A diaphragm bag and a battery

Abstract

The utility model provides a kind of diaphragm bag and battery, comprising: diaphragm, diaphragm has N, first diaphragm to N diaphragm is sequentially stacked along first direction;Diaphragm has N first side and N second side in the two sides of second direction respectively, N first side and N second side are welded in first direction respectively, form N-1 cavity;Diaphragm has height H in third direction;When N is odd, along first diaphragm to N / 2+1 diaphragm, height H increases sequentially;Along N / 2+1 diaphragm to N diaphragm, height H sequentially decreases;When N is even, along first diaphragm to N / 2 diaphragm, height H increases sequentially;Along N / 2+1 diaphragm to N diaphragm, height H sequentially decreases, and the height H of N / 2 diaphragm is equal to the height of N / 2+1 diaphragm;First direction is the direction parallel to diaphragm bag thickness, second direction is the direction parallel to diaphragm bag width, and third direction is the direction parallel to diaphragm bag height.

Description

Technical Field

[0001] This utility model relates to the field of sodium-ion battery production technology, and in particular to a separator bag and a battery. Background Technology

[0002] With the rapid development of large-scale energy storage and smart grids, the performance requirements for energy storage batteries, including energy efficiency and safety, are becoming increasingly stringent. Sodium and lithium share similar chemical properties, and sodium batteries offer significantly lower costs compared to lithium batteries, making them a potential future alternative to lithium-ion batteries. However, sodium-ion batteries are susceptible to failure during manufacturing and use. Therefore, conducting failure analysis on sodium-ion batteries is essential to avoid performance degradation and safety issues.

[0003] Currently, failure analysis methods for sodium-ion batteries are primarily derived from those for lithium-ion batteries. When investigating the failure mechanisms of failed cells at the cell-electrode-material level, it is inevitable to manufacture single-cell half-cells and single-cell three-electrode batteries. Single-cell half-cells are mainly used to analyze capacity loss at the electrode level, while single-cell three-electrode batteries are mainly used to analyze internal resistance changes at the electrode level. Traditional single-cell batteries consist of a positive electrode, a negative electrode, a separator, tabs, and an aluminum-plastic film casing. These batteries are generally manufactured using the following process: the positive electrode is placed inside the separator bag, the negative electrode is fixed to both sides of the positive electrode using adhesive, and then assembled and sealed. Single-cell three-electrode batteries, on the other hand, add a separator and use adhesive to fix a reference electrode between the positive and negative electrodes. The traditional manufacturing methods for single-cell and single-cell three-electrode batteries result in inaccurate positioning of the positive and negative electrodes, leading to significant relative positional deviations and low battery yield. Utility Model Content

[0004] To address the aforementioned issues, this invention aims to propose a separator bag and battery. Through a stepped height-distributed N-layer separator structure design, a symmetrical stepped cavity structure is formed, thereby improving battery yield.

[0005] To achieve the above objectives, the technical solution of this utility model is implemented as follows:

[0006] A diaphragm bag, comprising:

[0007] A diaphragm, wherein there are N diaphragms, and the first diaphragm to the Nth diaphragm are stacked sequentially along a first direction;

[0008] The diaphragm has N first side edges and N second side edges on both sides in the second direction, and the N first side edges and N second side edges are welded in the first direction to form N-1 cavities;

[0009] The diaphragm has a height H in the third direction;

[0010] When N is an odd number, the height H increases sequentially from the first diaphragm to the (N / 2+1)th diaphragm; and decreases sequentially from the (N / 2+1)th diaphragm to the Nth diaphragm.

[0011] When N is even, the height H increases sequentially from the first diaphragm to the N / 2th diaphragm; the height H decreases sequentially from the N / 2+1th diaphragm to the Nth diaphragm, and the height H of the N / 2th diaphragm is equal to the height of the N / 2+1th diaphragm.

[0012] The first direction is parallel to the thickness of the diaphragm bag, the second direction is parallel to the width of the diaphragm bag, and the third direction is parallel to the height of the diaphragm bag.

