Battery cell, battery device, and electric device

Abstract

Provided is a battery cell (5), comprising an electrode assembly (52). The electrode assembly (52) comprises a positive electrode sheet, a negative electrode sheet, a separator, and an electrolyte. The negative electrode sheet comprises a negative electrode current collector and a negative electrode active layer arranged on at least one side of the negative electrode current collector. The negative electrode active layer comprises a negative electrode active material. The negative electrode active material comprises a silicon-based negative electrode material. The electrolyte comprises an additive. The additive comprises fluoroether. Also provided are a battery device comprising the battery cell (5) and an electric device comprising the battery cell (5).

Description

Battery cells, battery packs and electrical devices Technical Field

[0001] This application relates to the field of battery technology, and in particular to a battery cell, a battery device, and an electrical device. Background Technology

[0002] In the development of high-energy-density battery systems, silicon is often used as a negative electrode active material due to its specific capacity advantage; for example, a mixture of graphite and silicon-carbon materials is often used. However, the low conductivity of silicon materials leads to poor kinetic performance of the electrode and a longer charging time.

[0003] To address this issue, existing technologies employ a design scheme with a thin coating of the negative electrode film, but this design scheme leads to a loss of battery energy density. Summary of the Invention

[0004] This application provides a battery cell, a battery device, and an electrical device to solve the problem of poor dynamic performance, particularly poor charging performance, of secondary batteries.

[0005] A first aspect of the present invention provides a battery cell including an electrode assembly comprising a positive electrode, a negative electrode, a separator, and an electrolyte. The negative electrode includes a negative current collector and a negative active layer disposed on at least one side of the negative current collector. The negative active layer includes a negative active material, which includes a silicon-based negative electrode material. The electrolyte includes an additive, which includes a fluorinated ether. This application also provides a battery device and an electrical device including the battery cell. Attached Figure Description

[0006] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments of this application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on the drawings without creative effort.

[0007] Figure 1 is a schematic diagram of a battery cell according to one embodiment of this application.

[0008] Figure 2 is an exploded view of a battery cell according to an embodiment of this application shown in Figure 1.

[0009] Figure 3 is a schematic diagram of a battery module according to one embodiment of this application.

[0010] Figure 4 is a schematic diagram of a battery pack according to one embodiment of this application.

[0011] Figure 5 is an exploded view of the battery pack of one embodiment of this application shown in Figure 4.

[0012] Figure 6 is a schematic diagram of an electrical device using a secondary battery as a power source according to an embodiment of this application.

[0013] The accompanying drawings are not drawn to scale.

[0014] Explanation of reference numerals in the attached figures:

[0015] 1 Battery pack; 2 Upper housing; 3 Lower housing; 4 Battery module; 5 Battery cell; 51 Casing; 52 Electrode assembly; 53 End cap. Detailed Implementation

[0016] The embodiments of this application will be described in further detail below with reference to the accompanying drawings and examples. The detailed description of the following embodiments and the accompanying drawings are used to illustrate the principles of this application by way of example, but should not be used to limit the scope of this application, that is, this application is not limited to the described embodiments.

[0017] The following detailed description, with appropriate reference to the accompanying drawings, specifically discloses embodiments of the battery cell, battery device, and power-consuming device of this application. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided to enable those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0018] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0019] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0020] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0021] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0022] Unless otherwise specified, the terms "comprising" and "including" as used in this application are open-ended. For example, "comprising" and "including" may mean that other components not listed may also be included or contained.

[0023] Unless otherwise specified, the term "or" is inclusive in this application. For example, any of the following conditions satisfies the condition "A or B": A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0024] [Battery cell]

[0025] In this embodiment of the application, the battery cell can be a secondary battery, which refers to a battery cell that can be recharged to activate the active materials and continue to be used after the battery cell has been discharged.

[0026] The battery cell can be a lithium-ion battery, sodium-ion battery, sodium-lithium-ion battery, lithium metal battery, sodium metal battery, lithium-sulfur battery, magnesium-ion battery, nickel-metal hydride battery, nickel-cadmium battery, lead-acid battery, etc., and the embodiments of this application are not limited to this.

[0027] A single battery cell typically includes an electrode assembly. The electrode assembly includes a positive electrode, a negative electrode, and a separator, with the separator positioned between the positive and negative electrodes. During the charging and discharging process of a single battery cell, active ions (such as lithium ions) repeatedly insert and extract between the positive and negative electrodes. The separator, positioned between the positive and negative electrodes, prevents short circuits between the positive and negative electrodes while allowing active ions to pass through.

