Secondary batteries and electrical devices

Abstract

This application discloses a secondary battery and an electrical device. The secondary battery includes a positive electrode sheet, a negative electrode sheet, a separator, and an electrolyte. The negative electrode sheet has a non-Faraday capacity of Cdl nF, satisfying 1≦Cdl≦5. The electrolyte contains an additive, which includes a silicon-containing compound. By appropriately adjusting the relationship between the non-Faraday capacity of the negative electrode sheet and the content of the additive in the electrolyte, the resulting lithium-ion secondary battery has high capacity and fast charging.

Description

[Technical Field]

[0001] This application claims priority from a Chinese patent application filed with the China Patent Office on September 26, 2022, with application number 202211175108.5, entitled "Secondary Battery and Electrical Device," the entire contents of which are incorporated herein by reference.

[0002] The present application relates to the field of secondary battery technology, and more particularly to secondary batteries and electrical-using devices. [Background technology]

[0003] Currently, secondary batteries such as lithium-ion batteries occupy a leading position in the new energy field, and market demand is rapidly increasing year by year. High-energy density and high-voltage lithium-ion secondary batteries are attracting attention. For example, to provide electric vehicles with the characteristics of short charging times and long driving ranges, lithium-ion secondary batteries must have fast charging times and high capacity.

[0004] Therefore, it is necessary to provide a secondary battery that can solve the above problems. Summary of the Invention [Problem to be solved by the invention]

[0005] The present application provides a secondary battery and an electrical device, which overcome the difficult problem of achieving both high-speed charging and high capacity in a secondary battery. [Means for solving the problem]

[0006] The secondary battery according to the first embodiment of the present invention includes a positive electrode sheet, a negative electrode sheet, a separator, and an electrolyte solution, and the non-Faraday capacitance value of the negative electrode sheet is Cdl nF, which satisfies 1≦Cdl≦5. The electrolyte solution includes an additive, and the additive includes a silicon-containing compound.

[0007] Preferably, in another embodiment of the present application, the silicon-containing compound comprises at least one of tris(trimethylsilyl)phosphate, tris(trimethylsilane)phosphite, trimethylfluorosilane, or tris(trimethylsilane)borate.

[0008] Preferably, in another embodiment of the present application, the mass percentage of the silicon-containing compound is A%, based on the total mass of the electrolyte, and satisfies 0.01≦A≦5.

[0009] Preferably, in another embodiment of the present application, the mass percentage of the silicon-containing compound is A%, based on the total mass of the electrolyte, and satisfies 0.01≦10×Cdl×A%≦2.5.

[0010] Preferably, in another embodiment of the present application, the compressed density of the negative electrode sheet is PD g / cm 3 and satisfies 1.1≦PD≦1.7.

[0011] Preferably, in another embodiment of the present application, the OI value of the negative electrode sheet is 2 to 25.

[0012] Preferably, in another embodiment of the present application, the electrolyte has a surface tension of F mN / m at room temperature, satisfies 20≦F≦40, and the room temperature is 20°C to 25°C.

[0013] Preferably, in another embodiment of the present application, the internal resistance of the secondary battery is R mΩ, and satisfies 0.02≦R≦0.8.

[0014] Preferably, in another embodiment of the present application, 1.1≦Cdl+R×F / 10≦8.

[0015] Preferably, in another embodiment of the present application, the negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer disposed on the negative electrode current collector, the negative electrode active material layer including a negative electrode active material, and the negative electrode active material includes one or more of artificial graphite, natural graphite, amorphous carbon, carbon nanotubes, or mesocarbon microspheres.

[0016] An electricity-using device according to a second embodiment of the present application includes the above-described secondary battery. [Effects of the Invention]

[0017] The secondary battery according to the embodiment of the present application has at least the following technical effects.

[0018] (1) By adjusting the non-Faraday capacitance value Cdl of the negative electrode sheet, the present invention accelerates the non-Faraday process of the negative electrode sheet, improves the reaction activity, and provides better kinetic performance.

[0019] (2) By adding a silicon-containing compound additive to the electrolyte, a stable passivation film can be formed at the interface between the positive and negative electrodes, reducing the impedance of the electrolyte and the interface. The non-Faraday capacitance value Cdl of the negative electrode sheet is within the above range. In addition, adding a silicon-containing compound to the electrolyte can effectively suppress side reactions between the negative electrode sheet and the electrolyte, keeping the reaction between the reactive sites of the negative electrode sheet and the electrolyte within an appropriate range. This gives the battery fast charging capability, optimizes the charging time period, and provides excellent power performance. [Brief explanation of the drawings]

[0020] In order to more clearly describe the technical solutions in the embodiments of the present application, the drawings used in the description of the embodiments are briefly described below. However, the drawings in the following description are only embodiments of the present application, and it is obvious that those skilled in the art can obtain other drawings based on these drawings without inventive efforts.

[0021] [Figure 1] 1 is a fitting curve showing a scan rate-current scatter diagram of the negative electrode sheet prepared in Example 1 of the present application. DETAILED DESCRIPTION OF THE INVENTION

[0022] The technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the accompanying drawings, but it is clear that the described embodiments are only a part of the embodiments of the present application, and are not all of the embodiments. Based on the embodiments of the present application, all other embodiments that can be obtained by those skilled in the art without inventive efforts fall within the scope of protection of the present application.

