Three-electrode button cell and battery pack

Abstract

The utility model discloses a three-electrode button cell and a cell pack, and belongs to the technical field of cells. Comprising a shell and a battery assembly, the shell comprises a positive electrode shell and a negative electrode shell covering the positive electrode shell, a containing space is formed between the positive electrode shell and the negative electrode shell, and the battery assembly is arranged in the containing space and comprises a positive electrode part and a negative electrode part; the reference electrode is arranged above the positive electrode part; the negative electrode part is arranged above the reference electrode; the reference electrode comprises a metal wire and a lithium titanate layer coated on the surface of the metal wire, a first end of the reference electrode is arranged in the positive electrode shell, and a second end of the reference electrode extends out of the accommodating space and is folded to form a first convex structure with a first height. The technical scheme has the beneficial effects that the outer layer of the reference electrode is coated with the lithium titanate layer, so that the battery performance monitoring result is more accurate, the side reaction and polarization influence are reduced, the experimental repeatability is good, and the formed button battery is small in size and stable in structure.

Description

Technical Field

[0001] This utility model relates to the field of battery technology, and in particular to a button cell battery and battery pack. Background Technology

[0002] A three-electrode cell consists of a working electrode (research electrode), a reference electrode, and an auxiliary electrode. A high input impedance exists between the reference and working electrodes due to the potential difference. Current flows between the working and auxiliary electrodes, while almost no current flows through the reference electrode, allowing for relatively accurate measurement of the potential change of the working electrode relative to the reference electrode. When studying lithium intercalation at the negative electrode during fast charging of lithium batteries, the potentials of the positive and negative electrodes can be tested separately.

[0003] In existing technologies, lithium sheets or bars are commonly used as reference electrodes in three-electrode systems. Although lithium metal has a standard potential and high exchange current density, it is sensitive to water and oxygen and is prone to reaction. During the charging and discharging process of the battery cell, lithium metal is easily decomposed by solvents, thus losing its function as a reference electrode and making it difficult to ensure the smooth progress of the experiment. Utility Model Content

[0004] The purpose of this utility model is to provide a three-electrode button battery to solve the above-mentioned technical problems;

[0005] The purpose of this utility model is also to provide a battery pack that solves the above-mentioned technical problems;

[0006] A three-electrode coin cell battery includes a casing and a battery assembly. The casing includes a positive electrode casing and a negative electrode casing covering the positive electrode casing. A receiving space is provided between the positive electrode casing and the negative electrode casing, and the battery assembly is disposed within the receiving space. The battery assembly includes...

[0007] Positive electrode section;

[0008] A reference electrode is disposed above the positive electrode portion;

[0009] The negative electrode portion is located above the reference electrode;

[0010] The reference electrode includes a metal wire and a lithium titanate layer covering the surface of the metal wire. The first end of the reference electrode is disposed inside the positive electrode shell, and the second end of the reference electrode extends out of the accommodating space and is folded to form a first protrusion structure of a first height.

[0011] Preferably, the positive electrode portion includes,

[0012] A positive electrode plate is disposed above the positive electrode shell;

[0013] The first diaphragm is disposed above the positive electrode plate;

[0014] The first gasket is disposed above the first diaphragm;

[0015] The second diaphragm is positioned above the first washer.

[0016] Preferably, the negative electrode portion includes,

[0017] A third diaphragm is disposed above the reference electrode;

[0018] The negative electrode is disposed above the third diaphragm;

[0019] The first pad is disposed above the negative electrode plate;

[0020] The second gasket is positioned above the first gasket.

[0021] Preferably, one end of the first washer extends out of the accommodating space and is disposed between the positive electrode shell and the second end of the reference electrode.

[0022] Preferably, the positive electrode is circular in shape, with a diameter of 13mm to 15mm, the diameters of the first and second separators are 17mm to 19mm, and the thicknesses of the first and second separators are 10μm to 15μm.

[0023] Preferably, the negative electrode sheet is circular in shape, the diameter of the negative electrode sheet is 15mm to 17mm, the diameter of the third separator is 17mm to 19mm, and the thickness of the third separator is 10μm to 15μm.

