A battery and device

Abstract

The application belongs to the technical field of battery preparation, and particularly relates to a battery and a device. The battery comprises a negative electrode sheet, the negative electrode sheet comprises a current collector and a negative electrode active material layer arranged on at least one surface of the current collector, the negative electrode active material layer comprises a negative electrode active material, and the negative electrode active material comprises a silicon-containing material. The silicon content in the negative electrode active material layer and the elongation at break of the negative electrode current collector satisfy a specific relationship, which not only can ensure the lithium ion embedding capacity of the negative electrode while reducing the risk of negative electrode foil cracking caused by negative electrode expansion, but also can avoid the risk of positive and negative electrode short circuit caused by the negative electrode foil cracking process, thereby improving the capacity density, cycle performance and safety performance of the battery.

Description

Technical Field

[0001] This invention belongs to the field of battery manufacturing technology, specifically relating to a battery and a device. Background Technology

[0002] Lithium-ion batteries possess advantages such as high energy density, long cycle life, low self-discharge rate, and no memory effect, making them promising for widespread application in the new energy field. With the development of science and technology, the performance requirements for lithium-ion batteries are becoming increasingly stringent. As the demand for battery energy density continues to rise, safety issues are becoming increasingly prominent. Especially when the negative electrode contains silicon, balancing the battery's energy density, safety, and cycle performance remains a technical challenge for those skilled in the art. Summary of the Invention

[0003] The purpose of this invention is to overcome the shortcomings of the existing technology and provide a battery and device that can ensure that the battery has good energy density, good cycle performance and safety.

[0004] To this end, the present invention provides the following technical solution.

[0005] A first aspect of the present invention provides a battery comprising a negative electrode sheet, the negative electrode sheet comprising a current collector and a negative electrode active material layer disposed on at least one surface of the current collector, the negative electrode active material layer comprising a negative electrode active material comprising a silicon-containing material; the silicon content in the negative electrode active material layer and the elongation at break of the negative electrode current collector satisfy the following relationship:

[0006]

[0007] Wherein, A is the elemental silicon content in the negative electrode active material layer, in wt%;

[0008] B represents the elongation at break of the negative electrode current collector, expressed as a percentage.

[0009] As an optional implementation, A ranges from 1.5 wt% to 17.5 wt%; and / or, B ranges from 3% to 100%.

[0010] As an optional implementation, the negative electrode current collector includes at least a first conductive layer and a first polymer substrate layer; the first polymer substrate layer is disposed between two adjacent first conductive layers;

[0011] The silicon content in the negative electrode active material layer and the elongation at break of the negative electrode current collector satisfy the following relationship:

[0012]

[0013] As an optional implementation, the range of B is 10% to 80%.

[0014] As an optional implementation, the negative electrode current collector is a metal foil, and the silicon content in the negative electrode active material layer and the elongation at break of the negative electrode current collector satisfy the following relationship:

[0015]

[0016] As an optional implementation, the range of B is 5% to 15%.

[0017] As an optional implementation, the battery includes a positive electrode sheet, and the silicon content in the negative electrode active material layer and the elongation at break of the positive electrode current collector satisfy the following relationship:

[0018]

[0019] Wherein, D is the elongation at break of the positive electrode current collector, in percentage (%).

[0020] As an optional implementation, the range of D is 3% to 90%.

[0021] As an optional implementation, the positive electrode current collector includes a second conductive layer and a second polymer substrate layer, with the second polymer substrate layer disposed between adjacent second conductive layers; the silicon content in the negative electrode active material layer and the elongation at break of the positive electrode current collector satisfy the following relationship:

[0022]

[0023] As an optional implementation, the range of D is 10% to 80%.

[0024] As an optional implementation, the positive current collector is a metal foil; the silicon content in the negative electrode active material layer and the elongation at break of the positive current collector satisfy the following relationship:

[0025]

[0026] As an optional implementation, the range of D is 5% to 15%.

[0027] As an optional implementation, the difference between the elongation at break B of the negative current collector and the elongation at break D of the positive current collector is 1% to 3%.

[0028] A second aspect of the present invention provides an apparatus comprising the battery described above.

[0029] The beneficial effects of this invention are as follows:

[0030] This invention provides a battery that, by controlling the silicon content and the elongation at break of the negative electrode within a suitable range, can not only ensure the lithium-ion intercalation capability of the negative electrode while reducing the risk of cracking of the negative electrode foil due to negative electrode expansion, but also avoid the risk of short circuit between the positive and negative electrodes caused by the breakage of the negative electrode foil, thereby improving the battery's energy density, cycle performance, and safety performance. Detailed Implementation

[0031] The following embodiments are provided to better understand the present invention and are not limited to the preferred embodiments described. They do not constitute a limitation on the content and scope of protection of the present invention. Any product that is the same as or similar to the present invention, derived by any person under the guidance of the present invention or by combining the features of the present invention with other prior art, falls within the protection scope of the present invention.

[0032] Where specific experimental steps or conditions are not specified in the examples, they can be performed according to the conventional experimental steps or conditions described in the literature in this field. Reagents or instruments whose manufacturers are not specified are all commercially available conventional reagent products.

[0033] This invention provides a battery comprising a negative electrode sheet, the negative electrode sheet comprising a current collector and a negative electrode active material layer disposed on at least one surface of the current collector, the negative electrode active material layer comprising a negative electrode active material, the negative electrode active material comprising a silicon-containing material; the silicon content in the negative electrode active material layer and the elongation at break of the negative electrode current collector satisfy the following relationship:

[0034]

[0035] Wherein, A is the elemental silicon content in the negative electrode active material layer, in wt%;

[0036] B represents the elongation at break of the negative electrode current collector, expressed as a percentage.

