Battery

Abstract

The embodiment of the invention relates to the technical field of batteries, and provides a battery which comprises a positive plate, a negative plate and an electrolyte, and the electrolyte comprises propyl acetate and a compound as shown in a formula 1; the positive plate comprises a positive current collector and a positive active coating coated on at least one surface of the positive current collector, the positive active coating comprises a positive active material, and the positive active material comprises an Ni element; the mass percentage content a of the propyl acetate in the electrolyte, the mass percentage content b of the compound shown in the formula 1 in the electrolyte and the molar percentage content c of the Ni element in all transition metal elements in the positive electrode active material meet the condition that (a + b) / c is greater than or equal to 0.15 and less than or equal to 1. Through mutual cooperation and interaction of the three components, the temperature rise of the battery can be effectively reduced, and the safety of the battery is improved.

Description

Technical Field

[0001] This application relates to the technical field of batteries, and particularly to a battery. Background Art

[0002] With the continuous development of lithium-ion batteries in the new energy field, battery life has become a key factor restricting the development of new energy. Improving the energy density and fast charging ability of lithium-ion batteries is an effective way to solve the battery life anxiety. Since high-nickel ternary materials have a high specific capacity, they can effectively improve the energy density of lithium-ion batteries and have become an essential material for preparing the positive electrode sheets of high-capacity batteries.

[0003] However, as the nickel content in high-nickel ternary materials increases, the safety of the battery decreases significantly. In particular, high energy density and fast charging bring challenges of temperature rise. When the battery is under high load or fast charging, the internal temperature will rise rapidly. This excessive temperature will not only reduce the performance and lifespan of the battery but also may cause potential safety hazards. For example, thermal runaway may occur. Summary of the Invention

[0004] The embodiments of this application provide a battery, which can effectively reduce the temperature rise of the battery and improve the safety of the battery.

[0005] The embodiments of this application provide a battery, including: a positive electrode sheet, a negative electrode sheet, and an electrolyte;

[0006] The electrolyte includes propyl acetate and the compound shown in Formula 1;

[0007]

[0008] In Formula 1, R1 is selected from a substituted or unsubstituted C1-C10 alkyl group, a substituted or unsubstituted C1-C10 alkoxy group, a substituted or unsubstituted cyclic sulfate; when it is substituted, the substituent may be a fluorine atom or a C1-C5 alkyl group;

[0009] The mass percentage content a of the propyl acetate in the electrolyte is 5%-60%, and the mass percentage content b of the compound shown in Formula I in the electrolyte is 0.2%-5%;

[0010] The positive electrode sheet includes a positive electrode current collector and a positive electrode active coating coated on at least one surface of the positive electrode current collector. The positive electrode active coating includes a positive electrode active material, and the positive electrode active material includes Ni element; the molar percentage content c of Ni element among all transition metal elements in the positive electrode active material is 60%-95%;

[0011] The battery satisfies the following formula:

[0012] 0.15 ≤ (a + b) / c ≤ 1.

[0013] In some embodiments, a and b satisfy the formula shown below:

[0014] 5 ≤ a / b ≤ 60.

[0015] In some embodiments, the positive electrode active material includes a high-nickel ternary material, and the chemical general formula of the high-nickel ternary material is shown below:

[0016] LiNi c Co y1 Mn z1 M1 a1 O2;

[0017] Wherein, 0.8 ≤ c ≤ 0.95, 0.01 ≤ y1 ≤ 0.2, 0.01 ≤ z1 ≤ 0.2, 0 ≤ a1 ≤ 0.1, and M1 is selected from at least one of Al, Mg, Y, W, B, Zr, Ti, Sr, Si, La, and Nb.

[0018] In some embodiments, the high-nickel ternary material includes a single-crystal high-nickel ternary material and / or a polycrystalline high-nickel ternary material;

[0019] The particle size D50 of the single-crystal high-nickel ternary material is 0.5 μm to 10 μm;

[0020] And / or,

[0021] The particle size D50 of the polycrystalline high-nickel ternary material is 5 μm to 30 μm.

[0022] In some embodiments, there is a coating layer on at least part of the surface of the high-nickel ternary material, and the coating layer includes a carbon material and / or an oxide material;

[0023] The oxide material is selected from at least one of aluminum oxide, titanium oxide, and zirconium oxide.

[0024] In some embodiments, the thickness of the coating layer is 2 nm to 100 nm.

[0025] In some embodiments, the compound shown in Formula 1 includes at least one of the following compounds:

[0026]

[0027]

[0028] In some embodiments, a ceramic coating is coated on at least one side edge of the positive electrode sheet, and the ceramic coating includes a ceramic and a binder;

[0029] The ceramic includes at least one of alumina, zirconia, titanium dioxide, silicon dioxide, boron nitride, boehmite, magnesium oxide, and magnesium hydroxide;

[0030] and / or,

[0031] The mass percentage of the ceramic in the ceramic coating is 30wt%-98wt%;

[0032] and / or,

[0033] The mass ratio of the binder to the ceramic is 1%-40%;

[0034] and / or,

[0035] The D50 of the ceramic particle size is 0.1μm - 5μm;

[0036] and / or,

[0037] The size of the ceramic coating in the width direction of the positive electrode sheet is 0.5mm to 10mm.

