Electrochemical device and electronic device

Abstract

The application discloses an electrochemical device and an electronic device. The electrochemical device comprises a first shell, a second shell, a separator, a first electrode assembly and a second electrode assembly. The separator is located between the first shell and the second shell to define a first cavity and a second cavity on two sides of the separator respectively. The first electrode assembly is arranged in the first cavity, and the second electrode assembly is arranged in the second cavity. The Li ion permeability K1 of the separator satisfies K1≤1.0 μg / (cm 2 ·h). The electrochemical device of the application can have excellent durability.

Description

Technical Field

[0001] This application relates to the field of electrochemistry, and in particular to an electrochemical device and an electronic device. Background Technology

[0002] Currently, batteries are widely used in electronic products such as drones, mobile phones, tablets, and laptops. In some applications, a single battery cell cannot achieve the desired output power; therefore, multiple battery cells are typically connected in series, parallel, or a combination thereof to work together to achieve the desired power output. However, while connecting multiple battery cells in series, parallel, or a combination thereof can increase output power, the energy density of the entire battery pack is relatively low. Therefore, the design of a series-connected battery in a single pouch has been proposed. This design includes a housing and multiple electrode assemblies housed within the same housing. These electrode assemblies are connected in series outside the housing and separated from each other by spacers. Summary of the Invention

[0003] However, the inventors of this application discovered through research that the durability of batteries connected in series in the same bag is insufficient and needs further improvement.

[0004] In view of the above problems, this application provides an electrochemical device and an electronic device to improve the durability of batteries connected in series in the same bag.

[0005] To address the aforementioned technical problems, this application provides an electrochemical device comprising a first housing, a second housing, a separator, a first electrode assembly, and a second electrode assembly. The separator is located between the first and second housings, defining a first cavity and a second cavity on either side of the separator. The first electrode assembly is disposed in the first cavity, and the second electrode assembly is disposed in the second cavity. The Li ion permeability K1 of the separator satisfies K1≤1.0μg / (cm²) 2The Li ion permeability K1 of the isolator is tested by the following method: A first test shell and a second test shell are respectively clamped on opposite sides of the isolator as a receiving body. The receiving body is placed with the isolator perpendicular to the horizontal plane. A first test cavity is defined between the isolator and the first test shell, and a second test cavity is defined between the isolator and the second test shell. Dimethyl carbonate is injected into the first test cavity, and a test solution composed of lithium hexafluorophosphate and diethyl carbonate is injected into the second test cavity. Based on the mass of the test solution, the mass percentage of lithium hexafluorophosphate in the test solution is 12.5%. The volumes of dimethyl carbonate and the test solution are equal, and the liquid surface of dimethyl carbonate in the first test cavity is flush with the liquid surface of the test solution in the second test cavity, thereby forming a test body. The isolator includes a first region in contact with dimethyl carbonate and a second region in contact with the test solution. Along the thickness direction of the isolator, the overlapping area of ​​the first region and the second region is S cm. 2 The test specimen was left to stand at 60℃ for 24 hours. Inductively coupled plasma (ICP-PAP) was used to measure the Li ion content in the first test chamber, which was found to be m1 μg. The Li ion permeability of the isolator was K1 = m1 / (S×24) μg / (cm³). 2 ·h). Due to the difficulty of heat dissipation between the electrode components inside the electrochemical device, the isolator is often under high-temperature conditions. The Li ion permeability K1 of the isolator at 60℃ satisfies K1≤1.0μg / (cm³). 2 ·h) can improve the isolation of the insulating element against Li ions at high temperatures, inhibit the decomposition of the electrolyte and the deposition of the negative electrode metal, thereby improving the durability of the electrochemical device.

[0006] In some embodiments, the separator includes a substrate layer, the substrate layer includes a metal layer, and the electrochemical device satisfies at least one of the following conditions (1) to (2): (1) the pinhole density of the metal layer is ≤3 pins / cm². 2 (2) The maximum pore size of the pinholes in the metal layer is ≤10μm. The above scheme can further reduce the Li ion permeability of the substrate layer.

[0007] In some embodiments, the separator includes a substrate layer, the substrate layer including a first polymer layer, and the electrochemical device satisfies at least one of the following conditions (a) to (b): (a) the crystallinity of the first polymer layer is ≥50%; (b) the melting point of the first polymer layer is ≥170°C. In the above embodiments, the Li ion permeability of the substrate layer can be further reduced.

[0008] In some embodiments, the separator further includes an encapsulation layer located on the surface of the substrate layer.

[0009] In some embodiments, the material of the metal layer includes at least one of Ni, Ti, Cu, Ag, Au, Pt, Fe, Sn, Co, Cr, W, Mo, Al, Mg, K, Na, Ca, Sr, Ba, Ge, Sb, Pb, In, Zn, or stainless steel.

