A battery

Abstract

This invention relates to the field of battery technology, specifically to a battery. The battery includes a positive electrode and an electrolyte. The positive electrode includes a positive current collector and a positive active layer. The positive active layer includes a ternary material, which comprises secondary particles interwoven from primary particles. The aspect ratio of the primary particles is 1.5-20. The ternary material has a hollow structure with internal cavities, and the area of ​​the cavities accounts for 5%-40% of the cross-section of the ternary material. The weight ratio of linear solvent to cyclic solvent in the electrolyte is 3-15. The cyclic solvent includes at least one of ethylene carbonate and propylene carbonate, and the weight percentage of the cyclic carbonate in the electrolyte is 8%-20%. The weight percentage of ethylene carbonate in the electrolyte is 0 < S1 ≤ 10%. The battery of this invention, through the synergistic effect of a specific ternary material structure and a specific electrolyte, enables the battery to possess both high low-temperature power performance and high cycle performance.

Description

Technical Field

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

[0002] As the global automotive industry accelerates its transformation towards electrification and intelligentization, the new energy vehicle market continues to expand, placing increasingly higher demands on vehicle energy systems. Against this backdrop, the automatic start-stop system, as a key energy-saving technology, has become a standard feature in modern vehicles. This system effectively reduces inefficient fuel consumption by 8% to 15% in urban driving conditions by automatically shutting off the engine when the vehicle is briefly stopped. However, this system places extremely stringent requirements on the battery: the battery must provide an instantaneous starting current of up to 300A within 0.5 seconds and withstand dozens of cycles per day. Traditional lead-acid batteries, due to their short cycle life, rapid degradation under high current discharge, weak low-temperature starting capability, and heavy weight, are no longer adequate for this role. In contrast, lithium-ion batteries, with their overwhelming advantages such as high energy density, ultra-long cycle life (up to 10 times that of lead-acid batteries), excellent power characteristics, and lightweight design (reducing weight by more than 50%), are becoming the inevitable choice for upgrading start-stop system batteries, driving the industry's progress towards "lead-free vehicles." However, lithium-ion batteries cannot simultaneously achieve both low-temperature starting performance and cycle performance. Summary of the Invention

[0003] Research has revealed that in lithium-ion battery technology, the cathode material is the key factor determining the performance boundary of the battery. While lithium iron phosphate (LFP) batteries hold a significant market share due to their high safety and low cost, their performance limitations at low temperatures restrict their application in harsh climates. Furthermore, at -20°C, the discharge capacity of LFP batteries can drop below 50%, while ternary lithium batteries (NCM / NCA) can still maintain over 70% of their performance. This is due to the superior ion diffusion kinetics of ternary materials, especially polycrystalline ternary materials composed of nano-primary particles. The abundant grain boundaries within the polycrystalline structure provide shorter diffusion paths and more transport channels for lithium ions, enabling them to maintain higher discharge voltage and capacity retention even at low temperatures.

[0004] However, conventional polycrystalline ternary cathode materials still face severe performance challenges when subjected to extreme low-temperature environments such as -30°C, making it difficult to meet the requirements of high-reliability applications. This is mainly due to their inherent microstructural defects. On the one hand, larger secondary particles (typically 10-20 micrometers) exhibit severe kinetic limitations at extremely low temperatures. Specifically, low temperatures significantly slow down the diffusion rate of lithium ions in solid materials. The long ion diffusion paths and complex grain boundary networks within large particles further restrict rapid ion transport, causing a sharp drop in the battery's effective discharge capacity, voltage plateau, and usable capacity at low temperatures, making it unable to provide the instantaneous high power required for vehicle cold starts. On the other hand, the polycrystalline structure of polycrystalline ternary cathode materials is composed of agglomerations of many nano-sized primary particles. During long-term charge-discharge cycles, significant grain boundary stress is generated due to anisotropic volume changes within the particles. This grain boundary stress easily leads to the internal rupture and pulverization of secondary particles, continuously exposing fresh, highly active interfaces. These highly active new interfaces not only accelerate the structural degradation of the material itself but also strongly catalyze the continuous oxidative decomposition reaction of the electrolyte solvent (especially ethylene carbonate EC) on the cathode surface, generating a large amount of gas, causing battery swelling, increased internal pressure, and a rapid acceleration of capacity decay and end of life. Moreover, although the single-crystal ternary cathode material has a stable structure, the diffusion kinetics of lithium ions in the single-crystal structure is poor, which limits the low-temperature power output of the single-crystal ternary cathode material.

[0005] In view of this, in order to improve the problem that ternary material batteries cannot simultaneously achieve high low-temperature power performance and high cycle performance, the present invention provides a battery. The battery of the present invention, through the synergistic combination of a specific structure of ternary materials and a specific electrolyte, enables the battery to possess both high low-temperature power performance and high cycle performance.

[0006] To achieve the above objectives, the present invention provides a battery comprising a positive electrode and an electrolyte. The positive electrode comprises a positive current collector and a positive active layer located on at least one side surface of the positive current collector. The positive active layer comprises a positive active material, which comprises a ternary material. The ternary material comprises secondary particles formed by interlacing primary particles. The aspect ratio of the primary particles is 1.5-20. The ternary material has a hollow structure with internal cavities, and the area of ​​the cavities in the cross-section of the ternary material accounts for 5%-40%. The electrolyte comprises a cyclic solvent and a linear solvent, wherein the weight ratio c of the linear solvent to the cyclic solvent is 3-15, the cyclic solvent comprises a cyclic carbonate, and the cyclic carbonate comprises at least one of ethylene carbonate and propylene carbonate, wherein the weight percentage of the cyclic carbonate in the electrolyte is 8%-20%, and the weight percentage S1 of the ethylene carbonate in the electrolyte is 0 < S1 ≤ 10%.

[0007] By employing the above technical solution, the present invention has at least the following advantages compared with the prior art: In the battery of this invention, the ternary material with a specific structure can improve the low-temperature power performance and cycle performance of the battery. Firstly, the abundant grain boundaries of the secondary particles formed by the interweaving of primary particles provide shorter diffusion paths and more transport channels for lithium ions, thereby improving the low-temperature power performance of the battery. Secondly, the secondary particles of the ternary material have an interwoven structure formed by the interweaving of primary particles. This interwoven structure, through the interlocking between particles, disperses external pressure and can reduce or even prevent the risk of overall breakage of the ternary material. Simultaneously, to form a tighter interwoven structure, the battery of this invention also controls the aspect ratio of the primary particles, thereby further improving the structural stability of the ternary material, reducing the risk of breakage, and also enhancing the conductivity of the ternary material. This improves the overall structural stability and low-temperature power performance of ternary materials, enabling the battery to have both high low-temperature power performance and cycle performance. Thirdly, the hollow structure of ternary materials can expand the contact interface between the ternary materials and the electrolyte, promote ion exchange, further improve the low-temperature power performance of the battery, and also provide a buffer space for the volume change of ternary materials during charging and discharging, reduce internal stress, and reduce or even prevent the structural failure of ternary materials. Furthermore, by controlling the area ratio of the cavity in the cross-section of the ternary materials, the proportion of hollow parts and solid materials in the ternary material structure can be balanced, ensuring that the structure of the ternary materials has sufficient mechanical strength to resist cyclic stress, reducing or even avoiding the risk of ternary material breakage, and further improving the cycle performance of the battery.

