Electrochemical device and electronic device

Abstract

An electrochemical device and an electronic device including the same. The electrochemical device includes a positive electrode sheet, a negative electrode sheet, a separator membrane, and an electrolyte, the separator membrane being disposed between the positive electrode sheet and the negative electrode sheet. The positive electrode sheet includes a positive electrode active material layer including a positive electrode active material and an inert material, the inert material including at least one of copper sulfide or copper chloride. At least one of the positive electrode sheet, the negative electrode sheet, the separator membrane, and the electrolyte further includes an additive capable of capturing copper ions and / or manganese ions from the positive electrode sheet.

Description

Technical Field

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

[0002] Lithium-ion batteries possess numerous advantages, including high energy density, long cycle life, high nominal voltage (>3.7V), and low self-discharge rate, leading to their widespread application in consumer electronics. To achieve sustainable development, waste cathode material powder is commonly used in the remanufacturing of lithium batteries. However, lithium batteries manufactured from waste cathode material powder suffer from issues such as poor K-value and loss of storage capacity. Summary of the Invention

[0003] One object of this application is to provide an electrochemical device that can improve poor K-value and storage capacity loss, as well as an electronic device including the electrochemical device.

[0004] This application provides an electrochemical device comprising a positive electrode, a negative electrode, a separator, and an electrolyte, wherein the separator is disposed between the positive and negative electrode. The positive electrode includes a positive active material layer, which comprises a positive active material and an inert material, wherein the inert material comprises at least one of copper sulfide or copper chloride. At least one of the positive electrode, negative electrode, separator, and electrolyte further comprises an additive capable of capturing copper ions and / or manganese ions from the positive electrode.

[0005] The inert materials copper sulfide or copper chloride in this application are obtained by oxidizing elemental copper in the cathode raw material, thereby reducing the copper content in the cathode active material layer and improving poor K-value. Furthermore, when elemental copper in the cathode raw material is oxidized to copper ions, the additive captures these copper ions, reducing the content of copper ions that can be reduced at the anode, further improving the phenomenon of puncturing the separator membrane caused by elemental copper deposited at the anode, and improving poor K-value. Moreover, when manganese dissolution occurs during use, the additive captures manganese ions, improving the phenomenon of SEI membrane damage caused by the reduction and deposition of manganese ions at the anode, and improving storage capacity loss.

[0006] According to some embodiments of this application, the additive satisfies at least one of the following conditions: the additive is capable of reacting with copper ions and / or manganese ions to form a precipitate; the additive is capable of reacting with copper ions and / or manganese ions to form a complex.

[0007] According to some embodiments of this application, the additive is selected from at least one of polysulfides, sulfides, cyanides, sulfites, phosphates, N-nitrosophenylammonium salts, or dipyrophosphate compounds.

[0008] According to some embodiments of this application, the positive electrode includes a positive current collector, a positive active material layer and a first functional layer stacked sequentially, the first functional layer containing additives; and / or the negative electrode includes a negative current collector, a negative active material layer and a second functional layer stacked sequentially, the second functional layer containing additives.

[0009] According to some embodiments of this application, the ratio of the mass of the additive to the mass of the positive electrode active material layer or the negative electrode active material layer is 10. -7 Up to 0.01. When the amount of additive added is within the above range, the poor K-value and storage capacity loss of lithium-ion batteries are reduced.

[0010] According to some embodiments of this application, the ratio of the mass of the additive to the mass of the positive electrode active material layer or the negative electrode active material layer is 10. -6 Up to 10 -5 When the amount of additive is within the above range, it can reduce both the poor K value and storage capacity loss of lithium-ion batteries, while exhibiting good cycle performance.

[0011] According to some embodiments of this application, the positive electrode includes a positive current collector and a positive active material layer stacked sequentially, the positive active material layer containing an additive; and / or the negative electrode includes a negative current collector and a negative active material layer stacked sequentially, the negative active material layer containing the additive.

[0012] According to some embodiments of this application, the separator includes a separator substrate and a third functional layer disposed on the surface of the separator substrate, the third functional layer containing additives.

[0013] According to some embodiments of this application, the positive electrode active material includes at least one of lithium iron phosphate or lithium manganese oxide. When lithium iron phosphate or lithium manganese oxide is selected as the positive electrode active material, manganese ions deposited from the positive electrode can be captured by additives, improving the phenomenon of manganese ions being reduced and deposited to form elemental manganese at the negative electrode, and reducing manganese precipitation.