[0010] In some embodiments, the material of the first polymer layer includes at least one of polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polyetheretherketone, polyimide, polyamide, polyethylene glycol, polyamide-imide, polycarbonate, cyclic polyolefin, polyphenylene sulfide, polyvinyl acetate, polytetrafluoroethylene, polymethylene naphthalene, polyvinylidene fluoride, polypropylene carbonate, poly(vinylidene fluoride-hexafluoropropylene), poly(vinylidene fluoride-co-trifluorochloroethylene), silicone, vinylon, polypropylene, anhydride-modified polypropylene, polyethylene, ethylene-propylene copolymer, polyvinyl chloride, polystyrene, polyether nitrile, polyurethane, polyphenylene ether, polyester, polysulfone, amorphous α-olefin copolymer, or derivatives thereof.

[0011] In some embodiments, the encapsulation layer is made of at least one of polypropylene, modified polypropylene, polyethylene, ethylene-propylene copolymer, ethylene-vinyl acetate copolymer, or ethylene-ethyl acrylate copolymer.

[0012] In some embodiments, the electrochemical device satisfies at least one of the following conditions (c) to (d): (c) a first electrolyte is provided in a first cavity, and the separator includes a first surface in contact with the first electrolyte, wherein a first contact angle of the first electrolyte on the first surface is ≤90°. (d) a second electrolyte is provided in a second cavity, and the separator includes a second surface in contact with the second electrolyte, wherein a second contact angle of the second electrolyte on the second surface is ≤90°. In the above scheme, the contact angle between the first surface (and / or the second surface) of the separator and the first electrolyte (and / or the second electrolyte) is small, so that after the first electrolyte (and / or the second electrolyte) comes into contact with the first surface (and / or the second surface) of the separator, it can extend a larger area on the first surface (and / or the second surface) of the separator, thereby enhancing the heat exchange between the separator and the first electrolyte (and / or the second electrolyte). This facilitates the transfer of heat inside the electrochemical device to the surrounding sidewalls through the separator and conduction to the outside of the electrochemical device, thereby reducing the internal temperature of the electrochemical device and suppressing the decrease in the ion isolation of the separator at high temperatures, thus improving the durability of the electrochemical device.

[0013] In some embodiments, the first contact angle is ≤50°; and / or, the second contact angle is ≤50°. The above solutions can further improve the heat dissipation effect of the isolator, reduce the internal temperature of the electrochemical device, thereby suppressing the decrease in the ion barrier properties of the isolator at high temperatures and improving the durability of the electrochemical device.

[0014] In some embodiments, the thermal conductivity of the first electrolyte is ≥0.1 W / (m·K); and / or, the thermal conductivity of the second electrolyte is ≥0.1 W / (m·K). The above solutions can further improve the heat dissipation effect of the electrochemical device, reduce the operating temperature of the isolator, suppress the decrease in the ion barrier properties of the isolator at high temperatures, and thus improve the durability of the electrochemical device.

[0015] In some embodiments, the first electrode assembly and the second electrode assembly are connected in series. This approach can increase the overall voltage of the electrochemical device, reduce the operating current, thereby reducing the temperature rise during operation, lowering the operating temperature of the isolator, and improving the durability of the electrochemical device.

[0016] This application also provides an electronic device, including any of the above-mentioned electrochemical devices.

[0017] The electrochemical device provided in this application fully considers the working environment of the separator in a series-connected battery bag, by limiting the Li ion permeability K1 of the separator at a high temperature of 60°C to ≤1.0 μg / (cm). 2 ·h) can improve the isolation of the separator against Li ions at high temperatures, thereby inhibiting the decomposition of the electrolyte and the deposition of negative electrode metal, and thus improving the durability of batteries connected in series in the same bag. Attached Figure Description

[0018] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments of this application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application.

[0019] Figure 1 This is an exploded schematic diagram of the electrochemical device provided in the first embodiment of this application; wherein the electrochemical device includes two electrode assemblies and a separator;

[0020] Figure 2 This is a side view schematic diagram of the electrochemical device provided in the first embodiment of this application;

[0021] Figure 3 This is a cross-sectional schematic diagram of the electrochemical device provided in the first embodiment of this application.

[0022] Figure 4 This is an exploded schematic diagram of the electrochemical device provided in the second embodiment of this application; wherein the electrochemical device includes three electrode assemblies and two insulating components;

[0023] Figure 5 This is a side view schematic diagram of the isolation member provided in the first embodiment of this application;

[0024] Figure 6This is a cross-sectional schematic diagram of a Li ion permeability test body for an isolation element provided in one embodiment of this application;

[0025] Figure 7 This is a schematic diagram of the contact angle of the first electrolyte on the separator according to one embodiment of this application. Detailed Implementation

[0026] To facilitate understanding of this application, a more detailed description is provided below with reference to the accompanying drawings and specific embodiments. It should be noted that when an element is described as being "fixed to" another element, it can be directly on the other element, or one or more intermediate elements may exist between them. When an element is described as being "connected" to another element, it can be directly connected to the other element, or one or more intermediate elements may exist between them. The terms "vertical," "horizontal," "left," "right," and similar expressions used in this specification are for illustrative purposes only.

[0027] Unless otherwise defined, all technical and scientific terms used in this specification have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the scope of this application. The term "and / or" as used in this specification includes any and all combinations of one or more of the associated listed items.

