WO2023216187A1 - Electrochemical device and electronic device - Google Patents

Abstract

The present application discloses an electrochemical device and an electronic device. The electrochemical device comprises a first housing, a second housing, an isolation member, a first electrode assembly and a second electrode assembly. The isolation member is located between the first housing and the second housing so as to respectively define a first cavity and a second cavity on two sides of the isolation member. The first electrode assembly is arranged in the first cavity, and the second electrode assembly is arranged in the second cavity. An Li ion permeability K1 of the isolation member satisfies K1≤1.0 μg/(cm²·h). The electrochemical device of the present application can have excellent durability.

Description

Electrochemical devices and electronic devices Technical field

The present application relates to the field of electrochemistry, and in particular to an electrochemical device and an electronic device.

Background technique

Currently, batteries are widely used in electronic products such as drones, mobile phones, tablets, and laptops. Since in some application scenarios, a single battery cell cannot achieve the desired output power; therefore, multiple battery cells are usually connected in series, parallel, or mixed, so that the multiple battery cells work together to achieve Desired power output. However, although connecting multiple battery cells in series, parallel or mixed connection can increase the output power, the energy density of the entire battery pack is low. Therefore, the design of the same-bag series battery is proposed. The same-bag series battery includes a casing and multiple electrode assemblies arranged in the same casing. The multiple electrode assemblies are connected in series outside the casing, and the multiple electrode assemblies are separated by separators. separated.

Contents of the invention

However, the inventor of the present application found through research that the durability of batteries connected in series in the same bag is insufficient and needs to be further improved.

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

In order to solve the above technical problems, a first aspect of the present application provides an electrochemical device. The electrochemical device includes a first housing, a second housing, a separator, a first electrode assembly and a second electrode assembly. The isolation piece is located between the first housing and the second housing to define a first cavity and a second cavity respectively on both sides of the isolation piece. The first electrode assembly is disposed in the first cavity, and the second electrode assembly is disposed in the second cavity. Among them, the Li ion permeability K1 of the separator satisfies K1 ≤ 1.0 μg/(cm ² ·h). The Li ion permeability K1 of the separator is tested by the following method: a first test case and a second test case are respectively sandwiched on opposite sides of the separator as a container, and the container is placed with the separator 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, Inject a test solution composed of lithium hexafluorophosphate and diethyl carbonate into the second test chamber. 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 level of dimethyl carbonate in the first test chamber is flush with the liquid level of the test solution in the second test chamber, thereby forming a test body, wherein the isolation member includes a first layer in contact with dimethyl carbonate. area and the second area in contact with the test solution, along the thickness direction of the isolator, the overlapping area of the first area and the second area is Scm ² ; the test body is left to stand at 60°C for 24 hours, and the inductively coupled plasma test is used. The Li ion content in a test chamber is m1μg, and the Li ion permeability of the isolation member is K1=m1/(S×24)μg/(cm ² ·h). Since it is difficult to dissipate heat between the electrode components inside the electrochemical device, the separator is often in high temperature working condition. The Li ion permeability K1 of the separator at 60°C satisfies K1≤1.0μg/(cm ² ·h), which can improve The isolation of Li ions by the separator at high temperatures inhibits the decomposition of the electrolyte and the deposition of negative electrode metal, thereby improving the durability of the electrochemical device.

In some embodiments, the separator includes a base material layer, the base material 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 ≤ 3 pieces/㎝ ² . (2) The maximum diameter of pinholes in the metal layer is ≤10 μm. . In the above solution, the Li ion permeability of the base material layer can be further reduced.

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

In some embodiments, the isolator further includes an encapsulation layer located on the surface of the base material layer.

In some embodiments, the material of the metal layer includes 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 at least one of stainless steel.

In some embodiments, the material of the first polymer layer includes polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polyetheretherketone, polyacyl Imine, polyamide, polyethylene glycol, polyamideimide, polycarbonate, cyclic polyolefin, polyphenylene sulfide, polyvinyl acetate, polytetrafluoroethylene, polymethylene naphthalene, polyylidene Vinyl fluoride, polypropylene carbonate, poly(vinylidene fluoride-hexafluoropropylene), poly(vinylidene fluoride-co-chlorotrifluoroethylene), silicone, vinylon, polypropylene, acid anhydride modified polypropylene , polyethylene, ethylene propylene copolymer, polyvinyl chloride, polystyrene, polyethernitrile, polyurethane, polyphenylene ether, polyester, polysulfone, amorphous α-olefin copolymer or at least one of the derivatives of the above substances kind.

In some embodiments, the material of the encapsulation layer includes at least one of polypropylene, modified polypropylene, polyethylene, ethylene-propylene copolymer, ethylene-vinyl acetate copolymer, or ethylene-ethyl acrylate copolymer.