[0014] A second aspect of this application also provides an electronic device, including the above-described electrochemical device, or including an electrochemical device prepared using the preparation method of the above-described electrochemical device. Detailed Implementation

[0015] The technical solutions in the embodiments of this application are described clearly and in detail below. Obviously, the described embodiments are only some, not all, of the embodiments of this application. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in the specification of this application is for the purpose of describing particular embodiments only and is not intended to limit this application.

[0016] The embodiments of this application will be described in detail below. However, this application may be embodied in many different forms and should not be construed as limited to the exemplary embodiments set forth herein. Rather, these exemplary embodiments are provided to provide a thorough and detailed understanding of this application to those skilled in the art.

[0017] As used herein, the terms “and / or” and “and / or” include any and all combinations of one or more of the related enumerated items. Additionally, it should be understood that when element A is referred to as “connecting” element B, element A may be directly connected to element B, or there may be an intermediate element C and element A and element B may be indirectly connected to each other.

[0018] Furthermore, when describing the implementation of this application, the word "may" refers to "one or more implementations of this application".

[0019] The technical terms used herein are for the purpose of describing particular embodiments and are not intended to limit this application. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. It should be further understood that the term "comprising," as used in this specification, means the presence of the described features, values, steps, operations, elements, and / or components, but does not exclude the presence or addition of one or more other features, values, steps, operations, elements, components, and / or combinations thereof.

[0020] Spatial terms, such as "above," may be used herein for convenience in describing the relationship of one element or feature to another element (or feature) or feature (or feature). It should be understood that, in addition to the direction described, spatial terms are intended to include different orientations of a device or apparatus during use or operation. For example, if the device is flipped over, an element described as "above" or "on" other elements or features will be oriented "below" or "under" other elements or features. Therefore, the exemplary term "above" can include both above and below orientations. It should be understood that although the terms first, second, third, etc., may be used herein to describe various elements, components, regions, layers, and / or portions, these elements, components, regions, layers, and / or portions should not be limited by these terms. These terms are used to distinguish one element, component, region, layer, or portion from another element, component, region, layer, or portion. Therefore, a first element, component, region, layer, or portion discussed below may be referred to as a second element, component, region, layer, or portion without departing from the teachings of the exemplary embodiments.

[0021] There are no particular limitations on the electrochemical device described in this application; it can be any electrochemical device capable of using this application, such as a lithium-ion battery or a supercapacitor. For ease of description, a lithium-ion battery is used as an example below, but this does not mean that the electrochemical device in this application is limited to lithium-ion batteries.

[0022] During the pre-processing of spent lithium-ion batteries, such as crushing and sorting, copper foil from the negative electrode can mix into the positive electrode sheet, resulting in a high content of elemental copper impurities in the resulting spent positive electrode material powder. During lithium-ion battery formation (PIEF), the elemental copper in the spent positive electrode material powder is oxidized into copper ions. These copper ions migrate to the negative electrode, where they are reduced back to elemental copper, easily puncturing the separator and causing localized internal short circuits, resulting in poor K-value.

[0023] The main types of cathode materials are ternary lithium, lithium iron phosphate, and lithium manganese oxide. Lithium iron phosphate is relatively stable and does not exhibit side reactions such as metal leaching during use, making it suitable for long-life designs. However, ternary lithium and lithium manganese oxide materials experience manganese leaching during use due to structural damage. The manganese leached from the cathode is reduced and deposited at the anode. This deposited manganese can catalyze the decomposition of the solid electrolyte interphase (SEI) film, damaging the anode interface and resulting in storage capacity loss.

[0024] This application provides an electrochemical device comprising a housing and a positive electrode, a negative electrode, a separator, and an electrolyte housed within the housing, the separator being disposed between the positive and negative electrode. The positive electrode includes a positive current collector and a positive active material layer sequentially stacked thereon. The positive active material layer may be disposed on one surface or both opposite surfaces of the positive current collector. The positive active material layer includes a positive active material and an inert material, the inert material including at least one of copper sulfide or copper chloride. At least one of the positive electrode, negative electrode, separator, and electrolyte further comprises an additive capable of capturing copper ions and / or manganese ions from the positive electrode.

