A lithium ion battery monomer, a battery module, a vehicle, a robot and a smart device

Abstract

The application belongs to the technical field of battery preparation, and particularly relates to a lithium ion battery monomer, a battery module, a vehicle, a robot and an intelligent device. The lithium ion battery monomer provided by the application comprises a battery shell and an electrode assembly accommodated in the battery shell, and the electrode assembly comprises a positive electrode sheet and a negative electrode sheet. The positive electrode sheet comprises a positive electrode active material, the positive electrode active material comprises a lithium-rich manganese-based positive electrode material, the negative electrode sheet comprises a negative electrode active material, the negative electrode active material comprises a silicon-based material, and the content of silicon in the negative electrode active material is 3wt%-10wt%. The lithium-rich manganese-based positive electrode material is matched with the silicon element with a specific content, so that the battery monomer can have good safety performance and energy density, the energy density of the battery monomer can reach at least 300Wh / kg, and when the battery monomer is applied to an electric vehicle, the driving range is improved, and the driving range can be more than 800km.

Description

Technical Field

[0001] This invention belongs to the field of battery manufacturing technology, and particularly relates to a lithium-ion battery cell, battery module, vehicle, robot and intelligent device. Background Technology

[0002] As a core component of electric vehicles, the performance of the power battery directly affects the vehicle's range, charging efficiency, and safety and reliability. Currently, in practical applications, there is still room for improvement in the energy density of power batteries, limiting the range of electric vehicles, especially in low-temperature environments where battery discharge capacity decreases significantly, resulting in a substantial reduction in range and impacting the user experience in cold regions or winter. Therefore, improving battery energy density, while ensuring battery safety, is crucial for increasing the range of electric vehicles. Summary of the Invention

[0003] To further improve battery energy density, this invention provides a lithium-ion battery cell, a battery module, a vehicle, a robot, and a smart device.

[0004] In a first aspect, the present invention provides a lithium-ion battery cell, including a battery casing and an electrode assembly housed inside the battery casing, the electrode assembly including a positive electrode and a negative electrode. The positive electrode sheet includes a positive electrode active material, which includes a lithium-rich manganese-based positive electrode material. The chemical formula of the lithium-rich manganese-based positive electrode material is xLi2MnO3·(1-x)LiMO2, wherein M includes at least one of Co, Mn, Ni, Cr, Fe, and Al, and x satisfies: 0 < x < 1. The negative electrode sheet includes a negative electrode active material, which is a silicon-based material, and the silicon content in the negative electrode active material is 3wt%-10wt%.

[0005] As an optional implementation, the positive electrode includes a positive current collector and a positive active material layer disposed on at least one side of the positive current collector along its own thickness direction, the positive active material layer including the positive active material, and the mass content of the positive active material in the positive active material layer being 10%-99%; As an optional implementation, the lithium-rich manganese-based cathode material includes at least one of aluminum-doped lithium-rich manganese-based cathode material, chromium-doped lithium-rich manganese-based cathode material, lithium-rich manganese nickel oxide cathode material, and lithium-rich manganese cobalt nickel oxide.

[0006] As an optional implementation, the negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer disposed on at least one side of the negative electrode current collector along its own thickness direction, wherein the negative electrode active material layer includes the negative electrode active material; As an optional implementation, the mass content of the negative electrode active material in the negative electrode active material layer is 90%-97%; As an optional implementation, the specific capacity of the negative electrode active material is 350mAh / g-4200mAh / g.

[0007] As an optional implementation, the silicon-based material includes at least one of silicon, silicon-carbon, and silicon suboxide; As an optional implementation, the negative electrode active material also includes at least one of graphite, soft carbon, hard carbon, and lithium titanate.

[0008] As an optional implementation, the battery housing is cylindrical and includes an outer peripheral shell and a bottom plate and a top cover connected to the two axial ends of the outer peripheral shell. The outer peripheral shell and the bottom plate are integrally formed, and the space formed by the outer peripheral shell, the bottom plate and the top cover is used to accommodate the electrode assembly.

