Secondary battery and device

Abstract

The present application relates to a secondary battery and a device. The secondary battery of the present application comprises a positive electrode sheet, a negative electrode sheet, and an electrolytic solution; the electrolytic solution comprises a nitrogen-containing additive and a silicon-containing and phosphorus-containing additive; the negative electrode sheet comprises a negative electrode active material layer and a solid electrolyte interface film located on the surface of the negative electrode active material layer; by testing at a sputtering etching time of 0 seconds by using an X-ray photoelectron spectrometer, the mass percentage content of a nitrogen element in the solid electrolyte interface film is a%, the mass percentage content of a silicon element in the solid electrolyte interface film is b%, and the mass percentage content of a phosphorus element in the solid electrolyte interface film is c%, wherein 5.5≤0.25a+b+0.5c≤10. Thus, the secondary battery of the present application has excellent cycle performance, fast charge performance and rate performance.

Description

Secondary battery and device

[0001] The present application claims priority to Chinese Patent Application CN202410467777.2, filed on April 18, 2024, entitled “Secondary battery and device”, the entire contents of which are incorporated herein by reference. TECHNICAL FIELD

[0002] The present application relates to the field of energy storage. In particular, the present application relates to a secondary battery and device. BACKGROUND

[0003] In recent years, lithium ion secondary batteries are increasingly widely used in the fields of mobile phones, computers, energy storage, electric tools, and electric vehicles. In the use process of lithium ion secondary batteries, faster charging speed has always been one of the goals pursued by people, and the development of fast charging technology can also alleviate the energy supplement anxiety of electric vehicle users. The lithium ion transmission speed is an important reference index for fast charging performance. From the perspective of lithium ion transmission path, the electrolyte is one of the important factors affecting the transmission speed of lithium ions in the charging and discharging process, because the electrolyte is an important medium connecting the positive and negative electrodes and an important place for lithium ion transmission. Therefore, the research on fast charging electrolyte is an important development direction of fast charging batteries.

[0004] However, the current secondary battery and device still needs to be improved. SUMMARY

[0005] The inventors found that the electrolyte additive can form a solid electrolyte interface film at the positive and negative electrode interface, and this interface film is one of the greater resistances in the lithium ion transfer process, thereby affecting the fast charging performance of the secondary battery. In addition, the electrolyte body is an important place for lithium ion transmission, and the category and content of the electrolyte additive will also affect the fast charging speed of the battery. In order to alleviate or solve at least one of the above-mentioned problems, the present application provides a secondary battery and device to solve the technical problem of slow charging speed in the prior art, which comprises a fast charging electrolyte, wherein the fast charging electrolyte comprises a nitrogen-containing additive, a silicon-containing and phosphorus-containing additive, thereby enabling the rapid transmission of lithium ions in the electrolyte body, and forming a special solid electrolyte interface film with smaller resistance at the negative electrode interface, so that lithium ions can also achieve rapid transmission at the interface film, thereby significantly improving the fast charging speed of the battery.

[0006] The secondary battery provided by the application comprises a positive electrode sheet, a negative electrode sheet and an electrolyte; the electrolyte comprises a nitrogen-containing additive, a silicon-containing additive and a phosphorus-containing additive; the negative electrode sheet comprises a negative electrode active material layer and a solid electrolyte interface film on the surface of the negative electrode active material layer; the mass percentage content of nitrogen in the solid electrolyte interface film is a% when the sputtering etching time is 0 seconds, the mass percentage content of silicon in the solid electrolyte interface film is b%, and the mass percentage content of phosphorus in the solid electrolyte interface film is c%; wherein, 6≤0.25a+b+0.5c≤10.

[0007] The application also provides a device comprising the secondary battery described above.

[0008] The application has the following advantages:

[0009] The secondary battery provided by the application adds a nitrogen-containing additive, a silicon-containing additive and a phosphorus-containing additive to the electrolyte and controls the content of nitrogen, silicon and phosphorus in the solid electrolyte interface film (SEI film) on the surface of the negative electrode active material layer. On the one hand, the fast-charging electrolyte can make lithium ions transmit quickly in the electrolyte, thereby improving the fast-charging speed. On the other hand, the control of the content of nitrogen, silicon and phosphorus in the SEI film improves the inorganic component ratio and structural uniformity of the SEI film, significantly reduces the transmission resistance of lithium ions in the SEI film, thereby significantly reduces the impedance of the SEI film, realizes the quick transmission of lithium ions in the SEI film, and thus significantly improves the fast-charging speed of the battery and improves the rate performance of the battery. Based on the above improvements, the secondary battery provided by the application has at least one of the following advantages: excellent cycle performance, fast-charging performance and rate performance. BRIEF DESCRIPTION OF DRAWINGS

[0010] FIG. 1 is a sub-peak spectrum of nitrogen in the XPS spectrum of the SEI film of the negative electrode sheet according to an embodiment of the application.

[0011] FIG. 2 is a sub-peak spectrum of silicon in the XPS spectrum of the SEI film of the negative electrode sheet according to an embodiment of the application.