[0025] Inert materials do not participate in electrochemical reactions. The inert materials, copper sulfide or copper chloride, in this application are obtained by oxidizing elemental copper in the positive electrode raw material, reducing the content of elemental copper in the positive electrode active material layer. This improves the phenomenon that elemental copper is oxidized during formation and then reduced and deposited at the negative electrode, thus mitigating the puncture of the separator caused by elemental copper deposited at the negative electrode and improving the K-value. In the lithium battery industry, the K-value refers to the voltage drop of the battery per unit time and is an indicator used to measure the self-discharge rate of lithium batteries. Furthermore, when elemental copper in the positive electrode raw material is oxidized into copper ions, the additive captures these copper ions, reducing the content of copper ions that can be reduced and deposited at the negative electrode, further improving the puncture of the separator caused by elemental copper deposited at the negative electrode and improving the K-value. Moreover, when manganese dissolution occurs during use, the additive captures manganese ions, improving the damage to the SEI film caused by the reduction and deposition of manganese ions at the negative electrode and improving storage capacity loss.

[0026] The inert materials copper sulfide or copper chloride can be prepared by oxidizing the positive electrode raw material with an oxidizing agent. The positive electrode raw material can be recycled waste positive electrode material powder. The oxidizing agent contains at least one of sulfur element or chlorine element. For example, the oxidizing agent can be selected from at least one of sulfur, ferrous sulfide or sulfur trioxide. In some other embodiments, the inert materials copper sulfide or copper chloride can also be prepared by oxidizing the positive electrode plate with an oxidizing atmosphere of a sulfur-containing atmosphere or a chlorine gas atmosphere. The sulfur-containing atmosphere can be gaseous sulfur单质, sulfur dioxide gas, gaseous sulfur trioxide, hydrogen sulfide gas, etc. In the oxidizing atmosphere, the active material layer formed by the positive electrode raw material in the positive electrode plate is directly oxidized, and among them, the elemental copper in the active material layer is oxidized to form copper sulfide or copper chloride.

[0027] The additive can react with copper ions and / or manganese ions to form a precipitate, and / or the additive can react with copper ions and / or manganese ions to form a complex, so as to capture copper ions and / or manganese ions. In some embodiments, the additive is selected from at least one of polysulfide, sulfide, cyanide, sulfite, phosphate, ammonium N-nitroso phenylhydroxamate or dipyrophosphate compound.

[0028] The positive electrode active material can be a positive electrode active substance known in the art that can reversibly deintercalate and intercalate active ions, and this application does not make any restrictions. For example, the positive electrode active material used in a lithium ion secondary battery can include one or more of lithium transition metal composite oxides, composite oxides obtained by adding other transition metals or non-transition metals or non-metals to lithium transition metal composite oxides. The transition metal can be one or more of Mn, Fe, Ni, Co, Cr, Ti, Zn, V, Al, Zr, Ce and Mg. As an example, the positive electrode active material can be selected from one or more of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium-containing phosphate with an olivine structure; such as LiMn2O4, LiNiO2, LiCoO2, LiNi 1-y Co y O2(0<y<1), LiNi a Co b Al 1-a-b O2(0<a<1, 0<b<1, 0<a+b<1), LiMn 1-m-n Ni m Co n O2(0<m<1, 0<n<1, 0<m+n<1), LiMPO4 (M can be one or more of Fe, Mn, Co) and Li3V2(PO4)3. LiMn 1-m-n Ni m Co n O2 for example is LiMn 0.1 Ni 0.8 Co0.1 O2, LiMn 0.3 Ni 0.5 Co 0.2 O2, LiMn 0.2 Ni 0.6 Co 0.2 O2, LiMn 1 / 3 Ni 1 / 3 Co 1 / 3 O2, etc.

[0029] In some embodiments, the positive electrode active material includes at least one of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium iron phosphate, or lithium cobalt phosphate. Preferably, the positive electrode active material includes at least one of LiCoO2, LiNiO2, LiMnO2, or LiCoPO4.