[0037] In this invention, when the ratio of A to B meets the above-mentioned range, it can improve the overall energy density of the battery, ensure the lithium-ion intercalation capability of the negative electrode, and prevent silicon expansion from causing electrode breakage, thus avoiding the risk of short circuit between the positive and negative electrodes during the negative electrode breakage process. This improves the battery's energy density, cycle performance, and safety performance. When the ratio of A to B does not meet the above-mentioned range, the electrode cannot withstand the expansion of silicon, leading to electrode breakage and a short circuit risk. Furthermore, when the ratio of A to B does not meet the above-mentioned range, it can also cause the active material layer on the electrode surface to crack easily, thereby affecting the battery life.

[0038] In this invention, the range of A is 1.5wt% to 17.5wt%; and / or the range of B is 3% to 100%. A represents the silicon content. During charging, silicon undergoes an alloying reaction, resulting in a volume change of up to 300% after lithium intercalation. As the silicon content increases, expansion increases; the larger the silicon grains, the greater the relative expansion. When A is within the above range, it not only improves the lithium intercalation capability of the negative electrode and the number of lithium ions intercalated, thereby increasing the battery capacity, but also prevents excessive silicon content from causing excessive expansion during charging, which could damage the electrode, lead to foil breakage, and ultimately affect battery life. When B is within the above range, it not only allows the negative electrode foil to adapt to the expansion of silicon particles, preventing cracking, but also avoids short circuits caused by excessive elongation at break, which could lead to the negative electrode foil overlapping with the casing or positive electrode; thus improving battery safety. Therefore, controlling B within the above range can reduce strip breakage during processing and improve production efficiency.

[0039] In this invention, the negative electrode current collector includes at least a first conductive layer and a first polymer substrate layer; the first polymer substrate layer is disposed between two adjacent first conductive layers; the silicon content A in the negative electrode active material layer and the elongation at break B of the negative electrode current collector satisfy the following relationship:

[0040]

[0041] When the negative electrode current collector includes a polymer substrate layer, the elongation at break of the negative electrode current collector is greater than that of ordinary current collectors, making it less prone to tearing under tension and reducing the probability of demolding and breakage of the negative electrode sheet. Furthermore, when the negative electrode current collector includes a polymer substrate layer, and A and B meet the above-mentioned ranges, the battery energy density and battery safety performance can be further improved. The first polymer substrate layer is made of polymers such as PET (polyethylene terephthalate), PP (polypropylene), and PI (polyimide), and its thickness is 4–15 μm; the first conductive layer is copper, and its thickness is 0.8–5 μm.

[0042] In this invention, when the negative electrode current collector includes a conductive layer and a polymer substrate layer, the range of B is 10% to 80%, the negative electrode current collector is a composite foil, and the elongation at break of the composite foil is within this range, which can improve the toughness of the composite foil, prevent stress concentration in the conductive layer, and improve the safety performance of the battery.

[0043] In this invention, the negative electrode current collector is a metal foil, and the silicon content in the negative electrode active material layer and the elongation at break of the negative electrode current collector satisfy the following relationship:

[0044]

[0045] When the negative electrode current collector is a metal foil, the silicon content A and the elongation at break B of the negative electrode current collector in this invention meet the above ranges, which can further improve the battery energy density, cycle performance and safety performance.

[0046] The range of B is 5% to 15%, and the negative electrode current collector is a metal foil. When the metal foil is within a suitable range, it can reduce the internal resistance of the battery, increase the energy density of the battery, and also ensure the overcurrent capacity of the foil, thus ensuring the safety performance of the battery.

[0047] In this invention, the battery includes a positive electrode sheet, and the silicon content in the negative electrode active material layer and the elongation at break of the positive electrode current collector satisfy the following relationship:

[0048]

[0049] Wherein, D is the elongation at break of the positive electrode current collector, in percentage (%).

[0050] After winding or stacking, batteries undergo a hot-pressing process. During hot pressing, some of the binder components in the positive and negative active material layers melt, thus providing a certain degree of adhesion between the positive and negative electrodes and the separator. Alternatively, the industry currently selects adhesive separators with sticky surfaces to further enhance the bond strength between the positive and negative electrodes and the separator. Given this bond strength, when the surface active material of the negative electrode expands, the negative electrode stretches, causing the more elastic separator to also stretch. The separator then further diffuses the tension to the positive electrode. If the elongation at break (D) of the positive current collector is low, the expansion of the negative active material may cause the negative electrode to stretch, leading to the breakage of the positive electrode and detachment of the positive active material from the positive current collector. Therefore, by controlling the silicon content A in the negative electrode active material layer and the elongation at break D of the positive electrode current collector to meet the above range, the present invention can reduce the occurrence of the positive electrode sheet being pulled apart, the positive electrode active material being demolded from the positive electrode current collector, and the active material layer cracking.

[0051] In this invention, the range of D is 3% to 90%. This invention enables the elongation at break D of the positive electrode current collector to meet the above range, which can further improve the cycle life of the battery and reduce the internal resistance of the battery.

[0052] In this invention, the positive electrode current collector includes a second conductive layer and a second polymer substrate layer, with the second polymer substrate layer disposed between two adjacent second conductive layers; the silicon content in the negative electrode active material layer and the elongation at break of the positive electrode current collector satisfy the following relationship:

[0053]

[0054] This invention introduces a conductive layer and a polymer substrate layer into the positive electrode current collector, which can further reduce the occurrence of electrode breakage and positive electrode active material demolding, and can also improve the safety performance of the battery and increase the energy density of the battery.

[0055] In this invention, when the positive electrode current collector includes a conductive layer and a polymer substrate layer, the range of D is 10% to 80%, which can further improve the mechanical stability of the battery, extend the battery life, and improve the cell manufacturing efficiency and yield.

