Diaphragm and sodium ion battery
By incorporating a layer in the sodium-ion battery separator for adsorbing carbon dioxide and water, the problem of water damaging the SEI in sodium-ion batteries is solved, thereby improving battery safety and cycle performance.
Patent Information
- Application Number
- CN202423161114.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-20
- Publication Date
- 2026-02-13
- Estimated Expiration
- 2034-12-20
AI Technical Summary
Sodium-ion batteries are sensitive to moisture. Trace amounts of water can damage the solid electrolyte interphase (SEI) film on the surface of the negative electrode, leading to capacity decay and battery swelling, which poses a safety risk.
A separator is designed, comprising a first adsorption layer for adsorbing carbon dioxide on the positive electrode side and a second adsorption layer for adsorbing water on the negative electrode side, which are respectively composed of a polyimide-based covalent organic framework layer and a zeolite molecular sieve layer. The separator adsorbs carbon dioxide and moisture generated in the battery, reducing the impact of gas accumulation on the battery.
It improves the safety and cycle performance of sodium-ion batteries by rapidly adsorbing carbon dioxide and water, slowing down the decomposition of the negative electrode SEI, reducing battery volume expansion, and enhancing battery stability and lifespan.
Smart Images
Figure CN223911803U_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The utility model relates to the technical field of battery, especially a kind of diaphragm and sodium ion battery. BACKGROUND
[0002] Compared with lithium ion battery, sodium ion battery is more sensitive to moisture, and trace water exists in electrolyte due to process limitation, which can not be removed. These water will destroy the solid electrolyte interface film (SEI) on the surface of the negative electrode during the first charge and discharge of sodium ion battery, and accelerate the capacity decay in the battery cycle process. And, in the process of sodium ion battery cycle charge and discharge, accompanied by positive material oxidation, surface residual alkali and electrolyte decomposition, etc. These side reactions will produce carbon dioxide, resulting in battery expansion, with safety risk, reduce cycle performance.
[0003] Therefore, it is urgent to develop a new type of diaphragm to adsorb trace water in electrolyte and carbon dioxide generated in the battery cycle process, to improve the safety performance and cycle performance of sodium ion battery. UTILITY MODEL CONTENT
[0004] The utility model aims at providing a kind of diaphragm and sodium ion battery to solve the problems in the above background.
[0005] The technical scheme of the utility model comprises: a diaphragm, the diaphragm comprises:
[0006] Polyolefin membrane layer;
[0007] First adsorption layer, the first adsorption layer is arranged on the positive side of the polyolefin membrane layer, for adsorbing carbon dioxide;
[0008] And second adsorption layer, the second adsorption layer is arranged on the negative side of the polyolefin membrane layer, for adsorbing water.
[0009] Further, the polyolefin membrane layer is polyethylene membrane layer or polypropylene membrane layer with thickness of 6-15 μm.
[0010] Further, the first adsorption layer is covalent organic framework layer containing polyimide group with thickness of 1-2 μm.
[0011] Further, the particle size of the covalent organic framework layer is 0.8-1 μm.
[0012] Further, the second adsorption layer is molecular sieve layer with thickness of 0.5-1 μm.
[0013] Further, the molecular sieve layer is zeolite molecular sieve layer.
[0014] Further, the particle size of the molecular sieve layer is 0.2-0.5 μm.
[0015] The technical scheme of the utility model further includes: a sodium ion battery, the sodium ion battery includes a positive electrode, a negative electrode, an electrolyte and the separator as described above.
[0016] Further, the positive electrode is correspondingly arranged on both sides of the negative electrode, the separator is arranged between the positive electrode and the negative electrode, the first adsorption layer is located between the positive electrode and the separator, and the second adsorption layer is located between the negative electrode and the separator.