[0023] The present invention provides a secondary battery and an electricity-using device according to the present invention. Each of the secondary battery and the electricity-using device will be described in detail below. Note that the order in which the following examples are described does not limit the preferred order of the examples.

[0024] In the description and claims, a list of items connected by the term "at least one" can refer to any combination of the listed items. For example, when listing items A and B, the phrase "at least one of A and B" means A only, B only, or A and B. In other examples, when listing items A, B, and C, the phrase "at least one of A, B, and C" means A only, B only, C only, A and B (excluding C), A and C (excluding B), B and C (excluding A), or all of A, B, and C. Item A can include a single element or multiple elements. Item B can include a single element or multiple elements. Item C can include a single element or multiple elements. The term "at least one" has the same meaning as the term "at least one."

[0025] In this specification, a numerical range indicated using "to" indicates that the range includes the numerical values ​​before and after "to" as the minimum and maximum values, respectively.

[0026] In one embodiment, the present application provides a secondary battery, which includes a positive electrode sheet, a negative electrode sheet, a separator, and an electrolyte.

[0027] I, negative electrode sheet The negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer disposed on the negative electrode current collector.

[0028] In some embodiments of the present application, the non-Faradaic capacity of the negative electrode sheet is Cdl nF, satisfying the condition 1≦Cdl≦5. Currently, increasing the coating weight to achieve high energy density in secondary batteries increases the battery's energy density, but this can affect the battery's long-term reliability. In secondary batteries, such as lithium-ion batteries, if lithium ions are not rapidly absorbed and released into the negative electrode active material during high-rate charging or high-rate discharging, lithium deposition occurs, forming lithium dendrites that may penetrate the microporous polymer separator and cause an internal short circuit. Lithium deposition on the negative electrode sheet consumes lithium ions in the battery, rapidly reducing battery capacity and degrading the battery's cycle performance. High charge and discharge currents also increase the amount of heat generated by the battery's internal resistance, potentially leading to safety issues such as thermal runaway, combustion, and explosion. The present application adjusts the non-Faradaic capacity Cdl of the negative electrode sheet to accelerate the non-Faradaic processes of the negative electrode sheet, improving reaction activity and improving kinetic performance. The negative electrode sheet of the present application has high capacity, high fold-rate performance, and is less susceptible to side reactions with the electrolyte, thereby providing lithium-ion batteries with high durability and cycle stability. The non-Faraday capacity value Cdl of the negative electrode sheet can be modified by adjusting the negative electrode active material form, negative electrode sheet compression density, negative electrode sheet OI value, negative electrode sheet composition, and negative electrode slurry processing methods, thereby adjusting the number of reactive sites on the negative electrode sheet and affecting battery performance. It is sufficient to achieve the non-Faraday capacity of the negative electrode sheet within the above range through these adjustment methods.

[0029] Specifically, Cdl may be any one of 1, 1.5, 1.9, 2.2, 2.7, 3.1, 3.4, 3.6, 4.5, and 5, or a range consisting of any two of these numbers. In some embodiments of the present application, 1.5≦Cdl≦4.5. In some embodiments of the present application, 1.9≦Cdl≦3.6. The electrochemical reactions include a change in the oxidation state of the active material, a Faradaic reaction of charge transfer into the active material, and a Faradaic reaction of charge storage and release due to physical adsorption and desorption of ions on the active material surface. The Faradaic reaction is when the oxidation state of the active material changes and charge passes through a double charge layer to transfer into the active material through the electrode interface. The non-Faradaic reaction is when charge storage and release occurs due to physical adsorption and desorption of ions on the electrode surface, without charge transfer across the electrode interface. When Cdl is within the above range, the non-Faradaic process of the negative electrode sheet is accelerated, resulting in higher reaction activity and better kinetic performance. The manufactured lithium ion battery can be rapidly charged at a large rate, has excellent safety performance, and has excellent cycle performance.

[0030] The non-Faraday capacity value of the negative electrode sheet can be obtained by testing the negative electrode sheet overhang area in a secondary battery using a non-Faraday capacity test method. The negative electrode sheet overhang area refers to the portion of the negative electrode sheet that extends beyond the positive electrode sheet in the length and width directions. The non-Faraday capacity value of the negative electrode sheet can be obtained by testing the negative electrode sheet before it is assembled into a battery.

[0031] Compressed Density In some embodiments of the present application, the compressed density of the negative electrode sheet is PD g / cm 3The range of PD satisfies 1.1≦PD≦1.7, and may be, for example, 1.1, 1.2, 1.3, 1.5, 1.6, or 1.7, or may be a range consisting of any two of these numbers. In some embodiments of the present application, 1.3≦PD≦1.6. When the compaction density is within the above range, the integrity of the negative active material granules is further improved, the occurrence of granule crushing after rolling is reduced, and the increase in side reactions during battery cycling is reduced, avoiding the impact on the battery cycle life. Furthermore, when the non-Faraday capacitance value of the negative electrode sheet is 1 nF to 5 nF and the compaction density is within the above range, the electrical contact between the negative active material granules is improved, which is favorable for lithium ion migration, increasing the current consistency of the negative electrode sheet and delaying battery polarization. At the same time, the gap between the negative active material granules can be within an appropriate range, which allows the negative active material granules to have a relatively intact structure and improves electrolyte infiltration, thereby improving dynamic performance. When the packing density of the negative electrode sheet is changed, the physical contact between the granules in the negative electrode sheet changes, and the pore spaces between the granules in the negative electrode sheet change, which in turn affects the non-faradaic capacity of the negative electrode sheet.

