Battery and device

Abstract

The invention belongs to the technical field of battery preparation, and particularly relates to a battery and a device. The battery comprises a negative pole piece and a positive pole piece, the negative pole piece comprises a negative current collector and a negative active material layer arranged on at least one surface of the negative current collector, the negative active material layer comprises a negative active material, and the negative 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 meet a specific relational expression, and the positive electrode plate comprises a positive electrode current collector; the silicon content in the negative electrode active material layer and the elongation at break of the positive electrode current collector meet a specific relational expression, so that the risk of negative electrode foil cracking caused by negative electrode expansion can be reduced while the lithium ion embedding capacity of the negative electrode is ensured, the risk of positive and negative electrode short circuit caused by the negative electrode foil breaking process can be avoided, and the service life of the negative electrode is prolonged. And the capacity density, the cycle performance and the safety performance of the battery are improved.

Description

[0001] This application is a divisional application of the invention patent application with publication number CN 119994048A. The application date of the original application is: 2025.02.20; the application number is: 202510189537.5; the name of the invention is: "A battery and device". Technical Field

[0002] The present invention belongs to the technical field of battery preparation, and in particular relates to a battery and a device. Background Art

[0003] Lithium-ion batteries, with their advantages of high energy density, long cycle life, low self-discharge, and lack of memory effect, hold broad application prospects in the new energy sector. With the advancement 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 also becoming increasingly prominent. Especially when silicon is incorporated into the negative electrode, balancing battery energy density, safety, and cycle performance remains a technical challenge for those skilled in the art. Summary of the Invention

[0004] The purpose of the present invention is to overcome the deficiencies of the prior art and provide a battery and a device that can ensure that the battery has good energy density, good cycle performance and safety.

[0005] To this end, the present invention provides the following technical solutions.

[0006] A first aspect of the present invention provides a battery, comprising a negative electrode plate, the negative electrode plate 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:

[0007]

[0008] Wherein, A is the elemental silicon content in the negative electrode active material layer, in wt%;

[0009] B is the elongation at break of the negative electrode current collector, in %.

[0010] As an optional embodiment, the range of A is 1.5 wt% to 17.5 wt%; and / or the range of B is 3% to 100%.

[0011] As an optional embodiment, the negative electrode current collector comprises 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;

[0012] 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:

[0013]

[0014] As an optional implementation manner, the range of B is 10% to 80%.

[0015] As an optional embodiment, 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:

[0016]

[0017] As an optional implementation manner, the range of B is 5% to 15%.

[0018] As an optional embodiment, 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:

[0019]

[0020] Wherein, D is the elongation at break of the positive electrode current collector, in %.

[0021] As an optional implementation, the range of D is 3% to 90%.

[0022] As an optional embodiment, the positive electrode current collector includes a second conductive layer and a second polymer substrate layer, and the second polymer substrate layer is provided 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:

[0023]

[0024] As an optional implementation manner, the range of D is 10% to 80%.

[0025] As an optional embodiment, 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:

[0026]

[0027] As an optional implementation, the range of D is 5% to 15%.

[0028] As an optional embodiment, 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%.

[0029] A second aspect of the present invention provides a device comprising the above-mentioned battery.

[0030] The beneficial effects of the present invention are:

[0031] The present invention provides a battery. By controlling the silicon content and the elongation at break of the negative electrode within appropriate ranges, the present invention can not only ensure the lithium ion embedding capacity of the negative electrode while reducing the risk of cracking of the negative electrode foil due to expansion of the negative electrode, but also avoid the risk of short circuit between the positive and negative electrodes due to the fracture of the negative electrode foil, thereby improving the battery capacity density, cycle performance and safety performance. DETAILED DESCRIPTION

[0032] The following examples are provided for a better understanding of the present invention and are not intended to limit the best mode of implementation. They do not limit the content and scope of protection of the present invention. Any product identical or similar to the present invention obtained by anyone under the guidance of the present invention or by combining the features of the present invention with other prior arts shall fall within the scope of protection of the present invention.

[0033] If no specific experimental steps or conditions are specified in the examples, the conventional experimental steps or conditions described in the literature in this field can be used. If the manufacturer of the reagents or instruments is not specified, they are all commercially available conventional reagents.

[0034] An embodiment of the present invention provides a battery, comprising a negative electrode plate, the negative electrode plate 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:

[0035]

[0036] Wherein, A is the elemental silicon content in the negative electrode active material layer, in wt%;

[0037] B is the elongation at break of the negative electrode current collector, in %.

[0038] In the present invention, when the ratio of A to B meets the above range, the energy density of the entire battery can be improved, the lithium ion embedding capacity of the negative electrode can be guaranteed, and the electrode piece fracture caused by silicon expansion can be prevented, thereby avoiding the risk of positive and negative electrode short circuit caused by the negative electrode fracture process, thereby improving the battery capacity density, cycle performance and safety performance. When the ratio of A to B does not meet the above range, the electrode piece will be unable to withstand the expansion of silicon, causing the electrode piece to fracture and the risk of short circuit. In addition, when the ratio of A to B does not meet the above range, it will also cause the active material layer on the electrode surface to crack easily, thereby affecting the battery life.