[0056] In this invention, the positive electrode current collector is a metal foil; the silicon content in the negative electrode active material layer and the elongation at break of the positive electrode current collector satisfy the following relationship:

[0057]

[0058] The present invention uses a metal foil as the positive electrode current collector, and the elongation at break of the positive electrode current collector and the silicon content in the negative electrode active material layer meet the above-mentioned ranges. This can further reduce the occurrence of positive electrode active material demolding and electrode breakage, further reduce accidental contact between the positive and negative electrodes, and improve the safety performance of the battery.

[0059] In this invention, when the positive electrode current collector is a metal foil, the range of D is 5% to 15%. Within this range, the mechanical stability and safety performance of the battery can be further improved.

[0060] In this invention, the difference between the elongation at break (B) of the negative electrode current collector and the elongation at break (D) of the positive electrode current collector is 1% to 3%. By controlling the elongation at break of the two current collectors to meet the above range, the DCR is smaller, the negative electrode active material layer and the positive electrode active material layer are matched, reducing the risk of lithium plating on the negative electrode and increasing the cycle capacity retention rate.

[0061] The present invention prepares the above-mentioned battery using conventional methods in the art. For example, it includes the following steps:

[0062] (1) Preparation of negative electrode sheet

[0063] The negative electrode active material is mixed with additives, and a solvent is added to obtain a negative electrode slurry. The negative electrode slurry is coated onto at least one surface of the negative electrode current collector, and after drying, cold pressing, and slitting, a negative electrode sheet is obtained. Additives include conductive agents, binders, thickeners, etc.

[0064] The negative electrode active material, conductive agent, binder, and thickener are made of materials commonly used in the art. For example, the conductive agent is one or more of acetylene black, SWCNT, etc.; the thickener is CMC, etc.; and the binder is SBR, etc. The negative electrode active material includes silicon-containing materials, which are at least one of nano-silicon-carbon composite negative electrode materials and silicon suboxide negative electrode materials; wherein, the silicon suboxide negative electrode material can also be a pre-magnesized or pre-lithiated silicon suboxide negative electrode material. This invention does not impose specific limitations on the preparation method of the silicon-containing material; those skilled in the art can choose any silicon-containing material prepared by existing technologies according to their needs. Several preparation methods for silicon-containing materials are listed here:

[0065] Preparation method of silicon-carbon composite anode material by vapor phase method

[0066] Porous carbon materials as carbon matrix (porous carbon type: pore size 4-5 nm, specific surface area range 900-1800 m²) 2 The sample (g) is added to a rotary kiln, and nitrogen is introduced to purge oxygen. The kiln is then heated and calcined. The nitrogen flow rate, calcination temperature and heating rate, and rotary kiln rotation speed are common parameters in the field. For example, the nitrogen flow rate can be set to 8–25 L / min, the calcination heating rate to 10–30 °C / min, the temperature to 500–800 °C, and the rotary kiln rotation speed to 100–300 rpm. While maintaining the calcination temperature, a mixed gas is introduced. This mixed gas consists of nitrogen and silane (e.g., methylene silane) in a volume ratio of 1:(1–7). The flow rate of the mixed gas is 0.1–0.2 L / min. Specifically, the gas is introduced at a flow rate of 0.1–0.2 L / min for 8 hours, then at a flow rate of 0.2–0.4 L / min for 8 hours, and then at a flow rate of 0.1–0.2 L / min for another 8 hours. After the reaction is complete, stop the flow of silane gas and only introduce nitrogen gas. Calcinate in a nitrogen atmosphere at a temperature of 500–600℃ and a heating rate of 10–20℃ / min. Once the temperature stabilizes, introduce acetylene gas at a rate of 0.8–2.5 L / min to carry out the reaction. Continue introducing acetylene gas for 5–12 hours, then turn off the acetylene gas and allow the material to cool naturally in a nitrogen atmosphere. After it has completely cooled to room temperature, remove the material and crush, sieve, and demagnetize it to obtain the silicon-carbon composite anode material.

[0067] Preparation method of silicon suboxide anode material

[0068] Precursor preparation: Silica powder and silicon powder are mixed uniformly in a VC mixer at a molar ratio of 1:0.5–3. The uniformly mixed powder is then subjected to high-temperature vacuum treatment in a vacuum atmosphere furnace sample chamber. The temperature range of the high-temperature vacuum treatment is 600–1800℃. After high-temperature vacuum treatment, the material is subjected to air jet milling and then passed through a dust removal device to obtain precursor powder with fine powder removed. Precursor coating: The above-mentioned precursor powder with fine powder removed is placed in a continuous rotary furnace. A mixed gas, including argon and acetylene, is introduced into the rotary furnace at a volume ratio of 1:1. The gas is introduced at a rate of 0.2–1.5 L / min for 20–60 min. The air in the furnace tube is then discharged, and the temperature is increased to 700–800℃ at a rate of 5–10℃ / min for 1–4 h to obtain silicon suboxide anode material.

[0069] Preparation method of silicon-carbon composite materials by sand milling

[0070] Silicon powder with a particle size of 1-20 μm and graphite are mixed in an organic solvent at a mass ratio of 1:1-5 and then ball-milled at a speed of 300-700 rpm to obtain precursor powder. Pitch and precursor powder are mixed at a mass ratio of 1:2-4 and sintered in a nitrogen atmosphere at a temperature of 500-1200℃ for 4-10 hours, and then naturally cooled to room temperature to obtain silicon-carbon composite material.

[0071] The mass ratio of the negative electrode active material, conductive agent, thickener and binder adopts the conventional ratio in the art. For example, the mass ratio of silicon-carbon composite material, conductive agent and binder is (96-98.5):(1.0-2.5):(0.5-1.5).

[0072] The current collector can be a composite current collector or a metal foil. For example, a composite current collector includes a conductive layer and a polymer substrate layer, with a polymer substrate layer between adjacent conductive layers. The conductive layer and the polymer substrate layer are made of conventional materials in the art; for example, the conductive layer is made of Cu. The polymer substrate layer is made of PET (polyethylene terephthalate), PP (polypropylene), PI (polyimide), etc. The metal foil is made of conventional materials in the art; for example, the metal foil is Cu foil.