[0030] In some embodiments, the positive electrode active material is selected from at least one of lithium iron phosphate or lithium manganese oxide. Lithium iron phosphate has a stable structure, good thermal stability, and excellent safety performance; lithium manganese oxide has abundant mineral resources, low price, a platform voltage as high as 3.8V, excellent safety performance, and superior overcharge resistance. Using lithium iron phosphate or lithium manganese oxide as the positive electrode active material makes the electrochemical device highly safe and economically viable. Furthermore, when lithium iron phosphate or lithium manganese oxide is used as the positive electrode active material, manganese ions deposited at the positive electrode can be captured by additives, improving the phenomenon of manganese ions being reduced and deposited at the negative electrode to form elemental manganese, thus reducing manganese precipitation.

[0031] The positive current collector in this application 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 collector.

[0032] The negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer stacked sequentially. The negative electrode active material layer may be disposed on one surface or two opposite surfaces of the negative electrode current collector. The negative electrode current collector can be any negative electrode current collector known in the art, such as copper foil, copper alloy foil, or composite current collector. The negative electrode active material layer includes a negative electrode material. The negative electrode active material can be any negative electrode active material known in the art, for example, it may include at least one of graphite, hard carbon, soft carbon, silicon, silicon carbide, or silicon oxide.

[0033] Both the positive electrode active material layer and the negative electrode active material layer may further include a conductive agent and a binder. There are no particular limitations on the conductive agent; any conductive agent known in the art can be used. For example, the conductive agent may include at least one of conductive carbon black (Super P), carbon nanotubes (CNTs), carbon fibers, or graphene. There are no particular limitations on the binder; any binder known in the art can be used. For example, the binder may include at least one of styrene-butadiene rubber (SBR), polyvinyl alcohol (PVA), polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), or sodium carboxymethyl cellulose (CMC-Na).

[0034] Additives can be added to the positive and / or negative electrode sheets in various forms. For example, additives can be added to the positive and / or negative active material layers, or additives can be disposed as a separate film layer in the positive and / or negative electrode sheets. Specifically, in some embodiments, the positive and / or negative electrode material layers further include additives. In other embodiments, the positive electrode sheet further includes a first functional layer containing additives, the first functional layer being stacked on the surface of the positive active material layer opposite to the positive current collector. In other embodiments, the negative electrode sheet further includes a second functional layer containing additives, the second functional layer being stacked on the surface of the negative active material layer opposite to the negative current collector.

[0035] In some embodiments, the mass of the additive is 10 times the mass of the positive electrode active material layer or the negative electrode active material layer. -7 Up to 0.01 (or, in other words, the ratio of the mass of the additive to the mass of the positive or negative electrode active material layer is 10). -7 Within this range (up to 0.01), both poor K-value and storage capacity loss in lithium-ion batteries are reduced. Preferably, the mass of the additive is 10% of the mass of the positive or negative electrode active material layer. -6 Up to 10 -5 Within this range, while reducing both poor K-value and storage capacity loss in lithium-ion batteries, it exhibits good cycle performance.

[0036] Additives can be added to the separator membrane in various forms. For example, additives can be added directly to the separator membrane, or additives can be disposed in the separator membrane as a separate film layer. Specifically, in some embodiments, the separator membrane includes a separator membrane substrate, and the additives are disposed in the separator membrane substrate. In other embodiments, the separator membrane includes a separator membrane substrate and a third functional layer disposed on the surface of the separator membrane substrate, the third functional layer containing the additives. The separator membrane substrate can be any film known in the art as a separator membrane; for example, the separator membrane substrate can be a film selected from one or more materials selected from polyethylene, polypropylene, nonwoven fabric, and polyfiber.

[0037] The electrolyte used in this application is not particularly limited and can be any electrolyte known in the art. For example, the electrolyte is selected from solutions containing one or more carbonate organic esters such as ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate as solvents, and containing one or more lithium salts selected from LiPF6, LiBF4, LiBOB, LiAsF6, Li(CF3SO2)2N, LiCF3SO3, and LiClO4 as solutes. In some embodiments, additives are added to the electrolyte.

[0038] The casing used in this application is not particularly limited and can be any casing known in the art. For example, the casing can be a packaging bag obtained by sealing with an encapsulating film, such as aluminum-plastic film, steel-plastic film, etc.; or, the casing can be a metal casing, such as a steel casing, aluminum casing, etc.

[0039] A second aspect of this application provides an electronic device that includes the electrochemical device of this application. The electronic device can be any electrical device that uses an electrochemical device, such as a mobile phone, portable device, laptop computer, electric vehicle, electric car, ship, spacecraft, electric toy, power tool, etc.