[0039] In the present 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 the charging process, silicon undergoes an alloying reaction, and after lithium insertion, the volume changes by up to 300%. As the silicon content increases, the expansion increases. The larger the silicon grains, the greater the relative expansion. When A meets the above range, it can not only improve the ability of the negative electrode sheet to insert lithium and the number of lithium ions inserted, thereby increasing the capacity of the battery, but also prevent excessive silicon content from causing excessive silicon expansion during charging, thereby damaging the electrode sheet, causing the foil to break, and thus affecting the battery life. When the B value is within the above range, it can not only enable the negative electrode foil to adapt to the expansion of silicon particles and prevent the occurrence of cracking of the negative electrode foil, but also avoid the phenomenon of short circuit caused by the negative electrode foil overlapping with the shell or the positive electrode sheet due to excessive elongation at break of the negative electrode foil, thereby improving the safety performance of the battery. Therefore, controlling B within the above range can reduce belt breakage during processing and improve production efficiency.

[0040] In the present 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 provided 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:

[0041]

[0042] 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 an ordinary current collector, and it is not easy to tear when stretched, which can reduce the probability of demolding and breaking of the negative electrode sheet. Furthermore, when the negative electrode current collector includes a polymer substrate layer, when A and B meet the above ranges, the battery energy density and battery safety performance can be further improved. The material of the first polymer substrate layer includes polymers such as PET (polyethylene terephthalate), PP (polypropylene), and PI (polyimide), and the thickness of the polymer substrate layer is 4 to 15 μm; the first conductive layer is copper, and the thickness of the conductive layer is 0.8 to 5 μm.

[0043] In the present invention, when the negative electrode current collector includes a conductive layer and a polymer substrate layer, the range of B is 10% to 80%, and the negative electrode current collector is a composite foil. 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.

[0044] In the present 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:

[0045]

[0046] 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 satisfying the above ranges can further improve the battery energy density, cycle performance and safety performance.

[0047] The range of B is 5% to 15%. The negative electrode current collector is a metal foil. When the metal foil is within a suitable range, the internal resistance of the battery can be reduced, while the energy density of the battery can be increased. The current capacity of the foil can also be guaranteed, thereby ensuring the safety performance of the battery.

[0048] In the present 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:

[0049]

[0050] Wherein, D is the elongation at break of the positive electrode current collector, in %.

[0051] After winding or stacking, the battery undergoes a hot pressing process. During hot pressing, some of the binder components in the positive and negative active material layers melt, resulting in a certain degree of adhesion between the positive and negative electrodes and the separator. Alternatively, the industry currently uses sticky separators with a sticky surface to further enhance the bonding strength between the positive and negative electrodes and the separator. Therefore, when there is a certain degree of bonding strength between the positive and negative electrodes and the separator, when the surface active material of the negative electrode expands, the negative electrode expands, which in turn causes the separator, which has greater ductility, to expand as well. The separator further transfers the tension to the positive electrode. If the elongation at break D of the positive current collector is small, the expansion of the negative active material may cause the negative electrode to expand, leading to the positive electrode being torn and the positive active material being separated from the positive current collector. Therefore, the present invention controls 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 ranges, which can reduce the situations where the positive electrode sheet is pulled apart, the positive electrode active material is demolded from the positive electrode current collector, and the active material layer cracks.

[0052] In the present invention, the range of D is 3% to 90%. The present 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.

[0053] In the present invention, the positive electrode current collector includes a second conductive layer and a second polymer substrate layer, and the second polymer substrate layer is provided 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:

[0054]

[0055] The present invention introduces a conductive layer and a polymer substrate layer into the positive electrode current collector, which can further reduce the situation where the pole piece is pulled apart and the positive electrode active material is demolded, and can also improve the safety performance of the battery and at the same time increase the energy density of the battery.

[0056] In the present 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 preparation efficiency and yield rate of the battery cell.

[0057] In the present 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:

[0058]

[0059] In the present invention, the positive electrode current collector is made of metal foil, 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, which can further reduce the demoulding of the positive electrode active material, the breakage of the electrode piece, etc., further reduce the accidental contact of the positive and negative electrode pieces, and improve the safety performance of the battery.

[0060] In the present 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.

[0061] In the present 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 fall within this range, the DCR is low, the negative electrode active material layer and the positive electrode active material layer are well matched, the risk of negative electrode lithium plating is reduced, and the cycle capacity retention rate is increased.