[0038] In some embodiments, the negative electrode sheet includes:

[0039] A negative electrode current collector and a negative electrode active material layer coated on at least one surface of the negative electrode current collector, the negative electrode active material layer includes a negative electrode active material, and the negative electrode active material includes a silicon-carbon material;

[0040] The mass percentage of silicon element in the silicon-carbon material is 10wt%-80wt%;

[0041] and / or,

[0042] The D50 of the silicon-carbon material particle size is 5μm - 15μm;

[0043] and / or,

[0044] The specific surface area of the silicon-carbon material is 0.5m 2 / g - 10m 2 / g.

[0045] In some embodiments, the battery further includes at least two positive electrode tabs, and / or, at least two negative electrode tabs.

[0046] The battery provided by the embodiments of the present application contains propyl acetate and the compound shown in Formula 1 in the electrolyte, and defines the mass percentage content a of propyl acetate in the electrolyte, the mass percentage content b of the compound shown in Formula 1 in the electrolyte, and the molar percentage content c of Ni element among all transition metal elements in the positive electrode active material, satisfying 0.15 ≤ (a + b) / c ≤ 1. Through the mutual cooperation and interaction among the three, the temperature rise of the battery can be reduced, and the safety of the battery can be improved. Description of the Drawings

[0047] Figure 1 It is a schematic diagram of a ceramic layer provided in the positive electrode sheet. Detailed Embodiments

[0048] To make the objectives, technical solutions, and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are some, but not all, of the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present application.

[0049] In the embodiments of the present application, terms such as "first" and "second" are used to distinguish the same items or similar items with basically the same functions and effects, and do not limit their sequence. Those skilled in the art can understand that terms such as "first" and "second" do not limit the quantity and execution order, and "first" and "second" do not necessarily mean different.

[0050] It should be noted that in the embodiments of the present application, words such as "exemplary" or "for example" are used to represent examples, illustrations, or explanations. Any embodiment or design solution described as "exemplary" or "for example" in the present application should not be construed as being more preferred or having more advantages than other embodiments or design solutions. Exactly, using words such as "exemplary" or "for example" is intended to present relevant concepts in a specific manner.

[0051] As mentioned above, high-nickel ternary materials are excellent materials for preparing the positive electrode sheets of lithium-ion batteries. However, as the nickel content in high-nickel ternary materials increases, during the charge and discharge process of the battery, cation mixing is likely to occur. Transition metal ions in the positive electrode will also de-lithiate the lattice and enter the electrolyte during the reaction, catalyzing the oxidative decomposition of the electrolyte and damaging the passivation film on the surface of the electrode material, thereby affecting its service life. On the other hand, high-nickel ternary materials have their own oxygen release situation. The high-temperature environment accelerates the damage of metal ions and active hydrogen in the battery to the battery system, and is extremely likely to cause problems such as battery swelling and thermal runaway.

[0052] In view of the above problems, the present application provides a battery, including a positive electrode sheet, a negative electrode sheet, an electrolyte, and a separator disposed between the positive electrode sheet and the negative electrode sheet. The electrolyte includes propyl acetate and a compound represented by Formula I;

[0053]

[0054] In Formula 1, R1 is selected from a substituted or unsubstituted C1-C10 alkyl group, a substituted or unsubstituted C1-C10 alkoxy group, a substituted or unsubstituted cyclic sulfate; when being substituted, the substituent may be a fluorine atom or a C1-C5 alkyl group.

[0055] The positive electrode sheet includes a positive electrode current collector and a positive electrode active coating coated on at least one surface of the positive electrode current collector. The positive electrode active coating includes a positive electrode active material, and the positive electrode active material includes Ni element;

[0056] The mass percentage content a of propyl acetate in the electrolyte, the mass percentage content b of the compound represented by Formula I in the electrolyte, and the molar percentage content c of Ni element among all transition metal elements in the positive electrode active material satisfy the following formula:

[0057] 0.15 ≤ (a + b) / c ≤ 1.

[0058] The "C1-C10 alkyl group" in the present application refers to a cyclic alkyl group or a chain alkyl group containing 1-10 carbon atoms. The chain alkyl group may be a saturated straight-chain alkyl group or a saturated branched-chain alkyl group; it should be noted that the cyclic alkyl group contains 1-10 carbon atoms; for example, the cyclic alkyl group may be cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, decahydronaphthyl, etc.; the chain alkyl group may be methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, isopentyl, neopentyl, n-hexyl, isohexyl, n-heptyl, n-octyl, n-nonyl, n-decyl, etc.

[0059] The "C1-C10 alkoxy group" in the present application refers to a straight-chain alkoxy group or a branched-chain alkoxy group with 1-10 carbon atoms. For example, it may be methoxy, ethoxy, propoxy, etc.

[0060] The present application does not specifically limit the substitution position of the substituent in the alkyl group or alkoxy group in R1. For example, any hydrogen atom in the alkyl group can be substituted, and the number of substituted substituents is not limited.

[0061] Further, the number of carbon atoms in the alkyl group or alkoxy group in R1 is C1-C7.

[0062] The specific sources of propyl acetate and the compound shown in Formula 1 in this application are not specifically limited, and commercially available products or products prepared by conventional preparation methods well-known to those skilled in the art can be used. In this application, the positive electrode active material included in the positive electrode sheet is a high-nickel active material. For example, the molar percentage content of Ni element among all transition metal elements in the active material is 60%-95%.