[0013] Furthermore, the diaphragm bag includes five diaphragms, with the first to fifth diaphragms stacked sequentially along the first direction to form four cavities;

[0014] The four cavities include:

[0015] The first cavity is used to house the first negative electrode;

[0016] The second cavity is used to house the reference electrode;

[0017] The third cavity is used to house the positive electrode;

[0018] The fourth cavity is used to house the second negative electrode.

[0019] Furthermore, the heights of the first to fifth diaphragms in the third direction are H1, H2, H3, H4, and H5, respectively; and satisfy: H1 = H5, H2 = H4, H1 = H2 * 3 / 4; 2mm ≤ H3 - H2 ≤ 3mm.

[0020] Furthermore, the heights of the first negative electrode and the second negative electrode in the third direction are H, respectively. 1负 H 2负 The condition is satisfied that 1mm ≤ H2 - H 1负 ≤2mm, 1mm≤H4-H 2负 ≤2mm.

[0021] Furthermore, the first to fifth diaphragms have widths W1, W2, W3, W4, and W5 in the second direction; the first negative electrode and the second negative electrode have widths W in the second direction. 1负 W 2负 Satisfying W1=W2=W3=W4=W5, W 1负 =W 2负 And 1mm≤W1-W 2负 ≤2mm.

[0022] To achieve the above object, the present utility model also discloses a battery including the above diaphragm bag, further comprising a housing, and the diaphragm bag is disposed inside the housing;

[0023] The diaphragm bag includes four diaphragms. The first diaphragm to the fourth diaphragm are sequentially stacked along the first direction to form three cavities; the three cavities include: a first cavity, a second cavity, and a third cavity;

[0024] A first sodium sheet is disposed inside the first cavity;

[0025] A positive electrode sheet or a negative electrode sheet is disposed in the second cavity;

[0026] A second sodium sheet is disposed inside the third cavity;

[0027] The heights of the first diaphragm to the fourth diaphragm in the third direction are H1, H2, H3, and H4 respectively, where H1 = H4 < H2 = H3;

[0028] The heights of the first sodium sheet and the second sodium sheet in the third direction are H Na1 and H Na2 , where H Na1 < H2, H Na2 < H3;

[0029] The first diaphragm and the fourth diaphragm are polypropylene diaphragms, and the second diaphragm and the third diaphragm are glass fiber diaphragms.

[0030] Further, H1 = 3 / 4 * H2.

[0031] Further, the positive electrode sheet or the negative electrode sheet disposed inside the second cavity has a height H 极片 in the third direction, satisfying 1 mm ≤ H2 - H 极片 ≤ 2 mm.

[0032] Further, the second diaphragm and the third diaphragm

[0033] have widths W2 and W3 in the second direction, and W2 = W3,

[0034] The positive electrode sheet or the negative electrode sheet disposed inside the second cavity has a width W 极片 ,

[0035] satisfying 1 mm ≤ W2 - W 极片 ≤ 2 mm.

[0036] Further, H1, H4, W2, and W3 satisfy 4 ≤ H1 - W2 ≤ 5 mm.

[0037] Beneficial effects: This utility model improves battery yield by forming a symmetrical stepped cavity structure through the design of an N-layer separator structure with a stepped height distribution. Attached Figure Description

[0038] The accompanying drawings, which form part of this utility model, are used to provide a further understanding of the utility model. The illustrative embodiments of the utility model and their descriptions are used to explain the utility model and do not constitute an undue limitation of the utility model. In the drawings:

[0039] Figure 1 This is a schematic diagram of the structure of the separator described in Embodiment 1 of this utility model (when there are five separators, it can be used to make a single three-electrode battery);

[0040] Figure 2 This is a schematic diagram of the structure of the battery described in Embodiment 2 of this utility model (when there are four separators, it can be used to make a single half cell);

[0041] Figure 3 The charging curve of the negative electrode half-cell before cycling and before degradation, which is made using "stepped composite separator bag" and "polypropylene stepped multilayer separator bag" as described in the embodiments of the present invention.

[0042] Figure 4 The charging curve of the negative electrode half-cell with a high degree of deterioration after cycling, which is made using "stepped composite separator bag" and "polypropylene stepped multilayer separator bag" as described in the embodiments of the present invention.