[0024] Preferably, the second gasket is wavy.

[0025] Preferably, the reference electrode has a diameter of 0.25 mm, the first end of the reference electrode is flat, and the size of the first end of the reference electrode is 0.5 mm × 0.4 mm.

[0026] Preferably, the first end of the reference electrode is located within the range of the positive electrode sheet, and the portion of the reference electrode near the second end is folded to form a second protrusion structure of a second height;

[0027] One end of the negative electrode shell is embedded between the first protruding structure and the second protruding structure.

[0028] A battery pack comprising any one of the three-electrode coin cells described in any one of the claims.

[0029] The beneficial effects of this invention are: coating the outer layer of the reference electrode with a lithium titanate layer makes the battery performance monitoring results more accurate, reduces the effects of side reactions and polarization, improves experimental repeatability, and results in a small-sized and stable coin cell. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the overall structure of the three-electrode button cell of this utility model;

[0031] Figure 2 This is a schematic diagram of the cross-sectional structure of the three-electrode button cell of this utility model.

[0032] In the attached diagram: 1. Positive electrode shell; 2. Negative electrode shell; 3. Positive electrode portion; 31. Positive electrode plate; 32. First diaphragm; 33. First gasket; 34. Second diaphragm; 4. Reference electrode; 5. Negative electrode portion; 51. Third diaphragm; 52. Negative electrode plate; 53. First gasket; 54. Second gasket. Detailed Implementation

[0033] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0034] It should be noted that, unless otherwise specified, the embodiments and features described in these embodiments can be combined with each other.

[0035] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but this is not intended to limit the present invention.

[0036] A three-electrode coin cell, such as Figure 1 , Figure 2 As shown, the device includes a housing and a battery assembly. The housing includes a positive electrode shell 1 and a negative electrode shell 2 covering the positive electrode shell 1. A receiving space is provided between the positive electrode shell 1 and the negative electrode shell 2, and the battery assembly is disposed within the receiving space. The battery assembly includes...

[0037] Positive electrode section 3;

[0038] The reference electrode 4 is disposed above the positive electrode portion 3;

[0039] The negative electrode 5 is located above the reference electrode 4;

[0040] The reference electrode 4 includes a metal wire and a lithium titanate layer covering the surface of the metal wire. The first end of the reference electrode 4 is disposed inside the positive electrode shell 1, and the second end of the reference electrode 4 extends out of the accommodating space and is folded to form a first protrusion structure of a first height.

[0041] Specifically, this invention provides a three-electrode coin cell battery. A lithium titanate layer is coated on the outer layer of the reference electrode 4, providing a stable reference during battery charging and discharging, thus making battery performance monitoring results more accurate. Simultaneously, fewer side reactions are observed, ensuring the accuracy and repeatability of the experiment. One end of the reference electrode 4 extends out of the accommodating space and is folded into a first protruding structure, making the overall battery structure stable.

[0042] In a preferred embodiment, the positive electrode portion 3 includes,

[0043] Positive electrode plate 31 is disposed above positive electrode shell 1;

[0044] The first diaphragm 32 is disposed above the positive electrode plate 31;

[0045] The first washer 33 is disposed above the first diaphragm 32;

[0046] The second diaphragm 34 is positioned above the first washer 33.

[0047] Specifically, the positive electrode section 3 adopts a layered structure of positive electrode sheet 31, first separator 32, first gasket 33, and second separator 34. The separator can prevent the positive and negative electrodes from directly contacting each other and causing a short circuit, thus ensuring the safety and stability of the battery. The gasket helps to fix the layers of the structure, so that the internal components of the battery maintain a stable relative position, which is conducive to the stable performance of the battery.

[0048] In a preferred embodiment, the negative electrode portion 5 includes,

[0049] The third diaphragm 51 is disposed above the reference electrode 4;

[0050] The negative electrode 52 is disposed above the third diaphragm 51;

[0051] The first pad 53 is located above the negative electrode plate 52;

[0052] The second gasket 54 is located above the first gasket 53.

