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, the negative pole piece comprises a current collector and a negative active material layer arranged on at least one surface of the 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, 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

Technical Field

[0001] The invention belongs to the technical field of battery preparation, and in particular relates to a battery and a device. Background Art

[0002] Lithium-ion batteries have the advantages of high energy density, long cycle life, low self-discharge rate and no memory effect, and have broad application prospects in the field of new energy. With the development of science and technology, the requirements for the performance of lithium-ion batteries are getting higher and higher. As the requirements for battery energy density continue to increase, safety issues are becoming increasingly prominent. Especially when the negative electrode contains silicon, how to balance the energy density, safety and cycle performance of the battery is still a technical problem faced by technicians in this field. Summary of the invention

[0003] 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.

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

[0005] A first aspect of the present invention provides a battery, the 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:

[0006]

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

[0008] B is the elongation at break of the negative electrode current collector, in %.

[0009] As an optional implementation manner, the range of A is 1.5wt% to 17.5wt%; and / or the range of B is 3% to 100%.

[0010] 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;

[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 manner, the range of B is 5% to 15%.

[0017] 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:

[0018]

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

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

[0021] 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 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:

[0022]

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

[0024] As an optional implementation, 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:

[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 electrode current collector and the elongation at break D of the positive electrode current collector is 1% to 3%.

[0028] A second aspect of the present invention provides a device comprising the above-mentioned battery.

[0029] The beneficial effects of the present invention are:

[0030] The present invention provides a battery. By controlling the silicon content and the elongation at break of the negative electrode within a suitable range, 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 breakage of the negative electrode foil, thereby improving the battery capacity density, cycle performance and safety performance. DETAILED DESCRIPTION

[0031] The following examples are provided for a better understanding of the present invention, but are not intended to limit the best mode of implementation, nor to limit the content and protection scope of the present invention. Any product identical or similar to the present invention obtained by anyone under the inspiration of the present invention or by combining the features of the present invention with other prior arts shall fall within the protection scope of the present invention.

[0032] If no specific experimental steps or conditions are specified in the examples, the conventional experimental steps or conditions described in the literature in the field can be used. If no manufacturer is specified for the reagents or instruments used, they are all conventional reagent products that can be obtained commercially.

[0033] An embodiment of the present invention provides a battery, the 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:

[0034]

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

[0036] B is the elongation at break of the negative electrode current collector, in %.

[0037] 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 ensured, and at the same time, the electrode piece can be prevented from breaking due to silicon expansion, and the risk of positive and negative short circuit caused by the negative electrode breaking process can be avoided, 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 break 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 surface of the electrode piece to crack easily, thereby affecting the battery life.

[0038] 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 the volume changes by up to 300% after lithium insertion. 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 embedded, 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 further affecting the battery life. When the B value is within the above range, not only can the negative electrode foil adapt to the expansion of silicon particles and prevent the occurrence of cracking of the negative electrode foil, but also can avoid the phenomenon of short circuit caused by the overlap of the negative electrode foil and the shell or the positive electrode sheet due to the excessive elongation at break of the negative electrode foil; improve the safety performance of the battery. Therefore, controlling B within the above range can reduce the broken belt during the processing process and improve production efficiency.

[0039] In the present invention, 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 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 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 pole piece. 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.

[0042] 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.

[0043] 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:

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

[0046] 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 improved. The current carrying capacity of the foil can also be guaranteed, thereby ensuring the safety performance of the battery.

[0047] 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:

[0048]

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

[0050] After winding or stacking, the battery will go through a hot pressing process, which will melt some of the binder components in the positive and negative active material layers. Therefore, after hot pressing, there is a certain degree of adhesion between the positive and negative electrodes and the separator; or the industry currently selects some sticky separators with sticky surfaces, which will further improve the bonding strength between the positive and negative electrodes and the separator. Then, 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 will stretch, which will cause the separator with better ductility to stretch as well. The separator will further spread 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 stretch, resulting in the positive electrode being pulled apart, and the positive active material and the positive current collector being delaminated. 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.

