Battery

Abstract

The invention provides a battery, the battery comprises a positive plate, a negative plate and a diaphragm, the positive plate comprises a positive current collector and a positive coating arranged on at least one side surface of the positive current collector, the positive coating comprises a positive active material and a solid electrolyte, the positive active material comprises a manganese element, the solid electrolyte comprises a titanium element, and the titanium element is a titanium element. The solid electrolyte comprises lithium titanium aluminum phosphate and / or lithium lanthanum titanate; based on the mass of the positive electrode coating, the weight ratio of the manganese element to the titanium element is (5-150): 1; the negative plate comprises a negative current collector and a negative coating arranged on the surface of at least one side of the negative current collector, the negative coating comprises a negative active substance, the negative active substance comprises graphite, the average particle size of the graphite is f [mu] m, the OI value of the negative plate is g, and f / g is larger than or equal to 0.06 and smaller than or equal to 1.5. The battery provided by the invention has excellent high / low temperature stability.

Description

Technical Field

[0001] This invention relates to the field of battery technology, and more particularly to a battery. Background Technology

[0002] Lithium-ion batteries are the core power source for new energy vehicles, and their performance directly affects the vehicle's range, safety, and lifespan. In high-temperature environments (such as during summer high-temperature conditions or fast charging), manganese (Mn) in the cathode material is prone to dissolution, leading to rapid capacity decay, shortened cycle life, and even the risk of thermal runaway. In low-temperature environments, the ion diffusion rate decreases significantly, internal resistance increases sharply, and high-rate discharge performance is severely affected.

[0003] To address battery stability issues caused by manganese leaching at high temperatures, current technologies typically employ methods such as coating the surface of the cathode material or introducing additives into the electrolyte. Coating the cathode material with oxide layers such as Al₂O₃ or MgO can suppress manganese leaching, but excessively thick coatings can hinder lithium-ion diffusion, reducing the rate performance of lithium-ion batteries. Adding film-forming additives such as FEC (fluoroethylene carbonate) forms a stable SEI film on the anode surface, helping to mitigate battery capacity decay caused by manganese leaching. However, side reactions between the electrolyte and the cathode material are difficult to completely suppress at high temperatures, and the problems of capacity decay, shortened high-temperature cycle life, and reduced low-temperature performance caused by manganese leaching remain fundamentally unresolved. Summary of the Invention

[0004] The present invention also provides a battery that, on the one hand, can improve the problems of capacity decay, shortened cycle life and increased interface impedance caused by the dissolution of manganese in the positive electrode material under high temperature conditions, and on the other hand, can promote the uniform diffusion of lithium ions in the positive electrode and reduce local lithium depletion, thereby improving the low temperature performance of the battery.

[0005] In detail: The present invention provides a battery comprising a positive electrode, a negative electrode, and a separator. The positive electrode includes a positive current collector and a positive electrode coating disposed on at least one side surface of the positive current collector. The positive electrode coating includes a positive electrode active material and a solid electrolyte. The positive electrode active material includes manganese and is selected from at least one of nickel-cobalt-manganese ternary materials, lithium manganese oxide, nickel-cobalt-manganese-aluminum quaternary materials, lithium manganese iron phosphate, and lithium manganese phosphate. The solid electrolyte includes titanium and is selected from lithium titanium aluminum phosphate and / or lithium lanthanum titanate. Based on the mass of the positive electrode coating, the weight ratio of manganese to titanium is (5~150):1.

[0006] The negative electrode sheet includes a negative electrode current collector and a negative electrode coating disposed on at least one side of the surface of the negative electrode current collector. The negative electrode coating includes a negative electrode active material, which includes graphite. The average particle size of the graphite is f μm. The OI value of the negative electrode sheet is g, and f and g satisfy: 0.06≤f / g≤1.5.

[0007] In an optional embodiment, the content of manganese in the positive electrode active material is 20,000 ppm to 400,000 ppm, based on the mass of the positive electrode coating; preferably 50,000 ppm to 300,000 ppm.

[0008] And / or, based on the quality of the positive electrode coating, the content of titanium in the solid electrolyte is 2000ppm to 100000ppm, preferably 4000ppm to 80000ppm.

[0009] In an alternative implementation, f and g satisfy: 0.1 ≤ f / g ≤ 0.9;

[0010] Preferably, 0.8≤f≤8, 4≤g≤20; more preferably, 1.2≤f≤6, 6≤g≤15.

[0011] In an optional embodiment, the average particle size of the positive electrode active material is a μm, and the average particle size of the solid electrolyte is b μm, wherein a and b satisfy: 10≤a / b≤300;

[0012] And / or, the specific surface area of ​​the positive electrode active material is c m² / g, and a and c satisfy: 0.05≤a / c≤8.

[0013] In one alternative embodiment, 0.8 ≤ a ≤ 30, 0.05 ≤ b ≤ 0.8; more preferably, 2 ≤ a ≤ 20, 0.1 ≤ b ≤ 0.5.

[0014] In one alternative embodiment, 2.8 ≤ c ≤ 38, and more preferably, 3.5 ≤ c ≤ 30.

[0015] In an alternative embodiment, the surface of the positive electrode active material has a coating layer containing zirconium.

[0016] In an optional embodiment, the elongation of the positive current collector is d%, and the thickness of the positive current collector is e μm, where d and e satisfy: 1.5 ≤ e / d ≤ 6; preferably: 1.8 ≤ e / d ≤ 3.6;

[0017] And / or, 15≤e / b≤180; preferably: 25≤e / b≤120.

[0018] In an optional embodiment, the tensile strength of the positive current collector is x MPa, where x and e satisfy: 8 ≤ x / e ≤ 35.

[0019] In an optional embodiment, d satisfies: 3≤d≤7, preferably: 4≤d≤6.5;

[0020] And / or, the e satisfies: 8≤e≤20, preferably: 10≤e≤15;

[0021] And / or, the x satisfies: 150≤x≤300.