In some embodiments, the electrochemical device satisfies at least one of the following conditions (c) to (d): (c) the first electrolyte is disposed in the first cavity, and the isolation member includes a The first surface, the first contact angle of the first electrolyte on the first surface is ≤90°. (d) The second electrolyte is disposed in the second cavity, the separator includes a second surface in contact with the second electrolyte, and the second contact angle of the second electrolyte on the second surface is ≤90°. In the above solution, the contact angle of the first surface (and/or the second surface) of the separator with respect to the first electrolyte (and/or the second electrolyte) is smaller, so that the first electrolyte (and/or the second electrolyte) After the second electrolyte) contacts the first surface (and/or the second surface) of the separator, it can extend to a larger area on the first surface (and/or the second surface) of the separator, thereby enhancing the contact between the separator and the separator. The heat exchange of the first electrolyte (and/or the second electrolyte) facilitates the transfer of heat inside the electrochemical device to the surrounding side walls through the isolation member and out of the electrochemical device, thereby reducing the internal temperature of the electrochemical device, This suppresses the decrease in ion isolation properties of the separator at high temperatures and improves the durability of the electrochemical device.

In some embodiments, the first contact angle is ≤50°; and/or, the second contact angle is ≤50°. In the above solution, the heat dissipation effect of the separator can be further improved and the internal temperature of the electrochemical device can be reduced, thereby suppressing the decrease in ion isolation properties of the separator at high temperatures and improving the durability of the electrochemical device.

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). In the above solution, the heat dissipation effect of the electrochemical device can be further improved, the operating temperature of the separator can be reduced, the reduction of ion isolation properties of the separator at high temperatures can be suppressed, and the durability of the electrochemical device can be improved.

In some embodiments, the first electrode assembly is connected in series with the second electrode assembly. In the above solution, the overall voltage of the electrochemical device can be increased and the operating current can be reduced, thereby reducing the temperature rise during operation of the electrochemical device, thereby reducing the operating temperature of the isolation member and improving the durability of the electrochemical device.

The present application also provides an electronic device, including any of the above electrochemical devices.

The electrochemical device provided by this application fully takes into account the working environment of the separator in the same bag series battery. By limiting the Li ion permeability of the separator at a high temperature of 60°C K1 ≤ 1.0 μg/(cm ² ·h), it can improve The separator can insulate Li ions at high temperatures, thereby inhibiting the decomposition of the electrolyte and the deposition of negative electrode metal, thereby improving the durability of the same-bag series battery.

Description of the drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required to be used in the embodiments of the present application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application.

Figure 1 is an exploded schematic diagram of an electrochemical device provided by the first embodiment of the present application; wherein, the electrochemical device includes two electrode assemblies and a separator;

Figure 2 is a schematic side view of an electrochemical device provided by the first embodiment of the present application;

Figure 3 is a schematic cross-sectional view of the electrochemical device provided by the first embodiment of the present application.

Figure 4 is an exploded schematic diagram of an electrochemical device provided by the second embodiment of the present application; wherein, the electrochemical device includes three electrode assemblies and two separators;

Figure 5 is a schematic side view of the isolation member provided by the first embodiment of the present application;

Figure 6 is a schematic cross-sectional view of a Li ion permeability test body of a separator provided by an embodiment of the present application;

FIG. 7 is a schematic diagram of the contact angle of the first electrolyte on the separator according to an embodiment of the present application.

Detailed ways

In order to facilitate understanding of the present application, the present application will be described in more detail below in conjunction with the accompanying drawings and specific embodiments. It should be noted that when an element is referred to as being "secured" to another element, it can be directly on the other element, or one or more intervening elements may be present therebetween. When an element is referred to as being "connected" to another element, it can be directly connected to the other element, or there may be one or more intervening elements present therebetween. The terms "vertical", "horizontal", "left", "right" and similar expressions used in this specification are for illustrative purposes only.

Unless otherwise defined, all technical and scientific terms used in this specification have the same meaning as commonly understood by a person skilled in the technical field belonging to this application. The terms used in the description of this application are only for the purpose of describing specific embodiments and are not used to limit this application. As used in this specification, the term "and/or" includes any and all combinations of one or more of the associated listed items.

The same-bag series battery includes a casing and multiple electrode assemblies arranged in the same casing. The multiple electrode assemblies are connected in series outside the casing, and the multiple electrode assemblies are separated by separators. However, the inventor of the present application found through research that due to the difficulty in dissipating heat between the electrode assemblies inside the same-bag series batteries, the separators are often in high-temperature conditions, resulting in insufficient durability of the same-bag series batteries.