[0017] The utility model has the beneficial effect that: the first adsorption layer and the second adsorption layer with different adsorption characteristics are arranged in the separator, the positions of the first adsorption layer and the second adsorption layer are designed according to the distribution of impurities (carbon dioxide and water) in the battery and the influence on the structure of each part of the battery, carbon dioxide generated by side reactions on the positive electrode side and water in the electrolyte are quickly adsorbed, the influence of gas accumulation on the volume expansion of the battery is reduced, the damage of water to the negative electrode SEI is reduced, and the safety performance and cycle performance of the sodium ion battery are improved. BRIEF DESCRIPTION OF DRAWINGS
[0018] Figure 1 It is the structure schematic diagram of the sodium ion battery in the utility model embodiment.
[0019] Among them:
[0020] 1, the positive electrode;
[0021] 2, the separator; 21, the first adsorption layer; 22, the polyolefin film layer; 23, the second adsorption layer;
[0022] 3, the negative electrode. DETAILED DESCRIPTION
[0023] In order to make the purpose, technical scheme and advantage of the utility model embodiment more clear, the technical scheme in the utility model embodiment will be clearly and completely described below in conjunction with the drawings in the utility model embodiment. Obviously, the described embodiment is a part of the embodiment of the utility model, rather than all the embodiments. Based on the embodiment in the utility model, all other embodiments obtained by the person skilled in the art without creative labor belong to the scope of protection of the utility model.
[0024] Referring to the accompanying drawings, this embodiment provides a membrane, the structure of which specifically includes a first adsorption layer 21, a polyolefin membrane layer 22, and a second adsorption layer 23. The first adsorption layer 21 and the second adsorption layer 23 are respectively disposed on both sides of the polyolefin membrane layer 22. The first adsorption layer 21 is located on the positive electrode side of the polyolefin membrane layer 22 (i.e., the side of the polyolefin membrane layer 22 close to the positive electrode 1 of the battery) and is used to adsorb carbon dioxide. The second adsorption layer 23 is located on the negative electrode side of the polyolefin membrane layer 22 (i.e., the side of the polyolefin membrane layer 22 close to the negative electrode 3 of the battery) and is used to adsorb water.
[0025] Although sodium-ion batteries generate carbon dioxide during charge-discharge cycles due to the decomposition of residual alkali (such as sodium carbonate) in the positive electrode active material and the decomposition of the electrolyte, the oxidation of the positive electrode material and the decomposition of residual alkali on the surface are the main contributors to the increase in carbon dioxide within the battery. By placing the first adsorption layer 21 for adsorbing carbon dioxide on the positive electrode side of the polyolefin film layer 22, carbon dioxide generated by the decomposition on the positive electrode side of the battery can be quickly adsorbed, preventing carbon dioxide from accumulating in the battery for a long time and causing the battery volume to expand. This has a better effect on improving the battery's safety and cycle performance.
[0026] Furthermore, trace amounts of water in the electrolyte primarily damage the solid electrolyte interphase (SEI) film on the negative electrode surface. Since water is constantly moving and diffusing within the battery, it is impractical to use a second adsorption film layer to constantly follow the movement of water molecules and adsorb water. Instead, placing the second adsorption layer 23 for adsorbing water on the negative electrode side of the polyolefin film layer 22 can quickly reduce the water content near the negative electrode surface, slow down the decomposition rate of the negative electrode SEI, or prevent its decomposition, thus providing a better effect on improving the battery cycle performance.
[0027] As an example, the polyolefin film layer 22 in this embodiment can be a polyethylene film layer or a polypropylene film layer with a thickness of 6 to 15 μm to ensure the migration efficiency of components in the electrolyte and to ensure the normal charge and discharge performance of the battery.