[0008] Simultaneously, by controlling the weight ratio of the linear solvent to the cyclic solvent in the electrolyte, the lithium-ion transport rate in the electrolyte can be improved. By controlling the weight ratio of ethylene carbonate in the electrolyte, the risk of side reactions of ethylene carbonate on the surface of ternary materials can be reduced while ensuring battery cycle performance, thereby reducing the battery thickness expansion rate and improving battery cycle performance. Therefore, the electrolyte of the battery of the present invention can match the requirements of ternary materials for rapid lithium-ion transport, further improving the low-temperature power performance and cycle performance of the battery.

[0009] Other features and advantages of the present invention will be described in detail in the following detailed description section.

[0010] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein. Attached Figure Description

[0011] Figure 1 The image shown is a SEM image of the ternary material of the present invention.

[0012] Figure 2 The image shown is a cross-sectional SEM image of the positive electrode active layer in a battery according to an embodiment of the present invention. Detailed Implementation

[0013] The following provides a detailed description of specific embodiments of the present invention. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the invention. Unless otherwise specified herein, data ranges include endpoints.

[0014] It should be noted that the numerical designations such as "first" and "second" in this invention are only used to distinguish different substances or methods of use, and do not represent a difference in order.

[0015] This invention provides a battery comprising a positive electrode and an electrolyte. The positive electrode comprises a positive current collector and a positive active layer located on at least one side surface of the positive current collector. The positive active layer comprises a positive active material, which comprises a ternary material. The ternary material comprises secondary particles formed by interlacing primary particles. The aspect ratio of the primary particles is 1.5-20 (e.g., 1.5, 3, 5, 8, 10, 13, 15, 18, or 20). The ternary material has a hollow structure with internal cavities. In the cross-section of the ternary material, the area ratio of the cavities is 5%-40% (e.g., 5%, 8%, 10%, 13%, 15%, 18%, 20%, 23%, 25%, 28%, 30%, 33%, 35%, 38%, 40%). The electrolyte comprises a cyclic solvent and a linear solvent, wherein the weight ratio c of the linear solvent to the cyclic solvent is 3-15 (3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14 or 15), the cyclic solvent comprises a cyclic carbonate, and the cyclic carbonate comprises at least one of ethylene carbonate and propylene carbonate, wherein the weight percentage of the cyclic carbonate in the electrolyte is 8%-20% (e.g., 8%, 10%, 13%, 15%, 18% or 20%), and the weight percentage S1 of the ethylene carbonate in the electrolyte is 0 < S1 ≤ 10% (e.g., 0, 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9% or 10%).

[0016] like Figure 1 As shown, the ternary material (marked by red solid circles) comprises secondary particles interwoven from primary particles, where the red circles represent secondary particles and the green solid squares represent primary particles. Figure 2 As shown, the ternary material has a hollow structure with internal cavities. The cross-section of the ternary material may include one cavity or multiple cavities (e.g., more than two). It is understood that the area ratio of the cavities in the cross-section of the ternary material refers to the ratio of the sum of the areas of all cavities in the cross-section to the area of ​​the cross-section itself.

[0017] In this invention, the area ratio of the cavity in the cross-section of the ternary material can be obtained by testing using the following method: a cross-sectional SEM image of the positive electrode active layer (e.g., ...). Figure 2In this method, arbitrarily select 50 cross-sections of ternary materials, and measure the area ratio of cavities in each of the 50 cross-sections. Take the average value as the area ratio of cavities in the cross-section of the ternary material. It is understood that when there are fewer than 50 ternary materials in the cross-sectional SEM image of the positive electrode active layer, multiple SEM images can be taken, and the average value of the total 50 cavity area ratios can be taken as the area ratio of cavities in the cross-section of the ternary material. Repeat the above operation three times, and take the average value as the final test result. The cross-sectional SEM image of the positive electrode active layer can be obtained by the following method: a small piece of positive electrode sheet is cut as a sample, cleaned with dimethyl carbonate to remove residual electrolyte and vacuum dried, the sample is vertically fixed in a special fixture, injected with epoxy resin to completely cover and cure, in order to support the fragile porous structure and prevent edge collapse, and then the embedded sample is placed in an argon ion polisher (CP), with an appropriate acceleration voltage and swing angle set, and the cross-section of the positive electrode sheet sample is finely ground with an argon ion beam to remove the mechanical damage layer and obtain an atomically flat surface. Finally, it is quickly transferred to SEM and observed at a low acceleration voltage, which can clearly show the details of internal cracks, grain boundaries and electrode interfaces of the particles, avoiding the morphological distortion caused by traditional cutting.

[0018] In this invention, the aspect ratio of the primary particle refers to the ratio of the length of the major axis to the length of the minor axis of the primary particle. The aspect ratio of the primary particle can be obtained by the following method: discharging the battery to 0% SOC (e.g., discharging the battery to 3V), disassembling and removing the positive electrode sheet, soaking it in dimethyl carbonate (DMC) solvent for 12 hours, then rinsing it with DMC solvent to remove the lithium salt adhering to the positive electrode sheet, calcining the positive electrode sheet in air at 450°C for 2-4 hours, scraping the ternary material off the positive electrode sheet with a ceramic knife, and observing the ternary material peeled off the positive electrode sheet using a scanning electron microscope to obtain a SEM image of the ternary material. The SEM image of the ternary material is depicted... The aspect ratio of a primary particle is defined as the smallest possible square or rectangle enclosing its edges. The length of one side of the square or rectangle is the major axis of the particle, and the length of the short side is the minor axis. The ratio of the major axis to the minor axis is the aspect ratio of the primary particle. Alternatively, 100 primary particles can be randomly selected, and their aspect ratios measured. The average aspect ratio is taken as the measured aspect ratio of the primary particle. The aspect ratio of the 100 primary particles can be obtained by taking multiple SEM images. Furthermore, SEM images of the ternary material can be obtained by observing the ternary material using an electron scanning microscope before it is fabricated into a cathode sheet.