In view of this, referring to FIGS. 1-7 , this embodiment provides an electrochemical device that can have good durability. The electrochemical device may be a battery 10, and further may be a lithium-ion battery 10 having multiple electrode assemblies. Specifically, referring to FIGS. 1-2 , the lithium ion battery 10 includes a first case 200 , a second case 300 , a separator 100 , a first electrode assembly 400 and a second electrode assembly 500 . The isolation member 100 is located between the first housing 200 and the second housing 300 to define a first cavity 210 and a second cavity 310 on both sides of the isolation member 100 respectively. 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 . Electrolyte is disposed in the first cavity 210 and the second cavity 310 respectively. On the one hand, the isolation member 100 is used to block the flow of electrolyte between the first cavity 210 and the second cavity 310. On the other hand, it is also used to To suppress ion transmission between the electrolyte in the first cavity 210 and the electrolyte in the second cavity 310 .

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 and reduce the operating current of the battery 10, thereby reducing the temperature rise of the battery 10 during operation and reducing the temperature of the isolation member 100. The operating temperature suppresses ion transmission between the electrolyte in the first cavity 210 and the electrolyte in the second cavity 310 , thereby improving the durability of the battery 10 .

Referring to Figures 1-3, the battery 10 in the present application may have two electrode assemblies (ie, a first electrode assembly 400 and a second electrode assembly 500) and a separator 100. A separator 100 connects the first case 200 and the second electrode assembly 500. The internal space of the second housing 300 is divided into two independent cavities (ie, the first cavity 210 and the second cavity 310). Referring to FIG. 3 , the battery 10 may also have a plurality of 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 battery 10 having one separator 100 and two electrode assemblies will be described below as an example.

In particular, after considering that it is difficult to dissipate heat between the electrode components inside the battery 10 and that the separator 100 is often in high-temperature working conditions, in this application, the Li ion permeability K1 of the separator 100 is configured to satisfy K1 ≤ 1.0 μg/ (cm ² ·h). Exemplarily, K1 may be 0.9 μg/(cm ² ·h), 0.8 μg/(cm ² ·h), 0.7 μg/(cm ² ·h), 0.6 μg/(cm ² ·h) or 0.5 μg/ (cm ² ·h) etc. Referring to FIG. 6 , the Li ion permeability K1 of the separator 100 is tested by the following method: a first test case 600 and a second test case 700 are respectively sandwiched on opposite sides of the separator 100 as a receiving body. The container is placed with the isolator 100 perpendicular to the horizontal plane. The first test cavity 800 is defined between the isolator 100 and the first test case 600 . The third test cavity 800 is defined between the isolator 100 and the second test case 700 . Two test chambers 900. Inject dimethyl carbonate into the first test chamber 800, and inject a test solution composed of lithium hexafluorophosphate and diethyl carbonate into the second test chamber 900. Based on the quality 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 level of dimethyl carbonate in the first test chamber 800 is flush with the liquid level of the test solution in the second test chamber 900, thereby forming a test body, where , the area of the first area where the isolation member 100 contacts the dimethyl carbonate in the first test chamber 800 is equal to the area of the second area where the isolation member 100 contacts the test solution in the second test chamber 900, both are Scm ² , and the first region and the second region overlap in the thickness direction of the isolator 100 . The test body was left standing at 60° C. for 24 hours, and the Li ion content in the first test chamber 800 was measured using inductively coupled plasma to be m1 μg. The Li ion permeability of the separator 100 is K1=m1/(S×24)μg/(cm ² ·h). For example, when Scm ² is 10cm ² and m1μg is 190μg, K1=190/(10×24)μg/(cm ² ·h), and K1 is approximately 0.791μg/(cm ² ·h).

After considering the influence of the temperature of the battery 10 on the ion isolation property of the separator 100, the inventor of the present application found that when the Li ion permeability K1 of the separator 100 at 60°C is ≤ 1.0 μg/(cm ² ·h), It can improve the isolation of Li ions of the separator 100 at high temperatures, suppress the decomposition of the electrolyte and the deposition of negative electrode metal, thereby improving the durability of the battery 10 .

The material and specific structure of the isolator 100 depend on the specific requirements, and the isolator 100 only needs to at least meet the above parameter requirements of Li ion permeability K1 ≤ 1.0 μg/(cm ² ·h). Specifically, referring to FIG. 5 , in one embodiment, the isolator 100 includes a base material layer 110 and two encapsulation layers (a first encapsulation layer 120 and a second encapsulation layer 130 respectively). The two encapsulation layers are respectively attached to The two side walls of the base material layer 110. In other embodiments, the isolation member 100 may have other layers, which will not be described again here. For convenience of description, the structure in which the isolator 100 only includes the base material layer 110 and two encapsulation layers will be exemplified below.

The material of the base material layer 110 depends on specific requirements. In one embodiment, the base material layer 110 includes a metal layer, and the pinhole density of the metal layer is ≤3/cm ² . This solution can reduce the Li ion permeability of the base material layer 110 . The material of the metal layer may include Ni, Ti, Cu, Ag, Au, Pt, Fe, Sn, Co, Cr, W, Mo, Al, Mg, K, Na, Ca, Sr, Ba, Ge, Sb, Pb, At least one of In, Zn or stainless steel. When the material of the base material layer 110 includes a metal layer, in one embodiment, the maximum diameter of the pinholes in the metal layer is ≤10 μm. In this solution, the Li ion permeability of the base material layer 110 can be further reduced.