[0063] Due to the high content of Ni element, during the charge and discharge process of the battery, the lithium ions are unevenly deintercalated and inserted on the surface of the positive electrode material, and the higher Ni 2+ will dissolve out, resulting in the positive electrode material having strong oxidizing properties, gradually oxidizing the solvent and additives of the electrolyte, causing the battery temperature to rise sharply under fast charge and discharge conditions. Adding the compound shown in Formula 1 to the electrolyte can form a solid electrolyte interface (CEI) film on the positive electrode during the first cycle, preventing other solvents from being oxidized by Ni 2+ oxidation, improving the overall oxidation resistance of the electrolyte, reducing side reactions, and reducing heat generation. However, the compound shown in Formula 1 has a high viscosity, resulting in the electrolyte being more likely to generate gas and affecting the fast charging performance. Further adding propyl acetate (PA) to the electrolyte, propyl acetate can reduce the viscosity of the compound shown in Formula 1. The compound of Formula 1 can preferentially decompose at high voltage to form a protective interface layer, delaying the oxidative decomposition of propyl acetate, thereby improving the overall high-voltage stability of the electrolyte. And the compound shown in Formula 1 and PA cooperate to form a denser and more stable CEI layer, inhibiting the further decomposition of the electrolyte and the dissolution of transition metals (such as Ni, Co, etc.). When the percentage content a of the compound shown in Formula 1 in the electrolyte, the percentage content b of propyl acetate in the electrolyte, and the mass percentage content c of Ni element in the active material satisfy the above relationship, it can ensure the appropriate viscosity of the electrolyte, and during the first charging process, propyl acetate assists the compound shown in Formula 1 to form a thin and dense CEI film on the positive electrode surface, reducing the temperature rise at high rates, meeting the fast charge and discharge performance of the battery, and at the same time preventing the dissolution of nickel ions during the lithium-nickel mixing process at the positive electrode and protecting the stability of the solid electrolyte interface (SEI) film of the negative electrode.

[0064] When a, b, and c do not satisfy the above relationship, if the total addition amount of propyl acetate and the compound shown in Formula 1 is low and the nickel content is high, the quality of the protective film formed by propyl acetate and the compound shown in Formula 1 on the positive electrode surface is poor. As the battery undergoes high-rate charge and discharge, it cannot effectively prevent the dissolution of positive electrode nickel ions and their deposition on the negative electrode, resulting in local heating of the battery and an increase in the cyclic temperature rise.

[0065] If the total addition amount of propyl acetate and the compound shown in Formula 1 is high and the nickel content is low, the Ni 2+Decrease, side reactions decrease, but the compound shown in Formula 1 increases. The surplus compound shown in Formula 1 continues to form a film on the positive electrode, thickening the CEI film of the battery, increasing the transmission impedance of lithium ions, and to a certain extent increasing the temperature rise, deteriorating the capacity retention rate and swelling of the battery.

[0066] In one embodiment, the compound shown in Formula 1 includes at least one of the following compounds:

[0067]

[0068] When the compound shown in Formula 1 includes the above compounds, it can be better coordinated with propyl acetate, further improving the safety of lithium-ion batteries.

[0069] In one embodiment, a and b satisfy the following formula:

[0070] 5 ≤ a / b ≤ 60.

[0071] Furthermore, a and b satisfy the following formula:

[0072] 10 ≤ a / b ≤ 30.

[0073] When the ratio of propyl acetate to the compound shown in Formula 1 satisfies the above relationship, when propyl acetate and the compound of Formula 1 are within the above formula range, Formula 1 can form a dense and thin CEI film on the positive electrode to prevent the oxidative decomposition of the electrolyte. At the same time, the excellent thermal conductivity of propyl acetate can effectively conduct heat and improve the heat dissipation efficiency. More importantly, the low viscosity of propyl acetate offsets the impedance effect caused by Formula 1 on the battery, maintaining the kinetics of the electrolyte, not deteriorating the normal temperature and low temperature performance of the battery, and improving problems such as temperature rise in high temperature cycling.

[0074] When the compound shown in Formula 1 is a mixture of the foregoing multiple compounds, the present application does not specifically limit the ratio between the specific compounds.

[0075] In one embodiment, the mass percentage content a of propyl acetate in the electrolyte is 5 wt% - 60 wt%. For example, the mass percentage content a of propyl acetate in the electrolyte can be 5 wt%, 10 wt%, 20 wt%, 30 wt%, 40 wt%, 50 wt%, 60 wt%, or a range composed of any two of the above values. When the mass percentage content of propyl acetate in the electrolyte is within the above range, propyl acetate has good thermal conductivity, can effectively conduct heat, reduce heat accumulation, and improve the heat dissipation efficiency. Moreover, propyl acetate has a high thermal decomposition temperature, which enables it to maintain stability without decomposition in a high-temperature environment and is suitable for high-temperature heat dissipation applications; propyl acetate also has a low viscosity and can effectively flow in the heat dissipation system to improve the heat transfer effect. When the proportion of propyl acetate exceeds the range, the proportion of other solvents with high dielectric constants is low, and the lithium salt and additives in the electrolyte are likely to precipitate at low temperatures.

