A curved battery and an electric device

Abstract

The present disclosure relates to a curved battery and an electrical device, wherein the curved battery comprises a positive electrode sheet, the positive electrode sheet comprises a current collector and a dressing layer disposed on at least one surface of the current collector, the content of the positive electrode binder in the dressing layer is P, in weight %, the curvature radius of the curved battery is R, in mm, wherein 1.6≤R / P≤110. The curved battery disclosed in the present disclosure has high volume energy density, good cycle performance, and low impedance growth rate of the battery, which is conducive to reducing battery capacity loss.

Description

Technical Field

[0001] The present disclosure relates to the technical field of flexible batteries, and in particular, to a curved battery and an electrical device. Background Art

[0002] Flexible curved batteries are mainly used in wearable devices, and there is little research on flexible curved batteries for other electrical devices. In addition, existing flexible curved batteries have the problem of too fast impedance growth during battery cycling, resulting in capacity loss. Summary of the invention

[0003] The purpose of the present disclosure is to provide a curved battery and an electrical device, which can solve the problem that the impedance of existing flexible batteries increases too fast and causes capacity loss during the cycle process.

[0004] In order to achieve the above-mentioned objectives, the first aspect of the present disclosure provides a curved battery, which includes a positive electrode plate, wherein the positive electrode plate includes a current collector and a dressing layer arranged on at least one surface of the current collector, the content of the positive electrode binder in the dressing layer is P, and the unit is weight %, and the curvature radius of the curved battery is R, and the unit is mm, wherein 1.6≤R / P≤110.

[0005] Optionally, in the curved battery, 6≤R / P≤57.

[0006] Optionally, P is 2-16 wt %, and R is 27-65 mm.

[0007] Optionally, the dressing layer is provided on both surfaces of the current collector.

[0008] Optionally, the thickness of the current collector is D1, in μm, and the surface density of the positive electrode sheet is L, in g / m 2 , where 0.01≤D1 / L≤0.5.

[0009] Optionally, 0.017≤D1 / L≤0.35.

[0010] Optionally, D1 is 10-20um, L is 80-600g / m 2 .

[0011] Optionally, the dressing layer includes the positive electrode binder, the positive electrode active material and the positive electrode conductor;

[0012] Based on the total weight of the dressing layer, the content of the positive electrode binder is 2-16% by weight, the content of the positive electrode active material is 80-97% by weight, and the content of the positive electrode conductor is 1-5% by weight.

[0013] Optionally, the positive electrode active material is selected from one or more of lithium iron phosphate, lithium cobalt oxide, lithium manganese oxide and nickel cobalt manganese oxide;

[0014] The positive electrode conductive agent is selected from one or more of carbon nanotubes, graphene, carbon black and carbon fibers;

[0015] The positive electrode binder is selected from one or both of PVDF and PTFE.

[0016] A second aspect of the present disclosure provides an electrical device, which includes the curved battery described in the first aspect of the present disclosure.

[0017] Through the above technical scheme, the present disclosure provides a curved battery and electrical equipment. The curved battery has good electrical properties, high volume energy density, good cycle performance, and low impedance growth rate, which is beneficial to reducing battery capacity loss.

[0018] Other features and advantages of the present disclosure will be described in detail in the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The accompanying drawings are used to provide a further understanding of the present disclosure and constitute a part of the specification. Together with the following specific embodiments, they are used to explain the present disclosure but do not constitute a limitation of the present disclosure. In the accompanying drawings:

[0020] Figure 1 This is a schematic structural diagram of a curved battery provided in the present disclosure, wherein R represents the radius of curvature of the curved battery, and D2 represents the thickness of the curved battery. DETAILED DESCRIPTION

[0021] The specific embodiments of the present disclosure are described in detail below. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present disclosure, and are not used to limit the present disclosure.

[0022] The inventors of the present disclosure have discovered through experimental research that the proportional relationship R / P between the binder content P in the dressing layer of the flexible curved battery and the curvature radius R of the curved battery plays an important role in controlling the cycle impedance of the flexible curved battery.

[0023] A first aspect of the present disclosure provides a curved battery, comprising a positive electrode plate, wherein the positive electrode plate comprises a current collector and a dressing layer disposed on at least one surface of the current collector, wherein the content of the positive electrode binder in the dressing layer is P, expressed in weight %, and the curvature radius of the curved battery is R, expressed in mm, wherein 1.6≤R / P≤110.