In another embodiment, the base material layer 110 includes a first polymer layer, and the crystallinity of the first polymer layer is ≥50%. This solution can reduce the Li ion permeability of the base material layer 110 . The material of the first polymer layer includes polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polyether ether ketone, polyimide, polyamide, Polyethylene glycol, polyamide-imide, polycarbonate, cyclic polyolefin, polyphenylene sulfide, polyvinyl acetate, polytetrafluoroethylene, polymethylene naphthalene, polyvinylidene fluoride, polycarbonate Propyl ester, poly(vinylidene fluoride-hexafluoropropylene), poly(vinylidene fluoride-co-chlorotrifluoroethylene), silicone, vinylon, polypropylene, anhydride-modified polypropylene, polyethylene, ethylene propylene At least one of copolymers, polyvinyl chloride, polystyrene, polyethernitrile, polyurethane, polyphenylene ether, polyester, polysulfone, amorphous α-olefin copolymer or derivatives of the above substances. When the material of the base material layer 110 includes the first polymer layer, in one embodiment, the melting point of the first polymer layer is ≥170°C. In this solution, the thermal stability of the base material layer 110 can be improved.

In some embodiments, the material of the encapsulation layer includes at least one of polypropylene, modified polypropylene, polyethylene, ethylene-propylene copolymer, ethylene-vinyl acetate copolymer, or ethylene-ethyl acrylate copolymer. When the isolator 100 has two encapsulation layers, the materials of the two encapsulation layers may be the same or different.

The applicant considered that temperature has an impact on the ion isolation property of the isolator 100, and the higher the temperature of the working environment of the isolator 100, the faster the ion penetration rate. Therefore, the durability of the battery 10 can be improved by lowering the temperature of the working environment of the isolator 100 . In view of this, referring to Figure 7, in some embodiments, the electrochemical device satisfies the following conditions: the first electrolyte 20 is disposed in the first cavity 210, and the separator 100 includes a first surface in contact with the first electrolyte 20, The first contact angle α of the first electrolyte 20 on the first surface is ≤90°. In this solution, the contact angle of the first surface of the separator 100 with respect to the first electrolyte 20 is small, so that the first electrolyte 20 can contact the first surface of the separator 100 after being in contact with the first surface of the separator 100 . By extending the spacer over a larger area, the heat exchange between the isolator 100 and the first electrolyte 20 can be enhanced, thereby facilitating the heat inside the battery 10 to be transferred to the surrounding side walls through the isolator 100 and exported to the outside of the battery 10 , thereby reducing the battery 10 The internal temperature of the separator 100 is suppressed from decreasing at high temperatures, thereby improving the durability of the battery 10 .

Similarly, in another embodiment, the second electrolyte is disposed in the second cavity 310, the separator 100 includes a second surface in contact with the second electrolyte, and the second electrolyte is in second contact with the second surface. Angle ≤90°. In this solution, the contact angle of the second surface of the separator 100 with respect to the second electrolyte is small, so that the second electrolyte can spread on the second surface of the separator 100 after contacting with the second surface of the separator 100 The larger area can enhance the heat exchange between the separator 100 and the second electrolyte, thereby facilitating the transfer of heat inside the battery 10 to the surrounding side walls through the separator 100 and out of the battery 10 , thus reducing the internal temperature of the battery 10 , thereby suppressing the decrease in ion isolation properties of the separator 100 at high temperatures, thereby improving the durability of the battery 10 .

The following provides the test method for the contact angle of electrolyte: The contact angle refers to the angle between the tangent to the gas-liquid interface made at the intersection of gas, liquid and solid through the liquid and solid-liquid interface. θ, is a measure of the degree of wetting. When measuring, a contact angle measuring instrument can be used. Drop a drop of electrolyte on the surface of the separator 100 material, and use optical measurement under a measuring instrument to obtain the angle θ at which the electrolyte droplet spreads on the surface of the separator 100, which is the contact of the electrolyte on the surface of the separator 100 material. horn.

In some embodiments, the first contact angle is ≤50°, and/or the second contact angle is ≤50°. In the above solution, the heat dissipation effect of the separator 100 can be further improved, thereby suppressing the decrease in ion isolation properties of the separator 100 at high temperatures and improving the durability of the battery 10 .

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). In the above solution, the heat dissipation effect of the battery 10 can be further improved, the operating temperature of the separator 100 can be reduced, and the reduction of ion isolation properties of the separator 100 at high temperatures can be suppressed, thereby improving the durability of the battery 10 .