[0019] The ternary material of this invention comprises secondary particles formed by the interweaving of primary particles. The secondary particles, formed by the interweaving of primary particles, have abundant grain boundaries, providing shorter diffusion paths and more transport channels for lithium ions, thereby improving the low-temperature power performance of the battery. Furthermore, the secondary particles possess an interwoven structure formed by the interweaving of primary particles (e.g., ...). Figure 1 As shown in the diagram, this interwoven structure, through the interlocking of particles, disperses external pressure, reducing or even preventing the risk of overall breakage of the ternary material. Simultaneously, to form a tighter interwoven structure, the battery of this invention also controls the aspect ratio of the primary particles, thereby further improving the structural stability of the ternary material, reducing the risk of breakage, and enhancing its conductivity. This improves the overall structural stability and low-temperature power performance of the ternary material, enabling the battery to possess both high low-temperature power performance and cycle performance. When the aspect ratio of the primary particles is less than 1.5, the resulting interwoven structure has poor stability and low mechanical strength, making it prone to breakage under stress, which is detrimental to improving the battery's low-temperature power performance. When the aspect ratio of the primary particles is greater than 20, the process of preparing secondary particles from primary particles becomes more difficult and difficult to implement.

[0020] Furthermore, the ternary material of this invention has a hollow structure with internal cavities. This hollow structure can expand the contact interface between the ternary material and the electrolyte, promote ion exchange, and further improve the low-temperature power performance of the battery. Simultaneously, it can provide buffer space for volume changes during charge and discharge, reducing internal stress and lowering or even preventing structural breakage failure. Furthermore, by controlling the area ratio of the cavity in the cross-section of the ternary material to be 5%-40%, the proportion of hollow parts and solid materials in the ternary material structure can be balanced, ensuring that the ternary material structure has sufficient mechanical strength to resist cyclic stress, reducing or even avoiding the risk of ternary material breakage, and further improving the cycle performance of the battery. When the area ratio of the cavity in the cross-section of the ternary material is less than 5%, the area ratio of solid material in the ternary material is large, and the area ratio of the internal cavity is small, which will lead to a decrease in the low-temperature power performance of the battery. When the area ratio of the cavity in the cross-section of the ternary material is higher than 40%, that is, the area ratio of the cavity is large, the outer wall of the ternary material particles will be thin, resulting in a loss of the compaction density of the ternary material. Moreover, during battery cycling, the thin outer wall is prone to breakage, causing the ternary material to break. When the ternary material breaks, more new interfaces will be exposed. These new interfaces do not have enough additives to form a film, and the oxygen on the surface will come into direct contact with the solvent in the electrolyte, oxidizing the solvent and decomposing it to produce gas (for example, oxygen free radicals on the surface will take away hydrogen from the surface of ethylene carbonate, causing ethylene carbonate to form an unstable structure, which will eventually decompose and produce gas under the catalysis of the ternary material). With the breakage of the ternary material particles, the electrolyte oxidizes and produces gas, accompanied by the loss of active lithium, causing the battery capacity to decay rapidly.

[0021] The linear solvent in the electrolyte has a lower viscosity, which effectively reduces the overall viscosity of the electrolyte and improves the migration rate of lithium ions. Especially at low temperatures, linear solvents have lower melting points and viscosities, resulting in less resistance to lithium ion transport within the electrolyte bulk. Furthermore, linear solvents have lower desolvation energy compared to cyclic solvents, thus exhibiting lower polarization at low temperatures, which matches the requirements of ternary materials for rapid lithium ion transport. Cyclic solvents, on the other hand, provide higher dielectric constants and stability. To further improve the low-temperature power performance of the battery and enable the electrolyte to be compatible with ternary materials, the weight ratio c of the linear solvent to the cyclic solvent in the battery control electrolyte of this invention is 3-15.

[0022] Under high pressure, the active oxygen species abundant on the surface of the ternary material can easily catalyze the oxidation and decomposition of ethylene carbonate in the electrolyte, thereby producing gas. However, ethylene carbonate can form a film on the negative electrode, reducing battery capacity decay and improving battery cycle performance. Therefore, in order to improve the problem of gas production caused by oxidation of the electrolyte on the surface of the ternary material, the battery of the present invention controls the weight ratio of ethylene carbonate in the electrolyte, thereby ensuring battery cycle performance while reducing the risk of side reactions of ethylene carbonate on the surface of the ternary material, reducing battery thickness expansion rate and improving battery cycle performance.

[0023] In this invention, by controlling the structure of the ternary material and the weight ratio of linear to cyclic solvents in the electrolyte, as well as the weight percentage of ethylene carbonate in the electrolyte, a battery exhibiting both high low-temperature power performance and high cycle performance can be achieved compared to existing technologies. To further improve the performance, one or more of the technical features can be further optimized.

[0024] In some instances, the major axis of the primary particles has a size of 0.5 μm to 3 μm (e.g., 0.5 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm).

[0025] In some instances, the minor axis of the primary particle has a size of 0.05 μm to 0.5 μm (e.g., 0.05 μm, 0.1 μm, 0.15 μm, 0.2 μm, 0.25 μm, 0.3 μm, 0.35 μm, 0.4 μm, 0.45 μm, or 0.5 μm).

[0026] According to some specific embodiments, the major axis of the primary particles is 0.5μm-3μm, the minor axis is 0.05μm-0.5μm, and the aspect ratio is 1.5-20. The ternary material of this invention includes secondary particles formed by interwoven primary particles, i.e., the secondary particles are formed by interwoven primary particles. Controlling the major and minor axis dimensions of the primary particles to meet the above-mentioned ranges facilitates the formation of an interwoven structure, while simultaneously improving the mechanical meshing and contact points between the primary particles in the interwoven structure. This allows for the alleviation of charge-discharge stress, reducing or even preventing particle breakage of the ternary material, while providing a rich conductive network for electrons and ions, thereby enhancing the structural stability and electrochemical kinetic performance of the cathode, and further improving the low-temperature power performance and cycle performance of the battery.

[0027] In some instances, the primary particles have a rod-like morphology.

[0028] In some instances, the ternary material comprises materials with the chemical formula LiNi. x Co y Mnz M 1-x-y-z The substance of O2 is 0.3≤x≤0.8 (e.g., 0.3, 0.4, 0.5, 0.6, 0.7 or 0.8), 0.05≤y≤0.3 (e.g., 0.05, 0.1, 0.15, 0.2, 0.25 or 0.3), 0.1≤z≤0.4 (e.g., 0.1, 0.15, 0.2, 0.25, 0.3, 0.35 or 0.4), and M includes at least one of Al, Zr, B, Mg, B, Y, Sr, W, Ti and Nb.

[0029] In some instances, 0.5 ≤ x ≤ 0.6.

[0030] In some instances, the average particle size of the ternary material is 2μm-8μm (e.g., 2μm, 3μm, 4μm, 5μm, 6μm, 7μm, 8μm). In a ternary material system, ternary materials with an average particle size within the above range are considered to have smaller particle sizes. Controlling the average particle size of the ternary material to meet the above range can further improve the lithium-ion transport rate within the ternary material, thereby further improving the instantaneous charge-discharge performance of the battery at low temperatures.