[0028] The first embodiment of this application provides a battery cell including an electrode assembly. The electrode assembly includes a positive electrode, a negative electrode, a separator, and an electrolyte. The negative electrode includes a negative current collector and a negative active layer disposed on at least one side of the negative current collector. The negative active layer includes a negative active material, which includes a silicon-based negative electrode material. The electrolyte includes additives, which include fluorinated ethers.

[0029] This application uses fluorinated ethers as additives in the electrolyte. The coordination of fluoride ions with active ions in the fluorinated ethers improves the ionic conductivity of the electrolyte, compensating for the insufficient conductivity of silicon materials, and thus improving the charging performance of the battery cells. In addition, fluorinated ethers have good oxidation stability, so they do not affect the cycle stability of the battery cells.

[0030] Since the use of the above-mentioned fluorinated ethers improves the ionic conductivity of the electrolyte and compensates for the insufficient conductivity of the silicon anode material, the content of the silicon anode material can be increased to a certain extent, thereby making full use of the silicon anode material to improve the energy density of the battery cell.

[0031] Electrolyte

[0032] In some embodiments, the fluoroether includes one or more combinations of monofluorinated bis(2-fluoroethyl) ether, difluorinated bis(2-fluoroethyl) ether, trifluorinated bis(2-fluoroethyl) ether, perfluorinated bis(2,2,2-trifluoroethyl) ether, bis(difluoroethyl) ether (BDE), 2,2,2-trifluoroethyl 2-fluoroethyl ether (TFFE), 1,1-difluoroethyl 2-fluoroethyl ether (DFE), monofluorinated bis(2-fluoroethyl) ether (BFE), or bis(2,2,2-trifluoroethoxy)ethane (BTFEOE).

[0033] In some embodiments, the content of fluorinated ethers in the electrolyte is 0.3% to 2% by weight. Controlling the content of fluorinated ethers within the above range can effectively control the excessive boiling point of the electrolyte caused by excessive fluorinated ethers, which is detrimental to production and safety, while also preventing unstable SEI film formation at the negative electrode and affecting its lifespan. This is because the boiling point affects the battery interface, leading to purple spots or lithium plating, thereby affecting the stability of the SEI.

[0034] To further enhance the active ion conduction of the electrolyte, in some embodiments, the electrolyte also includes a lithium salt, including fluorinated lithium salts.

[0035] In some embodiments, the electrolyte includes a fluorinated lithium salt, which includes one or more combinations of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium bis(fluorosulfonyl)imide (LiFSI), lithium fluorosulfonyl-trifluorosulfonylimide (LiFTFSI), or lithium difluoro(oxalate-borate)borate (LiDFOB). The fluorinated lithium salt acts as both an ion conductor in the electrolyte and, in conjunction with the fluorinated ether, a solvent that participates in the formation of the solvation sheath of lithium ions, thereby altering the migration and desolvation structure of lithium ions, thus increasing the ion migration rate and further improving the battery's charging performance.

[0036] In some embodiments, the concentration of the fluorinated lithium salt in the electrolyte is 0.1–1.2 mol / L.

[0037] In some embodiments, the mass ratio of fluorinated lithium salt to fluorinated ether is (99-90):(10-1), optionally (99-90):(1-5). Fluorinated ether can regulate the solvation structure, but the relative lithium salt content cannot be too high, otherwise the lithium salt will not be able to exert its ion conduction ability.

[0038] In some embodiments, the fluorinated lithium salt includes lithium hexafluorophosphate (LiPF6) and lithium bis(fluorosulfonyl)imide (LiFSI), and the fluorinated ether includes monofluorinated bis(2-fluoroethyl) ether and 2,2,2-trifluoroethyl 2-fluoroethyl ether (TFFE). This selection and combination achieves optimal SEI composition and optimal solvent structure with low interfacial impedance.

[0039] In some embodiments, the solvent may be selected from at least one of ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butyl carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

[0040] In some embodiments, the electrolyte may optionally include additional additives. As examples, additional additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain battery performance, such as additives that improve battery overcharge performance, additives that improve battery high-temperature or low-temperature performance, etc.