[0073] (2) Preparation of positive electrode sheet

[0074] The positive electrode active material and additives are mixed, and a solvent is added to obtain a positive electrode slurry. The positive electrode slurry is coated on at least one surface of the positive electrode current collector, and after drying, cold pressing, and slitting, a positive electrode sheet is obtained. Additives include conductive agents, binders, etc.

[0075] The positive electrode active material, conductive agent, and binder are made of materials commonly used in the art. For example, the conductive agent is one or more of acetylene black, SWCNT, etc.; the binder is SBR, etc. The positive electrode active material is a ternary positive electrode active material, which may be, but is not limited to, CM523, NCM622, and NCM811. The types and amounts of the positive electrode active material, conductive agent, binder, and solvent can be selected according to requirements. For example, the mass ratio of the positive electrode active material, conductive agent, and binder is (96–98.2):(1–2):(0.8–2).

[0076] The current collector can be a composite current collector or a metal foil. For example, a composite current collector includes a conductive layer and a polymer substrate layer, with a polymer substrate layer between adjacent conductive layers. The conductive layer and the polymer substrate layer are made of conventional materials in the art; for example, the conductive layer is made of Al. The polymer substrate layer is made of PET (polyethylene terephthalate), PP (polypropylene), PI (polyimide), etc. The metal foil is made of conventional materials in the art; for example, the metal foil is Al foil.

[0077] (3) Electrolyte

[0078] The electrolyte of this invention can be any electrolyte suitable for electrochemical energy storage devices in the art. The electrolyte includes an electrolyte and a solvent, and typically includes a lithium salt. The concentration of lithium salt in the electrolyte is 0.5–2.5 mol / L.

[0079] Conventional lithium salts in the art are used, and as an example, the lithium salt is at least one of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bisfluorosulfonylimide (LiFSI), lithium bistrifluoromethanesulfonylimide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalate borate (LiDFOB), lithium dioxalate borate (LiBOB), lithium difluorophosphate (LiPO2F2), lithium difluorodioxalate phosphate (LiDFOP), and lithium tetrafluorooxalate phosphate (LiTFOP).

[0080] The solvent can be one or more components such as cyclic carbonates (fluoroethylene carbonate (FEC), propylene carbonate (PC), ethylene carbonate (EC)), linear carbonates (dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC)), and carboxylic acid esters (methyl propionate (EP)).

[0081] (4) Diaphragm

[0082] A separator is placed between the positive and negative electrode plates to separate them and prevent short circuits caused by contact. This invention does not specify the manufacturer, manufacturing process, or type of separator. As an example, the separator can be a PE (polyethylene) film or a PP (polypropylene) film, etc.

[0083] (5) The above positive electrode, separator and negative electrode are stacked in sequence and wound to obtain a bare cell; the bare cell is placed in the outer packaging shell, dried, injected with electrolyte, and then packaged, left to stand and formed to obtain a lithium-ion battery.

[0084] This invention also provides a device including the aforementioned battery. This device refers to any equipment that can utilize electrical energy and convert it into mechanical energy, thermal energy, light energy, or one or more other energy-generating devices, such as electric motors, electric heaters, and electric light sources. Examples include, but are not limited to, electric vehicles, electric trains, ships, and mobile phones.

[0085] The present invention is further illustrated below with specific embodiments:

[0086] The silicon content A in the negative electrode active material layer, the current collector elongation at break, and the battery performance in the following embodiments and comparative examples were obtained by testing using the following methods.

[0087] (1) Test method for silicon content in the negative electrode active material layer:

[0088] The disassembled negative electrode sheet was immersed in a container containing DMC. After 8 hours of immersion, the negative electrode sheet was placed in a 45℃ oven and baked for 30 minutes to remove residual solvent, yielding the treated electrode sheet. The silicon content was tested using cross-sectional polishing and scanning electron microscopy (SEM). The treated negative electrode sheet was cross-sectionally polished using an argon ion beam. Four sections of the same sample were scanned using SEM at 500x magnification. The average value of all silicon content values ​​obtained from the 16 fields of view of the four sections was taken as the most accurate conclusion, i.e., the silicon content in the negative electrode active material layer. The silicon content in the negative electrode active material layer refers to the percentage of silicon by mass in the total mass of the negative electrode active material layer.

[0089] (2) Test method for elongation at break of current collector:

[0090] The battery is disassembled to obtain the electrode sheets. These sheets are then immersed in a container of deionized water and ultrasonically cleaned for 30 minutes to remove the active material from the current collector surface. The immersed electrode sheets are then baked in a 45°C oven for 10 minutes to remove residual moisture. A 150mm long and 15mm wide strip sample is cut using a separator slitting machine. The initial gauge length between the fixtures is 100mm, and the tensile speed is (100±10)mm / min. A static tensile load is applied uniformly along the foil axis until the foil breaks. The elongation at this point is measured, and divided by the gauge length, yields the elongation at break. The elongation at break for both the positive and negative current collectors can be obtained using this test method.

[0091] (3) Electrochemical performance testing methods:

[0092] Cyclic performance testing method: At 25°C, the lithium-ion batteries prepared in the examples and comparative examples were cycled according to the following procedure: charged to 4.25V at a 1 / 3C rate and then discharged to 2.5V at a 1 / 3C rate. This cycle was repeated until the capacity of the lithium-ion battery was less than 80% of the initial capacity, and the number of cycles at this point was recorded.

[0093] (4) Integrity test of the positive and negative electrode plates of the battery

[0094] At 25°C, the lithium-ion batteries prepared in the examples and comparative examples were subjected to cycle tests according to the following procedure: charged to 4.25V at a 1 / 3C rate; then discharged to 2.5V at a 1 / 3C rate. After 500 cycles, the lithium-ion batteries obtained in each example and comparative example were disassembled, and the integrity of the positive and negative electrode plates was observed.

