Secondary battery and electric equipment

Abstract

The invention provides a secondary battery and electric equipment, the secondary battery comprises an oxygen removal material, and the oxygen removal material comprises one or more of selenium, activated carbon, a catalyst and a perovskite oxygen storage material; the catalyst comprises at least one of Pt, Pd, Ag and Ce < 1-x > CuxO < 2-x >, and x is 0-1. The secondary battery provided by the invention can effectively solve the problem of gas production of the battery and improve the safety performance of the battery.

Description

Technical Field

[0001] The present invention relates to a secondary battery, in particular to a secondary battery and an electrical device, belonging to the field of secondary batteries. Background Art

[0002] Lithium-ion batteries have the advantages of high energy density and long cycle life, and have been widely used in the field of power batteries. Battery safety, as one of the characteristics that consumers are most concerned about, is an eternal topic. During the use of the battery, with the side reactions at the electrode / electrolyte interface, the battery continues to produce gas. On the one hand, it will cause the internal pressure of the battery to increase and eventually cause an explosion. On the other hand, the generated gas contains dangerous gases such as hydrogen (combustible gas) and oxygen (combustion-supporting gas), which increases the safety risk of thermal runaway of the battery. In addition, according to existing experimental results, as the battery ages, the gas production increases, further reducing safety.

[0003] At present, the main measure to deal with the safety hazards caused by battery gas production is to add an explosion-proof valve, such as Figure 1 When the gas inside the battery accumulates and the pressure increases to a certain threshold, the explosion-proof valve opens to release the pressure and exhaust gas to prevent further danger.

[0004] However, the design of the explosion-proof valve still has shortcomings: ① For different types of batteries, their pressure thresholds need to be re-evaluated to meet safety requirements, and the regulation of the thresholds must be relatively precise. Opening the valve too early will cause false alarms and battery scrapping, while opening the valve too late will bring safety risks. ② When the ternary system battery produces gas during thermal runaway, the heat generation time is extremely short, and there is often a violent reaction when the valve is opened. The explosion-proof valve cannot prevent thermal runaway, and the high-temperature heat flow is instantly discharged through the valve port, which often causes secondary damage. ③ There is still a large amount of dangerous gas in the gas discharged through the explosion-proof valve. If it cannot be properly handled, there is still a certain safety risk.

[0005] Therefore, it is urgent to explore technical solutions to solve the problem of battery gas production and improve battery safety performance. Summary of the invention

[0006] The present invention provides a secondary battery, which can effectively solve the problem of battery gas generation and improve the safety performance of the battery.

[0007] The present invention provides an electrical device, comprising the secondary battery, which has excellent safety performance.

[0008] In one aspect, the present invention provides a secondary battery, wherein the secondary battery comprises an oxygen scavenging material, wherein the oxygen scavenging material comprises one or more of selenium, activated carbon, a catalyst, and a perovskite oxygen storage material; wherein the catalyst comprises Pt, Pd, Ag, Ce, 1-x Cu x O 2-x At least one of , x is 0-1.

[0009] In the secondary battery as described above, the oxygen scavenging material includes selenium.

[0010] In the secondary battery as described above, based on the mass of the positive electrode active material in the secondary battery, the mass content of the oxygen scavenging material is 0.5 wt % to 2 wt %.

[0011] In the secondary battery as described above, the particle size D50 of the oxygen scavenging material is ≤100 μm.

[0012] The secondary battery as described above, wherein the secondary battery comprises an electrode sheet, wherein the electrode sheet comprises a current collector and an active material layer;

[0013] The active material layer includes an active material and an oxygen scavenging material;

[0014] And / or, a deoxygenating material layer is disposed on at least one surface of the current collector and / or the active material layer, and the deoxygenating material layer includes the deoxygenating material.

[0015] In the secondary battery as described above, the active material is a positive electrode active material, and the oxygen scavenging material is coated on the surface of the positive electrode active material.

[0016] The secondary battery as described above, wherein the oxygen scavenging material layer further comprises a binder;

[0017] Preferably, the deoxidizing material layer comprises 97-99% of deoxidizing material and 1-3% of binder by mass.

[0018] The secondary battery as described above comprises a separator, at least one surface of which is provided with an oxygen scavenging material layer, wherein the oxygen scavenging material layer comprises the oxygen scavenging material.

[0019] The secondary battery as described above includes a solid electrolyte layer, and the solid electrolyte layer includes the oxygen scavenging material.

[0020] Another aspect of the present invention provides an electrical device including the secondary battery as described above.

