Electrolyte, battery and electric equipment

Abstract

The invention provides an electrolyte, a battery and electric equipment, the electrolyte comprises AxOyZ-and PO2F2-, A comprises at least one of P, S or Si, 1 < = x < = 2, 4 < = y < = 5, 2 < = z < = 3.

Description

Electrolyte, battery and electrical equipment Technical Field

[0001] 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

[0002] Lithium-ion batteries are not only used in energy storage power systems such as hydropower, thermal power, wind power and solar power stations, but are also widely used in electric vehicles such as electric bicycles, electric motorcycles, electric cars, as well as in military equipment, aerospace and other fields.

[0003] 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.

[0004] Summary of the Invention

[0005] In view of the technical problems existing in the background technology, the present application provides an electrolyte, which aims 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 PO2F2 - , A includes at least one of P, S or Si, 1≤x≤2, 4≤y≤5, 2≤z≤3.

[0007] The electrolyte composition of the present application 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.

[0008] In some embodiments of the present application, the A x O y Z- Including PO4 3- 、SO4 2- or Si2O5 2- At least one of, optionally including PO4 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 PO2F2 -The total mass concentration of is less than or equal to 2000 ppm, and can be optionally 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 PO2F2 is m, - 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 1 ppm-1000 ppm, and can be optionally 1 ppm-200 ppm. 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 PO2F2 - The mass concentration n of is 1 ppm-1000 ppm, and can be optionally 1 ppm-200 ppm. 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 during the cyclic charge and discharge process of the lithium-ion battery containing the film-forming additive.

[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), optionally 1:(20-80). This can reduce the DCR growth rate of the lithium-ion battery containing the film-forming additive during the cyclic charge and discharge process.

[0015] In some embodiments of the present application, the mass concentration w of the film-forming additive is 0.2%-0.5%, and 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 a lithium-ion battery containing the film-forming additive during cyclic charge and discharge can be reduced.

[0017] The second aspect of the present application provides a battery comprising the electrolyte of the first aspect of the present application, thereby having 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 meets 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 at 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 meets 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 comprising 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 obvious from the description below, or will be learned through practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Various other advantages and benefits will become apparent to those skilled in the art upon reading the detailed description of the optional embodiments below. The accompanying drawings are provided for illustration purposes only and are not to be considered as limiting the present application. The same reference numerals are used throughout the drawings to denote the same components. In the drawings:

[0029] FIG1 is a schematic structural diagram of a battery according to an embodiment of the present application;

[0030] FIG2 is a schematic structural diagram of a battery module according to an embodiment of the present application;

[0031] FIG3 is a schematic structural diagram of a battery pack according to an embodiment of the present application;

[0032] FIG4 is an exploded view of FIG3 ;

[0033] FIG5 is a schematic diagram of an embodiment of an electric device using a battery 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 embodiments of the technical solution of the present application are described in detail. 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 are not intended to limit the scope of protection of the present application.

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

[0038] For the sake of clarity, only some numerical ranges are specifically disclosed herein. However, any lower limit may be combined with any upper limit to form an unspecified range; and any lower limit may be combined with other lower limits to form an unspecified range, and similarly, any upper limit may be combined with any other upper limit to form an unspecified range. In addition, each individually disclosed point or single value may itself serve as a lower limit or upper limit and be combined 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 this application, the term "and / or" is simply a description of the association relationship between associated objects, indicating that three relationships can exist. For example, A and / or B can represent the following three situations: A exists alone, A and B exist simultaneously, and B exists alone. In addition, the character " / " in this document generally indicates that the associated objects are in an "or" relationship.

[0040] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art 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" and any variations thereof in the specification and claims of this application and the above-mentioned figure descriptions are intended to cover non-exclusive inclusions.

[0041] Currently, market developments indicate that lithium-ion batteries are becoming increasingly widely used. They are not only used in energy storage systems such as hydropower, thermal power, wind power, and solar power plants, but are also widely used in electric vehicles like electric bicycles, electric motorcycles, and electric cars, as well as in military equipment and aerospace. As the application of lithium-ion batteries continues to expand, market demand is also growing.

