Secondary battery, battery module, battery pack, and power consumption device

Abstract

The present application provides a secondary battery, a battery module, a battery pack, and a power consumption device. The secondary battery includes a positive electrode sheet including a positive electrode film layer, a negative electrode sheet including a negative electrode film layer, an electrolytic solution, and a solid electrolyte, the solid electrolyte is provided on the surface of the positive electrode film layer and / or the negative electrode film layer and includes a polymer matrix and a first additive, the first additive is arranged to form an interfacial film on the surface of the positive electrode film layer and / or the negative electrode film layer, where the mass percentage of the polymer matrix relative to the total mass of the solid electrolyte is A%, the mass percentage of the first additive relative to the total mass of the solid electrolyte is B%, and the secondary battery satisfies 0.1≦B / A≦19. The present application uses a combination of a solid electrolyte and a liquid electrolyte to achieve both the advantages of the solid electrolyte and the advantages of the liquid electrolyte, and improves the dynamic performance, safety performance, and cycle performance of the secondary battery.

Description

[Technical Field]

[0001] The present application relates to a secondary battery, a battery module, a battery pack, and a power consuming device. [Background technology]

[0002] Due to their characteristics such as high capacity and long life, secondary batteries are widely used in electronic devices such as mobile phones, laptops, electric bicycles, electric vehicles, electric airplanes, electric ships, electric toy cars, electric toy ships, electric toy airplanes, power tools, etc. As the range of applications for batteries becomes wider, the requirements for the performance of secondary batteries also become more stringent.

[0003] However, when improving the performance of a secondary battery, it is difficult to simultaneously achieve safety performance, cycle performance, and dynamic performance of the secondary battery. Summary of the Invention

[0004] The present application has been made in view of the above-mentioned problems, and has as its object to provide a secondary battery, a battery module, a battery pack, and a power consuming device.

[0005] A first aspect of the present application provides a secondary battery, the secondary battery including: a positive electrode sheet including a positive electrode film layer; a negative electrode sheet including a negative electrode film layer; an electrolytic solution; and a solid electrolyte; the solid electrolyte is provided on the surface of the positive electrode film layer and / or the negative electrode film layer and includes a polymer matrix and a first additive; the first additive is arranged to form an interfacial film on the surface of the positive electrode film layer and / or the negative electrode film layer; wherein a mass percentage of the polymer matrix relative to a total mass of the solid electrolyte is A %, and a mass percentage of the first additive relative to the total mass of the solid electrolyte is B %, and the secondary battery satisfies 0.1≦B / A≦19, preferably 0.5≦B / A≦10.

[0006] As a result, the polymer matrix in the solid electrolyte of the present application has a certain degree of adhesion, allowing the solid electrolyte to adhere to the surface of the active material. The solid electrolyte has excellent thermal and chemical stability, maintaining good cycle stability during the charge and discharge process of the secondary battery and improving the cycle performance of the secondary battery. The solid electrolyte also has a wide stable electrochemical window, which ensures that adverse interfacial reactions between the electrolyte and the positive and negative electrodes are less likely to occur during the charge and discharge process, thereby reducing the internal resistance of the secondary battery, reducing heat generation, and improving the safety performance and service life of the secondary battery. Furthermore, the first additive forms an interfacial film on the active material surface that is not too thick, which is favorable for the transmission of metal ions, and the interfacial film has low impedance, which is favorable for improving the dynamic performance of the secondary battery. The combined use of a solid electrolyte and a liquid electrolyte combines the advantages of both solid and liquid electrolytes, improving the dynamic performance, safety performance, and cycling performance of the secondary battery.

[0007] In any embodiment, the secondary battery satisfies 5≦A≦99 and / or 0.1≦B≦95. When the mass percentage of the polymer matrix is ​​within this range, adhesion between the polymer matrix and the active material can be ensured, and the solid electrolyte is less likely to fall off from the surface of the active material during charge and discharge of the secondary battery. When the mass percentage of the first additive is within this range, the first additive forms a uniform and stable interfacial film on the positive electrode film layer and / or the negative electrode film layer, and the impedance of the interfacial film is relatively low, which is advantageous for improving the dynamic performance of the secondary battery.

[0008] In any embodiment, the first additive includes a boron-containing lithium salt having a mass percentage of B1% relative to the total mass of the solid electrolyte, and an anode film-forming additive having a mass percentage of B2% relative to the total mass of the solid electrolyte, wherein the secondary battery satisfies 0.002≦B1 / B2≦10. When the mass percentage of the anode film-forming additive of the present application is within the above range, it is ensured that the anode film-forming additive and the boron-containing lithium salt together form a uniform and stable SEI film, and the protective performance for the anode active material can be further improved.

[0009] In any embodiment, the secondary battery satisfies 0.1≦B1≦50 and / or 0.1≦B2≦50.

[0010] In any embodiment, the boron-containing lithium salt has the molecular formula LiBF a O b C c P d In the molecular formula, 0≦a≦4, 0≦b≦8, 0≦c≦4, and 0≦d≦4. Preferably, the boron-containing lithium salt includes one or more of lithium tetrafluoroborate LiBF4, lithium bis(oxalato)borate LiBOB, and lithium bis(fluorooxalato)borate LiDFOB.

[0011] As a result, the present invention uses a blend of lithium tetrafluoroborate (LiBF), lithium bis(oxalato)borate (LiBOB), and lithium bis(fluorooxalato)borate (LiDFOB), resulting in a SEI film with a high content of components, making the structure of the SEI film more stable. Furthermore, the stable structure ensures a relatively low impedance value for the SEI film, thereby ensuring the low-temperature performance of the secondary battery.

[0012] In some embodiments, the negative electrode film-forming additive includes one or more of a carbonate-based additive, a sulfate-based additive, and a sulfite-based additive. The negative electrode film-forming additive and the boron-containing lithium salt of the present application are combined to jointly form an SEI film on the surface of the negative electrode active material, and the multiple components jointly form a film on the surface of the SEI film, enriching the film layer structure of the SEI film and improving the structural stability of the SEI film.

[0013] In any embodiment, the carbonate ester-based additive includes a cyclic carbonate ester solvent and / or a chain carbonate ester solvent. Preferably, the cyclic carbonate ester solvent includes one or more of vinylene carbonate VC, fluoroethylene carbonate FEC, difluoroethylene carbonate DFEC, vinylethylene carbonate VEC, and dioctyl carbonate CC. Preferably, the chain carbonate ester solvent includes one or more of ethyl allyl carbonate AEC, diphenyl carbonate DPC, methyl allyl carbonate MAC, and polycarbonate. PC and / or the sulfate ester additive comprises a cyclic sulfonate ester additive and / or a hydrocarbon group sulfate ester additive, preferably the cyclic sulfonate ester additive comprises one or more of 1,3-propane sultone PS, propene sultone PES, 3-fluoro-1,3-propane sultone FPS, and / or the hydrocarbon group sulfate ester additive comprises one or more of vinyl sulfate DTD, diethyl sulfate DES, and dimethyl sulfate DMS, and / or the sulfite ester additive comprises ethylene sulfite ES and / or vinyl ethylene sulfite VES.

[0014] In any embodiment, the electrolyte solution contains a cyclic carbonate ester solvent having a mass percentage of M1% relative to the total mass of the electrolyte solution, and a chain carbonate ester solvent having a mass percentage of M2% relative to the total mass of the electrolyte solution, and the secondary battery is -3 ≦M1 / M2≦2, preferably 0.1≦M1 / M2≦1, and more preferably 1≦M1≦20 and / or 50≦M2≦85. When the mass percentages of the cyclic carbonate ester solvent and the chain carbonate ester solvent of the present application are within the above ranges, the ionic conductivity of the electrolyte can be further improved.

[0015] In any embodiment, the cyclic carbonate ester solvent includes one or more of ethylene carbonate EC, propylene carbonate PC, vinylene carbonate VC, fluoroethylene carbonate FEC, difluoroethylene carbonate DFEC, vinylethylene carbonate VEC, and dioctyl carbonate CC, and / or the linear carbonate ester solvent includes one or more of ethyl allyl carbonate AEC, diphenyl carbonate DPC, and methyl allyl carbonate MAC, polycarbonate PC , diethyl carbonate DEC, ethyl methyl carbonate EMC, methyl propyl carbonate MPC, ethyl propyl carbonate EPC, and Methyl butyl carbonate MBC and / or It includes one or more of methyl acetate MA, ethyl acetate EA, methyl propionate MP and ethyl propionate EP.

[0016] In any embodiment, the electrolyte solution includes an electrolyte film-forming additive having a mass percentage of D1% relative to the total mass of the electrolyte solution, and a lithium salt having a mass percentage of D2% relative to the total mass of the electrolyte solution, and the secondary battery satisfies 0.2≦E / (D1+D2)≦2.95, where E represents the viscosity of the electrolyte solution and is expressed in mPa s.

[0017] When the secondary battery satisfies the above formula, it is advantageous to improve the dynamic performance of the electrolyte. For example, when a relatively high content of lithium salt and electrolyte film-forming additive is added, the viscosity of the electrolyte is increased, which is advantageous for cooperation between the electrolyte and the solid electrolyte, and the electrolyte film-forming additive is more likely to form a film on the active material surface via the solid electrolyte. When a chain carbonate ester solvent is added to the electrolyte, the viscosity of the electrolyte can be further controlled to be in a low range, which is advantageous for lithium ion migration and ensures the dynamic performance of the electrolyte.

[0018] In any embodiment, the percentage of the solid mass content of the solid electrolyte solution relative to the liquid mass content is m, and the compressed density of the positive electrode membrane layer is P1 g / cm 3The thickness of the positive electrode film layer is h1 μm, and the secondary battery is 5≦h1 * P1 / m≦250. When the secondary battery of the present application satisfies this range, the polymer slurry provides good coverage of the active material and protects the interface. In this limited relationship, the diffusion path of the polymer slurry is appropriate, matching the viscosity of the polymer slurry to favor diffusion of the polymer slurry into the active material, and matching the appropriate compaction density, so that the porosity of the positive electrode membrane layer is appropriate to favor diffusion of the polymer slurry into the voids of the active material, thereby strengthening the bond between the solid electrolyte formed by the polymer slurry and the active material, and resulting in a relatively low impedance at the interface between the solid electrolyte and the active material.