[0031] In some instances, the average particle size of the ternary material is 3 μm-5 μm.

[0032] In this invention, the particle size of the ternary material can be obtained by the following method: On a scanned image, draw the smallest square or rectangle that completely surrounds one ternary material, i.e., draw a square or rectangle whose edge connects to all four sides of the square or rectangle. The length of one side of the square or the length of the long side of the rectangle is the particle size of the ternary material. In the SEM image of the positive electrode active layer cross-section, arbitrarily select an area of ​​100μm × 100μm, and average the particle sizes of any 50 ternary materials to obtain the average particle size. Repeat the above operation 5 times, and take the average value as the average particle size of the ternary material. It should be noted that if 50 ternary materials can be observed in the captured image, the average particle size of any 50 ternary materials in that image is taken as the average particle size of the ternary material. If no 50 ternary materials are observed in the image, take multiple images, and average the total number of particle sizes of 50 ternary materials to obtain the average particle size. The scanned images can be obtained by observing the cross-section of the positive electrode active layer using a scanning electron microscope.

[0033] In some instances, the sphericity of the ternary material is 0.8-1 (e.g., 0.8, 0.83, 0.85, 0.88, 0.9, 0.93, 0.95, 0.98, or 1). Cross-sectional particle images of the positive electrode active layer are captured using a scanning electron microscope (SEM). Within an arbitrarily selected 100μm × 100μm area in the image, ternary material particles are identified using image analysis software (e.g., ImageJ, NanoMeasurer, Matlab, etc.). The radius r1 of the equivalent circle representing the projected perimeter of a single ternary material particle and the radius r2 of the equivalent circle representing the projected area of ​​the particle are calculated. The sphericity of a single ternary material particle is calculated as r2 / r1. The sphericity of 100 ternary material particles is averaged. This process is repeated 5 times, and the average value is the final test result.

[0034] Controlling the sphericity of the ternary material within the aforementioned range ensures that the ternary material particles have a regular morphology, thereby ensuring that the stress on the ternary material is relatively uniform during charging and discharging, thus reducing the risk of ternary material breakage and further improving the structural stability of the ternary material. At the same time, it is also conducive to achieving close packing of ternary material particles in the positive electrode active layer, increasing the compaction density of the positive electrode active layer, further improving the uniformity of the positive electrode sheet and the lithium ion transport efficiency, and further improving the low-temperature power performance of the battery.

[0035] In some instances, the ternary material has a polycrystalline structure.

[0036] Studies have shown that lithium ions experience less resistance when shuttling between lithium titanium aluminum phosphate and lithium aluminum titanium silicon phosphate. In particular, lithium ions can be directly transported between lithium titanium aluminum phosphate and ternary materials, and the transport of lithium ions from lithium titanium aluminum phosphate to ternary materials does not require a desolvation process.

[0037] In some examples, the surface of the ternary material includes a coating layer comprising at least one of lithium aluminum titanium phosphate (LATP) and lithium aluminum titanium silicon phosphate (LATSP). The LATP and LTSP in the coating layer can improve the lithium-ion transport rate within the ternary material. Furthermore, LATP can reduce lithium-ion interfacial transport from the electrolyte to the ternary material, improving the battery's instantaneous charge-discharge performance at low temperatures and its low-temperature power performance. The coating layer also creates a stable interface with high ion conductivity between the ternary material and the electrolyte, reducing side reactions and gas generation while simultaneously enhancing ion transport and further improving the battery's cycle performance.

[0038] In some examples, the cavity of the ternary material includes at least one of lithium aluminum titanium phosphate and lithium aluminum titanium silicon phosphate. The lithium aluminum titanium phosphate and lithium aluminum titanium silicon phosphate in the cavity of the ternary material can improve the lithium-ion transport rate within the ternary material, further enhancing the low-temperature power performance of the battery.

[0039] In some examples, the inner surface of the cavity of the ternary material includes at least one of lithium aluminum titanium phosphate and lithium aluminum titanium silicon phosphate. The lithium aluminum titanium phosphate and lithium aluminum titanium silicon phosphate on the inner surface of the cavity of the ternary material can improve the transport rate of lithium ions in the ternary material, further enhancing the low-temperature power performance of the battery.

[0040] In some instances, the ternary material includes elements Al and Ti. It is understood that the Al and Ti elements in the ternary material can be derived from at least one of lithium aluminum titanium phosphate or lithium aluminum titanium silicon phosphate.

[0041] In some examples, the weight percentage of element Al in the positive electrode active layer is 0.1%-3% (e.g., 0.1%, 0.5%, 1%, 1.5%, 2%, 2.5%, or 3%), and the weight percentage of element Ti is 0.1%-3% (e.g., 0.1%, 0.5%, 1%, 1.5%, 2%, 2.5%, or 3%). Controlling the weight percentages of element Al and element Ti in the positive electrode active layer to satisfy the above relationship can further improve the lithium-ion transport rate in the ternary material and further enhance the low-temperature power performance of the battery.

[0042] In this invention, the weight percentages of Al and Ti in the positive electrode active layer can be obtained by the following method: Taking the "weight percentage of Al in the positive electrode active layer" as an example, the battery is discharged to 0% SOC (e.g., discharged to 3V). The battery is disassembled in a glove box, the positive electrode sheet is removed, cleaned with dimethyl carbonate to remove the electrolyte, and dried. The ternary material particles are scraped off the positive electrode active layer with a ceramic knife or grinding tool. An appropriate amount of sample is weighed and placed in a digestion vessel. A mixture of hydrochloric acid and nitric acid or aqua regia is added for microwave high-temperature sealed digestion. If necessary, a small amount of hydrofluoric acid is added to aid dissolution until the solution is clear and transparent. After cooling, the solution is transferred to a volumetric flask and diluted to volume with dilute nitric acid. The solution is then shaken well. Inductively coupled plasma optical emission spectrometry (ICP-OES) or mass spectrometry (ICP-MS) is used to select the characteristic spectral line of Al (e.g., 396.152 nm), and quantitative analysis is performed using the standard curve method. A blank experiment is also performed to correct for background interference to ensure data accuracy.

[0043] In some instances, the ternary material includes element Si. Element Si can originate from at least one of the following: LATSP in the ternary material's coating layer, LATSP in the ternary material's cavity, or LATSP on the inner surface of the ternary material's cavity. HF generated from the side reaction of lithium hexafluorophosphate in the electrolyte easily etches the surface of the ternary material, leading to gas production. Adding element Si to the ternary material can absorb the HF generated from the side reaction of lithium hexafluorophosphate, thereby improving the gas production problem.

