Battery

Abstract

The present disclosure relates to the field of batteries, and in particular to a battery. The battery comprises a separator and an electrolyte; the separator comprises a substrate layer and a ceramic layer containing inorganic particles and provided on at least one side surface of the substrate layer; the inorganic particles comprise an element Al; on the basis of the total weight of the separator, the content a of the element Al is 12%-32%; the electrolyte comprises ethyl butyrate; and on the basis of the total weight of the electrolyte, the content c1 of the ethyl butyrate is 5%-35%; and 0.2≤c1 / a≤2.5. The battery of the present disclosure can improve the self-discharge characteristic, and has good thermal stability and mechanical properties.

Description

Battery Technical Field

[0001] This disclosure relates to the field of battery technology, specifically to a battery. Background Technology

[0002] Compared to other energy storage devices, lithium-ion batteries offer advantages such as high energy density, high conversion efficiency, long cycle life, and no memory effect, leading to their widespread application in portable electronic devices, electric vehicles, and large-scale energy storage. With the advancement of science and technology and increasing demands for green environmental protection, lithium-ion batteries are expected to play a more significant role in even more fields in the future.

[0003] To further improve battery energy density and meet the public's demand for battery range, increasing battery voltage and reducing separator thickness are the main strategies currently used. However, reducing separator thickness or increasing battery voltage (e.g., above 4.45V) will exacerbate battery self-discharge and affect battery thermal stability and mechanical properties. Summary of the Invention

[0004] The purpose of this disclosure is to overcome the aforementioned problems in the prior art and to provide a battery. The battery of this disclosure has a separator that is compatible with the electrolyte, and the content of ethyl butyrate in the electrolyte and the content of elemental Al in the ceramic layer of the separator satisfy a specific relationship. This allows the battery of this disclosure to improve self-discharge under high voltage conditions and to have superior thermal stability and mechanical properties.

[0005] In related technologies, batteries operating at high voltages (e.g., greater than 4.45V) experience accelerated self-discharge and severely impact their thermal stability and mechanical performance. Research has found the causes to be: First, compared to low-voltage conditions, batteries generate more heat during cycling at high voltages. Especially when the separator thickness is reduced, the separator's thermal and structural stability deteriorates. The excessive heat further exacerbates the separator's swelling and contraction, leading to deformation and thus accelerating self-discharge, further affecting the battery's thermal stability and mechanical performance. Second, under high voltage conditions, metal ions are more easily dissolved from the positive electrode. These dissolved metal ions not only undergo side reactions with the electrolyte, further deteriorating battery stability, but also migrate through the separator to the negative electrode, where they are reduced to metal on the surface. As the metal accumulates, it may puncture the separator, exacerbating self-discharge. Based on these reasons, the inventors of this disclosure have discovered that these problems can be solved by strengthening the separator and improving the electrolyte.

[0006] To enhance the strength of the separator, including Al in the ceramic layer significantly increases its hardness and mechanical strength, thus mitigating deformation issues. Regarding electrolyte improvements, firstly, ethyl butyrate itself possesses high oxidation resistance and thermal stability. Adding it to the electrolyte reduces molecular thermal motion, alleviating the reactivity between the separator and the electrolyte, and improving the overall thermal stability of the battery. Secondly, ethyl butyrate has a strong adsorption effect on metal ions dissolved from the positive electrode, not only mitigating the adverse effects of these ions on the battery but also adsorbing onto the positive electrode surface through electrostatic adsorption. This improves the wettability of the electrolyte on the positive electrode and acts as a barrier between the positive electrode and other electrolyte components, effectively reducing the risk of side reactions between other electrolyte components and the positive electrode, thereby enhancing the battery's thermal stability. Finally, ethyl butyrate can inhibit the dissolution, deformation, and aging decomposition of the diaphragm, thereby inhibiting the swelling and shrinkage of the diaphragm. This allows the diaphragm to maintain good thermal and structural stability even with reduced thickness, preventing thermal runaway.

[0007] However, simply combining a separator containing elemental Al and an electrolyte containing ethyl butyrate does not significantly improve the battery's self-discharge, thermal stability, and mechanical properties under high voltage conditions. The inventors of this disclosure conducted extensive research and discovered that when the content of elemental Al in the ceramic layer of the separator and the content of ethyl butyrate in the electrolyte satisfy a specific relationship, the problems of increased self-discharge and deteriorated thermal stability and mechanical properties under high voltage conditions can be significantly improved. Based on this, the following solution is proposed:

[0008] This disclosure provides a battery comprising a separator and an electrolyte; the separator comprises a substrate layer and a ceramic layer on at least one surface of the substrate layer, the ceramic layer comprising inorganic particles, the inorganic particles comprising element Al, and the content of element Al is a based on the total weight of the separator, wherein 12% ≤ a ≤ 32%; the electrolyte comprises ethyl butyrate, and the content of ethyl butyrate is c1 based on the total weight of the electrolyte, wherein 5% ≤ c1 ≤ 35%; a and c1 satisfy 0.2 ≤ c1 / a ≤ 2.5.

[0009] When a and c1 satisfy a specific relationship, the problems of increased self-discharge and deterioration of thermal stability and mechanical properties can be significantly improved. This may be because the carbonyl group in ethyl butyrate can complex with the Al element in the separator, allowing ethyl butyrate to adsorb onto the separator surface. This isolates the polymer in the separator from dissolution by the low-temperature solvent in the electrolyte and the ceramic layer from corrosion by acidic substances, further improving the structural and thermal stability of the separator. However, excessive Al will occupy ethyl butyrate, preventing it from effectively adsorbing metal ions dissolved from the positive electrode. This leads to the reduction and deposition of metal ions at the negative electrode, exacerbating self-discharge. Therefore, it is necessary to control the Al content in the separator and the ethyl butyrate content in the electrolyte to achieve a specific relationship. Under this relationship, ethyl butyrate can not only effectively adsorb metal ions dissolved from the positive electrode but also form effective interfacial protection on the separator surface.

[0010] The present disclosure has at least the following advantages compared with the prior art through the above technical solution: the battery of the present disclosure can significantly improve the problems of increased self-discharge under high voltage conditions and deterioration of thermal stability and mechanical properties.

[0011] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein. Attached Figure Description

[0012] Figure 1 shows a cross-sectional schematic diagram of the diaphragm in an example of this disclosure.

[0013] Figure 2 shows a cross-sectional schematic diagram of the diaphragm in an example of this disclosure.

[0014] Figure 3 shows the particle size distribution of the positive electrode active material in an example of this disclosure.

[0015] Figure 4 shows a schematic diagram of a battery cell in an example of this disclosure. Detailed Implementation

[0016] The following provides a detailed description of specific embodiments of this disclosure. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit this disclosure.

[0017] This disclosure provides a battery that may include a separator and an electrolyte. The separator may include a substrate layer and a ceramic layer on at least one surface of the substrate layer. Figure 1 shows a cross-sectional schematic diagram of the separator in an embodiment of this disclosure. Figure 1(a) shows the case where the ceramic layer is disposed on one side, and Figure 1(b) shows the case where the ceramic layer is disposed on both sides. In Figure 1(a), the separator 1 includes a substrate layer 11 and a ceramic layer 12 on one surface of the substrate layer 11; in Figure 1(b), the separator 1 includes a substrate layer 11 and ceramic layers 12 on both surfaces of the substrate layer 11.

[0018] In this disclosure, the ceramic layer may include inorganic particles. The inorganic particles may include element Al, and the content of element Al, denoted as 'a', is 12% ≤ a ≤ 32% based on the total weight of the membrane. For example, 'a' can be 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, or 32%.

[0019] In one instance, 18% ≤ a ≤ 28%.