[0019] In any embodiment, the percentage of the solid mass content of the solid electrolyte solution relative to the liquid mass content is m, and the compressed density of the negative electrode film layer is Pg / cm 3 The thickness of the negative electrode film layer is h2 μm, and the secondary battery is 25≦h2 * P2 / m≦245 is satisfied. When the secondary battery of the present application satisfies the above range, the polymer slurry provides good coating on the active material, the diffusion path of the polymer slurry is appropriate, the viscosity of the polymer slurry is suitable, and the polymer slurry is favorable for diffusing into the active material. Also, the compaction density is suitable, so the porosity of the negative electrode film layer is appropriate, and the polymer slurry is favorable for diffusing into the voids of the active material. As a result, the degree of bonding between the solid electrolyte formed by the polymer slurry and the active material is strong, and the impedance at the interface between the solid electrolyte and the active material is relatively low.

[0020] A second aspect of the present application further provides a battery module including a secondary battery according to any one of the embodiments of the first aspect of the present application.

[0021] A third aspect of the present application further provides a battery pack including a battery module according to an embodiment of the second aspect of the present application.

[0022] A fourth aspect of the present application further provides a power consuming device including a secondary battery according to any of the embodiments of the first aspect of the present application, a battery module according to an embodiment of the second aspect of the present application, or a battery pack according to an embodiment of the third aspect of the present application. [Brief explanation of the drawings]

[0023] In order to more clearly explain the technical solutions of the embodiments of the present application, the drawings necessary for the embodiments of the present application will be briefly described below. It is clear that the drawings described below are only some embodiments of the present application. Those skilled in the art can further obtain other drawings based on the drawings without any creative work.

[0024] [Figure 1] 1 is a schematic diagram of one embodiment of a secondary battery of the present application. [Figure 2] FIG. 2 is an exploded schematic view of the embodiment of the secondary battery of FIG. [Figure 3] 1 is a schematic diagram of one embodiment of a battery module of the present application. [Figure 4] 1 is a schematic diagram of one embodiment of a battery pack of the present application. [Figure 5] 5 is an exploded schematic view of the embodiment of the battery pack shown in FIG. 4. [Figure 6] 1 is a schematic diagram of one embodiment of a power consuming device that includes a secondary battery of the present application as a power source. The drawings are not necessarily drawn to scale.

[0025] Explanation of symbols 1, battery pack; 2, upper housing; 3, lower housing; 4, battery module; 5, secondary battery; 51, case; 52, electrode assembly; 53, cover plate; 6, power consumption device. DETAILED DESCRIPTION OF THE INVENTION

[0026] Hereinafter, detailed descriptions will be given of embodiments specifically disclosing the secondary battery, battery module, battery pack, and power consumption device of the present application. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of known matters or redundant descriptions of substantially identical configurations may be omitted. This is to avoid unnecessary redundancy in the following description and to facilitate understanding by those skilled in the art. Note that the accompanying drawings and the following description are provided to enable those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0027] "Ranges" disclosed in this application are defined in the form of lower and upper limits. A given range is defined by selecting one lower limit and one upper limit, and the selected lower and upper limits define the boundaries of that particular range. Such defined ranges may be inclusive or exclusive of the end values, and may be arbitrarily combined; i.e., any lower limit may be combined with any upper limit to form a range. For example, if ranges of 60 to 120 and 80 to 110 are recited for a particular parameter, it is understood that ranges of 60 to 110 and 80 to 120 are also contemplated. Furthermore, if minimum range values ​​of 1 and 2 and maximum range values ​​of 3, 4, and 5 are recited, then ranges of 1 to 3, 1 to 4, 1 to 5, 2 to 3, 2 to 4, and 2 to 5 are all contemplated. In this application, unless otherwise specified, a numerical range "a to b" is represented by the abbreviation for any combination of real numbers between a and b, where a and b are both real numbers. For example, the numerical range "0 to 5" indicates that all real numbers between "0 and 5" are included herein, and "0 to 5" is an abbreviation for combinations of these numerical values. Furthermore, expressing a parameter as an integer greater than or equal to 2 (≧2) is equivalent to disclosing that the parameter is, for example, the integers 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0028] Unless otherwise specified, all embodiments and optional embodiments of the present application may be combined with each other to form new technical solutions, and such technical solutions are considered to be included in the disclosure content of the present application.

[0029] Unless otherwise specified, all steps in the present application may be performed in order or randomly, but are preferably performed in order. For example, when the method includes steps (a) and (b), it means that the method may include steps (a) and (b) performed in order, or may include steps (b) and (a) performed in order. For example, when it is stated that the method may further include step (c), it means that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or may include steps (a), (c), and (b), or may include steps (c), (a), and (b), etc.

[0030] Unless otherwise specified, the terms "comprise" and "include" used in this application mean open-ended and may also be closed-ended. For example, the terms "comprise" and "include" can mean "comprise" or "include" other components not listed, or "comprise" or "include" only the listed components.

[0031] Unless otherwise stated, in this application, the term "or" is inclusive. For example, the phrase "A or B" means "A, B, or both A and B." More specifically, any of the following conditions are met: 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).

[0032] In this application, the terms "plurality" and "plurality" mean two or more than two.

[0033] Secondary batteries are widely used due to their high capacity, long life, and other characteristics. The development of the new energy industry has placed higher demands on the electrical performance and reliability of secondary batteries. Although the energy density and battery capacity of secondary batteries have improved, safety issues can arise. For example, during the charge and discharge process of a high-capacity secondary battery, heat accumulated inside the secondary battery can destroy the separator, causing contact between the anode and cathode, which can lead to a rapid oxidation-reduction reaction and other phenomena, such as combustion. Due to safety issues inherent in liquid electrolytes, the development of secondary batteries has been limited, and the development of safer secondary batteries is therefore crucial.

[0034] Based on this, the inventors discovered that by using a solid electrolyte to protect the surface of the electrode sheet, the solid electrolyte has higher thermal and chemical stability than a liquid electrolyte. Furthermore, because the solid electrolyte is attached to the surface of the electrode sheet, even if the separator is damaged, direct contact between the anode and cathode is inevitable, resulting in high safety. Second, the solid electrolyte has a wide electrochemical window, effectively reducing the occurrence of interfacial side reactions, improving the cycle life of secondary batteries. It also has good electrochemical stability and can be matched with positive electrode active materials with higher charging voltages, resulting in high energy density. However, the interface between the solid electrolyte and the active material is a solid-solid interface, resulting in weak effective contact between the solid electrolyte and the active material, and slow kinetics of metal ion transport in the solid material, resulting in high interfacial impedance.

[0035] Therefore, as a result of intensive research into secondary batteries, the inventors have found that by using a combination of a solid electrolyte and an electrolytic solution, it is possible to increase the amount of a specific substance in the solid electrolyte to improve the protection performance of the active material, reduce the impedance between the solid electrolyte and the active material, and improve the dynamic performance, and by combining it with an electrolytic solution with a relatively low viscosity, it is possible to improve the dynamic performance of the electrolytic solution, thereby comprehensively improving the dynamic performance, safety performance, and cycle performance of the secondary battery. Next, the technical solution of this application will be described in detail.

[0036] secondary battery

[0037] According to a first aspect, the present application provides a secondary battery, also known as a rechargeable battery or storage battery, which can be continuously used by activating the active material by charging after discharging the battery.

[0038] The secondary battery includes a positive electrode sheet, a negative electrode sheet, an electrolytic solution, and a solid electrolyte, the positive electrode sheet includes a positive electrode film layer, the negative electrode sheet includes a negative electrode film layer, and a solid electrolyte is provided on a surface of at least one of the positive electrode film layer and the negative electrode film layer, the solid electrolyte includes a polymer matrix and a first additive, and the first additive is arranged to form an interfacial film on a surface of the positive electrode film layer and / or the negative electrode film layer, wherein a mass percentage of the polymer matrix with respect to a total mass of the solid electrolyte is A%, and a mass percentage of the first additive with respect to a total mass of the solid electrolyte is B%, and the secondary battery satisfies 0.5≦B / A≦19.

[0039] Although the mechanism is not clear, the secondary battery of the present application can comprehensively improve the dynamic performance, safety performance and cycle performance of the secondary battery.

[0040] The inventors speculate that the mechanism of action of the present invention is as follows.

[0041] The solid electrolyte may be provided in the positive electrode film layer, which includes a positive electrode active material. That is, the solid electrolyte is provided in the positive electrode active material, and a film-forming reaction can occur between the first additive in the solid electrolyte and the positive electrode active material, forming a CEI film, which is a positive electrode solid electrolyte interphase film, on the surface of the positive electrode active material. The solid electrolyte may be provided in the negative electrode film layer, which is provided in the negative electrode active material, and a film-forming reaction can occur between the first additive in the solid electrolyte and the negative electrode active material, forming a solid electrolyte interphase (SEI film) on the surface of the negative electrode active material. Alternatively, the solid electrolyte may be provided in both the positive electrode film layer and the negative electrode film layer, that is, the solid electrolyte is provided on both the positive electrode active material and the negative electrode active material. In this application, the CEI film and the SEI film are collectively referred to as interphase films.

[0042] The solid electrolyte is applied to the active material, and the polymer matrix in the solid electrolyte has a certain adhesiveness, allowing the solid electrolyte to adhere to the surface of the active material. The solid electrolyte has excellent thermal and chemical stability, maintaining good cycle stability during the charge and discharge process of the secondary battery and improving the cycle performance of the secondary battery. The solid electrolyte also has a wide stable electrochemical window, which ensures that adverse interfacial reactions between the electrolyte and the positive and negative electrodes are unlikely to occur during the charge and discharge process, thereby reducing the internal resistance of the secondary battery, reducing heat generation, and improving the safety performance and service life of the secondary battery.