[0076] In one embodiment, the mass percentage content b of the compound shown in Formula 1 in the electrolyte is 0.2 wt% - 5 wt%. For example, the mass percentage content b of the compound shown in Formula 1 in the electrolyte can be 0.2 wt%, 0.5 wt%, 1 wt, 1.5 wt%, 2 wt%, 2.5 wt%, 3 wt%, 3.5 wt%, 4 wt%, 4.5 wt%, 5 wt%, or a range composed of any two of the above values. When the mass percentage content of the compound shown in Formula 1 in the electrolyte is within the above range, the compound shown in Formula 1 forms a thin and tough CEI film on the surface of the positive electrode. During high-rate charge and discharge processes, it inhibits the release of active oxygen and the dissolution of Ni2+ caused by the unstable structure of the positive electrode material, and reduces the consumption of the electrolyte by these two strongly oxidizing substances. At the same time, it slows down the deposition of transition metals on the negative electrode SEI film and protects the long-term effectiveness of the SEI film. When the compound of Formula 1 exceeds the above range, it will increase the impedance of the electrolyte, deteriorate the kinetics of the electrolyte, cause lithium deposition in the battery during normal temperature and low temperature processes, and pose a safety hazard to the battery.

[0077] In one embodiment, the molar percentage content c of Ni element among all transition metal elements in the positive electrode active material is 60%-95%. For example, the molar percentage content of Ni element among all transition metal elements in the active material can be 60%, 70%, 80%, 85%, 88%, 90%, 92%, 95%, or any range composed of any two of the above values. Preferably, the molar percentage content c of Ni element among all transition metal elements in the active material is 80%-95%. When the molar percentage content of Ni element among all transition metal elements in the active material is within the above range, a higher nickel content can provide more lithium ion storage space and can significantly improve the energy density of the battery; when the nickel content of the ternary material exceeds the range, the crystal structure of the ternary material is more likely to change, and it is easy to release oxygen under high temperature, high pressure and long cycles, resulting in a series of oxidation reactions of the electrolyte and a sharp rise in the battery temperature.

[0078] In one embodiment, the positive electrode active material includes a high-nickel ternary material, and the chemical general formula of the high-nickel ternary material is as follows:

[0079] LiNi c Co y1 Mn z1 M1 a1 O2;

[0080] Wherein, 0.8≤c≤0.95, 0.01≤y1≤0.2, 0.01≤z1≤0.2, 0≤a1≤0.1.

[0081] When the chemical formula of the high-nickel ternary material is controlled within the range, a higher nickel content can provide more lithium ion storage space and can significantly improve the energy density of the battery, thereby enhancing the overall energy output of the battery. The increase in Ni content can improve the material capacity but will reduce the cycle performance and stability. The increase in Co content can inhibit phase change and improve the rate performance. The increase in Mn content is beneficial to improving the structural stability and prolonging the battery life.

[0082] Wherein, M1 is selected from at least one of Al, Mg, Y, W, B, Zr, Ti, Sr, Si, La and Nb. Doping the high-nickel ternary material with M1 can effectively improve the crystal structure of the material, make it more stable during long-term use, and slow down the capacity decay. Moreover, the doping element can improve the electrical conductivity of the material. In the application scenario of high-power output, the electrochemical performance can be significantly improved.

[0083] In one embodiment, the high-nickel ternary material includes single-crystal high-nickel ternary material and / or polycrystalline high-nickel ternary material. For example, the high-nickel ternary material is entirely composed of single-crystal high-nickel ternary material, or the high-nickel ternary material is entirely composed of polycrystalline high-nickel ternary material, or the high-nickel ternary material is composed of a mixture of single-crystal high-nickel ternary material and polycrystalline high-nickel ternary material. Using single-crystal high-nickel ternary material and / or polycrystalline high-nickel ternary material, because single crystals and polycrystals each have their own advantages. The advantages of single-crystal materials: The structure of single-crystal materials is more uniform, with fewer grain boundaries, which can effectively reduce the diffusion resistance of lithium ions during charge and discharge. Therefore, the capacity and energy density of the battery can be effectively improved. Compared with single-crystal materials, polycrystalline materials, although slightly inferior in some properties, also have many advantages: Polycrystalline materials have relatively good conductivity, and because the crystal structure of polycrystalline materials has more grains, it can better disperse stress and reduce damage during battery use.

[0084] In one embodiment, the D50 particle size of the single-crystal high-nickel ternary material is 0.5 μm to 10 μm. For example, the D50 particle size of the single-crystal high-nickel ternary material can be 0.5 μm, 1 μm, 1.5 μm, 2 μm, 3 μm, 5 μm, 7 μm, 9 μm, 10 μm, or a range composed of any two of the above values.

[0085] In one embodiment, the D50 particle size of the polycrystalline high-nickel ternary material is 5 μm to 30 μm. For example, the D50 particle size of the single-crystal high-nickel ternary material can be 5 μm, 8 μm, 10 μm, 12 μm, 15 μm, 18 μm, 20 μm, 25 μm, 30 μm, or a range composed of any two of the above values.

[0086] Among them, the D50 particle size is the particle size at which the cumulative particle volume distribution is 50%, and the D50 particle size can be obtained by testing with a Malvern 3000 laser particle size analyzer.

[0087] When the D50 particle size of the single-crystal high-nickel ternary material and / or the polycrystalline high-nickel ternary material is within the above range, the ternary material has a relatively large specific surface area, providing more reactive sites during charge and discharge, thereby increasing the discharge capacity of the battery. Moreover, the lithium-ion diffusion path is shortened, increasing the diffusion speed of lithium ions in the material, which is beneficial for high-rate charge and discharge.