[0021] The secondary battery provided by the present invention includes a specific type of oxygen removal material, which can effectively remove oxygen or active oxygen generated during the use of the battery, reduce the damage of oxygen to the battery, and improve the safety performance of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a schematic diagram of the structure of an explosion-proof valve in an existing battery;

[0023] Figure 2 It is a schematic diagram of the structure of a positive electrode sheet in a specific embodiment of the present invention;

[0024] Figure 3 It is a schematic structural diagram of a positive electrode sheet in another specific embodiment of the present invention;

[0025] Figure 4 DEMS oxygen production content-time curve in the first week 2.8-3.6V cycle of the secondary battery provided in Example 1, Example 2 and Comparative Example 1 of the present invention;

[0026] Figure 5 The heat flow-temperature curves of the secondary batteries provided in Example 1 and Comparative Example 1 of the present invention;

[0027] Figure 6 Schematic diagram of the composition of selenium in a secondary battery in some embodiments of the present invention.

[0028] Description of reference numerals:

[0029] 1-current collector; 2-oxygen removal material layer; 3-active material layer. DETAILED DESCRIPTION

[0030] In order to make the purpose, technical solutions and advantages of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in combination with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0031] In one aspect, the present invention provides a secondary battery, the secondary battery includes an oxygen scavenging material, the oxygen scavenging material includes one or more of selenium, activated carbon, a catalyst, and a perovskite oxygen storage material, the catalyst includes Pt, Pd, Ag, Ce, 1-x Cu x O 2-x At least one of , x is 0-1.

[0032] The secondary battery of the present invention may be any type of battery that has a risk of oxygen evolution, such as a lithium secondary battery, a sodium secondary battery, a potassium secondary battery, and the like.

[0033] The deoxygenating material in the present invention refers to a material that can remove oxygen or active oxygen, wherein active oxygen refers to a single-electron reduction product of oxygen, i.e., oxidized oxygen O α- , 0<α<2.

[0034] During the long-term cycle of the battery, lithium ions are constantly removed and embedded, causing the lattice to shrink and expand repeatedly, and eventually leading to the gradual decline of the positive electrode active material. The oxygen atoms in the positive electrode are separated from the lattice and react with highly active oxidizing oxygen O α- This will not only lead to the gradual collapse of the positive electrode structure, but also cause the electrolyte to be oxidized to form serious side reactions. From the perspective of battery safety, the oxygen generated in the battery will increase the internal pressure and expansion force of the battery, and promote the occurrence of thermal runaway of the battery.

[0035] When selenium is included in the secondary battery, after the oxygen is precipitated from the positive electrode active material, free active oxygen is formed, leaving oxygen vacancies in the lattice. The intervention of Se will capture the active oxygen and occupy the oxygen vacancies, as shown in the following reaction formula:

[0036]

[0037] Reactive oxygen α- The diffusion barrier of Se will be affected by the surrounding O vacancies. After Se occupies the O vacancies, it can hinder the diffusion of O α- On the other hand, it is reduced to more stable immobile O 2- , which plays a role in stabilizing the lattice O. Se that does not enter the O vacancy and remains on the surface of the material will directly combine with the escaped active O to form SeO2 to wrap the material. On the one hand, SeO2 acts as a shell to block the possible escape of oxygen (evolved from active oxygen), and on the other hand, it can resist the attack of HF generated in the electrolyte and protect the interface. At the same time, Se also has an inhibitory effect on the generation of oxygen free radicals (HO· / O2·) in the electrolyte, thereby preventing the oxidative decomposition of the electrolyte, alleviating the occurrence of side reactions, thinning SEI / CEI, and facilitating battery kinetic transmission.

[0038] Active oxygen is absorbed, which inhibits the generation of oxygen in the battery, which can alleviate the gas production inside the battery to a certain extent and reduce the increase in expansion force. More importantly, when the battery experiences thermal runaway, the oxygen evolution at the positive electrode active material is an important node in the entire thermal runaway chain reaction. By cutting off the oxygen production path through Se treatment, the possibility of thermal runaway in the battery is greatly reduced, thereby improving the battery safety performance.

[0039] When activated carbon is included in a secondary battery, deoxygenation can be achieved through physical adsorption and chemical adsorption. On the one hand, activated carbon has a large number of micropores and macropores, which can capture oxygen through physical adsorption to achieve oxygen adsorption. On the other hand, the small amount of chemical bonds and functional groups on the surface of activated carbon can also react chemically with oxygen to form chemical bonds.

[0040] When the secondary battery includes a catalyst, the types of the catalyst include but are not limited to Pt, Pd, Ag, Ce 1-x Cu x O 2-x At least one of the above, x is 0-1; substances that can react with O2, such as H2, Co, CH4, etc., are oxidized and adsorbed in the active sites of the catalyst, and then react with O 2- Catalytic reaction is performed to remove oxygen.

[0041] Perovskite oxygen storage materials include but are not limited to at least one of metal oxide perovskite, organic hybrid perovskite, and inorganic halogen perovskite. When a secondary battery includes a perovskite oxygen storage material, the perovskite oxygen storage material has oxygen vacancies, and oxygen is embedded in the oxygen vacancies through an oxidation reaction, thereby playing a role in deoxygenation.