[0044] In some instances, the weight percentage of element Si in the positive electrode active layer is 0.1%-3% (e.g., 0.1%, 0.5%, 1%, 1.5%, 2%, 2.5%, or 3%). In this invention, the method for testing the weight percentage of element Si in the positive electrode active layer can refer to the method for testing the weight percentage of element Al in the same positive electrode active layer. The characteristic spectral line of Si can be 251.611 nm.

[0045] In some instances, the ternary material accounts for 90%-95% of the weight of the positive electrode active layer.

[0046] In some instances, the positive electrode active layer comprises a positive electrode conductive agent, which includes a spherical conductive agent.

[0047] In some examples, the average particle size of the spherical conductive agent is 50nm-200nm (e.g., 50nm, 80nm, 100nm, 130nm, 150nm, 180nm, or 200nm). The nanoscale spherical conductive agent can uniformly fill the spaces between the particles of the ternary material, forming numerous point-to-point conductive pathways. This reduces the contact resistance and bulk resistance of the positive electrode, ensuring rapid electron collection and transport during charging. In synergy with the hollow structure of the ternary material, it further optimizes the ion transport path, increases the ion transport rate, further reduces the overall impedance of the battery, and further improves the low-temperature power performance of the battery.

[0048] In this invention, in the SEM image of the positive electrode active layer cross-section, an arbitrary 10μm × 10μm area is selected. Using image analysis software (e.g., ImageJ, NanoMeasurer, Matlab, etc.), the particle size of 100 randomly selected spherical conductive agents is measured. The average particle size of these 100 spherical conductive agents is then taken as the average particle size of the spherical conductive agents. It is understood that if no 100 spherical conductive agents are observed in the image, multiple images are taken, and the average of the total particle sizes of the 100 spherical conductive agents is taken as the average particle size of the spherical conductive agents.

[0049] In some instances, the sphericity of the spherical conductive agent is 0.9-1 (e.g., 0.9, 0.93, 0.95, 0.97, 1). A cross-sectional image of the positive electrode active layer particles is captured using a scanning electron microscope (SEM). Within an arbitrarily selected 10μm × 10μm area in the image, using image analysis software (e.g., ImageJ, NanoMeasurer, Matlab, etc.), the particles of the spherical conductive agent are identified. The radius r1 of the equivalent circle representing the projected circumference of a single spherical conductive agent particle and the radius r2 of the equivalent circle representing the projected area of ​​the spherical conductive agent particle are calculated. The sphericity of a single spherical conductive agent particle is calculated as r2 / r1. The sphericity of 100 spherical conductive agent particles is averaged. This process is repeated 5 times, and the average value is the final test result.

[0050] In some instances, the spherical conductive agent includes carbon black.

[0051] In some instances, the positive electrode conductive agent in the positive electrode active layer accounts for 2%-8% by weight (e.g., 2%, 3%, 4%, 5%, 6%, 7%, 8%).

[0052] According to some specific embodiments, the average particle size of the spherical conductive agent is 50nm-200nm, and the weight percentage of the positive electrode conductive agent in the positive electrode active layer is 2%-8%. This enables the construction of a highly efficient three-dimensional electronic conductive network in the positive electrode active layer, further improving the battery's transmission rate, low-temperature power performance, and rate performance.

[0053] In some instances, the positive electrode active layer further includes a positive electrode binder, which includes at least one of polyvinylidene fluoride, a copolymer of polyvinylidene fluoride and hexafluoropropylene, a styrene-acrylate copolymer, a styrene-butadiene copolymer, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate, sodium carboxymethyl cellulose, polyvinyl acetate, polyvinylpyrrolidone, polyvinyl ether, polymethyl methacrylate, polytetrafluoroethylene, or polyhexafluoropropylene.

[0054] In some instances, the positive electrode binder accounts for 1%-5% by weight in the positive electrode active layer (e.g., 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%).

[0055] In some instances, the areal density of the positive electrode sheet on one side is 5 mg / cm³. 2 -10mg / cm 2 (For example, 5 mg / cm) 2 5.5 mg / cm 2 6mg / cm 2 6.5 mg / cm2 7mg / cm 2 7.5 mg / cm 2 8mg / cm 2 8.5 mg / cm 2 9mg / cm 2 9.5 mg / cm 2 Or 10mg / cm 2 ).

[0056] In some instances, the compaction density of the positive electrode is 2 g / cm³. 3 -4g / cm 3 (For example, 2g / cm) 3 2.3g / cm 3 2.5g / cm 3 2.8g / cm 3 3g / cm 3 3.3g / cm 3 3.5g / cm 3 3.8g / cm 3 or 4g / cm 3 ); In some instances, the thickness of the positive current collector is 4 μm-15 μm (e.g., 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm or 15 μm).

[0057] In some instances, the positive current collector comprises aluminum foil.

[0058] In some specific embodiments, the areal density of the positive electrode sheet on one side is 5 mg / cm³. 2 -10mg / cm 2 The compaction density of the positive electrode sheet is 2 g / cm³. 3 -4g / cm 3 By controlling the areal density and compaction density of the positive electrode sheet to meet the aforementioned ranges, it is possible to ensure that the positive electrode active layer has a suitable porosity structure, thereby reducing the transport resistance and path tortuosity of lithium ions within the positive electrode sheet. This improves the electrolyte wetting performance and ion transport kinetics of the positive electrode sheet, further enhancing the low-temperature rate performance of the battery. Simultaneously, using a 10μm-15μm thin aluminum foil as the current collector provides an excellent high-conductivity substrate while ensuring high battery energy density, thus ensuring efficient electron collection and extraction. Furthermore, in synergy with ternary materials with specific structures, spherical conductive agents, and the electrolyte system, it further reduces the total impedance of the battery, further improving the low-temperature power performance and enhancing the battery's high-rate discharge and fast-charging performance.

[0059] In some instances, the linear solvent includes one or more of propyl propionate (PP), ethyl propionate (EP), ethyl acetate (EA), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC).

[0060] In some instances, the electrolyte comprises a lithium salt, including lithium hexafluorophosphate and a first lithium salt, the first lithium salt including at least one of lithium bis(fluorosulfonyl)imide and lithium bis(trifluoromethanesulfonyl)imide. At high temperatures, PF... 6- It is easy to decompose and generate PF5 and F. - PF5 further catalyzes the ring-opening polymerization of EC in the electrolyte, which may generate CO2, etc. The anionic center of LiFSI (lithium bisfluorosulfonylimide) and LiTFSI (lithium bistrifluoromethylsulfonylimide) is a nitrogen (N) atom, with the structure (R-SO2-N-SO2-R')-, where R / R' is -F or -CF3. First, the N atom is sp3 hybridized, and its outer electron structure is stable. It does not have low-energy empty orbitals to accept nucleophilic attacks or undergo coordination expansion similar to P, so it does not have strong Lewis acidity. Second, the fluorine (F) atom in the molecule is not directly connected to the central N atom, but exists in the form of a high-bond-energy CF bond on the side chain of the sulfonyl group (-SO2F or -CF3). The bond energy of the CF bond is much higher than that of the PF bond, and it is more difficult to break thermodynamically. Therefore, it is precisely because LiFSI and LiTSFI have the above-mentioned unique structure that lithium ions can be easily dissociated and have higher conductivity.