[0009] As an optional implementation, the battery casing may be made of nickel-plated steel strip; As an optional implementation, the height of the battery casing is 80mm-120mm; As an optional implementation, the inner diameter of the outer shell is 44.5mm-45.6mm; As an optional implementation, the wall thickness of the outer shell is 0.4mm-1.5mm.

[0010] As an optional implementation, the lithium-ion battery cell further includes a positive electrode tab and a negative electrode tab; The positive electrode tab is a full electrode tab; and / or, the negative electrode tab is a full electrode tab.

[0011] As an optional implementation, the lithium-ion battery is at least one of 4680 cells, 2170 cells, and 18650 cells.

[0012] Secondly, the present invention provides a battery module comprising the aforementioned lithium-ion battery cell.

[0013] As an optional implementation, two adjacent lithium-ion battery cells are connected by an adhesive layer.

[0014] Thirdly, the present invention provides a vehicle, robot, or intelligent device, including the aforementioned lithium-ion battery cell or the aforementioned battery module.

[0015] The technical solution provided by the embodiments of the present invention has the following advantages compared with the prior art: 1. The present invention provides a lithium-ion battery cell, comprising a battery casing and an electrode assembly housed within the battery casing. The electrode assembly includes a positive electrode and a negative electrode. The positive electrode includes a positive active material, which is a lithium-rich manganese-based positive electrode material with the chemical formula xLi₂MnO₃·(1-x)LiMO₂, wherein M includes at least one of Co, Mn, Ni, Cr, Fe, and Al, and x satisfies 0 < x < 1. The negative electrode includes a negative active material, which is a silicon-based material, wherein the silicon content in the negative active material is 3wt%-10wt%. The present invention uses a lithium-rich manganese-based positive electrode material, enabling the positive active material to achieve a capacity of over 230 mAh / g. By controlling the silicon content in the negative active material, the battery cell capacity is further improved, thereby greatly enhancing the battery cell's energy density and safety performance. The combination of lithium-rich manganese-based cathode material and a specific amount of silicon can enable battery cells to achieve both good safety performance and energy density. The energy density of the battery cell can reach at least 300Wh / kg. When this battery cell is applied to electric vehicles, the driving range can be improved, and the driving range can reach more than 800km. Detailed Implementation

[0016] To better understand the above-mentioned objectives, features, and advantages of the present invention, the solutions of the present invention will be further described below. It should be noted that, unless otherwise specified, the embodiments of the present invention and the features thereof can be combined with each other.

[0017] Many specific details are set forth in the following description in order to provide a full understanding of the invention, but the invention may also be practiced in other ways different from those described herein; obviously, the embodiments in the specification are only some embodiments of the invention, and not all embodiments.

[0018] Existing electric vehicles suffer from short driving range due to limitations in battery energy density. To address this, the first aspect of this invention provides a lithium-ion battery cell, including a battery casing and an electrode assembly housed within the battery casing, the electrode assembly comprising a positive electrode and a negative electrode. The positive electrode sheet includes a positive electrode active material, which includes a lithium-rich manganese-based positive electrode material. The chemical formula of the lithium-rich manganese-based positive electrode material is xLi2MnO3·(1-x)LiMO2, wherein M includes at least one of Co, Mn, Ni, Cr, Fe, and Al, and x satisfies: 0 < x < 1. The negative electrode sheet includes a negative electrode active material, which is a silicon-based material, and the silicon content in the negative electrode active material is 3wt%-10wt%. This invention employs lithium-rich manganese-based cathode materials, enabling the cathode active material capacity to reach over 230 mAh / g. By controlling the silicon content in the anode active material, the battery cell capacity is further improved, thereby significantly enhancing the battery cell energy density and safety performance. The combination of lithium-rich manganese-based cathode materials and a specific amount of silicon allows the battery cell to achieve both good safety performance and energy density, with a minimum energy density of 300 Wh / kg. When this battery cell is applied to electric vehicles, it increases the driving range, achieving a range of over 800 km.