[0088] In one embodiment, at least part of the surface of the high-nickel ternary material is coated with a coating layer; the coating layer includes carbon material and / or oxide material.

[0089] Among them, the oxide material is selected from at least one of aluminum oxide (for example, Al2O3), titanium oxide (for example, TiO2), and zirconium oxide (ZrO2).

[0090] Coating the surface of high-nickel ternary materials with carbon materials can significantly improve the conductivity of high-nickel ternary materials because carbon materials themselves have good conductivity. And as the battery charge-discharge cycle progresses, the carbon material coating layer can effectively slow down the decline in conductivity. Coating the surface of high-nickel ternary materials with oxide materials can prevent the direct contact between propyl acetate and the compound shown in Formula I and the positive electrode material, inhibit the release of oxygen, reduce the oxidation phenomenon of the positive electrode material, and prevent the oxidation and decomposition reaction of the electrolyte. It can improve the stability of the interface, which helps to extend the service life of the battery and further improve the temperature rise problem. Coating the core with carbon materials and oxide materials simultaneously can balance conductivity and temperature rise to a certain extent and further improve the performance of the battery.

[0091] In one embodiment, the thickness of the coating layer is 2 nm to 100 nm. For example, the thickness of the coating layer can be 2 nm, 5 nm, 10 nm, 30 nm, 50 nm, 70 nm, 90 nm, 100 nm, or any range composed of any two of the above values. If the coating layer is too thick, it will increase the lithium-ion exchange impedance of the battery and reduce the lithium-ion insertion / extraction rate. However, if the coating layer is too thin, the toughness of the film will be insufficient, and it will continuously break and repair during the insertion / extraction process, reducing the charge-discharge efficiency.

[0092] In one embodiment, a ceramic coating including ceramic and binder is coated on at least one side edge of the positive electrode sheet. By coating the ceramic coating on the positive electrode sheet, with the help of the high heat conduction efficiency of the ceramic coating, the heat generated inside the battery can be quickly dispersed, avoiding heat concentration in a certain part of the battery, reducing the temperature fluctuation of the battery, further improving the temperature rise problem, and thus enhancing the overall stability of the battery.

[0093] In one embodiment, the mass percentage of the ceramic in the ceramic coating is 30 wt% - 98 wt%. For example, the mass percentage of the ceramic in the ceramic coating can be 30 wt%, 40 wt, 45 wt%, 50 wt%, 55 wt%, 60 wt%, 65 wt%, 70 wt%, 75 wt%, 80 wt%, 85 wt%, 90 wt%, 92 wt%, 95 wt%, 98 wt%, or any range composed of any two of the above values.

[0094] In one embodiment, the binder accounts for 1% - 40% of the mass of the ceramic. For example, the binder may account for 1%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40% of the mass of the ceramic, or any range composed of any two of the above values. If the binder content is too low, the adhesion between ceramic particles will be poor, and ceramic shedding is likely to occur. If the binder content is too high, the heat dissipation effect of the ceramic will be reduced.

[0095] In one embodiment, the D50 particle size of the ceramic is 0.1 μm - 5 μm. For example, the Dv50 particle size of the ceramic may be 0.1 μm, 0.5 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm, or any range composed of any two of the above values. If the particle size of the ceramic is too large, the porosity of the separator material will be reduced, thereby reducing the gas permeability and ionic conductivity of the separator. Large particles may cause the pore structure of the separator to be uneven, and uneven porosity may lead to local overheating or poor electrolyte flow, affecting the stability and efficiency of the battery. If the ceramic particles are too small, the overall mechanical strength of the separator may decrease. Since the surface area of small particles is relatively large, phenomena such as thermal expansion or crystallization may easily occur, resulting in a decrease in the thermal stability of the separator.

[0096] In one embodiment, the ceramic includes an oxide and / or hydroxide containing element M. For example, the ceramic includes one or more of alumina, zirconia, titanium dioxide, silicon dioxide, boron nitride, boehmite, magnesium oxide, and magnesium hydroxide.

[0097] In one embodiment, the binder is selected from at least one of olefin wax emulsions, polyvinylidene fluoride, polytetrafluoroethylene, polyvinylidene fluoride - hexafluoropropylene copolymer, acrylic resin, polyurethane, sodium carboxymethyl cellulose, lithium carboxymethyl cellulose, polymethyl methacrylate, and polydimethylsiloxane.

[0098] In one embodiment, as Figure 1 shown, when a ceramic layer 2 is provided on one long side of the positive electrode sheet 1, the size L of the ceramic layer in the width direction of the positive electrode sheet is 0.5 mm - 10 mm, and the width direction of the positive electrode sheet is the direction of the relatively short side of the electrode sheet size. For example, the size of the ceramic layer is 0.5 mm, 1 mm, 3 mm, 5 mm, 8 mm, 10 mm, or any range composed of any two of the above values. When the size of the ceramic layer in the width direction of the positive electrode sheet is within the above range, it is possible to prevent the energy density of the battery from being reduced due to too large a width of the ceramic layer.