[0062] The present invention adopts conventional methods in the art to prepare the above-mentioned battery. For example, it includes the following steps:

[0063] (1) Preparation of negative electrode sheet

[0064] The negative electrode active material is mixed with additives and a solvent is added to produce a negative electrode slurry. The negative electrode slurry is then coated on at least one surface of the negative electrode current collector, dried, cold pressed, and cut into pieces to produce negative electrode sheets. Additives include conductive agents, binders, thickeners, and the like.

[0065] The negative electrode active material, conductive agent, binder and thickener are made of common materials in this field. As an example, the conductive agent is one or more of acetylene black, SWCNT, etc.; the thickener is CMC, etc.; the binder is SBR, etc. The negative electrode active material includes a silicon-containing material, and the silicon-containing material is at least one of a nano-silicon-carbon composite negative electrode material and a silicon oxide negative electrode material; wherein the silicon oxide negative electrode material can also be a pre-magnesiumized or pre-lithiated silicon oxide negative electrode material. The present invention does not make specific restrictions on the preparation method of the silicon-containing material. Those skilled in the art can select all silicon-containing materials prepared by the existing technology according to their needs. Here are several preparation methods of silicon-containing materials:

[0066] Preparation method of silicon-carbon composite negative electrode material by gas phase method

[0067] Porous carbon materials as carbon matrix (porous carbon type: pore size 4-5nm, specific surface area range of 900-1800m 2 / g), add it into a rotary kiln, introduce nitrogen to remove oxygen, and heat and roast it. The nitrogen flow rate, roasting temperature and heating rate, and rotary kiln speed are common parameters in this field. For example, the nitrogen flow rate can be set to 8-25 L / min, the roasting heating rate can be 10-30 ° C / min, the temperature is 500-800 ° C, and the rotary kiln speed is 100-300 rpm. Keeping the roasting temperature unchanged, introduce a mixed gas, which includes nitrogen and silane (such as monosilane) in a volume ratio of 1: (1-7), and the flow rate of the mixed gas is 0.1-0.2 L / min. Specifically: pass it at a flow rate of 0.1-0.2 L / min for 8 hours, then pass it at a flow rate of 0.2-0.4 L / min for 8 hours, and then pass it at a flow rate of 0.1-0.2 L / min for 8 hours. After the reaction is completed, stop introducing silane gas and only introduce nitrogen. The product is calcined in a nitrogen atmosphere at a calcination temperature of 500-600°C and a heating rate of 10-20°C / min. When the temperature stabilizes, acetylene gas is introduced at a rate of 0.8-2.5 L / min for reaction. After continuous introduction for 5-12 hours, the acetylene gas is turned off and the product is naturally cooled under a nitrogen atmosphere. After the temperature is completely reduced to room temperature, the material is taken out for crushing, screening, and demagnetization to obtain a silicon-carbon composite negative electrode material.

[0068] Preparation method of silicon 2 oxide negative electrode material

[0069] Precursor preparation: Silica powder and silicon powder are uniformly mixed in a VC mixer at a molar ratio of 1:0.5-3. The uniformly mixed powder is subjected to high-temperature vacuum treatment in a vacuum atmosphere furnace sample chamber; wherein the temperature range of the high-temperature vacuum treatment is 600-1800°C. The material after high-temperature vacuum treatment is subjected to air flow pulverization and then passed through a dust removal device to obtain a precursor powder with fine powder removed. Precursor coating: The above-mentioned precursor powder with fine powder removed is placed in a continuous rotary kiln, and a mixed gas is introduced into the rotary kiln, wherein the mixed gas includes argon and acetylene in a volume ratio of 1:1 and the mixed gas is introduced at a rate of 0.2-1.5L / min. After continuous introduction for 20-60 minutes, the air in the furnace tube is exhausted, and then the temperature is increased to 700-800°C at a heating rate of 5-10°C / min and calcined for 1-4 hours to obtain a silicon dioxide negative electrode material.

[0070] Preparation method of silicon-carbon composite material by sand grinding

[0071] Silicon powder with a particle size of 1 to 20 μm and graphite are mixed in an organic solvent in a mass ratio of 1:1 to 5, and the mixed mixture is ball-milled in a ball mill at a speed of 300 to 700 rpm to obtain a precursor powder; asphalt and the precursor powder are mixed in a mass ratio of 1:2 to 4, and sintered in a nitrogen atmosphere at a temperature of 500 to 1200°C for 4 to 10 hours, and then naturally cooled to room temperature to obtain a silicon-carbon composite material.

[0072] The mass ratio of the negative electrode active material, the conductive agent, the thickener and the binder adopts the conventional ratio in the art. As an example, the mass ratio of the silicon-carbon composite material, the conductive agent and the binder is (96-98.5):(1.0-2.5):(0.5-1.5).

[0073] The current collector can be a composite current collector or a metal foil. For example, the composite current collector includes a conductive layer and a polymer substrate layer, with the polymer substrate layer disposed between two 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.