[0042] During the charge and discharge process of a lithium-ion battery, lithium ions are released from the positive electrode, migrate through the electrolyte to the negative electrode under the action of an electric field, and are embedded in the negative electrode active material. During discharge, lithium ions are released from the negative electrode active material, migrate through the electrolyte to the positive electrode under the action of an electric field, and are embedded in the positive electrode active material. As the secondary battery cycles through charge and discharge, 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, consuming active lithium. On the other hand, the accumulation of side reaction products on the surface of the positive electrode active material makes lithium ion transmission difficult, preventing the lithium ions from being fully embedded in the material. Ultimately, this leads to the continuous loss of active lithium in the positive electrode active material, causing the DCR of the lithium-ion battery to continue to increase, thereby reducing the battery's power performance.

[0043] In this application, the electrolyte includes A x O yZ- and PO2F2 - , 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 PO2F2 - It can provide AO bond, A=O bond, PO bond and P=O bond, 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. After being oxidized, it can form a film on the surface of the positive electrode, thereby protecting the active lithium in the positive electrode. At the same time, during the battery charging process, PO2F2 - 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 sheet. After 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 surface ion conductivity of the oxidized product is solved. Since the radius of F ions and lithium ions is close, the binding energy is 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 devices that use batteries as power sources or various energy storage systems that use batteries as energy storage elements. Electrical devices may include, but are not limited to, mobile phones, tablets, laptops, electric toys, power 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, comprising: A x O y Z- and PO2F2 - , A includes at least one of P, S and Si, 1≤x≤2, 4≤y≤5, 2≤z≤3.

[0046] The present application includes at least the following beneficial effects: the electrolyte of the present application includes Ax O y Z- and PO2F2 - On the one hand, A x O y Z- and PO2F2 - It can provide AO bond, A=O bond, PO bond and P=O bond, 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. After being oxidized, it can form a film on the surface of the positive electrode, thereby protecting the active lithium in the positive electrode. At the same time, during the battery charging process, PO2F2 - 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 sheet. After 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 surface ion conductivity of the oxidized product is solved. Since the radius of F ions and lithium ions is close, the binding energy is 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-mentioned 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 PO4 3- 、SO4 2- or Si2O5 2- Thus, the above 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 PO4 3- .

[0048] It should be noted that in this application, A x O y Z- and PO2F2 - Added to the electrolyte in the form of lithium salt, such as Li3PO4, Li2SO4, Li2Si2O5, LiPO2F2.

[0049] In some embodiments of the present application, based on the total mass of the electrolyte, the A x O y Z- and the PO2F2 - 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 PO2F2 - The total mass concentration of 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 PO2F2 - The total mass concentration is less than or equal to 1500ppm.

[0050] It should be noted that "ppm" refers to the mass concentration, which refers to the concentration of A in the electrolyte. x Oy Z- and PO2F2 - The ratio of the total mass of the electrolyte to the mass of the electrolyte is 1ppm = 0.0001%. x O y Z- and PO2F2 - The mass concentration test method can be determined using instruments and methods known in the art, for example, ion chromatography can be used for testing, and the instrument uses ICS-900 ion chromatograph, and the test method is specifically referred 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 PO2F2 is m, - The mass concentration is n, 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. Thus, the present application will be the PO2F2 in the electrolyte - The mass concentration n and 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 while reducing the DCR growth rate during the cyclic charge and discharge process of the lithium ion battery, 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 PO2F2 - 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 charge and discharge cycle, 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 PO2F2 - 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 PO2F2 in the electrolyte. - 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 PO2F2 - 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, "film-forming additive" can 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 and / or a SEI film (solid electrolyte interface) on the surface of the negative electrode. x O y Z- and PO2F2 - 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 cycle 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 PO2F2 - The mass concentration of and the mass concentration ratio of the film-forming additive are within the above ranges, 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 A x O y Z- The mass concentration m of the PO2F2 - The mass concentration n and the mass concentration w of the film-forming additive satisfy (m+n) / w of 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%, for example, 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. Thus, 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 determined 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 solution may further include an electrolyte salt and a solvent.

[0060] As an example, the electrolyte salt may include at least one of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bisfluorosulfonyl imide (LiFSI), lithium bistrifluoromethanesulfonyl imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalatoborate (LiDFOB), lithium bisoxalatoborate (LiBOB), lithium difluorophosphate (LiPO2F2), lithium difluorobisoxalatophosphate (LiDFOP), or lithium tetrafluorooxalatophosphate (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 comprising the electrolyte described in the first aspect of the present application, thereby having low DC internal resistance and excellent power performance.