[0020] Under the premise that the content of elemental Al in the separator and the content of ethyl butyrate in the electrolyte meet a specific relationship, if the weight content of elemental Al in the separator is too low (e.g., less than 12%), it will lead to a decrease in the overall strength and durability of the separator, thereby affecting the thermal stability and mechanical properties of the battery; while if the weight content of elemental Al in the separator is too high (e.g., greater than 32%), it will affect the lithium ion transport efficiency, thereby affecting the overall charge and discharge efficiency of the battery.

[0021] In this disclosure, the weight content of element Al in the membrane can be determined by methods conventional in the art, such as inductively coupled plasma mass spectrometry (ICP-MS), energy dispersive spectroscopy (EDS), or X-ray fluorescence spectrometry (XRF).

[0022] In this disclosure, the electrolyte may include ethyl butyrate (EB), and the content of ethyl butyrate is c1, based on the total weight of the electrolyte, where 5% ≤ c1 ≤ 35%, for example, 5%, 10%, 15%, 20%, 25%, 30%, or 35%.

[0023] In one instance, 10% ≤ c1 ≤ 30%.

[0024] Under the premise that the content of elemental Al in the separator and the content of ethyl butyrate in the electrolyte meet a specific relationship, if the content of ethyl butyrate in the electrolyte is too low (e.g., less than 5%), it will lead to an increase in the overall viscosity of the electrolyte, which is not conducive to the wetting of the electrolyte and thus affects the cycle stability of the battery. On the other hand, if the content of ethyl butyrate in the electrolyte is too high (e.g., greater than 35%), it will lead to a decrease in the overall boiling point of the electrolyte, which will result in a decrease in the high-temperature stability of the electrolyte and thus affect the high-temperature storage performance of the battery.

[0025] In this disclosure, the weight content of ethyl butyrate in the electrolyte can be obtained by methods conventional in the art, such as gas chromatography, infrared spectroscopy, or liquid chromatography.

[0026] In this disclosure, a and c1 satisfy 0.2≤c1 / a≤2.5, for example, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2, 2.1, 2.2, 2.3, 2.4 or 2.5.

[0027] In one instance, 0.35 ≤ c1 / a ≤ 1.7.

[0028] In one instance, 0.5 ≤ c1 / a ≤ 1.2.

[0029] In related technologies, batteries operating at high voltages (e.g., greater than 4.45V) experience further exacerbated self-discharge problems when the separator thickness is reduced. The battery disclosed herein, however, improves self-discharge performance even with a thinner separator (e.g., 4μm-16μm).

[0030] In this disclosure, the thickness of the diaphragm is b, 4μm≤b≤16μm, for example, 4μm, 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, 11μm, 12μm, 13μm, 14μm, 15μm or 16μm.

[0031] When the separator is too thin (e.g., less than 4μm), it is prone to breakage, leading to short circuits and thus posing a safety risk; when the separator is too thick (e.g., greater than 16μm), it reduces the overall volumetric energy density of the battery, which is not in line with the development trend of batteries.

[0032] In this disclosure, the substrate layer may include at least one of polyethylene (PE) and polypropylene (PP). The thickness of the substrate layer may be 3μm-14μm, for example, 3μm, 4μm, 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, 11μm, 12μm, 13μm or 14μm.

[0033] In one example, the thickness of the substrate layer is 5 μm-10 μm.

[0034] In this disclosure, the inorganic particles may include aluminum-containing inorganic particles. The aluminum-containing inorganic particles may include at least one of alumina, aluminum hydroxide, montmorillonite, and boehmite. The inorganic particles may also include at least one of silicon oxide, magnesium oxide, magnesium hydroxide, and zirconium oxide. The ceramic layer may further include a first binder. The first binder may include at least one of polymethyl methacrylate (PMMA), polyacrylic acid (PAA), polyacrylonitrile (PAN), polyethylene, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP), polypropylene, carboxymethyl cellulose (CMC), and styrene-butadiene rubber (SBR).

[0035] In this disclosure, the content of inorganic particles can be 20%-60% based on the total weight of the diaphragm, for example, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55% or 60%.

[0036] In one example, the content of inorganic particles is 30%-45% based on the total weight of the diaphragm.

[0037] In this disclosure, the content of the inorganic particles can be 50%-99% based on the total weight of the ceramic layer, for example, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95% or 99%.

[0038] In one example, the content of inorganic particles is 90%-96% based on the total weight of the ceramic layer.

[0039] In this disclosure, the thickness of the ceramic layer can be 0.2μm-2.5μm, for example, 0.2μm, 0.5μm, 1μm, 1.5μm, 2μm or 2.5μm.

[0040] In one example, the thickness of the ceramic layer is 0.5 μm to 1.5 μm.

[0041] In this disclosure, the diaphragm may further include an adhesive layer, which may be located on at least one outer surface of the diaphragm. Figure 2 shows a cross-sectional schematic diagram of the diaphragm in an example of this disclosure, wherein Figures 2(a) and 2(b) show the case where the adhesive layer is disposed on one side, and Figures 2(c) and 2(d) show the case where the adhesive layer is disposed on both sides. In Figure 2(a), the diaphragm 1 includes a substrate layer 11, a ceramic layer 12 on one side of the substrate layer 11, and an adhesive layer 13 on the outer surface of the ceramic layer 12; in Figure 2(b), the diaphragm 1 includes a substrate layer 11, ceramic layers 12 on both sides of the substrate layer 11, and an adhesive layer 13 on the outer surface of one side of the diaphragm 1; in Figure 2(c), the diaphragm 1 includes a substrate layer 11, a ceramic layer 12 on one side of the substrate layer 11, and an adhesive layer 13 on the outer surfaces of both sides of the diaphragm 1; in Figure 2(d), the diaphragm 1 includes a substrate layer 11, ceramic layers 12 on both sides of the substrate layer 11, and an adhesive layer 13 on the outer surfaces of both sides of the diaphragm 1.

[0042] In this disclosure, the adhesive layer may include a second adhesive. The second adhesive may include at least one selected from polyvinylidene fluoride, PMMA, PAA, PAN, PVDF-HFP, polyethylene oxide (PEO), and polyimide (PI). The thickness of the adhesive layer may be 0.5 μm to 5 μm, for example, 0.5 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, or 5 μm.

[0043] In one example, the thickness of the adhesive layer is 1 μm-3 μm.

[0044] In this disclosure, the battery may further include a positive electrode sheet. The positive electrode sheet may include a positive electrode active material, which may include first particles and second particles. The median particle size Dv of the first particles... 1 50 is less than the median particle size Dv of the second particle 2 50. Figure 3 shows the particle size distribution of the positive electrode active material in an example of this disclosure. As can be seen from the figure, the positive electrode active material includes a first particle and a second particle, and the median particle size of the first particle is smaller than the median particle size of the second particle.

[0045] The inventors of this disclosure have discovered that when the median particle size of the first particle in the positive electrode active material is smaller than the median particle size of the second particle, the particles of the positive electrode active material are more tightly bound together, which is conducive to the uniform distribution of particles of different sizes in the positive electrode active material layer. This prevents the positive electrode sheet structure from becoming less stable due to powder shedding, stabilizes the battery capacity, further reduces the battery's self-discharge, and reduces safety hazards.

[0046] In one example, the positive electrode active material includes lithium cobalt oxide.

[0047] In this disclosure, 3μm≤Dv 1 50 ≤ 15 μm, for example, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm or 15 μm.

[0048] In one instance, 3μm≤Dv 1 50≤6μm.

[0049] In one instance, 4μm≤Dv 1 50≤5μm.

[0050] In this disclosure, 4μm≤Dv 2 50 ≤ 18 μm, for example, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm or 18 μm.

[0051] In one instance, 13μm≤Dv 2 50≤18μm.