[0024] The present disclosure provides a curved battery, which has good electrical properties, high volume energy density, good cycle performance, and low impedance growth rate of the battery, which is beneficial to reducing battery capacity loss. Wherein "1.6≤R / P≤110" includes but is not limited to R / P values ​​of 1.6, 2, 3, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100, 105, 110. In the present disclosure, the curvature radius of the curved battery refers to the curvature radius of the battery with a shell, and the shell of the curved battery is a soft shell conventionally used in the art, such as an aluminum-plastic film.

[0025] In a preferred embodiment, 6≤R / P≤57, including but not limited to 6, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 57. When the ratio of the binder content P in the curved battery to the battery curvature radius R is within the preferred range provided in this embodiment, the battery has a lower impedance growth rate.

[0026] In a specific embodiment, P is 2-16 wt%, and R is 27-65 mm, wherein "2-16 wt%" includes but is not limited to 2 wt%, 3 wt%, 4 wt%, 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, 10 wt%, 11 wt%, 12 wt%, 13 wt%, 14 wt%, 15 wt%, and 16 wt%; "27-65 mm" includes but is not limited to 27 mm, 30 mm, 32 mm, 34 mm, 36 mm, 38 mm, 40 mm, 42 mm, 44 mm, 46 mm, 48 mm, 50 mm, 52 mm, 54 mm, 56 mm, 57 mm, 60 mm, and 65 mm; preferably, P is 2-8 wt%, and R is 27-57 mm. The values ​​of P and R of the curved battery provided by the present disclosure are within the range provided in the present embodiment, especially within the preferred range, which can ensure that the curved battery has better electrochemical performance.

[0027] In a specific embodiment, the dressing layer is provided on both surfaces of the current collector. The positive electrode sheet provided in the present disclosure is provided with a dressing layer on both sides of the current collector to further improve the performance of the battery.

[0028] In one embodiment, the thickness of the current collector is D1, in μm, and the surface density of the positive electrode sheet is L, in g / m 2, wherein 0.01≤D1 / L≤0.5, preferably 0.017≤D1 / L≤0.35. The inventors of the present disclosure have found that the proportional relationship between the thickness D1 of the current collector and the density L of the positive electrode sheet in the flexible curved battery will also affect the performance of the battery. When the value of D1 / L of the battery is within the range of the present embodiment, especially within the preferred range, an excellent effect of reducing the impedance growth rate can be achieved. Wherein "0.01≤D1 / L≤0.5" includes but is not limited to the values ​​of D1 / L of 0.01, 0.017, 0.05, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5. In the present disclosure, "surface density of the positive electrode sheet" refers to the total mass of the dressing layer present on the two surfaces of the current collector per unit area of ​​the current collector when a dressing layer is provided on both surfaces of the current collector of the positive electrode sheet.

[0029] In a specific embodiment, D1 is 10-20um, L is 80-600g / m 2 ; "10-20um" includes but is not limited to 10um, 12um, 14um, 16um, 18um, 20um; "80-600g / m 2 "Including but not limited to 80g / m 2 , 100g / m 2 , 150g / m 2 , 200g / m 2 , 250g / m 2 , 300g / m 2 , 350g / m 2 , 400g / m 2 , 450g / m 2 , 500g / m 2 , 550g / m 2 , 600g / m 2 ; Preferably, D1 is 10-15um, L is 400-600g / m 2 Thick current collectors and high surface density are conducive to achieving a low cycle impedance growth rate, but thick current collectors will also reduce capacity. The inventors of the present disclosure have found that when D1 and L of the positive electrode sheet are within the scope of this embodiment, especially within the preferred range, the positive electrode sheet is more conducive to reducing the impedance growth rate of the battery in the battery.

[0030] In a preferred embodiment, the dressing layer includes the positive electrode binder, the positive electrode active material and the positive electrode conductor; based on the total weight of the dressing layer, the content of the positive electrode binder is 2-16% by weight, the content of the positive electrode active material is 80-97% by weight, and the content of the positive electrode conductor is 1-5% by weight; preferably, the content of the positive electrode binder is 2-8% by weight, the content of the positive electrode active material is 90-97% by weight, and the content of the positive electrode conductor is 1-2% by weight. The content of the components of the dressing layer is within the scope of this embodiment, which can ensure the electrochemical performance of the positive electrode sheet in battery applications.

[0031] In a specific embodiment, the positive electrode active material is selected from one or more of lithium iron phosphate, lithium cobalt oxide, lithium manganese oxide and nickel cobalt manganese oxide;

[0032] The positive electrode conductive agent is selected from one or more of carbon nanotubes, graphene, carbon black and carbon fibers;

[0033] The positive electrode binder is selected from one or both of polyvinylidene fluoride (PVDF) and polytetrafluoroethylene (PTFE).