[0043] The polymer matrix generally has a porous structure with small pores. When the first additive and the polymer matrix form a solid electrolyte, the first additive fills the pores of the polymer matrix, disperses uniformly within the polymer matrix, and the groups in the polymer matrix form complex coordination interactions with the metal ions in the first additive, such as lithium ions. Due to the irregular Brownian motion of the polymer matrix, the metal ions undergo repeated coordination and dissociation within the polymer matrix, achieving lithium ion transport. Because the first additive used in film formation is incorporated into the solid electrolyte, the amount of first additive used can be reduced, reducing the water content and the risk of side reactions within the secondary battery.

[0044] After injecting the electrolyte into the secondary battery, the electrolyte infiltrates the positive and negative electrode sheets. When the solid electrolyte is infiltrated with the electrolyte, the first additive contained therein dissolves in the electrolyte. The dissolved first additive is more likely to form an interfacial film on the surface of the active material, providing good protection for the active material. The interfacial film formed by the first additive on the surface of the active material is not too thick, which is advantageous for the transport of metal ions and has low impedance, which is advantageous for improving the dynamic performance of the secondary battery. Furthermore, the solid electrolyte reduces the risk of side reactions due to contact between the solvent in the electrolyte and the positive and negative electrode sheets, thereby reducing the possibility of decomposition of the electrolyte.

[0045] In the charging process of a secondary battery, the metal ion is described as an example of lithium ions, and the kinetic process generally includes the steps of lithium ions desorbing from the positive electrode active material and migrating to the electrolyte phase, solvated lithium ions in the electrolyte diffusing and transferring to the surface of the negative electrode active material, and lithium ions acquiring electrons from the surface of the negative electrode active material and diffusing into the negative electrode active material. The present application describes that during the process of lithium ions desorbing from the positive electrode active material to the electrolyte phase, the CEI film on the surface of the positive electrode active material is thin, which reduces the migration barrier, and the electrolyte is a liquid electrolyte with a relatively low viscosity and high ionic conductivity, which reduces the migration barrier during the process of lithium ions migrating from the electrolyte to the negative electrode active material. The SEI film on the surface of the negative electrode active material is thin, which reduces the migration barrier for lithium ions migrating from the SEI film to the interior of the negative electrode active material. Therefore, the migration barrier during the entire kinetic process of lithium ions is low, requiring less energy and favoring rapid lithium ion migration, resulting in relatively good kinetic performance of the secondary battery.

[0046] The present application utilizes a combination of a solid electrolyte and a liquid electrolyte to achieve both the advantages of a solid electrolyte and a liquid electrolyte, thereby improving the dynamic performance, safety performance, and cycle performance of a secondary battery.

[0047] [Solid electrolyte]

[0048] The solid electrolyte includes a polymer matrix and a first additive. In some embodiments, the polymer matrix includes one or more of polyethylene oxide (PEO), polyurethane (PU), polymethyl methacrylate (PMMA), polyacrylonitrile (PAN), polyvinylidene fluoride (PVDF), poly(vinylidene fluoride-hexafluoropropylene) (P(VDF-HFP)), polypropylene carbonate (PPC) and polycarbonate (PC), polyvinyl chloride (PVC), polyethylene carbonate (PEC), polylactic acid (PLA), polytetrafluoroethylene (PTFE), and blends and copolymers containing characteristic functional groups, where the characteristic functional groups include electron-withdrawing groups, illustratively, one or more of polymers having polar atoms or groups such as fluorine atom (F), nitrogen atom (N), sulfur atom (S), carbonyl (C=O), nitrile group (-CN), and sulfonyl (S=O).

[0049] Blends are used to adjust the physical and chemical properties of materials, and include various blend systems such as PVDF-HFP / polyethyl methacrylate (PEMA), PEO / PVDF, PVDF-HFP / polyvinyl acetate (PVAc), PVC / PMMA, PVDF-HFP / PMMA, and PVDF-HFP / PAN. Copolymer systems include PEO-polystyrene (PSt), polydimethylsiloxane (PDMS)-PEO, PEGMA-MMA-IBVE, PEO-PMMA, POEM-PBMA, PPG-PEG-PPG, and MMA-AN-BA.

[0050] The polymer matrix has good mechanical properties, and the resulting solid electrolyte has good flexibility, allowing it to form a stable and good electrode-electrolyte interface with the active material. Furthermore, the molecular chain segments of the polymer matrix have the ability of thermal motion, which increases with increasing temperature. The polymer matrix has the ability to conduct lithium ions, which is advantageous for metal ions, such as lithium ions, to constantly undergo a coordination-dissociation-coordination process with characteristic atoms and groups, thereby realizing the transport of lithium ions within or between the molecular chains of the polymer matrix. The resulting solid electrolyte has high ionic conductivity.

[0051] In some embodiments, the mass percentage A% of the polymer matrix relative to the total mass of the solid electrolyte is 5≦A≦99. When the mass percentage of the polymer matrix is ​​in this range, adhesion between the polymer matrix and the active material can be ensured, and the solid electrolyte is less likely to fall off the surface of the active material during charge and discharge of the secondary battery. Preferably, 5≦A≦70. Exemplarily, the mass percentage A% of the polymer matrix may be 5%, 10%, 15%, 25%, 35%, 45%, 55%, 65%, 70%, 90%, 95%, or 99%, or may be a range consisting of any two of the above values.

[0052] In some embodiments, the first additive may be used to form an interfacial film on the surface of the positive electrode film layer and / or the negative electrode film layer, and the mass percentage B% of the first additive is 0.1≦B≦95 with respect to the total mass of the solid electrolyte.

[0053] When the mass percentage of the first additive is within the above range, the first additive forms a uniform and stable interfacial film in the positive electrode film layer and / or the negative electrode film layer, and the impedance of the interfacial film is relatively low, which is advantageous for improving the dynamic performance of the secondary battery. Preferably, 10≦B≦95. For example, the mass percentage B% of the first additive may be 0.1%, 1%, 5%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, or 95%, or may be a range consisting of any two of the above values.

[0054] In some embodiments, the first additive may include a conductive lithium salt to ensure smooth lithium ion migration. The conductive lithium salt may be a boron-containing lithium salt. The boron-containing lithium salt has good compatibility with the polymer matrix, and adding the boron-containing lithium salt can lower the glass transition temperature of the polymer matrix to some extent, improving the mechanical strength and the amorphous phase stability temperature of the polymer matrix. The boron-containing lithium salt has a large anion group and easily dissociates lithium ions, ensuring the solubility of lithium ions and improving the ionic conductivity of the polymer electrolyte.

[0055] In some embodiments, the molecular formula of the boron-containing lithium salt is LiBF a O b C c P d and in the molecular formula, 0≦a≦4, 0≦b≦8, 0≦c≦4, and 0≦d≦4.

[0056] The B atom can bond with an oxygen-containing oxalate ligand. The resulting bonded product has excellent thermal stability and is easily able to form a high-performance SEI film on the surface of the negative electrode active material, thereby ensuring the structural stability of the negative electrode active material and improving the cycle performance of the secondary battery. Of course, the B atom can also bond with a halogen atom, particularly a fluorine atom. Fluorine atoms have a strong electron-withdrawing inductive effect and are highly thermally and chemically stable. Furthermore, the high solubility of lithium ions in the electrolyte ensures the solubility of lithium ions and the conductivity of the electrolyte.

[0057] For example, the boron-containing lithium salt includes one or more of lithium tetrafluoroborate (LiBF), lithium bis(oxalato)borate (LiB(C2O4)2, abbreviated as LiBOB), and lithium bis(fluorooxalato)borate (LiBC2O4F2, abbreviated as LiDFOB). Further, the boron-containing lithium salt includes a composition of lithium tetrafluoroborate LiBF4, lithium bis(oxalato)borate (LiB(C2O4)2, abbreviated as LiBOB), and lithium bis(fluorooxalato)borate (LiBC2O4F2, abbreviated as LiDFOB).

[0058] When lithium tetrafluoroborate (LiBF4) is used in combination with an organic solvent, such as a carbonate ester-based solvent or additive, in an electrolyte, the viscosity of the system composed of lithium tetrafluoroborate is relatively low, which is favorable for the release of lithium ions, thereby improving the electrical conductivity of the electrolyte. The SEI film formed by lithium tetrafluoroborate has a uniform thickness, good kinetic activity, and low charge transfer resistance in secondary batteries, thereby significantly improving the low-temperature performance of secondary batteries. The SEI film is resistant to thermal decomposition and has stable performance at high temperatures, which significantly improves the high-temperature performance of secondary batteries.

[0059] Either lithium bis(oxalato)borate (LiBOB) or lithium bis(fluorooxalato)borate (LiDFOB) has a passivation effect on the positive electrode current collector in the positive electrode sheet, reducing the risk of side reactions with the positive electrode current collector causing corrosion of the positive electrode current collector and improving the structural stability of the positive electrode sheet. Furthermore, an electrolyte containing either lithium bis(oxalato)borate (LiBOB) or lithium bis(fluorooxalato)borate (LiDFOB) is less likely to produce acidic substances, further reducing the risk of corrosion of the positive electrode current collector. Lithium bis(oxalato)borate (LiBOB) and lithium bis(fluorooxalato)borate (LiDFOB) are highly compatible with the positive electrode active material, favoring lithium ion migration. They form an effective SEI film on the surface of the negative electrode active material, improving the protection of the negative electrode active material.

[0060] The combined use of lithium tetrafluoroborate (LiBF), lithium bis(oxalato)borate (LiBOB), and lithium bis(fluorooxalato)borate (LiDFOB) results in a larger number of components in the SEI film formed by the three, resulting in a more stable structure of the SEI film. Furthermore, while ensuring a stable structure, the SEI film has a relatively small impedance value, ensuring the low-temperature performance of the secondary battery.

[0061] In some embodiments, the mass percentage of the boron-containing lithium salt is B1%, relative to the total mass of the solid electrolyte, and 0.1≦B1≦50.

[0062] When the mass percentage of the boron-containing lithium salt is within the above range, the ion conduction ability of the solid electrolyte can be ensured. Furthermore, the mass percentage B1% of the boron-containing lithium salt can provide good protection for the positive electrode current collector and the negative electrode active material. For example, the mass percentage B1% of the boron-containing lithium salt can be 0.1%, 0.5%, 1%, 2%, 10%, 20%, 25%, or 50%, etc.