The present application also provides an electronic device, which includes the electrochemical device provided by the present application. The electrochemical device includes a lithium ion battery 10 . The electronic device of the present application is not particularly limited and may be any electronic device known in the art. For example, electronic devices include, but are not limited to, notebook computers, pen computers, mobile computers, e-book players, portable telephones, portable fax machines, portable copiers, portable printers, stereo headsets, video recorders, LCD televisions, portable Cleaners, portable CD players, mini discs, transceivers, electronic notepads, calculators, memory cards, portable recorders, radios, backup power supplies, motors, cars, motorcycles, power-assisted bicycles, bicycles, lighting equipment, toys, game consoles , watches, power tools, flashlights, cameras, large household batteries10 and lithium-ion capacitors, etc.

The electrode assembly of the present application is not particularly limited. Any electrode assembly in the prior art can be used as long as the purpose of the present application can be achieved. For example, a laminated electrode assembly or a wound electrode assembly can be used. The electrode assembly generally includes a positive electrode piece, a negative electrode piece and a separator.

The negative electrode piece in this application is not particularly limited, as long as it can achieve the purpose of this application. For example, a negative electrode plate typically includes a negative electrode current collector and a negative electrode active material layer. The negative electrode current collector is not particularly limited, and any negative electrode current collector known in the art can be used, such as copper foil, aluminum foil, aluminum alloy foil, composite current collector, etc. The negative active material layer includes a negative active material. The negative active material is not particularly limited, and any negative active material known in the art can be used. For example, it may include at least one of artificial graphite, natural graphite, mesocarbon microspheres, soft carbon, hard carbon, silicon, silicon carbon, lithium titanate, and the like.

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 plate typically includes a positive current collector and a positive active material. The positive electrode current collector is not particularly limited and can be any positive electrode current collector known in the art, such as aluminum foil, aluminum alloy foil or composite current collector. The positive active material is not particularly limited and can be any positive active material in the prior art. The active material includes lithium nickel cobalt manganate, lithium nickel cobalt aluminate, lithium iron phosphate, lithium cobalt oxide, lithium manganate or phosphoric acid. At least one kind of lithium iron manganese.

The electrolyte in this application is not particularly limited, and any electrolyte known in the art can be used, for example, it can be any one of gel state, solid state and liquid state. For example, the liquid electrolyte solution can include lithium salt and non-aqueous solvent.

The lithium salt is not particularly limited, and any lithium salt known in the art can be used as long as the purpose of the present application can be achieved. For example, lithium salts may include lithium hexafluorophosphate (LiPF ₆ ), lithium tetrafluoroborate (LiBF ₄ ), lithium difluorophosphate (LiPO ₂ F ₂ ), lithium bistrifluoromethanesulfonimide LiN (CF ₃ SO ₂ ) ₂ ( LiTFSI), lithium bis(fluorosulfonyl)imide Li(N(SO ₂ F) ₂ )(LiFSI), lithium bis(fluorosulfonyl)borate LiB(C ₂ O ₄ ) ₂ (LiBOB) or lithium difluoroxaloborate LiBF ₂ ( At least one of C ₂ O ₄ )(LiDFOB). For example, LiPF ₆ can be used as the lithium salt.

The non-aqueous solvent is not particularly limited as long as it can achieve the purpose of the present application. For example, the non-aqueous solvent may include at least one of a carbonate compound, a carboxylate compound, an ether compound, a nitrile compound, or other organic solvents.

For example, the carbonate compound may include diethyl carbonate (DEC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), dipropyl carbonate (DPC), methylpropyl carbonate (MPC), ethylene propylene carbonate At least one of ester (EPC), ethylene carbonate (EC), propylene carbonate (PC) or butylene carbonate (BC).

The separator in the present application is not particularly limited. For example, the separator includes a polymer or inorganic substance formed of a material that is stable to the electrolyte of the present application. The separator should generally be ion conductive and electronically insulating.

For example, the separator may include an intermediate layer and a surface treatment layer. The middle layer can be a non-woven fabric, film or composite film with a porous structure, and the material of the middle layer can be selected from at least one of polyethylene, polypropylene, polyethylene terephthalate and polyimide. Optionally, a polypropylene porous film, a polyethylene porous film, a polypropylene nonwoven fabric, a polyethylene nonwoven fabric, or a polypropylene-polyethylene-polypropylene porous composite film may be used. Optionally, a surface treatment layer is provided on at least one surface of the intermediate layer. The surface treatment layer may be a polymer layer or an inorganic layer, or may be a layer formed by mixing a polymer and an inorganic layer.

For example, the inorganic layer includes inorganic particles and a binder. The inorganic particles are not particularly limited. For example, they can be selected from aluminum oxide, silicon oxide, magnesium oxide, titanium oxide, hafnium dioxide, tin oxide, ceria, and nickel oxide. , at least one of 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 the group consisting of polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate, and polyvinylidene. One or a combination of rrolidone, polyvinyl ether, polymethylmethacrylate, polytetrafluoroethylene and polyhexafluoropropylene. The polymer layer contains a polymer, and the polymer material includes polyamide, polyacrylonitrile, acrylate polymer, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyvinyl ether, polyvinylidene fluoride or poly( At least one of vinylidene fluoride-hexafluoropropylene).