[0041] [Negative electrode plate]

[0042] The negative electrode sheet includes a negative current collector and a negative active layer disposed on at least one surface of the negative current collector, the negative active layer comprising a negative active material.

[0043] As an example, the negative electrode current collector has two surfaces opposite each other in its own thickness direction, and the negative electrode active layer is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0044] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer material substrate and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0045] In order to make full use of silicon to improve the energy density of battery cells, in some embodiments, the mass ratio of silicon in the negative electrode active material is 9% to 65%, and can be selected as 9% to 35%.

[0046] In some implementations, the silicon-based anode material includes a silicon-carbon composite material. Compared to other silicon materials, silicon-carbon composite materials have the advantages of less expansion and better cycle life.

[0047] In some embodiments, the silicon content in the silicon-carbon composite material is 35%-70% by mass.

[0048] In some embodiments, the average particle size of the silicon-carbon composite material is 3-15 μm, as measured using a laser particle size analyzer. The relatively small particle size of the silicon-carbon composite material within this average particle size range allows for a higher compaction density in the negative electrode active layer, reducing its thickness. Furthermore, the smaller interparticle spacing of the silicon-carbon composite material in the negative electrode active layer shortens the lithium-ion transport path, further improving the charging performance of the battery cell.

[0049] To further improve the charging performance of individual battery cells, in some embodiments, the negative electrode active material of the battery also includes graphite.

[0050] As an example, the graphite mentioned above may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, and hard carbon.

[0051] In some embodiments, the graphite is fast-charging graphite with a D50 between 3 and 12 μm, which is measured by a laser particle size analyzer, or it is spherical secondary particles that can be observed by an electron microscope such as a scanning electron microscope (SEM) or a transmission electron microscope (TEM). The electron microscope images can intuitively reflect the spheroidization effect of the secondary granulation process, such as particle size distribution, degree of agglomeration and surface smoothness.

[0052] In some embodiments, the coating weight of the negative electrode active layer is 2–8 mg / cm³. 2 The coating weight was tested using a simple weighing method. Specifically, the negative electrode was cut into a 5*5cm square sheet, weighed using an electronic balance, and the weight was recorded as m1 g. Then, the electrode sheet was soaked in DMC to remove all the active material layer from the current collector surface. The current collector was then weighed, and the weight was recorded as m2 g. The coating weight was calculated as (m1-m2)*1000 / 2 / 25. At the above coating weight, the thickness of the negative electrode active layer decreased, thereby shortening the ion transport path and reducing its tortuosity, which can further improve the kinetics of the battery cell.

[0053] In some embodiments, the negative electrode film layer may optionally include a binder. As an example, the binder may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0054] In some embodiments, the negative electrode film may optionally include a conductive agent. As an example, the conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0055] In some embodiments, the negative electrode film may optionally include other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)).

[0056] In some embodiments, the negative electrode sheet can be prepared by dispersing the components used to prepare the negative electrode sheet, such as the negative electrode active material, conductive agent, binder and any other components, in a solvent (e.g., deionized water) to form a negative electrode slurry; coating the negative electrode slurry onto the negative electrode current collector, and then obtaining the negative electrode sheet after drying, cold pressing and other processes.

[0057] [Positive electrode plate]

[0058] A positive electrode typically includes a positive current collector and a positive active layer disposed on at least one surface of the positive current collector, the positive active layer comprising a positive active material.

[0059] As an example, the positive current collector has two surfaces opposite each other in its own thickness direction, and the positive active layer is disposed on either or both of the two opposite surfaces of the positive current collector.

[0060] In some embodiments, the positive current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0061] In some embodiments, the positive electrode active material may also be a known battery positive electrode active material. As an example, when the secondary battery is a lithium-ion secondary battery, the positive electrode active material may include at least one of the following materials: lithium phosphates with an olivine structure, lithium transition metal oxides, and their respective modified compounds. However, this application is not limited to these materials, and other conventional materials that can be used as battery positive electrode active materials may also be used. These positive electrode active materials may be used alone or in combination of two or more. Examples of lithium transition metal oxides include, but are not limited to, lithium cobalt oxides (such as LiCoO2), lithium nickel oxides (such as LiNiO2), lithium manganese oxides (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxides, lithium manganese cobalt oxides, lithium nickel manganese oxides, and lithium nickel cobalt manganese oxides (such as LiNi). 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (also known as NCM) 333 LiNi 0.5 Co 0.2 Mn 0.3 O2 (also known as NCM) 523 LiNi 0.5 Co 0.25 Mn 0.25 O2 (also known as NCM) 211 LiNi 0.6 Co 0.2 Mn 0.2 O2 (also known as NCM) 622 LiNi 0.8 Co 0.1 Mn 0.1 O2 (also known as NCM) 811 ), lithium nickel cobalt aluminum oxide (such as LiNi) 0.85 Co 0.15 Al 0.05At least one of O2 and its modified compounds. Examples of lithium phosphates with an olivine structure include, but are not limited to, lithium iron phosphate (such as LiFePO4 (also referred to as LFP)), lithium iron phosphate and carbon composites, lithium manganese phosphate (such as LiMnPO4), lithium manganese phosphate and carbon composites, lithium manganese iron phosphate, and lithium manganese iron phosphate and carbon composites.