[0063] In some embodiments, the conductive lithium salt may further comprise an ionically conductive lithium salt, such as one or more of lithium hexafluoroarsenate (LiPF), lithium difluorophosphate (LiPO), difluorobis(oxalatophosphate) (LiDODFP), lithium tetrafluorooxalophosphate (LiDFBP), lithium bisfluorosulfonylimide (LiFSI), lithium bistrifluoromethanesulfonylimide (LiTFSI), lithium fluorosulfonate (LiSO), lithium nitrate (LiNO), lithium perchlorate (LiClO), lithium hexafluoroantimonate (LiSbF), and lithium hexafluoroarsenate (LiAsF). The ionically conductive lithium salts have a relatively high degree of dissociation and high conductivity, which is favorable for lithium ion migration.

[0064] In some embodiments, the first additive may include a negative electrode film-forming additive, which may include one or more of a carbonate-based additive, a sulfate-based additive, and a sulfite-based additive.

[0065] The negative electrode film-forming additive and the boron-containing lithium salt cooperate to form an SEI film on the surface of the negative electrode active material, and the multiple components are formed on the surface of the SEI film together to enrich the film layer structure of the SEI film and improve the structural stability of the SEI film. Furthermore, the negative electrode film-forming additive includes at least two of carbonate ester-based additives, sulfate ester-based additives, sulfite ester-based additives, and lithium fluorooxalic acid phosphate, and the SEI film formed therefrom has a rich composition and higher structural stability.

[0066] The mass percentage of the negative electrode film-forming additive relative to the total mass of the solid electrolyte is B2%, where 0.1≦B2≦50.

[0067] When the mass percentage of the negative electrode film-forming additive is within the above range, the negative electrode film-forming additive can form a uniform and stable SEI film, and the protective performance of the negative electrode active material can be further improved. For example, the mass percentage B2% of the negative electrode film-forming additive can be 0.1%, 0.5%, 1%, 2%, 10%, 20%, 25%, or 50%, etc.

[0068] In some embodiments, 0.002≦B1 / B2≦9.

[0069] When the mass percentage of the negative electrode film-forming additive is within the above range, the negative electrode film-forming additive and the boron-containing lithium salt can form a uniform and stable SEI film together, thereby further improving the protection performance of the negative electrode active material. For example, B1 / B2 can be 0.002, 0.2, 0.5, 1, 2, 5, or 9, etc.

[0070] For example, the carbonate ester additives include cyclic carbonate ester additives and / or linear carbonate ester additives. Furthermore, the cyclic carbonate ester additives include one or more of vinylene carbonate (VC), fluoroethylene carbonate (FEC), difluoroethylene carbonate (DFEC), vinylethylene carbonate (VEC), and dioctyl carbonate (CC). The linear carbonate ester additives include ethyl allyl carbonate (AEC), diphenyl carbonate (DPC), methyl allyl carbonate (MAC), and polycarbonate. PC It includes one or more types of the above.

[0071] For example, the sulfate ester additive may include a cyclic sulfonate ester additive and / or a hydrocarbon group sulfate ester additive. The cyclic sulfonate ester additive may include one or more of 1,3-propane sultone PS, propene sultone PES, and 3-fluoro-1,3-propane sultone FPS. The hydrocarbon group sulfate ester additive may include one or more of vinyl sulfate DTD, diethyl sulfate DES, and dimethyl sulfate DMS.

[0072] By way of example, sulfite additives include ethylene sulfite ES and / or vinyl ethylene sulfite VES.

[0073] In some embodiments, the solid electrolyte may further include at least one solvent, such as acetonitrile, tetrahydrofuran, acetone, N-methylpyrrolidone, N,N-dimethylformamide, acetonitrile, tetrahydrofuran, acetone, N-methylpyrrolidone, and N,N-dimethylformamide, to enhance compatibility between the polymer matrix and the first additive, etc.

[0074] In some embodiments, the solid electrolyte may further include additives such as plasticizers, ionic liquids, etc. to improve the ionic conductivity and lithium ion mobility of the solid electrolyte, and to improve the interfacial compatibility of the electrode-electrolyte interface. Exemplary plasticizers may be ethylene carbonate (EC), propylene carbonate (PC), etc.

[0075] The solid electrolyte can be prepared by uniformly mixing the polymer matrix, the first additive, etc., forming a polymer slurry, applying it to the surface of the electrode sheet by a solution injection method, transferring it, and curing it to form a film.

[0076] [Electrolyte]

[0077] The electrolyte serves to conduct metal ions between the positive electrode sheet and the negative electrode sheet. The electrolyte of the present application can be any electrolyte used in secondary batteries known in the art. The electrolyte includes a lithium salt and an organic solvent.

[0078] In some embodiments, the lithium salt is at least one selected from the group consisting of lithium hexafluoroarsenate (LiPF), lithium difluorophosphate (LiPO), difluorobis(oxalatophosphate) (LiDODFP), lithium tetrafluorooxalate phosphate (LiDFBP), lithium bisfluorosulfonylimide (LiFSI), lithium bistrifluoromethanesulfonylimide (LiTFSI), lithium fluorosulfonate (LiSO), lithium nitrate (LiNO), lithium perchlorate (LiClO), lithium hexafluoroantimonate (LiSbF), and lithium hexafluoroarsenate (LiAsF). The mass percentage of the lithium salt relative to the total mass of the electrolyte is D2%.

[0079] Furthermore, when 1≦D2≦25 and the lithium salt is within the above range, a sufficient lithium source is provided for the electrolyte to form ion paths, and the electrolyte has high ion conductivity.

[0080] Illustratively, D2 may be 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 12, 15, 17, 19, 20, 21, 22, 23, or 25, or may be a range consisting of any two of the above numbers.

[0081] In some embodiments, the organic solvent may include a carbonate ester solvent, and the carbonate ester solvent may include a cyclic carbonate ester solvent and a chain carbonate ester solvent. By using a combination of a cyclic carbonate ester solvent and a chain carbonate ester solvent, the electrolyte solution has a high dielectric constant and low viscosity, and the ionic conductivity of the electrolyte solution can be improved. In addition, the electrochemical stability of the electrolyte solution is high, and the electrochemical window is significantly improved.

[0082] In some embodiments, the mass percentage of the cyclic carbonate ester solvent relative to the total mass of the electrolyte solution is M1%, the mass percentage of the chain carbonate ester solvent relative to the total mass of the electrolyte solution is M2%, and -3 ≦M1 / M2≦2.

[0083] When the mass percentages of the cyclic carbonate ester solvent and the chain carbonate ester solvent are within the above ranges, the ionic conductivity of the electrolyte solution can be further improved. Preferably, 0.1≦M1 / M2≦1. For example, M1 / M2 may be 0.001, 0.01, 0.1, 0.2, 0.5, 0.7, 0.9, or 1, or may be a range consisting of any two of the above values.

[0084] Exemplary cyclic carbonate solvents include one or more of ethylene carbonate EC, propylene carbonate PC, vinylene carbonate VC, fluoroethylene carbonate FEC, difluoroethylene carbonate DFEC, vinylethylene carbonate VEC, and dioctyl carbonate CC.

[0085] Furthermore, M1 satisfies the condition of 1≦M1≦20. When the mass percentage of the cyclic carbonate solvent is within the above range, dissociation of lithium ions is promoted, the solubility of lithium ions is increased, and the ionic conductivity of the electrolyte solution can be further improved. Illustratively, M1 may be 1, 5, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20, or may be a range consisting of any two of the above values.

[0086] Examples of the chain carbonate ester solvent include ethyl allyl carbonate (AEC), diphenyl carbonate (DPC), and methyl allyl carbonate (MAC), polycarbonate. PC , Diethyl carbonate DEC, Ethyl methyl carbonate EMC, Methyl propyl carbonate MPC, Ethyl propyl carbonate EPC, Methyl butyl carbonate MBC Includes one or more of the following types: , methyl acetate MA, ethyl acetate EA, methyl propionate MP, and ethyl propionate EP.

[0087] Furthermore, M2 is 50≦M2≦85. When the mass percentage of the chain carbonate solvent is within the above range, it can provide a low viscosity to the electrolyte, which is favorable for smooth migration of lithium ions and improves the kinetic performance of the electrolyte. For example, M2 can be 50, 52, 55, 56, 58, 60, 62, 65, 66, 68, or 85.

[0088] In some embodiments, the organic solvent may further include an ether-based solvent. The ether-based solvent has low viscosity, which can increase the ionic conductivity of the electrolyte and allow lithium ions in the electrolyte to maintain a good morphology during circulation. Examples of the ether-based solvent include ethyl ether and polymethoxy ether.

[0089] In some embodiments, the organic solvent may further include a nitrile-based solvent. Nitrile-based solvents have high stability, which can improve the stability of the entire electrolyte solution. Exemplary nitrile-based solvents may include adiponitrile, glutaronitrile, etc.

[0090] Of course, the organic solvent may include other types of solvents, such as sulfonic solvents.

[0091] Exemplarily, the organic solvent is at least one selected from ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butylene 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.

[0092] In some embodiments, the electrolyte may further include an electrolyte additive. For example, the electrolyte additive may include an electrolyte film-forming additive such as an anode film-forming additive or a cathode film-forming additive, or may include an additive that can improve certain battery performance, such as an additive that improves the battery's overcharge performance or an additive that improves the battery's high-temperature or low-temperature performance. For example, the anode film-forming additive may include one or more of a carbonate ester-based additive, a sulfate ester-based additive, and a sulfite ester-based additive. Specific types of electrolyte film-forming additives are the same as those described for the solid electrolyte, and will not be described here. The mass percentage of the electrolyte film-forming additive relative to the total mass of the electrolyte is defined as D1%.

[0093] Preferably, 10 -3 ≦D1≦10. When D1 is in the above range, it is possible to ensure that an interface film is sufficiently formed on the surface of the active material, and to improve the protective effect on the active material. Preferably, 0.1≦D1≦10. For example, D1 is 10 -3 , 10 -2, 0.1, 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10, or may be a range consisting of any two of the above numbers.

