1, Example 3 and Example 6 is better than that of Comparative Example 1 and Comparative Example 2, indicating that whether the scheme of Example 1 "the width of the etched area 12 gradually decreases along the direction away from the middle of the negative electrode ear connection part", Example 3 "the depth of the multiple etched grooves in the etched area 12 in the thickness direction of the pole piece gradually decreases along the direction away from the middle of the negative electrode ear connection part", or Example 6 "the width of the multiple etched grooves in the etched area 12 in the extension direction of the pole piece length gradually decreases along the direction away from the middle of the negative electrode ear connection part" is adopted, it is possible to improve the lithium precipitation problem while ensuring the energy density, which is beneficial to improving the cycle performance and safety of lithium-ion batteries; The test results of Example 2 show that a reasonable design of the maximum width of the etching area 12 can minimize the reduction in energy density while solving the lithium deposition problem; The test results of Examples 4 and 5 show that a reasonable design of the depths of the multiple etching grooves of the etching area 12 in the thickness direction of the electrode can minimize the reduction in energy density while solving the lithium deposition problem.

[0094] The test results of Examples 7 and 8 show that when the etching zone length L is reasonably designed, the energy density does not differ much and the cycle performance can meet the requirements. When the etching length is small, the etching process is simpler and the cost is reduced, but its cycle performance deteriorates. When the etching length is too large, its cycle performance is improved, but the etching time increases and the cost increases.

[0095] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A lithium ion battery, characterized in that: It comprises a positive electrode sheet (3), a negative electrode sheet (4), and a separator arranged between the positive electrode sheet (3) and the negative electrode sheet (4), wherein the positive electrode sheet (3), the negative electrode sheet (4) and the separator are stacked or wound to form a pole core; The positive electrode sheet (3) and the negative electrode sheet (4) both comprise a current collector (1) and an active material layer disposed on the surface of the current collector (1); The positive electrode sheet (3) further comprises a positive electrode ear (31) connected to its current collector (1), and the negative electrode sheet (4) further comprises a negative electrode ear (41) connected to its current collector (1); The portion of the negative electrode sheet (4) where the negative electrode ear (41) is provided is a negative electrode ear connecting portion; An etching area (12) is formed on the active material layer (11) adjacent to the negative electrode tab connection portion on the negative electrode sheet (4), or on the active material layer opposite to the negative electrode tab connection portion on the positive electrode sheet (3); and a plurality of etching grooves (121) are provided on the active material layer (11) of the etching area (12).

2. A lithium ion battery according to claim 1, characterized in that: The etched region (12) comprises a first negative electrode etched region (42) formed on the negative electrode sheet (4), the first negative electrode etched region (42) and the negative electrode tab (41) are located on the same side of the negative electrode sheet (4), and the first negative electrode etched region (42) is located in a region of the active material layer (11) adjacent to the negative electrode tab connection portion; or, The etching region (12) comprises a second negative electrode etching region (43) formed on the negative electrode sheet (4), the second negative electrode etching region (43) and the negative electrode ear (41) are respectively located on two sides of the negative electrode sheet (4), and the second negative electrode etching region (43) is located in a region of the active material layer (11) adjacent to the negative electrode ear connection portion.

3. A lithium ion battery according to claim 2, characterized in that: The first negative electrode etching region (42) comprises a plurality of etching grooves (121) distributed in a direction gradually away from the middle of the negative electrode ear connecting portion; and / or, The second negative electrode etching region (43) comprises a plurality of etching grooves (121) distributed in a direction gradually moving away from the middle of the negative electrode ear connecting portion.

4. A lithium ion battery according to claim 1, characterized in that: The etching region (12) comprises a first positive electrode etching region (32) formed on the positive electrode sheet (3); the first positive electrode etching region (32) faces a side of the negative electrode sheet (4) on which the negative electrode ear (41) is provided; and / or the etching region (12) comprises a second positive electrode etching region (33) formed on the positive electrode sheet (3); the second positive electrode etching region (33) faces a side of the negative electrode sheet (4) away from the negative electrode ear (41).

5. A lithium ion battery according to claim 4, characterized in that: The portion of the positive electrode sheet (3) opposite to the negative electrode ear connection portion is the negative electrode ear alignment portion; The first positive electrode etching region (32) comprises a plurality of etching grooves (121) distributed in a direction gradually away from the middle of the negative electrode ear alignment portion; and / or, The second positive electrode etching area (33) comprises a plurality of etching grooves (121) distributed in a direction gradually moving away from the middle of the negative electrode ear alignment portion.

6. A lithium ion battery according to claim 5, characterized in that: The first positive electrode etching region (32) and / or the second positive electrode etching region (33) further comprises a plurality of etching grooves (121) arranged on the active material layer (11) at the negative electrode ear-aligned portion.

7. A lithium ion battery according to claim 1, characterized in that: A pole piece adhesive tape (2) is provided on the side of the positive pole sheet (3) facing the negative pole ear (41), and / or on the side of the positive pole sheet (3) facing the negative pole sheet (4) away from the negative pole ear (41); the pole piece adhesive tape (2) is directly opposite to the negative pole ear (41).