[0032] OI value In some embodiments of the present application, the OI value of the negative electrode sheet is 2 to 25. For example, the OI value may be any one of 2, 4, 5, 6, 7, 10, 11, 15, 20, and 25, or a range consisting of any two of these numbers. In some embodiments of the present application, the OI value of the negative electrode sheet may be 4 to 20. In some embodiments of the present application, the OI value of the negative electrode sheet may be 5 to 15. The OI value (C004 / C110) of the negative electrode sheet can be measured using X-ray diffraction (XRD). The OI value of the negative electrode sheet can represent the crystalline orientation index of the negative electrode active material layer, where C004 is the peak intensity of the 004 characteristic diffraction peak in the X-ray diffraction pattern of the negative electrode active material layer, and C110 is the peak intensity of the 110 characteristic diffraction peak in the X-ray diffraction pattern of the negative electrode active material layer. Changing the OI value of the negative electrode sheet can affect the lithium ion transport pathway. During the lithium absorption process, lithium ions enter the interlayer spaces of the graphite anode material from the edge surfaces and undergo solid-state diffusion between the layers to complete the lithium absorption process. Therefore, the highly isotropic graphite edge surfaces are exposed to the surface of the anode sheet, shortening the lithium ion transition path and favoring the rapid migration of lithium ions, accelerating the electrochemical reaction kinetics, and thereby further achieving high-rate lithium ion discharge performance. In addition, excellent isotropy can suppress the expansion of the graphite interlayers, improving cycle performance. Therefore, when the OI value is within the above range, the effects of improved fast charging, reduced swelling, and improved cycle performance can be achieved.

[0033] Test method for non-Faraday capacitance Testing the non-faradaic capacity of the negative electrode sheet includes the following steps.

[0034] S1: To confirm the non-Faraday potential range, the negative electrode sheet is assembled into a button-type half cell (abbreviated as button cell) and subjected to a cyclic voltammogram (CV) test, where the voltage range is 0.005 to 3.0 V and the scan rate is 0.1 to 1 mV / s.

[0035] S2: For the cathodic scan in the non-Faraday section, select the potential range of S1 and perform a linear scan voltammogram (LSV) test. The scan direction is from high potential to low potential, and the voltage-current curve is collected. Here, the voltage range is 2.5 V to 2.6 V, and the scan rate is 0.05 mV / s to 5 mV / s. Then, select the midpoint U of the potential range at a specific scan rate V, and obtain the corresponding current value.

[0036] S3: To calculate the non-Faraday capacity, a linear function is obtained by fitting based on the scan rate-current scatter diagram collected in step S2, and the slope K of the linear function is the Cdl value of the negative electrode sheet in the cathode scan direction.

[0037] Furthermore, the button battery includes a positive electrode housing, a negative electrode sheet, a separator, an electrolyte, a lithium sheet, and a negative electrode housing.

[0038] The resulting negative electrode sheet is then dried, cut into small circular sheets, weighed, and transferred to a vacuum oven where it is dried at 90-110°C for 7-9 hours. The resulting sheets are then transferred to a glove box filled with argon gas for assembly into half-cells, resulting in button batteries. This button battery assembly process is standard in the art.

[0039] Negative electrode current collector In some embodiments, the negative electrode current collector includes, but is not limited to, a metal foil, a metal cylinder, a metal tape roll, a metal sheet, a metal thin film, a metal sheet mesh, a metal stamping, a metal foam, etc. In some embodiments, the negative electrode current collector is a metal foil. In some embodiments, the negative electrode current collector is an aluminum foil or a copper foil. As used herein, the term "copper foil" includes copper alloy foil.

[0040] In some embodiments, the negative electrode current collector is a conductive resin, hi some embodiments, the conductive resin comprises a film obtained by depositing copper on a polypropylene film.

[0041] Negative active material layer The negative electrode active material layer may be a single layer or multiple layers, and each of the multiple layers may contain the same or different negative electrode active materials. The negative electrode active material is any material that can reversibly store and release metal ions, such as lithium ions. In some embodiments, the chargeable capacity of the negative electrode active material is greater than the dischargeable capacity of the positive electrode active material to prevent lithium metal deposition on the negative electrode during charging.

[0042] In some embodiments, the thickness of the negative electrode active material layer refers to the thickness of the negative electrode active material layer coated on one side of the negative electrode current collector. In some embodiments, the thickness of the negative electrode active material layer on one side is 15 μm or more. In some embodiments, the thickness of the negative electrode active material layer is 20 μm or more. In some embodiments, the thickness of the negative electrode active material layer is 30 μm or more. In some embodiments, the thickness of the negative electrode active material layer is 150 μm or less. In some embodiments, the thickness of the negative electrode active material layer is 120 μm or less. In some embodiments, the thickness of the negative electrode active material layer is 100 μm or less. In some embodiments, the thickness of the negative electrode active material layer falls within a range consisting of any two of the above numbers. When the thickness of the negative electrode active material layer falls within the above range, the electrolyte can penetrate to the vicinity of the interface of the negative electrode current collector, improving the charge / discharge characteristics of the electrochemical device at high current densities. At the same time, by maintaining the volume ratio of the negative electrode active material to the negative electrode current collector within an appropriate range, the capacity of the secondary battery can be ensured.

[0043] The negative electrode active material layer contains a negative electrode active material, a conductive agent, an adhesive, an additive, and a solvent.