[0034] The material of the current collector of the positive electrode plate is selected from one or more of aluminum foil, carbon-coated aluminum foil and carbon composite substrate. The materials used in the present disclosure can be obtained through ordinary commercial purchase or prepared by known methods. The positive electrode binder in the dressing layer of the positive electrode plate provided in the present disclosure is an oil-based gel ingredient. The water-based gel has poor fixation on the bending of the battery, which will cause the battery to rebound and fail to reach the predetermined curvature. The oil-based ingredient is more suitable for the flexible curved battery disclosed in the present disclosure.

[0035] In the present disclosure, the curved battery further includes a negative electrode sheet, a separator and an electrolyte.

[0036] In a specific embodiment, the negative electrode plate includes a negative electrode active material, a negative electrode binder, a negative electrode conductive agent and water; wherein the negative electrode active material is selected from one or more of artificial graphite, natural graphite, silicon-based graphite and graphite oxide; the negative electrode binder is an aqueous binder, preferably one or two selected from sodium carboxymethyl cellulose (CMC) and acrylonitrile multipolymer styrene-butadiene rubber (SBR); the negative electrode conductive agent is selected from one or more of carbon black, carbon nanotubes, graphene and carbon fiber.

[0037] In a specific embodiment, the electrolyte is a type of electrolyte commonly used in the art, such as LiPF6 as the electrolyte salt, ethylene carbonate (EC), dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC) as the solvent; in the present disclosure, the separator can be made of conventional materials in the art. The content of the components in the electrolyte can be within the conventional content range in the art.

[0038] The flexible curved battery disclosed in the present invention can be prepared by conventional methods in the art.

[0039] In a specific embodiment, the curved battery is prepared by a method comprising the following steps:

[0040] The positive electrode active material, the positive electrode conductive agent, the positive electrode binder and the positive electrode solvent are mixed to obtain a positive electrode slurry, which is then coated on an aluminum foil current collector to obtain a positive electrode sheet; the positive electrode solvent may be selected from one or more of N-methylpyrrolidone, deionized water, acetone and dimethylacetamide (DMAC);

[0041] The negative electrode active material, the negative electrode binder, the negative electrode conductive agent and the deionized water are mixed to obtain a negative electrode slurry, which is then coated on a copper foil current collector. Preferably, the weight ratio of the negative electrode sheet to the positive electrode sheet is 0.4-0.5:1, preferably 0.42-0.46:1; optionally, the thickness of the current collector of the negative electrode sheet is 6-10 μm;

[0042] The positive electrode sheet, the negative electrode sheet, the separator and the electrolyte are assembled to obtain a battery, and a non-standard hot pressing mold is used to produce a curved positive electrode sheet.

[0043] In the present disclosure, the flexible bendable battery can be prepared into various shapes through a hot pressing process, including but not limited to round, C-shaped, L-shaped pole pieces and other special-shaped pole pieces, to make soft-pack batteries and aluminum shell batteries of different shapes.

[0044] A second aspect of the present disclosure provides an electrical device, which includes the battery described in the first aspect of the present disclosure.

[0045] In the present disclosure, electrical devices may include but are not limited to 3C batteries, drones, Bluetooth headsets, VR glasses, etc.

[0046] The present disclosure is further described in detail by way of examples. The raw materials used in the examples can all be obtained through commercial sources.

[0047] In the following embodiments and comparative examples, the electrolyte of the battery has the following composition: the solvent is EC / DMC / EMC, the electrolyte salt is LiPF6, and an additive (the additive is vinylene carbonate, VC) is added. Based on the total weight of the electrolyte, the content of LiPF6 is 12.93% by weight, the content of the additive is 2.5% by weight, and the rest are solvents EC, DMC and EMC, and the contents of the three solvents are the same.

[0048] In the following examples and comparative examples, the negative electrode slurry of the battery has the following composition: artificial graphite is used as the negative electrode active material, CMC and SBR are used as negative electrode binders, carbon black is used as the negative electrode conductive agent, deionized water is used as the solvent, and based on the total weight of the negative electrode slurry, the content of artificial graphite is 43.27% by weight, the content of CMC is 0.86% by weight, the content of SBR is 0.42% by weight, the content of carbon black is 0.42% by weight, and the balance is water.