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

[0052] 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 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] 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 simultaneously improve the energy density of the battery.

[0055] 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 life of the battery, and improve the preparation efficiency and yield rate of the battery cell.

[0056] 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:

[0057]

[0058] In the present invention, the positive electrode current collector is a 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 ranges, which can further reduce the demoulding of the positive electrode active material, the breakage of the electrode piece, etc., further reduce the accidental touching of the positive and negative electrode pieces, and improve the safety performance of the battery.

[0059] 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.

[0060] 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%. The present invention controls the elongation at break of the two current collectors to meet the above range, the DCR is small, the negative electrode active material layer and the positive electrode active material layer are matched, the risk of negative electrode lithium plating is reduced, and the cycle capacity retention rate is increased.

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

[0062] (1) Preparation of negative electrode sheet

[0063] The negative electrode active material is mixed with the auxiliary agent, and a solvent is added to obtain the negative electrode slurry; the negative electrode slurry is coated on at least one surface of the negative electrode current collector, and the negative electrode sheet is obtained after drying, cold pressing, and cutting. The auxiliary agent includes a conductive agent, a binder, a thickener, etc.

[0064] 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 obtained by the prior art according to their needs. Here are several preparation methods of silicon-containing materials:

[0065] Preparation method of silicon-carbon composite negative electrode material by gas phase method

[0066] Porous carbon materials as carbon matrix (porous carbon type: pore size 4-5nm, specific surface area range 900-1800m 2 / g), add it into a rotary kiln, introduce nitrogen to remove oxygen, and heat it up for roasting, wherein the flow rate of nitrogen, the roasting temperature and heating rate, and the rotation speed of the rotary kiln are common parameters in the art, such as the nitrogen flow rate can be set to 8-25L / min, the roasting heating rate can be 10-30℃ / min, the temperature is 500-800℃, and the rotary kiln rotation speed is 100-300rpm. Keep the roasting temperature unchanged, introduce a mixed gas, the mixed gas includes nitrogen and silane (such as monosilane, etc.) in a volume ratio of 1: (1-7), and the flow rate of the mixed gas is 0.1-0.2L / min, specifically: pass at a flow rate of 0.1-0.2L / min for 8h, then pass at a flow rate of 0.2-0.4L / min for 8h, and then pass at a flow rate of 0.1-0.2L / min for 8h. After the reaction is completed, stop introducing silane gas and only introduce nitrogen gas. Calcinate 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, introduce acetylene gas at a rate of 0.8-2.5L / min for reaction. After continuing to introduce acetylene gas for 5-12 hours, turn off the acetylene gas and cool naturally in a nitrogen atmosphere. After it is completely cooled to room temperature, take out the material for crushing, screening, and demagnetization to obtain a silicon-carbon composite negative electrode material.

[0067] Preparation method of silicon oxide negative electrode material

[0068] Precursor preparation: Mix silica powder and silicon powder in a VC mixer at a molar ratio of 1:0.5-3, and subject the mixed powder to high-temperature vacuum treatment in a vacuum atmosphere furnace sample chamber; wherein the temperature range of high-temperature vacuum treatment is 600-1800°C, and the material after high-temperature vacuum treatment is subjected to airflow crushing, and then the precursor powder with fine powder removed is obtained through dust removal equipment. Precursor coating: Place the above-mentioned precursor powder with fine powder removed in a continuous rotary kiln, and introduce a mixed gas into the rotary kiln, wherein the mixed gas includes argon and acetylene, the volume ratio of argon and acetylene is 1:1, and the introduction rate of the mixed gas is 0.2-1.5L / min. After continuous introduction for 20-60min, the air in the furnace tube is discharged, and then the temperature is raised to 700-800°C at a heating rate of 5-10°C / min and calcined for 1-4h to obtain silicon dioxide negative electrode material.

[0069] Preparation method of silicon-carbon composite material by sand grinding

[0070] 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 mixed and 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.