[0012] FIG. 3 is a sub-peak spectrum of phosphorus in the XPS spectrum of the SEI film of the negative electrode sheet according to an embodiment of the application. DETAILED DESCRIPTION

[0013] For the sake of brevity, only some numerical ranges are specifically disclosed herein. However, any lower limit can be combined with any upper limit to create a range not expressly recited; and any lower limit can be combined with any other lower limit to create a range not expressly recited, and likewise any upper limit can be combined with any other upper limit to create a range not expressly recited. Further, each individual disclosed point or single numerical value can be combined with any other point or single numerical value to create a range not expressly recited, either as a lower limit or an upper limit.

[0014] Unless otherwise indicated, the terms used in this application have their common meaning as understood by those skilled in the art. Unless otherwise indicated, the values of the parameters mentioned in this application can be measured using various measuring methods commonly used in the art (for example, can be tested according to the methods given in the examples of this application).

[0015] The use of the terms "at least one", "at least one of', "at least one of the', or other similar phrases as used herein is intended to mean any one of the items in the list. For example, if a list of items includes A and B, then the phrase "at least one of A and B" means A alone; B alone; or both A and B. In another example, if a list of items includes A, B, and C, then the phrase "at least one of A, B, and C" means A alone; B alone; C alone; A and B (excluding C); A and C (excluding B); B and C (excluding A); or all of A, B, and C. Item A can include a single component or multiple components. Item B can include a single component or multiple components. Item C can include a single component or multiple components.

[0016] The term "C1-C3 alkyl" includes, but is not limited to, methyl, ethyl, n-propyl, isopropyl, cyclopropyl, and the like.

[0017] The term "C3-C6 alkylsilyl" refers to a silyl group having 3 to 6 carbon atoms, including, but not limited to, trimethylsilyl and the like.

[0018] The term "C2-C3 alkenyl" includes, but is not limited to, ethenyl, propenyl, and the like.

[0019] The term "C6-C12 aryl" includes, but is not limited to, phenyl or naphthyl, and the like.

[0020] The term "substituted or unsubstituted" means that the functional group recited in the term after "substituted or unsubstituted" can or can not have a substituent. For example, "substituted or unsubstituted C1-C3 alkyl" means C1-C3 alkyl having a substituent or unsubstituted C1-C3 alkyl. The number of substituents can be one or more than two, and the substituents include at least one of halogen (e.g., fluorine), alkyl, or aryl. It should be understood that when the number of substituents is more than one, each substituent can be the same or different.

[0021] The present application will be further described in conjunction with specific embodiments. It should be understood that these specific embodiments are only used to illustrate but not to limit the scope of the present application.

[0022] A secondary battery

[0023] The secondary battery provided by the present application comprises a positive electrode sheet, a negative electrode sheet and an electrolyte; the electrolyte comprises a nitrogen-containing additive, a silicon-containing additive and a phosphorus-containing additive; the negative electrode sheet comprises a negative electrode active material layer and a solid electrolyte interface film on the surface of the negative electrode active material layer; the mass percentage content of nitrogen element in the solid electrolyte interface film is a% and the mass percentage content of silicon element in the solid electrolyte interface film is b% and the mass percentage content of phosphorus element in the solid electrolyte interface film is c% when tested by X-ray photoelectron spectrometer at a sputtering etching time of 0 seconds; wherein 6≤0.25a+b+0.5c≤10.

[0024] Therefore, the secondary battery of the present application can achieve the following advantages at least one of which: excellent cycle performance, fast charging performance and rate performance by adding the nitrogen-containing additive, the silicon-containing additive and the phosphorus-containing additive in the electrolyte and controlling the content of nitrogen element, silicon element and phosphorus element in the solid electrolyte interface film (SEI film) on the surface of the negative electrode active material layer. On the one hand, the fast charging electrolyte can make lithium ions transmit rapidly in the electrolyte, thereby improving the fast charging speed; on the other hand, the control of the content of nitrogen element, silicon element and phosphorus element in the SEI film improves the inorganic component ratio and structural uniformity of the SEI film, significantly reduces the transfer resistance of lithium ions in the SEI film, thereby significantly reduces the impedance of the SEI film, realizes the rapid transmission of lithium ions in the SEI film, and thus significantly improves the fast charging speed of the battery and improves the rate performance of the battery.

[0025] In some embodiments, the solid electrolyte interface film has a mass percentage content of nitrogen element a%, a mass percentage content of silicon element b%, and a mass percentage content of phosphorus element c%, wherein 6≤0.25a+b+0.5c≤10, when tested by X-ray photoelectron spectrometer at a sputtering etching time of 0 seconds. In some embodiments, 0.25a+b+0.5c is 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5, 10, or any value therebetween. In some embodiments, 7≤0.25a+b+0.5c≤9. In this way, the organic and inorganic components in the SEI film can be reasonably proportioned, so that the SEI film has a loose and porous structure, the lithium ions can quickly pass through the interface, and the fast charging performance is achieved. When the value of 0.25a+b+0.5c is too large, the SEI film is difficult to maintain a stable state, the electrolyte continuously generates side reactions, a large amount of solid by-products are accumulated at the SEI film interface, the transmission resistance of lithium ions is increased, and the fast charging performance is reduced. When the value of 0.25a+b+0.5c is too small, the SEI film is relatively dense, the transmission resistance of lithium ions is increased, and the fast charging performance is reduced.