[0040] The following specific embodiments and comparative examples are provided to better illustrate this application.

[0041] Example 1

[0042] Preparation of the positive electrode sheet: A positive electrode raw material containing lithium iron phosphate, lithium manganese oxide, and copper, a conductive agent, and a binder are mixed. The mixture includes 19 wt% lithium iron phosphate, 78 wt% lithium manganese oxide, 1.5 wt% polyvinylidene fluoride, 0.8 wt% conductive carbon black, and 0.7 wt% carbon nanotubes. The mixture is coated onto an aluminum current collector to form a positive electrode active material layer. Then, lithium sulfide is sprayed onto the surface of the positive electrode active material layer. The mass of lithium sulfide is 10 times the mass of the positive electrode active material layer. -5 After cold pressing, die cutting, and slitting, the positive electrode sheet is obtained.

[0043] Preparation of negative electrode sheet: 96wt% graphite, 1.5wt% sodium carboxymethyl cellulose, 1.5wt% polyvinylidene fluoride and 1wt% conductive carbon black are mixed and coated on copper current collector to form a negative electrode active material layer. After cold pressing, die cutting and slitting, the negative electrode sheet is obtained.

[0044] Preparation of the separator membrane: Polyethylene film was selected as the separator membrane.

[0045] Preparation of electrolyte: Ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), and methyl ethyl carbonate (EMC) were mixed in a weight ratio of 20:30:40:10 to obtain an organic solvent. Then, fully dried lithium salt LiPF6 was dissolved in the mixed organic solvent to prepare an electrolyte with a concentration of 1 mol / L.

[0046] Preparation of lithium-ion batteries: The positive electrode, polyethylene film, and negative electrode are stacked in sequence, with the polyethylene film in the middle of the positive and negative electrode, and then wound to obtain an electrode assembly; the electrode assembly is placed in an aluminum-plastic film, and after injecting electrolyte and forming, a lithium-ion battery is obtained.

[0047] Example 2

[0048] Except that lithium sulfide is sprayed onto the surface of the negative electrode active material layer instead of the positive electrode active material layer, the rest is the same as in Example 1.

[0049] Example 3

[0050] Except that lithium sulfide is sprayed onto the surface of the polyethylene film instead of onto the surface of the positive electrode active material layer, the rest is the same as in Example 1.

[0051] Example 4

[0052] Except that lithium sulfide is added to the electrolyte instead of being sprayed onto the surface of the positive electrode active material layer, the rest is the same as in Example 1.

[0053] Example 5

[0054] Except for the addition of lithium polysulfide instead of lithium sulfide to the electrolyte, the rest is the same as in Example 4.

[0055] Example 6

[0056] Except for spraying lithium cyanide instead of lithium sulfide onto the surface of the polyethylene film, the rest is the same as in Example 3.

[0057] Example 7

[0058] Besides the fact that the mass of lithium sulfide is 10 times the mass of the positive electrode active material layer... -7 Instead of 10 -5 Except for the above, it is the same as in Example 3.

[0059] Example 8

[0060] Except that the mass of lithium sulfide is 0.01 times the mass of the positive electrode active material layer, rather than 10 times. -5 Except for the above, it is the same as in Example 3.

[0061] Example 9

[0062] Besides the fact that the mass of lithium sulfide is 10 times the mass of the positive electrode active material layer... -6 Instead of 10 -5 Except for the above, it is the same as in Example 3.

[0063] Example 10

[0064] Besides the fact that the mass of lithium sulfide is 10 times the mass of the positive electrode active material layer... -8 Instead of 10 -5 Except for the above, it is the same as in Example 3.

[0065] Example 11

[0066] The only difference is that the mass of lithium sulfide is 0.1 times the mass of the positive electrode active material layer, not 10 times. -5 Except for the above, it is the same as in Example 3.

[0067] Comparative Example 1

[0068] Preparation of the positive electrode sheet: A positive electrode raw material containing lithium iron phosphate, lithium manganese oxide and copper, a conductive agent and a binder are mixed, wherein the mixture includes 19 wt% lithium iron phosphate, 78 wt% lithium manganese oxide, 1.5 wt% polyvinylidene fluoride, 0.8 wt% conductive carbon black and 0.7 wt% carbon nanotubes; the mixture is coated on an aluminum current collector, and the positive electrode sheet is obtained after cold pressing, die cutting and slitting.