[0052] In one instance, 14μm≤Dv 2 50≤16μm.

[0053] In this disclosure, the median particle size of the first particle and the median particle size of the second particle can be obtained by methods conventional in the art, such as a Malvern laser particle size analyzer.

[0054] In this disclosure, the particle size of the positive electrode active material can be: 2μm≤Dv10≤10μm (e.g., 2μm, 3μm, 4μm, 5μm, 6μm, 7μm, 8μm, 9μm or 10μm), 8μm≤Dv50≤20μm (e.g., 8μm, 9μm, 10μm, 11μm, 12μm, 13μm, 14μm, 15μm, 16μm, 17μm, 18μm, 19μm or 20μm). ), 20μm≤Dv90≤40μm (e.g., 20μm, 21μm, 22μm, 23μm, 24μm, 25μm, 26μm, 27μm, 28μm, 29μm, 30μm, 35μm or 40μm), Dv99≤52μm (e.g., 52μm, 50μm, 45μm, 42μm, 41μm, 40μm, 39μm, 38μm, 37μm, 36μm or 35μm).

[0055] The inventors of this disclosure have discovered that when the particle size of the positive electrode active material is within a specific range, it is beneficial for the tight bonding between the positive electrode active material particles, so that particles of different sizes are evenly distributed in the positive electrode active material layer, thereby preventing the positive electrode active material from falling off during battery charge and discharge cycles and preventing local lithium plating caused by uneven lithium ion transport.

[0056] In this disclosure, the particle sizes Dv10, Dv50, Dv90, and Dv99 of the positive electrode active material have conventional meanings in the art. Dv10 refers to the particle size corresponding to a cumulative particle size distribution percentage of 10% for the sample. Dv50 refers to the particle size corresponding to a cumulative particle size distribution percentage of 50% for the sample. Dv90 refers to the particle size corresponding to a cumulative particle size distribution percentage of 90% for the sample. Dv99 refers to the particle size corresponding to a cumulative particle size distribution percentage of 99% for the sample. Dv10, Dv50, Dv90, and Dv99 can be obtained by conventional methods in the art, such as a Malvern laser particle size analyzer, as follows: After discharging the battery to 0% SOC, the positive electrode sheet is disassembled and removed. It is then soaked in dimethyl carbonate (DMC) solvent for 12 hours, followed by rinsing with DMC to remove lithium salts adhering to the positive electrode sheet. The positive electrode sheet is then kept at 450°C for 180 minutes. The cooled positive electrode sheet is brushed off with a brush to obtain positive electrode active material powder. The collected positive electrode active material powder is taken as a sample and tested using a Malvern laser particle size analyzer.

[0057] In this disclosure, the positive electrode active material may include the chemical formula Li a Co z M 1 x M 2 y The substance of O2, wherein 0.9 ≤ a ≤ 1.1 (e.g., 0.9, 0.91, 0.92, 0.93, 0.94, 0.95, 0.96, 0.97, 0.98, 0.99, 1, 1.01, 1.02, 1.03, 1.04, 1.05, 1.06, 1.07, 1.08, 1.09 or 1.1), and 0.01 ≤ x ≤ 0.1 (e.g., 0.01, 0.02, 0.03, 0.04, 0. 0.05, 0.06, 0.07, 0.08, 0.09, or 0.1), 0 ≤ y ≤ 0.05 (e.g., 0, 0.01, 0.02, 0.03, 0.04, or 0.05), 0.85 ≤ z ≤ 0.99 (e.g., 0.85, 0.86, 0.87, 0.88, 0.89, 0.9, 0.91, 0.92, 0.93, 0.94, 0.95, 0.96, 0.97, 0.98, or 0.99), M 1 It may include at least one of Mn, Al and Mg, M 2It may include at least one of Zr, Ni, Y, Sr, W, Sc, B, Si, Ti, Sn, Tb, Nb, Sb, Se, C, La, Ta, and Te.

[0058] In this disclosure, the values ​​of a, x, y and z can be measured by conventional methods in the art, for example by the following method: take the aforementioned positive electrode active material powder as a sample, analyze it with an ICP spectrometer, and after obtaining the corresponding test parameters, a, x, y and z can be obtained by formula conversion.

[0059] The inventors of this disclosure have discovered that specific positive electrode active materials can improve the cycle stability of batteries under high voltage conditions.

[0060] In this disclosure, the positive electrode sheet may include a positive current collector and a positive active material layer on at least one side surface of the positive current collector. The positive active material layer may include the positive active material. The positive active material layer may also include at least one of a positive conductive agent and a positive binder. The positive conductive agent may include at least one conductive agent conventionally used in the art, such as conductive carbon black, carbon nanotubes, and carbon fibers. The positive binder may include at least one binder conventionally used in the art, such as polyvinylidene fluoride, polymethyl methacrylate, polytetrafluoroethylene, polyacrylic acid, carboxymethyl cellulose, sodium carboxymethyl cellulose, lithium carboxymethyl cellulose, and styrene-butadiene rubber.

[0061] In this disclosure, based on the total weight of the positive electrode active material layer, the content of the positive electrode active material can be 80%-99.8% (e.g., 80%, 82%, 84%, 86%, 88%, 90%, 92%, 94%, 96%, 98%, 99%, or 99.8%), the content of the positive electrode conductive agent can be 0.1%-10% (e.g., 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1%, 0.5%, or 0.1%), and the content of the positive electrode binder can be 0.1%-10% (e.g., 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1%, 0.5%, or 0.1%).

[0062] In this disclosure, the battery may further include a negative electrode. The negative electrode may include silicon-based particles with a median particle size Dv50 of d. The electrolyte may further include nitrile additives and fluorinated cyclic carbonate additives, wherein the content of the nitrile additives is c2 and the content of the fluorinated cyclic carbonate additives is c3, based on the total weight of the electrolyte. c1, c2, c3 and d (in μm) satisfy 1 ≤ (0.01 × d + c1) / (c2 + c3) ≤ 8, for example, 1, 2, 3, 4, 5, 6, 7 or 8.

[0063] When c1, c2, c3, and d satisfy a specific relationship, the thermal stability of the battery can be further improved and self-discharge reduced. This may be because nitrile additives can complex metal ions dissolved from the positive electrode, improving its stability. They also have a synergistic effect with ethyl butyrate, further preventing the adverse effects of metal ions dissolved from the positive electrode on the battery. However, nitrile additives themselves have low reducing power and can corrode the negative electrode containing silicon-based materials. Fluorinated cyclic carbonate additives can form a robust and corrosion-resistant SEI film on the surface of the negative electrode containing silicon-based materials. This not only inhibits the volume expansion of the silicon-based material but also reduces the corrosive effect of nitrile additives on the negative electrode, thereby improving the structural stability of the negative electrode. Ethyl butyrate has high thermal stability, preventing the electrolyte from dissolving and absorbing the SEI film during battery charge-discharge cycles. Ethyl butyrate and fluorocyclic carbonate additives have a synergistic effect, further improving the stability of the SEI film in the electrolyte. However, simply adding nitrile additives and fluorinated cyclic carbonate additives to the additives cannot significantly improve the dissolution of positive electrode metal ions and prevent SEI film decomposition. The inventors of this disclosure have discovered that when c1, c2, c3 and d satisfy a specific relationship, not only can the dissolution of metal ions be further suppressed, thereby reducing the self-discharge of the battery; it can also improve the stability of the SEI film, thereby improving the thermal stability and cycle stability of the battery; and at the same time, it can improve the mechanical strength and thermal stability of the separator.

[0064] In one instance, 1.2 ≤ (0.01 × d + c1) / (c2 + c3) ≤ 3.7.

[0065] In one instance, 1.5 ≤ (0.01 × d + c1) / (c2 + c3) ≤ 3.