[0062] In some implementations, the battery cell is a lithium-ion battery cell.

[0063] In some embodiments, the positive electrode includes a positive active material, which includes a lithium transition metal oxide having the chemical formula Li. a Ni b Co c Mn d M e O 2-f Wherein, M includes one or more elements selected from Al, Fe, Ti, Mg, Zr, Cr, Ga, Cu, Zn, Nb, and B; a is any value in the range of 0.4-1.2, and can be selected from any value in the range of 0.8-1.2; b is any value in the range of 0.45-0.95, and can be selected from any value in the range of 0.5-0.85; c is any value in the range of 0.02-0.25, and can be selected from any value in the range of 0.02-0.2; d is any value in the range of 0.05-0.5, and can be selected from any value in the range of 0.05-0.48; e is any value in the range of 0-0.2, and can be selected from any value in the range of 0.001-0.2; f is any value in the range of 0-0.3, and can be selected from any value in the range of 0-0.2. Higher nickel content results in higher specific capacity of the positive electrode, better matching with high-capacity silicon anodes, thus enabling higher energy density in the battery cell.

[0064] In some embodiments, the volumetric energy density of the battery cell ranges from 750Wh / L to 1000Wh / L.

[0065] When the secondary battery is a sodium-ion secondary battery, as an example, the positive electrode active material of the sodium-ion secondary battery may include at least one of the following materials: sodium transition metal oxides, polyanionic compounds, and Prussian blue compounds. However, this application is not limited to these materials, and other conventionally known materials that can be used as positive electrode active materials for sodium-ion batteries may also be used.

[0066] As an optional technical solution in this application, the transition metal in the sodium transition metal oxide can be at least one selected from Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce. For example, the sodium transition metal oxide is Na.x MO2, where M is one or more of Ti, V, Mn, Co, Ni, Fe, Cr and Cu, and 0 < x ≤ 1.

[0067] As an optional technical solution in this application, the polyanionic compound can be a compound containing sodium ions, transition metal ions, or a tetrahedral (YO4) structure. n- A class of compounds with anionic units. The transition metal can be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce; Y can be at least one of P, S, and Si; n represents (YO4). n- The price state.

[0068] Polyanionic compounds can also contain sodium ions, transition metal ions, or tetrahedral (YO4) ions. n- A class of compounds containing anionic units and halide anions. The transition metal can be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce; Y can be at least one of P, S, and Si, and n represents (YO4). n- The valence state; the halogen can be at least one of F, Cl and Br.

[0069] Polyanionic compounds can also be sodium-containing tetrahedral (YO4) compounds. n- Anionic unit, polyhedral unit (ZO) y ) m+ And a class of compounds with optional halide anions. Y can be at least one of P, S, and Si, and n represents (YO4). n- The valence state; Z represents a transition metal, which can be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce; m represents (ZO) y ) m+ The valence state; the halogen can be at least one of F, Cl and Br.

[0070] Polyanionic compounds include, for example, NaFePO4, Na3V2(PO4)3 (sodium vanadium phosphate, abbreviated as NVP), Na4Fe3(PO4)2 (P2O7), NaM'PO4F (M' is one or more of V, Fe, Mn and Ni), and Na3(VO4) y )2(PO4)2F 3-2y At least one of (0≤y≤1).

[0071] Prussian blue compounds can be a class of compounds containing sodium ions, transition metal ions, and cyanide ions (CN-). The transition metal can be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce. Examples of Prussian blue compounds include Na. a Me b Me' c (CN)6, wherein Me and Me' are each independently at least one of Ni, Cu, Fe, Mn, Co and Zn, 0 < a ≤ 2, 0 < b < 1, 0 < c < 1.