8. A lithium ion battery according to claim 1, characterized in that: A plurality of etching grooves (121) are arranged in parallel and at intervals on the active material layer (11) of the corresponding etching area (12).

9. A lithium ion battery according to claim 1, characterized in that: The extension direction of the plurality of etching grooves (121) is parallel to or coincides with the extension direction of the negative electrode tab (41).

10. A lithium ion battery according to any one of claims 1 to 9, characterized in that: The length direction of the etched area (12) is consistent with the width direction of the negative electrode ear (41), and the width direction of the etched area (12) is consistent with the length direction of the negative electrode ear (41); The etching groove (121) penetrates one side or both sides of the active material layer (11) along the extension direction of the negative electrode ear (41).

11. A lithium ion battery according to claim 10, characterized in that: On the negative electrode sheet (4) or on the positive electrode sheet (3): the length of the etching area (12) is 50 mm to 300 mm, and the width of the etching area (12) is 20 mm to 150 mm.

12. A lithium ion battery according to claim 10, characterized in that: Along a direction away from the middle of the negative electrode ear connecting portion, the width of at least one of the etched areas (12) gradually decreases.

13. A lithium ion battery according to claim 11, characterized in that: The maximum width of the etching area (12) is 25 mm to 85 mm.

14. A lithium ion battery according to claim 10, characterized in that: Along the direction away from the middle of the negative electrode ear connection portion, the width of the plurality of etching grooves (121) of at least one of the etching regions (12) in the direction of extension of the length of the electrode piece gradually decreases.

15. A lithium ion battery according to claim 14, characterized in that: The width of the etching groove (121) is 50 μm to 200 μm.

16. A lithium ion battery according to claim 1, characterized in that: Along a direction away from the middle of the negative electrode tab connection portion, the depth of the plurality of etching grooves (121) of at least one of the etching regions (12) in the thickness direction of the electrode sheet gradually decreases.

17. A lithium ion battery according to claim 16, characterized in that: The depth of the etched groove (121) is 8 μm to 60 μm.

18. A lithium ion battery according to claim 1, characterized in that: The negative electrode tab (41) is located at an end of the current collector (1), or the negative electrode tab (41) is located between two ends of the current collector (1).

19. A method for preparing a lithium ion battery according to any one of claims 1 to 9, characterized in that: The following operations are included: Obtaining a negative electrode sheet precursor and the positive electrode sheet (3) without the etching area (12); or obtaining a positive electrode sheet precursor and the negative electrode sheet (4) without the etching area (12); The negative electrode sheet precursor comprises the corresponding current collector (1), the negative electrode ear (41) integrally connected to the current collector (1), and the active material layer (11) coated on the current collector (1); a plurality of etching grooves (121) are formed by etching the active material layer (11) of the negative electrode sheet precursor; and the negative electrode sheet (4) is obtained; or, The negative electrode sheet precursor comprises the corresponding current collector (1), the active material layer (11) coated on the current collector (1), and a negative electrode hollow foil area without the active material layer (11) is provided on the current collector (1); a plurality of etching grooves (121) are formed by etching the active material layer (11) of the negative electrode sheet precursor; the negative electrode ear (41) is welded on the negative electrode hollow foil area; and the negative electrode sheet (4) is obtained; or, The negative electrode sheet precursor comprises the corresponding current collector (1) and the active material layer (11) coated on the entire surface of the current collector (1); cleaning a portion of the active material layer (11) of the negative electrode sheet precursor to expose a negative electrode hollow foil area; etching the active material layer (11) of the negative electrode sheet precursor to form a plurality of etching grooves (121); welding the negative electrode ear (41) to the negative electrode hollow foil area; and obtaining the negative electrode sheet (4); The positive electrode sheet precursor comprises the corresponding current collector (1), the positive electrode ear (31) integrally connected to the current collector (1), and the active material layer (11) coated on the current collector (1); a plurality of etching grooves (121) are formed by etching the active material layer (11) of the positive electrode sheet precursor; and the positive electrode sheet (3) is obtained; or, The positive electrode sheet precursor comprises the corresponding current collector (1), the active material layer (11) coated on the current collector (1), and a positive electrode hollow foil area without the active material layer (11) is provided on the current collector (1); a plurality of etching grooves (121) are formed by etching the active material layer (11) of the positive electrode sheet precursor; the positive electrode ear (31) is welded on the positive electrode hollow foil area; and the positive electrode sheet (3) is obtained; or, The positive electrode sheet precursor comprises the corresponding current collector (1) and the active material layer (11) coated on the entire surface of the current collector (1); cleaning a portion of the active material layer (11) of the positive electrode sheet precursor to expose a positive electrode hollow foil area; etching the active material layer (11) of the positive electrode sheet precursor to form a plurality of etching grooves (121); welding the positive electrode ear (31) to the positive electrode hollow foil area; and obtaining the positive electrode sheet (3); obtaining the diaphragm; The positive electrode sheet (3), the negative electrode sheet (4) and the separator are stacked or wound to form the electrode core.

20. The method for preparing a lithium ion battery according to claim 19, characterized in that: The etching method is laser etching.

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