[0019] As an example, the silicon content in the negative electrode active material is 3wt%, 4wt%, 5wt%, 6wt%, 7wt%, 8wt%, 9wt%, 10wt%, etc.

[0020] In some embodiments, the positive electrode sheet includes a positive current collector and a positive active material layer disposed on at least one side of the positive current collector along its own thickness direction, the positive active material layer including the positive active material, and the mass content of the positive active material in the positive active material layer is 10%-99%.

[0021] In some embodiments, the lithium-rich manganese-based cathode material includes at least one of aluminum-doped lithium-rich manganese-based cathode material, chromium-doped lithium-rich manganese-based cathode material, lithium-rich manganese nickel oxide cathode material, and lithium-rich manganese cobalt nickel oxide.

[0022] In some embodiments, the positive electrode active material layer further includes a conductive agent; optionally, the conductive agent includes at least one of conductive carbon black, conductive graphite, carbon nanotubes, graphene, carbon fiber, and polyaniline; the mass content of the conductive agent in the positive electrode active material layer is 0.5%-5%.

[0023] In some embodiments, the positive electrode active material layer further includes a binder; optionally, the binder includes at least one of sodium carboxycarboxylate, styrene-butadiene rubber, polyvinylidene fluoride, polytetrafluoroethylene, and polyacrylate; the mass content of the binder in the positive electrode active material layer is 0.5%-5%.

[0024] In some implementations, the thickness of the single-sided positive electrode active material layer is 60 μm-70 μm.

[0025] In some implementations, the positive current collector includes aluminum foil.

[0026] In some embodiments, the negative electrode sheet includes a negative current collector and a negative active material layer disposed on at least one side of the negative current collector along its own thickness direction, the negative active material layer including the negative active material.

[0027] In some embodiments, the mass content of the negative electrode active material in the negative electrode active material layer is 90%-97%.

[0028] In some embodiments, the specific capacity of the negative electrode active material is 350 mAh / g to 4200 mAh / g. For example, the specific capacity of the negative electrode active material is 350 mAh / g, 400 mAh / g, 600 mAh / g, 1000 mAh / g, 1500 mAh / g, 2000 mAh / g, 2500 mAh / g, 3000 mAh / g, 3500 mAh / g, 4000 mAh / g, 4500 mAh / g, 4200 mAh / g, etc.

[0029] In some embodiments, the silicon-based material includes at least one of silicon, silicon-carbon, and silicon suboxide.

[0030] In some embodiments, the negative electrode active material further includes at least one of graphite, soft carbon, hard carbon, and lithium titanate. The negative electrode active material of this invention includes silicon-based materials as well as at least one of graphite, soft carbon, hard carbon, and lithium titanate. The combined use of these negative electrode active materials is beneficial for improving the cycle life of individual battery cells.

[0031] This invention does not impose any limitation on the content of silicon-based materials in the negative electrode active material; optionally, the content of silicon-based materials in the negative electrode active material is 5wt%-95wt%. As an example, the content of silicon-based materials in the negative electrode active material is 5wt%, 10wt%, 15wt%, 20wt%, 25wt%, 30wt%, 35wt%, 40wt%, 45wt%, 50wt%, 55wt%, 60wt%, 65wt%, 70wt%, 75wt%, 80wt%, 85wt%, 90wt%, 95wt%, etc.

[0032] In some embodiments, the negative electrode active material layer further includes a conductive agent; optionally, the conductive agent includes at least one of conductive carbon black, conductive graphite, carbon nanotubes, graphene, and carbon fiber; the mass content of the conductive agent in the negative electrode active material layer is 0.5%-1%.

[0033] In some embodiments, the negative electrode active material layer further includes a binder; optionally, the binder includes at least one of sodium carboxycarboxylate, styrene-butadiene rubber, polyvinylidene fluoride, polytetrafluoroethylene, and polyacrylate; the mass content of the binder in the negative electrode active material layer is 2%-3%.