[0061] In some instances, the lithium hexafluorophosphate in the electrolyte comprises 3%-8% by weight (e.g., 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5% or 8%).

[0062] In some instances, the first lithium salt accounts for 5%-10% by weight in the electrolyte (e.g., 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5% or 10%).

[0063] In some instances, the weight percentage of the first lithium salt in the electrolyte is greater than the weight percentage of lithium hexafluorophosphate in the electrolyte. Controlling the weight percentage of the first lithium salt in the electrolyte to be greater than the weight percentage of lithium hexafluorophosphate can improve the conductivity of the electrolyte while reducing side reactions of lithium hexafluorophosphate, thereby improving the high-temperature cycle performance of the battery.

[0064] According to some specific embodiments, the weight percentage of the first lithium salt in the electrolyte is greater than the weight percentage of the lithium hexafluorophosphate in the electrolyte. The weight percentage of the lithium hexafluorophosphate in the electrolyte is 3%-8%, and the weight percentage of the first lithium salt in the electrolyte is 5%-10%.

[0065] In some examples, the electrolyte includes sulfur-containing additives, such as one or more of 1,3-propanesulfonyl lactone, vinyl sulfate, ethylene sulfite, 1,2,5-oxodithionane-2,2,5,5-tetracyclooxyethylene, thiophene, propylene-1,3-sulfonyl lactone, and mannitol carbonate sulfate. Ternary materials have numerous active sites on their surface, making them prone to electrolyte oxidation and leading to battery gas production. To further improve the high-temperature cycle performance of the battery and mitigate the risk of gas production, sulfur-containing additives are added to the electrolyte. On the one hand, these sulfur-containing additives preferentially oxidize at high potentials compared to solvents such as ethylene carbonate (EC), forming a dense and ion-conducting solid passivation film (CEI) on the positive electrode surface, isolating the electrolyte from direct contact with the highly active ternary material. On the other hand, the decomposition products or specific functional groups (such as -SOx) of the sulfur-containing additives can directly interact with the active sites on the positive electrode surface that catalyze electrolyte oxidation (mainly transition metal ions Ni). 3+ / 4+ It forms a stable SOM structure by forming a strong chemical bond with unstable lattice oxygen, which "poisons" or even permanently passivates these catalytic centers at the molecular level. Through the synergistic effect of the above two aspects, the catalytic oxidation decomposition chain of solvents such as EC is fundamentally cut off, thereby significantly reducing gas generation and further improving the high-temperature cycle performance of the battery.

[0066] In some instances, the sulfur-containing additive in the electrolyte accounts for 0.1% to 5% by weight (e.g., 0.1%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5% or 5%).

[0067] In some instances, the weight ratio of ethylene carbonate to sulfur-containing additive in the electrolyte is 0-10 (e.g., 0, 0.1, 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10). Controlling the weight ratio of ethylene carbonate to sulfur-containing additive in the electrolyte within this range improves the compatibility between ethylene carbonate and sulfur-containing additive, effectively inhibits the oxidative decomposition of ethylene carbonate on the surface of the ternary material, and further enhances the high-temperature cycle performance of the battery.

[0068] In some instances, the electrolyte includes a first additive comprising elements P and F. Low levels of ethylene carbonate (EC) in the electrolyte limit its ability to form a film at the negative electrode, resulting in a poor-performing SEI film. Other solvents in the electrolyte, such as linear solvents, continuously decompose on the surface of the negative electrode, leading to the accumulation of decomposition products. Therefore, a first additive containing elements P and F is added to the electrolyte. This first additive preferentially undergoes reduction and decomposition near the lithium intercalation potential of the negative electrode, participating in the construction of the SEI film and forming a film rich in LiF, Li3P, and Li3PO4. x F y The inorganic and organic lithium salt composite SEI film has high chemical stability and high ionic conductivity. Moreover, its dense structure can block the continuous contact and reduction decomposition of linear solvent molecules in the electrolyte with the surface of the negative electrode active material, thereby inhibiting the consumption of other solvents such as linear solvents and the accumulation of decomposition products on the surface of the negative electrode, thus further improving the cycle performance of the battery.

[0069] In some instances, the first additive includes one or more of lithium difluorophosphate, lithium tetrafluorophosphate, lithium difluorodioxarate phosphate, and lithium tetrafluorooxarate phosphate.

[0070] In some instances, the first additive is present in the electrolyte at a weight percentage of 0.1%-5% (e.g., 0.1%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5% or 5%).

[0071] In some instances, the electrolyte includes lithium salts, organic solvents, and additives.

[0072] In some instances, the organic solvent includes linear solvents and cyclic solvents.

[0073] In some instances, the organic solvent in the electrolyte accounts for 80%-90% by weight (e.g., 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, or 90%).

[0074] In some instances, the additives include sulfur-containing additives and a first additive.

[0075] In some instances, the additive in the electrolyte is present in a weight percentage of 0.1%-8% (e.g., 0.1%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5% or 8%).

[0076] In some instances, the battery has a charging cutoff voltage greater than 4.2V (e.g., 4.25V, 4.3V, 4.4V, 4.5V).

[0077] In some instances, the battery is a lithium-ion rechargeable battery.

[0078] The present invention will be described in detail below through embodiments. The embodiments described herein are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0079] The following examples illustrate the battery of the present invention.

[0080] Example 1 (1) Positive electrode plate Ternary materials (LiNi) 0.6 CO 0.2 Mn 0.2 O2 powder, polyvinylidene fluoride, and carbon black (sphericity 0.95, average particle size 65nm) were added to a vacuum mixer in a mass ratio of 93%:2%:5%. N-methylpyrrolidone (NMP) was added, and the mixture was thoroughly mixed under vacuum until a uniform, free-flowing positive electrode slurry with a solid content of 55wt% was formed. The positive electrode slurry was then uniformly coated on both sides of a 12μm thick aluminum foil, with a single-sided surface density of 8mg / cm². 2 After drying, rolling, controlling the thickness of the active material on one side to be 30μm, slitting, and punching, the positive electrode sheet is obtained.

[0081] The primary particles in the ternary material have a major axis dimension of 1.1 μm, a minor axis dimension of 0.2 μm, an aspect ratio of 5.5, a cavity area ratio of 20.3% in the cross-section of the ternary material, a sphericity of 0.85, and an average particle size of 3.6 μm.