Hereinafter, the embodiment of the present application will be described in more detail with reference to test examples. Various tests and evaluations were performed according to the following methods. In addition, unless otherwise specified, "parts" and "%" are based on weight.

Test example 1

Preparation of negative electrode plates

Mix the negative active material graphite, conductive carbon black, and styrene-butadiene rubber in a mass ratio of 96:1.5:2.5, add deionized water, and prepare a slurry with a solid content of 70%, and stir evenly. The slurry is evenly coated on one surface of a copper foil with a thickness of 10 μm, and dried at 110°C to obtain a negative electrode sheet with a coating thickness of 150 μm coated with a negative active material layer on one side, and then the copper foil is Repeat the above coating steps on the other surface to obtain a negative electrode piece coated with a negative active material layer on both sides. After cold pressing, cut the pole piece into 41mm×61mm specifications and weld the pole lug for later use.

Preparation of positive electrode plates

Mix the positive active material LiCoO ₂ , conductive carbon black, and PVDF (polyvinylidene fluoride) at a mass ratio of 97.5:1.0:1.5, add N-methylpyrrolidone (NMP), and prepare a slurry with a solid content of 75%. Mix well. The slurry is evenly coated on one surface of an aluminum foil with a thickness of 12 μm, and dried at 90°C to obtain a positive electrode sheet coated with a positive active material layer on one side with a coating thickness of 100 μm. Then repeat the above steps on the other surface of the aluminum foil to obtain a positive electrode sheet coated with a positive active material layer on both sides. After cold pressing, cut the pole pieces into 38mm×58mm specifications and weld the tabs for later use.

Preparation of electrolyte

In a dry argon atmosphere, first mix the organic solvents EC (ethylene carbonate), EMC (ethyl methyl carbonate) and DEC (diethyl carbonate) in a mass ratio of EC:EMC:DEC=30:50:20, and then Add LiPF ₆ (lithium hexafluorophosphate) to the organic solvent to dissolve and mix evenly to obtain an electrolyte with a LiPF ₆ concentration of 1.15M. Among them, the thermal conductivity of the electrolyte is 0.152W/(m·K).

Preparation of electrode assembly

Use a PE (polyethylene) film with a thickness of 15 μm as the isolation film, place a positive electrode piece on both sides of the negative electrode piece, and place a layer of isolation film between the positive electrode piece and the negative electrode piece to form a stack, and then the entire stack The four corners of the chip structure are fixed, and the positive and negative electrode tabs are drawn out to obtain the electrode assembly.

Preparation of spacers

(1) Evenly disperse the encapsulation layer material polypropylene (PP, melting point: 140°C) into the dispersant N-methylpyrrolidone (NMP) to obtain an encapsulation layer suspension;

(2) Use a glue applicator to apply the encapsulation layer suspension around the two surfaces of the PP substrate layer film with a thickness of 20 μm, and then dry it at 130°C to complete the preparation of the isolator.

Among them, the thickness of the PP encapsulation layer on one side is 40 μm. The crystallinity of the PP base material layer is 32%, the melting point of the PP base material layer is 150°C, and the Li ion permeability K1 of the separator is 1.1 μg/(cm ² ·h).

Assembly of the electrode assembly

Place the punched aluminum-plastic film with a thickness of 90 μm in the assembly fixture, with the pit facing upward, then place an electrode assembly A in the pit, and set tab glue in the area corresponding to the tab of electrode assembly A. Then place the separator on the electrode assembly A, with one side of the separator in contact with the diaphragm of the electrode assembly A, and apply external force to compress it. Place the above-mentioned assembled semi-finished product in another assembly fixture, place the other electrode assembly B on the separator, and set tab glue in the area corresponding to the tab of electrode assembly B. The other side of the separator is in contact with the electrode assembly B. The separator is in contact, and then another punched aluminum plastic film with a thickness of 90 μm is placed face down on the electrode assembly B, and the positive and negative electrode tabs of electrode assembly A and electrode assembly B are led out of the aluminum plastic film. In addition, hot pressing is used for top sealing and side sealing to obtain the assembled electrode assembly.

Liquid injection packaging

The electrolyte is injected into the two cavities of the above-mentioned assembled electrode assembly respectively, and is sealed after hot pressing, chemical formation, degassing.

Series connection

Weld the positive tab of electrode assembly A and the negative tab of electrode assembly B together to achieve series conduction between the two electrode assemblies. The lithium-ion battery assembly is completed.