[0074] (2) Preparation of positive electrode sheet

[0075] The positive electrode active material and additives are mixed and a solvent is added to produce a positive electrode slurry. The positive electrode slurry is then coated on at least one surface of a positive electrode current collector, dried, cold pressed, and cut into pieces to produce positive electrode sheets. Additives include conductive agents, binders, and the like.

[0076] The positive electrode active material, conductive agent, and binder are made of common materials in this field. As an 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, and the ternary positive electrode active material can be but is not limited to CM523, NCM622, and NCM811. The type and amount of positive electrode active material, conductive agent, binder, and solvent can be selected according to needs in this field. Exemplarily, the mass ratio of positive electrode active material, conductive agent, and binder is (96~98.2):(1~2):(0.8~2).

[0077] The current collector can be a composite current collector or a metal foil. For example, the composite current collector includes a conductive layer and a polymer substrate layer, with the polymer substrate layer disposed between two 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.

[0078] (3) Electrolyte

[0079] The electrolyte of the present invention can be any electrolyte suitable for electrochemical energy storage devices in the art, and the electrolyte includes an electrolyte and a solvent, and the electrolyte generally includes a lithium salt. The concentration of the lithium salt in the electrolyte is 0.5 to 2.5 mol / L.

[0080] Conventional lithium salts in the art are used as examples. The lithium salt is at least one of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalatoborate (LiDFOB), lithium dioxalatoborate (LiBOB), lithium difluorophosphate (LiPO2F2), lithium difluorobis(oxalatophosphate) (LiDFOP), and lithium tetrafluorooxalatophosphate (LiTFOP).

[0081] 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)), carboxylic acid esters (methyl propionate (EP)), etc.

[0082] (4) Diaphragm

[0083] The separator is disposed between the positive and negative electrodes to separate them and prevent short circuits. The present invention does not specify the manufacturer, preparation process, or type of separator. For example, the separator can be PE (polyethylene) or PP (polypropylene).

[0084] (5) The positive electrode sheet, separator, and negative electrode sheet are stacked in order and wound to obtain a bare cell; the bare cell is placed in an outer packaging shell, dried, injected with electrolyte, and packaged, allowed to stand, and formed to obtain a lithium-ion battery.

[0085] An embodiment of the present invention further provides a device comprising the aforementioned battery. This device refers to any device that can utilize electrical energy and convert it into one or more other forms of energy, such as mechanical energy, thermal energy, or light energy, such as an electric motor, an electric heat generator, or an electric light source. Examples include, but are not limited to, electric vehicles, electric trains, ships, and mobile phones.

[0086] The present invention is further described below with specific embodiments:

[0087] In the following examples and comparative examples, the silicon content A in the negative electrode active material layer, the elongation at break of the current collector, and the battery performance were measured and obtained using the following methods.

[0088] (1) Testing method for silicon content in negative electrode active material layer:

[0089] The disassembled negative electrode piece was immersed in a container filled with DMC. The negative electrode piece after soaking for 8 hours was placed in a 45°C oven and baked for 30 minutes to remove the residual solvent to obtain the treated piece. The silicon content was tested by cross-section polishing-scanning electron microscopy. The treated negative electrode piece was cross-sectioned and polished using an argon ion beam. The same sample was cut at 4 locations, and each cut surface was scanned by SEM. Four fields of view were selected for surface scanning at 500x magnification. The average value of all silicon element content values ​​obtained from the surface scans of 16 fields of view of the four cut surfaces was taken as the most accurate conclusion, that is, the silicon content in the negative electrode active material layer. The silicon content in the negative electrode active material layer refers to the proportion of silicon element in the mass of all substances in the negative electrode active material layer.

[0090] (2) Test method for elongation at break of current collector:

[0091] Disassemble the battery to obtain the electrode. Soak the disassembled electrode in a container filled with deionized water and ultrasonically clean it for 30 minutes to remove the active material on the current collector surface. Bake the soaked electrode in a 45°C oven for 10 minutes to remove any residual moisture. Use a diaphragm slitting machine to cut 150 mm long and 15 mm wide strips of specimens. The initial gauge length between the fixtures is 100 mm, and the tensile speed is (100 ± 10) mm / min. Apply a static tensile load uniformly along the axial direction of the foil until the foil breaks. The elongation at break is measured and divided by the gauge length to obtain the elongation at break. This test method can be used to determine the elongation at break for both positive and negative current collectors.

[0092] (3) Electrochemical performance test method:

[0093] Cycling performance test method: At 25°C, the lithium-ion batteries prepared in the examples and comparative examples were subjected to a cycling test according to the following procedure: charging at a rate of 1 / 3C to 4.25V and then discharging at a rate of 1 / 3C to 2.5V, and this cycle was repeated until the capacity of the lithium-ion battery was less than 80% of the initial capacity. The number of cycles at this time was recorded.