[0043] In the figure, 1-first diaphragm, 2-second diaphragm, 3-third diaphragm, 4-fourth diaphragm, 5-fifth diaphragm, 6-first cavity, 7-second cavity, 8-third cavity, 9-fourth cavity, 10-first negative electrode, 11-reference electrode, 12-positive electrode, 13-second negative electrode, 14-first sodium plate, 15-positive or negative electrode plate, 16-second sodium plate, 100-shell. Detailed Implementation

[0044] It should be noted that, unless otherwise specified, the embodiments and features described in these embodiments can be combined with each other.

[0045] This solution proposes a diaphragm bag, comprising:

[0046] A diaphragm, comprising N diaphragms, wherein the first diaphragm to the Nth diaphragm are stacked sequentially along a first direction;

[0047] The diaphragm has N first side edges and N second side edges on both sides in the second direction. The N first side edges and N second side edges are welded in the first direction to form N-1 cavities.

[0048] The diaphragm has a height H in the third direction;

[0049] When N is an odd number, the height H increases sequentially from the first diaphragm to the (N / 2+1)th diaphragm; and decreases sequentially from the (N / 2+1)th diaphragm to the Nth diaphragm.

[0050] When N is even, the height H increases sequentially from the first diaphragm to the N / 2th diaphragm; the height H decreases sequentially from the N / 2+1th diaphragm to the Nth diaphragm, and the height H of the N / 2th diaphragm is equal to the height of the N / 2+1th diaphragm.

[0051] The first direction is parallel to the thickness of the diaphragm bag, the second direction is parallel to the width of the diaphragm bag, and the third direction is parallel to the height of the diaphragm bag.

[0052] By designing an N-layer separator structure with a stepped height distribution, a symmetrical stepped cavity structure is formed, which improves the battery yield.

[0053] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0054] Example 1

[0055] See Figure 1 In a specific example, the diaphragm bag includes five diaphragms, namely the first diaphragm 1, the second diaphragm 2, the third diaphragm 3, the fourth diaphragm 4, and the fifth diaphragm 5, which are stacked sequentially along a first direction to form four cavities.

[0056] The four cavities include:

[0057] The first cavity 6 is used to house the first negative electrode 10;

[0058] The second cavity 7 is used to house the reference electrode 11;

[0059] The third cavity 8 is used to place the positive electrode 12;

[0060] The fourth cavity 9 is used to house the second negative electrode 13;

[0061] The heights of the first diaphragm 1 to the fifth diaphragm 5 in the third direction are H1, H2, H3, H4, and H5, respectively; and satisfy: H1 = H5, H2 = H4, H1 = H2 * 3 / 4; 2mm ≤ H3 - H2 ≤ 3mm;

[0062] The first negative electrode 10 and the second negative electrode 13 are respectively at heights H in the third direction. 1负 H 2负 The condition is satisfied that 1mm ≤ H2 - H 1负 ≤2mm, 1mm≤H4-H 2负 ≤2mm;

[0063] The first diaphragm 1 to the fifth diaphragm 5 have widths W1, W2, W3, W4, and W5 in the second direction; the first negative electrode 10 and the second negative electrode 13 have widths W in the second direction. 1负 W 2负 Satisfying W1=W2=W3=W4=W5, W 1负 =W 2负 And 1mm≤W1-W 2负 ≤2mm.

[0064] It should be noted that the first, second, third, fourth, and fifth diaphragms are stacked sequentially, and the three sides of all diaphragms parallel to the width of the diaphragm bag are welded together with a soldering iron, forming four cavities. These cavities are used to house the first negative electrode, the reference electrode, the positive electrode, and the second negative electrode, respectively. To facilitate identification of each diaphragm cavity in the glove box and to easily open the diaphragm cavity to insert the electrode, the height dimensions of the diaphragms are designed according to the actual function of each cavity. For the first / fifth diaphragms, their purpose is to fix the first and second negative electrodes and they do not provide isolation between the positive and negative electrodes. If their height dimensions were the same as the second / third / fourth diaphragms, they would be difficult to identify in the glove box and difficult to open with tweezers. Therefore, their height dimensions are designed to be shorter than the second diaphragm, specifically about 3 / 4 of the second diaphragm's height. This ensures sufficient fixation of the negative electrode while facilitating operation in the glove box. The primary function of the second / fourth separator is to fix the positive and negative electrodes and isolate them. Therefore, its height is designed to be slightly larger than that of the negative electrode to ensure adequate isolation. The primary function of the third separator is to fix the reference electrode and isolate it from the positive electrode. Typically, the reference electrode is attached to the third separator using tape. However, if the third separator is designed to be at the same height as the second / fourth separator, the tape will inevitably cover part of the electrode material area. This not only affects capacity but also leads to uneven stress on the individual three-electrode battery in the fixture. Therefore, the third separator is designed to be slightly higher than the second / fourth separator. When attaching the reference electrode, the tape is applied to the area above the second / fourth separator to ensure that the tape does not cover the electrode material area.

