Positive plate, battery cell thereof and lithium ion battery
By designing alternating convex and concave structures on the positive electrode, the problem of uneven stress at the corners of the wound battery cell is solved, the lithium plating phenomenon is improved, and the safety and applicability of the battery cell are enhanced.
Patent Information
- Application Number
- CN202422946411.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-11-29
- Publication Date
- 2025-12-19
- Estimated Expiration
- 2034-11-29
AI Technical Summary
Uneven stress at the corners of wound battery cells can lead to the shedding of active material from the electrode, brittle fracture, and lithium plating, affecting battery reliability and lifespan.
An undercoating layer is applied to the positive electrode. The undercoating layer has alternating convex and concave portions along the length of the electrode. The thickness and areal density of the active material layer on the surface of the convex portion are smaller than those of the concave portion. The design is an alternating structure of straight and corner regions. The N/P ratio is adjusted appropriately to ensure sufficient margin for the negative electrode.
It improves the lithium plating problem at the cell corners, enhances the safety and versatility of the cell structure, and is suitable for wound cells with different electrode sizes and structures.
Smart Images
Figure CN223693136U_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The utility model relates to secondary battery technical field, concretely relates to a positive plate and its electric core and lithium ion battery. BACKGROUND
[0002] The battery usually includes a shell and a roll core located in the shell. When manufacturing some roll cores, the long strip-shaped roll material is usually formed by winding. In some preparation processes, the roll core after winding can also be treated by cold pressing or hot pressing. The curvature of the roll core formed by winding is large at the corner. In the long cycle process, the negative corner will preferentially precipitate lithium compared to the plane, there is a large stress, which causes the pole piece at the corner to easily have active material falling off, brittle fracture cracking and other adverse conditions, and even lithium precipitation, which is not conducive to ensuring the reliability and service life of the battery.
[0003] Therefore, it is necessary to provide a technical solution to solve the above problems. UTILITY MODEL CONTENT
[0004] One of the purposes of the utility model is: in view of the shortage of prior art, a positive plate is provided to improve the problem of uneven corner stress of the winding type electric core and lithium precipitation.
[0005] In order to achieve the above purpose, the utility model adopts the following technical scheme:
[0006] A positive plate comprises:
[0007] A positive current collector;
[0008] A bottom coating layer arranged on at least one surface of the positive current collector; and
[0009] A positive active material layer arranged on the surface of the bottom coating layer;
[0010] The bottom coating layer has a plurality of convex parts and concave parts alternately distributed along the length direction of the pole piece.
[0011] When the positive plate is in a winding state, the positive plate has a flat area and a corner area alternately arranged along the winding direction of the positive plate, the concave part is located in the flat area, and the convex part is located in the corner area. Preferably, the thickness of the positive active material layer on the surface of the convex part is less than the thickness of the positive active material layer on the surface of the concave part.
[0012] Preferably, the surface density of the positive active material layer on the surface of the convex part is less than the surface density of the positive active material layer on the surface of the concave part.
[0013] Preferably, the shape of the convex part is circular arc or trapezoidal, and the length of the convex part is less than the length of the concave part.
[0014] The utility model discloses a second purpose is to provide a kind of electric core, including the positive sheet of any one described above, diaphragm and negative sheet are sequentially laminated and rolled into flat roll core, the convex part of the positive sheet is located the corner area of the roll core.
[0015] Preferably, the N / P value of the corner area of the roll core is 1.03-1.05.
[0016] Preferably, the gram capacity of negative electrode active material in the negative sheet is Ca, the weight percentage of negative electrode active material is Wa, and the coating surface density of negative electrode current collector is ρa.
[0017] The gram capacity of positive electrode active material in the positive sheet is Cc, the weight percentage of positive electrode active material is Wc, and the coating surface density of positive electrode current collector is ρc.
[0018] The capacity margin (N / P) 0 of the negative sheet relative to the concave part of the positive sheet satisfies the relationship:
[0019] (N / P) 0=(Ca*Wa*ρa) / (Cc*Wc*ρc).