[0042] The secondary battery provided by the present invention has excellent safety performance. The inventors have analyzed this and believe that the reason may be that when the secondary battery includes the above-mentioned materials, different mechanisms are used to remove oxygen or active oxygen generated during the use of the battery, alleviate gas production inside the battery, reduce the increase in expansion force, greatly reduce the possibility of thermal runaway of the battery, and improve the safety performance of the battery.

[0043] Furthermore, in one embodiment of the present invention, the oxygen scavenging material includes selenium.

[0044] As mentioned above, when oxygen is released from the positive electrode active material, active oxygen ions escape O α- (α<2), Se captures oxygen ions, and loses electrons to form positive Se to occupy oxygen vacancies, which increases the diffusion barrier of oxygen ions, and the active oxygen obtains electrons and is reduced to a -2 valence state, which is more stable and prevents the formation of oxygen. In addition to Se occupying oxygen vacancies, Se can also form an inert SeO coating on the surface of the positive electrode by combining with O ions, thereby inhibiting side reactions at the positive electrode, and can act as a shell to inhibit oxygen escape. Moreover, Se captures highly oxidizing active oxygen free radicals to prevent them from entering the electrolyte to oxidize the electrolyte. By capturing active oxygen, the generation of dangerous gas oxygen in the battery is reduced, and the deoxygenation effect is more timely and effective, further improving the safety performance of the battery.

[0045] The present invention does not limit the specific location or existence form of selenium in the secondary battery. Figure 6 As shown, selenium can be coated on the surface of copper foil, aluminum foil or diaphragm to form oxygen-absorbing foil or oxygen-absorbing diaphragm, and can also be combined with binder, conductive agent and main material (positive electrode active material / negative electrode active material) to form oxygen-absorbing slurry.

[0046] Further, in a specific embodiment of the present invention, based on the mass of the positive electrode active material in the secondary battery, the mass content of the oxygen scavenging material is 0.5 wt %-2 wt %.

[0047] In detail, based on the mass of the positive electrode active material in the secondary battery, the mass content of the oxygen scavenging material includes but is not limited to 0.5wt%, 0.6wt%, 0.8wt%, 1.0wt%, 1.2wt%, 1.4wt%, 1.6wt%, 1.8wt%, 2.0wt% or a range composed of any two thereof.

[0048] When the above-mentioned mass relationship exists between the deoxygenating material and the positive electrode active material, not only can the deoxygenating material fully exert its deoxygenating effect, but also the influence of the deoxygenating material on the conductivity can be effectively reduced, maintaining normal electron transport performance and ion transport performance.

[0049] Furthermore, in a specific embodiment of the present invention, the particle size D50 of the deoxidizing material is ≤100 μm.

[0050] The particle size D50 of the deoxidizing material refers to the median of the particle size distribution, representing the average size of the deoxidizing material particle size.

[0051] The particle size of the deoxidizing material can be measured by common methods in the art, such as laser particle size analysis.

[0052] Specifically, the particle size of the deoxidizing material includes but is not limited to 100 μm, 95 μm, 90 μm, 85 μm, 80 μm, 75 μm, 70 μm, 65 μm, etc., any range not higher than 100 μm.

[0053] The present invention does not limit the method for controlling the particle size of the deoxygenating material, and the deoxygenating material with the desired particle size can be obtained by common methods, such as ball milling.

[0054] In a specific embodiment, the deoxygenating material is selenium, and the particle size of commercially available selenium particles on the market is 1-6 mm. The particles are ball-milled at 4000 rpm for 24 hours to obtain selenium particles with a particle size D50≤100 μm that meets the above size limitation.

[0055] When the particle size of the deoxygenating material is within the above range, it can provide a larger surface area, contact with oxygen more quickly, and improve the deoxygenation efficiency. Moreover, the deoxygenating material within the above particle size range can be more evenly distributed in the secondary battery, ensuring a more comprehensive deoxygenation effect, thereby improving the safety performance of the battery.

[0056] Further, in a specific embodiment of the present invention, the secondary battery includes an electrode sheet, the electrode sheet includes a current collector and an active material layer; the active material layer includes an active material and an oxygen scavenging material;

[0057] And / or, a deoxygenating material layer is disposed on at least one surface of the current collector and / or the active material layer, and the deoxygenating material layer includes a deoxygenating material.

[0058] The present invention does not limit the polarity of the electrode sheet, and it can be a positive electrode sheet or a negative electrode sheet.

[0059] When the active material layer includes active materials and deoxidizing materials, the electrode sheet can be prepared by a common method in the art. In a specific embodiment, a mixed slurry including deoxidizing materials and active materials is coated on at least one side of the current collector, and then rolled, dried, etc. to obtain an electrode sheet.