[0065] In summary, the length of the short side direction (i.e., the bottom side) of the diaphragm bag in this embodiment is about 1-2 mm longer than the width of the negative electrode plate for easy insertion of the electrode plate; the dimension in the height direction of the diaphragm bag is based on the second / fourth diaphragm; the dimension in the height direction of the second / fourth diaphragm is 1-2 mm greater than the length direction of the negative electrode plate for overhang, effectively preventing short circuits caused by contact between the negative electrode and the reference electrode and between the positive electrode and the negative electrode; the dimension in the height direction of the first / fifth diaphragm is about 3 / 4 of the dimension in the height direction of the second / fourth diaphragm, effectively fixing the first negative electrode and the second negative electrode while facilitating the identification and expansion of the first cavity and the fourth cavity; the dimension in the height direction of the third diaphragm is about 2-3 mm greater than the dimension in the height direction of the second / fourth diaphragm so that when the reference electrode is fixed with glue, the tape can be fixed to the part higher than the dimension in the height direction of the second / fourth diaphragm, thus avoiding capacity loss caused by the tape covering the electrode plate material area; at the same time, it avoids uneven stress on the material area caused by sticking the tape to the material area.

[0066] Example 2

[0067] See Figure 2 : This embodiment also discloses a battery including a diaphragm bag: including a housing 100, and the diaphragm bag is arranged inside the housing 100;

[0068] The diaphragm bag includes four diaphragms, and the first diaphragm 1 to the fourth diaphragm 4 are stacked in sequence along the first direction to form three cavities; the three cavities include: a first cavity 6, a second cavity 7, and a third cavity 8;

[0069] A first sodium sheet 14 is arranged inside the first cavity 6;

[0070] A positive electrode plate or a negative electrode plate 15 is arranged inside the second cavity 7;

[0071] A second sodium sheet 16 is arranged inside the third cavity 8;

[0072] The heights of the first diaphragm 1 to the fourth diaphragm 4 in the third direction are H1, H2, H3, and H4 respectively, where H1 = H4 < H2 = H3;

[0073] The heights of the first sodium sheet 14 and the second sodium sheet 16 in the third direction are H Na1 and H Na2 , where H Na1 < H2, H Na2 < H3;

[0074] The first diaphragm 1 and the fourth diaphragm 4 are polypropylene diaphragms, and the second diaphragm 2 and the third diaphragm 3 are glass fiber diaphragms;

[0075] Among them, H1 = H2 * 3 / 4, and the positive electrode plate or the negative electrode plate 15 arranged inside the second cavity 7 has a height H 极片 , satisfying 1 mm ≤ H2 - H极片 ≤2mm, the second diaphragm 2 and the third diaphragm 3 have widths W2 and W3 in the second direction, W2 = W3, and the positive or negative electrode plate 15 disposed inside the second cavity 7 has a width W in the second direction. 极片 The condition is satisfied that 1mm ≤ W2 - W 极片 ≤2mm, H1, H4, W2, W3 satisfy, 4≤H1-W2≤5mm.