[0020] Preferably, the number of winding turns of the roll core is i; the circular arc radius of the i th negative sheet is Ra, and the circular arc radius of the i th positive sheet is Rc.
[0021] The capacity margin (N / P) i of the negative sheet of the corner area relative to the concave part of the positive sheet satisfies the relationship:
[0022] (N / P) i=(Ca*Wa*ρa*π*Ra) / (Cc*Wc*ρc*π*Rc).
[0023] Preferably, when (N / P) 0=(N / P) i, the thickness of the positive electrode current collector is H0, the thickness of the primer layer is H1, and the height of the convex part is H, which satisfies the relationship:
[0024] H=(Ca*Wa*ρa*π*Ra*2 / Cc*ρc*(N / P) i+H0+H1)-(Ca*Wa*ρa*2 / Cc*ρc*(N / P) 0+H0+H1).
[0025] The utility model discloses a third purpose is to provide a kind of lithium ion battery, including the electric core described above.
[0026] Compared with the prior art, the positive plate provided by the utility model has the advantages that the positive plate is provided with at least one surface bottom coating layer on the current collector, the bottom coating layer comprises a plurality of convex parts distributed along the length direction of the positive plate and concave parts between adjacent convex parts, the convex part surface density of the positive plate is less than that of the concave part, the positive lithium ion can be normally inserted into the negative electrode, the anode corner lithium precipitation problem is effectively improved, the N / P ratio of the corner position is increased, the safety of the battery cell structure is improved, and the design of the positive plate is suitable for different sizes and structures of the wound type battery cell, and has strong universality and flexibility. BRIEF DESCRIPTION OF DRAWINGS
[0027] Figure 1 It is a structure schematic view of the positive plate of an embodiment of the utility model;
[0028] Figure 2 It is a structure schematic view of the positive plate of another embodiment of the utility model.
[0029] Among them, 1-positive current collector; 2-bottom coating layer; 21-convex part; 22, concave part; 3-positive active material layer. DETAILED DESCRIPTION
[0030] In order to make the technical scheme and advantages of the utility model more clear, the following will be combined with specific implementation manner, and the utility model and its beneficial effects are further described in detail, but the implementation manner of the utility model is not limited to this.
[0031] The terms "first", "second" are only for the purpose of description, and can not be understood as indicating or implying relative importance or implicitly indicating the number of indicated technical features. Therefore, the features defined as "first", "second" can explicitly or implicitly include one or more features. In the description of the utility model, the meaning of "a plurality of" is two or more, unless otherwise specifically limited.
[0032] The utility model first aspect aims at providing a kind of positive plate, comprising: current collector 1;Bottom coating layer 2 being set to at least one surface of current collector;And positive active material layer 3 being set to the surface of bottom coating layer;Wherein, bottom coating layer includes a plurality of convex parts 21 and the concave part 22 between adjacent convex parts distributed along the length direction of the positive plate.
[0033] When the positive plate is in the state of winding, the positive plate has flat area and corner area alternately arranged along its winding direction, the concave part 22 is located in the flat area, and the convex part 21 is located in the corner area. Wherein, the thickness of positive active material layer on the surface of the convex part 21 is less than the thickness of positive active material layer on the surface of the concave part 22.
[0034] The active substance in the bottom coating layer 2 is lithium iron phosphate material or ceramic material, and the ceramic material is selected from one of aluminum oxide, zirconium oxide, boehmite, magnesium oxide, silicon oxide and calcium oxide.
[0035] The active substance in the positive electrode active material layer 3 is one of lithium cobaltate, ternary material, lithium iron phosphate, lithium manganate and lithium-rich manganese.