[0044] 1. Conductive agent In some embodiments of the present application, the conductive agent comprises one or more of conductive carbon black, conductive graphite, carbon fiber, carbon nanotubes, or graphene.

[0045] 2, negative electrode active material In some embodiments of the present application, the negative electrode active material includes one or more of artificial graphite, natural graphite, soft carbon, hard carbon, amorphous carbon, carbon nanotubes, or mesocarbon microspheres.

[0046] 3. Adhesive The negative electrode active material layer contains a negative electrode adhesive, which improves adhesion between the negative electrode active materials. The type of adhesive is not particularly limited, as long as it is a material that is stable against the electrolyte solution and the solvent used in manufacturing the electrode.

[0047] Manufacture of negative electrode sheets The negative electrode sheet in the secondary battery of the present application can be produced by any known method, for example, by preparing a negative electrode slurry from a negative electrode active material, a conductive agent, an adhesive, an additive, and a solvent in specific proportions, coating the negative electrode slurry on a negative electrode current collector, and rolling and cutting the coated negative electrode sheet.

[0048] II, electrolyte The electrolyte solution contains a lithium salt, an organic solvent, and an additive, the additive containing a silicon-containing compound. The present application provides a lithium-ion secondary battery with high capacity and fast charging by appropriately adjusting the relationship between the non-Faraday capacity of the negative electrode sheet and the content of the additive in the electrolyte solution.

[0049] additives The present secondary battery incorporates an additive containing a silicon-containing compound in the electrolyte, which simultaneously forms a stable passivation film at the positive and negative electrode interfaces, reducing the interfacial resistance between the electrolyte and the electrolyte and effectively suppressing side reactions between the positive or negative electrode sheet and the electrolyte. When the non-Faraday capacitance of the negative electrode sheet is 1 nF to 5 nF and the electrolyte contains a silicon-containing compound, the silicon-containing compound possesses nucleophilic and alkaline lone pairs of electrons, which adjust the hydrogen fluoride (HF) content, reducing the battery's internal resistance and improving charging speed. Meanwhile, the silicon-containing compound forms a film on the negative electrode due to its electron-deficient central atom, increasing the ionic conductivity of the solid electrolyte interfacial (SEI) film, accelerating lithium ion transport, endowing the battery with fast charging capabilities, optimizing the lithium deposition window, and providing excellent power performance. When the present electrolyte is applied to a lithium-ion battery together with the present negative electrode sheet, it not only improves the cycle performance of the lithium-ion battery but also improves its charging performance.

[0050] In some embodiments of the present application, the silicon-containing compound includes at least one of tris(trimethylsilane)phosphate (TMSP), tris(trimethylsilane)phosphite (TMSPi), trimethylfluorosilane, and tris(trimethylsilane)borate (TMSB), which can interact well with the negative electrode sheet and form a passivation film with stable properties and specific density on the surface of the negative electrode sheet of a lithium ion battery, effectively inhibiting side reactions between the electrode and the electrolyte, reducing the surface tension of the electrolyte, improving the compatibility between the electrode and the electrolyte interface, and improving the cycle performance and safety of the lithium ion battery.

[0051] In some embodiments, the mass percentage of the silicon-containing compound is A% based on the total mass of the electrolyte, and satisfies 0.01≦A≦5, e.g., 0.01, 0.1, 0.5, 0.7, 1, 1.5, 1.8, 2.2, 2.7, 3, 4, 5, or a range consisting of any two of these numbers. In some embodiments, 0.1≦A≦4. In some embodiments, 0.5≦A≦3. When the mass percentage of the silicon-containing compound is 0.01% or less, the film-forming ability is insufficient, limiting the improvement of lithium-ion performance. When the mass percentage of the silicon-containing compound is 5% or more, the formed film becomes too dense, resulting in a slower lithium-ion release rate, increased polarization, and poor cycle performance of the lithium-ion battery.

[0052] In some embodiments, the mass percentage of the silicon-containing compound is A%, based on the total mass of the electrolyte, and satisfies 0.01≦10×Cdl×A%≦2.5, and may be, for example, 0.02, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.8, 1.1, 2.2, or a range consisting of any two of these numbers. In some embodiments, 0.02≦10×Cdl×A%≦2.2. In some embodiments, 0.1≦10×Cdl×A%≦1.1.

[0053] surface tension In some embodiments of the present application, the surface tension of the electrolyte is F mN / m at room temperature, satisfying the relationship 20≦F≦40, and the room temperature is 20°C to 25°C. For example, F may be 20, 25, 30, 35, or 40, or a range consisting of any two of these numbers. In some embodiments of the present application, 25≦F≦35. The surface tension of a liquid refers to the force acting on the surface of the liquid to reduce its surface area. The degree of electrolyte infiltration affects the performance of lithium-ion batteries, and methods for improving this include changing the solvent system and using additives. When the surface tension of the electrolyte is within the above range, the infiltration effect of the sheet can be accelerated, improving the uniformity of electrolyte distribution and dynamic equilibrium ability, increasing the infiltration rate, which helps reduce battery resistance, improving battery reaction kinetics, and providing lithium-ion batteries with good power consumption. An electrolyte with the above surface tension provides a good interface for the negative electrode coating layer, which is advantageous for improving the cycle performance of electrochemical devices. Furthermore, shortening the wetting time also leads to improved productivity. The surface tension of the electrolyte can be measured using the SY / T5370-2018 Surface and Interfacial Tension Measurement Method. The test settings are: total time 10.0 s, start / pause 0.0 s, final frame rate 10% (33 FPS), pipette tip size 300 μL, and droplet volume 6 μL.

