Electrolyte, battery and electric equipment

Abstract

The invention discloses an electrolyte, a battery and electric equipment, the electrolyte comprises AxOyZ-and PO2F2-, A comprises at least one of P, S or Si, x is more than or equal to 1 and less than or equal to 2, y is more than or equal to 4 and less than or equal to 5, and z is more than or equal to 2 and less than or equal to 3, based on the total mass of the electrolyte, the mass concentration m of the AxOyZ-is 1ppm-1000ppm, and the mass concentration n of the PO2F2-is 1ppm-1000ppm. The electrolyte provided by the invention can effectively reduce the DCR growth rate of the battery containing the electrolyte in the cyclic charging and discharging process, so that the power performance of the lithium ion battery can be improved.

Description

[0001] This application is a divisional application with application number 202310846470.9, application date July 11, 2023, and invention name “Electrolyte, battery and electrical equipment”. Technical Field

[0002] The present application belongs to the technical field of secondary batteries, and specifically relates to an electrolyte, a battery and an electrical device. Background Art

[0003] Lithium-ion batteries are not only used in energy storage power systems such as hydropower, thermal, wind and solar power stations, but are also widely used in electric transportation vehicles such as electric bicycles, electric motorcycles, electric cars, as well as in military equipment, aerospace and other fields.

[0004] With continuous charge and discharge cycles, the DCR (direct current internal resistance) of existing lithium-ion batteries will continue to increase, thereby affecting the power performance of the battery. Summary of the invention

[0005] In view of the technical problems existing in the background technology, the present application provides an electrolyte, aiming to reduce the DCR growth rate of a lithium-ion battery containing the electrolyte during the cyclic charge and discharge process, thereby improving the power performance of the lithium-ion battery.

[0006] In order to achieve the above-mentioned object, the first aspect of the present application provides an electrolyte, wherein the electrolyte comprises: A x O y Z- and PO 2 F 2 - , A includes at least one of P, S or Si, 1≤x≤2, 4≤y≤5, 2≤z≤3, based on the total mass of the electrolyte, the A x O y Z- The mass concentration m is 1ppm-1000ppm, the PO 2 F 2 - The mass concentration n is 1ppm-1000ppm.

[0007] The electrolyte of the present invention can effectively reduce the DCR growth rate of the battery containing it during the charge and discharge cycle, thereby improving the power performance of the lithium-ion battery.

[0008] In some embodiments of the present application, the A x O y Z- Including PO 4 3- 、SO 4 2- or Si2 O 5 2- At least one of, optional, including PO 4 3- Therefore, the DCR growth rate of the lithium-ion battery containing it during the cyclic charge and discharge process can be reduced.

[0009] In some embodiments of the present application, based on the total mass of the electrolyte, the A x O y Z- and the PO 2 F 2 - The total mass concentration of is less than or equal to 2000 ppm, and can be selected to be less than or equal to 1500 ppm. Thus, the DCR growth rate of the lithium ion battery containing it during the cyclic charge and discharge process can be reduced.

[0010] In some embodiments of the present application, based on the total mass of the electrolyte, the A x O y Z- The mass concentration of PO is m, 2 F 2 - The mass concentration of is n, n / m=(10-1000): 1, and can be optionally (100-500): 1. Thus, the DCR growth rate of the lithium ion battery containing it during the cyclic charge and discharge process can be reduced.

[0011] In some embodiments of the present application, based on the total mass of the electrolyte, the A x O y Z- The mass concentration m of is 1ppm-200ppm. Thus, the DCR growth rate of the lithium ion battery containing it during the cyclic charge and discharge process can be reduced.

[0012] In some embodiments of the present application, based on the total mass of the electrolyte, the PO 2 F 2 - The mass concentration n of is 1ppm-200ppm. Thus, the DCR growth rate of the lithium-ion battery containing it during the cyclic charge and discharge process can be reduced.

[0013] In some embodiments of the present application, the electrolyte further comprises a film-forming additive, thereby reducing the DCR growth rate of the lithium-ion battery containing the film-forming additive during the cyclic charge and discharge process.

[0014] In some embodiments of the present application, based on the total mass of the electrolyte, the mass concentration of the film-forming additive is w, and (m+n) / w is 1:(10-100), and can be optionally 1:(20-80). Thus, the DCR growth rate of the lithium-ion battery containing it during the cyclic charge and discharge process can be reduced.

[0015] In some embodiments of the present application, the mass concentration w of the film-forming additive is 0.2%-0.5%, and can be optionally 0.25%-0.45%, thereby reducing the DCR growth rate of the lithium-ion battery containing the film-forming additive during the cyclic charge and discharge process.

[0016] In some embodiments of the present application, the film-forming additive includes at least one of tris(trimethylsilyl)phosphate, tris(trimethylsilyl)borate, and tris(trimethylsilyl)phosphite. Thus, the DCR growth rate of the lithium-ion battery containing the film-forming additive during the cyclic charge and discharge process can be reduced.

[0017] The second aspect of the present application provides a battery, which comprises the electrolyte described in the first aspect of the present application. Thus, the battery has excellent power performance.