[0036] In the utility model, the thickness of the positive electrode active material layer 3 on the surface of the convex part 21 is less than the thickness of the positive electrode active material layer 3 on the surface of the concave part 22, and the surface density of the positive electrode active material layer 3 on the surface of the convex part 21 is less than the surface density of the positive electrode active material layer 3 on the surface of the concave part 22. In the positive and negative electrode sheet coating process, due to the thick edge effect, the edge surface density may not match, for example, the positive electrode edge surface density is too large or the negative electrode edge surface density is too small, which will cause lithium precipitation; in the utility model, the less surface density of the convex part 21 of the positive electrode compared with the concave part 22 makes the matching negative electrode sufficient, and the lithium ion in the positive electrode can normally insert into the matching negative electrode, thereby effectively improving the anode corner lithium precipitation problem.
[0037] In the utility model, the shape of the convex part 21 is circular arc or trapezoidal, and the length of the convex part 21 is less than the length of the concave part 22.
[0038] The second purpose of the utility model is to provide an electric core, which comprises the flat core formed by stacking and winding the positive electrode sheet, the diaphragm and the negative electrode sheet in any one of the above.
[0039] In some embodiments, the N / P value of the corner area of the core is 1.03-1.05. When the N / P ratio is too large, it means that the negative electrode is excessively large, which leads to shallow charging and discharging of the negative electrode and deep charging and discharging of the positive electrode, and the negative electrode is not easy to precipitate lithium in the full state, which is relatively safer, but the increase of the oxidation state of the positive electrode increases the safety hazard, and may also lead to the separation of the positive electrode powder and the foil, the yellowing of the diaphragm, and the influence on the performance of the battery. The lower N / P ratio is easy to cause the lithium precipitation of the negative electrode sheet of the battery in the cycle process, and the deposition of lithium metal is easy to form lithium dendrites, which pierces the diaphragm and affects the safety of the lithium battery.
[0040] Wherein, the negative electrode active material gram capacity in the negative electrode sheet is Ca, the weight percentage of the negative electrode active material is Wa, and the coating surface density of the negative electrode current collector is ρa.
[0041] The positive electrode active material gram capacity in the positive electrode sheet is Cc, the weight percentage of the positive electrode active material is Wc, and the coating surface density of the positive electrode current collector is ρc.
[0042] The capacity margin (N / P) 0 of the negative electrode sheet relative to the concave part of the positive electrode sheet satisfies the relationship:
[0043] (N / P)0=(Ca*Wa*ρa) / (Cc*Wc*ρc).
[0044] wherein the winding number of the roll core is i; the circular arc radius of the negative plate of the i th winding is Ra, and the circular arc radius of the positive plate of the i th winding is Rc;
[0045] The capacity margin (N / P)i of the negative plate of the corner region relative to the concave part of the positive plate satisfies the relationship:
[0046] (N / P)i=(Ca*Wa*ρa*π*Ra) / (Cc*Wc*ρc*π*Rc).
[0047] When (N / P)0=(N / P)i, the thickness of the positive current collector is H0, the thickness of the primer layer is H1, and the height of the convex part is H, which satisfy the relationship:
[0048] H=(Ca*Wa*ρa*π*Ra*2 / Cc*ρc*(N / P)i+H0+H1)-(Ca*Wa*ρa*2 / Cc*ρc*(N / P)0+H0+H1).
[0049] Through the above calculation formula, the height of the positive convex part can be calculated according to the actual production needs, so that the N / P value of the corner region reaches the N / P value of the concave region, and the mass production is high in manufacturing degree; in addition, the positive plate convex part of the utility model can be designed as single-sided or double-sided according to the corner of the roll core, and can be flexibly adjusted according to the length of the plate.
[0050] The plate design of the utility model can be applied to different plate lengths and widths, and different structure of the winding type core, such as M6S, MTS, MTT, TTC, ZZS and the like, and has strong versatility and flexibility.
[0051] In the third aspect according to the utility model, the utility model further provides a lithium ion battery, which comprises the above-mentioned core, electrolyte and shell.
[0052] The preparation method of the lithium ion battery of the utility model is known to those skilled in the art, and generally, the preparation method of the battery comprises placing the core into the battery shell, adding electrolyte, and then sealing to obtain the battery.