[0022] In an alternative implementation, f and g satisfy: 0.1 ≤ f / g ≤ 0.9;

[0023] Preferably, 0.8≤f≤8, 4≤g≤20; more preferably, 1.2≤f≤6, 6≤g≤15.

[0024] In an optional embodiment, the battery further includes a separator comprising a base film and a coating disposed on at least one surface of the base film, the coating being disposed on the side of the base film facing the positive electrode, the coating comprising organic particles, the organic particles comprising at least one of 1,3,5-triazine-2,4,6-triamine, melamine cyanurate, melamine thiocyanate, 2,3-dicyanopyrazine, and symmetrical triaminotriazine;

[0025] Preferably, the organic particles in the coating have a mass content of 50 wt% to 95 wt%;

[0026] In an optional embodiment, the porosity of the separator is h%, the porosity of the positive electrode is i%, and h and i satisfy: 0.5≤h / i≤3, preferably 0.9≤h / i≤2.1;

[0027] Preferably, 30≤h≤80, 25≤i≤60; more preferably, 35≤h≤65, 30≤i≤50.

[0028] The battery of this invention, by incorporating a solid electrolyte into the positive electrode coating, can compensate for the uneven lithium-ion insertion / extraction phenomenon that occurs in the positive electrode active material during cycling. Simultaneously, a good interfacial contact is formed between the solid electrolyte and the positive electrode active material, promoting uniform diffusion of lithium ions in the positive electrode material, reducing local lithium depletion, and improving the battery's low-temperature performance. Furthermore, by limiting the ratio of manganese and titanium, the lattice matching between the solid electrolyte and the active material can be optimized. The solid electrolyte material compensates for lithium-ion losses in the positive electrode material, mitigating the battery capacity decay problem caused by the dissolution of Mn from the positive electrode active material under high-temperature conditions. At the same time, by adjusting the graphite particle size and OI value ratio of the negative electrode, the lithium-ion insertion / extraction rate in the positive and negative electrodes can be further balanced, thereby synergistically improving the low-temperature performance of the battery. Detailed Implementation

[0029] To enable those skilled in the art to better understand the present invention, the present invention will be further described in detail below. The specific embodiments listed below are merely descriptions of the principles and features of the present invention, and the examples are only for explaining the present invention and are not intended to limit the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0030] In this application, the terms "first" and "second" are used for descriptive purposes only, to distinguish objects, such as substances, from one another, and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. For example, without departing from the scope of the embodiments of this application, "first XX" may also be referred to as "second XX," and similarly, "second XX" may also be referred to as "first XX." Thus, features defined with "first" and "second" may explicitly or implicitly include one or more of that feature.

[0031] In this application, references to "an embodiment," "an example," or "an example" mean that a specific feature, structure, or characteristic described in connection with that embodiment, example, or example is included in at least one embodiment of the invention. Therefore, the phrases "an embodiment," "an example," "an example," "an example," or "an example" appearing in various places throughout the specification do not necessarily refer to the same embodiment or example. Furthermore, specific features, structures, or characteristics can be combined in one or more embodiments or examples in any suitable combination and / or sub-combination.

[0032] The cathode material for lithium-ion batteries often uses manganese-containing composite oxides (such as LiMn2O4, LiNi). x Mn x Co 1-2xThe structural stability of lithium (such as O2) is closely related to the content of manganese. Manganese is prone to dissolution under high temperature conditions. Specifically, during charge-discharge cycles, manganese ions (Mn²⁺) are extracted from the lattice of the positive electrode material, enter the electrolyte, and deposit on the surface of the negative electrode, which destroys the stability of the negative electrode SEI film, leading to irreversible consumption of lithium ions and capacity decay.

[0033] Existing technologies use surface coating and electrolyte additives to mitigate the negative effects of manganese leaching. However, even with surface coating and electrolyte additives, the degradation of the cathode material structure caused by manganese leaching remains significant under high-temperature conditions.

[0034] To address the shortcomings of existing technologies, this application, through the design of positive and negative electrode materials and interface optimization, suppresses the dissolution of manganese ions from the positive electrode material, prevents their deposition on the negative electrode and subsequent SEI film damage, and maintains a balance between lithium-ion transport efficiency and interface impedance, thereby simultaneously improving the high / low temperature performance of the battery. Specifically, this application provides the following technical solutions:

[0035] This invention provides a battery comprising a positive electrode, a negative electrode, and a separator. The positive electrode includes a positive current collector and a positive electrode coating disposed on at least one side of the positive current collector. The positive electrode coating includes a positive active material and a solid electrolyte. The positive active material includes manganese and is selected from at least one of nickel-cobalt-manganese ternary materials, lithium manganese oxide, nickel-cobalt-manganese-aluminum quaternary materials, lithium manganese iron phosphate, and lithium manganese phosphate. The solid electrolyte includes titanium and is selected from lithium titanium aluminum phosphate and / or lithium lanthanum titanate. Based on the mass of the positive electrode coating, the weight ratio of manganese to titanium is (5~150):1.

[0036] The negative electrode sheet includes a negative electrode current collector and a negative electrode coating disposed on at least one side of the surface of the negative electrode current collector. The negative electrode coating includes a negative electrode active material, which includes graphite. The average particle size of the graphite is f μm. The OI value of the negative electrode sheet is g, and f and g satisfy: 0.06≤f / g≤1.5.