[0028] The series-connected battery includes a casing and multiple electrode assemblies disposed within the same casing. The multiple electrode assemblies are connected in series outside the casing and separated from each other by a spacer. However, the inventors of this application have discovered through research that heat dissipation between the electrode assemblies inside the series-connected battery is difficult, and the spacers are often under high-temperature conditions, resulting in insufficient durability of the series-connected battery.

[0029] In view of this, see Figure 1-7 This embodiment provides an electrochemical device that exhibits good durability. The electrochemical device can be a battery 10, and more specifically, a lithium-ion battery 10 having multiple electrode components. See also... Figure 1-2The lithium-ion battery 10 includes a first housing 200, a second housing 300, a separator 100, a first electrode assembly 400, and a second electrode assembly 500. The separator 100 is located between the first housing 200 and the second housing 300, defining a first cavity 210 and a second cavity 310 on both sides of the separator 100. The first electrode assembly 400 is disposed in the first cavity 210, and the second electrode assembly 500 is disposed in the second cavity 310. Electrolytes are disposed in both the first cavity 210 and the second cavity 310. The separator 100 serves to block the flow of electrolyte between the first cavity 210 and the second cavity 310, and also to suppress ion transport between the electrolyte in the first cavity 210 and the electrolyte in the second cavity 310.

[0030] The first electrode assembly 400 and the electrolyte in the first cavity 210 form an independent electrochemical structure, and the second electrode assembly 500 and the electrolyte in the second cavity 310 form an independent electrochemical structure. The first electrode assembly 400 and the second electrode assembly 500 may or may not be electrically connected. When the first electrode assembly 400 and the second electrode assembly 500 are electrically connected, they may be connected in series or in parallel. In one embodiment, the first electrode assembly 400 and the second electrode assembly 500 are connected in series to increase the overall voltage of the battery 10, reduce the operating current of the battery 10, thereby reducing the temperature rise of the battery 10 during operation, reducing the operating temperature of the separator 100, suppressing ion transport between the electrolyte in the first cavity 210 and the electrolyte in the second cavity 310, and thus improving the durability of the battery 10.

[0031] See Figure 1-3 The battery 10 in this application may have two electrode assemblies (i.e., a first electrode assembly 400 and a second electrode assembly 500) and a separator 100. The separator 100 divides the internal spaces of the first housing 200 and the second housing 300 into two independent cavities (i.e., a first cavity 210 and a second cavity 310). See also Figure 3 The battery 10 may also have multiple separators 100 and electrode assemblies corresponding to the number of separators 100 (the number of electrode assemblies is one more than the number of separators 100). For ease of description, the following description uses the battery 10 having one separator 100 and two electrode assemblies as an example.

[0032] Specifically, considering the difficulty of heat dissipation between the electrode components inside the battery 10 and the fact that the separator 100 is often under high-temperature conditions, in this application, the Li ion permeability K1 of the separator 100 satisfies K1≤1.0μg / (cm³) 2 •h). For example, K1 can be 0.9 μg / (cm³). 2 ·h), 0.8μg / (cm)2 ·h), 0.7μg / (cm) 2 ·h), 0.6μg / (cm) 2 ·h) or 0.5μg / (cm 2 •h) etc. See also Figure 6 The Li ion permeability K1 of the isolator 100 is tested by the following method: A first test housing 600 and a second test housing 700 are respectively sandwiched on opposite sides of the isolator 100 as a receiving body. The receiving body is placed with the isolator 100 perpendicular to the horizontal plane, defining a first test cavity 800 between the isolator 100 and the first test housing 600, and a second test cavity 900 between the isolator 100 and the second test housing 700. Dimethyl carbonate is injected into the first test cavity 800, and a test solution composed of lithium hexafluorophosphate and diethyl carbonate is injected into the second test cavity 900. Based on the mass of the test solution, the mass percentage of lithium hexafluorophosphate in the test solution is 12.5%. The volumes of dimethyl carbonate and the test solution are equal, and the liquid surface of dimethyl carbonate in the first test chamber 800 is flush with the liquid surface of the test solution in the second test chamber 900, thus forming a test body. The area of ​​the first region where the isolator 100 contacts the dimethyl carbonate in the first test chamber 800 is equal to the area of ​​the second region where the isolator 100 contacts the test solution in the second test chamber 900, both being S cm. 2 Furthermore, the first and second regions coincide in the thickness direction of the separator 100. The test specimen was left to stand at 60°C for 24 hours, and the Li ion content in the first test chamber 800 was measured to be m1 μg using inductively coupled plasma (ICP-PAP). The Li ion permeability of the separator 100, K1, is given by K1 = m1 / (S×24) μg / (cm²). 2 •h). For example, when Scm 2 10cm 2 When m1μg is 190μg, K1=190 / (10×24)μg / (cm 2 ·h), yielding K1 to be approximately 0.791 μg / (cm). 2 ·h).

[0033] The inventors of this application, after considering the effect of battery temperature on the ion barrier properties of separator 100, found that when the Li ion permeability K1 of separator 100 at 60°C is ≤1.0 μg / (cm³), 2 When ·h), the isolation of the separator 100 against Li ions at high temperatures can be improved, the decomposition of the electrolyte and the deposition of the negative electrode metal can be suppressed, thereby improving the durability of the battery 10.