[0018] In some embodiments of the present application, the battery includes a positive electrode plate, and the positive electrode active material of the positive electrode plate satisfies at least one of the following conditions:

[0019] The volume average particle size D of the positive electrode active material v 50 is 1μm-4μm, optional is 1μm-3μm;

[0020] The BET specific surface area of ​​the positive electrode active material is 1 m 2 / g-4m 2 / g, optional 1m 2 / g-3m 2 / g;

[0021] The compaction density of the positive electrode active material under a pressure of 300 MPa is 3.2 g / cm 3 -3.8g / cm 3 , optional 3.3g / cm 3 -3.6g / cm 3 .

[0022] In some embodiments of the present application, the battery includes a negative electrode plate, and the negative electrode active material of the negative electrode plate satisfies at least one of the following conditions:

[0023] The volume average particle size D of the negative electrode active material v 50 is 1μm-4μm, optional is 1μm-3μm;

[0024] The BET specific surface area of ​​the negative electrode active material is 1 m 2 / g-4m 2 / g, optional 1m 2 / g-3m 2 / g;

[0025] The compaction density of the negative electrode active material at a pressure of 300 MPa is 1.4 g / cm 3 -1.8g / cm 3 , optional 1.5g / cm 3 -1.7g / cm 3 .

[0026] A third aspect of the present application provides an electrical device, which includes the battery described in the second aspect.

[0027] Additional aspects and advantages of the present application will be given in part in the description below, and in part will become apparent from the description below, or will be learned through the practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Various other advantages and benefits will become apparent to those of ordinary skill in the art by reading the detailed description of the optional embodiments below. The accompanying drawings are only used for the purpose of illustrating the optional embodiments and are not to be considered as limiting the present application. Moreover, the same reference numerals are used throughout the drawings to represent the same components. In the drawings:

[0029] Figure 1 is a schematic structural diagram of a battery according to one embodiment of the present application;

[0030] Figure 2 is a schematic structural diagram of a battery module according to an embodiment of the present application;

[0031] Figure 3 is a schematic structural diagram of a battery pack according to an embodiment of the present application;

[0032] Figure 4 yes Figure 3 Exploded diagram of

[0033] Figure 5 It is a schematic diagram of an embodiment of an electric device in which a battery is used as a power source.

[0034] Description of reference numerals:

[0035] 1: Secondary battery; 2: Battery module; 3: Battery pack; 4: Upper case; 5: Lower case. DETAILED DESCRIPTION

[0036] The following is a detailed description of the embodiments of the technical solution of the present application. The following embodiments are only used to more clearly illustrate the technical solution of the present application, and are therefore only used as examples, and cannot be used to limit the scope of protection of the present application.

[0037] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0038] For simplicity, only some numerical ranges are specifically disclosed herein. However, any lower limit can be combined with any upper limit to form an unspecified range; and any lower limit can be combined with other lower limits to form an unspecified range, and any upper limit can be combined with any other upper limit to form an unspecified range. In addition, each separately disclosed point or single value can itself be combined as a lower limit or upper limit with any other point or single value or with other lower limits or upper limits to form an unspecified range.

[0039] In the description of the embodiments of the present application, the term "and / or" is only a description of the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in this article generally indicates that the associated objects before and after are in an "or" relationship.

[0040] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by technicians in the technical field to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" in the specification and claims of this application and the above-mentioned figure descriptions and any variations thereof are intended to cover non-exclusive inclusions.

[0041] At present, from the perspective of market development, the application of lithium-ion batteries is becoming more and more extensive. Lithium-ion batteries are not only used in energy storage power systems such as hydropower, thermal power, wind power and solar power stations, but also widely used in electric vehicles such as electric bicycles, electric motorcycles, electric cars, as well as military equipment and aerospace and other fields. With the continuous expansion of the application field of lithium-ion batteries, its market demand is also constantly expanding.

[0042] During the charge and discharge process of lithium-ion batteries, lithium ions are released from the positive electrode, migrate to the negative electrode through the electrolyte under the action of the electric field, and are embedded in the negative electrode active material; when the battery is discharged, lithium ions are released from the negative electrode active material, migrate to the positive electrode through the electrolyte under the action of the electric field, and are embedded in the positive electrode active material. With the charge and discharge cycle of the secondary battery, side reactions occur between the positive electrode and the electrolyte. On the one hand, the occurrence of side reactions is accompanied by the participation of active lithium in the reaction, which consumes active lithium. On the other hand, the accumulation of side reaction products on the surface of the positive active material makes it difficult for lithium ions to be transported, making it impossible for lithium ions to be fully embedded in the material, and finally leading to the continuous loss of active lithium in the positive active material, causing the DCR of the lithium-ion battery to continue to increase, thereby reducing the power performance of the battery.

[0043] In this application, the electrolyte includes A x O y Z- and PO 2 F 2 - , A includes at least one of P, S or Si, 1≤x≤2, 4≤y≤5, 2≤z≤3, on the one hand, A x O y Z- and PO 2 F 2 - It can provide AO bonds, A=O bonds, PO bonds and P=O bonds, which can combine with lithium ions on the surface of the positive electrode to stabilize the active lithium in the positive electrode. x O y Z- Since the central ligand of A has insufficient binding force on O, it is easy to lose electrons under high voltage, and after being oxidized, it can form a film on the surface of the positive electrode, thereby protecting the active lithium in the positive electrode. 2 F 2 - The P=O bond on the positive electrode is easily oxidized by the positive electrode active material after the lithium is removed from the positive electrode. After the P=O is oxidized, the remaining F ions are easily combined with lithium ions, thereby improving the A x O y Z- The problem of poor conductivity of the surface product ions after oxidation is solved. Since the radius of F ions and lithium ions is close, the binding energy is very strong, and they can be well covered on the surface of the positive electrode material, thereby reducing the loss of active lithium. Therefore, the electrolyte composed of the present application can effectively reduce the loss of active lithium, thereby reducing the DCR growth rate of the battery containing it during the cyclic charge and discharge process, and improving the power performance of the battery.