[0037] Solid electrolytes possess high lithium-ion conductivity. The battery of this invention, by incorporating a solid electrolyte into the positive electrode coating, can compensate for the uneven lithium-ion insertion / extraction phenomenon occurring in the positive electrode active material during cycling. Simultaneously, a good interfacial contact is formed between the solid electrolyte and the positive electrode active material, promoting uniform diffusion of lithium ions within the positive electrode material, reducing localized lithium depletion, and improving the battery's low-temperature performance. Furthermore, by limiting the ratio of manganese and titanium, an excellent ion transport network can be constructed, buffering the interfacial stress caused by changes in the lattice volume of the positive electrode active material. The solid electrolyte material compensates for lithium-ion loss in the positive electrode material, mitigating the battery capacity decay problem caused by the dissolution of Mn elements from the positive electrode active material under high-temperature conditions. Moreover, further optimizing the graphite particle size and OI value ratio of the negative electrode can further balance the lithium-ion insertion / extraction rates in the positive and negative electrodes, thereby synergistically improving the battery's low-temperature performance.

[0038] When the weight ratio of manganese to titanium is less than 5:1, the low manganese content may cause lattice distortion or phase transition during charging and discharging, thus reducing its structural stability. The high titanium content may reduce the mobility of lithium ions in its lattice, thus affecting its lithium ion transport capacity as a solid electrolyte. The combined effect of insufficient lithium ion replenishment and decreased structural stability leads to accelerated capacity decay of the cathode material during charging and discharging, seriously affecting the rate performance and lifespan of the battery. When the weight ratio of manganese to titanium is greater than 150:1, the high manganese content may also cause lattice distortion or phase transition during cycling, thus reducing its structural stability. The low titanium content may cause its lattice parameters to be mismatched with the cathode material, thus affecting the interface contact quality, increasing interface impedance, and further affecting the battery's cycle capacity.

[0039] When f / g is less than 0.06, the excessively small graphite particle size results in an excessively large specific surface area. This increases the contact area with the electrolyte during battery charging and discharging, leading to side reactions that consume more lithium ions and increase the battery's irreversible capacity. Conversely, an excessively large OI value in the negative electrode hinders the diffusion channels of lithium ions between graphite layers, increasing lithium ion transport resistance and reducing the battery's rate charge / discharge capability. When f / g is greater than 1.5, the excessively large graphite particle size significantly prolongs the lithium ion diffusion path within the particles, increasing the diffusion time of lithium ions within the particles and severely limiting the battery's charge / discharge capability. An excessively small OI value in the negative electrode results in more end faces available for active ion insertion, leading to more exposed active sites in the particles, further accelerating lithium ion loss and severely affecting the battery's cycle life. By controlling f / g within a specific range, it is possible to ensure a high lithium ion transport rate while reducing side reactions between the negative electrode active material and the electrolyte, enabling the battery to achieve both high and low temperature performance and long cycle life.

[0040] In some embodiments, the method for testing the OI value of the negative electrode is as follows: X-ray diffraction (XRD) technology is used to analyze the crystal structure of the graphite material to evaluate its orientation, and the intensity ratio of the (004) crystal plane diffraction peak to the (110) crystal plane diffraction peak is measured, OI=I(004) / I(110), thereby calculating the OI value.

[0041] By way of example and not limitation, in some embodiments, the positive electrode active material includes, but is not limited to, at least one of: nickel-cobalt-manganese ternary materials, lithium manganese oxide, nickel-cobalt-manganese-aluminum quaternary materials, lithium manganese iron phosphate, and lithium manganese phosphate. Exemplarily, the nickel-cobalt-manganese ternary material may be LiNi... 1 / 3 Co 1 / 3 Mn 1 / 3 O2, LiNi 0.5 Co 0.2 Mn 0.3 O2, LiNi 0.6 Co 0.2 Mn 0.2 O2, LiNi 0.8 Co 0.1 Mn 0.1 One or more of O2.

[0042] In one specific embodiment, the solid electrolyte includes at least one of lithium aluminum titanium phosphate (LATP) and lithium lanthanum titanate (LLTO).

[0043] In one specific embodiment, the weight ratio of manganese to titanium is (10~70):1. When the battery of the above embodiment is used, the mixed solid electrolyte particles and the positive electrode active material form a compatible contact at the microscopic interface, which further promotes the uniform diffusion of lithium ions in the positive electrode material, and at the same time improves the problem of battery capacity decay caused by the dissolution of Mn element in the positive electrode active material under high temperature conditions, thereby further optimizing the high temperature stability of the battery.

[0044] For example, the weight ratio of manganese to titanium is any one of 10:1, 20:1, 30:1, 40:1, 50:1, 60:1, 70:1, etc.

[0045] In some embodiments, the average particle size of the graphite particles can be obtained by measuring the particle size of any 100 graphite particles in an SEM image of the negative electrode active layer surface, and averaging these values ​​as the average particle size. It should be noted that if more than 100 particles are observed in the captured image, the average number of any 100 particles in that image is taken as the average particle size of the graphite particles; if no 100 particles are observed in the image, multiple images are captured, and the average number of all 100 particles is taken as the average particle size of the graphite particles. The SEM images can be obtained using a scanning electron microscope (S-3400N, manufactured by Hitachi, Ltd.).

[0046] In some implementations, the content of elements can be tested using scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS).

[0047] In one specific embodiment, the manganese content in the positive electrode active material is 20,000 ppm to 400,000 ppm, depending on the quality of the positive electrode coating.

[0048] The manganese content within the above range helps to further stabilize the crystal structure of the cathode material, reducing structural damage caused by lithium-ion insertion / extraction during charging and discharging, thereby further improving the high-temperature stability and safety of the battery. As a further preferred option, the manganese content in the active material is 50,000 ppm to 300,000 ppm.

[0049] For example, the manganese content in the positive electrode active material is any value or a range of any two of the following: 20,000 ppm, 30,000 ppm, 40,000 ppm, 50,000 ppm, 60,000 ppm, 70,000 ppm, 80,000 ppm, 90,000 ppm, 100,000 ppm, 200,000 ppm, 300,000 ppm, 400,000 ppm.