[0094] In some embodiments, the secondary battery further satisfies 0.2≦E / (D2+D1)≦2.95, where E represents the viscosity of the electrolyte solution, and its unit is mPa·s.

[0095] When the secondary battery satisfies the above formula, it is advantageous to improve the dynamic performance of the electrolyte. For example, adding a relatively high content of lithium salt and electrolyte film-forming additive increases the viscosity of the electrolyte, which is advantageous for cooperation between the electrolyte and the solid electrolyte and makes it easier for the electrolyte film-forming additive to form a film on the active material surface through the solid electrolyte. When a chain carbonate ester solvent is added to the electrolyte, the viscosity of the electrolyte can be further controlled to be in a low range, which is advantageous for lithium ion migration and ensures the dynamic performance of the electrolyte. For example, E / (D2+D1) may be 0.2, 0.25, 0.28, 1, 1.2, 1.5, 1.8, 2, 2.5, or 2.95, or may be a range consisting of any two of the above values.

[0096] Furthermore, 0.1≦E≦8. Exemplarily, E may be 0.1, 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 5, 6, 7, or 8, or may be a range consisting of any two of the above values. When E is in the above range, the viscosity of the electrolyte can be adjusted within an appropriate range, which is advantageous for the migration of lithium ions.

[0097] [Positive electrode sheet]

[0098] In some embodiments, the positive electrode sheet includes a positive electrode current collector and a positive electrode film layer provided on at least one surface of the positive electrode current collector. For example, the positive electrode current collector has two surfaces facing each other in the thickness direction of the positive electrode current collector, and the positive electrode film layer is provided on one or both of the two surfaces of the positive electrode current collector.

[0099] In some embodiments, the solid electrolyte is provided on the surface of the positive electrode film layer, i.e., on the surface of the positive electrode film layer away from the positive electrode current collector, thereby providing good protection for the positive electrode sheet, ensuring the structural stability of the positive electrode sheet and improving the cycle performance of the secondary battery.

[0100] In some embodiments, the solid mass percentage of the solid electrolyte solution relative to the liquid mass is m, and the compressed density of the positive electrode membrane layer is P1 g / cm 3 The thickness of the positive electrode film layer is set to h1 μm, and the secondary battery is set to 5≦h1 * P1 / m≦250 is satisfied.

[0101] The solids in the solid electrolyte include the polymer matrix, boron-containing lithium salt, etc., and the mass percentage relative to the solid electrolyte is the solid mass content of the solution of the solid electrolyte. The liquid substances in the solid electrolyte solution, such as solvents, are the liquid mass content of the solid electrolyte relative to the mass percentage content of the solid electrolyte. The percentage of the solid mass content of the solution relative to the liquid mass content is m.

[0102] In this application, the compressed density of a material has a meaning well known in the art and can be tested using equipment and methods known in the art. For example, it can be tested using an electronic pressure tester (e.g., UTM7305 type) with reference to standard GB / T24533-2009. An exemplary test method is to weigh 1 g of material and measure the density of the material with a base area of ​​1.327 cm. 2 The material was placed in a mold, pressurized to 2000 kg (equivalent to 20,000 N), and held for 30 seconds, after which the pressure was released and held for 10 seconds. The compressed density of the material at an applied force of 20,000 N was then recorded and calculated.

[0103] When the secondary battery satisfies the above range, the polymer slurry provides good coverage to the active material and protects the interface. In this limited relationship, the diffusion path of the polymer slurry is appropriate, matching the viscosity of the polymer slurry, favoring the diffusion of the polymer slurry into the active material, and matching the appropriate compaction density, resulting in an appropriate porosity of the positive electrode membrane layer, favoring the diffusion of the polymer slurry into the voids of the active material. This strengthens the bond between the solid electrolyte formed by the polymer slurry and the active material, resulting in a relatively low impedance at the interface between the solid electrolyte and the active material. Preferably, 100≦h1×P1 / m≦250. For example, h1 * P1 / m may be 0.4, 0.8, 1, 2, 3, 5, 8, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 100, 110, 120, 150, 160, 170, 180, 190, 200, 220, 250, 260, 280, or 300, or may be a range consisting of any two of the above values.

[0104] Furthermore, 1≦m≦50. m may be 1, 2, 5, 10, 15, 20, 25, 30, 35, 40, 45, or 50, or may be a range consisting of any two of the above numbers.

[0105] Furthermore, 10≦h1≦300. h1 may be 10, 20, 50, 60, 80, 100, 120, 150, 180, 200, 220, 250, 280, 300, or may be a range consisting of any two of the above values.

[0106] Furthermore, 0.1≦P1≦5. P1 may be 0.1, 0.5, 1, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, or 5, or may be a range consisting of any two of the above numbers.

[0107] The positive electrode film layer includes a positive electrode active material, which may be a positive electrode active material for secondary batteries known in the art. For example, the positive electrode active material may include at least one of a lithium transition metal oxide, a lithium-containing phosphate with an olivine structure, and a modified compound thereof. Exemplary lithium transition metal oxides include at least one of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, and modified compounds thereof. Exemplary lithium-containing phosphates with an olivine structure include at least one of lithium iron phosphate, a composite material of lithium iron phosphate and carbon, lithium manganese phosphate, a composite material of lithium manganese phosphate and carbon, lithium manganese iron phosphate, a composite material of lithium manganese iron phosphate and carbon, and modified compounds thereof. The present application is not limited to these materials, and other materials known in the art for use as positive electrode active materials for secondary batteries may also be used. These positive electrode active materials may be used singly or in combination of two or more kinds.

[0108] In some embodiments, the positive electrode active material is LiNi x Co y Mn z M 1-x-y-z O2 or LiNi a Co b Al c N 1-a-b-cO2, where M and N are each independently any one selected from Co, Ni, Mn, Mg, Cu, Zn, Al, Sn, B, Ga, Cr, Sr, V, and Ti, and 0≦y≦1, 0≦x<1, 0≦z≦1, x+y+z≦1, 0≦a≦1, 0≦b≦1, 0≦c≦1, a+b+c≦1. When the positive electrode active material is used in combination with a boron-containing lithium salt, B atoms in the boron-containing lithium salt are more likely to bond with O atoms in the positive electrode active material, thereby reducing the charge transfer resistance of the positive electrode active material and the diffusion resistance of lithium ions within the bulk of the positive electrode active material. Therefore, when the non-aqueous electrolyte contains an appropriate amount of lithium tetrafluoroborate and lithium bisfluorooxalatoborate, the low-cobalt or cobalt-free positive electrode active material significantly improves the lithium ion diffusion rate, allowing lithium ions in the bulk of the low-cobalt or cobalt positive electrode active material to be promptly replenished to the surface, preventing excessive lithium desorption from the surface of the low-cobalt or cobalt positive electrode active material, thereby stabilizing the crystalline structure of the low-cobalt or cobalt-free positive electrode active material. Because the low-cobalt or cobalt-free positive electrode active material has a more stable crystalline structure, it significantly reduces the likelihood of lithium desorption from the surface of the low-cobalt or cobalt-free positive electrode active material causing problems such as unstable structural, chemical, or electrochemical properties, such as irreversible distortion and increased lattice defects in the positive electrode active material.

[0109] LiNi x Co y Mn z M 1-x-y-z O2orLiNi a Co b Al c N 1-a-b-cO2 was produced by a conventional method known in the art. An exemplary production method involves mixing a lithium source, a nickel source, a cobalt source, a manganese source, an aluminum source, an M element precursor, and an N element precursor, followed by sintering. The sintering atmosphere can be an oxygen-containing atmosphere, such as an air atmosphere or an oxygen gas atmosphere. The O2 concentration in the sintering atmosphere is, for example, 70% to 100%. The sintering temperature and sintering time can be adjusted according to the actual situation.

[0110] Exemplary lithium sources include, but are not limited to, at least one of lithium oxide (LiO), lithium phosphate (LiPO), lithium dihydrogen phosphate (LiHPO), lithium acetate (CHCOOLi), lithium hydroxide (LiOH), lithium carbonate (LiCO), and lithium nitrate (LiNO). Exemplary nickel sources include, but are not limited to, at least one of nickel sulfate, nickel nitrate, nickel chloride, nickel oxalate, and nickel acetate. Exemplary cobalt sources include, but are not limited to, at least one of cobalt sulfate, cobalt nitrate, cobalt chloride, cobalt oxalate, and cobalt acetate. Exemplary manganese sources include, but are not limited to, at least one of manganese sulfate, manganese nitrate, manganese chloride, manganese oxalate, and manganese acetate. Exemplary aluminum sources include, but are not limited to, at least one of aluminum sulfate, aluminum nitrate, aluminum chloride, aluminum oxalate, and aluminum acetate. For example, precursors of the M element include, but are not limited to, at least one of oxides, nitrate compounds, carbonate compounds, hydrogen hydroxide compounds, and acetate compounds of the M element. For example, precursors of the N element include, but are not limited to, at least one of ammonium fluoride, lithium fluoride, hydrogen fluoride, ammonium chloride, lithium chloride, hydrogen chloride, ammonium nitrate, ammonium nitrite, ammonium carbonate, ammonium hydrogen carbonate, ammonium phosphate, phosphoric acid, ammonium sulfate, ammonium hydrogen sulfate, ammonium hydrogen sulfite, ammonium sulfite, ammonium hydrogen sulfide, hydrogen sulfide, lithium sulfide, ammonium sulfide, and elemental sulfur.

[0111] In some embodiments, the molecular formula for the total mass of the positive electrode layer is LiNi x Co y Mn z M 1-x-y-z O2 or LiNi a Co b Al c N 1-a-b-c The mass percentage of the layered material is 80-99%. For example, the molecular formula is LiNix Co y Mn z M 1-x-y-z O2 or LiNi a Co b Al c N 1-a-b-c The mass percentage of the layered material of O2 may be 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or any range therebetween. Preferably, the molecular formula is LiNi x Co y Mn z M 1-x-y-z O2 or LiNi a Co b Al c N 1-a-b-c The mass percentage of the O2 layered material is 85% to 99%, 90% to 99%, 95% to 99%, 80% to 98%, 85% to 98%, 90% to 98%, 95% to 98%, 80% to 97%, 85% to 97%, 90% to 97%, or 95% to 97%.