[0049] Example 1

[0050] (1) Preparation of positive electrode sheet: The positive electrode active material is lithium iron phosphate, the positive electrode conductive agent is carbon nanotubes, the positive electrode binder is polyvinylidene fluoride (PVDF), and the positive electrode solvent is NMP. After stirring evenly, the positive electrode slurry is obtained, which is coated on the aluminum foil current collector (double-sided coating), and then dried to remove the solvent; the thickness of the aluminum foil current collector (D1) is 10um, and the surface density of the double-sided coating layer of the positive electrode sheet (i.e., the surface density L of the positive electrode sheet) is 80g / m 2 , the content of the positive electrode binder in the dressing layer (P) is 2% by weight, the content of the positive electrode active material is 97% by weight, the content of the positive electrode conductive agent is 1% by weight, the total amount of the positive electrode binder, the positive electrode active material and the positive electrode conductive agent (recorded as the positive electrode dressing content) accounts for 40% by weight of the positive electrode slurry, and the content of the solvent in the positive electrode slurry is 60% by weight;

[0051] (2) Negative electrode sheet preparation: artificial graphite is used as the negative electrode active material, CMC and SBR are used as the negative electrode binder, carbon black is used as the negative electrode conductive agent, and deionized water is used as the negative electrode solvent. After being mixed evenly, a negative electrode slurry is obtained, which is coated on an 8um copper foil current collector and then dried to remove the solvent; the NP ratio of the negative electrode coating amount to the positive electrode coating amount is 1.15;

[0052] (3) Production of curved batteries: The positive and negative electrodes are die-cut into rectangular shapes, and the positive and negative electrodes are alternately stacked. The separator is folded in a Z shape and heat-sealed in a shell made of an aluminum-plastic film. The positive electrode multi-layer aluminum foil and the negative electrode multi-layer copper foil of the battery cell are transferred by foils. The electrolyte uses EC / DMC / EMC+LiPF6+additives. The separator uses a 15umPE ceramic coated ion exchange membrane. A non-standard hot pressing mold is used to produce the curved battery. The curvature radius of the curved battery is R=27mm.

[0053] Example 2-19

[0054] Referring to the preparation method of Example 1, the difference from Example 1 is that the battery is prepared according to the contents of the positive electrode binder, the positive electrode active material and the positive electrode conductive agent in Table 1 below. The rest of the process is the same as Example 1.

[0055] Comparative Example 1-2

[0056] Referring to the preparation method of Example 1, the difference from Example 1 is that the battery is prepared according to the contents of the positive electrode binder, the positive electrode active material and the positive electrode conductive agent in Table 1 below. The rest of the process is the same as Example 1.

[0057] Test Case

[0058] This test example is used to test the impedance growth rate of the battery obtained in the above embodiment. The test method includes: 0.1C charge and discharge formation, 1C discharge capacity division; after the capacity division is completed, 45°C, 1C cycle 500 times, test DCIR1 before the cycle, DCIR2 after the cycle, and calculate the impedance growth rate T (%) by the following formula (1): T = [DCIR2-DCIR1) / DCIR1] × 100% formula (1).

[0059] The DCIR before the cycle (DCIR1) and the DCIR after the cycle (DCIR2) are obtained by the following method: at 50% SOC, 1C discharge for 30s, the battery's equilibrium voltage V1, and the voltage after 30s V2, the DCIR is calculated by the following formula (2): DCIR = (V2-V1) / I Formula (2).

[0060] The compositions of the positive electrode slurries and the positive electrode sheet coating layers in the above embodiments and comparative examples are listed in Table 1 below.

[0061] Table 1

[0062]

[0063] The positive electrode binder content (P) of the flexible curved battery prepared in the above embodiment, the curvature radius (R) of the curved battery, the thickness of the current collector in the positive electrode sheet (D1), and the surface density (L) of the positive electrode sheet are listed in the following Table 2; the impedance growth rate and 500-cycle capacity retention rate obtained from the electrochemical performance test of the curved battery are listed in the following Table 2.

[0064] Table 2

[0065]

[0066] According to the data in Table 2 above, we can see that:

[0067] Comparing Examples 1-24 with Comparative Examples 1-2, the R / P value of the curved battery obtained in Examples 1-24 is within the range provided in the present disclosure (1.6≤R / P≤110), while the R / P value of the curved battery obtained in Comparative Examples 1-2 is not within the range, and the curved battery obtained in Examples 1-24 has a lower impedance growth rate and a higher cycle capacity retention rate;