[0050] As an example and not a limitation, f / g = any value of 0.06, 0.08, 0.1, 1.2, 1.5, or a range of any two of these values.

[0051] In some embodiments, 0.1 ≤ f / g ≤ 0.9.

[0052] In some embodiments, 0.8≤f≤8, 4≤g≤20, more preferably, 1.2≤f≤6, 6≤g≤15.

[0053] As an example and not a limitation, f = any value or any combination of two of the following: 0.8, 1, 2, 3, 4, 5, 6, 7, 8, etc.; g = any value or any combination of two of the following: 4, 6, 8, 10, 12, 14, 16, 18, 20, etc.

[0054] In one specific embodiment, the titanium content in the solid electrolyte is 2000ppm to 100000ppm, depending on the quality of the positive electrode coating.

[0055] The titanium content within the above range can further improve the formation of good interfacial contact between the solid electrolyte and the positive electrode active material, promote the uniform diffusion of lithium ions in the positive electrode material, and at the same time compensate for the capacity decay problem caused by the dissolution of Mn in the positive electrode material under high temperature conditions. As a further preferred option, the titanium content in the solid electrolyte is 4000ppm~80000ppm.

[0056] For example, the titanium content in the solid electrolyte is any value or a range of any two of the following: 2000 ppm, 5000 ppm, 10000 ppm, 25000 ppm, 50000 ppm, 70000 ppm, 80000 ppm, 90000 ppm, 100000 ppm.

[0057] In one specific embodiment, the average particle size of the positive electrode active material is a μm, and the average particle size of the solid electrolyte is b μm, wherein a and b satisfy: 10 ≤ a / b ≤ 300.

[0058] When a and b satisfy the above relationship, it helps accelerate lithium-ion conduction and further improves the battery's low-temperature performance. When a / b is less than 10, the interfacial contact area between the positive electrode active material and the solid electrolyte decreases, resulting in increased interfacial impedance. Simultaneously, excessively large solid electrolyte particles lengthen the diffusion path of lithium ions within the electrolyte, leading to increased polarization and minimal improvement in the battery's low-temperature performance. Furthermore, excessively small active material particles are more prone to lattice distortion during cycling, accelerating capacity decay. When the average particle size ratio of the positive electrode active material to the solid electrolyte is greater than 300, the mismatch in interfacial contact area between the excessively large positive electrode active material and the excessively small solid electrolyte leads to increased interfacial impedance. Simultaneously, excessively large positive electrode active material lengthens the diffusion path of lithium ions within the positive electrode material, potentially causing increased polarization and affecting the battery's low-temperature performance and energy density improvement.

[0059] For example, a / b = any value or a range of any two of the following: 10, 15, 20, 30, 50, 90, 100, 150, 200, 250, 300, etc.

[0060] In one specific embodiment, 0.8 ≤ a ≤ 30, 0.08 ≤ b ≤ 0.8; preferably, 2 ≤ a ≤ 20, 0.1 ≤ b ≤ 0.5. Exemplarily, a = any value or a range of any two of the following: 0.8, 1.2, 5, 10, 12, 15, 17, 20, 22, 25, 27, 30; b = any value or a range of any two of the following: 0.08, 0.1, 0.2, 0.5, 0.7, 0.8.

[0061] In one specific embodiment, the specific surface area of ​​the positive electrode active material is c m² / g, and a and c satisfy: 0.05≤a / c≤8.

[0062] When a and c satisfy the above relationship, the diffusion path and charge transfer efficiency of lithium ions in the cathode material can be optimized, further improving the low-temperature charge and discharge capability of the battery; at the same time, it can reduce the volume change and structural damage of the cathode material during cycling, further extending the high-temperature cycle life of the battery.

[0063] When a / c is less than 0.05, it indicates an increase in active sites on the surface of the positive electrode material, making it prone to side reactions with the electrolyte. These surface side reactions and structural instability lead to pulverization and degradation of the material during cycling, affecting the improvement of the battery's high-temperature cycling stability. When a / c is greater than 8, the excessively large particle size of the positive electrode material results in a longer diffusion path for lithium ions within the positive electrode material, increasing the polarization effect and hindering low-temperature, high-rate charge and discharge. Simultaneously, the excessively small specific surface area indicates a reduced contact area between the electrode and the electrolyte, decreasing interfacial reaction efficiency and further affecting the improvement of the battery's low-temperature rate performance.

[0064] As an example and not a limitation, a / c = any value or a range of any two of the following: 0.05, 1, 3, 4, 6, 7, 8, etc.

[0065] In some embodiments, 2.8 ≤ c ≤ 3.8, more preferably, 3.5 ≤ c ≤ 30. By way of example and not limitation, c = any value or a range of any two of 2.8, 2.9, 3.0, 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, etc.

[0066] In some embodiments, the average particle size of the positive electrode active material and the average particle size of the solid electrolyte can be obtained by testing the following method: in the SEM image of the surface of the positive electrode active layer, for any 100 particles of positive electrode active material and solid electrolyte, the particle size of each particle is measured, and the average value of these particles is set as the average particle size.

[0067] In one specific embodiment, the surface of the positive electrode active material has a coating layer containing zirconium.

[0068] It is understandable that the coating layer is placed on the surface of the positive electrode active material, which can be part of the surface or cover the entire surface of the positive electrode active material.

[0069] The outer surface of the positive electrode active material includes a coating layer, which helps to suppress lattice distortion or crack propagation of the positive electrode material during cycling, improve the structural integrity of the positive electrode material, and reduce side reactions that occur when in contact with the electrolyte.

[0070] In one specific embodiment, the thickness of the coating layer is 0.01~0.15μm.

[0071] The coating thickness above helps to further optimize the lithium-ion transport path on the surface of the cathode material, improve ionic conductivity, reduce the interfacial impedance between the cathode material and the electrode, and further enhance the electrochemical performance of the battery.