[0071] 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).

[0072] The current collector may be a composite current collector or a metal foil; for example, the composite current collector includes a conductive layer and a polymer substrate layer, a polymer substrate layer is provided 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.

[0073] (2) Preparation of positive electrode sheet

[0074] The positive electrode active material and the auxiliary agent 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 the positive electrode sheet is obtained after drying, cold pressing, and cutting. The auxiliary agent includes a conductive agent, a binder, etc.

[0075] 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 demand 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).

[0076] The current collector may be a composite current collector or a metal foil; for example, the composite current collector includes a conductive layer and a polymer substrate layer, a polymer substrate layer is provided 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.

[0077] (3) Electrolyte

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

[0079] A conventional lithium salt in the art is used. As an example, the lithium salt is lithium hexafluorophosphate (LiPF 6 ), lithium tetrafluoroborate (LiBF 4 ), lithium perchlorate (LiClO 4 ) lithium hexafluoroarsenate (LiAsF 6 ), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalatoborate (LiDFOB), lithium dioxalatoborate (LiBOB), lithium difluorophosphate (LiPO 2 F 2 ), at least one of lithium difluorobis(oxalate) 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)), carboxylates (methyl propionate (EP)), etc.

[0081] (4) Diaphragm

[0082] The separator is disposed between the positive electrode sheet and the negative electrode sheet to separate the positive electrode sheet and the negative electrode sheet to prevent the positive electrode sheet and the negative electrode sheet from short-circuiting. The present invention does not make specific requirements on the manufacturer, preparation process, type, etc. of the separator. As an example, the separator can be a PE film (polyethylene) or a PP film (polypropylene).

[0083] (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, packaged, allowed to stand, and formed to obtain a lithium-ion battery.

[0084] The embodiment of the present invention further provides a device, including the above-mentioned battery. The device refers to any device that can utilize electrical energy and convert it into mechanical energy, thermal energy, light energy or other one or more forms of energy, such as a motor, an electric heat engine, an electric light source, etc. As an example, it can be, but not limited to, an electric vehicle, an electric train, a ship, a mobile phone, etc.

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

[0086] 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 by the following methods.

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

[0088] The disassembled negative electrode piece was immersed in a container containing DMC, and the negative electrode piece after immersion for 8 hours was placed in an oven at 45°C 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 cross-section of the treated negative electrode piece was polished by an argon ion beam, and each section of the same sample was scanned by SEM at 4 locations. Four fields of view were selected for surface scanning at 500 times, and the average value of all values ​​of silicon content obtained by surface scanning of 16 fields of view of the four sections was taken as the most accurate conclusion, that is, the silicon content in the negative active material layer. The silicon content in the negative active material layer refers to the proportion of silicon element in the mass of all substances in the negative active material layer.

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

[0090] Disassemble the battery to obtain the pole piece, soak the disassembled pole piece in a container filled with deionized water, and ultrasonicate it in an ultrasonic cleaner for 30 minutes to remove the active material on the surface of the current collector. Place the soaked pole piece in a 45°C oven and bake it for 10 minutes to remove the residual moisture; use a diaphragm slitting machine to cut a 150mm long and 15mm wide strip sample, the original gauge length between the clamps is 100mm, and the stretching speed is (100±10)mm / min; apply a static tensile load uniformly along the axial direction of the foil until the foil breaks, measure the elongation length of the sample at this time, and divide it by the gauge length of the sample to obtain the elongation at break. Both the positive current collector and the negative current collector can obtain the elongation at break according to this test method.

[0091] (3) Electrochemical performance test method:

[0092] Cycle performance test method: At 25°C, the lithium ion batteries prepared in the examples and comparative examples were subjected to cycle tests 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, and the number of cycles at this time was recorded.

[0093] (4) Integrity test of positive and negative electrodes

[0094] At 25°C, the lithium-ion batteries prepared in the embodiments 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 embodiments and comparative examples were disassembled to observe the integrity of the positive and negative electrodes.