[0026] In some embodiments, the solid electrolyte interface film has a mass percentage content of nitrogen element a%, 2≤a≤13. In some embodiments, a is 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, or any value therebetween. In some embodiments, 4≤a≤8. In this way, a loose and porous and stable SEI film interface structure can be formed, which is beneficial for the rapid transmission of lithium ions. When the value of a is too large (e.g., too much LiFSI), the current collector generates more side reactions, forming by-products that hinder the transmission of lithium ions. When the value of a is too small (e.g., too little LiFSI), the transmission resistance of lithium ions in the electrolyte bulk is increased, and the fast charging speed is reduced.

[0027] In some embodiments, the solid electrolyte interface film has a mass percentage content of silicon element b%, 0.01≤b≤4. In some embodiments, b is 0.01, 0.1, 0.5, 1, 2, 3, 4, or any value therebetween. In some embodiments, 1≤b≤3. In this way, a loose and porous and stable SEI film interface structure can be formed, which is beneficial for the rapid transmission of lithium ions. When the value of b is too large, the SEI film is unstable, the newly added particle surface induces the electrolyte to continuously generate side reactions, a large amount of solid by-products are accumulated at the SEI film interface, the transmission resistance of lithium ions is increased, and the fast charging performance is reduced. When the value of b is too small, the SEI film is relatively dense, the transmission resistance of lithium ions is increased, and the fast charging performance is reduced.

[0028] In some embodiments, the content of phosphorus in the solid electrolyte interface film is c%, 0.01≤c≤15. In some embodiments, c is 0.01, 0.1, 0.5, 1, 2, 3, 4, 6, 8, 10, 12, 15, or any value therebetween. In some embodiments, 3≤c≤10. In this way, a loose, porous, and stable SEI film interface structure can be formed, which is conducive to the rapid passage of lithium ions. When the value of c is too large, the SEI film will be unstable, the newly added particle surface will induce the continuous side reaction of the electrolyte, the SEI film interface will accumulate a large amount of solid byproducts, and the transmission resistance of lithium ions will be increased, thereby reducing the fast charging performance. When the value of c is too small, the SEI film will be relatively dense, the transmission resistance of lithium ions will also be increased, and the fast charging performance will also be reduced.

[0029] In some embodiments, the nitrogen-containing additive includes at least one of lithium fluorosulfonylimide, lithium bis(trifluoromethylsulfonyl)imide (LiTFSI), lithium (fluorosulfonyl)(trifluoromethylsulfonyl)imide, lithium (fluorosulfonyl)(perfluorobutylsulfonyl)imide, lithium (trifluoromethylsulfonyl)(perfluorobutylsulfonyl)imide (LiFNFSI), and lithium bis(pentafluoroethylsulfonyl)imide (LiBETI). In this way, the lithium fluorosulfonylimide is an imide lithium salt with nitrogen as the central atom, which can improve the fast charging performance of the battery and significantly improve the rate performance of the battery.

[0030] In some embodiments, the nitrogen-containing additive includes lithium fluorosulfonylimide (LiFSI). Since the anion radius of LiFSI is large, it is easier to dissociate lithium ions, thereby significantly improving the conductivity of the battery, thereby improving the fast charging performance of the battery, and also improving the rate performance, safety, and high-temperature cycle stability of the secondary battery.

[0031] In some embodiments, the content of the nitrogen-containing additive is 3% to 15% by mass based on the mass of the electrolyte. In some embodiments, the content of the nitrogen-containing additive is 3%, 4%, 5%, 7%, 9%, 10%, 12%, 15%, or any value therebetween. In some embodiments, the content of the nitrogen-containing additive is 5% to 10%.

[0032] In some embodiments, the silicon-containing and phosphorus-containing additive includes at least one of the compounds shown in Formula I and Formula II:

[0033] wherein, in formula I and formula II, R3, R4, R5, R6, R7, R8are each independently selected from substituted or unsubstituted C1-C3alkyl, substituted or unsubstituted C3-C6alkylsilyl, substituted or unsubstituted C2-C3alkenyl, or substituted or unsubstituted C6-C12aryl; wherein, in formula I, there is at least one substituted or unsubstituted C3-C6alkylsilyl, and in formula II, there is at least one substituted or unsubstituted C3-C6alkylsilyl, each of the substituents is independently selected from fluorine.

[0034] In some embodiments, formula I is a silicon-containing phosphonate additive, and formula II is a silicon-containing phosphite additive. Thus, the above-mentioned phosphorus-containing additive can reduce the impedance of the interface between the positive and negative electrodes, and improve the power performance of the battery. In addition, the use of the above-mentioned nitrogen-containing additive together with the above-mentioned silicon-containing and phosphorus-containing additives can further improve the stability of the SEI film and improve the cycle performance and rate performance of the secondary battery.

[0035] In some embodiments, the silicon-containing and phosphorus-containing additive includes at least one of tris(trimethylsilyl)phosphite (TMSP) and tris(trimethylsilyl)phosphite (TMSPi). In some embodiments, the silicon-containing and phosphorus-containing additive includes tris(trimethylsilyl)phosphite (TMSP). Thus, the stability of the SEI film can be further improved, and the cycle performance of the battery can be improved.