[0094] (4) Integrity test of battery positive and negative electrodes

[0095] At 25°C, the lithium-ion batteries prepared in the examples and comparative examples were subjected to a cycle test according to the following procedure: charging at a rate of 1 / 3C to 4.25V; then discharging at 1 / 3C to 2.5V. After 500 cycles, the lithium-ion batteries obtained in the examples and comparative examples were disassembled to observe the integrity of the positive and negative electrodes.

[0096] (5) Self-discharge value test

[0097] At 25°C, first charge to 4.25V at a rate of 1 / 3C, let it stand for 10 minutes, discharge to 2.5V at a rate of 1 / 3C, let it stand for 10 minutes, and repeat this cycle for 100 times. Then charge to 4.25V at a rate of 1 / 3C and let it stand for 30 minutes. Measure the open circuit voltage at this time, record it as OCV1, and continue to stand for 2 days. Record the open circuit voltage at this time, record it as OCV2, and calculate the voltage change and voltage drop (K value) according to the formula; the K value calculation formula is as follows:

[0098]

[0099] Example 1

[0100] This embodiment provides a battery, and the preparation method thereof includes:

[0101] (1) Preparation of negative electrode sheet

[0102] The porous carbon material is used as the carbon matrix (porous carbon type: pore size 4-5nm, specific surface area range 900-1800m 2 / g), added to a rotary kiln, nitrogen was introduced to remove oxygen, and the flow rate was set to 10 L / min. After the oxygen removal was completed, the temperature was raised and calcined, the calcination temperature was 500 ° C, the heating rate was 10 ° C / min, the rotation speed was 100 rpm, and the temperature was kept constant. A mixed gas of nitrogen and monosilane with a volume ratio of 1: 4 was introduced, and the mixed gas was first ventilated at a flow rate of 0.15 L / min for 8 h, then ventilated at a flow rate of 0.3 L / min for 8 h, and finally ventilated at a flow rate of 0.2 L / min for 8 h. After the reaction was completed, the silane gas was turned off and calcined under a nitrogen atmosphere, the calcination temperature was 550 ° C, the heating rate was 10 ° C / min, and when the temperature was stable, acetylene gas was introduced with a flow rate of 1 L / min. The acetylene gas was turned off after the temperature was kept constant and ventilation was continued for 10 h. The temperature was naturally lowered under a nitrogen atmosphere. After cooling was complete, the material was taken out and crushed, sieved, and demagnetized to obtain a silicon-carbon composite material.

[0103] The carbon-coated silicon-carbon composite material and the conductive agent, acetylene black, and binder, SBR, were mixed in a mass ratio of 97:1.5:1.5. Deionized water was added as a solvent and stirred in a vacuum mixer to obtain a negative electrode slurry. The negative electrode slurry was evenly coated on both surfaces of the negative electrode current collector copper foil, dried at room temperature, and then transferred to an oven for further drying. The negative electrode sheets were then cold pressed and slit. The elongation at break of the copper foil is shown in Table 1.

[0104] (2) Preparation of positive electrode sheet

[0105] The positive electrode active material NCM811, the conductive agent acetylene black, and the binder PVDF were mixed in a mass ratio of 96:2:2. The solvent NMP was added and stirred in a vacuum mixer to obtain a positive electrode slurry. The positive electrode slurry was then coated on both surfaces of the positive electrode current collector aluminum foil, dried at room temperature, and then transferred to an oven for further drying. The positive electrode sheets were then cold pressed and slit. The elongation at break of the aluminum foil is shown in Table 1.

[0106] (3) Electrolyte

[0107] Ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) are mixed in a volume ratio of 1:1:1 to obtain an organic solvent. Then, fully dried lithium salt LiPF6 is dissolved in the mixed organic solvent to prepare an electrolyte with a lithium salt concentration of 1 mol / L.

[0108] (4) Diaphragm

[0109] Polyvinyl alcohol was used as the separator.

[0110] (5) Stacking the positive electrode sheet, isolation film, and negative electrode sheet in order, placing the isolation film between the positive and negative electrode sheets to play an isolating role, and then winding to obtain a bare battery cell; placing the bare battery cell in an outer packaging shell, injecting electrolyte after drying, and vacuum packaging, standing, and forming to obtain a lithium-ion battery.

[0111] Example 2

[0112] This embodiment provides a battery that is substantially the same as that of Example 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 elongations at break of the negative and positive electrode current collectors are shown in Table 1. The negative electrode active material of this embodiment is a silicon oxide negative electrode material, and its preparation method comprises: uniformly mixing silicon dioxide powder and silicon powder at a molar ratio of 1:2 in a VC mixer, subjecting the uniformly mixed powder to a high-temperature vacuum treatment in a sample chamber of a vacuum furnace at 1650°C, pulverizing the high-temperature treated material in a jet mill, and passing the resulting material through a dust removal device to obtain a precursor powder from which fine powder has been removed. The above-mentioned precursor powder was placed in a continuous rotary kiln, and a mixed gas of inert gas argon and acetylene was introduced into the rotary kiln. The volume ratio of argon and acetylene gas was 1:1, the introduction rate of the mixed gas was 1L / min, the ventilation time was 30min, and the air in the furnace tube was discharged. Then, the powder was calcined at 750°C for 2h with a heating rate of 5°C / min. After the temperature dropped to room temperature, the sample was taken out to obtain a silicon oxide negative electrode material.