[0060] Active materials will generate oxygen or reactive oxygen during the secondary battery cycle. When the active material layer includes active materials and deoxygenating materials, the deoxygenating materials can absorb oxygen or reactive oxygen more efficiently to ensure the safety performance of the battery.

[0061] When a deoxygenating material layer is disposed on at least one surface of the current collector and / or the active material layer, and the deoxygenating material layer includes a deoxygenating material, the deoxygenating material layer may be between the current collector and the active material layer or on the surface of the active material layer.

[0062] In a specific embodiment, Figure 2 As shown, the oxygen scavenging material layer 2 is located between the current collector 1 and the active material layer 3 .

[0063] In another specific embodiment, Figure 3 As shown, the oxygen scavenging material layer 2 is located on the surface of the active material layer 3 .

[0064] When a secondary battery includes an oxygen scavenging material layer disposed on at least one side of the current collector and / or active material layer, it can absorb active oxygen generated during the battery cycle, prevent the generation of oxygen, and ensure the safety of the battery throughout its life cycle.

[0065] It can be understood that when the electrode sheet is a positive electrode sheet, the current collector can be selected from common positive electrode current collectors in the art, such as at least one of aluminum foil and nickel foil.

[0066] The active material can be selected from the common positive electrode active materials in the field. In a specific embodiment, the secondary battery is a lithium ion secondary battery, and the positive electrode active material is selected from at least one of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium manganese oxide, nickel cobalt manganese ternary material, nickel cobalt aluminum ternary material, lithium iron phosphate (LFP), lithium nickel manganese oxide, lithium-rich manganese-based materials, etc.

[0067] When the electrode sheet is a negative electrode sheet, the current collector may be selected from common negative electrode current collectors in the art, such as at least one of copper foil, nickel foam, and copper foam. The active material may be selected from common negative electrode active materials in the art, such as at least one of graphite, hard carbon, soft carbon, mesophase carbon microspheres, silicon-based negative electrode materials (mainly including silicon oxide, silicon-carbon negative electrode), tin-based negative electrode materials (mainly including tin, tin alloy), etc.

[0068] Furthermore, in a specific embodiment of the present invention, the active material is a positive electrode active material, and the oxygen scavenging material is coated on the surface of the positive electrode active material.

[0069] In detail, the oxygen scavenging material is coated on the surface of the positive electrode active material to form a core-shell structure.

[0070] The present invention does not limit the coating method of the deoxidizing material on the surface of the positive electrode active material, and common coating methods in the art, such as coprecipitation, ball milling, spray drying, etc., can be used.

[0071] In a specific embodiment, mechanical fusion is used to coat the surface of the positive electrode active material with the deoxygenating material, including the following steps: using a mechanical fusion machine at 4000 rpm in an inert atmosphere to treat the positive electrode active material and the deoxygenating material for 20 minutes to uniformly coat them.

[0072] During the battery cycle, the oxygen atoms in the positive electrode active material are separated from the lattice and react with highly active oxidative oxygen O α- When the oxygen scavenging material is coated on the surface of the positive electrode active material, it can more efficiently block the movement of active oxygen and prevent the active oxygen from evolving into oxygen overflow, thereby improving the safety performance of the battery.

[0073] Further, in a specific embodiment of the present invention, the deoxidizing material layer further includes a binder;

[0074] Preferably, the deoxidizing material layer comprises 97-99% of deoxidizing material and 1-3% of binder by mass.

[0075] In detail, after adding the binder, the connection tightness between the deoxygenating materials in the deoxygenating material layer 2 can be improved, and the stability between the deoxygenating material layer 2 and the current collector 1 and / or the active material layer can be improved.

[0076] The mass content of the deoxygenating material in the deoxygenating material layer 2 includes but is not limited to 97%, 97.5%, 98%, 98.5%, 99% or a range between any two of them.

[0077] When the mass contents of the deoxygenating material and the binder are within the above range, the deoxygenating effect of the deoxygenating material can be fully exerted while ensuring the stability of the battery structure.

[0078] The present invention does not limit the specific type of the binder, and can select any of the common secondary battery binders in the art, such as at least one of polytetrafluoroethylene, polyvinylidene fluoride, polyvinyl fluoride, polyethylene, polypropylene, polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polymers containing ethylene oxide, polyvinyl pyrrolidone, and polyurethane.

[0079] Furthermore, in a specific embodiment of the present invention, the secondary battery includes a separator, and a deoxygenating material layer is disposed on at least one surface of the separator, and the deoxygenating material layer includes a deoxygenating material.

[0080] Wherein, a deoxidizing material layer including deoxidizing material is provided on one side surface or both side surfaces of the diaphragm.

[0081] The present invention does not limit the preparation method of the deoxygenation material layer on the surface of the diaphragm, and the deoxygenation material layer can be prepared by a common method in the art.

[0082] In a specific embodiment, a slurry including deoxidizing material is coated on the surface of the diaphragm, and the deoxidizing material layer is obtained after treatment such as drying.