[0036] In some embodiments, the mass percentage content of the silicon-containing and phosphorus-containing additive is 0.01% to 2% based on the mass of the electrolyte. In some embodiments, the mass percentage content of the silicon-containing and phosphorus-containing additive is 0.01%, 0.1%, 0.3%, 0.5%, 0.7%, 0.9%, 1%, 1.1%, 1.3%, 1.5%, 1.7%, 1.9%, 2%, or any value therebetween. In some embodiments, the mass percentage content of the phosphorus-containing additive is 0.5% to 2%.

[0037] In some embodiments, the solid electrolyte interface film is a non-artificial film. In some embodiments, the solid electrolyte interface film (SEI film) is formed by a solid product generated by the reaction of a specific component in the electrolyte at a specific voltage. In some embodiments, the nitrogen element in the solid electrolyte interface film comes from the nitrogen-containing additive, and the silicon element and the phosphorus element in the solid electrolyte interface film come from the silicon-containing and phosphorus-containing additive.

[0038] In some embodiments, the mass percentage content of the nitrogen element, the silicon element, and the phosphorus element in the solid electrolyte interface film refers to the mass percentage content of the corresponding element obtained by testing with an X-ray photoelectron spectrometer at a sputtering etching time of 0 seconds on the surface of the negative active material layer.

[0039] In some embodiments, the electrolyte further comprises a first additive, the first additive comprising at least one of a cyclic carbonate containing a carbon-carbon double bond, a fluorine-containing cyclic carbonate, a fluorine-containing phosphate, and an oxalate borate. In some embodiments, the first additive comprises at least one of vinylene carbonate (VC), fluoroethylene carbonate (FEC), lithium difluorophosphate (LiDFP), lithium difluoro oxalato borate (LiDFOB), and lithium bisoxalato borate (LiBOB).

[0040] In some embodiments, the first additive has a mass percentage content of 0.05% to 10% based on the mass of the electrolyte. In some embodiments, the first additive has a mass percentage content of 0.05%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 6%, 7%, 8%, 9%, 10%, or any value therebetween. In some embodiments, the first additive has a mass percentage content of 0.1% to 5%.

[0041] In some embodiments, the electrolyte further comprises a lithium salt, the lithium salt comprising at least one of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium trifluorosulfonyl (LiTf), and lithium bis(fluoromalonato)borate (LiBFMB).

[0042] In some embodiments, the lithium salt has a mass percentage content of 0.05% to 20% based on the mass of the electrolyte. In some embodiments, the lithium salt has a mass percentage content of 0.05%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, or any value therebetween. In some embodiments, the lithium salt has a mass percentage content of 1% to 15%.

[0043] In some embodiments, the electrolyte further comprises a solvent, the solvent comprising at least one of a chain carbonate, a cyclic carbonate, and a carboxylic acid ester.

[0044] In some embodiments, the chain carbonate is selected from at least one of dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, and a fluorinated chain carbonate. In some embodiments, the cyclic carbonate comprises at least one of ethylene carbonate (EC), propylene carbonate, and butylene carbonate. In some embodiments, the carboxylic acid ester is selected from at least one of methyl formate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, gamma-butyrolactone, and a fluorinated carboxylic acid ester.

[0045] In some embodiments, the solvent has a mass percentage content of 0.05% to 80% based on the mass of the electrolyte. In some embodiments, the solvent has a mass percentage content of 0.05%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 6%, 7%, 8%, 9%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, or any value therebetween. In some embodiments, the solvent has a mass percentage content of 20% to 70%.

[0046] In some embodiments, the positive electrode tab includes a positive electrode active material layer including a positive electrode active material, the positive electrode active material including a lithium nickel transition metal oxide.

[0047] In some embodiments, the lithium nickel transition metal oxide includes LiNi x M 1-x O2, M includes at least one of cobalt, manganese, iron, chromium, titanium, zinc, vanadium, aluminum, zirconium, cerium, magnesium, calcium, molybdenum, strontium, tungsten, yttrium, lanthanum, silver, niobium, copper, and barium, 0.7≤x≤0.98. It can be understood that all transition metal elements in the positive electrode active material include the transition element nickel element (Ni) and other transition elements M. The molar percentage content of the nickel element is based on the proportion of the total amount of all transition metal elements (including the transition element Ni and other transition elements M) in the positive electrode active material.

[0048] In some embodiments, x is 0.7, 0.72, 0.74, 0.76, 0.78, 0.8, 0.82, 0.84, 0.86, 0.88, 0.9, 0.92, 0.94, 0.96, 0.98, or any value therebetween.

[0049] In some embodiments, the positive electrode active material includes at least one of lithium nickel oxide, lithium nickel cobalt aluminum oxide, lithium nickel cobalt manganese oxide, lithium nickel manganese cobalt magnesium oxide, and lithium nickel manganese oxide.

[0050] In some embodiments, the positive electrode active material layer further includes a binder, and optionally, a conductive material. The binder improves the binding between the positive electrode active material particles to each other, and also improves the binding between the positive electrode active material and the current collector.

[0051] In some embodiments, the binder includes polyvinylidene fluoride (PVDF), polyacrylonitrile (PAN), polyacrylic acid (PAA), polymethyl methacrylate (PMMA), polyimide (PI), polyvinyl alcohol, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polymeric ethylene oxide, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, poly-p-1,1- difluoroethylene, polyethylene, polypropylene, styrene butadiene rubber, acrylated styrene butadiene rubber, epoxy resin, or nylon, etc.