[0095] (5) Test of self-discharge value

[0096] At 25℃, first charge to 4.25V at a 1 / 3C rate, let stand for 10 minutes, then discharge to 2.5V at a 1 / 3C rate, let stand for 10 minutes, repeat this cycle 100 times. Then charge again at a 1 / 3C rate to 4.25V and let stand for 30 minutes. Measure the open-circuit voltage at this point and record it as OCV1. Continue to let stand for 2 days and record the open-circuit voltage at this point as OCV2. Calculate the voltage drop (K value) according to the formula; the formula for calculating the K value is as follows:

[0097]

[0098] Example 1

[0099] This embodiment provides a battery, the preparation method of which includes:

[0100] (1) Preparation of negative electrode sheet

[0101] Porous carbon materials were used as the carbon matrix (porous carbon type: pore size 4-5 nm, specific surface area range 900-1800 m²). 2 / g), added to a rotary kiln, nitrogen gas was introduced to purge oxygen at a flow rate of 10 L / min. After purging, the temperature was raised to 500℃, the heating rate was 10℃ / min, and the rotation speed was 100 rpm. The temperature was kept constant, and a mixture of nitrogen and silane in a volume ratio of 1:4 was introduced. The mixture was first introduced at a flow rate of 0.15 L / min for 8 hours, then at a flow rate of 0.3 L / min for 8 hours, and finally at a flow rate of 0.2 L / min for 8 hours. After the reaction was completed, the silane gas was turned off, and the mixture was purged under a nitrogen atmosphere at a temperature of 550℃ and a heating rate of 10℃ / min. When the temperature stabilized, acetylene gas was introduced at a flow rate of 1 L / min. The temperature was kept constant, and the mixture was purged for 10 hours. Then the acetylene gas was turned off, and the mixture was allowed to cool naturally under a nitrogen atmosphere. After cooling was complete, the material was removed, crushed, sieved, and demagnetized to obtain the silicon-carbon composite material.

[0102] The aforementioned carbon-coated silicon-carbon composite material, conductive agent acetylene black binder SBR, and other components were mixed at a mass ratio of 97:1.5:1.5. Deionized water was added as a solvent, and the mixture was stirred under vacuum to obtain a negative electrode slurry. The negative electrode slurry was uniformly coated onto both surfaces of the negative electrode current collector copper foil, air-dried at room temperature, and then transferred to an oven for further drying. After cold pressing and slitting, the negative electrode sheet was obtained. The elongation at break of the copper foil is shown in Table 1.

[0103] (2) Preparation of positive electrode sheet

[0104] The positive electrode active material NCM811, conductive agent acetylene black, and binder PVDF were mixed at a mass ratio of 96:2:2. NMP solvent was added, and the mixture was stirred under vacuum to obtain a positive electrode slurry. The positive electrode slurry was coated on both surfaces of the positive electrode current collector aluminum foil, air-dried at room temperature, and then transferred to an oven for further drying. After cold pressing and slitting, the positive electrode sheet was obtained. The elongation at break of the aluminum foil is shown in Table 1.

[0105] (3) Electrolyte

[0106] Ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) were mixed in a volume ratio of 1:1:1 to obtain an organic solvent. Then, fully dried lithium salt LiPF6 was dissolved in the mixed organic solvent to prepare an electrolyte with a lithium salt concentration of 1 mol / L.

[0107] (4) Diaphragm

[0108] Polyvinyl alcohol is used as the diaphragm.

[0109] (5) Stack the above positive electrode, separator and negative electrode in sequence, so that the separator is between the positive and negative electrode to play the role of isolation, and then wind them to obtain a bare cell; place the bare cell in the outer packaging shell, dry it and inject electrolyte, and then vacuum seal, stand and form to obtain a lithium-ion battery.

[0110] Example 2

[0111] This embodiment provides a battery that is basically the same as that in Embodiment 1, except that the preparation method of the negative electrode active material, the elongation at break of the negative electrode current collector, and the elongation at break of the positive electrode current collector are different. The elongation at break of the negative electrode current collector and the positive electrode current collector are shown in Table 1. In this embodiment, the negative electrode active material is a silicon suboxide negative electrode material, and its preparation method includes: mixing silicon dioxide powder and silicon powder in a molar ratio of 1:2 uniformly in a VC mixer; subjecting the uniformly mixed powder to high-temperature vacuum treatment in a vacuum atmosphere furnace sample chamber at 1650℃; pulverizing the high-temperature treated material under an air jet mill; and obtaining a precursor powder with fine powder removed by a dust removal device. The precursor powder was placed in a continuous rotary furnace, and a mixture of inert argon and acetylene gas was introduced into the furnace at a volume ratio of 1:1. The gas was introduced at a rate of 1 L / min for 30 min, and the air in the furnace tube was purged. The mixture was then calcined at 750 °C for 2 h at a heating rate of 5 °C / min. After the temperature dropped to room temperature, the sample was removed to obtain silicon suboxide anode material.

[0112] Example 3

[0113] This embodiment provides a battery that is basically the same as that in Embodiment 1, except that the preparation method of the negative electrode active material, the elongation at break of the negative electrode current collector, and the elongation at break of the positive electrode current collector are different. The elongation at break of the negative electrode current collector and the positive electrode current collector are shown in Table 1. The negative electrode active material in this embodiment is a silicon-carbon composite negative electrode material, and its preparation method includes: mixing silicon powder with a particle size of 3-5 μm and graphite in an organic solvent at a mass ratio of 1:3, and then ball milling the mixture at a ball mill speed of 500 rpm to obtain precursor powder; mixing asphalt with the precursor powder at a mass ratio of 1:3, placing the mixture in a nitrogen atmosphere, sintering it at 800°C for 8 hours, and then naturally cooling it to room temperature to obtain a silicon-carbon composite material.