[0099] In one embodiment, the negative electrode sheet includes: a negative electrode current collector, and a negative electrode active material layer coated on at least one surface of the negative electrode current collector. The negative electrode active material layer includes a negative electrode active material, and the negative electrode active material includes a silicon-carbon material. Carbon materials (such as graphite, carbon nanotubes, carbon fibers, etc.) have good electrical conductivity. Although silicon material itself has lower electrical conductivity than carbon, after being compounded with carbon materials, it can maintain good electronic conductivity and improve the conductive problems that silicon may encounter during charge and discharge. Therefore, using silicon-carbon materials can reduce the internal resistance of the battery and improve the charging and discharging efficiency of the battery.

[0100] In one embodiment, the mass percentage of silicon element in the silicon-carbon material is 10wt%-80wt%. For example, the mass percentage of silicon element can be 10wt%, 20wt, 30wt%, 40wt%, 50wt%, 60wt%, 70wt%, 80wt%, or any range composed of any two of the above values. The conductivity of silicon element is relatively high. When the mass percentage of silicon element in the silicon-carbon material is within the above range, the temperature rise problem during high-current charge and discharge of the battery can be reduced.

[0101] In one embodiment, the D50 particle size of the silicon-carbon material is 5μm-15μm. For example, the D50 particle size of the silicon-carbon material can be 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, 11μm, 12μm, 15μm, or any range composed of any two of the above values. The larger the particle size of the silicon material, the easier it is to expand and break, the worse the kinetics, and the easier it is to cause lithium plating on the negative electrode. When the particle size of the silicon material is adjusted within the above range, the extrusion of the separator caused by excessive expansion of the silicon material can be reduced, and the blocking of the separator pores can be reduced; it can also reduce the breakage of the negative electrode material, improve the kinetic performance of the battery, and reduce lithium plating on the negative electrode.

[0102] In one embodiment, the specific surface area of the silicon-carbon material is 0.5m 2 / g - 10m 2 / g. For example, the specific surface area of the silicon-carbon material can be 0.5m 2 / g, 1m 2 / g, 3m 2 / g, 5m 2 / g, 8m 2 / g, 10m 2 / g, or any range composed of any two of the above values. When the specific surface area of the silicon material is adjusted within the above range, the contact area between the silicon-carbon material and the electrolyte increases, the resistance of ion migration is reduced, and thus the charging and discharging rates are improved. Moreover, the large specific surface area provides more active sites, reduces the structural change of the electrode material, and reduces the damage caused by volume expansion or contraction during charge and discharge, thereby improving the cycle life of the battery.

[0103] In one embodiment, the battery further comprises at least two positive electrode tabs, and / or at least two negative electrode tabs.

[0104] Among them, at least two positive pole tabs are independently connected to the positive current collector in the positive electrode sheet, and at least two negative pole tabs are independently connected to the negative current collector in the negative electrode sheet. Through the design of the multi-pole tab structure, the contact area of ​​the pole tab can be increased, and the contact resistance between the electrode and the external circuit is significantly reduced. This helps to improve the current density and the energy transmission efficiency of the battery and reduce energy loss. In addition, since the multi-pole tab structure can effectively reduce the generation of local hot spots, reduce the mechanical fatigue and chemical aging of the material, it helps to extend the cycle life and overall stability of the battery.

[0105] The following is a detailed introduction to the battery provided in the present application through specific embodiments.

[0106] Example 1

[0107] (1) Preparation of electrolyte

[0108] In a glove box (H2O<0.01ppm, O2<0.01ppm, Ar atmosphere), ethylene carbonate (EC), propylene carbonate (PC) and ethyl propionate (EP) were mixed in a mass ratio of 12:10:20, and 36% of propyl acetate (PA) based on the total mass of the electrolyte, 12% of fully dried lithium hexafluorophosphate (LiPF6) and 18% of the second additive (including 3% of the compound shown in Formula 1-1, 8% of fluoroethylene carbonate (FEC), 2% of propane sultone (PS), 0.5% of MDTD, 0.5% of lithium difluorophosphate (LiPO2F2), 4% of lithium bis(fluorosulfonyl)imide (LiFSI)) were added thereto, stirred evenly, and the electrolyte was obtained after passing the moisture and free acid tests.

[0109] (2) Preparation of negative electrode sheet

[0110] The negative electrode active material (artificial graphite + silicon carbon), conductive carbon black, styrene-butadiene rubber and sodium carboxymethyl cellulose are mixed evenly in a mass ratio of 98:1:0.5:0.5, deionized water is added, and the mixture is fully stirred to form a uniform negative electrode slurry; the negative electrode slurry is coated on a copper foil, and the negative electrode sheet is obtained after drying, rolling, cutting, cleaning and adhesive tape.

[0111] (3) Preparation of positive electrode sheet

[0112] The positive electrode active material (LiNi 0.9 Co 0.05 Mn 0.05O2), conductive carbon black, and polyvinylidene fluoride are mixed evenly in a mass ratio of 98:1.2:0.8, dispersed in N-methylpyrrolidone (NMP), and stirred thoroughly to form a uniform positive electrode paste. The positive electrode paste is coated on aluminum foil, dried, rolled, cut, washed, and pasted with adhesive tape to obtain a positive electrode sheet. In this positive electrode active material, the content of Ni element is 90%.

[0113] (4) Preparation of the battery

[0114] The negative electrode sheet prepared in step (2), the positive electrode sheet prepared in step (3), and a separator (such as a commercially available conventional separator) are wound around a core according to a predetermined process, and the electrolyte prepared in step (1) is injected. After processes such as vacuum sealing, standing, formation, sorting, and secondary sealing, the battery is prepared.