[0095] (5) Self-discharge value test

[0096] At 25°C, first charge to 4.25V at 1 / 3C rate, let stand for 10min, discharge to 2.5V at 1 / 3C rate, let stand for 10min, and cycle 100 times. Then charge to 4.25V at 1 / 3C rate and let stand for 30min. Measure the open circuit voltage at this time, record it as OCV1, and continue to stand for 2d. Record the open circuit voltage at this time, record it as OCV2, and calculate the voltage change voltage drop (K value) according to the formula; the K value calculation formula is as follows:

[0097]

[0098] Example 1

[0099] This embodiment provides a battery, and the preparation method thereof includes:

[0100] (1) Preparation of negative electrode sheet

[0101] 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 into a rotary kiln, nitrogen was introduced to remove oxygen, and the flow rate was set to 10L / min. After the oxygen was removed, the temperature was raised for calcination, the calcination temperature was 500°C, the heating rate was 10°C / min, the rotation speed was 100rpm, the temperature was kept constant, and a nitrogen and monosilane mixed gas with a volume ratio of 1:4 was introduced, the mixed gas was first ventilated at a flow rate of 0.15L / min for 8h, then at a flow rate of 0.3L / min for 8h, and finally at a flow rate of 0.2L / min for 8h. After the reaction was completed, the silane gas was turned off, and the mixture was calcined under a nitrogen atmosphere at a calcination temperature of 550°C and a heating rate of 10°C / min. When the temperature was stable, acetylene gas was introduced with a flow rate set to 1L / min. The acetylene gas was turned off after the temperature was kept constant and ventilation was performed for 10h, and the temperature was naturally cooled under a nitrogen atmosphere. After the cooling was complete, the material was taken out for crushing, screening, and demagnetization to obtain a silicon-carbon composite material.

[0102] The carbon-coated silicon-carbon composite material and the conductive agent acetylene black binder SBR are mixed at a mass ratio of 97:1.5:1.5, and deionized water is added as a solvent, and stirred under the action of a vacuum mixer to obtain a negative electrode slurry; the negative electrode slurry is evenly coated on both surfaces of the negative electrode current collector copper foil, and after drying at room temperature, it is transferred to an oven for further drying, and then cold pressed and cut to obtain a negative electrode sheet. 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, the conductive agent acetylene black, and the binder PVDF were mixed in a mass ratio of 96:2:2, and the solvent NMP was added, and the mixture was stirred and mixed under the action of a vacuum mixer to obtain a positive electrode slurry; the positive electrode slurry was 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, and then cold pressed and cut to obtain a positive electrode sheet. 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, and then the fully dried lithium salt LiPF 6 The electrolyte is dissolved in the mixed organic solvent to prepare a lithium salt concentration of 1 mol / L.

[0107] (4) Diaphragm

[0108] Polyvinyl alcohol was used as the separator.

[0109] (5) stacking the positive electrode sheet, separator, and negative electrode sheet in order, placing the separator 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.

[0110] Example 2

[0111] This embodiment provides a battery, which is basically the same as Example 1, except that the preparation method of the negative electrode active material 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. Among them, 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 of this embodiment is a silicon oxide negative electrode material, and its preparation method includes: mixing silicon dioxide powder and silicon powder with a molar ratio of 1:2 in a VC mixer, subjecting the mixed powder to high-temperature vacuum treatment in a sample chamber of a vacuum atmosphere furnace at 1650°C, crushing the material after high-temperature treatment under an air flow mill, and obtaining a precursor powder with fine powder removed through a dust removal device. The above-mentioned precursor powder is placed in a continuous rotary furnace, and an inert gas mixture of argon and acetylene is introduced into the rotary furnace. The volume ratio of argon and acetylene is 1:1, the introduction rate of the mixed gas is 1L / min, the ventilation time is 30min, and the air in the furnace tube is discharged. Then, it is calcined at 750°C for 2h with a heating rate of 5°C / min. After the temperature drops to room temperature, the sample is taken out to obtain a silicon oxide negative electrode material.