[0064] A battery is a battery that can be recharged to activate the active materials after discharge and continue to be used.

[0065] Typically, a battery consists of a positive electrode, a negative electrode, a separator, and an electrolyte. During the battery's charge and discharge processes, active ions are inserted and removed between the positive and negative electrodes. The separator is placed between the positive and negative electrodes to isolate them. The electrolyte conducts ions between the positive and negative electrodes.

[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. 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 a lithium transition metal oxide, an olivine-structured lithium-containing phosphate, 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 olivine-structured lithium-containing phosphates 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 through commercial channels.

[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 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 v50 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 is 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 this application, the specific surface area of ​​the positive electrode active material can be tested by referring to the following method: using the American Microelectronics 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 host 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 this application, "compacted density" has a meaning well known in the art and can be measured using instruments and methods well known in the art. For example, the following test method can be used: a fixed amount m of powder 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 (see GB / T24533-2009 for details).

[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 within the positive electrode active material is small and the surface side reactions are small, which promotes the positive electrode active material to exert its specific capacity and improves the capacity retention rate of the battery containing it.

[0079] [Negative electrode]

[0080] In a battery, the negative electrode sheet 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 that can be used for the negative electrode of a secondary battery known in the art can be used, and those skilled in the art can make a choice 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 (such as silicon monoxide), silicon-carbon composite, silicon-nitrogen composite, and silicon alloy. The tin-based material may include at least one of elemental tin, tin oxide, and tin alloy. These materials can all be obtained commercially.

[0083] In some embodiments, 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 other embodiments of the present application, the volume average particle size D of the negative electrode active material is v50 is 1μm-3μm.

[0085] In this 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 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 for the BET specific surface area of ​​the negative electrode active material can refer to the test method for 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 sheet 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 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 for the "compacted density of the positive electrode sheet" described above. It is worth noting that deionized water is often used to wipe the active material layer of the negative electrode.

[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 carboxymethyl cellulose 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. FIG1 shows a secondary battery 1 with a square structure as an example.

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

[0097] In some embodiments, the outer packaging may include a housing and a cover. The housing may include a bottom plate and side plates connected to the bottom plate, with the bottom plate and side plates enclosing a receiving cavity. The housing may have an opening communicating with the receiving cavity, and the cover may be positioned over the opening to seal the receiving cavity.

[0098] The positive electrode sheet, negative electrode sheet, and separator can be wound or laminated to form an electrode assembly. The electrode assembly is encapsulated in the housing. The number of electrode assemblies in a battery can include one or more, which can be adjusted according to needs.

[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 bag, such as a bag-type soft bag. The material of the soft bag may be plastic, such as at least one of polypropylene (PP), polybutylene terephthalate (PBT), and polybutylene succinate (PBS).

[0101] In some embodiments, 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 shows an example battery module 2. Referring to Figure 2 , within the battery module 2, multiple secondary batteries 1 may be arranged sequentially along the length of the battery module 2. Of course, any other arrangement is also possible. Furthermore, the multiple secondary batteries 1 may be secured together using fasteners.

[0103] The battery module 2 may further include a housing having a housing space, wherein the housing space accommodates a plurality of secondary batteries 1. 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] Figures 3 and 4 illustrate an example battery pack 3. Referring to Figures 3 and 4 , the battery pack 3 may include a battery box and multiple battery modules 2 disposed within the battery box. The battery box comprises an upper case 4 and a lower case 5. The upper case 4 can be placed over the lower case 5 to form an enclosed space for accommodating the battery modules 2. The multiple battery modules 2 can be arranged in any manner within the battery box.

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

[0106] FIG5 shows an example of an electric device, which includes a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle.

[0107] As another example, electric devices may include mobile phones, tablet computers, and laptop computers. These electric devices are generally required to be lightweight and thin, and may use batteries as power sources.