[0069] Preparation of negative electrode sheet: 96wt% graphite, 1.5wt% sodium carboxymethyl cellulose, 1.5wt% polyvinylidene fluoride and 1wt% conductive carbon black are mixed and coated on copper current collector. After cold pressing, die cutting and slitting, negative electrode sheet is obtained.

[0070] Preparation of the separator membrane: Polyethylene film was selected as the separator membrane.

[0071] Preparation of electrolyte: Ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), and methyl ethyl carbonate (EMC) were mixed in a weight ratio of 20:30:40:10 to obtain an organic solvent. Then, fully dried lithium salt LiPF6 was dissolved in the mixed organic solvent to prepare an electrolyte with a concentration of 1 mol / L.

[0072] Preparation of lithium-ion batteries: The positive electrode, polyethylene film, and negative electrode are stacked in sequence, with the polyethylene film in the middle of the positive and negative electrode, and then wound to obtain an electrode assembly; the electrode assembly is placed in an aluminum-plastic film, and after injecting electrolyte and forming, a lithium-ion battery is obtained.

[0073] The lithium-ion batteries prepared in Examples 1-11 and Comparative Example 1 were subjected to the following tests.

[0074] Self-discharge rate K-value test:

[0075] The lithium-ion battery was discharged to 3.0V at 0.5C and left to stand for 5 minutes. Then, it was charged to 3.85V at a constant current of 0.5C, followed by charging at a constant voltage of 3.85V to a current of 0.05C. It was then left to stand for two days at 45℃±3℃, and the voltage was measured and recorded as V1. Next, the lithium-ion battery was left to stand at room temperature for three more days, and the voltage was measured and recorded as V2. The K value can be obtained using the following formula: K(mV / h)=(V2-V1) / 72h*1000. A K value greater than 0.02 is considered a defective product. The rate of decrease in the K value defect rate of different embodiments is compared to that of Comparative Example 1.

[0076] Storage capacity loss test:

[0077] The lithium-ion battery was charged to 4.2V at a constant current of 0.5C, and then charged to a current of 0.05C at a constant voltage of 4.2V to fully charge the lithium-ion battery; then discharged to 2.8V at a constant current of 0.5C, i.e., a discharge capacity of D1. It was then charged at a constant current of 0.5C for 36 minutes, at which point the battery's state of charge (SOC) was 30%. The battery was stored in a 60°C oven for 14 days, and then charged to 4.2V at a constant current of 0.5C, and then charged to a current of 0.05C at a constant voltage of 4.2V to fully charge the lithium-ion battery; then discharged to 2.8V at a constant current of 0.5C, i.e., a discharge capacity of D2. The storage capacity loss was 1 - D2 / D1. The percentage decrease in storage capacity loss of different embodiments was compared to that of Comparative Example 1.

[0078] Electrical performance testing (cyclic testing):

[0079] The lithium-ion battery was placed in a 45°C constant temperature chamber and left to stand for 5 minutes. Then, it was charged at a constant current of 0.5C to 4.2V, followed by constant voltage charging to 0.05C. After standing for 5 minutes, it was discharged at a constant current of 0.5C to 2.8V, and left to stand for 5 minutes. This process was repeated 1000 times, and the discharge capacity retention rate was calculated. The discharge capacity retention rates of different embodiments were compared with those of Comparative Example 1 to determine if there were any significant changes. It should be noted that when the difference between the discharge capacity retention rate of the embodiments and that of Comparative Example 1 is within ±5%, it is considered that there is no significant change and the electrical performance is not significantly affected.

[0080] The data and test results of Examples 1-11 and Comparative Example 1 are shown in Table 1.

[0081] Table 1

[0082]

[0083] Wherein, " / " represents none; "none" means that Comparative Example 1 is used as a comparison object for other embodiments, and the reduction of K value, the reduction of storage capacity loss, and the impact on electrical performance are all unchanged compared to itself.

[0084] As shown in Table 1, the addition of additives to any of the positive electrode, negative electrode, separator, and electrolyte can reduce the K-value defect rate and storage capacity loss, and has virtually no significant impact on electrical performance.