[0034] The material and specific structure of the separator 100 depend on the specific requirements, but the separator 100 must at least meet the above-mentioned Li ion permeability K1 ≤ 1.0 μg / (cm³). 2 The parameter requirements for ·h) are sufficient. For details, see [link to documentation]. Figure 5 In one embodiment, the spacer 100 includes a substrate layer 110 and two encapsulation layers (a first encapsulation layer 120 and a second encapsulation layer 130, respectively), with the two encapsulation layers respectively attached to the two side walls of the substrate layer 110. In other embodiments, the spacer 100 may have other layers, which will not be described in detail here. For ease of description, the following example illustrates the structure of the spacer 100, which includes only the substrate layer 110 and the two encapsulation layers.

[0035] The material of the substrate layer 110 depends on specific requirements. In one embodiment, the substrate layer 110 includes a metal layer with a pinhole density of ≤3 pins / cm². 2 This solution can reduce the Li ion permeability of the substrate layer 110. The material of the metal layer may include at least one of Ni, Ti, Cu, Ag, Au, Pt, Fe, Sn, Co, Cr, W, Mo, Al, Mg, K, Na, Ca, Sr, Ba, Ge, Sb, Pb, In, Zn, or stainless steel. When the material of the substrate layer 110 includes a metal layer, in one embodiment, the maximum pore size of the pinholes in the metal layer is ≤10 μm. This solution can further reduce the Li ion permeability of the substrate layer 110.

[0036] In another embodiment, the substrate layer 110 includes a first polymer layer with a crystallinity ≥50%. This approach can reduce the Li ion permeability of the substrate layer 110. The material of the first polymer layer includes at least one of polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polyetheretherketone, polyimide, polyamide, polyethylene glycol, polyamide-imide, polycarbonate, cyclic polyolefin, polyphenylene sulfide, polyvinyl acetate, polytetrafluoroethylene, polymethylene naphthalene, polyvinylidene fluoride, polypropylene carbonate, poly(vinylidene fluoride-hexafluoropropylene), poly(vinylidene fluoride-co-trifluorochloroethylene), silicone, vinylon, polypropylene, anhydride-modified polypropylene, polyethylene, ethylene-propylene copolymer, polyvinyl chloride, polystyrene, polyether nitrile, polyurethane, polyphenylene ether, polyester, polysulfone, amorphous α-olefin copolymer, or derivatives thereof. When the substrate layer 110 is made of a first polymer layer, in one embodiment, the melting point of the first polymer layer is ≥170°C. This design improves the thermal stability of the substrate layer 110.

[0037] In some embodiments, the encapsulation layer is made of at least one of polypropylene, modified polypropylene, polyethylene, ethylene-propylene copolymer, ethylene-vinyl acetate copolymer, or ethylene-ethyl acrylate copolymer. When the spacer 100 has two encapsulation layers, the two encapsulation layers may be made of the same or different materials.

[0038] The applicant has considered that temperature affects the ion barrier properties of the separator 100, and that the higher the operating temperature of the separator 100, the faster the ion permeation rate. Therefore, the durability of the battery 10 can be improved by lowering the operating temperature of the separator 100. In view of this, see [reference needed]. Figure 7 In some embodiments, the electrochemical device satisfies the following conditions: a first electrolyte 20 is provided in the first cavity 210, and the separator 100 includes a first surface in contact with the first electrolyte 20, wherein the first contact angle α of the first electrolyte 20 on the first surface is ≤90°. In this scheme, the contact angle of the first surface of the separator 100 relative to the first electrolyte 20 is small, thereby allowing the first electrolyte 20 to extend a larger area on the first surface of the separator 100 after contact, which enhances the heat exchange between the separator 100 and the first electrolyte 20. This facilitates the transfer of heat inside the battery 10 to the surrounding sidewalls and out of the battery 10 through the separator 100, thereby reducing the internal temperature of the battery 10 and suppressing the decrease in the ion isolation of the separator 100 at high temperatures, thus improving the durability of the battery 10.

[0039] Similarly, in another embodiment, the second cavity 310 is provided with a second electrolyte, and the separator 100 includes a second surface in contact with the second electrolyte, wherein the second contact angle of the second electrolyte on the second surface is ≤90°. In this scheme, the contact angle of the second surface of the separator 100 relative to the second electrolyte is small, so that after the second electrolyte comes into contact with the second surface of the separator 100, it can extend a larger area on the second surface of the separator 100, thereby enhancing the heat exchange between the separator 100 and the second electrolyte. This facilitates the transfer of heat inside the battery 10 to the surrounding sidewalls through the separator 100 and conduction to the outside of the battery 100, thereby reducing the internal temperature of the battery 10 and suppressing the decrease in the ion isolation of the separator 100 at high temperatures, thereby improving the durability of the battery 10.

[0040] The following provides a method for testing the contact angle of electrolyte: The contact angle is the angle θ between the tangent at the gas-liquid interface at the gas-liquid-solid three-phase junction and the liquid-solid-liquid interface. It is a measure of the degree of wetting. A contact angle measuring instrument can be used for measurement. A drop of electrolyte is placed on the surface of the separator 100 material. Under the measuring instrument, the angle θ at which the electrolyte drop spreads on the surface of the separator 100 material is obtained through optical measurement; this is the contact angle of the electrolyte on the surface of the separator 100 material.