[0113] Example 3

[0114] This embodiment provides a battery that is substantially the same as Example 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 elongations at break of the negative and positive electrode current collectors are shown in Table 1. The negative electrode active material of this embodiment is a carbon-silicon composite negative electrode material, and its preparation method comprises: mixing silicon powder with a particle size of 3 to 5 μm and graphite in an organic solvent in a mass ratio of 1:3, and ball milling the mixture in a ball mill at a speed of 500 rpm to obtain a precursor powder; and mixing asphalt with the precursor powder in a mass ratio of 1:3, placing the mixture in a nitrogen atmosphere, sintering the mixture at 800°C for 8 hours, and then naturally cooling the mixture to room temperature to obtain a silicon-carbon composite material.

[0115] Examples 4-7

[0116] Examples 4-7 provide a battery that is substantially the same as Example 1, except that the silicon content in 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.

[0117] Comparative Examples 1-4

[0118] This comparative example provides a battery that is substantially the same as 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.

[0119] The silicon content A, the elongation at break B of the negative electrode current collector, and the elongation at break D of the positive electrode current collector of Examples 1-7 and Comparative Examples 1-4 are shown in Table 1, and the test results are shown in Table 2.

[0120] Table 1 Parameters of Examples 1-7 and Comparative Examples 1-4

[0121]

[0122]

[0123] Table 2 Test results of Examples 1-7 and Comparative Examples 1-4

[0124]

[0125] From the above results, it can be seen, in conjunction with Examples 6-7, that the present invention, based on the ratio of the silicon content A of the negative electrode active material layer to the elongation at break B of the negative electrode current collector being 0.17-0.6, further regulating the silicon content A of the negative electrode active material layer and the elongation at break D of the positive electrode current collector to meet the requirements of 0.19-0.55, can further improve battery cycle performance and reduce problems such as wrinkling of the positive electrode sheet and cracking of the material layer. Furthermore, in conjunction with Comparative Examples 1-2, when the ratio of the silicon content A of 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 breakage of the foil will occur, and the battery cycle performance will be significantly reduced. The K value is an indicator for evaluating the short circuit risk of the battery. A K value exceeding 0.045 indicates a high risk of internal short circuit in the battery. The larger the K value, the higher the risk of internal short circuit in the battery. When the ratio of the silicon content A of 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 is increased. Comparative Examples 3-4 adjust the silicon content in the negative electrode active material layer based on Comparative Examples 1-2, indicating that when the silicon content A in the negative electrode active material layer satisfies 1.5%-17.5%, the appropriate ratio can further improve the battery cycle performance.

[0126] Example 8

[0127] This embodiment provides a battery that is substantially the same as that of Example 1, except that the silicon content in the negative electrode active material layer, the negative electrode current collector and its elongation at break are different, and the positive electrode current collector has a different elongation at break. The negative electrode current collector of this embodiment comprises a PET film and copper foil disposed on both sides of the PET film. The PET film is 4.5 μm thick, and the copper foil on one side is 1.0 μm thick. The negative electrode current collector of this embodiment is manufactured by Mianyang Maoyuan New Energy.

[0128] Example 9

[0129] This embodiment provides a battery that is substantially the same as that of Example 8, differing in 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. The preparation method for the negative electrode active material of this embodiment is the same as that of Example 2. The silicon content A in the negative electrode active material layer is shown in Table 3.

[0130] Example 10

[0131] This embodiment provides a battery that is substantially the same as that of Example 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 of Example 3. The silicon content A in the negative electrode active material layer is shown in Table 3.

[0132] Examples 11-14

[0133] Examples 11-14 provide a battery that is substantially the same as 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.

[0134] Comparative Examples 5-8

[0135] This comparative example provides a battery that is substantially the same as 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.

[0136] The parameters of A, B and D of Examples 8-14 and Comparative Examples 5-8 are shown in Table 3.

[0137] Table 3 Parameters of Examples 8-14 and Comparative Examples 5-8

[0138]

[0139] Table 4 Test results of Examples 8-14 and Comparative Examples 5-8

[0140]

[0141] Example 15

[0142] This embodiment provides a battery that is essentially the same as Example 1, differing in the silicon content of the negative electrode active material layer, the elongation at break of the negative electrode current collector, and the positive electrode current collector and its elongation at break. The positive electrode current collector in this embodiment comprises a polypropylene film and copper foil disposed on both sides of the PP film. The PP film is 8.0 μm thick, and the copper foil on one side is 1.2 μm thick.