[0072] As an example and not a limitation, the thickness of the coating is any value or a range of any two of the following: 0.01 μm, 0.12 μm, 0.13 μm, 0.14 μm, 0.15 μm.

[0073] In one specific embodiment, the thickness of the coating layer is 0.02-0.1 μm.

[0074] In one specific embodiment, the elongation of the positive current collector is d%, and the thickness of the positive current collector is e μm, where d and e satisfy: 1.5≤e / d≤6.

[0075] Meeting the above conditions for e / d helps to further reduce the risk of structural failure of the battery during cycling, reduce interface failure during cycling, and extend battery life.

[0076] When e / d is less than 1.5, insufficient current collector thickness leads to inadequate electron transport paths, affecting the overall conductivity of the battery and increasing its internal resistance. Conversely, excessive elongation results in a loose bond between the current collector and the active material layer, creating voids, increasing interfacial impedance, and hindering the improvement of the battery's low-temperature rate performance. When e / d is greater than 6, excessive current collector thickness increases the proportion of inactive materials, reducing the overall energy density of the battery. Conversely, insufficient elongation is accompanied by increased brittleness, causing the current collector to break during encapsulation or use, reducing battery life.

[0077] As an example, not a limitation, e / d = any value of 1.5, 2, 3, 4, 5, 6, etc., or a range of any two of them.

[0078] In one specific implementation, 1.8 ≤ e / d ≤ 3.6.

[0079] To further enhance battery stability, in one specific embodiment, the tensile strength of the positive electrode current collector is x MPa, where x and e satisfy: 8 ≤ x / e ≤ 35.

[0080] If x / e meets the above conditions, the toughness of the positive electrode current collector can be increased, ensuring that the current collector is not easily broken during the packaging process and reducing the risk of structural failure of the battery during cycling.

[0081] In one specific implementation, 12 ≤ e / x ≤ 26.

[0082] In one specific implementation, 15 ≤ e / b ≤ 180.

[0083] Meeting the above e / b conditions helps to further reduce the transport path length of lithium ions between the positive electrode and the solid electrolyte, improve transport efficiency, help to form a more uniform interface contact, reduce interface voids and impedance, thereby further improving the battery's low-temperature rate performance and high-temperature cycling capability.

[0084] When the ratio of the cathode current collector thickness *e* to the average particle size *b* of the solid electrolyte is less than 15, the excessively small thickness of the cathode current collector may lead to insufficient electron transport paths, affecting the overall conductivity of the battery and increasing internal resistance. Conversely, excessively large solid electrolyte particle size hinders the diffusion of lithium ions between the cathode and the electrolyte, reducing transport efficiency and exacerbating polarization, further affecting the improvement of the battery's low-temperature rate performance. When the ratio of the cathode current collector thickness *e* to the average particle size *b* of the solid electrolyte is greater than 180, the excessively large current collector thickness increases the proportion of inactive materials, reducing the overall energy density of the battery. Conversely, excessively small particle size leads to an uneven interface between the solid electrolyte and the current collector, increasing interface impedance, accelerating the decay of the positive electrode active material, causing interface failure, and shortening the battery's high-temperature cycle life.

[0085] The tensile strength of the positive electrode current collector can be tested using an electronic tensile testing machine to measure the stress of the material before fracture. Elongation can be calculated by measuring the elongation of the material at fracture during the tensile test. Both tests reference standards: ASTM D638 / GB / T 1040.2.

[0086] In one specific implementation, 25 ≤ e / b ≤ 120.

[0087] In one specific implementation, d satisfies: 3≤d≤7, preferably: 4≤d≤6.5.

[0088] In one specific implementation, e satisfies: 8≤e≤20, preferably: 10≤e≤15.

[0089] In one specific implementation, x satisfies: 150≤x≤300.

[0090] In an optional embodiment, the negative electrode sheet includes a negative electrode current collector and a negative electrode coating disposed on at least one side surface of the negative electrode current collector, the negative electrode coating comprising the aforementioned graphite. Regarding the material of the aforementioned negative electrode current collector, the present invention does not specifically limit it; for example, it may be selected from any one or more of copper foil, titanium foil, tin foil, chromium foil, and composite foils of the above metals.

[0091] In a preferred embodiment, the negative electrode coating further includes a conductive agent, a binder, and a dispersant, excluding graphite. Exemplarily, the conductive agent may be selected from at least one of carbon black, acetylene black, Ketjen black, carbon fiber, carbon nanotubes, metal powder, and graphene; the binder may be selected from at least one of carboxymethyl cellulose, styrene-butadiene rubber, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene oxide-containing polymers, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyamide-imide, polyvinyl alcohol, and sodium polyacrylate; and the dispersant may be selected from at least one of sodium carboxymethyl cellulose, triethylhexyl phosphate, and sodium dodecyl sulfate.

[0092] The battery also includes a separator, which includes a base film and a coating disposed on at least one side of the base film. The coating is disposed on the side of the base film facing the positive electrode. The coating includes organic particles, which include at least one of 1,3,5-triazine-2,4,6-triamine, melamine cyanurate, melamine thiocyanate, 2,3-dicyanopyrazine, and symmetrical triaminotriazine.

[0093] The above-mentioned organic particles can block the migration of dissolved manganese ions. Specifically, the nitrogen atom (N) in the molecular structure of the organic particles has a lone pair of electrons. When Mn ions migrate from the positive electrode to the negative electrode, they coordinate with the nitrogen atom through the membrane, forming a stable coordinate bond and preventing them from migrating further to the negative electrode side. Additionally, the carbonyl oxygen atom (O=C-) also has a lone pair of electrons, and multiple N and O atoms can simultaneously coordinate with a single Mn atom. 2+ Ion coordination forms one or more stable five-membered or six-membered ring chelate structures, which capture free Mn ions on the membrane surface and prevent them from migrating further to the negative electrode surface and damaging the negative electrode SEI membrane.