[0052] In some embodiments, the conductive material includes carbon-based material, metal-based material, conductive polymer, and mixtures thereof. In some embodiments, the carbon-based material is selected from natural graphite, artificial graphite, carbon black, acetylene black, ketjen black, carbon fiber, or any combination thereof. In some embodiments, the metal-based material is selected from metal powder, metal fiber, copper, nickel, aluminum, or silver. In some embodiments, the conductive polymer is polyphenylene derivative.

[0053] In some embodiments, the positive electrode tab further includes a positive electrode current collector, which can be a metal foil or a composite current collector. For example, an aluminum foil can be used. The composite current collector can be obtained by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer substrate.

[0054] In some embodiments, the negative electrode tab includes a negative electrode active material layer and a solid electrolyte interface film on the surface of the negative electrode active material layer.

[0055] In some embodiments, the negative electrode active material layer includes a negative electrode active material, which includes a silicon-based material and a mixture of at least one material selected from a carbon-based material, a tin-based material, a phosphorus-based material, and metallic lithium.

[0056] In some embodiments, the silicon-based material includes at least one of silicon, silicon alloy, silicon oxide compound, and silicon carbon compound. In some embodiments, the carbon-based material includes at least one of graphite, soft carbon, hard carbon, carbon nanotube, and graphene. In some embodiments, the tin-based material includes at least one of tin, tin oxide, and tin alloy. In some embodiments, the phosphorus-based material includes phosphorus and / or phosphorus compound.

[0057] In some embodiments, the mass percentage content of the silicon-based material is 3% to 40% based on the mass of the negative electrode active material. In some embodiments, the mass percentage content of the silicon-based material is 3%, 5%, 8%, 10%, 12%, 15%, 18%, 20%, 25%, 30%, 35%, 40%, or any value therebetween.

[0058] In some embodiments, the negative active material layer further comprises a binder and a conductive agent. In some embodiments, the binder comprises: styrene butadiene rubber (SBR), sodium carboxymethyl cellulose (CMC), polyacrylic acid (PAA), polyvinyl alcohol, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene oxide-containing polymer, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, acrylic acid (ester) butadiene rubber, epoxy resin, or nylon, etc.

[0059] In some embodiments, the conductive agent comprises: carbon-based material, metal-based material, conductive polymer, and mixtures thereof. In some embodiments, the carbon-based material is selected from natural graphite, artificial graphite, carbon black, acetylene black, ketjen black, carbon fiber, or any combination thereof. In some embodiments, the metal-based material is selected from metal powder, metal fiber, copper, nickel, aluminum, or silver. In some embodiments, the conductive polymer is a polyphenylene derivative.

[0060] In some embodiments, the negative electrode tab further comprises a negative current collector, which comprises: copper foil, nickel foil, stainless steel foil, titanium foil, foamed nickel, foamed copper, polymer substrate coated with conductive metal, or any combination thereof.

[0061] In some embodiments, a separator is provided between the positive electrode tab and the negative electrode tab to prevent short circuit. The material and shape of the separator that can be used in the embodiments of the present application are not particularly limited, and it can be any technology disclosed in the prior art. In some embodiments, the separator comprises a polymer or inorganic substance formed of a material stable to the electrolyte of the present application, etc.

[0062] For example, the separator can comprise a substrate layer and a surface treatment layer. The substrate layer is a non-woven fabric, a film, or a composite film having a porous structure, and the material of the substrate layer comprises at least one of polyethylene, polypropylene, polyethylene terephthalate, or polyimide. Specifically, a polypropylene porous film, a polyethylene porous film, a polypropylene non-woven fabric, a polyethylene non-woven fabric, or a polypropylene-polyethylene-polypropylene porous composite film can be used.

[0063] A surface treatment layer is provided on at least one surface of the substrate layer, and the surface treatment layer can be a polymer layer or an inorganic layer, or a layer formed by mixing a polymer and an inorganic substance.

[0064] The inorganic layer includes inorganic particles and a binder. The inorganic particles include at least one of alumina, silica, magnesia, titania, hafnia, tin oxide, ceria, nickel oxide, zinc oxide, calcium oxide, zirconia, yttria, silicon carbide, boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide, or barium sulfate. The binder includes at least one of polyvinylidene fluoride, a copolymer of vinylidene fluoride-hexafluoropropylene, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyvinyl ether, polymethyl methacrylate, polytetrafluoroethylene, or polyhexafluoropropylene.

[0065] The polymer layer includes a polymer. The polymer includes at least one of polyamide, polyacrylonitrile, acrylate polymer, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyvinyl ether, polyvinylidene fluoride, or poly(vinylidene fluoride-hexafluoropropylene).

[0066] In some embodiments, the method of manufacturing the secondary battery includes providing an electrode assembly, injecting a liquid electrolyte, encapsulating, and formation. In some embodiments, the formation is performed at a temperature of 40-50°C, for example, 41°C, 42°C, 43°C, 44°C, 45°C, 46°C, 47°C, 48°C, or 49°C.

[0067] In some embodiments, the formation includes charging at a temperature of 40-50°C, for example, 45°C, at a pressure of 150-250 kgf, for example, 210 kgf, at a current of 0.05C to 4.25V, standing for 60 minutes, then charging at a current of 0.1C to 4.25V, and then discharging at a current of 0.2C to 3.0V.