[0054] In some embodiments of the present application, 1.1≦Cdl+R×F / 10≦8 may be, for example, 1.1, 1.5, 2, 3, 5, 7, or 8, or a range consisting of any two of these numbers. In some embodiments of the present application, 1.5≦Cdl+R×F / 10≦6. In some embodiments of the present application, 1.9≦Cdl+R×F / 10≦4.5. When the non-Faraday capacity value of the negative electrode sheet, the internal resistance of the secondary battery, and the surface tension of the electrolyte satisfy the above numerical ranges, the negative electrode sheet has relatively high electron and lithium ion transport performance, thereby realizing relatively high charge and discharge performance at a high rate of charging and discharging, and thus providing excellent overall performance to the lithium ion battery.

[0055] organic solvents In some embodiments of the present application, the electrolyte further comprises any organic solvent known in the art that can act as a solvent for the electrolyte, hi some embodiments, the organic solvent comprises a carbonate-based solvent, the carbonate-based solvent comprising at least two of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, and polycarbonate.

[0056] lithium salts In some embodiments of the present application, the lithium salt comprises at least one of lithium hexafluorophosphate, lithium organoborate, lithium perchlorate, and sulfonimide-type lithium salts.

[0057] The content of the lithium salt is not particularly limited as long as it does not impair the effects of the present application. In some embodiments of the present application, the molar concentration of the lithium salt may be 0.5 mol / L to 2 mol / L, 1 mol / L to 1.8 mol / L, or 1.2 mol / L to 1.5 mol / L, based on the total volume of the electrolyte solution. When the concentration of the lithium salt is within the above range, the amount of lithium ions, which are charged ions, is not too small, and the viscosity can be kept within an appropriate range, making it easier to ensure excellent conductivity.

[0058] additives In some embodiments of the present application, the additive comprises a sulfur-oxygen double bond-containing compound, such as 1,3-propane sultone, vinyl sulfate, vinyl sulfite, and the like.

[0059] In some embodiments of the present application, the additive comprises a cyclic carbonate containing an unsaturated double bond, such as vinylene carbonate, ethylene vinyl carbonate, and the like.

[0060] III. Positive electrode sheet The positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer disposed on the positive electrode current collector.

[0061] Cathode active material layer The positive electrode active material layer may be a single layer or multiple layers. Each of the multiple negative electrode active material layers may contain the same or different positive electrode active materials. The positive electrode active material is any material that can reversibly store and release metal ions, such as lithium ions.

[0062] The positive electrode active material layer contains a positive electrode active material, a positive electrode conductive agent, a positive electrode adhesive, and a solvent.

[0063] 1. Positive electrode active material The type of positive electrode active material is not particularly limited as long as it can electrochemically absorb and release metal ions (e.g., lithium ions). In some embodiments of the present application, the positive electrode active material includes one or more of lithium iron phosphate (LFP) and a ternary material.

[0064] In some embodiments of the present application, the active cathode material includes a ternary material, wherein the ternary material includes lithium nickel cobalt manganese oxide and / or lithium nickel cobalt aluminum oxide.

[0065] In some embodiments of the present application, the molar ratio of nickel, cobalt and manganese in the lithium nickel cobalt manganese oxide is 1:1:1, and the content of nickel is 0.5 or more.

[0066] In some embodiments of the present application, the molar ratio of nickel, cobalt, and manganese in the lithium nickel cobalt manganese oxide is 1:1:1, and the content of nickel is less than or equal to 0.85.

[0067] In some embodiments of the present application, the positive electrode active material further includes a doping element and / or a coating element.

[0068] In some embodiments of the present application, the content of the positive electrode active material may be 80% to 98%, 85% to 96%, or 90% to 95%, based on the weight of the positive electrode active material layer. In some embodiments, the content of the positive electrode active material may be within a range consisting of any two of the above numbers, based on the weight of the positive electrode active material layer. When the content of the positive electrode active material is within the above range, the strength of the positive electrode sheet can be maintained while ensuring the content of the positive electrode active material in the positive electrode active material layer.

[0069] 2. Positive electrode conductive agent The type of positive electrode conductive agent is not particularly limited, and any known conductive agent can be used. Examples of positive electrode conductive agents include, but are not limited to, carbon materials such as natural graphite, artificial graphite, acetylene black, acicular coke, carbon nanotubes, and graphene. The above positive electrode conductive agents may be used alone or in any combination.

[0070] 3. Positive electrode adhesive The type of positive electrode adhesive used in manufacturing the positive electrode active material layer is not particularly limited, and in the case of a coating method, it may be a material that is soluble or dispersible in the liquid medium used in manufacturing the electrode. Examples of positive electrode adhesives may include, but are not limited to, one or more of the following: These include resin-based polymers such as polyethylene, polypropylene, polyethylene terephthalate, polymethyl methacrylate, polyimide, aromatic polyamide, cellulose, and nitrocellulose; rubber-like polymers such as styrene-butadiene rubber (SBR), nitrile rubber (NBR), fluororubber, isoprene rubber, polybutadiene, and ethylene-propylene rubber; thermoplastic elastomeric polymers such as styrene-butadiene-styrene block copolymers and their hydrogenated products, ethylene-propylene-diene terpolymer (EPDM), styrene-ethylene-butadiene-ethylene copolymers, and styrene-isoprene-styrene block copolymers and their hydrogenated products; soft resin-like polymers such as syndiotactic 1,2-polybutadiene, polyvinyl acetate, ethylene-vinyl acetate copolymers, and propylene-α-olefin copolymers; fluoropolymers such as polyvinylidene fluoride (PVDF), polytetrafluoroethylene, polyvinylidene fluoride, and polytetrafluoroethylene-ethylene copolymers; and polymer compositions with ionic conductivity for alkali metal ions (especially lithium ions). The positive electrode adhesives may be used alone or in any combination.