[0066] In this disclosure, 5μm≤d≤20μm, for example, 5μm, 10μm, 15μm or 20μm.

[0067] In one instance, 10μm≤d≤18μm.

[0068] In this disclosure, the median particle size Dv50 of the silicon-based particles can be obtained by methods conventional in the art, such as a Malvern laser particle size analyzer or a scanning electron microscope.

[0069] In this disclosure, c2 ≥ 0, for example, 0, 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5%, or 6%.

[0070] In one instance, 2% ≤ c2 ≤ 6%.

[0071] In one instance, 4% ≤ c2 ≤ 5%.

[0072] In this disclosure, c3 ≥ 0, for example, 0, 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, or 15%.

[0073] In one instance, 5% ≤ c3 ≤ 15%.

[0074] In one instance, 8% ≤ c3 ≤ 12%.

[0075] In this disclosure, the weight content of the nitrile additives and the weight content of the fluorinated cyclic carbonate additives in the electrolyte can be obtained by methods conventional in the art, such as gas chromatography, infrared spectroscopy, or liquid chromatography.

[0076] In this disclosure, the nitrile additives may include at least one selected from ethylene glycol bis(propionitrile) ether, adiponitrile, succinic anionitrile, 1,3,6-hexanetrionitrile, glutaronitrile, trans-butenedionitrile, trans-hexenedionitrile, 1,2-bis(2-cyanoethoxy)ethane, 1,2,3-tris(2-cyanoethoxy)propane, and 1,2,3,4,5,6-(2-cyanoethoxy)hexane. The fluorocyclic carbonate additives may include at least one selected from fluoroethylene carbonate and difluoroethylene carbonate.

[0077] In one example, the nitrile additives include butadionitrile and 1,3,6-hexanetrionitrile.

[0078] In one example, the weight ratio of the succinic anion to the 1,3,6-hexanetrionitrile is 1:(1-2), for example, 1:1, 1:1.5 or 1:2.

[0079] In one example, the fluorocyclic carbonate additive includes fluoroethylene carbonate.

[0080] In this disclosure, the silicon-based particles may include at least one of elemental silicon, silicon-oxygen, silicon-carbon, and silicon alloys. Silicon-oxygen refers to materials comprising elements Si and O. Silicon-carbon refers to materials comprising elements Si and C.

[0081] In one example, the silicon-carbon comprises silicon-carbon particles formed by combining nano-silicon with carbon materials.

[0082] In this disclosure, the negative electrode sheet may include a negative electrode current collector and a negative electrode active material layer on at least one side surface of the negative electrode current collector. The negative electrode active material layer may include a negative electrode active material. The negative electrode active material may include the silicon-based particles. The negative electrode active material may also include carbon-based particles. The carbon-based particles may include at least one of natural graphite, artificial graphite, mesophase carbon microspheres, soft carbon, and hard carbon.

[0083] In this disclosure, based on the total weight of the negative electrode active material, the content of the silicon-based particles can be 1%-50% (e.g., 1%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, or 50%), and the content of the carbon-based particles can be 50%-99% (e.g., 99%, 95%, 90%, 85%, 80%, 75%, 70%, 65%, 60%, 55%, or 50%).

[0084] In one example, based on the total weight of the negative electrode active material, the content of silicon-based particles is 3%-10%, and the content of carbon-based particles can be 90%-97%.

[0085] In this disclosure, the negative electrode active material layer may further include at least one of a negative electrode conductive agent and a negative electrode binder. The negative electrode conductive agent may include at least one conductive agent conventionally used in the art, such as conductive carbon black, carbon nanotubes, and carbon fibers. The negative electrode binder may include at least one binder conventionally used in the art, such as polyvinylidene fluoride, polymethyl methacrylate, polytetrafluoroethylene, polyacrylic acid, carboxymethyl cellulose, sodium carboxymethyl cellulose, lithium carboxymethyl cellulose, and styrene-butadiene rubber.

[0086] In this disclosure, based on the total weight of the negative electrode active material layer, the content of the negative electrode active material can be 80%-99.8% (e.g., 80%, 82%, 84%, 86%, 88%, 90%, 92%, 94%, 96%, 98%, 99%, or 99.8%), the content of the negative electrode conductive agent can be 0.1%-10% (e.g., 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1%, 0.5%, or 0.1%), and the content of the negative electrode binder can be 0.1%-10% (e.g., 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1%, 0.5%, or 0.1%).

[0087] Unsaturated silane additives not only exhibit good compatibility with silicon-based particles but also synergistically enhance the toughness and strength of the SEI film with ethyl butyrate. This is because the unsaturated bonds in the unsaturated silane additives can participate in the formation of the SEI film, while ethyl butyrate has a certain inhibitory effect on the excessive growth of the SEI film. When ethyl butyrate is included in the electrolyte, the SEI film formed by the unsaturated silane additives has better strength and toughness in this environment, further improving the protection of the negative electrode and mitigating the volume expansion of silicon-based particles during battery charge-discharge cycles.

[0088] In this disclosure, the electrolyte may further include unsaturated silane additives. The unsaturated silane additives may include at least one of tetravinylsilane, trivinylmethylsilane, hexavinyldisiloxane, and vinyl-2-methoxyethoxysilane.

[0089] In one instance, the unsaturated silane additive comprises hexavinyldisiloxane.

[0090] In this disclosure, the content of the unsaturated silane additive is c4, c4≥0, for example, 0, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7% or 0.8%, based on the total weight of the electrolyte.

[0091] In one instance, 0.05% ≤ c4 ≤ 1%.

[0092] In one instance, 0.2% ≤ c4 ≤ 0.5%.

[0093] In this disclosure, the weight content of the unsaturated silane additive in the electrolyte can be obtained by methods conventional in the art, such as gas chromatography, infrared spectroscopy, or liquid chromatography.

[0094] The inventors of this disclosure have discovered that when the content of unsaturated silane additives in the electrolyte is within a specific range, their synergistic effect with ethyl butyrate is more pronounced, which can further enhance the toughness and strength of the SEI film, thereby improving the protection effect on the negative electrode and reducing the volume expansion of silicon-based particles during battery charge-discharge cycles.

[0095] In this disclosure, the electrolyte may further comprise an organic solvent and a lithium salt. The organic solvent may include organic solvents conventionally used in the art, such as at least one selected from ethylene carbonate, methyl ethyl carbonate, propylene carbonate, diethyl carbonate, ethyl propionate, propyl propionate, ethyl acetate, and γ-butyrolactone. The lithium salt may include lithium salts conventionally used in the art, such as at least one selected from lithium hexafluorophosphate (LiPF6), lithium difluorophosphate, lithium difluorobis(oxalate) phosphate, lithium tetrafluoro(oxalate) phosphate, lithium oxalate phosphate, lithium bis(oxalate) borate, lithium difluoro(oxalate) borate, lithium tetrafluoroborate, lithium bis(trifluorosulfonyl)imide, and lithium bis(fluorosulfonyl)imide.

[0096] In this disclosure, the positive electrode, the separator, and the negative electrode are stacked. The ceramic layer faces the positive electrode. Figure 4 shows a schematic diagram of a battery cell in an example of this disclosure. As can be seen from the figure, the battery cell includes a separator 1, a negative electrode 2, and a positive electrode 3. The separator 1 includes a binder layer 13, a ceramic layer 12, a substrate layer 11, and the binder layer 13 arranged sequentially. The ceramic layer 12 of the separator faces the positive electrode 3.

[0097] The inventors of this disclosure have discovered that when the ceramic layer faces the positive electrode, it is beneficial to improve the electrolyte absorption and moisture retention capacity of the positive electrode side, and to improve the adsorption effect of ethyl butyrate on metal ions dissolved from the positive electrode. This not only further improves the battery's self-discharge, thermal stability, and mechanical properties, but also increases the peeling force between the separator and the positive electrode, promotes the formation of an integrated structure of the cell, and improves the overall stability of the battery.