[0068] In some embodiments, the secondary battery is formed. In some embodiments, the solid electrolyte interface film is formed after the formation of the secondary battery. The nitrogen-containing additive, the silicon-containing additive, and the phosphorus-containing additive are reduced on the surface of the negative active material to form the SEI film during the formation of the secondary battery. After the secondary battery is cycled for a plurality of times, the absolute content of each of nitrogen, silicon, and phosphorus in the SEI film is different from the absolute content of each of nitrogen, silicon, and phosphorus in the SEI film after the formation, but the relative content, i.e., the mass percentage content of each of nitrogen, silicon, and phosphorus in the SEI film, is still between 2-12%, 0.01-4%, and 0.01-15%, respectively.

[0069] In some embodiments, the secondary battery is a lithium secondary battery or a sodium secondary battery. In some embodiments, the lithium secondary battery includes a lithium metal secondary battery, a lithium ion secondary battery, a lithium polymer secondary battery, or a lithium ion polymer secondary battery.

[0070] In some embodiments, the secondary battery can include an outer package, which can be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer package of the secondary battery can also be a soft package, such as a pouch soft package. The material of the soft package can be plastic, such as one or more of polypropylene (PP), polybutylene terephthalate (PBT), polybutylene succinate (PBS), etc.

[0071] In some embodiments, the shape of the secondary battery is not particularly limited, which can be cylindrical, square, or any other shape.

[0072] In some embodiments, the present application also provides a battery module. The battery module includes the above-mentioned secondary battery. The battery module of the present application adopts the above-mentioned secondary battery, and thus has at least the same advantages as the secondary battery. The number of secondary batteries contained in the battery module of the present application can be multiple, and the specific number can be adjusted according to the application and capacity of the battery module.

[0073] In some embodiments, the present application also provides a battery pack, which includes the above-mentioned battery module. The number of battery modules contained in the battery pack can be adjusted according to the application and capacity of the battery pack.

[0074] II. Device

[0075] The present application also provides a device, which includes the above-mentioned secondary battery.

[0076] In some embodiments, the device includes an electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, a power storage system, etc. In order to meet the high power and high energy density requirements of the secondary battery for the device, a battery pack or a battery module can be used.

[0077] In other embodiments, the device can be a mobile phone, a tablet computer, a notebook computer, etc. The device usually requires thinning, and a secondary battery can be used as a power source.

[0078] Examples and Comparative Examples

[0079] Example 1

[0080] The preparation steps of the positive electrode tab are as follows: the positive electrode active material LiNi 0.9 Co 0.06 Mn 0.04 O2, CNT (conductive agent carbon nanotube) / acetylene black, binder polyvinylidene fluoride PVDF, in a weight ratio of LiNi 0.9 Co 0.06 Mn 0.04O2: CNT / Acetylene black: PVDF = 95: (2.0 / 1.0):2 in N-methyl pyrrolidone NMP, after being fully homogenized, coated on a 12 μm thick aluminum current collector, followed by drying, rolling, hot pressing and other steps to obtain a positive electrode sheet.

[0081] The preparation steps of the negative electrode sheet are as follows: the negative active material silicon oxide (SiOx, 0.5≤x≤1.5)-graphite composite (Si / C = 14:86), conductive agent acetylene black, binder styrene-butadiene rubber SBR, thickening agent sodium carboxymethyl cellulose CMCNa, polyacrylic acid PAA are added into deionized water in a weight ratio of 95:2:1.5:1:0.5, after being fully homogenized, coated on an 8 μm thick copper current collector, followed by drying, rolling, hot pressing and other steps to obtain a negative electrode sheet.

[0082] Preparation of electrolyte: in an argon-filled glove box (H2O < 0.1 ppm, O2 < 0.1 ppm), lithium salt LiPF6 is fully dissolved in a mixed solution of EC / DMC / EMC (ethylene carbonate / diethyl carbonate / methyl ethyl carbonate) = 20 / 70 / 10, configured into a solution with a mass percentage of lithium salt LiPF6 of 1.5%, followed by the addition of 15% of nitrogen-containing additive lithium bisfluorosulfonylimide (LiFSI) and 2% of silicon- and phosphorus-containing additive tris(trimethylsilyl) phosphate (TMSP), and then the addition of second additives 8% of fluoroethylene carbonate (FEC) and 0.5% of vinylene carbonate (VC), after being stirred uniformly, an electrolyte is obtained.

[0083] Separator: a PP / PE / PP (polypropylene / polyethylene / polypropylene) three-layer composite separator is used.

[0084] Preparation of lithium ion secondary battery: the above-prepared positive electrode sheet, separator (PP / PE / PP three-layer composite film) and negative electrode sheet are overlapped in turn, with the separator being in the middle of the positive electrode sheet and negative electrode sheet, and a bare cell is obtained by winding, and after being fully dried, the bare cell is placed in a cylindrical (for example, 18650 cylindrical) steel shell, followed by the injection of the above-prepared electrolyte and sealing, and after the battery is subjected to pre-charging, high-temperature infiltration, formation (formation conditions are: temperature 45℃, 0.05C current charging to 3V, then standing for 5min, followed by 0.1C charging to 3.5V, then standing for 5min, and then 0.33C charging to 4.0V) and high-temperature aging, normal partitioning is performed.