[0071] 4. Solvent The type of solvent used to form the positive electrode slurry is not limited, and any solvent capable of dissolving or dispersing the positive electrode active material, positive electrode conductive agent, and positive electrode adhesive may be used. Examples of solvents used to form the positive electrode slurry include, but are not limited to, aliphatic hydrocarbons such as hexane; aromatic hydrocarbons such as benzene, toluene, xylene, and methylnaphthalene; heterocyclic compounds such as quinoline and pyridine; ketones such as acetone, methyl ethyl ketone, and cyclohexanone; esters such as methyl acetate and methyl acrylate; amines such as diethylenetriamine and N,N-dimethylaminopropylamine; ethers such as diethyl ether, propylene oxide, and tetrahydrofuran (THF); amides such as N-methylpyrrolidone (NMP), dimethylformamide, and dimethylacetamide; and aprotic polar solvents such as hexamethylphosphamide and dimethyl sulfoxide.

[0072] positive electrode current collector The type of positive electrode current collector is not particularly limited, and may be any known material suitable for use as a positive electrode current collector. Examples of positive electrode current collectors include, but are not limited to, metal materials such as aluminum, stainless steel, nickel plating, titanium, and tantalum, and carbon materials such as carbon cloth and carbon paper. In some embodiments, the positive electrode current collector is aluminum.

[0073] The shape of the positive electrode current collector is not particularly limited. When the positive electrode current collector is made of a metal material, the shape of the positive electrode current collector includes, but is not limited to, a metal foil, a metal cylinder, a metal tape roll, a metal plate, a metal thin film, a metal plate mesh, a stamped metal, a metal foam, etc. When the positive electrode current collector is made of a carbon material, the shape of the positive electrode current collector includes, but is not limited to, a carbon plate, a carbon thin film, and a carbon cylinder. In some embodiments, the positive electrode current collector is a metal foil. In some embodiments, the metal foil is in a mesh shape. The thickness of the metal foil is not particularly limited. In some embodiments, the thickness of the metal foil is 1 μm or more, 3 μm or more, or 5 μm or more. In some embodiments, the thickness of the metal foil is 1 mm or less, 100 μm or less, or 50 μm or less. In some embodiments, the thickness of the metal foil is within a range consisting of any two of the above numbers.

[0074] IV, separator To prevent short circuits, a separator is typically disposed between the positive electrode and the negative electrode. The material and shape of the separator are not particularly limited as long as they do not impair the effects of the present application. The separator may be a resin, glass fiber, inorganic material, or the like formed from a material stable in the electrolyte solution of the present application. In some embodiments, the separator includes a porous sheet-like or nonwoven fabric-like material with excellent liquid retention. Examples of materials for the resin or glass fiber separator include, but are not limited to, polyolefin, aromatic polyamide, polytetrafluoroethylene, polyethersulfone, and the like. In some embodiments, the polyolefin is polyethylene or polypropylene. In some embodiments, the polyolefin is polypropylene. The above separator materials may be used alone or in any combination.

[0075] Internal resistance of secondary batteries In some embodiments of the present application, the internal resistance of the secondary battery is R mΩ, and satisfies 0.02≦R≦0.8, for example, 0.02, 0.05, 0.1, 0.3, 0.5, 0.7, 0.8, or a range consisting of any two of these numbers. In some embodiments of the present application, 0.05≦R≦0.7. In some embodiments of the present application, 0.1≦R≦0.5. The internal resistance of the secondary battery can be measured by an AC impedance test using an electrochemical workstation. Here, the interference voltage is 5 mV and the frequency range is 100 kHz to 100 mHz.

[0076] V. Application An embodiment of the present application further provides an electricity-using device, which includes the above-described secondary battery pack.

[0077] The electricity-using device of the present application can be used in, but is not limited to, a backup power supply, a motor, an electric vehicle, an electric motorcycle, an electric-assisted bicycle, a bicycle, an electric tool, a large-scale home storage battery, and the like.

[0078] The following will explain this in conjunction with specific examples. Example 1 The battery manufacturing method provided in this embodiment includes the following steps.

[0079] 1) In the positive electrode sheet manufacturing step, the positive electrode active material (NCM811), positive electrode conductive agent (carbon black), and positive electrode adhesive (polyvinylidene fluoride) are mixed in a mass ratio of 96:2:2, and then mixed with a solvent to produce positive electrode slurry. The solvent is N-methylpyrrolidone (NMP). The resulting positive electrode slurry is uniformly coated on both sides of the positive electrode current collector aluminum foil, which is then dried at 120°C, rolled, and cut to obtain the positive electrode sheet.