[0082] (2) Negative electrode plate Graphite, styrene-acrylic emulsion, sodium carboxymethyl cellulose, and acetylene black were added to a vacuum mixer in a mass ratio of 95.5:1.5:1:2. Deionized water was added, and the mixture was thoroughly mixed under vacuum to form a uniform, free-flowing negative electrode slurry with a solid content of 45 wt%. The negative electrode slurry was uniformly coated on both sides of a 6 μm thick carbon-coated copper foil, and after drying and rolling, a negative electrode sheet was obtained.

[0083] (3) Electrolyte Ingredients preparation: Lithium hexafluorophosphate (LiPF6) 5 parts by weight, lithium bis(fluorosulfonyl)imide (LiFSI) 10 parts by weight: Cyclic solvent: 10 parts by weight of ethylene carbonate (EC); Linear solvents: 36 parts by weight of dimethyl carbonate (DMC) and 36 parts by weight of ethyl methyl carbonate (EMC); Sulfur-containing additives: a total of 2 parts by weight, 1,3-propanesulfonyl lactone: mannitol carbonate sulfate: vinyl sulfate (weight ratio 1:3:1) First additive: 1 part by weight of lithium difluorophosphate.

[0084] In an argon glove box with a water content of <0.1ppm and an oxygen content of <0.1ppm, ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) were mixed. Fully dried lithium hexafluorophosphate (LiPF6) and lithium difluorosulfonyl imide (LiFSI) were added to the above solution, followed by the addition of 1,3-propane sulpholol, mannitol carbonate sulfate, ethylene sulfate, and lithium difluorophosphate. The mixture was stirred until homogeneous, and after passing the physical property test, the electrolyte was obtained.

[0085] (4) Lithium-ion batteries The positive electrode obtained in step (1), the negative electrode obtained in step (2), and the separator (PP) are wound together to obtain a bare cell. The two bare cells are welded to the tabs through connecting pieces and placed in the battery casing. The electrolyte prepared in step (3) is injected into the dried and qualified cell. After standing, aging, formation, secondary sealing, aging, sorting and other processes, the battery is obtained.

[0086] Example 2 group This set of examples illustrates the effects of changes in the structure of ternary materials.

[0087] This embodiment group is based on Embodiment 1, except that the structure of the ternary material is changed, as detailed in Table 1-1.

[0088] Table 1-1 Example 3 Group This set of examples illustrates the effects of changes in the sphericity of ternary materials.

[0089] Example 3a The same procedure was followed as in Example 1, except that the sphericity of the ternary material was 0.8.

[0090] Example 3b The same procedure was followed as in Example 1, except that the sphericity of the ternary material was 0.95.

[0091] Example 3c The same procedure was followed as in Example 1, except that the sphericity of the ternary material was 0.75.

[0092] Example 4 group This set of examples illustrates the effects of changing the aspect ratio of primary particles in ternary materials.

[0093] This embodiment group is based on Embodiment 1, except that the aspect ratio of the primary particles of the ternary material is changed, as detailed in Tables 1-2.

[0094] Table 1-2 Example 5 group This set of embodiments is used to illustrate the effect when the area ratio of the cavity in the cross-section of the ternary material changes.

[0095] Example 5a The same procedure was followed as in Example 1, except that the preparation process of the ternary material was adjusted so that the area of ​​the cavity in the cross-section of the ternary material accounted for 5.6%.

[0096] Example 5b The same procedure was followed as in Example 1, except that the preparation process of the ternary material was adjusted so that the area of ​​the cavity in the cross-section of the ternary material accounted for 38.7%.

[0097] Example 6 group This set of examples illustrates the effects of changes in the average particle size of ternary materials.

[0098] Example 6a The procedure was carried out in accordance with Example 1, except that the average particle size of the ternary material was 1.8 μm.

[0099] Example 6b The procedure was carried out in accordance with Example 1, except that the average particle size of the ternary material was 7.6 μm.

[0100] Example 6c The procedure was carried out in accordance with Example 1, except that the average particle size of the ternary material was 8.5 μm.

[0101] Example 7 group This set of examples illustrates the effects of changes in the average particle size of the spherical conductive agent in the positive electrode conductive agent and / or the weight ratio of the positive electrode conductive agent in the positive electrode active layer.

[0102] Example 7a The experiment was conducted in accordance with Example 1, except that the average particle size of the spherical conductive agent was 44 nm and the weight percentage of the positive electrode conductive agent in the positive electrode active layer was 8.5%.

[0103] Example 7b The experiment was conducted in accordance with Example 1, except that the average particle size of the spherical conductive agent was 105 nm and the weight percentage of the positive electrode conductive agent in the positive electrode active layer was 7.2%.

[0104] Example 7c The experiment was conducted in accordance with Example 1, except that the average particle size of the spherical conductive agent was 215 nm and the weight percentage of the positive electrode conductive agent in the positive electrode active layer was 1.7%.

[0105] Example 8 group This set of examples illustrates the effects of changes in the composition of the electrolyte.

[0106] This embodiment group is based on Embodiment 1, except that the composition of the electrolyte is changed, as detailed in Tables 1-4 and 1-5.

[0107] Table 1-4 Same as 1 indicates the same as the embodiment.

[0108] Table 1-5 Same as 1 indicates the same as the embodiment.

[0109] Comparative Example 1 The same procedure was followed as in Example 1, except that the preparation process of the ternary material was adjusted so that there were no cavities inside the ternary material.

[0110] Comparative Example 2 The same procedure was followed as in Example 1, except that the preparation process of the ternary material was adjusted so that the area of ​​the cavity in the cross-section of the ternary material accounted for 45%.

[0111] Comparative Example 3 The procedure was carried out in accordance with Example 1, except that the major axis of the primary particle was 0.5 μm, the minor axis of the primary particle was 0.4 μm, and the aspect ratio of the primary particle was 1.25.

[0112] Comparative Example 4 The experiment was carried out in accordance with Example 1, except that the major axis of the primary particle was 1.1 μm, the minor axis of the primary particle was 0.05 μm, and the aspect ratio of the primary particle was 22.

[0113] Comparative Examples 5-10 The procedure was carried out in accordance with Example 1, except that the composition of the electrolyte was changed, as detailed in Tables 1-6 and 1-7.

[0114] Table 1-6 Same as 1 indicates the same as the embodiment.

[0115] Table 1-7 Same as 1 indicates the same as the embodiment.

[0116] Test case The batteries prepared in the examples and comparative examples were subjected to the following tests.