[0044] The electrolyte disclosed in the embodiments of the present application is suitable for lithium-ion batteries, and the battery disclosed in the embodiments of the present application can be used in electrical equipment that uses the battery as a power source or various energy storage systems that use the battery as an energy storage element. Electrical equipment may include, but is not limited to, mobile phones, tablets, laptops, electric toys, electric tools, battery cars, electric cars, ships, spacecraft, and the like. Among them, electric toys may include fixed or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, and the like, and spacecraft may include airplanes, rockets, space shuttles, and spacecraft, and the like.

[0045] In a first aspect, the present application provides an electrolyte, wherein the electrolyte comprises: A x O y Z- and PO 2 F 2 - , A includes at least one of P, S and Si, 1≤x≤2, 4≤y≤5, 2≤z≤3.

[0046] The present application at least includes the following beneficial effects: the electrolyte of the present application includes A x O y Z- and PO 2 F 2 - On the one hand, A x O y Z- and PO 2 F 2 - It can provide AO bonds, A=O bonds, PO bonds and P=O bonds, which can combine with lithium ions on the surface of the positive electrode to stabilize the active lithium in the positive electrode. x O y Z- Since the central ligand of A has insufficient binding force on O, it is easy to lose electrons under high voltage, and after being oxidized, it can form a film on the surface of the positive electrode, thereby protecting the active lithium in the positive electrode. 2 F 2 - The P=O bond on the positive electrode is easily oxidized by the positive electrode active material after the lithium is removed from the positive electrode. After the P=O is oxidized, the remaining F ions are easily combined with lithium ions, thereby improving the A x O y Z-The problem of poor conductivity of the surface product ions after oxidation is solved. Since the radius of F ions and lithium ions is close, the binding energy is very strong, and they can be well covered on the surface of the positive electrode material, thereby reducing the loss of active lithium. Therefore, the electrolyte composed of the present application can effectively reduce the loss of active lithium and reduce the DCR growth rate of the battery containing it during the cyclic charge and discharge process, thereby improving the power performance of the battery.

[0047] In some embodiments of the present application, the above A x O y Z- Where A may include at least one of P, S or Si, 1≤x≤2, 4≤y≤5, 2≤z≤3, for example, x is 1 or 2, y is 4 or 5, and z is 2 or 3. As an example, A x O y Z- Can include PO 4 3- 、SO 4 2- or Si 2 O 5 2- Thus, the above-mentioned composition A x O y Z- The AO bond and A=O bond provided can combine with the lithium ions on the surface of the positive electrode, thereby stabilizing the active lithium in the positive electrode; x O y Z- Since the central ligand of A has insufficient binding force on O, it is easy to lose electrons and be oxidized to form a film on the surface of the positive electrode, thereby protecting the active lithium in the positive electrode. x O y Z- Can include PO 4 3- .

[0048] It should be noted that in this application, A x O y Z- and PO 2 F 2 - Added to the electrolyte in the form of lithium salt, such as Li 3 PO 4 , Li 2 SO 4 , Li 2 Si 2 O 5 、LiPO 2 F 2 .

[0049] In some embodiments of the present application, based on the total mass of the electrolyte, the A x O y Z- and the PO 2 F 2 - The sum of the mass concentrations of is less than or equal to 2000ppm, for example, 2ppm-2000ppm, 10ppm-2000ppm, 50ppm-2000ppm, 100ppm-2000ppm, 200ppm-2000ppm, 300ppm-2000ppm, 400ppm-2000ppm, 500ppm-2000ppm, 600ppm-2000ppm, 700ppm-2000ppm, 800ppm-2000ppm, 900ppm-2000ppm, 1000ppm-2000ppm, 1100ppm-1900ppm, 1200ppm-1800ppm, 1300ppm-1700ppm, 1400ppm-1600ppm, 1400ppm-1500ppm, etc. Thus, the present application controls the A in the electrolyte. x O y Z- and PO 2 F 2 - The total mass concentration of A is controlled within the above range, which can not only improve the battery cycle life, but also reduce the DCR growth rate during the cyclic charge and discharge process of the lithium-ion battery, thereby improving the power performance of the lithium-ion battery. In other embodiments of the present application, based on the total mass of the electrolyte, the A x O y Z- and the PO 2 F 2 - The sum of the mass concentrations is less than or equal to 1500 ppm.

[0050] It should be noted that "ppm" refers to mass concentration, which refers to the A x O y Z- and PO 2 F 2 - The ratio of the total mass of to the mass of the electrolyte is 1ppm=0.0001%. x O y Z- and PO 2 F 2 -The test method for the mass concentration can be determined by instruments and methods known in the art, for example, it can be tested by ion chromatography, the instrument uses ICS-900 ion chromatograph, and the test method specifically refers to GB / T36240-2018.