[0076] It should be noted that failure analysis typically uses a single half-cell to analyze the capacity loss of the positive and negative electrodes, i.e., using two sodium plates sandwiching one positive and one negative electrode. Multi-layer PP separator bags are usually used for manufacturing single half-cells. However, compared to large batteries (such as cylindrical and prismatic batteries), the biggest difference in single-cell batteries is their insufficient bonding. Even in a clamped state, the bonding force between the electrodes in a single cell is difficult to achieve the state of a large battery. This means that when evaluating the capacity of electrodes in poor condition using a single cell, its capacity is difficult to accurately reflect the true capacity of electrodes in a large battery. Therefore, this embodiment proposes a compromise solution: using a glass fiber separator as the separator for the single half-cell. Glass fiber separators not only have a much higher porosity than polypropylene separators but are also thicker, allowing for better utilization of the electrode capacity in a single cell. At the same time, glass fibers cannot be welded with a soldering iron, complicating the manufacturing of the separator bag. Therefore, this embodiment proposes combining the glass fiber separator with a polypropylene separator to assemble a "stepped composite separator bag". The first, second, third, and fourth diaphragms are stacked sequentially. The first and fourth diaphragms are polypropylene diaphragms, while the second and third diaphragms are glass fiber diaphragms. The three sides of the first and fourth diaphragms, parallel to the width of the diaphragm bag, are welded together with a soldering iron. The second and third diaphragms are placed in the middle, forming three cavities. These cavities are used to hold the first sodium electrode, the positive / negative electrode, and the second sodium electrode, respectively. To facilitate identification of each diaphragm cavity in the glove box and to easily open the diaphragm cavities to insert the electrodes, the diaphragm dimensions along their long sides are designed according to the actual function of each cavity. The first and fourth diaphragms are used to fix the first and second sodium electrodes and do not serve as a separator between the electrodes. If their height were the same as the second and third diaphragms, they would be difficult to identify in the glove box and difficult to open with tweezers. Therefore, their height is designed to be shorter than the second and third diaphragms, specifically 3 / 4 of their height. This design effectively secures the sodium sheet and facilitates operation within the glove box. The second / third diaphragm's primary function is to secure the positive or negative electrode and isolate the electrodes. Therefore, its height is designed to be slightly larger than that of the sodium sheet to ensure adequate electrode isolation.

[0077] In summary, the bottom edge length of the second / third diaphragm is approximately 1-2 mm longer than the width of the positive / negative electrode plates to facilitate electrode insertion. The bottom edge length of the first / fourth diaphragm, taking into account the thickness of the second / third diaphragm and the sodium plate, is approximately 4-5 mm longer than the second / third diaphragm to secure it and allow for sodium plate insertion. The height dimension of the second / third diaphragm is 1-2 mm greater than the length dimension of the positive / negative electrode plates for overhang, effectively preventing short circuits caused by contact between the positive / negative electrodes and the sodium plate. The height dimension of the first / fourth diaphragm is approximately 3 / 4 the height dimension of the second / third diaphragm, effectively securing the first and second sodium plates while facilitating the differentiation and opening of the first and third cavities.

[0078] In failure analysis, single-cell half-cells are typically fabricated using polypropylene separators, the same type used in large-cell batteries. The biggest difference between single-cell half-cells and large-cell batteries (such as cylindrical or prismatic cells) lies in their insufficient adhesion. Even in a clamped state, the adhesion between the electrodes in a single-cell half-cell is difficult to match that of a large-cell battery. This means that when evaluating the capacity of electrodes in poor condition using a single-cell half-cell, the capacity is unlikely to accurately reflect the true capacity of the electrodes in the large-cell battery. Therefore, this embodiment proposes a compromise solution: using a glass fiber separator as the separator for single-cell half-cells. The glass fiber separator not only has a much higher porosity than the polypropylene separator but is also thicker, allowing it to better utilize the electrode capacity within a single-cell half-cell. To highlight the optimization effect of the "stepped composite separator bag," the following experiment was designed: Negative electrode sheets were obtained before cycling (without degradation) and after cycling (with significant degradation). Negative half-cells were fabricated using both the "stepped composite separator bag" and a "polypropylene stepped multilayer separator bag" (with the same structure as the "stepped composite separator bag," but using polypropylene separators). Charging curves were obtained, as shown below. Figure 3 and Figure 4 As shown. The results showed that for the negative electrode sheet before cycling and before deterioration, the capacity difference of the negative electrode half-cell made using the two types of separator bags was small ( Figure 3 For negative electrode sheets that have deteriorated significantly after cycling, the capacity of a negative electrode half-cell made with a "stepped composite separator bag" is much higher than that made with a "polypropylene stepped multilayer separator bag." In other words, the "stepped composite separator bag" is more conducive to maximizing the true capacity of the negative electrode sheet.