Test example 2

The crystallinity of the PP base material layer is 65%, the melting point of the PP base material layer is 170°C, and the Li ion permeability K1 of the separator is 0.24. The other conditions are the same as in Test Example 1.

Test example 3

The material of the base material layer is polyethylene terephthalate (PET). The crystallinity of the PET base material layer is 55%, the melting point of the PET base material layer is 240°C, and the Li ion permeability K1 of the separator is 0.05. Others are the same as Test Example 1.

Test example 4

The crystallinity of the PET base material layer was 62%, the melting point of the PET base material layer was 255°C, and the Li ion permeability K1 of the separator was 0.04. The other conditions were the same as in Test Example 3.

Test example 5

The material of the base material layer is polyethylene naphthalate (PEN). The crystallinity of the PEN base material layer is 67%. The melting point of the PEN base material layer is 260°C. The Li ion permeability K1 of the separator is 0.03. Others Same as Test Example 1.

Test example 6

The crystallinity of the PEN base material layer is 68%, the melting point of the PEN base material layer is 265° C., and the Li ion permeability K1 of the separator is 0.02. The other aspects are the same as Test Example 5.

Test example 7

The material of the base material layer is Al, the pinhole density of the base material layer is 2/cm, the maximum pore diameter of the pinholes of the base material layer is 8 μm, and the Li ion permeability K1 of the separator is 0.92. Others are the same as Test Example 1.

Test example 8

The pinhole density of the base material layer is 3/cm, the maximum pore diameter of the base material layer pinholes is 3 μm, and the Li ion permeability K1 of the separator is 0.36. The other conditions are the same as Test Example 7.

Test example 9

The material of the base material layer is stainless steel (SUS). The pinhole density of the base material layer is 1/cm. The maximum pinhole diameter of the base material layer is 17 μm. The Li ion permeability K1 of the separator is 1.2. Others and test examples 7 is the same.

Test example 10

The pinhole density of the base material layer was 5/cm, the maximum pore size of the pinholes of the base material layer was 4 μm, and the Li ion permeability K1 of the separator was 1.12. Others were the same as Test Example 9.

Test example 11

The material of the base material layer is a PET film with two surfaces coated with silicone resin (polydimethylsiloxane). The Li ion permeability K1 of the separator is 0.02. The rest is the same as in Test Example 3.

2C charging temperature rise test

Charge the lithium-ion battery to 8.4V at a constant current of 2C in an environment of 25°C, and measure the maximum surface temperature of the lithium-ion battery. Then the 2C charging temperature rise = the maximum surface temperature -25°C.

Thickness expansion rate test after 100 cycles at 45℃

Use a micrometer to measure the thickness of the lithium-ion battery at 25°C as T0. Charge the lithium-ion battery at a constant current of 0.5C to 8.4V at 45°C, then charge it at a constant voltage of 8.4V to a current of 0.05C, and then charge it at a constant current of 0.5C. Discharge to 6.0V and repeat the above cycle 100 times. After the 100th cycle of discharge, wait for the lithium-ion battery to cool to 25°C. Use a micrometer to measure the thickness of the lithium-ion battery at this time as T1. Then the thickness expansion rate after 100 cycles at 45°C =(T1-T0)/T0×100%.

Please refer to Table 1 for the specific parameters of each test example:

Table 1

Refer to Test Example 1, Test Example 9 and Test Example 10. The Li ion permeability K1 of the separators in the above three test examples at 60°C is higher than 1.0 μg/(cm ² ·h). In the subsequent 45°C cycle In the thickness expansion rate test, the expansion rate of lithium-ion batteries is relatively high. The Li ion permeability K1 of the separator in Test Example 2-8 at 60°C is ≤1.0 μg/(cm ² ·h). In the subsequent 45°C cycle thickness expansion rate test, the expansion rate of the lithium-ion battery was significantly reduced. . This is because the Li ion permeability K1 of the separator at 60°C satisfies K1 ≤ 1.0 μg/(cm ² ·h), which can improve the isolation of Li ions by the separator at high temperatures, inhibit the decomposition of the electrolyte, and The deposition of negative electrode metal, in turn, can improve the durability of batteries connected in series in the same bag. Refer to Test Example 9 and Test Example 10. The pinhole density of the base material layer is greater than 3/㎝ ² /the maximum pore diameter of the pinhole is greater than 10 μm. The Li ion isolation performance of the separator at 60°C is poor, resulting in series connection of the same bag. Batteries have poor durability.

Refer to Test Example 11. The contact angle of the electrolyte is greater than 90°, so the temperature rise of the lithium-ion battery during 2C rate charging is greater than 15°C. The heat dissipation is poor under high-rate applications. As the temperature increases, the ion isolation of the isolator The performance will be reduced, which will reduce the durability of batteries connected in series in the same bag.