[0112] In some embodiments, the positive electrode film layer may further include a positive electrode conductive agent. The present application does not particularly limit the type of the positive electrode conductive agent. For example, the positive electrode conductive agent may include one or a combination of materials selected from superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon particles, carbon nanotubes, graphene, and carbon nanofibers. In some embodiments, the mass percentage of the positive electrode conductive agent is 5% or less of the total mass of the positive electrode film layer.

[0113] In some embodiments, the positive electrode film layer may preferably further include a positive electrode binder. The present application does not particularly limit the type of positive electrode binder. For example, the positive electrode binder may include one or a combination of materials selected from polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a vinylidene fluoride-tetrafluoroethylene-propylene ternary copolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene ternary copolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, and a fluorine-containing acrylate resin. In some embodiments, the mass percentage of the positive electrode binder is 5% or less of the total mass of the positive electrode film layer.

[0114] In some embodiments, the positive electrode current collector may be a metal foil piece or a composite current collector. Examples of metal foil sheets include aluminum foil or aluminum alloy foil. The composite current collector may include a polymeric material base layer and a metal material layer formed on at least one surface of the polymeric material base layer. For example, the metal material may include one or a combination of materials selected from aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy. The polymeric material base layer may include one or a combination of materials selected from polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0115] The positive electrode film layer is typically formed by applying a positive electrode slurry to a positive electrode current collector, drying, and cold pressing. The positive electrode slurry is typically formed by dispersing a positive electrode active material, an optional conductive agent, an optional binder, and any other components in a solvent and stirring the mixture uniformly. The solvent may be, but is not limited to, N-methylpyrrolidone (NMP).

[0116] The electrolyte solution of the present application can be prepared according to a conventional method in this field. For example, the electrolyte solution can be obtained by uniformly mixing additives, a solvent, an electrolyte salt, etc. The order of addition of each material is not particularly limited. For example, the additives, the electrolyte salt, etc. can be added to a non-aqueous solvent and mixed uniformly to obtain a non-aqueous electrolyte solution.

[0117] In the present application, the components and their contents in the electrolyte solution can be measured by methods known in the art, such as gas chromatography-mass spectrometry (GC-MS), ion chromatography (IC), liquid chromatography (LC), nuclear magnetic resonance spectroscopy (NMR), etc.

[0118] In the electrolyte test of the present application, a freshly prepared electrolyte may be taken out as is, or the electrolyte may be taken out from a secondary battery. One exemplary method for taking an electrolyte from a secondary battery is to discharge the secondary battery to its end-of-discharge voltage (for safety reasons, the battery is generally fully discharged) and then centrifugal treatment, and the appropriate amount of liquid obtained from the centrifugal treatment is the nonaqueous electrolyte. The nonaqueous electrolyte may also be taken directly from the filling port of the secondary battery.

[0119] [Negative electrode sheet]

[0120] The negative electrode sheet includes a negative electrode current collector and a negative electrode film layer provided on at least one surface of the negative electrode current collector, and the negative electrode film layer includes a negative electrode active material.

[0121] For example, the negative electrode current collector has two surfaces facing each other in the thickness direction thereof, and the negative electrode film layer is provided on one or both of the two facing surfaces of the negative electrode current collector.

[0122] In some embodiments, the solid electrolyte is provided on the surface of the negative electrode film layer, i.e., the surface of the negative electrode film layer away from the negative electrode current collector, and provides good protection for the negative electrode sheet, thereby ensuring the structural stability of the negative electrode sheet and improving the cycle performance of the secondary battery.

[0123] In some embodiments, the percentage of the solid mass content of the solid electrolyte solution relative to the liquid mass content is m, and the compressed density of the negative electrode film layer at an applied force of 20,000 N is P2g / cm 3 The thickness of the negative electrode film layer is set to h2 μm, and the secondary battery satisfies 25≦h2×P2 / m≦245.

[0124] When the secondary battery satisfies the above range, the polymer slurry provides good coating on the active material, matches the viscosity of the polymer slurry, favors the diffusion of the polymer slurry into the active material, and matches the appropriate compaction density, resulting in an appropriate porosity of the negative electrode film layer, favoring the diffusion of the polymer slurry into the voids of the active material. This strengthens the bond between the solid electrolyte formed by the polymer slurry and the active material, resulting in a relatively low impedance at the interface between the solid electrolyte and the active material. Preferably, 50≦h2*P2 / m≦200. For example, h2 * P2 / m may be 0.04, 0.08, 0.1, 0.2, 0.3, 0.4, 0.8, 1, 2, 3, 5, 8, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 100, 110, 120, 150, 160, 170, 180, 190, or 200, or may be a range consisting of any two of the above values.

[0125] Furthermore, 1≦m≦50. m may be 1, 2, 5, 10, 15, 20, 25, 30, 35, 40, 45, or 50, or a range consisting of any two of the foregoing numbers.

[0126] Furthermore, 10≦h2≦300. h2 may be 10, 20, 50, 60, 80, 100, 120, 150, 180, 200, 220, 250, 280, 300, or a range consisting of any two of the above values.

[0127] Furthermore, 1≦P2≦5. P2 may be 1, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, or 5, or may be a range consisting of any two of the above values.

[0128] In some embodiments, the negative electrode active material may be a battery negative electrode active material known in the art. For example, the negative electrode active material may include at least one of artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, lithium titanate, and lithium-aluminum alloys. The silicon-based material may be at least one selected from elemental silicon, silicon-oxygen compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material may be at least one selected from elemental tin, tin-oxygen compounds, and tin alloys. However, the present application is not limited to these materials, and other materials commonly used as battery negative electrode active materials may also be used. These negative electrode active materials may be used alone or in combination.

[0129] In some embodiments, the negative electrode film layer may preferably further include a negative electrode binder. The present application does not particularly limit the type of negative electrode binder. For example, the negative electrode binder may include one or a combination of materials selected from styrene butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, water-soluble acrylic resin (e.g., polyacrylic acid (PAA), polymethacrylic acid (PSMA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS). In some embodiments, the mass percentage of the negative electrode binder is 5% or less of the total mass of the negative electrode film layer.

[0130] In some embodiments, the negative electrode film layer may further include a negative electrode conductive agent. The present application does not particularly limit the type of the negative electrode conductive agent. For example, the negative electrode conductive agent may include one or a combination of materials selected from superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon particles, carbon nanotubes, graphene, and carbon nanofibers. In some embodiments, the mass percentage of the negative electrode conductive agent is 5% or less of the total mass of the negative electrode film layer.

[0131] In some embodiments, the negative electrode membrane layer may further include other additives. For example, the other additives may include thickeners such as carboxymethyl cellulose sodium (CMC-Na) and PTC thermistor materials. In some embodiments, the mass percentage of the other additives relative to the total mass of the negative electrode membrane layer is 2% or less.

[0132] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. Examples of metal foils include copper foil and copper alloy foil. The composite current collector may include a polymeric material base layer and a metal material layer formed on at least one surface of the polymeric material base layer. For example, the metal material may include one or a combination of materials selected from copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy. The polymeric material base layer may include one or a combination of materials selected from polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0133] The negative electrode film layer is typically formed by applying a negative electrode slurry to a negative electrode current collector, drying, and cold pressing. The negative electrode slurry is typically formed by dispersing the negative electrode active material, optional conductive agent, optional binder, and optional other additives in a solvent and stirring the mixture uniformly. The solvent may be, but is not limited to, N-methylpyrrolidone (NMP) or deionized water.

[0134] The negative electrode sheet does not exclude additional functional layers other than the negative electrode film layer. For example, in some embodiments, the negative electrode sheet further includes a protective layer covering the surface of the negative electrode film layer.

[0135] In the present application, the mass percentage of a substance can be measured according to a method known in the art, such as gas chromatography-mass spectrometry (GC-MS), ion chromatography (IC), liquid chromatography (LC), nuclear magnetic resonance spectroscopy (NMR), etc.

[0136] [Separator]

[0137] In some embodiments, the secondary battery further includes a separator. The type of separator in the present application is not particularly limited, and any known porous structure separator having good chemical stability and mechanical stability can be selected.

[0138] In some embodiments, the separator is made of at least one material selected from glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator may be a single-layer film or a multilayer composite film, and is not particularly limited. When the separator is a multilayer composite film, the materials of the layers may be the same or different, and are not particularly limited.

[0139] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator can be formed into an electrode assembly by a winding or lamination process.

[0140] In some embodiments, the secondary battery may include an exterior case that seals the electrode assembly and electrolyte.

[0141] In some embodiments, the exterior of the secondary battery may be a hard case such as a hard plastic case, an aluminum case, or a steel case. The exterior of the secondary battery may be a soft bag, such as a bag soft bag. The soft package may be made of plastic. Examples of plastic include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0142] The shape of the secondary battery of the present application is not particularly limited, and may be cylindrical, rectangular, or any other shape. Figure 1 shows an example of a secondary battery 5 with a prismatic structure.

[0143] In some embodiments, as shown in FIGS. 1 and 2 , the exterior may include a case 51 and a cover plate 53. The case 51 includes a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate are enclosed to form a storage chamber. The case 51 has an opening communicating with the storage chamber, and the cover plate 53 closes the opening to close the storage chamber. The positive electrode sheet, the negative electrode sheet, and the separator may be formed into an electrode assembly 52 by a winding process or a stacking process. The electrode assembly 52 is sealed in the storage chamber. An electrolyte solution is impregnated into the electrode assembly 52. ​​The number of electrode assemblies 52 included in the secondary battery 5 may be one type or multiple types and may be adjusted as required.

[0144] Methods for manufacturing the secondary battery of the present application are known. In some embodiments, a secondary battery can be formed by assembling a positive electrode sheet, a separator, a negative electrode sheet, and an electrolyte. For example, the positive electrode sheet, the separator, and the negative electrode sheet can be wound or stacked to form an electrode assembly, which can then be placed in a housing and dried. The electrode assembly can then be infused with an electrolyte, and the secondary battery can be obtained through processes such as vacuum sealing, standing, chemical formation, and shaping.