[0051] In some embodiments of the present application, based on the total mass of the electrolyte, the A x O y Z- The mass concentration of PO is m, 2 F 2 - The mass concentration of n is n / m=(10-1000):1, for example (20-980):1, (30-950):1, (40-920):1, (50-900):1, (80-880):1, (100-850):1, (120-820):1, (150-800):1, (180-780):1, (200-750):1, (250-700):1, (300-650):1, (350-600):1, (400-550):1, (450-500):1, (480-500):1, etc. Therefore, the present application converts the PO in the electrolyte into 2 F 2 - The mass concentration n is related to the A x O y Z- The ratio n / m of the mass concentration m is controlled within the above range, which can reduce the gas production and reduce the DCR growth rate of the lithium-ion battery during the cyclic charge and discharge process, thereby improving the power performance and cycle performance of the lithium-ion battery. In other embodiments of the present application, based on the total mass of the electrolyte, the A x O y Z- The mass concentration m of the PO 2 F 2 - The mass concentration n satisfies n / m=(100-500):1.

[0052] In some embodiments of the present application, based on the total mass of the electrolyte, the A x O y Z-The mass concentration m is 1ppm-1000ppm, for example 2ppm-1000ppm, 5ppm-1000ppm, 10ppm-1000ppm, 50ppm-1000ppm, 80ppm-1000ppm, 100ppm-1000ppm, 120ppm-1000ppm, 150ppm-1000ppm, 170ppm-1000ppm, 200ppm-1000ppm, 300ppm-1000ppm, 400ppm-1000ppm, 500ppm-1000ppm, 600ppm-1000ppm, 700ppm-1000ppm, 800ppm-1000ppm, 900ppm-1000ppm. Thus, the present application controls the A in the electrolyte. x O y Z- The mass concentration of is within the above range, which can reduce the deterioration of gas production while reducing the DCR growth rate of the lithium-ion battery during the cyclic charge and discharge process, thereby improving the power performance and cycle performance of the lithium-ion battery. In other embodiments of the present application, based on the total amount of the electrolyte, the A x O y Z- The mass concentration m is 1ppm-200ppm.

[0053] In some embodiments of the present application, based on the total mass of the electrolyte, the PO 2 F 2 - The mass concentration n is 1ppm-1000ppm, for example, 2ppm-1000ppm, 5ppm-1000ppm, 10ppm-1000ppm, 50ppm-1000ppm, 80ppm-1000ppm, 100ppm-1000ppm, 120ppm-1000ppm, 150ppm-1000ppm, 170ppm-1000ppm, 200ppm-1000ppm, 300ppm-1000ppm, 400ppm-1000ppm, 500ppm-1000ppm, 600ppm-1000ppm, 700ppm-1000ppm, 800ppm-1000ppm, 900ppm-1000ppm. Thus, the present application controls the PO in the electrolyte. 2 F 2 - The mass concentration of is within the above range, which can reduce the DCR growth rate of the lithium-ion battery during the cyclic charge and discharge process, thereby improving the power performance of the lithium-ion battery. In other embodiments of the present application, based on the total mass of the electrolyte, the PO 2 F2 - The mass concentration n is 1ppm-200ppm.

[0054] In some embodiments of the present application, the electrolyte may further include a film-forming additive. Specifically, a "film-forming additive" may be understood as a substance added to the electrolyte that can promote the formation of a CEI film (positive electrode electrolyte interface) on the surface of the positive electrode plate and / or a SEI film (solid electrolyte interface film) on the surface of the negative electrode plate. The present application adds a film-forming additive to the electrolyte, and the film-forming additive is added to the electrolyte. x O y Z- and PO 2 F 2 - The synergy can promote film formation on the surface of the positive electrode, effectively reduce the loss of active lithium, thereby reducing the DCR growth rate of the battery containing it during the cyclic charge and discharge process and improving the power performance of the battery.

[0055] In some embodiments of the present application, based on the total mass of the electrolyte, the mass concentration of the film-forming additive is w, and (m+n) / w is 1:(10-100), for example, 1:(15-95), 1:(20-90), 1:(25-85), 1:(30-80), 1:(35-75), 1:(40-70), 1:(45-65), 1:(50-60), 1:(55-60), etc. Thus, the present application controls the A in the electrolyte. x O y Z- With the PO 2 F 2 - The mass concentration of and the mass concentration ratio of the film-forming additive are within the above range, which can reduce the DCR growth rate of the lithium-ion battery during the cyclic charge and discharge process, thereby improving the power performance of the lithium-ion battery. In other embodiments of the present application, the A x O y Z- The mass concentration m of the PO 2 F 2 - The mass concentration n and the mass concentration w of the film-forming additive satisfy (m+n) / w=1:(20-80).

[0056] In some embodiments of the present application, the mass concentration w of the film-forming additive is 0.2%-0.5%, such as 0.22%-0.48%, 0.25%-0.45%, 0.27%-0.42%, 0.3%-0.4%, 0.32%-0.38%, 0.35%-0.37%, etc. Therefore, the present application controls the mass concentration w of the film-forming additive in the electrolyte within the above range, which can reduce the DCR growth rate during the cyclic charge and discharge process of the lithium-ion battery, thereby improving the power performance of the lithium-ion battery. In other embodiments of the present application, the mass concentration w of the film-forming additive is 0.25%-0.45%.