[0112] Example 3

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

[0114] Embodiment 4-7

[0115] Embodiment 4-7 provides a battery, which 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.

[0116] Comparative Examples 1-4

[0117] This comparative example provides a battery, which 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.

[0118] 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.

[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] From the above results, it can be seen that, in combination with Examples 6-7, the present invention further regulates the negative electrode active material layer silicon content A and the positive electrode current collector elongation at break D to meet 0.19-0.55 on the basis of the negative electrode active material layer silicon content A and the negative electrode current collector elongation at break B meeting 0.17-0.6, which can further improve the battery cycle performance and reduce the problems of wrinkles on the positive electrode sheet and cracks in the material layer. Further, in combination with Comparative Examples 1-2, when the negative electrode active material layer silicon content A and the negative electrode current collector elongation at break B ratio are too large or too small, the negative electrode sheet wrinkles, active material cracks and foil breakage will occur, and the battery cycle performance will be significantly reduced; K value is an indicator for evaluating the risk of short circuit in the battery. K value exceeding 0.045 indicates that the risk of short circuit in the battery is high. The larger the K value, the higher the risk of short circuit in the battery. When the ratio of the negative electrode active material layer silicon content A and the negative electrode current collector elongation at break B is too small, the risk of short circuit in the battery is increased. Comparative Examples 3-4 adjust the silicon content in the negative electrode active material layer on the basis of Comparative Examples 1-2, indicating that when the silicon content A in the negative electrode active material layer meets 1.5%-17.5%, the appropriate ratio can further improve the battery cycle performance.

[0125] Example 8

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

[0127] Example 9

[0128] This embodiment provides a battery, which is basically the same as that of embodiment 8, except that the negative electrode active material 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. The preparation method of the negative electrode active material of this embodiment is the same as that of 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, which is basically the same as that of embodiment 8, except that the negative electrode active material 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. The preparation method of the negative electrode active material of this embodiment is the same as that of 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 substantially the same as 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.

[0133] Comparative Examples 5-8

[0134] This comparative example provides a battery, which is basically the same as 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 of 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] Embodiment 15

[0141] This embodiment provides a battery, which 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 positive electrode current collector and its elongation at break are different. The positive electrode current collector of this embodiment includes a PP film and copper foils disposed on both sides of the PP film, the thickness of the PP film is 8.0 μm, and the thickness of the single-sided copper foil is 1.2 μm.

[0142] Examples 16-21

[0143] Embodiments 16-21 provide a battery that is substantially 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.

[0144] Comparative Examples 9-12

[0145] 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.

[0146] 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.

[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] Embodiment 22

[0153] This embodiment provides a battery, which is basically the same as that of Embodiment 1, except that the silicon content in the negative electrode active material layer is different, the negative electrode current collector and its elongation at break are different, and the positive electrode current collector and its elongation at break are different. The negative electrode current collector of this embodiment includes a PET film and copper foils arranged 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 positive electrode current collector of this embodiment includes a PP film and copper foils arranged 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 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 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 of 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] From the above results, whether the negative electrode current collector or the positive electrode current collector is a metal foil or a composite material (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 the problems of wrinkling of the pole piece 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 the problems of wrinkling of the pole piece and fracture of the current collector will be reduced, 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.

[0165] Examples 29-33

[0166] The embodiment provides a battery, which 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.

[0167] Table 9 Parameters of Examples 29-33

[0168]

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

[0170]

[0171] From the above results, it can be seen that when the negative electrode current collector is a metal foil, regulating the elongation at break of the negative electrode current collector to meet 5%-15% can help 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, 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 meet 0.3-0.6 can improve the cracking of the active material layer and the cycle performance of the battery.

[0172] Examples 34-38

[0173] The embodiment provides a battery, which 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 collector is different, and the elongation at break of the positive electrode collector is different, see Table 11, and 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] From the above results, it can be seen that when the negative electrode current collector is a composite foil, regulating the elongation at break of the negative electrode current collector to meet 10%-80% can help 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, 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 meet 0.17-0.35 can improve the cracking of the active material layer and the cycle performance of the battery.