[0098] In this disclosure, the peel force between the separator and the negative electrode sheet can be 6N / m-30N / m, for example, 6N / m, 7N / m, 8N / m, 9N / m, 10N / m, 11N / m, 12N / m, 13N / m, 14N / m, 15N / m, 16N / m, 17N / m, 18N / m, 19N / m, 20N / m, 21N / m, 22N / m, 23N / m, 24N / m, 25N / m, 26N / m, 27N / m, 28N / m, 29N / m or 30N / m.

[0099] In one example, the peel force between the separator and the negative electrode is 18 N / m-22 N / m.

[0100] In this disclosure, the peel force between the separator and the positive electrode sheet can be 3N / m-20N / m, for example, 3N / m, 4N / m, 5N / m, 6N / m, 7N / m, 8N / m, 9N / m, 10N / m, 11N / m, 12N / m, 13N / m, 14N / m, 15N / m, 16N / m, 17N / m, 18N / m, 19N / m or 20N / m.

[0101] In one example, the peel force between the separator and the positive electrode is 8 N / m-10 N / m.

[0102] The inventors of this disclosure have discovered that when the peel force between the separator and the positive electrode and / or the peel force between the separator and the negative electrode is within a specific range, the overall structural stability of the battery can be improved, thereby reducing the occurrence of self-discharge.

[0103] In this disclosure, the peel force between the separator and the negative electrode and the peel force between the separator and the positive electrode can be tested by conventional methods in the art, such as a universal tensile testing machine.

[0104] In this disclosure, the charging cut-off voltage of the battery is ≥4.45V.

[0105] In one example, the charging cutoff voltage of the battery is 4.45V-4.58V.

[0106] In one example, the battery is a lithium-ion rechargeable battery.

[0107] In one example, the battery is a wound battery.

[0108] It should be noted that the numerical designations such as "first" and "second" in this disclosure are only used to distinguish different substances or methods of use, and do not represent a difference in order.

[0109] The present disclosure will be described in detail below through embodiments. The embodiments described in this disclosure are only some embodiments of this disclosure, and not all embodiments. Based on the embodiments in this disclosure, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this disclosure.

[0110] In the following examples, unless otherwise specified, all materials used are commercially available analytical grade.

[0111] The following examples illustrate the battery of this disclosure.

[0112] Example 1

[0113] The battery is prepared according to the following method:

[0114] (1) Preparation of the diaphragm

[0115] Polyvinylidene fluoride (PVDF) and boehmite were mixed evenly at a weight ratio of 5:95. N-methylpyrrolidone (NMP) was added to obtain a ceramic layer slurry. This ceramic layer slurry was coated onto one side of a polyethylene membrane (6 μm thick). PVDF was added to NMP to obtain an adhesive layer slurry. This adhesive layer slurry was coated onto the outer surfaces of the polyethylene membrane and the ceramic layer (i.e., the adhesive layer was located on both outer surfaces of the membrane). After drying, a membrane was obtained, wherein the thickness of the ceramic layer was 1 μm, the thickness of the adhesive layer was 2 μm, a was 23%, b was 11 μm, and the weight content of boehmite in the membrane was 35%.

[0116] (2) Preparation of positive electrode sheet

[0117] LiCo 0.95 Al 0.05 O2 (including the first and second particles, where Dv) 1 50 is 4.5μm, Dv 2 50 (15μm), polyvinylidene fluoride and conductive carbon black (Super P) are mixed evenly in a weight ratio of 97:2:3, NMP is added, and the mixture is continuously stirred under the action of a stirrer to form a uniform positive electrode slurry. The positive electrode slurry is coated on an aluminum foil with a thickness of 10μm and dried in a vacuum oven at 120℃ for 6 hours. After rolling and slitting, the positive electrode sheet is obtained.

[0118] (3) Preparation of negative electrode sheet

[0119] The negative electrode active material (a combination of silicon carbon and artificial graphite, wherein the weight content of silicon carbon is 8%, the weight content of artificial graphite is 92%, and the median particle size d of silicon carbon is 15μm), conductive carbon black (Super P), sodium carboxymethyl cellulose (CMC-Na) and SBR are mixed evenly in a weight ratio of 97.5:1:0.3:1.2. Deionized water is added, and the mixture is continuously stirred under the action of a stirrer to form a uniform negative electrode slurry. The negative electrode slurry is coated onto a copper foil with a thickness of 10μm and dried in a vacuum oven at 120℃ for 6 hours. After rolling and slitting, the negative electrode sheet is obtained.

[0120] (4) Preparation of electrolyte

[0121] In an argon-filled glove box (moisture <1ppm, oxygen <1ppm), ethylene carbonate, propylene carbonate, ethyl propionate, and propyl propionate were mixed in a weight ratio of 20:10:50:20 to form a homogeneous solvent. LiPF6, based on 14.3% of the total electrolyte weight, was slowly added, along with ethyl butyrate (amounts shown in Table 1), nitrile additives (a combination of succinic anionyl and 1,3,6-hexanetrionitrile, wherein the weight ratio of succinic anionyl and 1,3,6-hexanetrionitrile is 1:1) and / or fluorocyclic carbonate additives (fluoroethylene carbonate) and / or unsaturated silane additives (hexavinyldisiloxane), with specific amounts shown in Table 1. After stirring until homogeneous, the electrolyte was obtained.

[0122] (5) Battery fabrication

[0123] The positive electrode sheet prepared in step (2), the separator prepared in step (1), and the negative electrode sheet prepared in step (3) are stacked together, with the ceramic layer of the separator facing the positive electrode sheet. A bare cell is prepared by winding. The bare cell is placed in an aluminum-plastic film package. The electrolyte prepared in step (4) is injected into the dried bare cell. After vacuum sealing, room temperature standing, high temperature formation and other processes, a battery is obtained.

[0124] Example 2

[0125] The battery is prepared according to the following method:

[0126] (1) Preparation of the diaphragm

[0127] Polyvinylidene fluoride (PVDF) and boehmite were mixed uniformly at a weight ratio of 10:90, and NMP was added to obtain a ceramic layer slurry. This ceramic layer slurry was coated onto one side of a polyethylene membrane (5 μm thick). PVDF was added to NMP to obtain an adhesive layer slurry, which was then coated onto the outer surfaces of the polyethylene membrane and the ceramic layer (i.e., the adhesive layer was located on both outer surfaces of the membrane). After drying, a membrane was obtained, wherein the thickness of the ceramic layer was 0.5 μm, the thickness of the adhesive layer was 3 μm, a was 18%, b was 11.5 μm, and the weight content of boehmite in the membrane was 32%.

[0128] (2) Preparation of positive electrode sheet

[0129] LiCo 0.94 Al 0.05 Ti 0.01 O2 (including the first and second particles, where Dv) 1 50 is 4μm, Dv 2 50 (16μm), polyvinylidene fluoride and conductive carbon black (Super P) are mixed evenly in a weight ratio of 97:2:3, NMP is added, and the mixture is continuously stirred under the action of a stirrer to form a uniform positive electrode slurry. The positive electrode slurry is coated on an aluminum foil with a thickness of 10μm and dried in a vacuum oven at 120℃ for 6 hours. After rolling and slitting, the positive electrode sheet is obtained.