[0057] It should be noted that the concentration of the film-forming additive in the electrolyte in the present application can be tested using instruments and methods known in the art, such as organic gas chromatography.

[0058] As an example, the film-forming additive may include at least one of tris(trimethylsilyl)phosphate, tris(trimethylsilyl)borate, or tris(trimethylsilyl)phosphite.

[0059] The electrolyte may further include an electrolyte salt and a solvent.

[0060] As an example, the electrolyte salt may include lithium hexafluorophosphate (LiPF 6 ), lithium tetrafluoroborate (LiBF 4 ), lithium perchlorate (LiClO 4 ) lithium hexafluoroarsenate (LiAsF 6 ), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalatoborate (LiDFOB), lithium dioxalatoborate (LiBOB), lithium difluorophosphate (LiPO 2 F 2 ), at least one of lithium difluorobis(oxalate) phosphate (LiDFOP) or lithium tetrafluorooxalate phosphate (LiTFOP).

[0061] As an example, the solvent may include at least one of ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butylene carbonate (BC), fluoroethylene carbonate (FEC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), ethyl methyl sulfone (EMS) or diethyl sulfone (ESE).

[0062] In some embodiments, the electrolyte may further include additives that can improve certain battery properties, such as additives that improve battery overcharge performance, additives that improve battery high temperature performance, and additives that improve battery low temperature performance.

[0063] The second aspect of the present application provides a battery, which includes the electrolyte described in the first aspect of the present application. Therefore, the battery has low DC internal resistance and excellent power performance.

[0064] A battery is a battery that can be used again by recharging the active materials after discharge.

[0065] Generally, a battery includes a positive electrode sheet, a negative electrode sheet, a separator and an electrolyte. During the charge and discharge process of the battery, active ions are embedded and released back and forth between the positive electrode sheet and the negative electrode sheet. The separator is arranged between the positive electrode sheet and the negative electrode sheet to play a role of isolation. The electrolyte plays a role of conducting ions between the positive electrode sheet and the negative electrode sheet.

[0066] In some embodiments of the present application, the battery may be a lithium-ion battery.

[0067] [Positive electrode]

[0068] In a battery, the positive electrode sheet generally includes a positive electrode current collector and a positive electrode active material layer disposed on the positive electrode current collector, wherein the positive electrode active material layer includes a positive electrode active material.

[0069] The positive electrode current collector may be a conventional metal foil or a composite current collector (a metal material may be disposed on a polymer substrate to form a composite current collector). As an example, the positive electrode current collector may be an aluminum foil.

[0070] The specific type of the positive electrode active material is not limited, and any active material known in the art that can be used for the positive electrode of a secondary battery can be used, and those skilled in the art can select it according to actual needs.

[0071] As an example, the positive electrode active material may include, but is not limited to, at least one of lithium transition metal oxides, lithium-containing phosphates of olivine structure and their respective modified compounds. Examples of lithium transition metal oxides may include, but are not limited to, at least one of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide and their modified compounds. Examples of lithium-containing phosphates of olivine structure may include, but are not limited to, at least one of lithium iron phosphate, a composite material of lithium iron phosphate and carbon, lithium manganese phosphate, a composite material of lithium manganese phosphate and carbon, lithium iron manganese phosphate, a composite material of lithium iron manganese phosphate and carbon and their modified compounds. These materials can all be obtained commercially.

[0072] In some embodiments of the present application, the volume average particle size D of the positive electrode active material is v 50 is 1 μm-4 μm, for example, the volume average particle size D of the positive electrode active material v 50 can be 1 μm-3 μm, 2 μm-3 μm, etc. In some other embodiments of the present application, the volume average particle size D of the positive electrode active material is v 50 is 1μm-3μm.

[0073] In this application, the volume average particle size D v 50 refers to the particle size corresponding to when the cumulative volume distribution percentage reaches 50%, for example, with reference to the standard GB / T 19077-2016, and measured using a laser particle size analyzer (such as Malvern Master Size 3000).

[0074] In some embodiments of the present application, the BET specific surface area of ​​the positive electrode active material is 1 m 2 / g-4m 2 / g, for example, the specific surface area of ​​the positive electrode active material can be 1.5m 2 / g-3.5m 2 / g,2m 2 / g-3m 2 / g, 2.5m 2 / g-3m 2 / g, 2.8m 2 / g-3m 2 In some other embodiments of the present application, the BET specific surface area of ​​the positive electrode active material is 1 m 2 / g-3m 2 / g.

[0075] In the present application, the specific surface area of ​​the positive electrode active material can be tested by referring to the following method: using the American Micromeritics multi-station fully automatic specific surface area and pore analyzer GeminiVII2390, take about 7g of the sample and put it into a 9cc long tube with a bulb, degas at 200℃ for 2h, and then put it into the main unit for testing to obtain the BET (specific surface area) data of the positive electrode active material.

[0076] In some embodiments of the present application, the compaction density of the positive electrode active material at a pressure of 300 MPa is 3.2 g / cm 3 -3.8g / cm 3 For example, the compaction density of the positive electrode active material at a pressure of 300 MPa can be 3.2 g / cm 3 -3.7g / cm 3 , 3.3g / cm 3 -3.6g / cm 3 , 3.4g / cm 3 -3.5g / cm 3 In some embodiments of the present application, the compaction density of the positive electrode active material at a pressure of 300 MPa is 3.3 g / cm 3 -3.6g / cm 3 .