[0143] Examples 16-21

[0144] Examples 16-21 provide a battery that is substantially the same as Example 15, except that the silicon content in 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.

[0145] Comparative Examples 9-12

[0146] This comparative example provides a battery that is basically the same as 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.

[0147] The parameters of A, B and D of Examples 15-21 and Comparative Examples 9-12 are shown in Table 5, and the results are shown in Table 6.

[0148] Table 5 Parameters of Examples 15-21 and Comparative Examples 9-12

[0149]

[0150] Table 6 Test results of Examples 15-21 and Comparative Examples 9-12

[0151]

[0152]

[0153] Example 22

[0154] This embodiment provides a battery that is essentially the same as Example 1, differing in the silicon content of 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. The negative electrode current collector in this embodiment comprises a PET film and copper foil disposed on both sides of the PET film. The PET film is 4.5 μm thick, and the copper foil on one side is 1.0 μm thick. The positive electrode current collector in this embodiment comprises a PP film and copper foil disposed on both sides of the PP film. The PP film is 8 μm thick, and the copper foil on one side is 1.2 μm thick.

[0155] Examples 23-28

[0156] Examples 23-28 provide a battery that is substantially the same as Example 22, except that the silicon content in 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.

[0157] Comparative Examples 13-16

[0158] This comparative example provides a battery that is basically the same as 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.

[0159] The parameters of A, B and D of Examples 22-28 and Comparative Examples 13-16 are shown in Table 7, and the results are shown in Table 8.

[0160] Table 7 Parameters of Examples 22-28 and Comparative Examples 13-16

[0161]

[0162]

[0163] Table 8 Test results of Examples 22-28 and Comparative Examples 13-16

[0164]

[0165] From the above results, no matter the negative electrode current collector or the positive electrode current collector is a metal foil or a composite material (a composite of a substrate layer and a conductive layer), when the ratio of the silicon content A in the negative electrode active material layer to the elongation at break D of the positive electrode current collector meets 0.19-0.55, the cycle performance of the battery can be further improved, and problems such as wrinkles on the electrode sheet and cracking of the positive electrode active material layer can be reduced. When the ratio of the 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, the cycle performance of the battery will be significantly reduced, and problems such as wrinkles on the electrode sheet and fracture of the current collector will occur, thereby reducing the risk of battery short circuit. The present invention regulates the silicon content A in the negative electrode active material layer to meet 1.5%-17.5% or the elongation at break B of the negative electrode current collector to meet 3-100%, which can further improve the cycle performance and safety performance of the battery.

[0166] Examples 29-33

[0167] The embodiment provides a battery that is basically the same as the 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, see Table 9, and the test results are shown in Table 10.

[0168] Table 9 Parameters of Examples 29-33

[0169]

[0170] Table 10 Test results of Examples 29-33

[0171]

[0172] The above results show that when the negative electrode current collector is a metal foil, regulating the elongation at break of the negative electrode current collector to 5%-15% can help further improve the battery's cycling performance and reduce problems such as cracking of the active material and foil breakage. Furthermore, when the negative electrode current collector is a metal foil, regulating the ratio of the silicon content A in the negative electrode active material layer to the elongation at break of the negative electrode current collector to 0.3-0.6 can also improve active material layer cracking and battery cycling performance.

[0173] Examples 34-38

[0174] The embodiment provides a battery that is basically the same as 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, see Table 11, and the results are shown in Table 12.

[0175] Table 11 Parameters of Examples 34-38

[0176]

[0177]

[0178] Table 12 Test results of Examples 34-38

[0179]

[0180] The above results show that when the negative electrode current collector is a composite foil, regulating the elongation at break of the negative electrode current collector to 10%-80% can help further improve the battery's cycling performance and reduce problems such as active material cracking and foil breakage. Furthermore, when the negative electrode current collector is a composite foil, regulating the ratio of the silicon content A in the negative electrode active material layer to the elongation at break B of the negative electrode current collector to 0.17-0.35 can also improve active material layer cracking and battery cycling performance.

[0181] Examples 39-43

[0182] The embodiment provides a battery that is basically the same as the 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, see Table 13, and the results are shown in Table 14.

[0183] Table 13 Parameters of Examples 39-43

[0184]

[0185] Table 14 Test results of Examples 39-43

[0186]

[0187] The above results show that when the positive electrode current collector is a metal foil, regulating the elongation at break of the positive electrode current collector to 5%-15% can help further improve the battery's cycling performance and reduce problems such as active material cracking and foil breakage. When the positive electrode current collector is a metal foil, a ratio of the silicon content A in the negative electrode active material layer to the elongation at break D of the positive electrode current collector of 0.3-0.55 can improve active material layer cracking and battery cycling performance.

[0188] Examples 44-48

[0189] The embodiment provides a battery that is basically the same as 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, see Table 15, and the results are shown in Table 16.