[0130] (3) Preparation of negative electrode sheet

[0131] The negative electrode active material (a combination of silicon carbon and artificial graphite, wherein the weight content of silicon carbon is 8%, the weight content of artificial graphite is 92%, and the median particle size d of silicon carbon is 10 μm), conductive carbon black (Super P), sodium carboxymethyl cellulose (CMC-Na) and SBR are mixed evenly in a weight ratio of 97.5:1:0.3:1.2. Deionized water is added, and the mixture is continuously stirred under the action of a stirrer to form a uniform negative electrode slurry. The negative electrode slurry is coated onto a copper foil with a thickness of 10 μm and dried in a vacuum oven at 120℃ for 6 hours. After rolling and slitting, the negative electrode sheet is obtained.

[0132] (4) Preparation of electrolyte

[0133] In an argon-filled glove box (moisture <1ppm, oxygen <1ppm), ethylene carbonate, propylene carbonate, ethyl propionate, and propyl propionate were mixed in a weight ratio of 20:10:50:20 to form a homogeneous solvent. LiPF6, based on 14.3% of the total electrolyte weight, was slowly added, along with ethyl butyrate (amounts shown in Table 1), nitrile additives (a combination of succinate and 1,3,6-hexanetrionitrile, with a weight ratio of succinate and 1,3,6-hexanetrionitrile of 1:1.5) and / or fluorocyclic carbonate additives (fluoroethylene carbonate) and / or unsaturated silane additives (hexavinyldisiloxane), with specific amounts shown in Table 1. After stirring until homogeneous, the electrolyte was obtained.

[0134] (5) Battery fabrication

[0135] The positive electrode sheet prepared in step (2), the separator prepared in step (1), and the negative electrode sheet prepared in step (3) are stacked together, with the ceramic layer of the separator facing the positive electrode sheet. A bare cell is prepared by winding. The bare cell is placed in an aluminum-plastic film package. The electrolyte prepared in step (4) is injected into the dried bare cell. After vacuum sealing, room temperature standing, high temperature formation and other processes, a battery is obtained.

[0136] Example 3

[0137] The battery is prepared according to the following method:

[0138] (1) Preparation of the diaphragm

[0139] PMMA and boehmite were mixed evenly at a weight ratio of 4:96, and NMP was added to obtain a ceramic layer slurry. This ceramic layer slurry was coated on one side of a polyethylene membrane (10 μm thick). Polyvinylidene fluoride was added to NMP to obtain an adhesive layer slurry. This adhesive layer slurry was coated on the outer surfaces of the polyethylene membrane and the ceramic layer (i.e., the adhesive layer was located on both outer surfaces of the membrane). After drying, a membrane was obtained, wherein the thickness of the ceramic layer was 1.5 μm, the thickness of the adhesive layer was 1 μm, a was 28%, b was 13.5 μm, and the weight content of boehmite in the membrane was 43%.

[0140] (2) Preparation of positive electrode sheet

[0141] LiCo 0.94 Al 0.05 Mg 0.01 O2 (including the first and second particles, where Dv) 1 50 is 5μm, Dv 250 (14μm), polyvinylidene fluoride and conductive carbon black (Super P) are mixed evenly in a weight ratio of 97:2:3, NMP is added, and the mixture is continuously stirred under the action of a stirrer to form a uniform positive electrode slurry. The positive electrode slurry is coated on an aluminum foil with a thickness of 10μm and dried in a vacuum oven at 120℃ for 6 hours. After rolling and slitting, the positive electrode sheet is obtained.

[0142] (3) Preparation of negative electrode sheet

[0143] The negative electrode active material (a combination of silicon carbon and artificial graphite, wherein the weight content of silicon carbon is 8%, the weight content of artificial graphite is 92%, and the median particle size d of silicon carbon is 18μm), conductive carbon black (Super P), sodium carboxymethyl cellulose (CMC-Na) and SBR are mixed evenly in a weight ratio of 97.5:1:0.3:1.2. Deionized water is added, and the mixture is continuously stirred under the action of a stirrer to form a uniform negative electrode slurry. The negative electrode slurry is coated onto a copper foil with a thickness of 10μm and dried in a vacuum oven at 120℃ for 6 hours. After rolling and slitting, the negative electrode sheet is obtained.

[0144] (4) Preparation of electrolyte

[0145] In an argon-filled glove box (moisture <1ppm, oxygen <1ppm), ethylene carbonate, propylene carbonate, ethyl propionate, and propyl propionate were mixed in a weight ratio of 20:10:50:20 to form a homogeneous solvent. LiPF6, based on 14.3% of the total electrolyte weight, was slowly added, along with ethyl butyrate (amounts shown in Table 1), nitrile additives (a combination of succinate and 1,3,6-hexanetrionitrile, with a weight ratio of succinate and 1,3,6-hexanetrionitrile of 1:2) and / or fluorocyclic carbonate additives (fluoroethylene carbonate) and / or unsaturated silane additives (hexavinyldisiloxane), with specific amounts shown in Table 1. After stirring until homogeneous, the electrolyte was obtained.

[0146] (5) Battery fabrication

[0147] The positive electrode sheet prepared in step (2), the separator prepared in step (1), and the negative electrode sheet prepared in step (3) are stacked together, with the ceramic layer of the separator facing the positive electrode sheet. A bare cell is prepared by winding. The bare cell is placed in an aluminum-plastic film package. The electrolyte prepared in step (4) is injected into the dried bare cell. After vacuum sealing, room temperature standing, high temperature formation and other processes, a battery is obtained.

[0148] Example 4 group

[0149] This set of examples is used to verify the impact of the change in "c1 / a".

[0150] This set of embodiments is based on embodiment 2 or embodiment 3, except that c1 is changed, as follows:

[0151] Example 4a is carried out with reference to Example 2, except that c1 is adjusted from 10% to 30%;

[0152] Example 4b is carried out with reference to Example 3, except that c1 is adjusted from 30% to 10%.

[0153] Example 5 group

[0154] This set of examples is used to verify the impact of the change in "(0.01×d+c1) / (c2+c3)".

[0155] This set of embodiments is based on embodiment 2 or embodiment 3, except that c3 is changed, as follows:

[0156] Example 5a was carried out with reference to Example 2, except that c3 was adjusted from 8% to 12%;

[0157] Example 5b is carried out with reference to Example 3, except that c3 is adjusted from 12% to 8%.

[0158] Example 6 group

[0159] This set of examples is used to verify the impact of changing "a".

[0160] This set of embodiments is based on Embodiment 1, except that 'a' is changed by adjusting the weight content of inorganic particles in the ceramic layer and / or the thickness of the ceramic layer, as detailed below:

[0161] Example 6a: Polyvinylidene fluoride and boehmite were mixed evenly at a weight ratio of 50:50, wherein a was 12% and the weight content of boehmite in the membrane was 26%.

[0162] Example 6b: Polyvinylidene fluoride and boehmite were mixed uniformly at a weight ratio of 2:98, wherein a was 32%, the thickness of the ceramic layer was 1.5 μm, and b was 11.5 μm.

[0163] In Example 6c, polyvinylidene fluoride and alumina were mixed uniformly at a weight ratio of 5:95, wherein a was 27%.

[0164] Example 7 group

[0165] This set of examples is used to verify the impact of the change in "b".

[0166] This set of embodiments refers to Embodiment 1, except that b is changed by adjusting the thickness of the substrate layer and / or the ceramic layer and / or the adhesive layer, as follows:

[0167] Example 7a has a polyethylene film thickness of 3 μm, a ceramic layer thickness of 0.2 μm, and an adhesive layer thickness of 0.5 μm, while example b has a thickness of 4.2 μm. The boehmite content in the membrane is 44% by weight.

[0168] Example 7b: The thickness of the polyethylene film is 3 μm, the thickness of the ceramic layer is 2.5 μm, the thickness of the adhesive layer is 5 μm, and the thickness of b is 15.5 μm. The boehmite content in the membrane is 60% by weight.

[0169] Example 8 group

[0170] This set of examples is used to verify "Dv" 1 50 and / or Dv 2 The impact of the "50" change.