[0077] In the present application, "compacted density" has a well-known meaning in the art and can be measured by instruments and methods well-known in the art. For example, the following test method can be used: a certain amount of powder m is placed in a special compaction mold, the mold is placed on a compaction density instrument, a pressure of 300 MPa is set, and the volume v of the powder under a pressure of 300 MPa is measured on the equipment. The compacted density is calculated by density = mass m / volume v (specific reference GB / T24533-2009).

[0078] Specifically, when the volume average particle size D of the positive electrode active material of the present application is v 50. When at least one of the specific surface area and the compaction density under a pressure of 300 MPa is within the above range, the conduction distance in the positive electrode active material is small and the surface side reactions are small, which promotes the positive electrode active material to exert its gram capacity and improves the capacity retention rate of the battery containing it.

[0079] [Negative electrode]

[0080] In a battery, the negative electrode plate generally includes a negative electrode current collector and a negative electrode active material layer disposed on the negative electrode current collector, wherein the negative electrode active material layer includes a negative electrode active material.

[0081] The negative electrode current collector may be a conventional metal foil or a composite current collector (for example, a metal material may be disposed on a polymer substrate to form a composite current collector). As an example, the negative electrode current collector may be a copper foil.

[0082] The specific type of the negative electrode active material is not limited, and active materials known in the art that can be used for the negative electrode of a secondary battery can be used, and those skilled in the art can choose according to actual needs. As an example, the negative electrode active material may include but is not limited to at least one of artificial graphite, natural graphite, hard carbon, soft carbon, silicon-based materials and tin-based materials. The silicon-based material may include at least one of elemental silicon, silicon oxide compounds (such as silicon monoxide), silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material may include at least one of elemental tin, tin oxide compounds, and tin alloys. These materials can all be obtained commercially.

[0083] In some embodiments, in order to further improve the energy density of the battery, the negative electrode active material may include a silicon-based material.

[0084] In some embodiments of the present application, the volume average particle size D of the negative electrode active material is v 50 is 1 μm-4 μm, for example, the volume average particle size D of the negative electrode active material v 50 can be 1 μm-3 μm, 2 μm-3 μm, etc. In some other embodiments of the present application, the volume average particle size D of the negative electrode active material is v 50 is 1μm-3μm.

[0085] In the present application, the volume average particle size D of the negative electrode active material v The meaning and test method of 50 can refer to the volume average particle size D of the positive electrode active material. v The meaning and testing method of 50.

[0086] In some embodiments of the present application, the BET specific surface area of ​​the negative electrode active material is 1 m 2 / g-4m 2 / g, for example, the specific surface area of ​​the negative electrode active material can be 1.5m 2 / g-3.5m 2 / g,2m 2 / g-3m 2 / g, 2.5m 2 / g-3m 2 / g, 2.8m 2 / g-3m 2 In some other embodiments of the present application, the BET specific surface area of ​​the negative electrode active material is 1 m 2 / g-3m 2 / g.

[0087] In the present application, the test method of the BET specific surface area of ​​the negative electrode active material can refer to the test method of the BET specific surface area of ​​the positive electrode active material.

[0088] In some embodiments of the present application, the compaction density of the negative electrode plate is 1.4 g / cm 3 -1.8g / cm 3 , for example 1.4 g / cm 3 -1.7g / cm 3 , 1.5g / cm 3 -1.7g / cm 3 , 1.6g / cm 3 -1.7g / cm 3 In some other embodiments of the present application, the compaction density of the negative electrode sheet is 1.5 g / cm 3 -1.7g / cm 3 Thus, the cycle performance of the battery containing it can be improved.

[0089] The "compacted density of the negative electrode sheet" in this application has a well-known meaning in the art and can be measured using instruments and methods known in the art. For example, the test method can refer to the test method of the "compacted density of the positive electrode sheet" mentioned above. It is worth noting that the negative electrode is usually wiped with deionized water to remove the active material layer.

[0090] The negative electrode active material layer may also optionally include a binder, a conductive agent and other optional auxiliary agents.

[0091] As an example, the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0092] As an example, the binder may include at least one of styrene butadiene rubber (SBR), water-based acrylic resin, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), ethylene-vinyl acetate copolymer (EVA), polyvinyl alcohol (PVA), and polyvinyl butyral (PVB).

[0093] As examples, other optional additives may include thickening and dispersing agents (eg, sodium carboxymethylcellulose CMC-Na), and PTC thermistor materials.

[0094] As the above-mentioned isolation membrane, the present application has no special restrictions and any known porous structure isolation membrane with electrochemical stability and mechanical stability can be selected according to actual needs. For example, it can include a single-layer or multi-layer film containing at least one of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride.

[0095] The embodiment of the present application has no particular limitation on the shape of the battery, which can be cylindrical, square or any other shape. Figure 1 The secondary battery 1 is a square structure as an example.

[0096] In some embodiments, the battery may include an outer packaging for packaging the positive electrode sheet, the negative electrode sheet, and the electrolyte.

[0097] In some embodiments, the outer package may include a shell and a cover plate. The shell may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity. The shell has an opening connected to the receiving cavity, and the cover plate can be covered on the opening to close the receiving cavity.