[0145] In some embodiments of the present application, the secondary battery of the present application may be assembled into a battery module, and the number of secondary batteries included in the battery module may be multiple, and the specific number may be adjusted according to the application and capacity of the battery module.

[0146] Fig. 3 is a schematic diagram of an example battery module 4. As shown in Fig. 3, in the battery module 4, the plurality of secondary batteries 5 may be arranged in order along the longitudinal direction of the battery module 4. Of course, they may be arranged in any other manner. Furthermore, the plurality of secondary batteries 5 may be fixed by fasteners.

[0147] Preferably, the battery module 4 further includes a housing having an accommodation space, and the plurality of secondary batteries 5 are accommodated in the accommodation space.

[0148] In some embodiments, the battery modules may be assembled into a battery pack, and the number of battery modules included in the battery pack may be adjusted depending on the application and capacity of the battery pack.

[0149] 4 and 5 are schematic diagrams of an example battery pack 1. As shown in FIGS. 4 and 5, the battery pack 1 may include a battery box and a plurality of battery modules 4 provided in the battery box. The battery box includes an upper housing 2 and a lower housing 3, and the upper housing 2 covers the lower housing 3 to form a closed space for accommodating the battery modules 4. The plurality of battery modules 4 may be arranged in the battery box in any manner.

[0150] power consumption equipment

[0151] According to a second aspect, the present application provides a power consuming device, the power consuming device including at least one of the secondary battery, battery module, and battery pack of the present application. The secondary battery, battery module, and battery pack may be used as a power source for the power consuming device, or may be used as an energy storage means for the power consuming device. The power consuming device may be, but is not limited to, a mobile device (e.g., a mobile phone, a laptop, etc.), an electric vehicle (e.g., a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc.), a train, a ship, a satellite, an energy storage system, etc.

[0152] The power consuming device can select a secondary battery, a battery module, or a battery pack according to its needs.

[0153] 6 is a schematic diagram of an example power consuming device 6, which may be a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, etc. To meet the high power and high energy density requirements of the power consuming device, a battery pack 1 or a battery module may be employed.

[0154] As another example, the power consuming device may be a mobile phone, a tablet computer, a laptop computer, etc. These power consuming devices are typically required to be thin and may employ a secondary battery as a power source.

[0155] Example

[0156] The following examples are provided to more specifically describe the contents of the present application, but these examples are merely illustrative, and it will be apparent to those skilled in the art that various modifications and variations within the scope of the disclosure of the present application may be made. All parts, percentages, and ratios reported in the following examples are based on mass unless otherwise specified. All reagents used in the examples are commercially available or may be synthesized according to conventional methods. They may be used as they are without further treatment. All devices used in the examples are commercially available.

[0157] Example 1

[0158] 1. Manufacturing of positive electrode sheets

[0159] As the positive electrode current collector, an aluminum foil having a thickness of 12 μm was used.

[0160] LiNi, the positive electrode active material 0.6 Co 0.2 Mn2O2, carbon black as a conductive agent, and polyvinylidene fluoride (PVDF) as a binder were thoroughly mixed and stirred in an appropriate amount of NMP solvent in a weight ratio of 97.5:1.4:1.1 to form a uniform positive electrode slurry. The positive electrode slurry was then evenly applied to the surface of aluminum foil as a positive electrode current collector, dried, and cold-pressed to obtain a positive electrode film layer.

[0161] The polymer matrix P (VDF-HFP), boron-containing lithium salt (LiBOB), and lithium salt LiTFSI were uniformly stirred to form a polymer slurry, which was then vacuum degassed and applied to the positive electrode film layer. The solution was then left for 12 hours at 5°C to 35°C and in a humidity environment of 0.1% to 30%, causing a phase transition and hardening to form a solid electrolyte.

[0162] 2. Manufacturing of negative electrode sheets

[0163] A copper foil with a thickness of 8 μm was used as the negative electrode current collector.

[0164] The negative electrode active material, graphite, the binder, styrene butadiene rubber (SBR), the thickener, sodium carboxymethyl cellulose (CMC-Na), and the conductive agent, carbon black (SuperP), were mixed in a weight ratio of 96.2:1.8:1.2:0.8 in an appropriate amount of deionized water to form a uniform negative electrode slurry. The negative electrode slurry was then uniformly applied to the surface of copper foil, the negative electrode current collector, and dried and cold-pressed to obtain a negative electrode film layer.

[0165] After vacuum degassing the polymer matrix P (VDF-HFP), boron-containing lithium salt (LiBF4), and lithium salt LiTFSI, they were applied to the negative electrode film layer and left for 12 hours at 5°C to 35°C and in a humidity environment of 0.1% to 30%, whereupon they hardened to form a solid electrolyte.

[0166] 3. Separator

[0167] A porous polyethylene (PE) film was used as the separator.

[0168] 4. Electrolyte production

[0169] In an environment with a water content of less than 10 ppm, non-aqueous organic solvents ethylene carbonate, ethyl methyl carbonate, and diethyl carbonate were mixed in a volume ratio of 1:1:1 to obtain an electrolyte solvent, and then lithium salt was dissolved in the mixed solvent to obtain an electrolyte solution with a lithium salt concentration of 1 mol / L.

[0170] 5. Secondary battery manufacturing

[0171] The positive electrode sheet, separator, and negative electrode sheet are stacked in this order, with the separator acting as a separator between the positive electrode sheet and the negative electrode sheet, and then wound up to obtain an electrode assembly. The electrode assembly is placed in an outer can and dried, after which an electrolyte solution is injected, and the assembly is subjected to processes such as vacuum sealing, standing, chemical formation, and shaping to obtain a lithium ion battery.

[0172] Example 2

[0173] The secondary batteries of Examples 2-1 to 2-12 were manufactured by a method similar to that of Example 1. The difference from Example 1 is that Examples 2-1 to 2-12 adjusted the mass percentages of the first additive and the polymer matrix.

[0174] Comparative Examples 1 and 2

[0175] The secondary batteries of Comparative Examples 1 and 2 were manufactured in a similar manner to that of Example 1. The difference from Example 1 is that the mass percentages of the first additive and the polymer matrix were adjusted in Comparative Examples 1 and 2. The data of Examples 1, 2, and the Comparative Example are shown in Table 1. vinegar.

[0176] [Table 1]

[0177] Example 3

[0178] The secondary batteries of Examples 3-1 to 3-5 were manufactured in a manner similar to that of Example 1. The difference from Example 1 is that Examples 3-1 to 3-5 adjusted the mass percentage B1% of the boron-containing lithium salt. The data of Examples 1 and 3 are shown in Table 2.

[0179] [Table 2]

[0180] Example 4

[0181] The secondary batteries of Examples 4-1 to 4-7 were manufactured in a manner similar to that of Example 1. The difference from Example 1 is that Examples 4-1 to 4-7 adjusted the mass percentage D1% of the electrolyte film-forming additive. The data of Examples 1 and 4 are shown in Table 3.

[0182] [Table 3]

[0183] Example 5

[0184] The secondary batteries of Examples 5-1 to 5-8 were manufactured by a method similar to that of Example 1. The difference from Example 1 is that Examples 5-1 to 5-8 adjusted parameters such as the compressed density P1 of the positive electrode film layer. The data of Examples 1 and 5 are shown in Table 4.

[0185] [Table 4]

[0186] Example 6

[0187] The secondary batteries of Examples 6-1 to 6-6 were manufactured by a method similar to that of Example 1. The difference from Example 1 is that parameters such as the compressed density P2 of the negative electrode film layer were adjusted in Examples 6-1 to 6-6. The data of Examples 6-1 to 6-6 are shown in Table 5.

[0188] [Table 5]

[0189] Testing part

[0190] 1. Testing parameters of positive electrode sheet / negative electrode sheet

[0191] 1.1 Testing the thickness of the positive electrode film layer / negative electrode film layer

[0192] Use a ladybug sand micrometer to measure the thickness of the positive electrode sheet at at least 12 different positions along the thickness direction of the positive electrode sheet, and use the average value as the thickness h1 of the positive electrode sheet. Then, subtract the thickness of the positive electrode current collector to determine the thickness of the positive electrode film layer.

[0193] Use a ladybug sand micrometer to measure the thickness of the negative electrode sheet at at least 12 different positions along the thickness direction of the negative electrode sheet, and use the average value as the thickness h2 of the negative electrode sheet. Then, subtract the thickness of the negative electrode current collector to determine the thickness of the negative electrode film layer.

[0194] 1.2 Testing the compressed density P of the positive electrode film layer / negative electrode film layer

[0195] A certain amount of the prepared negative electrode active material sample was taken and placed in a mold with a base area of ​​1.327 cm2 in a UTM7305 type electronic pressure tester. A pressure of 2000 kg (equivalent to 20,000 N) was applied, and the pressure was maintained for 30 seconds. After the pressure was released and maintained for 10 seconds, the compressed density of the powder of the negative electrode active material at a force of 20,000 N was recorded and calculated. The test standard was in accordance with GB / T24533-2009.

[0196] A certain amount of the prepared positive electrode active material sample was taken and placed in a mold with a base area of ​​1.327 cm2 in a UTM7305 type electronic pressure tester. A pressure of 2000 kg (equivalent to 20,000 N) was applied, and the pressure was maintained for 30 seconds. After the pressure was released and maintained for 10 seconds, the powder compression density of the positive electrode active material at a force of 20,000 N was recorded and calculated. The test standard was in accordance with GB / T24533-2009.

[0197] 2. Electrolyte viscosity test

[0198] After taking an appropriate amount of electrolyte sample and cleaning the sample cup and rotor in order, take an appropriate amount of electrolyte and place it in the sample cup, keep the temperature constant at 25℃, and measure the viscosity of the DV-2TLV viscometer (calculation formula is FSR=TK * SMC * The test was performed using a 18# rotor at 70 rpm (10,000 RPM), with the electrolyte and organic solvent fixed, and the data collection mode selected was Multi-Point Average, which automatically recorded and detected the results. The test standard was in accordance with GB / T10247-2008.