[0079] The above description is only a preferred embodiment of the present utility model and is not intended to limit the present utility model. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present utility model should be included within the protection scope of the present utility model.

Claims

1. A diaphragm bag, characterized in that, include: The diaphragm has N diaphragms, and the first diaphragm to the Nth diaphragm are stacked sequentially along a first direction; The diaphragm has N first side edges and N second side edges on both sides in the second direction, and the N first side edges and N second side edges are welded in the first direction to form N-1 cavities; The diaphragm has a height H in the third direction; When N is an odd number, the height H increases sequentially from the first diaphragm to the (N / 2+1)th diaphragm; and decreases sequentially from the (N / 2+1)th diaphragm to the Nth diaphragm. When N is even, the height H increases sequentially from the first diaphragm to the N / 2th diaphragm; the height H decreases sequentially from the N / 2+1th diaphragm to the Nth diaphragm, and the height H of the N / 2th diaphragm is equal to the height of the N / 2+1th diaphragm. The first direction is parallel to the thickness of the diaphragm bag, the second direction is parallel to the width of the diaphragm bag, and the third direction is parallel to the height of the diaphragm bag.

2. The diaphragm bag according to claim 1, characterized in that, The diaphragm bag includes five diaphragms, with the first to fifth diaphragms stacked sequentially along the first direction to form four cavities; The four cavities include: The first cavity is used to house the first negative electrode; The second cavity is used to house the reference electrode; The third cavity is used to house the positive electrode; The fourth cavity is used to house the second negative electrode.

3. The diaphragm bag according to claim 2, characterized in that, The heights of the first to fifth diaphragms in the third direction are H1, H2, H3, H4, and H5, respectively; and satisfy: H1 = H5, H2 = H4, H1 = H2 * 3 / 4; 2mm ≤ H3 - H2 ≤ 3mm.

4. The diaphragm bag according to claim 3, characterized in that, The heights of the first negative electrode and the second negative electrode in the third direction are H1 negative and H2 negative, respectively, satisfying that 1mm≤H2-H1 negative≤2mm and 1mm≤H4-H2 negative≤2mm.

5. The diaphragm bag according to claim 2, characterized in that, The first to fifth diaphragms have widths W1, W2, W3, W4, and W5 in the second direction; the first negative electrode and the second negative electrode have widths W in the second direction. 1负 W 2负 Satisfying W1=W2=W3=W4=W5, W 1负 =W 2负 And 1mm≤W1-W 2负 ≤2mm.

6. A battery comprising the diaphragm bag of claim 1, characterized in that, It also includes a housing, and the diaphragm bag is disposed inside the housing; The diaphragm bag includes four diaphragms, which are stacked sequentially along the first direction to form three cavities; the three cavities include: a first cavity, a second cavity, and a third cavity; The first cavity contains a first sodium sheet; The second cavity is provided with a positive electrode or a negative electrode; The third cavity is equipped with a second sodium plate; The heights of the first to fourth diaphragms in the third direction are H1, H2, H3, and H4, respectively, where H1 = H4 < H2 = H3; The heights of the first sodium tablet and the second sodium tablet in the third direction are H Na1 and H Na2 , where H Na1 <H2, H Na2 <H3; The first and fourth diaphragms are polypropylene diaphragms, and the second and third diaphragms are glass fiber diaphragms.

7. The battery according to claim 6, characterized in that, H1 = H2 * 3 / 4.

8. The battery according to claim 6, characterized in that, The positive or negative electrode plate disposed inside the second cavity has a height H in the third direction. 极片 The condition is satisfied that 1mm ≤ H2 - H 极片 ≤2mm.

9. The battery according to claim 6, characterized in that, The second and third diaphragms have widths W2 and W3 in the second direction, where W2 = W3. The positive or negative electrode plate disposed inside the second cavity has a width W in the second direction. 极片 The condition is satisfied that 1mm ≤ W2 - W 极片 ≤2mm.

10. The battery according to claim 6, characterized in that, H1, H4, W2, and W3 satisfy the condition that 4 ≤ H1 - W2 ≤ 5 mm.

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