[0083] It is understandable that the slurry also needs to include a binder so that the deoxidizing material can be better covered on the surface of the diaphragm. The present invention does not limit the specific type of the binder, and can select a binder commonly used in the field of secondary batteries, such as polytetrafluoroethylene, polyvinylidene fluoride, polyvinyl fluoride, polyethylene, polypropylene, polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polymers containing ethylene oxide, polyvinyl pyrrolidone, and polyurethane.

[0084] The present invention does not strictly limit the material selection of the diaphragm, which can be a diaphragm material commonly used in secondary batteries, such as a polypropylene diaphragm (PP), a polyethylene diaphragm (PE), a polypropylene / polyethylene double-layer composite film (PP / PE), a polyimide electrospinning diaphragm (PI), a polypropylene / polyethylene / polypropylene three-layer composite film (PP / PE / PP), a cellulose non-woven fabric diaphragm, or a diaphragm with a ceramic coating.

[0085] The deoxygenation material layer arranged on the surface of the diaphragm can further play the role of deoxygenation, thereby ensuring the safety performance of the battery.

[0086] Furthermore, in a specific embodiment of the present invention, the secondary battery includes a solid electrolyte layer, and the solid electrolyte layer includes an oxygen scavenging material.

[0087] It can be understood that a secondary battery including a solid electrolyte layer is a solid-state battery.

[0088] When preparing the solid electrolyte layer, the deoxygenating material and other components of the solid electrolyte layer may be mixed into a slurry, and after drying, the solid electrolyte layer including the deoxygenating material may be obtained.

[0089] Other components of the solid electrolyte layer can be selected from common solid electrolyte layer compositions, such as at least one of lithium aluminum oxide, lithium titanium oxide, lithium magnesium titanium oxide, lithium phosphate, lithium aluminum phosphate, lithium vanadium phosphate, lithium aluminate, lithium aluminum fluoride, and lithium sodium fluoride.

[0090] The oxygen removal material in the solid electrolyte layer can effectively remove oxygen or active oxygen in a timely manner when oxygen or active oxygen contacts the solid electrolyte layer, thereby reducing the impact of oxygen on the safety performance of the battery.

[0091] Another aspect of the present invention provides an electrical device including the secondary battery as described above.

[0092] The present invention does not limit the specific types of electrical equipment, and may include electric vehicles, mobile phones, smart homes, robots, drones, electronic cigarettes, speakers, and any other equipment that requires batteries to power them.

[0093] The electrical equipment provided by the present invention comprises the above-mentioned battery, and thus has good electrochemical performance and cycle stability.

[0094] The secondary battery provided by the present invention is described in detail below through specific embodiments.

[0095] Unless otherwise specified, the reagents, materials and instruments used in the following examples are conventional reagents, conventional materials and conventional instruments in the art and can be obtained commercially. The reagents involved can also be synthesized by conventional methods in the art.

[0096] Example 1

[0097] The method for preparing a secondary battery provided in this embodiment comprises the following steps:

[0098] 1) NCM811, Se, and polyvinylidene fluoride were added to a mechanical fusion machine and operated at 4000 rpm in an Ar atmosphere for 20 min to prepare NCM811@Se with a D50 of 100 μm;

[0099] 2) The coated positive electrode active material NCM811@Se was mixed with conductive carbon black and PVDF in a weight ratio of 96%:2%:2% respectively, and a positive electrode slurry was obtained by dispersion. The slurry was coated on the aluminum foil current collector, and the positive electrode surface density was 4.12g / cm 3 Rolling is performed to prepare a positive electrode sheet;

[0100] 3) Artificial graphite, styrene diene rubber (SBR), sodium carboxymethyl cellulose and conductive carbon black are mixed in a weight ratio of 94%:3%:2%:1%, and the mixture is dispersed in water and mixed by double planetary mixing to obtain a negative electrode slurry. The slurry is coated on a copper current collector, followed by roll pressing and drying to obtain a negative electrode sheet;

[0101] 4) Assemble the positive electrode sheet, the negative electrode sheet and the separator into a lithium-ion battery, and inject a non-aqueous electrolyte. The electrolyte is mixed in a mass ratio of ethylene carbonate (abbreviated as EC): diethyl carbonate (abbreviated as DEC): propylene carbonate (abbreviated as PC) = 2:5:3, and then add 5% of the total mass of the electrolyte fluoroethylene carbonate (abbreviated as FEC) and 13% of the total mass of the electrolyte lithium hexafluorophosphate.

[0102] The mass content of Se in NCM811 is 2%, and the mass ratio of the deoxidizing material Se to the binder PVDF is 99:1.

[0103] Example 2

[0104] The method for preparing a secondary battery provided in this embodiment comprises the following steps:

[0105] 1) A deoxidizing material layer is coated on both sides of the aluminum foil; the deoxidizing material layer comprises 99% of Se with a particle size D50 of 100 μm and 1% of polyvinylidene fluoride.