[0080] 2) In the negative electrode sheet manufacturing step, the negative electrode active material, conductive agent, adhesive, and additives are uniformly mixed in a mass ratio of 96.5:1.5:1.5:0.5, and then mixed with deionized water to prepare a negative electrode slurry. The negative electrode active material is artificial graphite, the conductive agent is carbon black, the adhesive is styrene butadiene rubber, and the additive is sodium carboxymethyl cellulose. The mixture is stirred using a vacuum mixer to obtain a negative electrode slurry. The prepared negative electrode slurry is uniformly coated on both sides of the copper foil of the negative electrode current collector, baked and dried, and then rolled and cut to obtain a negative electrode sheet. The baking temperature is 90°C to 110°C, and the rolling density is 1.55 g / cm. 3 The OI value of the negative electrode sheet is adjusted to 6.5. The non-Faraday capacity of the negative electrode sheet can be adjusted to the values ​​shown in Table 1 by adjusting the state of the negative electrode active material in the negative electrode sheet, the stirring process, the rolling conditions, and other methods.

[0081] 3) In the electrolyte preparation step, ethylene carbonate (EC), methyl ethyl carbonate (EMC), and diethyl carbonate (EDC) are mixed in a mass ratio of 3:4:3, 0.1% tris(trimethylsilyl) phosphate ester and 1% vinylene carbonate are added, and then 1 mol / L LiPF6 is added and mixed uniformly to prepare the electrolyte, whose surface tension is 35 mN / m.

[0082] 4) In the manufacturing step of the lithium ion battery, the negative electrode sheet and positive electrode sheet manufactured using the above steps are dried, and then wound with a separator and an electric core, and the manufactured electric core is placed in a housing, and the separator is a PP film, and after injection and chemical formation, the lithium ion battery is manufactured.

[0083] 5) The non-Faraday capacity test steps are as follows: Step 1: Disassemble the lithium-ion battery in a glove box or dry room. Obtain the sheet from the negative electrode overhang region, soak it in dimethyl carbonate (DMC) solution, cut it, and then assemble it with a metallic lithium sheet into a button half-cell. Alternatively, obtain the negative electrode sheet that is not assembled into a battery, cut it, and then assemble it with a metallic lithium sheet into a button half-cell. Step 2: Perform a cyclic voltammogram (CV) test on the button battery in the voltage range of 0.005 V to 3.0 V, with a scan rate of 0.1 mV / s, ensuring that the non-Faraday potential range is 2.5 V to 2.6 V. In step 3, a linear scan voltammogram (LSV) test was performed from 2.6 V to 2.5 V at scan rates of 0.1 mV / s, 0.2 mV / s, 0.5 mV / s, 1 mV / s, and 2 mV / s, respectively. The midpoint of the potential range, 2.55 V, was selected, and the corresponding current values ​​were obtained: -7.87E-07 A, -9.94E-07 A, -1.80E-06 A, -3.03E-06 A, and -4.99E-06 A. In step 4, the scan rate-current scatter plot was plotted and fitted to obtain a linear function. As shown in Figure 1, the slope of the linear function, -2.22E-06, indicates that the cathode scan direction Cdl of the negative electrode sheet is 2.22 nF.

[0084] The parameters of the battery manufactured in this example are as follows: The compressed density of the negative electrode sheet after rolling is 1.55 g / cm 3 The sheet OI value is 6.5. The electrolyte is prepared by adding 0.1% tris(trimethylsilane) phosphate ester to the electrolyte, and its surface tension is 35 mN / m, and the non-Faraday capacity value of the lithium-ion battery is 2.22.

[0085] Examples 2 to 20 In Examples 2 to 20, lithium ion batteries were manufactured by the method of Example 1, except for the differences shown in Table 1 below.

[0086] Comparative Example 1 In Comparative Example 1, a lithium ion battery was manufactured by the method of Example 1, except for the following differences.

[0087] The compressed density of the negative electrode sheet after rolling is 1.05 g / cm 3 The sheet OI value is 20. The electrolyte does not contain any additives and its surface tension is 45 mN / m. The non-faradaic capacity value of the lithium-ion battery is 0.8.

[0088] Comparative Example 2 In Comparative Example 2, a lithium ion battery was manufactured according to the method of Example 1, except for the following differences.

[0089] The compressed density of the negative electrode sheet after rolling is 1.3 g / cm 3 The sheet OI value is 27. The electrolyte is prepared by adding 5.5% tris(trimethylsilane) phosphate ester to the electrolyte, and its surface tension is 15 mN / m. The non-Faraday capacity value of the lithium-ion battery is 5.3.

[0090] The Cdl values ​​in Examples 1 to 20 and Comparative Examples 1 and 2 can be changed by adjusting the form of the negative electrode active material, the compressed density of the negative electrode sheet, and the OI value of the negative electrode sheet, as long as they become the values ​​exemplified in this application.

[0091] The batteries obtained in Examples 1 to 20 and Comparative Examples 1 and 2 were subjected to a dynamic performance test, and the test method was as follows.