[0034] In some implementations, the negative current collector includes copper foil.

[0035] In some embodiments, the battery housing is cylindrical and includes an outer peripheral shell and a bottom plate and a top cover connected to the two axially upward ends of the outer peripheral shell. The outer peripheral shell and the bottom plate are integrally formed, and the space formed by the outer peripheral shell, the bottom plate and the top cover is used to accommodate the electrode assembly.

[0036] In some embodiments, the battery casing is made of nickel-plated steel strip. Optionally, the nickel-plated steel strip includes at least one of SPCC and SPCE.

[0037] Silicon in the negative electrode expands due to volume changes during cycling. The R-corner of the battery is prone to damage and wrinkles due to stress concentration. This invention uses nickel-plated steel strip as the battery casing material, which can fully absorb the volume expansion of silicon in the negative electrode during charging and discharging, reduce damage and wrinkles of individual battery cells, and improve the safety performance of individual battery cells.

[0038] In some embodiments, the height of the battery casing is 80mm-120mm; In some embodiments, the inner diameter of the outer periphery shell is 44.5 mm to 45.6 mm; In some embodiments, the wall thickness of the outer shell is 0.4 mm to 1.5 mm.

[0039] In some embodiments, the top cover is provided with a pole post; In some embodiments, the base plate is provided with a pressure relief valve.

[0040] The pressure relief valve and terminals are located on opposite sides of the battery casing, achieving a design where electrical connection and thermal runaway pressure relief are handled on opposite sides, further improving the safety of the battery cell after thermal runaway. Optionally, the terminals are integrated with the top cover, and the pressure relief valve is integrated with the base plate.

[0041] In some embodiments, the pressure relief valve is set to a pressure of 0.4 MPa-1.2 MPa.

[0042] In some implementations, a lithium-ion battery cell includes a positive electrode tab and a negative electrode tab; The positive electrode tab is a full electrode tab; and / or, the negative electrode tab is a full electrode tab.

[0043] The battery of this invention adopts a full tab design, which enables the two ends of the positive and negative current collectors to make surface contact, forming a stable full tab structure. The current transmission method is changed from the traditional line transmission to surface transmission, which greatly improves the current conduction area and overcurrent capacity, reduces the battery internal resistance, and also increases the heat conduction area, increases heat conduction, reduces heat generation, avoids heat concentration and temperature rise, alleviates thermal runaway, and is conducive to achieving 4C-6C high current charging and improving the battery fast charging performance.

[0044] In some embodiments, the electrode assembly further includes a separator located between the positive electrode and the negative electrode, the separator comprising at least one base film. Optionally, the base film is made of at least one of polyethylene (PE) and polypropylene (PP); optionally, the separator comprises multiple layers of base films stacked together, the adjacent base films being made of the same or different materials.

[0045] In some embodiments, a ceramic layer and / or an adhesive layer are provided on at least one side of the base film along its thickness direction.

[0046] Optionally, the ceramic layer comprises at least one of alumina and boehmite. Optionally, the adhesive layer comprises at least one of polyvinylidene fluoride (PVDF) and acrylate adhesive.

[0047] In some embodiments, the lithium-ion battery further includes an electrolyte; the electrolyte includes a solvent, an electrolyte, and optionally additives.

[0048] In some embodiments, the solvent in the electrolyte includes at least one of carbonate solvents, carboxylic acid ester solvents, fluorinated ester solvents, ether solvents, and sulfone solvents.

[0049] In some embodiments, the electrolyte in the electrolyte includes at least one of LiPF6, LiBF4, Li(CF3SO2)2N, and LiCF3SO3.

[0050] In some embodiments, the additives in the electrolyte include fluorinated organic compounds.

[0051] In some embodiments, the lithium-ion battery is at least one of 4680 cells, 2170 cells, and 18650 cells.

[0052] A second aspect of the present invention provides a battery module comprising the aforementioned lithium-ion battery cell.