[0072] In some embodiments, the positive electrode film layer may optionally include a binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0073] In some embodiments, the positive electrode film may optionally include a conductive agent. As an example, the conductive agent may include at least one selected from superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0074] In some embodiments, the positive electrode sheet can be prepared by dispersing the above-mentioned components for preparing the positive electrode sheet, such as positive active material, conductive agent, binder and any other components, in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry onto the positive electrode current collector, and then obtaining the positive electrode sheet after drying, cold pressing and other processes.

[0075] [Isolation Component]

[0076] In some embodiments, the secondary battery also includes a separator. This application does not impose any particular limitation on the type of separator; any known porous separator with good chemical and mechanical stability can be selected.

[0077] In some embodiments, the separator is a separator membrane. This application does not impose any particular limitation on the type of separator membrane; any known porous separator membrane with good chemical and mechanical stability can be selected.

[0078] As an example, the main material of the separator can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, polyvinylidene fluoride, and ceramic. The separator can be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation. The separator can be a single component located between the positive and negative electrodes, or it can be attached to the surfaces of the positive and negative electrodes. An inorganic particle coating, an organic particle coating, or an organic / inorganic composite coating can also be applied to the surface of the separator.

[0079] In some embodiments, the separator is a solid electrolyte. The solid electrolyte is disposed between the positive and negative electrodes, serving both to transport ions and isolate the positive and negative electrodes. In some embodiments, the positive electrode, negative electrode, and separator can be fabricated into an electrode assembly using a winding or stacking process.

[0080] [Electrode Assembly]

[0081] The electrode assembly can be a wound structure, a stacked structure, or a hybrid structure of wound and stacked.

[0082] In some embodiments, the electrode assembly is a wound structure. The positive electrode and the negative electrode are wound into a wound structure.

[0083] In some implementations, the electrode assembly is a stacked structure.

[0084] As an example, multiple positive and negative electrode plates can be set, and multiple positive and multiple negative electrode plates can be stacked alternately.

[0085] As an example, multiple positive electrode sheets can be set, and negative electrode sheets are folded to form multiple stacked folded segments, with a positive electrode sheet sandwiched between adjacent folded segments.

[0086] As an example, both the positive and negative electrode sheets are folded to form multiple stacked folded segments.

[0087] As an example, multiple separators can be provided, each positioned between any adjacent positive or negative electrode plates.

[0088] As an example, the separator can be continuously arranged between any adjacent positive or negative electrode plates by folding or rolling.

[0089] In some embodiments, the electrode assembly can be cylindrical, flat, or polygonal, etc.

[0090] In some embodiments, the electrode assembly is provided with tabs that allow current to be drawn from the electrode assembly. The tabs include a positive tab and a negative tab.

[0091] [shell]

[0092] In some embodiments, the battery cell may include a casing. The casing may be a steel casing, an aluminum casing, a plastic casing (such as a polypropylene casing), a composite metal casing (such as a copper-aluminum composite casing), or an aluminum-plastic film, etc. In some embodiments, the casing may be a sealed structure or a non-sealed structure. As an example, when the casing is a non-sealed structure, the casing serves to protect the electrode assembly, and a sealing bag is included between the casing and the electrode assembly to encapsulate the electrode assembly and electrolyte. Specifically, the sealing bag may be a bag-shaped insulating component or an aluminum-plastic film. When the casing is a sealed structure, it is used to encapsulate components such as the electrode assembly and electrolyte.

[0093] As an example, the battery cell can be a cylindrical battery cell, a prismatic battery cell, a pouch battery cell, or a battery cell of other shapes. Prismatic battery cells include prismatic battery cells, blade-shaped battery cells, and multi-prismatic batteries, such as hexagonal prismatic batteries. This application does not have any particular limitations.

[0094] In some embodiments, the housing includes an end cap and a housing, the housing having an opening, and the end cap covering the opening. The housing may have one or more openings. The end cap may also have one or more.

[0095] This application does not impose any particular limitation on the shape of the secondary battery cell; it can be cylindrical, square, or any other arbitrary shape. For example, Figure 1 shows a square-structured secondary battery cell 5 as an example.