[0094] In some embodiments, the coating further includes an adhesive such as polyvinylidene fluoride (PVDF) and / or polymethyl methacrylate (PMMA).

[0095] In some embodiments, at least one side of the coating faces the positive electrode side. Applying a coating containing organic particles to the side facing the positive electrode can promptly capture Mn ions dissolved from the positive electrode active material, preventing metal ions from damaging the negative electrode, reducing the risk of negative electrode SEI instability, internal short circuits, or gas generation caused by Mn deposition, and improving the battery's cycle life, especially its high-temperature cycle life.

[0096] In some embodiments, the base film comprises polypropylene and / or polyethylene.

[0097] In one specific embodiment, the organic particles in the coating have a mass content of 50 wt% to 95 wt%. This range of organic particle content in the coating helps to balance the relative equilibrium between lithium ion transport and the inhibition of manganese dissolution and migration. By way of example and not limitation, the organic particle content in the coating can be any value from 50 wt%, 60 wt%, 70 wt%, 80 wt%, 90 wt%, 95 wt%, or a range of any combination thereof.

[0098] In one specific embodiment, the battery further includes an electrolyte with a viscosity not greater than 5 mPa•s.

[0099] Electrolytes with the above viscosities can improve electrolyte conductivity, accelerate lithium-ion transport rate, reduce concentration polarization, and help improve the rate performance and low-temperature performance of lithium-ion batteries.

[0100] The viscosity of the electrolyte was measured using a Fluidicam microfluidic visual rheometer from Formulaction, France.

[0101] In some embodiments, the electrolyte comprises an organic solvent and a lithium salt. The organic solvent includes one or more of dimethyl carbonate, methyl acetate, ethyl propionate, ethyl acetate, and other ester solvents. The organic solvent content in the electrolyte is 10 wt% to 60 wt%. These organic solvents are characterized by low viscosity, which can accelerate lithium-ion transport rates at low temperatures and improve the low-temperature performance of the battery. By way of example and not limitation, the organic solvent content in the electrolyte is any value or a range of any combination of 10 wt%, 20 wt%, 30 wt%, 40 wt%, 50 wt%, 60 wt%, etc.

[0102] In some embodiments, the lithium salt serves as the ion source and can be a lithium salt known in the art for use in battery electrolytes. Exemplarily, the lithium salt can be lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium hexafluoroantimonyate (LiSbF6), lithium difluorophosphate (LiPF2O2), lithium 4,5-dicyano-2-trifluoromethylimidazolium (LiDTI), lithium dioxoborate (LiBOB), lithium trifluoromethanesulfonate (LiTFS), lithium bis(malonic acid)borate (LiBMB), lithium difluorooxalate borate (LiDFOB), etc. Lithium borate (LiBDFMB), lithium borate (LiMOB), lithium borate (LiDFMOB), lithium tri(oxalate) phosphate (LiTOP), lithium tri(difluoromalonate) phosphate (LiTDFMP), lithium tetrafluorooxalate phosphate (LiTFOP), lithium difluorodioxalate phosphate (LiDFOP), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium (fluorosulfonyl)(trifluoromethanesulfonyl)imide (LiN(SO2F)(SO2CF3)), lithium nitrate (LiNO3), lithium fluoride (LiF), LiN(SO2RF)2 or LiN(SO2F)(SO2RF), wherein RF = CnF 2n+1 n is 2-10 and is an integer.

[0103] In some embodiments, the electrolyte includes fluoroethylene carbonate (FEC), with the FEC content ranging from 5 wt% to 20 wt% based on the total mass of the electrolyte. Controlling the FEC content within this range allows the FEC to form a dense SEI film on the negative electrode surface even in the later stages of long-cycle operation, suppressing the damage of transition metal ions to the negative electrode, improving protection of the negative electrode, and further enhancing the battery's long-cycle performance.

[0104] In some embodiments, the total content of easily gas-generating components in the organic solvent, such as ethylene carbonate (EC) and fluoroethylene carbonate (FEC), is controlled to be below 30%, which helps to reduce the amount of gas generated by the battery under high temperature or overcharge conditions and improve the battery life at high temperatures.

[0105] In some embodiments, the viscosity of the electrolyte is not greater than 3.5 mPa•s.

[0106] In one specific embodiment, the porosity of the separator is h%, the porosity of the positive electrode is i%, and h and i satisfy: 0.5≤h / i≤3.

[0107] When h / i meets the above conditions, the ion transport capability of the positive electrode is faster, which is beneficial to improving the rate performance of lithium-ion batteries.

[0108] When h / i is less than 0.5, excessive porosity of the positive electrode leads to a longer electron transport path, increasing the electron transport resistance of the electrode and thus increasing the internal resistance of the battery. Insufficient separator porosity restricts the lithium-ion transport channels, increasing the resistance to ion diffusion and further increasing the internal resistance of the battery, severely affecting its rate performance. When h / i is greater than 3, insufficient positive electrode porosity restricts the wettability of the electrolyte, reducing the lithium-ion transport channels in the electrode and leading to decreased lithium-ion diffusion efficiency, affecting the battery's low-temperature discharge capability. Furthermore, insufficient porosity also increases internal stress in the electrode, preventing buffering of the volume expansion of the active material during charging and discharging, thus accelerating particle breakage and shedding, ultimately shortening the battery's cycle life. Excessive separator porosity reduces its thermal stability, thereby accelerating the high-temperature storage and cycle performance of the lithium-ion battery.

[0109] The porosity of the positive electrode and the separator can be tested using conventional methods in the art, such as by measuring the porosimetry using a Micron AutoPore V 9600 mercury porosimeter.

[0110] As an example and not a restriction, h / i = any value of 0.5, 0.7, 1.2, 1.5, 2, 2.5, 3, etc., or a range of any two of them.