[0053] In some embodiments, adjacent lithium-ion battery cells are connected by an adhesive layer; optionally, the adhesive layer is made of at least one of thermally conductive silicone adhesive, thermally conductive polyurethane structural adhesive, and thermally conductive epoxy resin adhesive. Optionally, the adhesive layer is disposed on the outer surface of the battery casing, thereby achieving the connection between adjacent battery cells. Optionally, potting is used when applying the adhesive layer. The presence of an adhesive layer in the battery module helps improve safety after thermal runaway of individual battery cells.

[0054] A third aspect of the present invention provides a vehicle, robot, or smart device, including the aforementioned lithium-ion battery cell or battery module. Optionally, the smart device includes smartphones, tablets, laptops, headphones, speakers, smart bracelets, smart glasses, smart door locks, robot vacuum cleaners, floor scrubbers, electric toothbrushes, smartwatches, smart cameras, video doorbells, and other devices.

[0055] In this invention, unless otherwise specified, all percentages are by mass, and the raw materials and equipment used are common materials and conventional equipment in this field.

[0056] Example 1 This embodiment provides a lithium-ion battery cell, including: Positive electrode: Positive active material 0.5Li2MnO3·0.5LiNi 0.33 Co 0.33 Mn 0.33 O2 (positive electrode active material capacity of 230mAh / g), conductive agent (conductive carbon black, conductive graphite, and carbon nanotubes in a mass ratio of 1:1:1), and binder polyvinylidene fluoride are mixed in a mass ratio of 95%, 3%, and 2%, respectively. N-methylpyrrolidone (NMP) solvent is added, and the mixture is mixed evenly to form a slurry. This slurry is then coated on both surfaces of an aluminum foil and dried to form a positive electrode active material layer, thus obtaining the positive electrode sheet. The thickness of the positive electrode active material layer on one side is 65μm.

[0057] Negative electrode sheet: Negative electrode active material (graphite and silicon carbon in a mass ratio of 1:1, silicon content in the negative electrode active material is 6wt%, capacity is 539mAh / g), conductive agent (conductive carbon black, conductive graphite and carbon nanofibers in a mass ratio of 1:1:1), binder (sodium carboxycarboxylate CMC and styrene-butadiene rubber SBR in a mass ratio of 1:1) are mixed in a mass ratio of 92%, 6% and 2%, respectively. Solvent water is added and mixed evenly to form a slurry. This slurry is coated on both surfaces of a 6μm thick copper foil and dried to form a negative electrode active material layer. The thickness of the negative electrode active material layer on one side is 40μm, thus obtaining the negative electrode sheet.

[0058] The membrane consists of a PE base membrane with a thickness of 7 μm, on both sides of the PE base membrane, with a PVDF adhesive layer on each side having a thickness of 1.5 μm. An alumina ceramic layer with a thickness of 2 μm is disposed on one of the PVDF adhesive layers.

[0059] Electrolyte: includes ethylene carbonate, dimethyl carbonate, and fluoroethylene carbonate in a volume ratio of 30:60:10. The electrolyte also includes lithium hexafluorophosphate (LiPF6) at a concentration of 1 mol / L and lithium bis(oxalatoborate) (LiBOB) at a concentration of 0.1 mol / L.

[0060] The positive electrode, separator, and negative electrode are stacked in sequence and wound to obtain an electrode assembly. The electrode assembly is placed in a cylindrical battery casing (made of nickel-plated steel strip SPCC). The battery casing includes an outer shell and a bottom plate and a top cover connected to the axial ends of the outer shell. The bottom plate is equipped with a pressure relief valve with a set pressure of 0.8MPa. The pressure relief valve is integrated with the bottom plate. The top cover is integrated with the electrode post. The positive and negative electrode are full tabs. The electrode post is connected to the full tabs. Electrolyte is injected into the battery casing. After formation, degassing, and sealing, a cylindrical battery with a diameter of 46mm and a height of 80mm is obtained.