[0041] In some embodiments, the first contact angle is ≤50°, and / or the second contact angle is ≤50°. The above solutions can further improve the heat dissipation effect of the separator 100, thereby suppressing the decrease in the ion barrier properties of the separator 100 at high temperatures and improving the durability of the battery 10.

[0042] In some embodiments, the thermal conductivity of the first electrolyte is ≥0.1 W / (m·K); and / or the thermal conductivity of the second electrolyte is ≥0.1 W / (m·K). The above solutions can further improve the heat dissipation effect of the battery 10, reduce the operating temperature of the separator 100, suppress the decrease in the ion barrier properties of the separator 100 at high temperatures, and thereby improve the durability of the battery 10.

[0043] This application also provides an electronic device comprising the electrochemical device provided in this application, the electrochemical device including a lithium-ion battery 10. The electronic device in this application is not particularly limited and can be any electronic device known in the prior art. For example, the electronic device includes, but is not limited to, laptops, pen-based computers, mobile computers, e-book players, portable telephones, portable fax machines, portable copiers, portable printers, stereo headphones, video recorders, LCD TVs, portable cleaners, portable CD players, mini CDs, transceivers, electronic notebooks, calculators, memory cards, portable recorders, radios, backup power supplies, motors, automobiles, motorcycles, electric bicycles, bicycles, lighting fixtures, toys, game consoles, clocks, power tools, flashlights, cameras, household large-capacity batteries 10, and lithium-ion capacitors, etc.

[0044] The electrode assembly used in this application is not particularly limited; any electrode assembly from the prior art can be used, as long as it achieves the purpose of this application. For example, a stacked electrode assembly or a wound electrode assembly can be used. The electrode assembly generally includes a positive electrode, a negative electrode, and a separator.

[0045] The negative electrode sheet in this application is not particularly limited, as long as it achieves the purpose of this application. For example, the negative electrode sheet typically includes a negative electrode current collector and a negative electrode active material layer. The negative electrode current collector is not particularly limited; any negative electrode current collector known in the art can be used, such as copper foil, aluminum foil, aluminum alloy foil, and composite current collectors. The negative electrode active material layer includes a negative electrode active material, and the negative electrode active material is not particularly limited; any negative electrode active material known in the art can be used. For example, it can include at least one of artificial graphite, natural graphite, mesophase carbon microspheres, soft carbon, hard carbon, silicon, silicon-carbon, lithium titanate, etc.

[0046] The positive electrode sheet in this application is not particularly limited, as long as it can achieve the purpose of this application. For example, the positive electrode sheet typically includes a positive current collector and a positive active material. The positive current collector is not particularly limited and can be any positive current collector known in the art, such as aluminum foil, aluminum alloy foil, or composite current collectors. The positive active material is not particularly limited and can be any existing positive active material, including at least one of lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium iron phosphate, lithium cobalt oxide, lithium manganese oxide, or lithium manganese iron phosphate.

[0047] There are no particular limitations on the electrolyte used in this application. Any electrolyte known in the art can be used, such as any of the gel, solid, and liquid states. For example, liquid electrolytes may include lithium salts and non-aqueous solvents.

[0048] There are no particular limitations on the lithium salt; any lithium salt known in the art can be used, as long as it achieves the purpose of this application. For example, the lithium salt may include at least one of lithium hexafluorophosphate (Li PF6), lithium tetrafluoroborate (Li BF4), lithium difluorophosphate (LiPO2F2), lithium bis(trifluoromethanesulfonyl)imide LiN(CF3SO2)2 (Li TFS I), lithium bis(fluorosulfonyl)imide Li(N(SO2F)2)(Li FSI), lithium bis(oxalateborate)borate LiB(C2O4)2 (Li BOB), or lithium difluorooxalateborate LiBF2(C2O4) (Li DFOB). For example, Li PF6 may be selected as the lithium salt.

[0049] The non-aqueous solvent is not particularly limited, as long as it can achieve the purpose of this application. For example, the non-aqueous solvent may include at least one of carbonate compounds, carboxylic acid ester compounds, ether compounds, nitrile compounds, or other organic solvents.

[0050] For example, carbonate compounds may include at least one of diethyl carbonate (DEC), dimethyl carbonate (DMC), methyl ethyl carbonate (EMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), ethylene carbonate (EC), propylene carbonate (PC), or butyl carbonate (BC).

[0051] The diaphragm used in this application is not particularly limited; for example, the diaphragm may include polymers or inorganic materials formed from materials stable to the electrolyte of this application. The diaphragm should generally possess ionic conductivity and electronic insulation.

[0052] For example, the diaphragm may include an intermediate layer and a surface treatment layer. The intermediate layer may be a nonwoven fabric, membrane, or composite membrane with a porous structure, and the material of the intermediate layer may be selected from at least one of polyethylene, polypropylene, polyethylene terephthalate, and polyimide. Optionally, a polypropylene porous membrane, a polyethylene porous membrane, a polypropylene nonwoven fabric, a polyethylene nonwoven fabric, or a polypropylene-polyethylene-polypropylene porous composite membrane may be used. Optionally, a surface treatment layer is provided on at least one surface of the intermediate layer, and the surface treatment layer may be a polymer layer or an inorganic layer, or a layer formed by mixing polymers and inorganic materials.