[0115] The preparation methods of the lithium-ion batteries in Examples 2 - 16 are basically the same as those in Example 1, except that the structure and content of the compound shown in Formula 1 and the content of propyl acetate are different. The specific adjustments are shown in Table 1.

[0116] The preparation methods of the lithium-ion batteries in Examples 17 - 30 are basically the same as those in Example 1, except that the particle size of the high-nickel ternary material, the thickness of the coating layer, and the parameters of the ceramic layer are different. The specific adjustments are shown in Table 2.

[0117] The preparation methods of the lithium-ion batteries in Examples 31 - 35 are basically the same as those in Example 1, except that the parameters of the negative electrode sheet and the number of tabs are different. The specific adjustments are shown in Table 3.

[0118] Comparative Example 1. The preparation method of the lithium-ion battery in this comparative example is basically the same as that in Example 1, except that propyl acetate is not included in the electrolyte.

[0119] Comparative Example 2. The preparation method of the lithium-ion battery in this comparative example is basically the same as that in Example 1, except that the compound shown in Formula 1-1 is not included in the electrolyte.

[0120] Comparative Example 3. The preparation method of the lithium-ion battery in this comparative example is basically the same as that in Example 1, except that the compound shown in Formula 1-1 and propyl acetate are not included in the electrolyte.

[0121] Comparative Example 4. The preparation method of the lithium-ion battery in this comparative example is basically the same as that in Example 1, except that the content of the compound shown in Formula 1-1 in the electrolyte is adjusted to 0.05 wt%, and the content of propyl acetate in the electrolyte is adjusted to 3 wt%.

[0122] Comparative Example 5. The preparation method of the lithium-ion battery in this comparative example is basically the same as that of Example 1, except that the content of the compound shown in Formula 1-1 in the electrolyte is adjusted to 8 wt%, and the content of propyl acetate in the electrolyte is adjusted to 65 wt%.

[0123] Comparative Example 6. The preparation method of the lithium-ion battery in this comparative example is basically the same as that of Example 1, except that the content of the compound shown in Formula 1-1 in the electrolyte is adjusted to 1 wt%, and the content of propyl acetate in the electrolyte is adjusted to 8 wt%.

[0124] Test Example

[0125] 1. Test the temperature rise of the lithium-ion batteries in Examples 1-43 and the lithium-ion batteries in Comparative Examples 1-6.

[0126] Temperature rise test: At an ambient temperature of 25°C, discharge the battery to the lower limit voltage at 0.5C, and let it stand for 60 min; charge the battery to the upper limit voltage at 2C, keep the voltage constant until 0.05C, and let it stand for 30 min; discharge the battery to the lower limit voltage at the rate of discharge, rate = {0.5C / 4C / }, and measure the change in the temperature of the battery body. The specific test results are shown in Table 6.

[0127] Table 1

[0128]

[0129]

[0130] Table 2

[0131]

[0132] Table 3

[0133]

[0134]

[0135] Table 4

[0136] Temperature Rise (°C) Temperature Rise (°C) Example 1 3 Example 22 7 Example 2 4 Example 23 8 Example 3 4 Example 24 8 Example 4 5 Example 25 10 Example 5 10 Example 26 11 Example 6 8 Example 27 6 Example 7 9 Example 28 8 Example 8 10 Example 29 12 Example 9 10 Example 30 10 Example 10 11 Example 31 5 Example 11 8 Example 32 6 Example 12 7 Example 33 8 Example 13 6 Example 34 7 Example 14 7 Example 35 7 Example 15 8 Comparative Example 1 15 Example 16 8 Comparative Example 2 16 Example 17 5 Comparative Example 3 18 Example 18 6 Comparative Example 4 17 Example 19 6 Comparative Example 5 18 Example 20 7 Comparative Example 6 13 Example 21 8

[0137] As can be seen from Table 1 and Table 4, compared with Comparative Examples 1-3, in Examples 1-16, after adding propyl acetate and the compound shown in Formula 1 to the electrolyte, under the same temperature rise experiment, the average temperature rise of the batteries prepared in Examples 1-16 is 6.6°C, and the average temperature rise of the batteries prepared in Comparative Examples 1-3 is 16.3°C. It can be seen that after adding propyl acetate and the compound shown in Formula 1 to the electrolyte, the temperature rise problem of the battery during the cycle can be effectively alleviated, and the safety of the battery can be improved.

[0138] Further, compared with Comparative Examples 4-6, in Examples 1-16, after adding propyl acetate and the compound shown in Formula 1 to the electrolyte, the ratio of the contents of propyl acetate, the compound shown in Formula 1, and Ni element is in the range of 0.15-1, which can further alleviate the temperature rise problem during the cycling of the battery and improve the safety of the battery.

[0139] Further, compared with Examples 7, 8, 9, 10, 15 and the remaining examples in Table 1, when the ratio of propyl acetate, the compound shown in Formula 1, and Ni element is in the range of 0.15-1, and the mass ratio of propyl acetate and the compound shown in Formula 1 is in the range of 5-60, the temperature rise of the batteries in the remaining examples in Table 1 is all below 9°C, which can further alleviate the temperature rise problem during the cycling of the battery and improve the safety of the battery.