[0096] In some embodiments, referring to FIG2, the outer packaging may include a housing 51 and a top cover assembly 53. The housing 51 may include a base plate and side plates connected to the base plate, the base plate and side plates forming a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the top cover assembly 53 can cover the opening to close the receiving cavity. A positive electrode, a negative electrode, and a separator may be formed into an electrode assembly 52 by a winding process or a stacking process. The electrode assembly 52 is encapsulated within the receiving cavity. Electrolyte is immersed in the electrode assembly 52. ​​The number of electrode assemblies 52 contained in the secondary battery cell 5 may be one or more, which can be selected by those skilled in the art according to specific practical needs.

[0097] In some implementations, the secondary battery cells can be assembled into a battery module. The number of secondary battery cells contained in the battery module can be one or more, and the specific number can be selected by those skilled in the art according to the application and capacity of the battery module.

[0098] Figure 3 shows a battery module 4 as an example. Referring to Figure 3, in the battery module 4, multiple secondary battery cells 5 can be arranged sequentially along the length of the battery module 4. Of course, they can also be arranged in any other manner. Furthermore, these multiple secondary battery cells 5 can be fixed in place using fasteners.

[0099] Optionally, the battery module 4 may also include a housing with a receiving space in which multiple secondary battery cells 5 are received.

[0100] In some embodiments, the battery modules described above can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be one or more, the specific number of which can be selected by those skilled in the art according to the application and capacity of the battery pack.

[0101] Figures 4 and 5 show a battery pack 1 as an example. Referring to Figures 4 and 5, the battery pack 1 may include a battery box and multiple battery modules 4 disposed within the battery box. The battery box includes an upper box 2 and a lower box 3, the upper box 2 covering the lower box 3 to form a closed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery box.

[0102] In addition, this application also provides an electrical device, which includes the secondary battery provided in this application. The secondary battery can be used 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, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.

[0103] As the electrical device, a single secondary battery cell, a battery module, or a battery pack can be selected according to its usage requirements.

[0104] Figure 6 shows an example of an electrical device. This device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. To meet the high power and high energy density requirements of the secondary battery for this device, a battery pack or battery module can be used.

[0105] [Example]

[0106] The following describes embodiments of this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0107] Example 1

[0108] Positive electrode: Nickel-cobalt-manganese ternary material LiNi 0.8 Co 0.1 Mn 0.1 O2, conductive agent carbon black, and binder polyvinylidene fluoride (PVDF) are mixed in a mass ratio of 97:1:2 with N-methylpyrrolidone to obtain a positive electrode slurry. This slurry is then uniformly coated onto the positive electrode current collector, dried, cold-pressed, and slit to obtain the positive electrode sheet.

[0109] Negative electrode sheet: The negative electrode active material is artificial graphite, silicon-carbon composite material (specifically, a composite material of porous carbon-supported silicon nanoparticles), conductive agent is carbon black, carbon nanotubes (CNTs), binder is styrene-butadiene rubber (SBR), and thickener is sodium carboxymethyl cellulose (CMC). These are added to deionized water in a weight ratio of 60.48:34.02:1:0.375:2.8:1.325 and mixed to obtain a slurry. The slurry is then uniformly coated onto the negative electrode current collector and dried.

[0110] Diaphragm: Polypropylene membrane is used as the diaphragm.

[0111] Electrolyte: LiPF6 was dissolved in a solvent containing ethylene carbonate, methyl ethyl carbonate, and diethyl carbonate in a volume ratio of 1:1:1 to prepare an electrolyte with a concentration of 1 mol / L. The required fluorinated ether monofluorinated bis(2-fluoroethyl) ether was added to the electrolyte. The mass content of the fluorinated ether in the electrolyte is recorded in Table 1 to obtain the desired fast-charging electrolyte.

[0112] Assembly: The above-mentioned positive electrode sheet, separator, and negative electrode sheet are wound or stacked in sequence to obtain a bare cell; the bare cell is placed in a packaging shell, dried, and then injected with electrolyte. After vacuum sealing, standing, formation, shaping and other processes, a lithium-ion battery cell is obtained.

[0113] test:

[0114] Silicon content testing method: ICP. Weigh 0.1g of sample (using active material scraped directly from the anode plate for testing) and add it to a PTFE beaker. Add 10mL of nitric acid and heat to digest. Add another 10mL of nitric acid and repeat the digestion process once more. After cooling, filter the digested solution to remove the residue, and dilute to 100mL in a volumetric flask. Add the prepared solution to the nebulizer and test using inductively coupled plasma atomic emission spectrometry (ICP-AES).