[0053] For example, the inorganic layer comprises inorganic particles and a binder. The inorganic particles are not particularly limited and may be selected from at least one of alumina, silicon oxide, magnesium oxide, titanium oxide, hafnium dioxide, tin oxide, cerium dioxide, nickel oxide, zinc oxide, calcium oxide, zirconium oxide, yttrium oxide, silicon carbide, boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide, and barium sulfate. The binder is not particularly limited and may be selected from one or a combination of several of polyvinylidene fluoride, a copolymer of polyvinylidene fluoride and hexafluoropropylene, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyvinyl ether, polymethyl methacrylate, polytetrafluoroethylene, and polyhexafluoropropylene. The polymer layer contains a polymer, the polymer material of which includes at least one of polyamide, polyacrylonitrile, acrylate polymer, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyvinyl ether, polyvinylidene fluoride, or poly(vinylidene fluoride-hexafluoropropylene).

[0054] The following test examples illustrate the implementation of this application in more detail. Various tests and evaluations were conducted according to the methods described below. Unless otherwise specified, "parts" and "%" refer to weight.

[0055] Experimental Example 1

[0056] Preparation of negative electrode sheet

[0057] Graphite (anode active material), conductive carbon black, and styrene-butadiene rubber were mixed in a mass ratio of 96:1.5:2.5, and deionized water was added to prepare a slurry with a solid content of 70%, which was then stirred evenly. The slurry was uniformly coated onto one surface of a 10 μm thick copper foil and dried at 110°C to obtain a single-sided negative electrode sheet with a 150 μm coating of the negative electrode active material. The coating process was then repeated on the other surface of the copper foil to obtain a double-sided negative electrode sheet with a negative electrode active material coating. After cold pressing, the electrode sheet was cut into 41 mm × 61 mm dimensions and tabs were welded on for later use.

[0058] Preparation of positive electrode sheet

[0059] LiCoO2 (positive electrode active material), conductive carbon black, and PVDF (polyvinylidene fluoride) were mixed in a mass ratio of 97.5:1.0:1.5. N-methylpyrrolidone (NMP) was added to prepare a slurry with a solid content of 75%, and the mixture was stirred evenly. The slurry was uniformly coated onto one surface of a 12 μm thick aluminum foil and dried at 90°C to obtain a positive electrode sheet with a single-sided coating of positive electrode active material layer with a coating thickness of 100 μm. The above steps were then repeated on the other surface of the aluminum foil to obtain a positive electrode sheet with a double-sided coating of positive electrode active material layer. After cold pressing, the electrode sheet was cut into 38 mm × 58 mm dimensions and tabs were welded on for later use.

[0060] Preparation of electrolyte

[0061] In a dry argon atmosphere, organic solvents EC (ethylene carbonate), EMC (ethyl methyl carbonate), and DEC (diethyl carbonate) were first mixed at a mass ratio of EC:EMC:DEC = 30:50:20. Then, LiPF6 (lithium hexafluorophosphate) was added to the organic solvents, dissolved, and mixed thoroughly to obtain an electrolyte with a LiPF6 concentration of 1.15 M. The thermal conductivity of the electrolyte was 0.152 W / (m·K).

[0062] Preparation of electrode components

[0063] A PE (polyethylene) film with a thickness of 15μm is selected as the separator. A positive electrode is placed on each side of the negative electrode. A separator is placed between the positive and negative electrode to form a stack. Then, the four corners of the entire stack structure are fixed and the positive and negative electrode tabs are led out to obtain the electrode assembly.

[0064] Preparation of the isolation component

[0065] (1) The encapsulation layer material polypropylene (PP, melting point 140℃) is uniformly dispersed in the dispersant N-methylpyrrolidone (NMP) to obtain an encapsulation layer suspension;

[0066] (2) Using a coating machine, the encapsulation layer suspension is coated around both sides of the PP substrate film with a thickness of 20μm, and then dried at 130℃ to complete the preparation of the isolation component.

[0067] The thickness of the single-sided PP encapsulation layer is 40 μm. The crystallinity of the PP substrate layer is 32%, the melting point of the PP substrate layer is 150℃, and the Li ion permeability K1 of the separator is 1.1 μg / (cm²). 2 ·h).

[0068] Assembly of electrode components

[0069] A 90μm thick aluminum-plastic film, formed by punching indentations, is placed in an assembly fixture with the indentation facing upwards. An electrode assembly A is then placed in the indentation, and tab adhesive is applied to the area corresponding to the tabs of electrode assembly A. A spacer is then placed on electrode assembly A, with one side of the spacer in contact with the diaphragm of electrode assembly A, and external force is applied to press it firmly. The above-mentioned semi-finished assembly is placed in another assembly fixture. Another electrode assembly B is placed on top of the spacer, and tab adhesive is applied to the area corresponding to the tabs of electrode assembly B. The other side of the spacer is in contact with the diaphragm of electrode assembly B. Another 90μm thick aluminum-plastic film, formed by punching indentations, is then placed over electrode assembly B with the indentation facing downwards. The positive and negative tabs of both electrode assemblies A and B are led out of the aluminum-plastic film. Finally, a hot-pressing method is used for top and side sealing to obtain the assembled electrode assembly.