It should be noted that the preferred embodiments of the present application are given in the description and drawings of this application. However, the present application can be implemented in many different forms and is not limited to the embodiments described in this specification. These embodiments are not used as additional limitations on the content of the present application, and are provided for the purpose of making the disclosure of the present application more thorough and comprehensive. Moreover, the above technical features can be continuously combined with each other to form various embodiments not listed above, which are all deemed to be within the scope of the description of this application; further, for those of ordinary skill in the art, they can be improved or transformed according to the above description. , and all these improvements and transformations should fall within the protection scope of the claims appended to this application.

Claims (9)

An electrochemical device, characterized by including: a first housing and a second housing; A spacer located between the first housing and the second housing to respectively define a first cavity and a second cavity on both sides of the spacer; A first electrode assembly and a second electrode assembly, the first electrode assembly is located in the first cavity, and the second electrode assembly is located in the second cavity; Wherein, the Li ion permeability K1 of the separator satisfies K1≤1.0μg/(cm ² ·h); The Li ion permeability K1 of the separator is tested by the following method: a first test case and a second test case are respectively sandwiched on opposite sides of the separator as a container, and the container is placed as described The isolation member is placed perpendicular to the horizontal plane, a first test cavity is defined between the isolation member and the first test housing, and a second test cavity is defined between the isolation member and the second test housing. Cavity; inject dimethyl carbonate into the first test chamber, inject a test solution composed of lithium hexafluorophosphate and diethyl carbonate into the second test chamber, based on the quality of the test solution, the The mass percentage of lithium hexafluorophosphate in the test solution is 12.5%; the volumes of the dimethyl carbonate and the test solution are equal, and the liquid level of the dimethyl carbonate in the first test chamber is equal to the The liquid level of the test solution in the second test chamber is flush, thereby forming a test body, wherein the isolation member includes a first area in contact with the dimethyl carbonate and a third area in contact with the test solution. Two regions, along the thickness direction of the isolator, the overlapping area of the first region and the second region is Scm ² ; the test body is left to stand at 60°C for 24 hours, and an inductively coupled plasma test is performed. The Li ion content in the first test chamber is m1 μg, and the Li ion permeability of the isolation member is K1 = m1/(S×24) μg/(cm ² ·h). The electrochemical device according to claim 1, wherein the separator includes a base material layer, the base material layer includes a metal layer, and satisfies at least one of the following conditions (1) to (2): (1) The pinhole density of the metal layer is ≤3/ ^cm2 ; (2) The maximum diameter of pinholes in the metal layer is ≤10 μm. The electrochemical device according to claim 1, wherein the separator includes a base material layer, the base material layer includes a first polymer layer, and satisfies at least one of the following conditions (a) to (b). By: (a) The crystallinity of the first polymer layer is ≥50%; (b) The melting point of the first polymer layer is ≥170°C. The electrochemical device according to claim 2 or 3, characterized in that, The isolator further includes an encapsulation layer located on the surface of the base material layer, The materials of the metal layer include 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 at least one of stainless steel; The material of the first polymer layer includes polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polyether ether ketone, polyimide, poly Amide, polyethylene glycol, polyamide-imide, polycarbonate, cyclic polyolefin, polyphenylene sulfide, polyvinyl acetate, polytetrafluoroethylene, polymethylene naphthalene, polyvinylidene fluoride, poly Propylene carbonate, poly(vinylidene fluoride-hexafluoropropylene), poly(vinylidene fluoride-co-chlorotrifluoroethylene), silicone, vinylon, polypropylene, acid anhydride modified polypropylene, polyethylene, At least one of ethylene propylene copolymer, polyvinyl chloride, polystyrene, polyethernitrile, polyurethane, polyphenylene ether, polyester, polysulfone, amorphous α-olefin copolymer or derivatives of the above substances; The material of the encapsulation layer includes at least one of polypropylene, modified polypropylene, polyethylene, ethylene-propylene copolymer, ethylene-vinyl acetate copolymer or ethylene-ethyl acrylate copolymer. The electrochemical device according to claim 1, characterized in that at least one of the following conditions (c) to (d) is satisfied: (c) A first electrolyte is disposed in the first cavity, the isolator includes a first surface in contact with the first electrolyte, and the first electrolyte is disposed on a first surface of the first surface. Contact angle ≤90°; (d) A second electrolyte is disposed in the second cavity, the separator includes a second surface in contact with the second electrolyte, and the second electrolyte is disposed on a second surface of the second surface. Contact angle ≤90°. The electrochemical device according to claim 5, characterized in that The first contact angle is ≤50°; and/or, the second contact angle is ≤50°. The electrochemical device according to claim 5, characterized in that The thermal conductivity of the first electrolyte is ≥0.1W/(m·K); and/or the thermal conductivity of the second electrolyte is ≥0.1W/(m·K). The electrochemical device according to claim 1, wherein the first electrode assembly and the second electrode assembly are connected in series. An electronic device, characterized by comprising the electrochemical device according to any one of claims 1-8.

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