[0106] 2) The positive electrode active material NCM811 is mixed with conductive carbon black and PVDF in a weight ratio of 96%:2%:2% respectively, and the positive electrode slurry is obtained by dispersion. The slurry is coated on the surface of the deoxidizing material layer, and the positive electrode surface density is 4.12g / cm 3 Rolling is performed to prepare a positive electrode sheet;

[0107] 3) Artificial graphite, styrene diene rubber (SBR), sodium carboxymethyl cellulose and conductive carbon black are mixed in a weight ratio of 94%:3%:2%:1%, and the mixture is dispersed in water and mixed by double planetary mixing to obtain a negative electrode slurry. The slurry is coated on a copper current collector, followed by roll pressing and drying to obtain a negative electrode sheet;

[0108] 4) Assemble the positive electrode sheet, the negative electrode sheet and the separator into a lithium-ion battery, and inject a non-aqueous electrolyte. The electrolyte is mixed in a mass ratio of ethylene carbonate (abbreviated as EC): diethyl carbonate (abbreviated as DEC): propylene carbonate (abbreviated as PC) = 2:5:3, and then add 5% of the total mass of the electrolyte fluoroethylene carbonate (abbreviated as FEC) and 13% of the total mass of the electrolyte lithium hexafluorophosphate.

[0109] The mass content of the oxygen scavenging material is 2 wt % based on the mass of the positive electrode active material in the secondary battery.

[0110] Example 3

[0111] The method for preparing a secondary battery provided in this embodiment comprises the following steps:

[0112] 1) The positive electrode active material NCM811 was mixed with conductive carbon black, PVDF, and Se in a weight ratio of 94%: 2%: 2.12%: 1.88% respectively, and the positive electrode slurry was obtained by dispersion. The slurry was coated on the surface of aluminum foil, and the positive electrode surface density was 4.12g / cm 3 Roll-pressing is performed to prepare a positive electrode sheet;

[0113] 3) Artificial graphite, styrene diene rubber (SBR), sodium carboxymethyl cellulose and conductive carbon black are mixed in a weight ratio of 94%:3%:2%:1%, and the mixture is dispersed in water and mixed by double planetary mixing to obtain a negative electrode slurry. The slurry is coated on a copper current collector, followed by roll pressing and drying to obtain a negative electrode sheet;

[0114] 4) Assemble the positive electrode sheet, the negative electrode sheet and the separator into a lithium-ion battery, and inject a non-aqueous electrolyte. The electrolyte is mixed in a mass ratio of ethylene carbonate (abbreviated as EC): diethyl carbonate (abbreviated as DEC): propylene carbonate (abbreviated as PC) = 2:5:3, and then add 5% of the total mass of the electrolyte fluoroethylene carbonate (abbreviated as FEC) and 13% of the total mass of the electrolyte lithium hexafluorophosphate.

[0115] The mass content of the oxygen scavenging material Se is 2 wt % based on the mass of the positive electrode active material in the secondary battery.

[0116] Example 4

[0117] The method for preparing a secondary battery provided in this embodiment comprises the following steps:

[0118] 1) The positive electrode active material NCM811 was mixed with conductive carbon black and PVDF in a weight ratio of 96%:2%:2% respectively, and the positive electrode slurry was obtained by dispersion. The slurry was coated on the surface of aluminum foil with a positive electrode surface density of 4.12g / cm 3 Roll-pressing is performed to prepare a positive electrode sheet;

[0119] 2) Artificial graphite, styrene diene rubber (SBR), sodium carboxymethyl cellulose and conductive carbon black are mixed in a weight ratio of 94%:3%:2%:1%, and the mixture is dispersed in water and mixed by double planetary mixing to obtain a negative electrode slurry. The slurry is coated on a copper current collector, followed by roll pressing and drying to obtain a negative electrode sheet;

[0120] 3) coating a deoxygenation material layer on the surface of the diaphragm, wherein the deoxygenation material layer comprises 99% of Se with a particle size D50 of 100 μm and 1% of polyvinylidene fluoride;

[0121] 4) Assemble the positive electrode sheet, the negative electrode sheet and the separator into a lithium-ion battery, and inject a non-aqueous electrolyte. The electrolyte is mixed in a mass ratio of ethylene carbonate (abbreviated as EC): diethyl carbonate (abbreviated as DEC): propylene carbonate (abbreviated as PC) = 2:5:3, and then add 5% of the total mass of the electrolyte fluoroethylene carbonate (abbreviated as FEC) and 13% of the total mass of the electrolyte lithium hexafluorophosphate.

[0122] The mass content of the oxygen scavenging material Se is 2 wt % based on the mass of the positive electrode active material in the secondary battery.