[0061] Example 2 This embodiment provides a lithium-ion battery cell, which is basically the same as that in Embodiment 1. The main difference is that the mass ratio of silicon-carbon to graphite is adjusted to 83:17, so that the silicon content in the negative electrode active material is 10wt% and the specific capacity of the negative electrode active material is 665mAh / g.

[0062] Example 3 This embodiment provides a lithium-ion battery cell, which is basically the same as that in Embodiment 1. The main difference is that the mass ratio of silicon carbon to graphite is adjusted to 25:75, so that the silicon content in the negative electrode active material is 3wt% and the specific capacity of the negative electrode active material is 445mAh / g.

[0063] Example 4 This embodiment provides a lithium-ion battery cell, which is basically the same as that in Embodiment 1. The main difference is the adjustment of the silicon-based material. The negative electrode active material in this embodiment includes silicon and graphite in a mass ratio of 6:94. The silicon content in the negative electrode active material is the same as that in Embodiment 1. The specific capacity of the negative electrode active material is 539 mAh / g.

[0064] Example 5 This embodiment provides a lithium-ion battery cell, which is basically the same as that in Embodiment 1. The main difference is the adjustment of the silicon-based material. The negative electrode active material in this embodiment includes silicon suboxide and graphite in a mass ratio of 9:91. The silicon content in the negative electrode active material is the same as that in Embodiment 1. The specific capacity of the negative electrode active material is 539 mAh / g.

[0065] Example 6 This embodiment provides a lithium-ion battery cell, which is basically the same as that in Embodiment 1. The main difference is the adjustment of the type of lithium-rich manganese-based cathode material. In this embodiment, the lithium-rich manganese-based cathode material is 0.4Li2MnO3. 0.6LiNi 0.5 Co 0.2 Mn 0.3 O2.

[0066] Example 7 This embodiment provides a lithium-ion battery cell, which is basically the same as that in Embodiment 1, except that the battery casing material is adjusted to be nickel-plated steel strip SPCE.

[0067] Example 8 This embodiment provides a lithium-ion battery cell. A positive electrode, a negative electrode, a separator, and an electrolyte are prepared according to Example 1. The battery cell assembly includes: In a dry and clean workshop with a dew point ≤-40℃ and humidity ≤10ppm, positive electrode plates / separators / negative electrode plates / separators are stacked alternately in the following order. The separators completely isolate the positive and negative electrodes and prevent short circuits. After stacking, the cells are shaped, bundled, and pressed to obtain stacked bare cells. The tabs of the bare cells are ultrasonically welded firmly to the aluminum-plastic film lead-out terminals. The bare cells are then placed in a three-layer aluminum-plastic film soft-pack shell, and the three sides are heat-sealed. The encapsulated cells are then placed in a vacuum oven at 85℃ for 24 hours to thoroughly remove internal moisture and residual solvents, controlling the moisture content of the cells to ≤10ppm. In an argon glove box (water and oxygen <1ppm), electrolyte is injected, formation is performed, and capacity testing is conducted to obtain a stacked battery. The dimensions of the stacked battery are 14.5mm × 100mm × 300mm.

[0068] Example 9 This embodiment provides a lithium-ion battery cell, which is basically the same as that in Embodiment 1. The main difference is the adjustment of the positive electrode tab. The positive electrode tab is a non-full tab (traditional single tab structure) integrally punched from the blank area of ​​the positive electrode current collector.

[0069] Example 10 This embodiment provides a battery module, which includes 6 lithium-ion battery cells; the lithium-ion battery cells are the same as those in Embodiment 1.

[0070] Thermally conductive silicone adhesive is encapsulated between adjacent lithium-ion battery cells to form an adhesive layer that connects the adjacent lithium-ion battery cells.

[0071] Comparative Example 1 This comparative example provides a lithium-ion battery that is basically the same as that in Example 1, except that the type of positive electrode material is adjusted. The positive electrode material in this comparative example is lithium iron phosphate (LFP).