[0190] Table 15 Parameters of Examples 44-48

[0191]

[0192] Table 16 Test results of Examples 44-48

[0193]

[0194]

[0195] The above results show that when the positive electrode current collector is a composite foil, regulating the elongation at break of the positive electrode current collector to 10%-80% can help further improve the battery's cycling performance and reduce problems such as active material cracking and foil breakage. When the positive electrode current collector is a composite foil, a ratio of the silicon content A in the negative electrode active material layer to the elongation at break D of the positive electrode current collector of 0.19-0.35 can improve active material layer cracking and battery cycling performance.

[0196] Examples 49-52

[0197] The embodiment provides a battery that is basically the same as 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, see Table 17, and the results are shown in Table 18.

[0198] Table 17 Parameters of Examples 49-52

[0199]

[0200] Table 18 Test results of Examples 49-52

[0201]

[0202] The above results demonstrate that when the negative electrode current collector is a metal foil, further adjusting the values ​​of A and B, provided the silicon content A in the negative electrode active material layer and the elongation at break B meet the ranges of the present invention, can help improve battery cycle performance and reduce issues such as foil breakage and active material cracking. Silicon contents below 1.5 wt% are detrimental to contact between silicon particles and the carbon matrix, affecting the structural stability of the electrode and, consequently, the cycle life.

[0203] Examples 53-56

[0204] The embodiment provides a battery that is basically the same as the 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, see Table 19, and the results are shown in Table 20.

[0205] Table 19 Parameters of Examples 53-56

[0206]

[0207] Table 20 Test results of Examples 53-56

[0208]

[0209] The above results show that when the negative electrode current collector is a composite foil, and 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 ranges of the present invention, further adjusting the values ​​of A and B can help improve battery cycle performance and reduce problems such as foil breakage and active material cracking. Silicon content below 1.5 wt% is detrimental to contact between silicon particles and the carbon matrix, affecting the structural stability of the electrode and, consequently, the cycle life.

[0210] Examples 57-60

[0211] The embodiment provides a battery that is basically the same as 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, see Table 21, and the results are shown in Table 22.

[0212] Table 21 Parameters of Examples 57-60

[0213]

[0214] Table 22 Test results of Examples 57-60

[0215]

[0216] The above results 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 ranges of the present invention, further adjusting the values ​​of A and D can help improve battery cycle performance and reduce problems such as foil breakage and active material cracking. Silicon content below 1.5wt% is detrimental to contact between silicon particles and the carbon matrix, affecting the structural stability of the electrode and, consequently, the cycle life.

[0217] Examples 61-64

[0218] The embodiment provides a battery that is basically the same as 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, see Table 23, and the results are shown in Table 24.

[0219] Table 23 Parameters of Examples 61-64

[0220]

[0221] Table 24 Test results of Examples 61-64

[0222]

[0223] The above results 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 ranges of the present invention, further adjusting the values ​​of A and D can help improve battery cycle performance and reduce problems such as foil breakage and active material cracking. Silicon content below 1.5 wt% is detrimental to contact between silicon particles and the carbon matrix, affecting the structural stability of the electrode and, consequently, the cycle life.

[0224] Obviously, the above embodiments are merely examples for clarity of explanation and are not intended to limit the implementation methods. Those skilled in the art will appreciate that other variations or modifications can be made based on the above description. It is not necessary and impossible to enumerate all implementation methods here. Obvious variations or modifications arising therefrom remain within the scope of protection of the present invention.

Claims

1. A battery comprising a negative electrode sheet and a positive electrode sheet, wherein the negative electrode sheet comprises a negative electrode current collector and a negative electrode active material layer disposed on at least one surface of the negative electrode current collector, characterized in that: The negative electrode active material layer includes a negative electrode active material, and the negative electrode active material 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 is the elemental silicon content in the negative electrode active material layer, in wt%; the range of A is 1.5wt% to 17.5wt%; B is the elongation at break of the negative electrode current collector, in %. The positive electrode sheet includes a positive electrode current collector; 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: Wherein, D is the elongation at break of the positive electrode current collector, in %.

2. The battery according to claim 1, characterized in that The range of B is 3% to 100%.

3. The battery according to claim 1, characterized in that The negative electrode current collector comprises 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. The battery according to claim 1, characterized in that The range of D is 3% to 90%.

8. The battery according to claim 6, characterized in that The positive electrode current collector includes a second conductive layer and a second polymer substrate layer, and the second polymer substrate layer is provided 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:

9. The battery according to claim 8, characterized in that The range of D is 10% to 80%.

10. The battery according to claim 1, characterized in that 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:

11. The battery according to claim 10, characterized in that The range of D is 5% to 15%.

12. The battery according to claim 1, characterized in that 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%.

13. A device, characterized in that: A battery comprising the battery according to any one of claims 1 to 12.

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