[0070] Liquid injection packaging

[0071] Electrolyte is injected into the two cavities of the assembled electrode assembly, and then sealed after hot pressing, formation, and degassing.

[0072] Series connection

[0073] The positive electrode tab of electrode assembly A is welded together with the negative electrode tab of electrode assembly B, achieving series conduction between the two electrode assemblies. The lithium-ion battery assembly is now complete.

[0074] Experimental Example 2

[0075] The crystallinity of the PP substrate layer is 65%, the melting point of the PP substrate layer is 170℃, and the Li ion permeability K1 of the separator is 0.24. Other aspects are the same as in Experimental Example 1.

[0076] Experimental Example 3

[0077] The substrate layer is made of polyethylene terephthalate (PET). The crystallinity of the PET substrate layer is 55%, the melting point of the PET substrate layer is 240℃, and the Li ion permeability K1 of the separator is 0.05. Other aspects are the same as in Experimental Example 1.

[0078] Test Example 4

[0079] The crystallinity of the PET substrate layer is 62%, the melting point of the PET substrate layer is 255℃, and the Li ion permeability K1 of the separator is 0.04. Other aspects are the same as in Experiment 3.

[0080] Experimental Example 5

[0081] The substrate layer is made of polyethylene naphthalate (PEN). The crystallinity of the PEN substrate layer is 67%, the melting point of the PEN substrate layer is 260℃, and the Li ion permeability K1 of the separator is 0.03. Other aspects are the same as in Experimental Example 1.

[0082] Experimental Example 6

[0083] The crystallinity of the PEN substrate layer is 68%, the melting point of the PEN substrate layer is 265℃, and the Li ion permeability K1 of the separator is 0.02. Other aspects are the same as in Experimental Example 5.

[0084] Experimental Example 7

[0085] The substrate layer is made of Al, the pinhole density of the substrate layer is 2 pinholes / cm2, the maximum pore size of the substrate layer pinholes is 8μm, the Li ion permeability K1 of the separator is 0.92, and other parameters are the same as in Experimental Example 1.

[0086] Experimental Example 8

[0087] The pinhole density of the substrate layer is 3 pinholes / cm2, the maximum pore size of the substrate layer pinholes is 3μm, and the Li ion permeability K1 of the separator is 0.36. Other aspects are the same as in Experimental Example 7.

[0088] Experimental Example 9

[0089] The substrate layer is made of stainless steel (SUS), the pinhole density of the substrate layer is 1 pinhole / cm2, the maximum pore size of the substrate layer pinhole is 17μm, the Li ion permeability K1 of the separator is 1.2, and other parameters are the same as in Experimental Example 7.

[0090] Experimental Example 10

[0091] The pinhole density of the substrate layer is 5 pinholes / cm2, the maximum pore size of the substrate layer pinholes is 4μm, and the Li ion permeability K1 of the separator is 1.12. Other aspects are the same as in Experimental Example 9.

[0092] Experimental Example 11

[0093] The substrate layer consists of two PET films coated with silicone resin (polydimethylsiloxane) on their surfaces. The Li ion permeability K1 of the separator is 0.02, and the other properties are the same as in Example 3.

[0094] 2C charging temperature rise test

[0095] A lithium-ion battery is charged to 8.4V at a constant current of 2C at 25℃. The highest surface temperature of the lithium-ion battery is measured. The 2C charging temperature rise is equal to the highest surface temperature minus 25℃.

[0096] Thickness expansion rate test at 45℃ for 100 cycles

[0097] The thickness of the lithium-ion battery at 25℃ is measured with a micrometer and is T0. The lithium-ion battery is charged at a constant current of 0.5C to 8.4V at 45℃, then charged at a constant voltage of 8.4V to a current of 0.05C, and then discharged at a constant current of 0.5C to 6.0V. This cycle is repeated 100 times. After the 100th cycle of discharge, the lithium-ion battery is cooled to 25℃, and the thickness of the lithium-ion battery at this time is measured with a micrometer and is T1. Therefore, the thickness expansion rate after 100 cycles at 45℃ is (T1-T0) / T0×100%.

[0098] The specific parameters for each test case are shown in Table 1:

[0099] Table 1

[0100]

[0101] Referring to Test Examples 1, 9, and 10, the Li ion permeability K1 of the spacer in these three test examples at 60°C is higher than 1.0 μg / (cm³). 2 In the subsequent 45℃ cyclic thickness expansion rate test, the lithium-ion battery showed a higher expansion rate. However, the separator in Examples 2-8 exhibited a Li-ion permeability K1 ≤ 1.0 μg / (cm²) at 60℃. 2 In subsequent 45°C cyclic thickness expansion rate tests, the expansion rate of the lithium-ion battery significantly decreased. This is because the Li-ion permeability K1 through the separator at 60°C satisfies K1≤1.0μg / (cm²). 2 •h) can improve the isolation of the separator against Li ions at high temperatures, inhibit electrolyte decomposition and negative electrode metal deposition, thereby improving the durability of batteries connected in series in the same bag. See Test Examples 9 and 10; the pinhole density of the substrate layer is greater than 3 pins / cm². 2 The pinhole diameter is greater than 10μm, and the separator has poor Li ion isolation at 60℃, resulting in poor durability of the series-connected batteries in the same bag.