[0053] Specifically, the negative electrode portion 5 has a layered structure of the third separator 51, the negative electrode sheet 52, the first gasket 53, and the second gasket 54. The third separator 51 also serves to prevent short circuits between the positive and negative electrodes. The gaskets can buffer and fix the negative electrode sheet 52, making its position inside the battery stable and ensuring the stability of the battery during charging and discharging.

[0054] In a preferred embodiment, one end of the first washer 33 extends out of the accommodating space and is located between the positive electrode shell 1 and the second end of the reference electrode 4. This can further fix the position of the reference electrode 4, enhance the stability of the internal structure of the battery, reduce the relative displacement between components, and ensure the reliability of the battery during use.

[0055] In a preferred embodiment, the positive electrode 31 is circular in shape, with a diameter of 13mm to 15mm, and the diameters of the first separator 32 and the second separator 34 are 17mm to 19mm, with a thickness of 10μm to 15μm.

[0056] The negative electrode 52 is circular in shape and has a diameter of 15mm to 17mm. The third diaphragm 51 has a diameter of 17mm to 19mm and a thickness of 10μm to 15μm.

[0057] Specifically, the diameter of the positive electrode 31 is 14 mm, the diameters of the first separator 32 and the second separator 34 are 18 mm, and the thicknesses of the first separator 32 and the second separator 34 are 12 μm. The diameter of the negative electrode 52 is 16 mm, the diameter of the third separator 51 is 18 mm, and the thickness of the third separator 51 is 12 μm. These appropriate dimensions ensure a tight fit between the positive electrode 31 and the separators, reducing internal voids, lowering the battery's internal resistance, improving ion transport efficiency, and thus enhancing the battery's charge / discharge performance and energy density.

[0058] The diameter of the negative electrode 52, the diameter and thickness of the third separator 51 are matched with the size design of the positive electrode 3, which is conducive to the uniform distribution of the electric field inside the battery, promotes the efficient transport of lithium ions between the positive and negative electrodes, and improves the charging and discharging performance of the battery.

[0059] In a preferred embodiment, the second gasket 54 is wavy in shape, which can act as a buffer during battery assembly and use, relieving stress caused by vibration or compression of the internal components of the battery, protecting the internal structure of the battery, and extending the battery's lifespan; at the same time, it also helps to improve the internal pressure distribution of the battery, making the battery performance more stable.

[0060] Specifically, the thickness of the first washer 33 is greater than the thickness of the second washer 54 and the first washer 53. The first washer 53 is a stainless steel washer, and the first washer 33 is a plastic washer.

[0061] In a preferred embodiment, the reference electrode 4 has a diameter of 0.25 mm, and the first end of the reference electrode 4 is flat, with a size of 0.5 mm × 0.4 mm.

[0062] Specifically, the flat shape increases the coating area of ​​lithium titanate, improves the electrochemical performance of the reference electrode 4, and enables it to monitor battery potential changes more accurately. The flat design also facilitates close contact between the reference electrode 4 and other components, reduces contact resistance, and improves the overall performance of the battery.

[0063] In a preferred embodiment, the first end of the reference electrode 4 is located within the area of ​​the positive electrode 31, and the portion of the reference electrode 4 near the second end is folded to form a second protrusion structure of a second height.

[0064] One end of the negative electrode shell 2 is embedded between the first protrusion structure and the second protrusion structure.

[0065] Specifically, the first end of the reference electrode 4 is located within the range of the positive electrode plate 31, and the portion near the second end is folded to form a second protruding structure. The negative electrode shell 2 is embedded between the two protruding structures, which facilitates the assembly and sealing of the battery, enhances the stability of the battery structure, prevents the displacement of internal components, and ensures the reliability of the battery.

[0066] A battery pack, comprising the aforementioned three-electrode coin cell, possesses all the advantages of the three-electrode coin cell, which will not be elaborated here. Applying it to a battery pack can reduce production costs while ensuring battery pack performance, facilitating large-scale production and application. Simultaneously, the precise monitoring performance of the three-electrode coin cell helps optimize the battery pack management system, improving the overall performance and safety of the battery pack.