[0123] Example 5

[0124] The preparation method of the secondary battery provided in this embodiment is basically the same as that in embodiment 2, except that:

[0125] In step 1), selenium is replaced by activated carbon.

[0126] Example 6

[0127] The preparation method of the secondary battery provided in this embodiment is basically the same as that in embodiment 2, except that:

[0128] In step 1), selenium is replaced by the catalyst Cu / TiO2.

[0129] Example 7

[0130] The preparation method of the secondary battery provided in this embodiment is basically the same as that in embodiment 2, except that:

[0131] In step 1), selenium is replaced by the perovskite oxygen storage material CaTiO3.

[0132] Example 8

[0133] The preparation method of the secondary battery provided in this embodiment is basically the same as that in embodiment 2, except that:

[0134] In step 1), the mass content of the oxygen scavenging material Se is 2.5 wt % based on the mass of the positive electrode active material.

[0135] Example 9

[0136] The preparation method of the secondary battery provided in this embodiment is basically the same as that in embodiment 2, except that:

[0137] In step 1), the particle size D50 of the deoxidizing material is 110 μm.

[0138] Example 10

[0139] The preparation method of the secondary battery provided in this embodiment is basically the same as that in embodiment 3, except that:

[0140] In step 1), the mass content of the deoxygenating material in the deoxygenating material layer is 90 wt.%.

[0141] Embodiment 11

[0142] The method for preparing a secondary battery provided in this embodiment comprises the following steps:

[0143] 1) The positive electrode active material NCM811 was mixed with conductive carbon black and PVDF in a weight ratio of 96%:2%:2% respectively, and the positive electrode slurry was obtained by dispersion. The slurry was coated on the surface of aluminum foil with a positive electrode surface density of 4.12g / cm 3 Roll-pressing is performed to prepare a positive electrode sheet;

[0144] 2) Se with a D50 of 100 microns and polyvinylidene fluoride are mixed in a mass ratio of 99:1 to obtain a slurry, and the slurry is coated on the surface of the copper current collector to obtain a deoxidizing material layer, and then artificial graphite, styrene diene rubber (SBR), sodium carboxymethyl cellulose, and conductive carbon black are mixed in a weight ratio of 94%:3%:2%:1%, and the mixture is dispersed in water and mixed by double planetary mixing to obtain a negative electrode slurry. The slurry is coated on the surface of the deoxidizing material layer, followed by rolling and drying to obtain a negative electrode sheet;

[0145] 3) Assemble the positive electrode sheet, the negative electrode sheet and the separator into a lithium-ion battery, and inject a non-aqueous electrolyte. The electrolyte is mixed in a mass ratio of ethylene carbonate (abbreviated as EC): diethyl carbonate (abbreviated as DEC): propylene carbonate (abbreviated as PC) = 2:5:3, and then add 5% of the total mass of the electrolyte fluoroethylene carbonate (abbreviated as FEC) and 13% of the total mass of the electrolyte lithium hexafluorophosphate.

[0146] The mass content of the oxygen scavenging material Se is 2 wt % based on the mass of the positive electrode active material in the secondary battery.

[0147] Example 12

[0148] The method for preparing a secondary battery provided in this embodiment comprises the following steps:

[0149] 1) NCM811, Se, and polyvinylidene fluoride were added to a mechanical fusion machine and operated at 4000 rpm in an Ar atmosphere for 20 min to prepare NCM811@Se with a D50 of 100 μm;

[0150] 2) The coated positive electrode active material NCM811@Se was mixed with conductive carbon black and PVDF in a weight ratio of 96%:2%:2% respectively, and a positive electrode slurry was obtained by dispersion. The slurry was coated on the aluminum foil current collector, and the positive electrode surface density was 4.12g / cm 3Roll-pressing is performed to prepare a positive electrode sheet;

[0151] 3) Weigh 8:1 (0.44 g: 0.36 g) of PEO: LiTFSI (lithium bistrifluoromethanesulfonyl imide), add 6 ml of acetonitrile, heat and stir at 60°C for 4 hours to obtain a PEO-based solid electrolyte, pour the PEO-based solid electrolyte on the positive electrode sheet with LiPF6 solution evenly distributed, put non-woven fabric in the electrolyte middle layer to prevent short circuit, then heat the positive electrode sheet-lithium salt-electrolyte at 60°C for 12 hours, remove the acetonitrile solvent, and then cover the negative electrode sheet to finally assemble into a solid-state battery.

[0152] The mass content of Se in NCM811 is 2%, and the mass ratio of the deoxidizing material Se to the binder PVDF is 99:1.

[0153] Comparative Example 1

[0154] The preparation method of the secondary battery provided in this comparative example is basically the same as that in Example 1, except that:

[0155] In step 1), the NCM811@Se material is replaced by NCM811.

[0156] Comparative Example 2

[0157] The preparation method of the secondary battery provided in this comparative example is basically the same as that in Example 2, except that:

[0158] In step 1), selenium is replaced by a common reducing agent Na2O4S2.