[0072] Comparative Example 2 This comparative example provides a lithium-ion battery that is basically the same as that in Example 1, except that the type of cathode material is adjusted. The cathode material in this comparative example is lithium nickel cobalt manganese oxide (NCM811).

[0073] Comparative Example 3 This comparative example provides a lithium-ion battery that is basically the same as Example 1, except that the mass ratio of silicon carbon to graphite is adjusted to 100:0 (the negative electrode active material does not contain graphite), so that the silicon content in the negative electrode active material is 12wt% and the specific capacity of the negative electrode active material is 728mAh / g.

[0074] Comparative Example 4 This comparative example provides a lithium-ion battery that is basically the same as that in Example 1. The main difference is that the mass ratio of silicon-carbon to graphite is adjusted to 17:83, so that the silicon content in the negative electrode active material is 2wt% and the specific capacity of the negative electrode active material is 413mAh / g.

[0075] Test Example 1 This test case provides the performance tests and results of lithium-ion batteries from Examples 1-10 and Comparative Examples 1-4, as detailed below: The energy density test method is as follows: The energy density of a single cell at room temperature is determined according to the test method specified in GB / T 31486-2024 "Electrical Performance Requirements and Test Methods for Power Batteries for Electric Vehicles". Specifically, it includes: (1) Measuring the cell mass: At 25℃, the cell mass is measured using an electronic balance. The average value is taken after 3 tests and recorded as m, in kg; (2) The cell is left to stand at 25℃ for 60 min, and then charged to 4.2V at 1 / 3C constant current and constant voltage, with a cutoff current of 0.05C; (3) The cell is left to stand at 25℃ for 30 min; (4) The cell is discharged to 2.5V at 1 / 3C constant current at 25℃, and the discharge energy E1 is recorded; (5) Steps (2)-(4) are repeated three times, and the discharge energies E2 and E3 are recorded respectively. The average value of these three discharge energies is calculated and recorded as E, in Wh; (6) The energy density is calculated according to the formula: Energy density Em = E / m; where Em is the cell mass energy density, in Wh / kg; E represents the discharge energy, measured in Wh; m represents the cell mass, measured in kg.

[0076] Test method for internal resistance: Refer to the FreedomCAR manual to test and calculate the discharge DC internal resistance, specifically including: (1) stand at 25℃ for 60min; (2) charge at 25℃ with 1 / 3C constant current and constant voltage to 4.2V, cut-off current 0.05C; (3) stand at 25℃ for 30min; (4) discharge at 25℃ with 1 / 3C constant current to 50%SOC; (5) stand at 25℃ for 30min, record the end voltage U0; (6) discharge at 25℃ with 4C constant current for 10s, record the end voltage U1; (7) Calculate: DC internal resistance DCIR = (U0-U1) / 4C for 10s discharge at 25℃ and 50%SOC.

[0077] Safety performance testing method: The heating test (single cell thermal abuse) method specified in GB 38031-2020 "Safety Requirements for Power Batteries for Electric Vehicles" shall be used. The fully charged cell shall be used as the test object. A programmable temperature chamber shall be used with a temperature control accuracy of ±2℃. The specific steps include: (1) the cell is placed in the temperature chamber; (2) the temperature chamber is heated to 130℃±2℃ at 5℃ / min; (3) the temperature is kept constant for 30min; (4) heating is stopped and the cell is allowed to cool naturally; (5) the cell is observed for 1h after cooling. The cell shall be observed to see if it catches fire or explodes throughout the process. If it does not catch fire or explode, it shall be considered as passing the safety performance test. If it catches fire or explodes, it shall be considered as failing the safety performance test.

[0078] Table 1 Test Results

[0079] Compared to Comparative Examples 1-2, the positive electrode active material of the embodiments of the present invention includes a lithium-rich manganese-based positive electrode material, which can significantly improve the energy density of the battery cell. Compared to Comparative Examples 3-4, the embodiments of the present invention regulate the silicon content in the negative electrode active material, which is beneficial for the battery to balance safety performance and energy density. In addition, the battery provided by the embodiments of the present invention also has low internal resistance, indicating good fast charging performance.