[0085] Examples 2-7 and Comparative Examples 1-3

[0086] Examples 2-7 and Comparative Examples 1-3 are realized on the basis of Example 1 by adjusting the types and contents of lithium salt, solvent and additive in the electrolyte, and the specific adjustment measures and detailed data are shown in Table 1.

[0087] Table 1

[0088] Test method

[0089] 1. X-ray photoelectron spectroscopy (XPS) test

[0090] The lithium ion battery is discharged to 2.5V at a current of 0.1C, and the electrode sheet is obtained by disassembling the lithium ion battery in an argon-filled glove box. The obtained electrode sheet is cut into a test sample with a size of 8mmx8mm, and is soaked and cleaned with a low-boiling-point dimethyl carbonate (DMC) solvent for half an hour. After drying completely, the test sample is pasted on the sample table of the XPS, with the surface of the negative active material layer away from the current collector facing upward, and the measurement is carried out without exposure to the atmosphere. The specific test conditions and steps are as follows:

[0091] The single crystal spectrum AlKα ray is used, and for the X-ray point, the elliptical form with an output of 10KV and 22mA of 1000x1750μm is used, the data at a sputtering etching time of 0 seconds is selected, for neutral carbon C1s, 284.8eV is used, and for data processing such as peak differentiation, 3-point smoothing, peak area measurement, background subtraction and peak synthesis are used to calculate the atoms of each component.

[0092] For example, the mass percentage content of nitrogen element, silicon element and phosphorus element in the SEI film of the negative electrode sheet can be obtained by the above test method. More specifically, FIGS. 1-3 are XPS spectra of nitrogen element, silicon element and phosphorus element obtained by testing the SEI film of the negative electrode sheet in Example 1, wherein the peak area in the spectrum is integrated and calculated, the peak area of each element can be obtained, and the mass percentage content of the corresponding element is calculated by normalization according to the peak area of each element.

[0093] 2. Impedance (DCR) test

[0094] In an environment of 25±2℃, the lithium ion secondary battery is static for 5 minutes, charged to 4.2V at 0.5C, static for 5 minutes, discharged to 50% SOC at 0.5C, static for 60 minutes, the end potential is recorded as V1, 2C pulse charging for 10 seconds, the end potential is recorded as V2, static for 5 minutes, the 2C charging current is A, then DCR=(V1-V2) / A.

[0095] 3. 4C rate charge capacity retention test

[0096] 25±2℃ environment, lithium ion secondary battery is static for 5 minutes, 0.5C discharge to 2.5V, static for 5 minutes, 0.5C charge to 4.2V, static for 5 minutes, record the charge capacity as C0; 0.5C discharge to 2.5V, static for 5 minutes, 4C charge to 4.2V, static for 5 minutes, record the charge capacity as C1; then the 4C rate charge capacity retention rate A=C1 / C0.

[0097] 4, electrolyte conductivity test

[0098] 25±2℃ environment, take the above prepared electrolyte, using conductivity meter for testing.

[0099] Test results

[0100] Table 2

[0101] From examples 1-7, comparative examples 1-3, the fast charging type electrolyte can make lithium ion transport in electrolyte quickly, and further improve the fast charging speed; and by controlling the content of nitrogen element, silicon element and phosphorus element in SEI film, the inorganic component ratio and structure uniformity of SEI film are improved, the transfer resistance of lithium ion in SEI film is significantly reduced, and the impedance of SEI film is significantly reduced, so as to realize the rapid transmission of lithium ion in SEI film, thereby significantly improving the fast charging speed of battery and improving the rate performance of battery. Based on the above improvement, the secondary battery of the application has at least one of the following advantages: excellent fast charging performance and rate performance.

[0102] Comparative example 1 and examples 1-7, because of not adding silicon-containing and phosphorus-containing additive TMSP, the content of silicon element in SEI film is not detected, and the value of 0.25a+b+0.5c is too small, so that the SEI film is denser, the transfer resistance of lithium ion is increased, the battery impedance is significantly increased, the fast charging performance is poor, and the capacity retention rate is also significantly reduced.

[0103] Comparative example 2 and examples 1-7, because of not adding nitrogen-containing additive LiFSI, the content of nitrogen element in SEI film is not detected, and the content of phosphorus element in SEI film is too large, so that the value of 0.25a+b+0.5c is too large, so that the SEI film has poor stability, and a large amount of solid by-products will be accumulated in the interface, increasing the transfer resistance of lithium ion, the battery impedance is significantly increased, the fast charging performance is poor, and the capacity retention rate is also significantly reduced.

[0104] Comparative example 3 and examples 1-7, because the value of 0.25a+b+0.5c is too small, the SEI film is denser, the transfer resistance of lithium ion is increased, the battery impedance is significantly increased, the fast charging performance is poor, and the capacity retention rate is also significantly reduced.

[0105] While certain example embodiments have been shown and described, the application is not limited to the disclosed embodiments. Rather, persons of ordinary skill in the art will recognize that modifications and changes can be made to the described embodiments without departing from the spirit and scope of the application as described in the claims.