[0171] This set of embodiments is based on Embodiment 1, except that Dv is changed. 1 50 and / or Dv 2 50, as detailed below:

[0172] Example 8a, Dv 1 50 is 3μm, Dv 2 50 is 13μm;

[0173] Example 8b, Dv 1 50 is 6μm, Dv 2 50 is 18μm;

[0174] Example 8c, Dv 2 50 is 4.5μm, and the median particle size of the first particle is equal to the median particle size of the second particle;

[0175] Example 8d, Dv 1 50 is 15μm, and the median particle size of the first particle is equal to the median particle size of the second particle.

[0176] Example 9 group

[0177] This set of examples is used to verify the impact of changing "d".

[0178] This set of embodiments is based on Embodiment 1, except that d is changed, as follows:

[0179] Example 9a: The median particle size d of silicon-carbon is 5 μm;

[0180] In Example 9b, the median particle size d of silicon-carbon was 8 μm.

[0181] Example 10 group

[0182] This set of examples is used to verify the impact of the change in "c1".

[0183] This set of embodiments is based on Embodiment 1, except that c1 is changed, as detailed in Table 1.

[0184] Example 11 group

[0185] This set of examples is used to verify the impact of the change in "c2".

[0186] This set of embodiments is based on Embodiment 1, except that c2 is changed, as detailed in Table 1.

[0187] Example 12 group

[0188] This set of examples is used to verify the impact of the change in "c3".

[0189] This set of embodiments is based on Embodiment 1, except that c3 is changed, as detailed in Table 1.

[0190] Example 13 group

[0191] This set of examples is used to verify the impact of the change in "c4".

[0192] This set of embodiments is based on Embodiment 1, except that c4 is changed, as detailed in Table 1.

[0193] Example 14

[0194] The procedure was carried out in accordance with Example 1, except that the ceramic layer of the separator was positioned directly opposite the negative electrode.

[0195] Example 15

[0196] The same procedure was followed as in Example 1, except that silicon carbon was replaced with the same weight of silicon oxide.

[0197] Example 16 group

[0198] This set of examples is used to verify the impact of changes in the "weight content of silicon-based particles in the negative electrode active material".

[0199] This set of embodiments is based on Embodiment 1, except that the weight content of silicon-based particles in the negative electrode active material is changed, as follows:

[0200] Example 16a: The weight content of silicon carbon in the negative electrode active material is 3%, and the weight content of artificial graphite is 97%.

[0201] Example 16b: The weight content of silicon carbon in the negative electrode active material is 10%, and the weight content of artificial graphite is 90%.

[0202] Example 16c: The weight content of silicon carbon in the negative electrode active material is 1%, and the weight content of artificial graphite is 99%.

[0203] In Example 16d, the weight content of silicon-carbon in the negative electrode active material was 50%, and the weight content of artificial graphite was 50%.

[0204] Example 17 group

[0205] This set of examples follows the same procedure as Example 1, except that the nitrile additives, fluorocyclic carbonate additives, or unsaturated silane additives are changed, as detailed below:

[0206] Example 17a, in which the nitrile additive was replaced with the same weight of adiponitrile;

[0207] Example 17b, in which the nitrile additive was replaced with the same weight of 1,3,6-hexanetrionitrile;

[0208] Example 17c, in which the fluorocyclic carbonate additive was replaced with the same weight of difluoroethylene carbonate;

[0209] In Example 17d, the unsaturated silane additive was replaced with the same weight of tetravinylsilane.

[0210] Comparative Example 1

[0211] The procedure was carried out in accordance with Example 1, except that ethyl butyrate was replaced with the same weight of methyl butyrate.

[0212] Comparative Example 2

[0213] The same procedure was followed as in Example 1, except that boehmite was replaced with magnesium oxide, resulting in an elemental Mg content of 23%.

[0214] Comparative Example 3

[0215] The process was carried out in accordance with Example 1, except that the content of inorganic particles in the ceramic layer and / or the thickness of the ceramic layer were adjusted as follows: polyvinylidene fluoride and boehmite were mixed evenly in a weight ratio of 50:50, a was 10%, the thickness of the ceramic layer was 0.8 μm, and b was 10.8 μm.

[0216] Comparative Example 4

[0217] The process was carried out in accordance with Example 1, except that the content of inorganic particles in the ceramic layer and / or the thickness of the ceramic layer were adjusted as follows: polyvinylidene fluoride and boehmite were mixed evenly at a weight ratio of 2:98, a was 35%, the thickness of the ceramic layer was 1.8 μm, and b was 11.8 μm.

[0218] Table 1

[0219] Note: The "*" in Table 1 indicates that the value of the embodiment is the same as the embodiment it refers to. For example, if embodiment 4a is carried out with reference to embodiment 2, then the values ​​of c2-c4 in embodiment 4a in Table 1 are the same as those in embodiment 2.

[0220] Test case

[0221] (1) Particle size test of positive electrode active material

[0222] In Examples 1-7 and Examples 9-14, the particle size of the positive electrode active material satisfies the following conditions: 2μm≤Dv10≤10μm, 8μm≤Dv50≤20μm, 20μm≤Dv90≤40μm, and Dv99≤52μm.

[0223] In Examples 8a and 8b, the particle size of the positive electrode active material satisfies: 2μm≤Dv10≤10μm, 8μm≤Dv50≤20μm; but does not satisfy: 20μm≤Dv90≤40μm, Dv99≤52μm.

[0224] In Examples 8c and 8d, the particle size of the positive electrode active material does not meet the following requirements: 2μm≤Dv10≤10μm, 8μm≤Dv50≤20μm, 20μm≤Dv90≤40μm, Dv99≤52μm.

[0225] (2) Loop Test

[0226] The batteries prepared in the examples and comparative examples were placed in an environment with an ambient temperature of (25±2)℃ and charged to 4.5V at a constant current density of 1C (cutoff current of 0.05C). After the batteries were fully charged, they were left to stand for 5 minutes and then discharged at a constant current density of 0.5C (cutoff voltage of 3.0V). The discharge capacity was recorded as the initial capacity Q0. When the cycle reached 600 cycles, the last discharge capacity Q1 of the battery was recorded. The capacity retention rate (%) = (Q1 / Q0) × 100%. The results are recorded in Table 2.

[0227] (3) Self-discharge test

[0228] The batteries prepared in the examples and comparative examples were placed in an environment with an ambient temperature of (25±2)℃ and stored for 24 hours. The open-circuit voltage OCV1 was measured and the time t1 was recorded. The batteries were stored for another 72 hours and the time t2 was recorded. The open-circuit voltage OCV2 was measured again. The K value was (OCV1-OCV2) / (t1-t2). The test conditions were a cutoff voltage of 4.48V. The results are recorded in Table 2.

[0229] (4) Furnace temperature test

[0230] The batteries prepared in the examples and comparative examples were placed in an ambient temperature of (25±2)℃ and charged at 0.5C to the upper limit voltage of 4.5V and the cutoff current of 0.05C. Then, the batteries were placed in a 130℃ thermal shock test chamber and the temperature was increased to 130℃ at a rate of 5℃ / min±2℃ / min and maintained for 60min. If the battery did not smoke, catch fire, or explode, it was considered to have passed. The results were recorded in Table 2. In Table 2, 10P / 10T means that 10 samples were tested and 10 passed; 8P / 10T means that 8 out of 10 samples were tested and 8 passed; and so on.

[0231] (5) Acupuncture test

[0232] The batteries prepared in the examples and comparative examples were pierced with a high-temperature resistant steel needle with a diameter of 5mm-8mm (the cone angle of the needle tip was 45°-60°) at a speed of (25±5)mm / s from a direction perpendicular to the battery plates. The piercing position should be close to the geometric center of the pierced surface (the steel needle remained in the battery). The battery state was recorded. The battery was considered to have passed when it did not catch fire or explode. The results were recorded in Table 2. In Table 2, 10P / 10T means that 10 samples were tested and 10 passed; 8P / 10T means that 8 out of 10 samples were tested and 8 passed; and so on.