[0085] Comparing Examples 1-4, it is evident that when the additive is added to the electrolyte, the reduction in K-value defect rate and capacity loss compared to the comparative example is the greatest, indicating the greatest improvement in K-value defect rate and capacity loss. The positive electrode is immersed in the electrolyte, and the additive added to the electrolyte can fully react with copper and / or manganese ions from the positive electrode, resulting in the greatest improvement in K-value defect rate and capacity loss.

[0086] Comparing Examples 4-5, it can be seen that adding lithium sulfide and lithium polysulfide as additives to the electrolyte can improve the K-value defect rate and storage capacity loss. Among them, when the additive is lithium sulfide, the improvement in K-value defect rate and storage capacity loss is relatively large.

[0087] Comparing Examples 3 and 6, it can be seen that adding lithium sulfide and lithium cyanide as additives to the separator can improve the K-value defect rate and storage capacity loss. Among them, the battery with added lithium cyanide has a greater reduction in the K-value defect rate than the battery with added lithium sulfide, while the battery with added lithium cyanide has a smaller reduction in storage capacity loss than the battery with added lithium sulfide.

[0088] Comparing Examples 3 and 7-11, it can be seen that as the amount of additive added increases, the reduction in K-value defect rate and the reduction in storage capacity loss increase. When the amount of additive added is less than 10... -7 When the K-value defect rate decreased by less than 0.2%, the storage capacity loss decreased by less than 0.1%; when the additive dosage was greater than or equal to 0.01, the electrical performance deteriorated significantly. When the additive dosage was 10... -6 Up to 10 -5 At that time, the reduction in K-value defect rate and storage capacity was significant, while the electrical performance was not significantly affected.

[0089] The above-disclosed embodiments are merely preferred embodiments of this application and should not be construed as limiting the scope of this application. Therefore, any equivalent variations made in accordance with this application are still within the scope of this application.

Claims

1. An electrochemical device comprising a positive electrode, a negative electrode, a separating membrane, and an electrolyte, wherein the separating membrane is disposed between the positive electrode and the negative electrode, wherein, The positive electrode sheet includes a positive active material layer, which includes a positive active material, elemental copper, and an inert material. The inert material includes at least one of copper sulfide or copper chloride, which is obtained by oxidizing the elemental copper. At least one of the positive electrode, the negative electrode, the separator, and the electrolyte is further provided with an additive, which is capable of capturing copper ions generated after the oxidation of the copper element, and / or the additive is capable of capturing manganese ions from the positive electrode.

2. The electrochemical device as claimed in claim 1, wherein, The additive satisfies at least one of the following conditions: The additive can react with the copper ions and / or the manganese ions to form a precipitate; The additive can react with the copper ions and / or the manganese ions to form a complex.

3. The electrochemical device as described in claim 2, wherein, The additive is selected from at least one of polysulfides, sulfides, cyanides, sulfites, phosphates, N-nitrosophenylammonium salts, or dipyrophosphate compounds.

4. The electrochemical device as claimed in claim 1, wherein, The positive electrode sheet includes a positive current collector, the positive active material layer, and a first functional layer stacked sequentially, wherein the first functional layer contains the additive; and / or The negative electrode sheet includes a negative current collector, a negative active material layer, and a second functional layer stacked sequentially, wherein the second functional layer contains the additive.

5. The electrochemical device as described in claim 4, wherein, The mass ratio of the additive to the mass of the positive electrode active material layer or the negative electrode active material layer is 10. -7 Up to 0.

01.

6. The electrochemical device as claimed in claim 5, wherein, The mass ratio of the additive to the mass of the positive electrode active material layer or the negative electrode active material layer is 10. -6 Up to 10 -5 .

7. The electrochemical device as claimed in claim 1, wherein, The positive electrode sheet includes a positive current collector and the positive active material layer stacked sequentially, the positive active material layer containing the additive; and / or The negative electrode sheet includes a negative current collector and a negative active material layer stacked sequentially, and the negative active material layer contains the additive.

8. The electrochemical device as claimed in claim 1, wherein, The separator includes a separator substrate and a third functional layer disposed on the surface of the separator substrate, the third functional layer containing the additive.

9. The electrochemical device as claimed in claim 1, wherein, The positive electrode active material includes at least one of lithium iron phosphate or lithium manganese oxide.

10. An electronic device, wherein, It includes the electrochemical device as described in any one of claims 1 to 9.

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