[0114] Examples 4-7

[0115] Examples 4-7 provide a battery that is basically the same as that in Example 1, except that the silicon content in the negative electrode active material layer is different, the elongation at break of the negative electrode current collector is different, and the elongation at break of the positive electrode current collector is different.

[0116] Comparative Examples 1-4

[0117] This comparative example provides a battery that is basically the same as that in Example 1, except that the silicon content in the negative electrode active material layer is different, the elongation at break of the negative electrode current collector is different, and the elongation at break of the positive electrode current collector is different.

[0118] The silicon content A, elongation at break B of the negative electrode current collector, and elongation at break D of the positive electrode current collector in Examples 1-7 and Comparative Examples 1-4 are shown in Table 1, and the test results are shown in Table 2.

[0119] Table 1. Parameters of Examples 1-7 and Comparative Examples 1-4

[0120]

[0121]

[0122] Table 2 Test results of Examples 1-7 and Comparative Examples 1-4

[0123]

[0124] As can be seen from the above results, in conjunction with Examples 6-7, this invention, based on the premise that the ratio of silicon content A in the negative electrode active material layer to the elongation at break B of the negative electrode current collector is 0.17-0.6, further adjusts the silicon content A in the negative electrode active material layer and the elongation at break D of the positive electrode current collector to 0.19-0.55, which can further improve the battery cycle performance and reduce problems such as wrinkling and material layer cracking of the positive electrode sheet. Furthermore, in conjunction with Comparative Examples 1-2, when the ratio of silicon content A in the negative electrode active material layer to the elongation at break B of the negative electrode current collector is too large or too small, wrinkling of the negative electrode sheet, cracking of the active material, and foil breakage will occur, and the battery cycle performance will significantly decrease. The K value is an indicator for evaluating the short-circuit risk of a battery. A K value exceeding 0.045 indicates a high risk of short circuit within the battery; the larger the K value, the higher the risk of short circuit within the battery. When the ratio of silicon content A in the negative electrode active material layer to the elongation at break B of the negative electrode current collector is too small, the risk of battery short circuit increases. Comparative Examples 3-4, based on Comparative Examples 1-2, adjusted the silicon content in the negative electrode active material layer, demonstrating that when the silicon content A in the negative electrode active material layer meets the range of 1.5%-17.5%, the appropriate ratio can further improve the battery cycle performance.

[0125] Example 8

[0126] This embodiment provides a battery that is basically the same as that in Embodiment 1, except that the silicon content in the negative electrode active material layer, the negative electrode current collector and its elongation at break, and the elongation at break of the positive electrode current collector are different. In this embodiment, the negative electrode current collector includes a PET film and copper foil disposed on both sides of the PET film. The thickness of the PET film is 4.5 μm, and the thickness of the copper foil on one side is 1.0 μm. The manufacturer of the negative electrode current collector in this embodiment is Mianyang Maoyuan New Energy.

[0127] Example 9

[0128] This embodiment provides a battery that is basically the same as that in Embodiment 8, except that the negative electrode active material, the elongation at break of the negative electrode current collector, and the elongation at break of the positive electrode current collector are different. The preparation method of the negative electrode active material in this embodiment is the same as that in Embodiment 2, and the silicon content A in the negative electrode active material layer is shown in Table 3.

[0129] Example 10

[0130] This embodiment provides a battery that is basically the same as that in Embodiment 8, except that the negative electrode active material, the elongation at break of the negative electrode current collector, and the elongation at break of the positive electrode current collector are different. The preparation method of the negative electrode active material in this embodiment is the same as that in Embodiment 3, and the silicon content A in the negative electrode active material layer is shown in Table 3.

[0131] Examples 11-14

[0132] Examples 11-14 provide a battery that is basically the same as that in Example 8, except that the silicon content of the negative electrode active material layer, the elongation at break of the negative electrode current collector, and the elongation at break of the positive electrode current collector are different.

[0133] Comparative Examples 5-8

[0134] This comparative example provides a battery that is basically the same as that in Example 8, except that the silicon content of the negative electrode active material layer is different, the elongation at break of the negative electrode current collector is different, and the elongation at break of the positive electrode current collector is different.

[0135] The parameters of A, B, and D in Examples 8-14 and Comparative Examples 5-8 are shown in Table 3.

[0136] Table 3 Parameters of Examples 8-14 and Comparative Examples 5-8

[0137]

[0138] Table 4. Test results of Examples 8-14 and Comparative Examples 5-8

[0139]

[0140] Example 15

[0141] This embodiment provides a battery that is basically the same as that in Embodiment 1, except that the silicon content in the negative electrode active material layer is different, the elongation at break of the negative electrode current collector is different, and the positive electrode current collector and its elongation at break are different. In this embodiment, the positive electrode current collector includes a PP film and copper foil disposed on both sides of the PP film. The thickness of the PP film is 8.0 μm, and the thickness of the copper foil on one side is 1.2 μm.

[0142] Examples 16-21

[0143] Examples 16-21 provide a battery that is basically the same as that in Example 15, except that the silicon content in the negative electrode active material layer is different, the elongation at break of the negative electrode current collector is different, and the elongation at break of the positive electrode current collector is different.

[0144] Comparative Examples 9-12

[0145] This comparative example provides a battery that is basically the same as that in Example 15, except that the silicon content of the negative electrode active material layer is different, the elongation at break of the negative electrode current collector is different, and the elongation at break of the positive electrode current collector is different.

[0146] The parameters of A, B, and D in Examples 15-21 and Comparative Examples 9-12 are shown in Table 5, and the results are shown in Table 6.