[0115] The electrolyte ion chromatography test refers to the ion chromatography verification procedure section of the "National Metrological Verification Regulations of the People's Republic of China" JJG823-2014, which can detect fluorinated salts. The electrolyte gas chromatography refers to the national standard GB / T 9722-2006 below, which can detect fluorinated ethers. By comparing with the standard spectrum, the presence of fluorinated ethers and fluorinated lithium salts can be identified, and the content can be determined by peak area integration.

[0116] Energy density test:

[0117] 1) Measurement of discharge energy of a single battery cell, using the following method:

[0118] Let the individual battery cells stand at 25°C for 2 hours to ensure that the temperature of the individual battery cells is 25°C.

[0119] At 25°C, the battery cell is charged to the charging cutoff voltage at 0.1C, and then constant voltage charging is continued at the charging cutoff voltage until the current is 0.05C, at which point charging is cut off (where C represents the rated capacity of the battery cell).

[0120] Let the individual battery cells stand at 25°C for 1 hour;

[0121] At 25℃, the battery cells were discharged to the discharge cutoff voltage at 0.1C. The total discharge capacity C0 and the total discharge energy E0 of the battery cells were recorded, with the unit being Wh.

[0122] 2) Battery cell volume measurement: Use vernier calipers to measure the thickness, width and height of the battery cell respectively. Measure 3 times in each direction and take the average value to obtain the thickness T1, width W1 and height H1. Calculate the volume of the battery cell V0 = T1 * W1 * H1, in L;

[0123] 3) Energy density calculation: The volumetric energy density of a battery cell is calculated as E0 / V0.

[0124] Charging performance test:

[0125] Step 1: Voltage Calibration

[0126] 1) Place the stacked three-electrode cell (including the reference electrode for monitoring half potential) with the same design as the battery cell to be tested at 25°C for 30 minutes;

[0127] 2) After charging the battery cell to the charging cutoff voltage at 0.33C at 25℃, continue constant voltage charging at the charging cutoff voltage until the current is 0.05C and charging is cut off (where C represents the rated capacity of the battery cell).

[0128] 3) Let stand at 25℃ for 1 hour;

[0129] 4) Discharge each battery cell at 0.33C to the discharge cutoff voltage at 25℃, and record the total discharge capacity C1 of the battery cell;

[0130] 5) Let stand at 25℃ for 1 hour;

[0131] Step 2: Charging Test

[0132] 1) Let the stacked three-electrode battery cell stand at 25℃ for 30 minutes;

[0133] 2) 0.33C1 DC (constant current discharge) to discharge cutoff voltage;

[0134] 3) Let stand for 5 minutes;

[0135] 4) xC1 CC (constant current charging) to the charging cutoff voltage (the three electrodes monitor the anode potential; when the anode potential is 0V, proceed to the next step).

[0136] 5) Repeat steps 3) to 4) 9 times, with x taking the following values: 5, 4, 4.5, 3, 2, 1, 0.8, 0.5, 0.33.

[0137] 6) Take the value of x corresponding to the anode potential of 0V and the charging capacity Cx. From this, the charging window can be obtained, and the charging time can be obtained by calculating the charging window.

[0138] The following provides detailed technical descriptions of Examples 1-16 and Comparative Examples 1-5, wherein Examples 2-16 and Comparative Examples 1-5 are based on Example 1 with modifications shown in the table below. Table 1

[0139] As can be seen from the comparison of the above embodiments and comparative examples, the embodiments of the present invention significantly reduce the charging time compared to the comparative examples. In particular, the only difference between Example 2 (charging time 27.3) and Comparative Example 3 (charging time 28.6) is whether or not a fluoroether is added; similar situations occur in the comparison between Example 8 (charging time 25.1) and Comparative Example 4 (charging time 26.7), and in the comparison between Example 12 (charging time 23) and Example 14 (charging time 26.7) and Comparative Example 1 (charging time 29.1).