[0098] The positive electrode sheet, the negative electrode sheet and the separator can be wound or laminated to form an electrode assembly. The electrode assembly is packaged in the receiving cavity. The number of electrode assemblies contained in the battery can include one or more, which can be adjusted according to demand.

[0099] In some embodiments, the outer packaging of the battery may include a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell.

[0100] The outer packaging of the battery may also include a soft package, such as a bag-type soft package. The material of the soft package may be plastic, such as at least one of polypropylene (PP), polybutylene terephthalate (PBT), and polybutylene succinate (PBS).

[0101] In some embodiments, the batteries may be assembled into a battery module. The battery module may contain multiple batteries, and the specific number may be adjusted according to the application and capacity of the battery module.

[0102] Figure 2 2 is an example of a battery module 2. Figure 2 In the battery module 2, the plurality of secondary batteries 1 may be arranged in sequence along the length direction of the battery module 2. Of course, they may also be arranged in any other manner. Further, the plurality of secondary batteries 1 may be fixed by fasteners.

[0103] The battery module 2 may further include a housing having a housing space, in which a plurality of secondary batteries 1 are housed. In some embodiments, the battery modules may be assembled into a battery pack, and the number of battery modules contained in the battery pack may be adjusted according to the application and capacity of the battery pack.

[0104] Figure 3 and 4 The battery pack 3 is used as an example. Figure 3 and 4The battery pack 3 may include a battery box and a plurality of battery modules 2 disposed in the battery box. The battery box includes an upper box body 4 and a lower box body 5. The upper box body 4 can cover the lower box body 5 and form a closed space for accommodating the battery modules 2. The plurality of battery modules 2 can be arranged in the battery box in any manner.

[0105] The third aspect of the present application provides an electrical device, which includes the battery described in the second aspect. Specifically, the battery can be used as a power source for the electrical device, and can also be used as an energy storage unit for the electrical device. The electrical device may include, but is not limited to, mobile devices (such as mobile phones, laptops), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks), electric trains, ships and satellites, and energy storage systems.

[0106] Figure 5 The electrical equipment is used as an example, and the electrical equipment includes a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle.

[0107] As another example, the electric device may include a mobile phone, a tablet computer, and a notebook computer. The electric device is usually required to be thin and light, and a battery may be used as a power source.

[0108] In order to make the technical problems, technical solutions and beneficial effects solved by the embodiments of the present application clearer, the following will be further described in detail with reference to the embodiments and the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all of the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is by no means intended to limit the present application and its applications. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without creative work are within the scope of protection of the present application.

[0109] Example 1

[0110] 1. Preparation of positive electrode sheet

[0111] The positive electrode active material LiNi 0.7 Co 0.1 Mn 0.1 O 2 , conductive agent Super P, and binder polyvinylidene fluoride (PVDF) are used to prepare positive electrode slurry in N-methylpyrrolidone (NMP), wherein the solid content in the positive electrode slurry is 50wt%, and the solid content of LiNi 0.7 Co 0.1 Mn 0.1 O 2The mass ratio of Super P and PVDF is 8:1:1. The positive electrode slurry is coated on the upper and lower surfaces of the current collector aluminum foil and dried at 85°C and then cold pressed. Then, it is trimmed, cut into pieces, and stripped, and then dried at 85°C under vacuum conditions for 4 hours to make the positive electrode sheet.

[0112] 3. Preparation of negative electrode sheet

[0113] Graphite, conductive agent Super P, thickener carboxymethyl cellulose (CMC), and adhesive styrene butadiene rubber (SBR) are mixed evenly in deionized water to prepare a negative electrode slurry, wherein the solid content in the negative electrode slurry is 30wt%, and the mass ratio of graphite, silicon oxide, Super P, CMC and adhesive styrene butadiene rubber (SBR) in the solid component is 88:7:3:2. The negative electrode slurry is coated on the upper and lower surfaces of the current collector copper foil and dried at 85°C, and then cold pressed, trimmed, cut into pieces, and slit, and then dried at 120°C under vacuum conditions for 12 hours to prepare a negative electrode sheet.

[0114] 3. Preparation of electrolyte

[0115] In a glove box filled with argon (water content <10 ppm, oxygen content <1 ppm), Li z A x O y and LiPO 2 F 2 Add to the organic solvent (the organic solvent includes ethylene carbonate (EC) and ethyl methyl carbonate (EMC), the mass ratio of EC to EMC is 3:7), mix well, and then slowly add LiPF 6 and LiFSI, and after the lithium salt is completely dissolved, an electrolyte with a lithium salt concentration of 1 mol / L is obtained.

[0116] 4. Isolation film

[0117] A 16 μm polyethylene film was used as the separator.

[0118] 5. Lithium-ion battery preparation

[0119] The positive electrode sheet, the separator, and the negative electrode sheet are stacked in order, so that the separator is in the middle of the positive and negative electrode sheets to isolate the positive and negative electrodes, and the bare battery cell is wound and welded. The tabs are placed in the outer packaging, and the prepared electrolyte is injected into the dried battery cell. The battery cell is packaged, allowed to stand, formed, shaped, and tested for capacity to complete the preparation of the lithium-ion battery (the soft-pack lithium-ion battery has a thickness of 4.0 mm, a width of 60 mm, and a length of 140 mm).