[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 drawings. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is in no way intended to limit the present application and its applications. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this 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 O2, conductive agent Super P, and binder polyvinylidene fluoride (PVDF) are prepared into 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 The mass ratio of O2, 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 and striped, and dried under vacuum conditions at 85°C 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 components 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 under vacuum conditions at 120°C 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 yand LiPO2F2 are added to an organic solvent (the organic solvent includes ethylene carbonate (EC) and ethyl methyl carbonate (EMC), and the mass ratio of EC to EMC is 3:7), and after mixing evenly, LiPF6 and LiFSI are slowly added. 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, separator, and negative electrode sheet are stacked in order, with the separator placed between the positive and negative electrode sheets to isolate the positive and negative electrodes. The bare battery cell is wound and the tabs are welded. The bare battery cell is placed in an outer package, and the above-prepared electrolyte is injected into the dried battery cell. The battery cell is packaged, allowed to stand, formed, shaped, and capacity tested to complete the preparation of the lithium-ion battery (the thickness of the soft-pack lithium-ion battery is 4.0 mm, the width is 60 mm, and the length is 140 mm).

[0120] The preparation methods of the lithium ion batteries of Examples 2-39 and Comparative Examples 1-4 are the same as those 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 cycling the battery, adjust the SOC to 50%. Then, discharge it at 4C for 30 seconds. The pre-discharge voltage is recorded as V1, and the post-discharge voltage is recorded as V2. Calculate DCR1 = (V1 - V2) / I (where I corresponds to the 4C discharge current). After 300 cycles, remove the battery. Test DCR2 using the same protocol, calculating ΔDCR = (DCR2 - DCR1) / DCR1, where ΔDCR represents the rate of increase in the battery's DCR.

[0126] Table 2

[0127] 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 shows that the lithium-ion batteries of the present application including A x O yZ- and PO2F2 - The electrolyte can effectively reduce the DCR growth rate of the battery containing it during the cycle charge and discharge process, thereby improving the power performance of the lithium-ion battery.

[0128] 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 make equivalent replacements for some or all of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions 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, wherein 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.

2. The electrolyte according to claim 1, wherein 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, wherein The A x O y Z- Including PO4 3- .

4. The electrolyte according to any one of claims 1 to 3, wherein Based on the total mass of the electrolyte, the A x O y Z- And the PO2F2 - The sum of the mass concentrations is less than or equal to 2000ppm.

5. The electrolyte according to any one of claims 1 to 4, wherein Based on the total mass of the electrolyte, the A x O y Z- And the PO2F2 - The sum of the mass concentrations is less than or equal to 1500 ppm.

6. The electrolyte according to any one of claims 1 to 5, wherein Based on the total mass of the electrolyte, the A x O y Z- The mass concentration of PO2F2 is m, - The mass concentration is n, n / m=(10-1000):

1.

7. The electrolyte according to claim 6, wherein n / m=(100-500):

1.

8. The electrolyte according to claim 6 or 7, wherein Based on the total mass of the electrolyte, the A x O y Z- The mass concentration m is 1ppm-1000ppm.

9. The electrolyte according to any one of claims 6 to 8, wherein Based on the total mass of the electrolyte, the A x O y Z- The mass concentration m is 1ppm-200ppm.

10. The electrolyte according to any one of claims 6 to 9, wherein Based on the total mass of the electrolyte, the PO2F2 - The mass concentration n is 1ppm-1000ppm.

11. The electrolyte according to any one of claims 6 to 10, wherein Based on the total mass of the electrolyte, the PO2F2 - The mass concentration n is 1ppm-200ppm.

12. The electrolyte according to any one of claims 6 to 11, wherein The electrolyte also includes a film-forming additive.

13. The electrolyte according to claim 12, wherein 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).

14. The electrolyte according to claim 13, wherein (m+n) / w is 1:(20-80).

15. The electrolyte according to claim 13 or 14, wherein The mass concentration w of the film-forming additive is 0.2%-0.5%.

16. The electrolyte according to any one of claims 13 to 15, wherein The mass concentration w of the film-forming additive is 0.25%-0.45%.

17. The electrolyte according to any one of claims 12 to 16, wherein The film-forming additive includes at least one of tris(trimethylsilyl)phosphate, tris(trimethylsilyl)borate or tris(trimethylsilyl)phosphite.

18. A battery, wherein: The invention comprises the electrolyte described in any one of claims 1 to 17.

19. The battery according to claim 18, wherein The battery comprises a lithium ion battery.

20. The battery according to claim 18 or 19, wherein 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 at a pressure of 300 MPa is 3.2 g / cm 3 -3.8g / cm 3 .

21. The battery according to any one of claims 18 to 20, wherein 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 .

22. An electrical device, wherein: A battery comprising any one of claims 18 to 21.

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