[0140] As can be seen from Table 2 and Table 4, compared with Examples 21 and 22 (average temperature rise of 7.5°C), and Examples 1, 17 and 18 (average temperature rise of 4.6°C), when the D50 of the single crystal high-nickel ternary material is in the range of 0.5 μm to 10 μm and / or the D50 of the polycrystalline high-nickel ternary material is in the range of 5 μm to 30 μm, the temperature rise during the cycling of the battery can be effectively reduced.

[0141] Further, compared with Examples 25 and 26 (average temperature rise of 10.5°C), and Examples 1, 23 and 24 (average temperature rise of 6.3°C), when the thickness of the coating layer present on at least part of the surface of the high-nickel ternary material is in the range of 2 nm to 100 nm, the temperature rise during the cycling of the battery can be effectively reduced.

[0142] Further, compared with Examples 29 and 30 (average temperature rise of 11°C), and Examples 1, 27 and 28 (average temperature rise of 5.6°C), when the D50 of the ceramic is 0.1 μm - 5 μm, and the size of the ceramic coating in the width direction of the positive electrode sheet is in the range of 0.5 mm to 10 m, the temperature rise during the cycling of the battery can be effectively reduced.

[0143] As can be seen from Table 3 and Table 4, compared with Examples 33 and 34 (average temperature rise of 7.5°C), and Examples 1, 31 and 32 (average temperature rise of 4.6°C), the mass percentage content of silicon element in the silicon-carbon material is 10 wt% - 80 wt%, the D50 of the silicon-carbon material is in the range of 5 μm - 15 μm, and the specific surface area of the silicon-carbon material is in the range of 0.5 m 2 / g - 10 m 2 / g, the temperature rise during the cycling of the battery can be effectively reduced.

[0144] Furthermore, compared with Example 35 (temperature rise of 7°C) and Example 1 (temperature rise of 3°C), the battery adopts a multi-tab design method, which can effectively reduce the temperature rise of the battery during cycling, thereby contributing to extending the cycle life and overall stability of the battery.

[0145] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements 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 sheet, a negative electrode sheet, and an electrolyte, characterized in that: The electrolyte includes propyl acetate and a compound shown in Formula 1; In Formula 1, R1 is selected from substituted or unsubstituted C1-C10 alkyl, substituted or unsubstituted C1-C10 alkoxy, substituted or unsubstituted cyclic sulfate; if substituted, the substituent may be a fluorine atom, a C1-C5 alkyl; The mass percentage a of the propyl acetate in the electrolyte is 5%-60%, and the mass percentage b of the compound represented by Formula 1 in the electrolyte is 0.2%-5%; The positive electrode sheet comprises a positive electrode current collector and a positive electrode active coating coated on at least one surface of the positive electrode current collector, wherein the active coating comprises a positive electrode active material, wherein the positive electrode active material comprises a Ni element, and the molar percentage c of the Ni element in all transition metal elements in the positive electrode active material is 60%-95%; The battery shown satisfies the following formula: 0.15≤(a+b) / c≤1.

2. The battery according to claim 1, characterized in that The a and the b satisfy the following formula: 5≤a / b≤60.

3. The battery according to claim 1, characterized in that The positive electrode active material includes a high-nickel ternary material, and the chemical formula of the high-nickel ternary material is as follows: LiNi c Co y1 Mr z1 M1 a1 O2; Among them, 0.8≤c≤0.95, 0.01≤y1≤0.2, 0.01≤z1≤0.2, 0≤a1≤0.1, and M1 is selected from at least one of Al, Mg, Y, W, B, Zr, Ti, Sr, Si, La and Nb.

4. The battery according to claim 3, characterized in that The high-nickel ternary material includes single crystal and / or polycrystal; the particle size D50 of the single crystal is 0.5 μm to 10 μm; And / or, the grain size D50 of the polycrystal is 5 μm to 30 μm.

5. The battery according to claim 4, characterized in that A coating layer is present on at least part of the surface of the high-nickel ternary material, and the coating layer includes at least one of a carbon material, an aluminum oxide, a titanium oxide, and a zirconium oxide.

6. The battery according to claim 5, characterized in that The coating layer has a thickness of 2nm to 100nm.

7. The battery according to any one of claims 1 to 6, characterized in that: The compound represented by Formula 1 includes at least one of the following compounds:

8. The battery according to claim 1 or 2, characterized in that: A ceramic coating is coated on at least one side edge of the positive electrode sheet, wherein the ceramic coating comprises ceramic, and the ceramic comprises at least one of aluminum oxide, zirconium oxide, titanium dioxide, silicon dioxide, boron nitride, boehmite, magnesium oxide, and magnesium hydroxide; And / or, the particle size D50 of the ceramic is 0.1 μm-5 μm; and / or, the dimension of the ceramic coating in the width direction of the positive electrode sheet is 0.5 mm to 10 mm.

9. The battery according to claim 1 or 2, characterized in that: The negative electrode sheet comprises a negative electrode current collector and a negative electrode active material layer coated on at least one side of the negative electrode current collector, wherein the negative electrode active material layer comprises a negative electrode active material, and the negative electrode active material comprises a silicon-carbon material; The mass percentage of silicon element in the silicon-carbon material is 10wt%-80wt%; And / or, the particle size D50 of the silicon-carbon material is 5 μm-15 μm; And / or, the specific surface area of ​​the silicon-carbon material is 0.5 m 2 / g-10m 2 / g.

10. The battery according to claim 1 or 2, characterized in that: The battery also includes at least two positive electrode tabs and / or at least two negative electrode tabs.

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