[0120] The preparation methods of the lithium ion batteries of Examples 2-39 and Comparative Examples 1-4 are the same as that of Example 1, except that the composition of the additives in the electrolyte is different, as shown in Table 1.

[0121]

[0122]

[0123] The DCR growth rates of the lithium-ion batteries obtained in Examples 1-39 and Comparative Examples 1-4 were characterized, and the characterization results are shown in Table 2.

[0124] Lithium-ion battery DCR growth rate test method

[0125] Before the battery starts cycling, adjust the SOC to 50%. Then discharge at 4C for 30S. The voltage before discharge is recorded as V1, and the voltage after discharge is recorded as V2. Calculate DCR 1 =(V1-V2) / I (where I corresponds to the current value of 4C discharge). After 300 cycles, remove the battery. Test DCR with the same scheme. 2 , calculate ΔDCR = (DCR 2 -DCR 1 ) / DCR 1 , ΔDCR is the growth rate of battery DCR.

[0126] Table 2

[0127]

[0128]

[0129] As shown in Table 2, the DCR growth rate of the lithium-ion batteries of Examples 1-39 is significantly lower than that of Comparative Examples 1-4, which indicates that the lithium-ion batteries of the present application including A x O y Z- and PO 2 F 2 - The electrolyte can effectively reduce the DCR growth rate of the battery containing it during the cyclic charge and discharge process, thereby improving the power performance of the lithium-ion battery.

[0130] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them; although the present application 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 by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application, and they should all be included in the scope of the claims and specification of the present application. In particular, as long as there is no structural conflict, the various technical features mentioned in the various embodiments can be combined in any way. The present application is not limited to the specific embodiments disclosed herein, but includes all technical solutions that fall within the scope of the claims.

Claims

1. An electrolyte, characterized in that: include: A x O y Z- and PO2F2 - , A includes at least one of P, S or Si, 1≤x≤2, 4≤y≤5, 2≤z≤3, Based on the total mass of the electrolyte, the A x O y Z- The mass concentration m is 1ppm-1000ppm, the PO2F2 - The mass concentration n is 1ppm-1000ppm.

2. The electrolyte according to claim 1, characterized in that The A x O y Z- Including PO4 3- 、SO4 2- or Si2O5 2- At least one of .

3. The electrolyte according to claim 1 or 2, characterized in that The A x O y Z- Including PO4 3- .

4. The electrolyte according to any one of claims 1 to 3, characterized in that Based on the total mass of the electrolyte, the A x O y Z- The mass concentration m and the PO2F2 - The total mass concentration n is less than or equal to 2000 ppm.

5. The electrolyte according to any one of claims 1 to 4, characterized in that Based on the total mass of the electrolyte, the A x O y Z- The mass concentration m and the PO2F2 - The total mass concentration n is less than or equal to 1500 ppm.

6. The electrolyte according to any one of claims 1 to 5, characterized in that n / m=(10-1000):

1.

7. The electrolyte according to any one of claims 1 to 6, characterized in that n / m=(100-500):

1.

8. The electrolyte according to any one of claims 1 to 7, characterized in that The A x O y Z- The mass concentration m is 1ppm-200ppm.

9. The electrolyte according to any one of claims 1 to 8, characterized in that The PO2F2 - The mass concentration n is 1ppm-200ppm.

10. The electrolyte according to any one of claims 1 to 9, characterized in that Also included are film-forming additives.

11. The electrolyte according to claim 10, characterized in that Based on the total mass of the electrolyte, the mass concentration of the film-forming additive is w, and (m+n) / w is 1:(10-100).

12. The electrolyte according to claim 11, characterized in that (m+n) / w is 1:(20-80).

13. The electrolyte according to claim 11 or 12, characterized in that: The mass concentration w of the film-forming additive is 0.2%-0.5%.

14. The electrolyte according to any one of claims 11 to 13, characterized in that The mass concentration w of the film-forming additive is 0.25%-0.45%.

15. The electrolyte according to any one of claims 10 to 14, characterized in that: The film-forming additive includes at least one of tris(trimethylsilyl)phosphate, tris(trimethylsilyl)borate or tris(trimethylsilyl)phosphite.

16. A battery, characterized in that: The invention comprises the electrolyte described in any one of claims 1 to 15.

17. The battery according to claim 16, characterized in that The battery comprises a lithium ion battery.

18. The battery according to claim 16 or 17, characterized in that: The battery comprises a positive electrode plate, wherein the positive electrode active material of the positive electrode plate satisfies at least one of the following conditions: The volume average particle size D of the positive electrode active material v 50: 1μm-4μm; The BET specific surface area of ​​the positive electrode active material is 1 m 2 / g-4m 2 / g; The compaction density of the positive electrode active material under a pressure of 300 MPa is 3.2 g / cm 3 -3.8g / cm 3 .

19. The battery according to any one of claims 16 to 18, characterized in that The battery comprises a negative electrode plate, wherein the negative electrode active material of the negative electrode plate satisfies at least one of the following conditions: The volume average particle size D of the negative electrode active material v 50: 1μm-4μm; The BET specific surface area of ​​the negative electrode active material is 1 m 2 / g-4m 2 / g; The compaction density of the negative electrode active material at a pressure of 300 MPa is 1.4 g / cm 3 -1.8g / cm 3 .

20. An electrical equipment, characterized in that: The battery comprises the battery according to any one of claims 16 to 19.

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