[0102] Referring to Test Example 11, the contact angle of the electrolyte is greater than 90°, so the temperature rise of the lithium-ion battery at 2C rate charging is greater than 15°C. The heat dissipation is poor under high rate application. As the temperature rises, the ion isolation of the separator will decrease, which will reduce the durability of the batteries connected in series in the same bag.

[0103] It should be noted that while preferred embodiments of this application are provided in the specification and accompanying drawings, this application can be implemented in many different forms and is not limited to the embodiments described herein. These embodiments are not intended to impose additional limitations on the content of this application; their purpose is to provide a more thorough and comprehensive understanding of the disclosure of this application. Furthermore, the above-described technical features can be combined with each other to form various embodiments not listed above, all of which are considered to be within the scope of this specification. Moreover, those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.

Claims

1. An electrochemical device, characterized in that, include: First shell and second shell; An isolator is located between the first housing and the second housing to define a first cavity and a second cavity on both sides of the isolator, respectively; A first electrode assembly and a second electrode assembly, wherein the first electrode assembly is disposed in the first cavity and the second electrode assembly is disposed in the second cavity; Wherein, the Li ion permeability K1 of the separator satisfies K1≤1.0μg / (cm²) 2 ·h); The Li ion permeability K1 of the isolator is tested by the following method: A first test shell and a second test shell are respectively sandwiched on opposite sides of the isolator as a receiving body. The receiving body is placed with the isolator perpendicular to the horizontal plane. A first test cavity is defined between the isolator and the first test shell, and a second test cavity is defined between the isolator and the second test shell. Dimethyl carbonate is injected into the first test cavity, and a test solution composed of lithium hexafluorophosphate and diethyl carbonate is injected into the second test cavity. Based on the mass of the test solution, the mass percentage of lithium hexafluorophosphate in the test solution is 12.5%. The volumes of dimethyl carbonate and the test solution are equal, and the liquid surface of dimethyl carbonate in the first test cavity is flush with the liquid surface of the test solution in the second test cavity, thereby forming a test body. The isolator includes a first region in contact with the dimethyl carbonate and a second region in contact with the test solution. Along the thickness direction of the isolator, the overlapping area of ​​the first region and the second region is S cm. 2 The test specimen was left to stand at 60°C for 24 hours. The Li ion content in the first test chamber was measured using inductively coupled plasma (ICP-C) to be m1 μg. The Li ion permeability of the isolator was K1 = m1 / (S×24) μg / (cm²). 2 ·h); The separator includes a substrate layer, the substrate layer including a first polymer layer, the first polymer layer having a crystallinity ≥55%.

2. The electrochemical device according to claim 1, characterized in that, The melting point of the first polymer layer is ≥170℃.

3. The electrochemical device according to claim 2, characterized in that, The isolation element also includes an encapsulation layer located on the surface of the substrate layer. The material of the first polymer layer includes at least one of the following: polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polyetheretherketone, polyimide, polyamide, polyethylene glycol, polyamide-imide, polycarbonate, cyclic polyolefin, polyphenylene sulfide, polyvinyl acetate, polytetrafluoroethylene, polymethylene naphthalene, polyvinylidene fluoride, polypropylene carbonate, poly(vinylidene fluoride-hexafluoropropylene), poly(vinylidene fluoride-co-trifluorochloroethylene), silicone, vinylon, polypropylene, anhydride-modified polypropylene, polyethylene, ethylene-propylene copolymer, polyvinyl chloride, polystyrene, polyether nitrile, polyurethane, polyphenylene ether, polyester, polysulfone, amorphous α-olefin copolymer, or derivatives thereof. The encapsulation layer is made of at least one of polypropylene, modified polypropylene, polyethylene, ethylene-propylene copolymer, ethylene-vinyl acetate copolymer, or ethylene-ethyl acrylate copolymer.

4. The electrochemical device according to claim 1, characterized in that, At least one of the following conditions (c) to (d) must be met: (c) The first cavity is provided with a first electrolyte, and the isolation member includes a first surface that contacts the first electrolyte, wherein the first contact angle of the first electrolyte on the first surface is ≤90°; (d) The second cavity is provided with a second electrolyte, and the isolation member includes a second surface that contacts the second electrolyte, wherein the second contact angle of the second electrolyte on the second surface is ≤90°.

5. The electrochemical device according to claim 4, characterized in that, The first contact angle is ≤50°; and / or the second contact angle is ≤50°.

6. The electrochemical device according to claim 4, characterized in that, The thermal conductivity of the first electrolyte is ≥0.1 W / (m·K); and / or, the thermal conductivity of the second electrolyte is ≥0.1 W / (m·K).

7. The electrochemical device according to claim 1, characterized in that, The first electrode assembly and the second electrode assembly are connected in series.

8. An electronic device, characterized in that, Includes the electrochemical device according to any one of claims 1-7.

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