[0233] (6) High-temperature storage performance test

[0234] The batteries prepared in the examples and comparative examples were charged at an ambient temperature of (25±3)℃ and stored at a high temperature of (85±3)℃ for 8 hours while maintaining 100% SOC. After the charging was completed, the batteries were left to stand at an ambient temperature of (25±3)℃ for 2 hours. Then, the batteries were charged and discharged at an ambient temperature. The maximum capacity of the first 3 cycles was recorded as the recovery capacity Q2, where Q0 was obtained from the cycle test in (2). The recovery capacity retention rate (%) = Q2 / Q0 × 100%. The results are recorded in Table 2.

[0235] (7) Peel force test

[0236] The batteries prepared in the examples and comparative examples were placed in an environment with a temperature of (25±2)℃. The part of the negative electrode sheet and the separator (and the positive electrode sheet and the separator) that were bonded to each other was taken out of the lithium-ion battery and cut into 2mm×2mm samples. The free end of the sample was folded over a certain angle (180°) and the adhesive surface was peeled off by about 50mm. The two ends of the peeled adhesive surface were fixed on both sides of the peel force tester. The instrument was started to peel off the free end of the sample and the peel force was obtained. The results are recorded in Table 2.

[0237] Table 2

[0238] As can be seen from Table 2, compared with the comparative example, the battery disclosed in this invention has significantly improved capacity retention rate after 600 cycles, furnace temperature test pass rate, nail penetration test pass rate and recovery capacity retention rate, and significantly reduced K value.

[0239] The preferred embodiments of this disclosure have been described in detail above; however, this disclosure is not limited thereto. Within the scope of the technical concept of this disclosure, various simple modifications can be made to the technical solutions of this disclosure, including combining the various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in this disclosure and are all within the protection scope of this disclosure.

Claims

1. A battery, characterized in that, The battery includes a separator and an electrolyte; The diaphragm includes a substrate layer and a ceramic layer on at least one surface of the substrate layer, the ceramic layer includes inorganic particles, the inorganic particles include element Al, and the content of element Al is a based on the total weight of the diaphragm, 12% ≤ a ≤ 32%; The electrolyte includes ethyl butyrate, and based on the total weight of the electrolyte, the content of ethyl butyrate is c1, where 5% ≤ c1 ≤ 35%. a and c1 satisfy 0.2≤c1 / a≤2.

5.

2. The battery according to claim 1, wherein, 0.35≤c1 / a≤1.7; preferably, 0.5≤c1 / a≤1.2; And / or, the thickness of the diaphragm is b, where 4μm≤b≤16μm.

3. The battery according to claim 1 or 2, wherein, 18％≤a≤28％； And / or, 10% ≤ c1 ≤ 30%.

4. The battery according to any one of claims 1-3, wherein, The inorganic particles include at least one of aluminum-containing inorganic particles, silicon oxide, magnesium oxide, magnesium hydroxide, and zirconium oxide; Preferably, the aluminum-containing inorganic particles include at least one of alumina, aluminum hydroxide, montmorillonite, and boehmite; Preferably, the content of inorganic particles is 20%-60% based on the total weight of the diaphragm.

5. The battery according to any one of claims 1-4, wherein, The battery further includes a positive electrode sheet, which comprises a positive electrode active material, and the positive electrode active material comprises first particles and second particles, wherein the median particle size Dv of the first particles is... 1 50 is less than the median particle size Dv of the second particle 2 50; Preferably, 3μm≤Dv 1 50≤15μm; Preferably, 4μm≤Dv 2 50≤18μm; More preferably, 4μm≤Dv 1 50≤5μm; More preferably, 14μm≤Dv 2 50≤16μm.

6. The battery according to claim 5, wherein, The particle size of the positive electrode active material is 2μm≤Dv10≤10μm, 8μm≤Dv50≤20μm, 20μm≤Dv90≤40μm, and Dv99≤52μm. Preferably, the positive electrode active material comprises Li a Co z M 1 x M 2 y For O2, 0.9 ≤ a ≤ 1.1, 0.01 ≤ x ≤ 0.1, 0 ≤ y ≤ 0.05, 0.85 ≤ z ≤ 0.99, M 1 Includes at least one of Mn, Al and Mg, M 2 It includes at least one of Zr, Ni, Y, Sr, W, Sc, B, Si, Ti, Sn, Tb, Nb, Sb, Se, C, La, Ta, and Te.

7. The battery according to any one of claims 1-6, wherein, The battery also includes a negative electrode sheet, which comprises silicon-based particles, and the median particle size Dv50 of the silicon-based particles is d. The electrolyte also includes nitrile additives and fluorocyclic carbonate additives. Based on the total weight of the electrolyte, the content of the nitrile additives is c2 and the content of the fluorocyclic carbonate additives is c3. c1, c2, c3 and d satisfy 1≤(0.01×d+c1) / (c2+c3)≤8; Preferably, 1.2 ≤ (0.01 × d + c1) / (c2 + c3) ≤ 3.7; More preferably, 1.5≤(0.01×d+c1) / (c2+c3)≤3.

8. The battery according to claim 7, wherein, 2% ≤ c2 ≤ 6%; preferably, 4% ≤ c2 ≤ 5%; And / or, 5% ≤ c3 ≤ 15%; preferably, 8% ≤ c3 ≤ 12%.

9. The battery according to claim 7, wherein, 5μm≤d≤20μm; Preferably, 10μm≤d≤18μm.

10. The battery according to any one of claims 7-9, wherein, The silicon-based particles include at least one of elemental silicon, silicon-oxygen, silicon-carbon, and silicon alloys; the negative electrode sheet includes a negative electrode active material, which includes the silicon-based particles; the weight content of the silicon-based particles in the negative electrode active material is 1%-50%; Preferably, the fluorocyclic carbonate additive includes fluoroethylene carbonate.

11. The battery according to any one of claims 7-10, wherein, The nitrile additives include butadienenitrile and 1,3,6-hexanetrionitrile; Preferably, the weight ratio of the butadionitrile to the 1,3,6-hexanetrionitrile is 1:(1-2).

12. The battery according to any one of claims 1-11, wherein, The electrolyte also includes unsaturated silane additives; Preferably, based on the total weight of the electrolyte, the content of the unsaturated silane additive is c4, 0.05% ≤ c4 ≤ 1%; Preferably, 0.2% ≤ c4 ≤ 0.5%; Preferably, the unsaturated silane additive includes hexavinyldisiloxane.

13. The battery according to any one of claims 1-12, wherein, The battery further includes a positive electrode and a negative electrode, wherein the positive electrode, the separator, and the negative electrode are stacked together, and the ceramic layer faces the positive electrode. Preferably, the diaphragm further includes an adhesive layer located on at least one outer surface of the diaphragm.

14. The battery according to any one of claims 1-13, wherein, The thickness of the substrate layer is 3μm-14μm, and the thickness of the ceramic layer is 0.2μm-2.5μm; Preferably, the thickness of the substrate layer is 5μm-10μm, and the thickness of the ceramic layer is 0.5μm-1.5μm; Preferably, the diaphragm further includes an adhesive layer with a thickness of 0.5 μm-5 μm, more preferably 1 μm-3 μm.

15. The battery according to any one of claims 1-14, wherein, The battery also includes a positive electrode and a negative electrode, and the peel force between the separator and the positive electrode is 3N / m-20N / m; And / or, the peel force between the diaphragm and the negative electrode sheet is 6N / m-30N / m.

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