[0111] In some embodiments, 0.9 ≤ h / i ≤ 2.1.

[0112] In some embodiments, 30≤h≤80, 25≤i≤60.

[0113] In some embodiments, more preferably, 35≤h≤65 and 30≤i≤50.

[0114] As an example, not a limitation, h = any value or a range of any two of the following: 35, 40, 45, 50, 60, 65, etc. i = any value or a range of any two of the following: 30, 35, 40, 45, 50, etc.

[0115] The above-mentioned positive electrode, separator and negative electrode can be stacked in sequence to obtain a battery cell, or the above-mentioned positive electrode, separator and negative electrode can be stacked in sequence and then wound to obtain a battery cell; the battery cell is placed in a battery packaging film shell (such as an aluminum-plastic film shell), electrolyte is injected into the outer packaging and sealed to prepare the battery of the present invention.

[0116] The aluminum-plastic film shell has a tensile strength of 100~250 MPa, which can better withstand the mechanical stress caused by volume changes during battery charging and discharging, and helps to improve battery expansion.

[0117] The test method for the tensile strength of aluminum-plastic film is as follows: Using an electronic tensile testing machine, the aluminum-plastic film sample disassembled from the battery is subjected to a tensile speed of 50 mm / min until the sample breaks. The tensile strength (MPa) is then calculated as the ratio of the maximum tensile force (N) to the cross-sectional area (mm²) of the aluminum-plastic film sample. 2 The ratio of ).

[0118] The present invention will be further described below with reference to specific embodiments:

[0119] Example 1

[0120] (1) Preparation of positive electrode

[0121] Li 1.3 Al 0.3 Ti 1.7 (PO4)3, positive electrode active material NCM523, binder PVDF, and conductive carbon black are mixed by stirring to form a homogeneous and stable mixture. The solid component of this mixture contains 1 wt% Li. 1.3 Al 0.3 Ti 1.7 (PO4)3, 92wt% positive electrode active material, 2wt% binder PVDF, and 5wt% conductive carbon black were used as solvent to prepare a positive electrode active material slurry with a solid content of 63wt%. The slurry was uniformly coated on both sides of an aluminum foil, dried, and compacted by a roller press to obtain a positive electrode sheet including the aluminum foil and the positive electrode coating placed on both sides of the current collector aluminum foil. The structural parameters of the positive electrode coating are shown in Table 1, the structural parameters of the current collector aluminum foil are shown in Table 2, and the positive electrode porosity is shown in Table 3.

[0122] (2) Preparation of negative electrode

[0123] The negative electrode active material graphite, binder SBR, and conductive agent are mixed and stirred to form a homogeneous and stable mixture. This mixture contains 95 wt% graphite G1, 3 wt% binder SBR, and 2 wt% conductive agent as solid components. A negative electrode active material slurry with a solid content of 46 wt% is prepared using water as a solvent. This slurry is uniformly coated on both sides of a copper foil, dried, and compacted using a roller press to obtain a negative electrode sheet comprising a current collector copper foil and a negative electrode coating on both sides of the copper foil; the structural parameters of the negative electrode coating are shown in Table 3.

[0124] (3) Battery assembly

[0125] Prepare a diaphragm, which consists of a polyethylene base membrane (7μm) and a coating on one side of the base membrane. The coating is composed of melamine cyanurate particles and PVDF, wherein the melamine cyanurate particles account for 70wt%. The structural parameters of the diaphragm are shown in Table 3.

[0126] The positive electrode, negative electrode, and separator laminations are wound / stacked to form a bare cell, which is then hot-pressed and welded with aluminum tabs and nickel-plated copper tabs. After perforation in the aluminum-plastic film, it is encapsulated and vacuum-baked at 95°C for 24 hours. The electrolyte used is a 1M lithium hexafluorophosphate electrolyte, with a solvent consisting of a 1:1:1 volume ratio of ethylene carbonate, dimethyl carbonate, and 1,2-propylene glycol carbonate, and an additive of 5% by mass. After electrolyte injection, the battery undergoes formation, secondary sealing, sorting, and OCV testing to obtain a soft-pack battery.

[0127] Example 2-28

[0128] The differences from Example 1 are shown in Tables 1-3, wherein the content of manganese and titanium is adjusted by regulating the mass ratio of active material and solid electrolyte.

[0129] Example 29

[0130] The only difference from Example 1 is that the diaphragm includes a polyethylene base film (7μm) and a coating on one side of the base film. The coating is composed of alumina ceramic particles and PVDF, wherein the alumina ceramic particles account for 70wt%.

[0131] Comparative Examples 1-4

[0132] The differences from Example 1 are shown in Tables 1-3, and the batteries are labeled D1, D2, D3, and D4 respectively.

[0133] Test case

[0134] 1) Cell rate test: Under (25±2)℃ environment, discharge at 1C standard constant current to discharge termination voltage 2.7V, and rest for 30min; then charge at 1C standard constant current and constant voltage to charging limit voltage 4.2V, cut-off current 0.05C, and rest for 30min; discharge at 1C standard constant current to discharge termination voltage 2.7V to obtain the actual cell capacity C0, and rest for 30min; charge at 1C standard constant current and constant voltage to charging limit voltage 4.2V, cut-off current 0.05C; after standing at (-20±2)℃ for 4h, discharge at a certain rate for 10s to discharge limit voltage 2.7V, and this rate is the cell discharge rate;

[0135] 2) Cell Cycle Test: Discharge at 45℃ using 3C standard constant current until the discharge termination voltage is 2.7V, and let stand for 30 minutes; then charge using 3C standard constant current and constant voltage until the charging limit voltage is 4.2V, the cutoff current is 0.05C, and let stand for 30 minutes; discharge using 3C standard constant current until the discharge termination voltage is 2.7V, and let stand for 30 minutes; repeat the above full charge and discharge steps until the capacity decays to 80% and then stops. The number of repeats is the cycle number, which is used to evaluate the cycle performance of the battery after aging.