[0147] Table 5. Parameters of Examples 15-21 and Comparative Examples 9-12

[0148]

[0149] Table 6. Test results of Examples 15-21 and Comparative Examples 9-12

[0150]

[0151]

[0152] Example 22

[0153] This embodiment provides a battery that is essentially the same as that in Embodiment 1, except that the silicon content in the negative electrode active material layer, the negative electrode current collector and its elongation at break, and the positive electrode current collector and its elongation at break are different. In this embodiment, the negative electrode current collector includes a PET film and copper foil disposed on both sides of the PET film. The thickness of the PET film is 4.5 μm, and the thickness of the copper foil on one side is 1.0 μm. In this embodiment, the positive electrode current collector includes a PP film and copper foil disposed on both sides of the PP film. The thickness of the PP film is 8 μm, and the thickness of the copper foil on one side is 1.2 μm.

[0154] Examples 23-28

[0155] Examples 23-28 provide a battery that is basically the same as that in Example 22, except that the silicon content in the negative electrode active material layer is different, the elongation at break of the negative electrode current collector is different, and the elongation at break of the positive electrode current collector is different.

[0156] Comparative Examples 13-16

[0157] This comparative example provides a battery that is basically the same as that in Example 22, except that the silicon content of the negative electrode active material layer is different, the elongation at break of the negative electrode current collector is different, and the elongation at break of the positive electrode current collector is different.

[0158] The parameters of A, B, and D in Examples 22-28 and Comparative Examples 13-16 are shown in Table 7, and the results are shown in Table 8.

[0159] Table 7 Parameters of Examples 22-28 and Comparative Examples 13-16

[0160]

[0161]

[0162] Table 8. Test results of Examples 22-28 and Comparative Examples 13-16

[0163]

[0164] Based on the above results, regardless of whether the negative electrode current collector or the positive electrode current collector is made of metal foil or a composite material (a composite of a substrate layer and a conductive layer), when the ratio of silicon content A in the negative electrode active material layer to the elongation at break D of the positive electrode current collector is 0.19-0.55, the cycle performance of the battery can be further improved, and problems such as electrode wrinkling and cracking of the positive electrode active material layer can be reduced. When the ratio of silicon content A in the negative electrode active material layer to the elongation at break B of the negative electrode current collector is too high or too low, the cycle performance of the battery will be significantly reduced, leading to electrode wrinkling, current collector breakage, and other problems, thus reducing the risk of short circuits. This invention, by controlling the silicon content A in the negative electrode active material layer to be 1.5%-17.5% or the elongation at break B of the negative electrode current collector to be 3-100%, can further improve the cycle performance and safety performance of the battery.

[0165] Examples 29-33

[0166] The embodiment provides a battery that is basically the same as that in embodiment 1, except that the silicon content in the negative electrode active material layer is different, the elongation at break of the negative electrode current collector is different, and the elongation at break of the positive electrode current collector is different, as shown in Table 9. The test results are shown in Table 10.

[0167] Table 9 Parameters of Examples 29-33

[0168]

[0169] Table 10 Test Results of Examples 29-33

[0170]

[0171] The results above show that when the negative electrode current collector is a metal foil, controlling the elongation at break of the negative electrode current collector to be between 5% and 15% helps to further improve the cycle performance of the battery and reduce problems such as cracking of the active material and breakage of the foil. Furthermore, when the negative electrode current collector is a metal foil, controlling the ratio of silicon content A in the negative electrode active material layer to the elongation at break B of the negative electrode current collector to be between 0.3 and 0.6 can improve cracking of the active material layer and battery cycle performance.

[0172] Examples 34-38

[0173] The embodiment provides a battery that is basically the same as that in embodiment 8, except that the silicon content in the negative electrode active material layer is different, the elongation at break of the negative electrode current collector is different, and the elongation at break of the positive electrode current collector is different, as shown in Table 11. The results are shown in Table 12.

[0174] Table 11 Parameters of Examples 34-38

[0175]

[0176]

[0177] Table 12 Test Results of Examples 34-38

[0178]

[0179] The results above show that when the negative electrode current collector is a composite foil, controlling the elongation at break of the negative electrode current collector to be between 10% and 80% helps to further improve the cycle performance of the battery and reduce problems such as cracking of the active material and breakage of the foil. Furthermore, when the negative electrode current collector is a composite foil, controlling the ratio of silicon content A in the negative electrode active material layer to the elongation at break B of the negative electrode current collector to be between 0.17 and 0.35 can improve cracking of the active material layer and battery cycle performance.

[0180] Examples 39-43

[0181] The embodiment provides a battery that is basically the same as that in embodiment 1, except that the silicon content in the negative electrode active material layer is different, the elongation at break of the negative electrode current collector is different, and the elongation at break of the positive electrode current collector is different, as shown in Table 13. The results are shown in Table 14.

[0182] Table 13 Parameters of Examples 39-43

[0183]

[0184] Table 14 Test Results of Examples 39-43

[0185]

[0186] The results show that when the positive electrode current collector is a metal foil, controlling the elongation at break of the positive electrode current collector to be between 5% and 15% helps to further improve the cycle performance of the battery and reduce problems such as cracking of the active material and breakage of the foil. When the positive electrode current collector is a metal foil, the ratio of silicon content A in the negative electrode active material layer to the elongation at break D of the positive electrode current collector being between 0.3 and 0.55 can improve the cracking of the active material layer and the cycle performance of the battery.

[0187] Examples 44-48

[0188] The embodiment provides a battery that is basically the same as that in embodiment 15, except that the silicon content in the negative electrode active material layer is different, the elongation at break of the negative electrode current collector is different, and the elongation at break of the positive electrode current collector is different, as shown in Table 15. The results are shown in Table 16.