[0159] Test Case

[0160] 1. Test of VC content in electrolyte

[0161] The secondary batteries provided in all the embodiments and comparative examples were disassembled after 500 cycles at 2.8-4.25V and 1C rate, and the VC content in the batteries was analyzed by GCMS. Nine samples were taken from each battery, and the specific test results are shown in Table 1.

[0162] 2. DEMS gas production test

[0163] The secondary batteries provided in all the embodiments and comparative examples were cycled at 2.8-4.6V and 0.05C, and the oxygen generation in one cycle was monitored by in-situ DEMS, wherein: Figure 4These are the test curves of Example 1, Example 2 and Comparative Example 1. Under high voltage, the oxygen in the positive electrode active material is more easily excited and precipitated to form oxygen gas. According to the experimental results, there is almost no oxygen precipitation in Example 1, relatively less in Example 2, and more precipitation in Comparative Example 1. The inhibitory effect on active oxygen is: Se-coated positive electrode active material > Se-coated current collector treatment > original battery, which is consistent with the results of the VC test.

[0164] 3.DSC thermal stability test

[0165] The secondary batteries provided in all the embodiments and comparative examples were charged at a rate of 1C, with a cut-off voltage of 4.25V. After being fully charged, the positive electrode sheets were disassembled and thermal stability tests were performed using DSC in a N2 atmosphere at a temperature range of 50-350°C and a temperature rise rate of 10°C / min. Figure 5 The heat flow-temperature curves of the secondary batteries provided for Example 1 and Comparative Example 1 show that the oxygen release temperature of the positive electrode sheet treated with Se at high temperature is significantly increased, and the heat release is significantly reduced, indicating that its thermal stability is improved, which is attributed to the inhibitory effect of Se on the generation of active oxygen.

[0166] Table 1

[0167] Serial number VC content% Oxygen Oxygen release temperature ℃ Heat mW / g Example 1 1.69 0.26 200 500 Example 2 0.21 0.30 195 525 Example 3 0.13 0.28 197 516 Example 4 0.11 0.32 192 528 Example 5 0.04 4.31 183 590 Example 6 0.02 5.85 181 620 Example 7 0.03 4.57 182 604 Example 8 1.80 0.18 205 495 Example 9 0.11 0.81 189 574 Example 10 0.10 1.29 188 579 Embodiment 11 1.44 0.29 194 504 Example 12 1.28 0.27 195 510 Comparative Example 1 0 22 170 700 Comparative Example 2 0 12 175 682

[0168] In summary, the secondary battery provided by the present invention can effectively capture active oxygen and oxygen generated in the battery, prevent the generation of oxygen, avoid thermal runaway of the battery, and effectively improve battery safety. In addition, the reduced oxidation and expansion force of the electrolyte can also effectively improve battery performance.

[0169] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A secondary battery, characterized in that: The secondary battery includes an oxygen scavenging material, and the oxygen scavenging material includes one or more of selenium, activated carbon, a catalyst, and a perovskite oxygen storage material; the catalyst includes Pt, Pd, Ag, Ce, 1-x Cu x O 2-x At least one of , x is 0-1.

2. The secondary battery according to claim 1, characterized in that: The oxygen scavenging material includes selenium.

3. The secondary battery according to claim 1 or 2, characterized in that: The mass content of the oxygen scavenging material is 0.5 wt % to 2 wt % based on the mass of the positive electrode active material in the secondary battery.

4. The secondary battery according to any one of claims 1 to 3, characterized in that: The particle size D50 of the deoxidizing material is ≤100 μm.

5. The secondary battery according to any one of claims 1 to 4, characterized in that: The secondary battery comprises an electrode sheet, wherein the electrode sheet comprises a current collector and an active material layer; The active material layer includes an active material and an oxygen scavenging material; And / or, a deoxygenating material layer is disposed on at least one surface of the current collector and / or the active material layer, and the deoxygenating material layer includes the deoxygenating material.

6. The secondary battery according to claim 5, characterized in that: The active material is a positive electrode active material, and the deoxidizing material is coated on the surface of the positive electrode active material.

7. The secondary battery according to claim 5, characterized in that: The deoxidizing material layer also includes a binder; Preferably, the deoxidizing material layer comprises 97-99% of deoxidizing material and 1-3% of binder by mass.

8. The secondary battery according to any one of claims 1 to 7, characterized in that: The secondary battery comprises a separator, at least one surface of which is provided with an oxygen scavenging material layer, wherein the oxygen scavenging material layer comprises the oxygen scavenging material.

9. The secondary battery according to any one of claims 1 to 7, characterized in that: The secondary battery includes a solid electrolyte layer including the oxygen scavenging material.

10. An electrical device, characterized in that: A secondary battery comprising any one of claims 1 to 9.

Images