[0068] Comparing Examples 13-15, 20, and 23 with Examples 1 and 21-22, it can be seen that, when D1 / L is the same, the R / P values ​​of the batteries in Examples 1 and 21-22 are within the preferred range provided in the present disclosure (6≤R / P≤57), the R / P values ​​of the batteries in Examples 13-15, 20, and 23 are not within the above preferred range, and the impedance growth rate of the batteries in Examples 1 and 21-22 is less than the impedance growth rate of the batteries in Examples 13-15, 20, and 23; further, in Examples 13-15, 2 In Examples 0 and 23, the values ​​of P and R of the curved batteries in Examples 20 and 23 are not within the optimized range provided in the present disclosure, and the impedance growth rate of the batteries in Examples 13-15 is lower than that of the impedance growth rate in Examples 20 and 23; in Examples 1, 21-22, the values ​​of P and R of the curved batteries in Examples 1 and 21 are within the optimized range provided in the present disclosure, the values ​​of P and R of the curved battery in Example 22 are not within the optimized range provided in the present disclosure, and the impedance growth rate of the batteries in Examples 1 and 21 is lower than that of the curved battery in Example 22;

[0069] Comparing Example 13 with Example 17, it can be seen that, under the same R / P condition, the value of D1 / L of the battery in Example 13 is within the preferred range provided in the present disclosure (0.017≤D1 / L≤0.35), the value of D1 / L of the battery in Example 17 is not within the preferred range, and the impedance growth rate of the curved battery in Example 13 is lower than the impedance growth rate of the battery in Example 17; in addition, D1 and L of the curved battery in Example 13 are both within the optimized range provided in the present disclosure, D1 in Example 17 is not within the optimized range provided in the present disclosure, and the impedance growth rate of the curved battery in Example 13 is lower;

[0070] In addition, considering the R / P value and D1 / L value of the curved battery comprehensively, the R / P and D1 / L of the curved batteries in Examples 17-19 are not within the preferred range provided in the present disclosure, the D1 / L of the curved batteries in Examples 13-16, 20 and 23 are within the preferred range, but the R / P is not within the preferred range, and the impedance growth rate of the curved batteries in Examples 13-16, 20 and 23 is lower than that in Examples 17-19. It can be seen that when the R / P of the curved battery is within the preferred range, the impedance growth rate of the curved battery is lower; further, the R / P and D1 / L of the curved batteries in Examples 1-12, 21-22 and 24 are both within the preferred range provided in the present disclosure. Compared with Examples 13-16, 20 and 23, when the R / P and D1 / L of the curved batteries are both within the preferred range provided in the present disclosure, the curved batteries in Examples 1-12, 21-22 and 24 have a lower impedance growth rate.

[0071] And comparing Example 16 with Example 14, under the condition that the R / P of the curved battery is similar, D1 and L of the curved battery in Example 14 are both within the optimized range provided by the present disclosure, D1 in Example 16 is not within the optimized range provided by the present disclosure, and the impedance growth rate of the curved battery in Example 14 is lower.

[0072] The preferred embodiments of the present disclosure are described in detail above; however, the present disclosure is not limited to the specific details in the above embodiments. Within the technical concept of the present disclosure, a variety of simple modifications can be made to the technical solution of the present disclosure, and these simple modifications all fall within the protection scope of the present disclosure.

[0073] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present disclosure will not further describe various possible combinations.

[0074] In addition, various embodiments of the present disclosure may be arbitrarily combined, and as long as they do not violate the concept of the present disclosure, they should also be regarded as the contents disclosed by the present disclosure.

Claims

1. A curved battery, characterized in that: The curved battery comprises a positive electrode sheet, wherein the positive electrode sheet comprises a current collector and a dressing layer disposed on at least one surface of the current collector, wherein the content of the positive electrode binder in the dressing layer is P, in weight %, and the curvature radius of the curved battery is R, in mm, wherein 6≤R / P≤57; wherein P is 2-16 weight %, and R is 27-37 mm; The dressing layer is provided on both surfaces of the current collector; the thickness of the current collector is D1, in μm, and the surface density of the positive electrode sheet is L, in g / m 2 , where 0.1≤D1 / L≤0.25; where D1 is 10-20μm.

2. The curved battery according to claim 1, characterized in that: L: 80-600g / m 2 .

3. The curved battery according to claim 1, characterized in that: The dressing layer includes the positive electrode binder, the positive electrode active material and the positive electrode conductor; Based on the total weight of the dressing layer, the content of the positive electrode binder is 2-16% by weight, the content of the positive electrode active material is 80-97% by weight, and the content of the positive electrode conductor is 1-5% by weight.

4. The curved battery according to claim 3, characterized in that: The positive electrode active material is selected from one or more of lithium iron phosphate, lithium cobalt oxide, lithium manganese oxide and nickel cobalt lithium manganese oxide; The positive electrode conductive agent is selected from one or more of carbon nanotubes, graphene, carbon black and carbon fibers; The positive electrode binder is selected from one or both of PVDF and PTFE.

5. An electrical device, characterized in that: A curved battery comprising the curved battery described in any one of claims 1 to 4.

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