[0053] Table 1 is the lithium extraction test result when the N / P ratio of the corner region of the roll core is different.
[0054] Table 1
[0055]
[0056]
[0057] In conclusion, the utility model discloses a convex part on the positive plate is designed, and the surface density of the convex part is less than the concave part, so that the excess of the negative pole is sufficient, the positive lithium ion can be normally embedded into the negative pole, thereby effectively improving the lithium precipitation problem of the anode corner, increasing the N / P ratio of the corner position, and the positive plate in the range of the utility model does not precipitate lithium, and the safety of the battery structure is effectively improved.
[0058] Based on the disclosure and teaching of the above description, the person skilled in the art of the utility model can also change and modify the above embodiments. Therefore, the utility model is not limited to the above specific embodiments, and any obvious improvement, replacement or modification made by the person skilled in the art on the basis of the utility model belongs to the protection scope of the utility model. In addition, although some specific terms are used in the specification, these terms are only for convenience of description and do not constitute any limitation on the utility model.
Claims
1. A positive electrode sheet characterized by comprising: The positive electrode current collector; The undercoat layer arranged on at least one surface of the positive electrode current collector; The positive electrode active material layer arranged on the surface of the undercoat layer; The undercoat layer has a plurality of convex portions and concave portions alternately distributed along the length direction of the electrode tab; When the positive electrode tab is in the wound state, the positive electrode tab has flat regions and corner regions alternately arranged along the winding direction of the positive electrode tab, the concave portions are located in the flat regions, and the convex portions are located in the corner regions. The thickness of the positive electrode active material layer on the surface of the convex portion is less than the thickness of the positive electrode active material layer on the surface of the concave portion. The surface density of the positive electrode active material layer on the surface of the convex portion is less than the surface density of the positive electrode active material layer on the surface of the concave portion.
2. The positive electrode sheet according to claim 1, characterized by: The convex portion has a circular arc shape or a trapezoidal shape, and the length of the convex portion is less than the length of the concave portion.
3. The positive electrode sheet according to claim 1, characterized by: The flat battery core is formed by sequentially stacking the positive electrode tab, the separator, and the negative electrode tab according to any one of claims 1-4.
4. The positive electrode sheet according to claim 1, characterized by: The N / P value of the corner region of the battery core is 1.03-1.
05.
5. An electric cell characterized by 7. The battery core according to claim 5, wherein:
6. The electric cell of claim 5, wherein: The gram capacity of the negative electrode active material in the negative electrode tab is Ca, the weight percentage of the negative electrode active material is Wa, and the coating surface density of the negative electrode current collector is pa; The gram capacity of the positive electrode active material in the positive electrode tab is Cc, the weight percentage of the positive electrode active material is Wc, and the coating surface density of the positive electrode current collector is pc; The capacity margin (N / P)0 of the negative electrode tab relative to the concave portion of the positive electrode tab satisfies the relationship: (N / P)0=(Ca*Wa*pa) / (Cc*Wc*pc). The number of winding turns of the battery core is i, the circular arc radius of the negative electrode tab of the ith turn is Ra, and the circular arc radius of the positive electrode tab of the ith turn is Rc; The capacity margin (N / P)i of the negative electrode tab relative to the concave portion of the positive electrode tab in the corner region satisfies the relationship:
8. The electric cell of claim 7, wherein: (N / P)i=(Ca*Wa*pa*π*Ra) / (Cc*Wc*pc*π*Rc). When (N / P)0=(N / P)i, The thickness of the positive electrode current collector is H0, the thickness of the undercoat layer is H1, and the height of the convex portion is H, which satisfy the relationship:
9. The electric cell of claim 8, wherein: H=(Ca*Wa*pa*π*Ra*2 / Cc*pc*(N / P)i+H0+H1)-(Ca*Wa*pa*2 / Cc*pc*(N / P)0+H0+H1). The battery core according to any one of claims 5-9. 10. A lithium-ion battery, characterized by,