[0199] 3. Secondary battery performance testing

[0200] 3.1 Testing the cycle performance of secondary batteries

[0201] (1) Testing the room temperature cycle performance of secondary batteries

[0202] The secondary battery was charged at 25°C at a constant current of 1C to 4.4V, and then continued to be charged at a constant voltage until the current reached 0.05C. At this point, the secondary battery was fully charged. The charge capacity at this point was recorded, i.e., the first-cycle charge capacity. After allowing the secondary battery to stand for 5 minutes, it was discharged at a constant current of 1C to 2.8V. This constitutes one cycle of charge-discharge. The discharge capacity at this point was recorded, i.e., the first-cycle discharge capacity. The secondary battery was subjected to a cycle charge-discharge test according to the above method, and the discharge capacity after each cycle was recorded. The capacity retention rate (%) of the secondary battery after 600 cycles at 25°C = discharge capacity after 600 cycles / discharge capacity at first cycle × 100%.

[0203] 3.2 Safety performance testing of secondary batteries

[0204] At 25°C, the secondary battery is charged to 4.3V at a constant current of 1C, and then continues charging at a constant voltage until the current drops to 0.05C, at which point the secondary battery is fully charged. The fully charged secondary battery is placed in a sealed high-temperature box, heated to 100°C at 5°C / min, held for 1 hour, then heated to 105°C at 5°C / min, held for 30 minutes, and then heated at a rate of 5°C / min for every 5°C increase, held for 30 minutes, until the secondary battery expires. max Recorded. T max The higher the value, the better the thermal box safety performance of the secondary battery.

[0205] To ensure the reliability of the test results, each test above can be performed using at least three parallel samples, and the average value can be used as the test result.

[0206] 3.3 Testing the DC resistance (DCR) of secondary battery cells

[0207] DCR test at 25°C: First, a capacity test was performed. The specific operating procedure was to leave the secondary battery at 25°C for 2 hours using a constant current charge / discharge tester, charge it at a rate of 0.33C up to 4.4V, then charge it at a constant voltage until the current became less than 0.05C, leave it for 5 minutes, and then discharge it to 2.8V. The discharge capacity at this time was recorded and used as the initial capacity of the secondary battery. The remaining battery charge (expressed as SOC, calculated as remaining battery charge / initial charge x 100%) was then measured and a DCR test was performed. The battery was first fully charged to 4.4V at 0.33C, then charged to 4.4V at a constant voltage until the current dropped below 0.05C. It was then fully discharged at 0.05C for 1 hour and then discharged at a constant current to adjust the secondary battery to 50% SOC. The secondary battery's voltage was designated U1. The secondary battery was then discharged at a constant current of 4C I1 for 30 seconds, with 0.1-second sampling intervals. The end-of-discharge voltage was designated U2. The discharge DC internal resistance of the secondary battery at 50% SOC represents the initial DC internal resistance of the secondary battery, which is calculated as (U1 - U2) / I1 (mΩ).

[0208] Test results

[0209] The present application shows in Tables 6 to 10 the effects of improving the cycle performance, safety performance and dynamic performance of secondary batteries.

[0210] [Table 6]

[0211] As can be seen from Table 6, the attachment of the solid electrolyte to the electrode sheet improves the safety performance of the secondary battery, but the kinetics of interfacial transport of lithium ions is poor and the interfacial impedance is large, as can be seen from Comparative Examples 1 and 2. In Examples 1 to 2-12, by controlling the mass percentages of the polymer matrix and the first additive in the solid electrolyte to be within an appropriate range, for example, 0.1≦B / A≦19, preferably 0.5≦B / A≦10, the impedance of the secondary battery can be significantly improved, its kinetic performance can be improved, and the cycle performance and safety performance of the secondary battery can also be improved.

[0212] [Table 7]

[0213] As can be seen from Table 7, the performance of the secondary battery can be adjusted by adjusting the mass percentage ratio of the boron-containing lithium salt in the first additive to the negative electrode film-forming additive. In particular, when 0.002≦B1 / B2≦10, the cycle performance and dynamic performance of the secondary battery are significantly improved.

[0214] [Table 8]

[0215] As can be seen from Table 8, the performance of the secondary battery can be adjusted by adjusting the correlation between the mass percentage of the electrolyte film-forming additive and the lithium salt in the electrolyte and the viscosity of the electrolyte. In particular, when 0.2≦E / (D1+D2)≦2.95, the cycle performance and dynamic performance of the secondary battery are significantly improved.

[0216] [Table 9]

[0217] As can be seen from Table 9, by adjusting the correlation between the positive electrode film layer and the solid electrolyte, the protective power of the solid electrolyte against the positive electrode film layer can be adjusted, and the performance of the secondary battery can be adjusted. In particular, when 5≦h1 * P1 / m≦250, preferably 70≦h1 * When P1 / m≦250, the cycle performance and dynamic performance of the secondary battery are obviously improved.

[0218] [Table 10]

[0219] As can be seen from Table 10, the performance of the secondary battery can be adjusted by adjusting the correlation between the negative electrode film layer and the solid electrolyte, and by adjusting the protective power of the solid electrolyte against the negative electrode film layer. In particular, 5≦h1 * P1 / m≦250, preferably 25≦h2 * When P2 / m≦245, the cycle performance and dynamic performance of the secondary battery are obviously improved.

[0220] Although the present application has been described above with reference to preferred embodiments, various modifications may be made without departing from the scope of the present application, and some of the components may be replaced with equivalents. In particular, as long as there is no structural contradiction, the technical features described in each embodiment may be arbitrarily combined. The present application is not limited to the specific embodiments disclosed above, but includes all aspects encompassed by the scope of the claims.

Claims

1. A secondary battery, a positive electrode sheet including a positive electrode film layer; a negative electrode sheet including a negative electrode film layer; An electrolyte; a solid electrolyte provided on the surface of the positive electrode film layer and / or the negative electrode film layer, the solid electrolyte including a polymer matrix and a first additive, the first additive being arranged to form an interfacial film on the surface of the positive electrode film layer and / or the negative electrode film layer; The first additive is A boron-containing lithium salt having a mass percentage of B1% relative to the total mass of the solid electrolyte; a negative electrode film-forming additive containing one or more additives selected from the group consisting of a carbonate ester-based additive, a sulfate ester-based additive, and a sulfite ester-based additive, and having a mass percentage of B2% relative to the total mass of the solid electrolyte; The mass percentage of the polymer matrix relative to the total mass of the solid electrolyte is A %, The mass percentage of the first additive relative to the total mass of the solid electrolyte is defined as B %, The secondary battery satisfies 0.1≦B / A≦19 and 0.002≦B1 / B2≦10.

2. The secondary battery according to claim 1 , wherein the secondary battery satisfies 5≦A≦99 and / or 0.1≦B≦95.

3. The secondary battery according to claim 1 , wherein the secondary battery satisfies 0.1≦B1≦50 and / or 0.1≦B2≦50.

4. The molecular formula of the boron-containing lithium salt is LiBF ａ O ｂ C ｃ P ｄ 2. The secondary battery according to claim 1, wherein in the molecular formula, 0≦a≦4, 0≦b≦8, 0≦c≦4, and 0≦d≦4.

5. The carbonate ester-based additive includes a cyclic carbonate ester solvent and / or a chain carbonate ester solvent, and / or The sulfate ester additive includes a cyclic sulfonate ester additive and / or a hydrocarbon group sulfate ester additive, and / or The secondary battery according to claim 1 , wherein the sulfite ester additive comprises ethylene sulfite ES and / or vinyl ethylene sulfite VES.

6. The electrolyte solution is a cyclic carbonate solvent having a mass percentage of M1% relative to the total mass of the electrolyte; a chain carbonate ester solvent having a mass percentage of M2% relative to the total mass of the electrolyte solution; The secondary battery is 10 －３ The secondary battery according to claim 1 , wherein M1 / M2≦2 is satisfied.

7. The cyclic carbonate solvent comprises one or more of ethylene carbonate EC, propylene carbonate PC, vinylene carbonate VC, fluoroethylene carbonate FEC, difluoroethylene carbonate DFEC, vinylethylene carbonate VEC, and dioctyl carbonate CC; and / or The chain carbonate ester solvent includes one or more of ethyl allyl carbonate AEC, diphenyl carbonate DPC and methyl allyl carbonate MAC, polycarbonate PC, diethyl carbonate DEC, ethyl methyl carbonate EMC, methyl propyl carbonate MPC, ethyl propyl carbonate EPC, and methyl butyl carbonate MBC, and / or 7. The secondary battery of claim 6, comprising one or more of methyl acetate MA, ethyl acetate EA, methyl propionate MP, and ethyl propionate EP.

8. The electrolyte solution is an electrolyte film-forming additive having a mass percentage of D1% relative to the total mass of the electrolyte; A lithium salt having a mass percentage of D2% relative to the total mass of the electrolyte solution, 5. The secondary battery according to claim 1, wherein the secondary battery satisfies 0.2≦E / (D1+D2)≦2.95, in which E represents the viscosity of the electrolyte solution, and its unit is mPa s.

9. The percentage of the solid mass content of the solid electrolyte solution relative to the liquid mass content is m; The compressed density of the positive electrode film layer is set to P1g / cm ３ year, The thickness of the positive electrode film layer is h 1 μm, The secondary battery has a temperature of 5≦h1 ＊ The secondary battery according to claim 1 , wherein P1 / m≦250 is satisfied.

10. The percentage of the solid mass content of the solid electrolyte solution relative to the liquid mass content is m; The compressed density of the negative electrode film layer is set to P2 g / cm ３ year, The thickness of the negative electrode film layer is h2 μm, The secondary battery has a temperature of 25≦h2 ＊ The secondary battery according to claim 1 , wherein P2 / m≦245 is satisfied.

11. A battery module comprising the secondary battery according to claim 1 .

12. A battery pack comprising the battery module according to claim 11.

13. A power consuming device comprising: the secondary battery according to claim 1 ; the battery module according to claim 11 ; or the battery pack according to claim 12 .

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