[0067] The preparation process of lithium titanate (LTO) slurry includes the following steps: pre-preparation of lithium titanate (85-91%), PVDF (3-5%), conductive agent (4-6%), and malonic acid (2-4%). ​​The preparation steps are as follows:

[0068] Lithium titanate and conductive agent are baked at 120℃~140℃ for 4~5 hours. After baking, they are cooled to 40℃~55℃ in dry air. Lithium titanate, PVDF and conductive agent dry powder are mixed for 1h~2h. Then, they are added to the solvent NMP in 2~4 portions, with an interval of 20min~30min between each addition. After stirring for 4h~5h, malonic acid is added. Stirring is continued and vacuum is applied. After stirring for 1h~2h, the mixture is sieved through a 150~180 mesh sieve to obtain lithium titanate anode slurry.

[0069] The manufacturing process of coated lithium titanate copper wire is as follows.

[0070] Enameled copper wire with a diameter of 0.25 mm is immersed in a 7%–15% dilute sulfuric acid solution for 1.5 hours to remove the surface oxide layer. The head is first rolled into a flat shape of approximately 0.5 mm × 0.4 mm, and then coated with lithium titanate to increase the coating area. It is then washed with distilled water 3–5 times and dried in an oven. After drying, the copper wire is immersed in lithium titanate slurry. After the slurry is applied, the copper wire is dried in an 85°C oven for later use.

[0071] The assembly process of the button-type three-electrode includes,

[0072] Step S0: Assemble inside the glove box, such as... Figure 1 Assemble from bottom to top;

[0073] Step S1: Place the positive electrode plate 31 inside the positive electrode shell 1;

[0074] Step S2: Insert the first diaphragm 32 and add 40 μl of electrolyte;

[0075] Step S3: Place the first washer 33 on the first diaphragm 32;

[0076] Step S4: Place the second separator 34 on the gasket, place the reference electrode 4 on the second separator 34, fold the reference electrode 4 coated with lithium titanate into a circle, and place the active lithium titanate on the reference electrode 4 within the range of the positive electrode 31.

[0077] Step S5: Place the third diaphragm 51 on the reference electrode 4, then add 40 μl of electrolyte. Fold the reference electrode 4 appropriately as follows: Figure 2 The shape is designed to allow for a snap-on three-electrode seal;

[0078] Step S6: Insert the first gasket 53 and the second gasket 54 in sequence;

[0079] Step S7: Drill a semicircle with a diameter of 0.25mm into the plastic rubber ring of the negative electrode shell 2 (with plastic sealing ring) so that the copper wire can be led out;

[0080] Step S8: After sealing the battery with a sealing machine, the battery assembly is completed (pressure 800Pa, pressing for 5s). If the pressure is too high, the electrolyte in the button battery will be easily squeezed out; if the pressure is too low, the internal resistance of the button battery will be too large.

[0081] Step S9: After encapsulation, seal the notch in the negative electrode shell 2 with sealant material to prevent leakage.

[0082] After assembly, the reliability of the coin cell was verified through testing. Monitoring the potential changes of the reference electrode 4's negative electrode pair at 25℃, 35℃, and 45℃ allowed observation of the lithium plating state on the negative electrode surface during charging and discharging. The charging current was adjusted in real-time to maintain the voltage of the reference electrode 4's negative electrode pair above 1.55V to achieve the fastest possible charging speed.

[0083] During the lithium plating process, the reference electrode 4 is used as the negative electrode and the positive electrode is used as the positive electrode. First, a charge-discharge cycle of C / 16 is performed and recorded as C1. Then, the capacity of C1 is added, which completes the process of lithium titanate reaching a suitable and stable voltage platform.

[0084] The testing process is as follows:

[0085] The first step is to perform a 5-minute reset.

[0086] The second step is to charge the reference electrode 4 pairs of negative electrodes to 1.55V.

[0087] The third step involves gradually decreasing the 3C current to charge at a constant potential.

[0088] The fourth step ends when the voltage reaches 1.55V between the negative electrode and the copper wire.