[0028] As an example, the first adsorption layer 21 in this embodiment can be a covalent organic framework layer containing polyimide groups with a thickness of 1-2 μm and a particle size of 0.8-1 μm. The covalent organic framework layer containing polyimide groups is obtained by imidizing covalent organic framework materials (COFs). Optional imidizing raw materials include 1,4,5,8-naphthalenetetracarboxylic anhydride, tris(4-aminophenyl)amine, etc. Materials containing polyimide groups have excellent thermal and chemical stability. Covalent organic framework materials have a porous structure and a large specific surface area. The polar groups on the surface increase the affinity for carbon dioxide, which can effectively adsorb carbon dioxide, rapidly reduce the carbon dioxide content in the battery, and prevent battery volume expansion.
[0029] As an example, the second adsorption layer 23 in the embodiment can be a molecular sieve layer with a thickness of 0.5-1 μm and a particle size of 0.2-0.5 μm, and preferably a zeolite molecular sieve layer.
[0030] The zeolite molecular sieve layer contains a hydrated crystalline silicate, has a crystal structure and characteristics, and has a solid skeleton on the surface, and has a strong surface interaction with water molecules containing polar groups, thereby adsorbing water molecules. The pores are connected by channels, and water molecules pass through the channels. Due to the crystalline nature of the pores, the pore size distribution of the zeolite molecular sieve is very uniform, and a large amount of water can be adsorbed in a short time, and the process of adsorbing water has high selectivity, which can quickly reduce the water content near the negative electrode in the battery and alleviate the decomposition of the negative electrode SEI.
[0031] The embodiment also provides a sodium ion battery, which comprises a positive electrode 1, the separator 2 described above, a negative electrode 3, an electrolyte (not shown in the figure), and conventional packaging materials and other functional components, the positive electrode 1 is arranged on both sides of the negative electrode 3, the separator 2 is arranged between the positive electrode 1 and the negative electrode 3, the first adsorption layer 21 is located between the positive electrode 1 and the separator 2, and the second adsorption layer 23 is located between the negative electrode 3 and the separator 2. The electrolyte is filled between the positive electrode 1 and the negative electrode 3.
[0032] Compared with the prior art, the beneficial effects of the utility model lie in that the first adsorption layer 21 and the second adsorption layer 23 with different adsorption characteristics are arranged in the separator 2, the positions of the first adsorption layer 21 and the second adsorption layer 23 are designed according to the distribution of impurities (carbon dioxide and water) in the battery and the influence on the structure of each part of the battery, carbon dioxide generated by decomposition of the positive electrode 1 and water near the negative electrode 3 are quickly adsorbed, the influence of gas accumulation on the volume expansion of the battery is reduced, the decomposition efficiency of water on the negative electrode SEI is reduced, and the safety performance and cycle performance of the sodium ion battery are improved.
[0033] The above is the preferred embodiment of the utility model, and it should be pointed out that for ordinary skilled persons in the technical field, some improvements and refinements can be made without departing from the principles of the utility model, and these improvements and refinements should also be regarded as the protection scope of the utility model.
Claims
1. A diaphragm, characterized in that, The diaphragm includes: Polyolefin film layer; A first adsorption layer is disposed on the positive electrode side of the polyolefin membrane and is used to adsorb carbon dioxide. And a second adsorption layer, which is disposed on the negative electrode side of the polyolefin membrane and is used to adsorb water.
2. The diaphragm according to claim 1, characterized in that, The polyolefin film layer is a polyethylene film layer or a polypropylene film layer with a thickness of 6~15μm.
3. The diaphragm according to claim 1, characterized in that, The second adsorption layer is a molecular sieve layer with a thickness of 0.5~1μm.
4. A sodium-ion battery, characterized in that, The sodium-ion battery includes a positive electrode, a negative electrode, an electrolyte, and a separator as described in any one of claims 1-3.
5. The sodium-ion battery according to claim 4, characterized in that, The positive electrode is disposed on both sides of the negative electrode, and the membrane is disposed between the positive electrode and the negative electrode. The first adsorption layer is located between the positive electrode and the membrane, and the second adsorption layer is located between the negative electrode and the membrane.