[0117] (1) High-temperature cycling performance test High-temperature cycling performance test: At 45℃, the initial thickness h1 of the battery was recorded. The battery was charged to the upper limit voltage of 4.2V at 0.33C, and discharged to the lower limit voltage of 2.5V at 0.33C. This cycle was repeated twice, and the second discharge capacity was selected as the initial discharge capacity C0. The battery was then charged to 80% SOC×C0 using a 10C0 constant current and constant voltage 0.05C cutoff method, allowed to stand for 100 minutes, and then discharged to 30% SOC×C0 using a 10C0 method. After 5000 cycles, the battery was charged to the upper limit voltage of 4.2V at 0.33C, and discharged to the lower limit voltage of 2.5V at 0.33C. This cycle was repeated twice, and the second discharge capacity was selected as the discharge capacity C after 5000 cycles. (5000T) Measure the battery thickness h2 and calculate the discharge capacity retention rate = [C (5000T) / C0]×100%, Battery thickness change rate=[(h2 / h1 )-1]×100%.

[0118] (2) Low-temperature power performance test Under a temperature of (25±2)℃, the battery cell was discharged at a standard constant current of 1C to the discharge termination voltage (2.5V) and left to stand for 30 minutes; then charged at a standard constant current and constant voltage of 1C to the charging limit voltage (4.2V), with a cutoff current of 0.05C, and left to stand for 30 minutes; finally, it was discharged at a standard constant current to the discharge termination voltage, thus obtaining the actual cell capacity Q. 0 Let stand for 30 minutes; charge to 4.2V using a constant current and constant voltage (1C), cutoff current 0.05C, and use 1Q. 0 Discharge to 40% SOC; place the battery at -30℃ for 4 hours to maintain a constant power output of 26.4Q. 0 W, constant power discharge for 10s, sampling every 10ms, recording voltage and current, and recording the final voltage V after 10s of discharge.

[0119] The results are recorded in Table 2.

[0120] Table 2 As can be seen from Table 2, by comparing the comparative examples and the embodiments, the batteries prepared in the embodiments have improved low-temperature power, significantly improved high-temperature cycle capacity retention, and reduced high-temperature cycle thickness expansion rate. This indicates that by controlling the structure of the ternary material and controlling the weight ratio of linear solvent to cyclic solvent in the electrolyte and the weight proportion of ethylene carbonate in the electrolyte, the battery can have both high low-temperature power performance and high cycle performance.

[0121] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A battery, characterized in that, The battery includes a positive electrode sheet and an electrolyte. The positive electrode sheet includes a positive current collector and a positive active layer located on at least one side surface of the positive current collector. The positive active layer includes a positive active material, which is a ternary material. The ternary material includes secondary particles formed by interlacing primary particles. The aspect ratio of the primary particles is 1.5-20. The ternary material has a hollow structure with internal cavities. In the cross-section of the ternary material, the area of ​​the cavities accounts for 5%-40%. The electrolyte comprises a cyclic solvent and a linear solvent, wherein the weight ratio c of the linear solvent to the cyclic solvent is 3-15, the cyclic solvent comprises a cyclic carbonate, and the cyclic carbonate comprises at least one of ethylene carbonate and propylene carbonate, wherein the weight percentage of the cyclic carbonate in the electrolyte is 8%-20%, and the weight percentage S1 of the ethylene carbonate in the electrolyte is 0 < S1 ≤ 10%.

2. The battery according to claim 1, wherein, The ternary material comprises components with the chemical formula LiNi. x Co y Mn z M 1-x-y-z O2 is a substance with a molecular weight of 0.3 ≤ x ≤ 0.8, 0.05 ≤ y ≤ 0.3, and 0.1 ≤ z ≤ 0.

4. M includes at least one of Al, Zr, B, Mg, B, Y, Sr, W, Ti, and Nb. And / or, the sphericity of the ternary material is 0.8-1; And / or, the morphology of the primary particles is rod-shaped.

3. The battery according to claim 1, wherein, The average particle size of the ternary material is 2μm-8μm, preferably 3μm-5μm; And / or, the major axis dimension of the primary particle is 0.5μm-3μm; And / or, the minor axis size of the primary particle is 0.05μm-0.5μm.

4. The battery according to claim 1, wherein, The surface of the ternary material includes a coating layer, which includes at least one of lithium aluminum titanium phosphate and lithium aluminum titanium silicon phosphate. And / or, the cavity of the ternary material includes at least one of lithium aluminum titanium phosphate and lithium aluminum titanium silicon phosphate; And / or, the inner surface of the cavity of the ternary material includes at least one of lithium aluminum titanium phosphate and lithium aluminum titanium silicon phosphate.

5. The battery according to claim 1, wherein, The ternary material includes elements Al and Ti. Preferably, in the positive electrode active layer, the weight percentage of element Al is 0.1%-3% and the weight percentage of element Ti is 0.1%-3%. And / or, the ternary material includes element Si, and the weight percentage of element Si in the positive electrode active layer is 0.1%-3%.

6. The battery according to claim 1, wherein, The electrolyte includes a lithium salt, which includes lithium hexafluorophosphate and a first lithium salt, wherein the first lithium salt includes at least one of lithium bis(fluorosulfonyl)imide and lithium bis(trifluoromethanesulfonyl)imide. Preferably, the weight percentage of lithium hexafluorophosphate in the electrolyte is 3%-8%, and / or the weight percentage of the first lithium salt in the electrolyte is 5%-10%, and / or the weight percentage of the first lithium salt in the electrolyte is greater than the weight percentage of lithium hexafluorophosphate in the electrolyte.

7. The battery according to claim 1, wherein, The electrolyte includes sulfur-containing additives, which include one or more of 1,3-propane sulpholactone, vinyl sulfate, ethylene sulfite, 1,2,5-oxodithionane-2,2,5,5-tetracyclooxyethylene, thiophene, propenyl-1,3-sulfonyl lactone, and mannitol carbonate sulfate. Preferably, the sulfur-containing additive in the electrolyte accounts for 0.1%-5% by weight; Preferably, in the electrolyte, the weight ratio of the ethylene carbonate to the sulfur-containing additive is 0-10.

8. The battery according to claim 1, wherein, The electrolyte includes a first additive, which includes elements P and F. Preferably, the first additive includes one or more of lithium difluorophosphate, lithium tetrafluorophosphate, lithium difluorodioxarate phosphate, and lithium tetrafluorooxarate phosphate. Preferably, the weight percentage of the first additive in the electrolyte is 0.1%-5%.

9. The battery according to claim 1, wherein, The positive electrode active layer includes a positive electrode conductive agent, which includes a spherical conductive agent with an average particle size of 50nm-200nm. Preferably, the sphericity of the spherical conductive agent is 0.9-1; Preferably, the spherical conductive agent comprises carbon black; Preferably, the positive electrode conductive agent accounts for 2%-8% of the weight of the positive electrode active layer.

10. The battery according to claim 1, wherein, The areal density of the positive electrode sheet is 5 mg / cm³. 2 -10mg / cm 2 ; And / or, the compaction density of the positive electrode is 2 g / cm³. 3 -4g / cm 3 ; And / or, the thickness of the positive current collector is 4μm-15μm.

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