[0089] The time required to charge to 80% in the third step under 3C conditions at 25℃, 35℃, and 45℃ shows a decreasing trend.

[0090] Reference electrode 4 is a 25-micrometer diameter lithium titanate-coated electrode that does not affect lithium-ion transport between the positive and negative electrodes. It allows for effective in-situ monitoring of changes in the positive and negative electrode potentials and impedance during lithium battery charging and discharging. It effectively monitors the potential changes of the positive and negative electrodes, exhibits electrochemical stability, high potential, and fewer side reactions than lithium metal. Furthermore, due to its two-phase mechanism and lack of polarization, it can more accurately obtain the negative electrode potential and changes in the lithium intercalation state. Monitoring data at different temperatures, negative electrode potentials, and fast charging are shown in the table below.

[0091]

[0092] This invention is based on button cells. Compared to pouch cells and steel-cased cells, button cells are smaller, easier to operate, require fewer consumables, have lower costs, are simpler to operate, have lower manufacturing costs, better experimental repeatability, and can be used in large quantities. Lithium titanate uses a material with a specific plateau potential. As a reference electrode 4, lithium titanate is electrochemically stable, has a high potential, fewer side reactions than lithium metal, and is non-polarized.

[0093] The above description is only a preferred embodiment of the present utility model and does not limit the implementation method and protection scope of the present utility model. Those skilled in the art should realize that all solutions obtained by equivalent substitutions and obvious changes made based on the description and illustrations of the present utility model should be included within the protection scope of the present utility model.

Claims

1. A three-electrode coin cell, characterized in that, The device includes a housing and a battery assembly. The housing includes a positive electrode shell and a negative electrode shell covering the positive electrode shell. A receiving space is provided between the positive electrode shell and the negative electrode shell, and the battery assembly is disposed within the receiving space. The battery assembly includes... Positive electrode section; A reference electrode is disposed above the positive electrode portion; The negative electrode portion is located above the reference electrode; The reference electrode includes a metal wire and a lithium titanate layer covering the surface of the metal wire. The first end of the reference electrode is disposed inside the positive electrode shell, and the second end of the reference electrode extends out of the accommodating space and is folded to form a first protrusion structure of a first height.

2. The three-electrode coin cell according to claim 1, characterized in that, The positive electrode portion includes, A positive electrode plate is disposed above the positive electrode shell; The first diaphragm is disposed above the positive electrode plate; The first gasket is disposed above the first diaphragm; The second diaphragm is positioned above the first washer.

3. The three-electrode coin cell according to claim 1, characterized in that, The negative electrode portion includes, A third diaphragm is disposed above the reference electrode; The negative electrode is disposed above the third diaphragm; The first pad is disposed above the negative electrode plate; The second gasket is positioned above the first gasket.

4. The three-electrode coin cell according to claim 2, characterized in that, One end of the first washer extends out of the accommodating space and is located between the positive electrode shell and the second end of the reference electrode.

5. The three-electrode coin cell according to claim 2, characterized in that, The positive electrode is circular in shape, and the diameter of the positive electrode is [missing information]. The diameters of the first diaphragm and the second diaphragm are The thicknesses of the first diaphragm and the second diaphragm are .

6. The three-electrode coin cell according to claim 3, characterized in that, The negative electrode is circular in shape, and the diameter of the negative electrode is [missing information]. The diameter of the third diaphragm is The thickness of the third diaphragm is .

7. The three-electrode coin cell according to claim 3, characterized in that, The second gasket has a wavy shape.

8. The three-electrode coin cell according to claim 1, characterized in that, The reference electrode has a diameter of 0.25 mm, and its first end is flat. The dimensions of the first end of the reference electrode are... .

9. The three-electrode coin cell according to claim 2, characterized in that, The first end of the reference electrode is located within the area of ​​the positive electrode sheet, and the portion of the reference electrode near the second end is folded to form a second protrusion structure of a second height; One end of the negative electrode shell is embedded between the first protruding structure and the second protruding structure.

10. A battery pack, characterized in that, This includes the three-electrode coin cell as described in any one of claims 1-9.

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