[0080] As seen in Example 9, the present invention further adjusts the positive and negative tabs of the battery to be all tabs, which is beneficial to further reduce the internal resistance of the battery and improve the fast charging performance.

[0081] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0082] The above description is merely a specific embodiment of the present invention, enabling those skilled in the art to understand or implement the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the present invention is not to be limited to the embodiments described herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A lithium-ion battery cell, characterized in that, The battery includes a battery casing and an electrode assembly housed inside the battery casing, the electrode assembly including a positive electrode and a negative electrode; The positive electrode sheet includes a positive electrode active material, which includes a lithium-rich manganese-based positive electrode material. The chemical formula of the lithium-rich manganese-based positive electrode material is xLi2MnO3·(1-x)LiMO2, wherein M includes at least one of Co, Mn, Ni, Cr, Fe, and Al, and x satisfies: 0 < x < 1. The negative electrode sheet includes a negative electrode active material, which is a silicon-based material, and the silicon content in the negative electrode active material is 3wt%-10wt%.

2. The lithium-ion battery cell according to claim 1, characterized in that, The positive electrode sheet includes a positive current collector and a positive active material layer disposed on at least one side of the positive current collector along its own thickness direction. The positive active material layer includes the positive active material, and the mass content of the positive active material in the positive active material layer is 10%-99%. And / or, the lithium-rich manganese-based cathode material includes at least one of aluminum-doped lithium-rich manganese-based cathode material, chromium-doped lithium-rich manganese-based cathode material, lithium-rich manganese nickel oxide cathode material, and lithium-rich manganese cobalt nickel oxide.

3. The lithium-ion battery cell according to claim 1 or 2, characterized in that, The negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer disposed on at least one side of the negative electrode current collector along its own thickness direction, wherein the negative electrode active material layer includes the negative electrode active material. And / or, the mass content of the negative electrode active material in the negative electrode active material layer is 90%-97%; And / or, the specific capacity of the negative electrode active material is 350mAh / g-4200mAh / g.

4. The lithium-ion battery cell according to any one of claims 1-3, characterized in that, The silicon-based material includes at least one of silicon, silicon-carbon, and silicon suboxide; And / or, the negative electrode active material further includes at least one of graphite, soft carbon, hard carbon, and lithium titanate.

5. The lithium-ion battery cell according to any one of claims 1-4, characterized in that, The battery housing is cylindrical and includes an outer shell, a bottom plate and a top cover connected to the two ends of the outer shell in the axial direction. The outer shell and the bottom plate are integrally formed, and the space formed by the outer shell, the bottom plate and the top cover is used to accommodate the electrode assembly.

6. The lithium-ion battery cell according to claim 5, characterized in that, The battery casing is made of nickel-plated steel strip; And / or, the height of the battery casing is 80mm-120mm; And / or, the inner diameter of the outer periphery shell is 44.5mm-45.6mm; And / or, the wall thickness of the outer shell is 0.4mm-1.5mm.

7. The lithium-ion battery cell according to any one of claims 1-6, characterized in that, The lithium-ion battery cell also includes a positive electrode tab and a negative electrode tab; The positive electrode tab is a full electrode tab; and / or, the negative electrode tab is a full electrode tab.

8. The lithium-ion battery cell according to any one of claims 1-7, characterized in that, The lithium-ion battery is at least one of 4680 cells, 2170 cells, and 18650 cells.

9. A battery module, characterized in that, The lithium-ion battery cell includes any one of claims 1-8.

10. The battery module according to claim 9, characterized in that, Two adjacent lithium-ion battery cells are connected by an adhesive layer.

11. A vehicle, robot, or intelligent device, characterized in that, It includes a lithium-ion battery cell as described in any one of claims 1-8 or a battery module as described in any one of claims 9-10.

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