[0180] Examples 39-43

[0181] The embodiment provides a battery, which 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.

[0182] Table 13 Parameters of Examples 39-43

[0183]

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

[0185]

[0186] From the above results, it can be seen that when the positive electrode current collector is a metal foil, regulating the elongation at break of the positive electrode current collector to meet 5%-15% can help 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 the silicon content A in the negative electrode active material layer to the elongation at break D of the positive electrode current collector meets 0.3-0.55, which 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, which is basically the same as the embodiment 15, except that the silicon content in the negative electrode active material layer is different, the elongation at break of the negative electrode collector is different, and the elongation at break of the positive electrode collector is different, see Table 15, and 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] From the above results, it can be seen that when the positive electrode current collector is a composite foil, regulating the elongation at break of the positive electrode current collector to meet 10%-80% can help 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 the silicon content A in the negative electrode active material layer to the elongation at break D of the positive electrode current collector meets 0.19-0.35, which can improve the cracking of the active material layer and the battery cycle performance.

[0195] Examples 49-52

[0196] The embodiment provides a battery, which 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 collector is different, and the elongation at break of the positive electrode collector is different, see Table 17, and 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] It can be seen from the above results that when the negative electrode current collector is a metal foil, 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 range of the present invention, further adjusting the values ​​of A and B will help improve the battery cycle performance and reduce problems such as foil breakage and active material cracking. When the silicon content is lower than 1.5wt%, it is not conducive to the contact between silicon particles and the carbon matrix, affecting the structural stability of the electrode, thereby affecting the cycle life.

[0202] Examples 53-56

[0203] The embodiment provides a battery, which 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.

[0204] Table 19 Parameters of Examples 53-56

[0205]

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

[0207]

[0208] It can be seen from the above results that when the negative electrode current collector is a composite foil, 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 range of the present invention, further adjusting the values ​​of A and B will help improve the battery cycle performance and reduce problems such as foil breakage and active material cracking. When the silicon content is lower than 1.5wt%, it is not conducive to the contact between silicon particles and the carbon matrix, affecting the structural stability of the electrode, thereby affecting the cycle life.

[0209] Examples 57-60

[0210] The embodiment provides a battery, which 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 21, and 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] It can be seen from the above results that when the positive electrode current collector is a metal foil, when 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 range of the present invention, further adjusting the values ​​of A and D will help improve the battery cycle performance and reduce problems such as foil breakage and active material cracking. When the silicon content is lower than 1.5wt%, it is not conducive to the contact between silicon particles and the carbon matrix, affecting the structural stability of the electrode, thereby affecting the cycle life.

[0216] Examples 61-64

[0217] The embodiment provides a battery, which is basically the same as the 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 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] It can be seen from the above results that when the positive electrode current collector is a composite foil, when 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 range of the present invention, further adjusting the values ​​of A and D will help improve the battery cycle performance and reduce problems such as foil breakage and active material cracking. When the silicon content is lower than 1.5wt%, it is not conducive to the contact between silicon particles and the carbon matrix, affecting the structural stability of the electrode, thereby affecting the cycle life.

[0223] Obviously, the above embodiments are merely examples for the purpose of clear explanation, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived from these are still within the scope of protection of the invention.

Claims

1. A battery, comprising a negative electrode plate, wherein the negative electrode plate comprises 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, 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 element silicon content in the negative electrode active material layer, in wt%; B is the elongation at break of the negative electrode current collector, in %.

2. The battery according to claim 1, characterized in that The range of A is 1.5 wt% to 17.5 wt%; 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 at least comprises 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 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: Wherein, D is the elongation at break of the positive electrode current collector, in %.

8. The battery according to claim 7, characterized in that The range of D is 3% to 90%.

9. 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 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:

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

11. The battery according to claim 7, 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:

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

13. The battery according to claim 7, 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%.

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

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