[0189] Table 15 Parameters of Examples 44-48

[0190]

[0191] Table 16 Test Results of Examples 44-48

[0192]

[0193]

[0194] The results above show that when the positive electrode current collector is a composite foil, controlling the elongation at break of the positive electrode current collector to be between 10% and 80% helps to further improve the cycle performance of the battery and reduce problems such as cracking of the active material and breakage of the foil. When the positive electrode current collector is a composite foil, the ratio of silicon content A in the negative electrode active material layer to the elongation at break D of the positive electrode current collector is between 0.19 and 0.35, which can improve the cracking of the active material layer and the cycle performance of the battery.

[0195] Examples 49-52

[0196] The embodiment provides a battery that is basically the same as that in embodiment 1, except that the silicon content in the negative electrode active material layer is different, the elongation at break of the negative electrode current collector is different, and the elongation at break of the positive electrode current collector is different, as shown in Table 17. The results are shown in Table 18.

[0197] Table 17 Parameters of Examples 49-52

[0198]

[0199] Table 18 Test Results of Examples 49-52

[0200]

[0201] The results above show that when the negative electrode current collector is a metal foil, further adjusting the values ​​of A and B, when the silicon content A in the negative electrode active material layer and the elongation at break B of the negative electrode current collector meet the requirements of this invention, helps to improve battery cycle performance and reduce problems such as foil breakage and active material cracking. When the silicon content is below 1.5 wt%, it is detrimental to the contact between silicon particles and the carbon matrix, affecting the structural stability of the electrode and thus impacting cycle life.

[0202] Examples 53-56

[0203] The embodiment provides a battery that is basically the same as that in embodiment 8, except that the silicon content in the negative electrode active material layer is different, the elongation at break of the negative electrode current collector is different, and the elongation at break of the positive electrode current collector is different, as shown in Table 19 and the results are shown in Table 20.

[0204] Table 19 Parameters of Examples 53-56

[0205]

[0206] Table 20 Test Results of Examples 53-56

[0207]

[0208] The results above show that when the negative electrode current collector is a composite foil, further adjusting the values ​​of A and B, when the silicon content A in the negative electrode active material layer and the elongation at break B of the negative electrode current collector meet the requirements of this invention, helps to improve battery cycle performance and reduce problems such as foil breakage and active material cracking. When the silicon content is below 1.5 wt%, it is detrimental to the contact between silicon particles and the carbon matrix, affecting the structural stability of the electrode and thus impacting cycle life.

[0209] Examples 57-60

[0210] The embodiment provides a battery that is basically the same as that in embodiment 1, except that the silicon content in the negative electrode active material layer is different, the elongation at break of the negative electrode current collector is different, and the elongation at break of the positive electrode current collector is different, as shown in Table 21. The results are shown in Table 22.

[0211] Table 21 Parameters of Examples 57-60

[0212]

[0213] Table 22 Test Results of Examples 57-60

[0214]

[0215] The results above show that when the positive electrode current collector is a metal foil, and the silicon content A in the negative electrode active material layer and the elongation at break D of the positive electrode current collector meet the requirements of this invention, further adjusting the values ​​of A and D helps improve battery cycle performance and reduce problems such as foil breakage and active material cracking. When the silicon content is below 1.5 wt%, it is detrimental to the contact between silicon particles and the carbon matrix, affecting the structural stability of the electrode and thus impacting cycle life.

[0216] Examples 61-64

[0217] The embodiment provides a battery that is basically the same as that in embodiment 15, except that the silicon content in the negative electrode active material layer is different, the elongation at break of the negative electrode current collector is different, and the elongation at break of the positive electrode current collector is different, as shown in Table 23 and the results are shown in Table 24.

[0218] Table 23 Parameters of Examples 61-64

[0219]

[0220] Table 24 Test Results of Examples 61-64

[0221]

[0222] The results above show that when the positive electrode current collector is a composite foil, and the silicon content A in the negative electrode active material layer and the elongation at break D of the positive electrode current collector meet the requirements of this invention, further adjusting the values ​​of A and D helps improve battery cycle performance and reduce problems such as foil breakage and active material cracking. When the silicon content is below 1.5 wt%, it is detrimental to the contact between silicon particles and the carbon matrix, affecting the structural stability of the electrode and thus impacting cycle life.

[0223] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A battery, the battery comprising a negative electrode sheet, the negative electrode sheet comprising a current collector and a negative electrode active material layer disposed on at least one surface of the current collector, characterized in that, The negative electrode active material layer includes a negative electrode active material, which includes a silicon-containing material; the silicon content in the negative electrode active material layer and the elongation at break of the negative electrode current collector satisfy the following relationship: Wherein, A represents the elemental silicon content in the negative electrode active material layer, in wt%; B represents the elongation at break of the negative electrode current collector, expressed in % (%). The battery includes a positive electrode sheet, which comprises a positive current collector and a positive active material layer. The positive current collector is a metal foil. The silicon content in the negative active material layer and the elongation at break of the positive current collector satisfy the following relationship: Wherein, D is the elongation at break of the positive electrode current collector, in percentage (%). The range of D is 5% to 15%; The difference between the elongation at break B of the negative electrode current collector and the elongation at break D of the positive electrode current collector is 1% to 3%.

2. The battery according to claim 1, characterized in that, The range of A is 1.5wt% to 17.5wt%; and / or the range of B is 3% to 100%.

3. The battery according to claim 1, characterized in that, The negative electrode current collector includes at least a first conductive layer and a first polymer substrate layer; the first polymer substrate layer is disposed between two adjacent first conductive layers; The silicon content in the negative electrode active material layer and the elongation at break of the negative electrode current collector satisfy the following relationship: 。 4. The battery according to claim 3, characterized in that, The range of B is 10% to 80%.

5. The battery according to claim 1, characterized in that, The negative electrode current collector is a metal foil, and the silicon content in the negative electrode active material layer and the elongation at break of the negative electrode current collector satisfy the following relationship: 。 6. The battery according to claim 5, characterized in that, The range of B is 5% to 15%.

7. An apparatus, characterized in that, Includes the battery as described in any one of claims 1 to 6.

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