[0092] The lithium-ion battery was subjected to 10 charge-discharge cycles: 30 minutes at 25°C, full charge at 5C, 30 minutes at 25°C, full discharge at 1C, and 10 minutes at 25°C. The battery was then fully charged at 5C and left for 10 minutes. The lithium-ion battery was then disassembled, and the surface condition of the negative electrode sheet was observed. The area of ​​lithium deposition was recorded. The percentage of the area of ​​lithium deposition was calculated as follows: area of ​​lithium deposition / total area of ​​negative electrode sheet × 100%. The degree of lithium deposition was classified as no lithium deposition, slight lithium deposition, moderate lithium deposition, or severe lithium deposition. No lithium deposition indicates that the area of ​​lithium deposition on the surface of the negative electrode sheet is less than 3%. Light lithium deposition indicates that the area of ​​lithium deposition on the surface of the negative electrode sheet is 3% or more but less than 20% of the total area. Moderate lithium deposition refers to the area of ​​lithium deposition on the surface of the negative electrode sheet being 20% ​​to 70% of the total area, and severe lithium deposition refers to the area of ​​lithium deposition on the surface of the negative electrode sheet being more than 70% of the total area.

[0093] Cycle performance test method The secondary battery is subjected to a cycle test in which it is left at 25°C for 30 minutes, discharged at a constant current of 1C, left at rest for 10 minutes, charged at a constant current and constant voltage of 1C, and left at rest for 10 minutes, and then fully charged and fully discharged.The capacity retention rate after 2000 cycles is recorded.

[0094] Test method for surface tension of electrolyte For the test method of the surface tension of the electrolyte, refer to SY / T5370-2018 Surface and Interfacial Tension Measurement Method.

[0095] Test method for battery internal resistance The lithium-ion battery was left at 25°C for 30 min, charged at a constant current and constant voltage of 1 C with a cutoff current of 0.05 C, and then discharged at 1 C for 30 min to a 50% state of charge (SOC). Then, AC impedance measurements were performed using an electrochemical workstation, where the interference voltage was 5 mV and the frequency range was 100 kHz to 100 mHz.

[0096] The test results are shown in the table below. [Table 1(1)] [Table 1(2)] [Table 1(3)]

[0097] Referring to the results in Table 1, in Comparative Example 1, no silicon-containing compound was added to the electrolyte, and the non-Faraday capacity value was lower than the range of the present application. In Comparative Example 2, an excess silicon-containing compound was added to the electrolyte, and the non-Faraday capacity value was higher than the range of the present application. This indicates that the kinetic performance of the battery is superior to that of the Comparative Example when the silicon-containing compound within the range of the present application is added to the electrolyte and the non-Faraday capacity value is within the range of the present application.

[0098] The cycle performance of the batteries in the Examples was significantly improved compared to the Comparative Examples. In Comparative Example 1, no silicon-containing compound was added to the electrolyte, and the non-Faraday capacity value was lower than the range of the present application. In Comparative Example 2, an excess silicon-containing compound was added to the electrolyte, and the non-Faraday capacity value was higher than the range of the present application. This shows that when the silicon-containing compound in the Examples is added to the electrolyte within the range of the present application and the non-Faraday capacity value is within the range of the present application, the batteries have excellent cycle performance compared to the Comparative Examples.

[0099] The present application provides a secondary battery, which can be charged at a high rate and has a high capacity and excellent cycle performance.

[0100] The secondary battery and the electricity-using device provided by the present application have been described in detail above. Although the present application has used specific examples to describe the principles and embodiments of the present application, the description of the above examples is merely intended to facilitate understanding of the method and core idea of ​​the present application. Furthermore, it should be understood that those skilled in the art may make modifications to the specific embodiments and application scope in light of the idea of ​​the present application, and therefore the description in the present application is not intended to limit the present application.

Claims

1. a positive electrode sheet, a negative electrode sheet, a separator, and an electrolyte solution, wherein the non-Faraday capacitance value of the negative electrode sheet is Cdl mF and satisfies 1≦Cdl≦5; and the electrolyte solution contains an additive, which contains a silicon-containing compound; Secondary battery.

2. the silicon-containing compound includes at least one of tris(trimethylsilyl)phosphate, tris(trimethylsilane)phosphite, trimethylfluorosilane, or tris(trimethylsilane)borate; The secondary battery according to claim 1 .

3. Based on the total mass of the electrolyte solution, the mass percentage of the silicon-containing compound is A%, and satisfies 0.01≦A≦5. The secondary battery according to claim 1 or 2.

4. Based on the total mass of the electrolyte solution, the mass percentage of the silicon-containing compound is A%, and satisfies 0.01≦10×Cdl×A%≦2.

5. The secondary battery according to claim 1 or 2.

5. The compressed density of the negative electrode sheet is PD g / cm ３ and 1.1≦PD≦1.7 is satisfied. The secondary battery according to claim 1 or 2.

6. The OI value of the negative electrode sheet is 2 to 25. The secondary battery according to claim 1 or 2.

7. The electrolyte has a surface tension of F mN / m at room temperature, satisfying 20≦F≦40, and the room temperature is 20° C. to 25° C. The secondary battery according to claim 1 or 2.

8. The internal resistance of the secondary battery is R mΩ, and satisfies 0.02≦R≦0.

8. The secondary battery according to claim 1 or 2.

9. the electrolyte has a surface tension of F mN / m at room temperature, the internal resistance of the secondary battery is R mΩ, and 1.1≦Cdl+R×F / 10≦8 is satisfied; The secondary battery according to claim 1 or 2.

10. The negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer disposed on the negative electrode current collector, the negative electrode active material layer including a negative electrode active material, the negative electrode active material including one or more of artificial graphite, natural graphite, amorphous carbon, carbon nanotubes, and mesocarbon microspheres. The secondary battery according to claim 1 or 2.

11. The secondary battery according to claim 1 or 2, Electrical usage devices.

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