[0136] 3) Cell energy density test: The weight of the lithium-ion battery after the second sealing process is recorded as the cell weight. The energy of the battery after being fully charged to 4.2V and then discharged to 2.7V after being left to stand for 5 minutes during the sorting process is recorded as the discharge energy. The ratio of the discharge energy to the cell weight is the cell energy density, with the unit being Wh / kg.

[0137] The test results are shown in Table 4.

[0138] Table 1:

[0139]

[0140] Table 2:

[0141]

[0142] Table 3:

[0143]

[0144] Table 4:

[0145]

[0146] Based on the data in Tables 1 to 4, it can be seen that, on the one hand, the batteries of the embodiments, by introducing a positive electrode active material containing manganese and a solid electrolyte containing titanium, and by limiting the weight ratio of manganese in the positive electrode active material and titanium in the solid electrolyte, not only can the uniform diffusion of lithium ions in the positive electrode material be improved, reducing local lithium depletion and thus improving the low-temperature performance of the battery, but the lattice matching between the solid electrolyte and the active material can also be optimized to compensate for the loss of lithium ions in the positive electrode material, thereby improving the high-temperature cycle performance of the battery. On the other hand, the positive electrode sheet is also matched with the graphite particle size and OI value ratio of the negative electrode, which can further balance the lithium ion insertion / extraction rate in the positive and negative electrodes, thereby synergistically improving the low-temperature performance of the battery with the positive electrode sheet. Specifically, compared with Comparative Examples 1-4, the batteries of Examples 1-29 exhibit higher low-temperature rate performance, high-temperature cycle performance, and energy density.

[0147] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A battery comprising a positive electrode, a negative electrode, and a separator, characterized in that, The positive electrode sheet includes a positive current collector and a positive electrode coating disposed on at least one side of the surface of the positive current collector. The positive electrode coating includes a positive electrode active material and a solid electrolyte. The positive electrode active material includes manganese and is selected from at least one of nickel-cobalt-manganese ternary materials, lithium manganese oxide, nickel-cobalt-manganese-aluminum quaternary materials, lithium manganese iron phosphate, and lithium manganese phosphate. The solid electrolyte includes titanium and is selected from lithium titanium aluminum phosphate and / or lithium lanthanum titanate. Based on the mass of the positive electrode coating, the weight ratio of manganese to titanium is (5~150):

1. The negative electrode sheet includes a negative electrode current collector and a negative electrode coating disposed on at least one side of the surface of the negative electrode current collector. The negative electrode coating includes a negative electrode active material, which includes graphite. The average particle size of the graphite is f μm. The OI value of the negative electrode sheet is g, and f and g satisfy: 0.06≤f / g≤1.

5.

2. The battery according to claim 1, characterized in that, Based on the quality of the positive electrode coating, the content of manganese in the positive electrode active material is 20,000 ppm to 400,000 ppm; preferably 50,000 ppm to 300,000 ppm. And / or, based on the quality of the positive electrode coating, the content of titanium in the solid electrolyte is 2000ppm to 100000ppm, preferably 4000ppm to 80000ppm.

3. The battery according to claim 1 or 2, characterized in that, f and g satisfy: 0.1 ≤ f / g ≤ 0.9; Preferably, 0.8≤f≤8, 4≤g≤20; more preferably, 1.2≤f≤6, 6≤g≤15.

4. The battery according to any one of claims 1-3, characterized in that, The average particle size of the positive electrode active material is a μm, and the average particle size of the solid electrolyte is b μm, wherein a and b satisfy: 10≤a / b≤300; And / or, the specific surface area of ​​the positive electrode active material is c m² / g, and a and c satisfy: 0.05≤a / c≤8; Preferably, 0.8 ≤ a ≤ 30, 0.05 ≤ b ≤ 0.8; more preferably, 2 ≤ a ≤ 20, 0.1 ≤ b ≤ 0.5; Preferably, 2.8 ≤ c ≤ 38, more preferably, 3.5 ≤ c ≤ 30.

5. The battery according to any one of claims 1-4, characterized in that, The surface of the positive electrode active material has a coating layer containing zirconium.

6. The battery according to any one of claims 1-5, characterized in that, The elongation of the positive electrode current collector is d%, and the thickness of the positive electrode current collector is e μm, where d and e satisfy: 1.5 ≤ e / d ≤ 6; preferably: 1.8 ≤ e / d ≤ 3.6; And / or, 15≤e / b≤180; preferably: 25≤e / b≤120.

7. The battery according to claim 6, characterized in that, The tensile strength of the positive current collector is x MPa, where x and e satisfy: 8≤x / e≤35.

8. The battery according to claim 7, characterized in that, The d satisfies: 3≤d≤7, preferably: 4≤d≤6.5; And / or, the e satisfies: 8≤e≤20, preferably: 10≤e≤15; And / or, the x satisfies: 150≤x≤300.

9. The battery according to any one of claims 1-8, characterized in that, The battery further includes a separator, the separator comprising a base film and a coating disposed on at least one side surface of the base film, the coating being disposed on the side of the base film facing the positive electrode, the coating comprising organic particles, the organic particles comprising at least one of 1,3,5-triazine-2,4,6-triamine, melamine cyanurate, melamine thiocyanate, 2,3-dicyanopyrazine, and symmetrical triaminotriazine; Preferably, the organic particles in the coating have a mass content of 50 wt% to 95 wt%.

10. The battery according to claim 9, characterized in that, The porosity of the diaphragm is h%, and the porosity of the positive electrode is i%. h and i satisfy: 0.5≤h / i≤3, preferably 0.9≤h / i≤2.1; Preferably, 30≤h≤80, 25≤i≤60; more preferably, 35≤h≤65, 30≤i≤50.

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