[0140] Although this application has been described with reference to preferred embodiments, various modifications can be made thereto and components can be replaced with equivalents without departing from the scope of this application. In particular, the technical features mentioned in the various embodiments can be combined in any manner, provided there is no structural conflict. This application is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A battery cell comprising an electrode assembly, the electrode assembly comprising a positive electrode sheet, a negative electrode sheet, a separator, and an electrolyte, wherein, The negative electrode sheet includes a negative current collector and a negative active layer disposed on at least one side of the negative current collector. The negative active layer includes a negative active material, which includes a silicon-based negative electrode material. The electrolyte includes an additive, which includes a fluorinated ether.

2. The battery cell of claim 1, wherein, The fluorinated ethers include one or more combinations of monofluorinated bis(2-fluoroethyl) ether, difluorinated bis(2-fluoroethyl) ether, trifluorinated bis(2-fluoroethyl) ether, perfluorinated bis(2,2,2-trifluoroethyl) ether, bis(difluoroethyl) ether, 2,2,2-trifluoroethyl 2-fluoroethyl ether, 1,1-difluoroethyl 2-fluoroethyl ether, monofluorinated bis(2-fluoroethyl) ether, or bis(2,2,2-trifluoroethoxy) ethane.

3. The battery cell of claim 1 or 2, wherein, The fluoroether is present in the electrolyte at a concentration of 0.3% to 2% by weight.

4. The battery cell of any one of claims 1 to 3, wherein, The electrolyte also includes lithium salts, including fluorinated lithium salts.

5. The battery cell of claim 4, wherein, The fluorinated lithium salts include one or more combinations of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium bis(trifluoromethylsulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium fluorosulfonyl-trifluorosulfonylimide, or lithium difluoro(oxalate)borate.

6. The battery cell of claim 4 or 5, wherein, The concentration of the fluorinated lithium salt in the electrolyte is 0.1–1.2 mol / L.

7. The battery cell of any one of claims 4-6, wherein, The mass ratio of the fluorinated lithium salt to the fluorinated ether is (99-90):(10-1).

8. The battery cell of any one of claims 4-7, wherein, The fluorinated lithium salt includes lithium hexafluorophosphate and / or lithium bis(fluorosulfonyl)imide, and the fluorinated ether includes monofluorinated bis(2-fluoroethyl) ether and / or 2,2,2-trifluoroethyl 2-fluoroethyl ether (TFFE).

9. The battery cell of any one of claims 1-8, wherein, The silicon content in the negative electrode active material is 9% to 65% by mass, and can be selected as 9% to 35%.

10. The battery cell of any one of claims 1 to 9, wherein, The silicon-based anode material includes silicon-carbon composite materials.

11. The battery cell of claim 10, wherein, The silicon-carbon composite material contains 35% to 70% silicon by mass.

12. The battery cell of claim 10 or 11, wherein, The average particle size of the silicon-carbon composite material is 3–15 μm.

13. The battery cell of any one of claims 1-12, wherein, The battery negative electrode active material also includes graphite.

14. The battery cell of any one of claims 1-13, wherein, The coating weight of the negative electrode active layer is 2 mg / cm 2 ~ 8 mg / cm 2 .

15. The battery cell of any one of claims 1-14, wherein, The positive electrode tab includes a positive electrode active material, the positive electrode active material including a lithium transition metal oxide having a chemical formula Li a Ni b Co c Mn d M e O 2-f ; wherein the M includes one or more elements of Al, Fe, Ti, Mg, Zr, Cr, Ga, Cu, Zn, Nb, B; The value of 'a' is any value within the range of 0.4-1.2, and can be selected as any value within the range of 0.8-1.2; the value of 'b' is any value within the range of 0.45-0.95, and can be selected as any value within the range of 0.8-0.95; the value of 'c' is any value within the range of 0.02-0.25, and can be selected as any value within the range of 0.02-0.1; the value of 'd' is any value within the range of 0.03-0.5, and can be selected as any value within the range of 0.03-0.1; the value of 'e' is any value within the range of 0-0.2, and can be selected as any value within the range of 0.001-0.1; the value of 'f' is any value within the range of 0-0.3, and can be selected as any value within the range of 0-0.

2.

16. The battery cell of any one of claims 1-15, wherein, The volumetric energy density of the battery cells ranges from 750Wh / L to 1000Wh / L.

17. A battery device comprising a plurality of battery cells, wherein, The battery cell comprises any one of claims 1 to 16.

18. An electrically powered device comprising a battery cell or battery device, wherein, The battery cell comprises any one of claims 1 to 16, and the battery device comprises the battery device of claim 17.

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