Claims

1. A secondary battery characterized by comprising: The positive electrode tab, the negative electrode tab and the electrolyte solution; The electrolyte solution comprises a nitrogen-containing additive, a silicon-containing and phosphorus-containing additive; The negative electrode tab comprises a negative electrode active material layer and a solid electrolyte interface film on the surface of the negative electrode active material layer; The mass percentage content of nitrogen in the solid electrolyte interface film is a% when the sputtering etching time is 0 seconds, the mass percentage content of silicon in the solid electrolyte interface film is b%, and the mass percentage content of phosphorus in the solid electrolyte interface film is c%; 5.5≤0.25a+b+0.5c≤10.

2. The secondary battery according to claim 1, characterized by 6≤0.25a+b+0.5c≤8.

3. The secondary battery according to claim 1 or 2, characterized by 2≤a≤13。 4. The secondary battery according to claim 1 or 2, characterized by 0.01≤b≤4。 5. The secondary battery according to claim 1 or 2, characterized by 0.01≤c≤15。 6. The secondary battery according to claim 3, characterized by 4≤a≤8。 7. The secondary battery according to claim 4, characterized by 1≤b≤3。 8. The secondary battery according to claim 5, characterized by 3≤c≤10。 9. The secondary battery according to claim 1 or 2, characterized by The nitrogen-containing additive comprises lithium fluorosulfonylimide, and the lithium fluorosulfonylimide comprises at least one of lithium bisfluorosulfonylimide, lithium bis-trifluoromethylsulfonylimide, lithium (fluorosulfonyl)(trifluoromethylsulfonyl)imide, lithium (fluorosulfonyl)(perfluorobutylsulfonyl)imide, lithium (trifluoromethylsulfonyl)(perfluorobutylsulfonyl)imide and lithium bis(pentafluoroethylsulfonyl)imide.

10. The secondary battery according to claim 1 or 2, characterized by The silicon-containing and phosphorus-containing additives include at least one of the compounds shown in Formula I and Formula II: In formula I and formula II, R3, R4, R5, R6, R7, R8 are each independently selected from substituted or unsubstituted C1-C3 alkyl, substituted or unsubstituted C3-C6 alkylsilyl, substituted or unsubstituted C2-C3 alkenyl or substituted or unsubstituted C6-C12 aryl; at least one of the substituted or unsubstituted C3-C6 alkylsilyl in formula I and formula II is selected from fluorine.

11. The secondary battery according to claim 9, characterized by The nitrogen-containing additive comprises lithium bisfluorosulfonylimide.

12. The secondary battery according to claim 10, characterized by The silicon-containing and phosphorus-containing additive comprises at least one of tris(trimethylsilyl) phosphate and tris(trimethylsilyl) phosphite.

13. The secondary battery according to claim 1, characterized by The solid electrolyte interface film is a non-artificial film.

14. The secondary battery according to claim 1 or 2, characterized by The mass percentage content of the nitrogen-containing additive is 3% to 15% based on the mass of the electrolyte solution; The mass percentage content of the silicon-containing and phosphorus-containing additive is 0.01% to 2% based on the mass of the electrolyte solution.

15. The secondary battery according to claim 1 or 2, characterized by The electrolyte solution further comprises a second additive, and the second additive comprises at least one of a cyclic carbonate containing a carbon-carbon double bond, a fluorine-containing cyclic carbonate, a fluorine-containing phosphate and oxalate borate; the mass percentage content of the second additive is 0.05% to 10% based on the mass of the electrolyte solution.

16. The secondary battery according to claim 1 or 2, characterized by The electrolyte solution further comprises a lithium salt, and the lithium salt comprises at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium trifluorosulfonyl and lithium bis(fluoromalonate) borate; the mass percentage content of the lithium salt is 0.05% to 20% based on the mass of the electrolyte solution.

17. The secondary battery according to claim 1 or 2, characterized by The electrolyte solution further comprises a solvent, and the solvent comprises at least one of a chain carbonate, a cyclic carbonate and a carboxylic acid ester; the mass percentage content of the solvent is 0.05% to 80% based on the mass of the electrolyte solution.

18. The secondary battery according to claim 1 or 2, characterized by The solid electrolyte interface film is formed by the reaction of the negative electrode active material and the electrolyte solution.

19. The secondary battery according to claim 1 or 2, characterized by The positive electrode sheet includes a positive electrode active material layer including a positive electrode active material including a lithium nickel transition metal oxide including LiNi x M 1-x at least one of cobalt, manganese, iron, chromium, titanium, zinc, vanadium, aluminum, zirconium, cerium, magnesium, calcium, molybdenum, strontium, tungsten, yttrium, lanthanum, silver, niobium, copper, and barium, 0.7≤x≤0.98; and / or The negative electrode active material layer comprises a negative electrode active material, the negative electrode active material comprises a mixture of a silicon-based material and at least one material selected from a carbon-based material, a tin-based material, a phosphorus-based material, and lithium metal; wherein the silicon-based material comprises at least one of silicon, a silicon alloy, a silicon oxide compound, and a silicon carbon compound, the carbon-based material comprises at least one of graphite, soft carbon, hard carbon, a carbon nanotube, and graphene, the tin-based material comprises at least one of tin, a tin oxide, and a tin alloy, and the phosphorus-based material comprises phosphorus and / or a phosphorus-carbon compound; the mass percentage content of the silicon-based material is 3% to 40% based on the mass of the negative electrode active material; and / or The secondary battery is subjected to formation.

20. An apparatus comprising: The secondary battery comprises the secondary battery according to any one of claims 1 to 19.

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