Lithium-ion batteries and power consumption devices having improved electrolyte viscosity and CB value

Abstract

The present application relates to a lithium ion battery, comprising a positive electrode, a negative electrode and an electrolyte, wherein the viscosity c of the electrolyte at 25°C is 1-6 mPa.s, and the ratio CB between the lithium absorption capacity of the negative electrode and the lithium desorption capacity of the positive electrode is 1.05-1.5, measured according to GB / T10247-2008. The present application further relates to a power consuming device. The lithium ion battery has a high-rate fast charging capability and good cycle performance.

Description

Technical Field

[0001] This application relates to the technical field of lithium batteries, and particularly to lithium-ion batteries and power-consuming devices.

Background Art

[0002] In recent years, as the application range of lithium-ion batteries has become increasingly wide, lithium-ion batteries have been widely applied in many fields such as energy storage power systems for hydropower, thermal power, wind power, and solar power plants, and electric tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, and aerospace. However, compared with conventional fuel oil-driven devices, problems such as range anxiety and long charging time have become the main problems hindering the development of secondary batteries, and how to improve the rapid charging ability of secondary batteries is one of the key issues that those skilled in the art are concerned about.

[0003] Improving the rapid charging ability of batteries is a system engineering, and changes and upgrades of battery materials are required. In the prior art, the improvement of the anode material has been the most studied, but the formulation of materials such as electrolyte and conductive agent is also indispensable. Therefore, there is a need to further improve the conventional batteries with rapid charging ability.

Summary of the Invention

[0004] This application is made in view of the above problems, and its purpose is to provide a lithium-ion battery having improved electrolyte viscosity and CB value, which includes an electrolyte with a specific viscosity and has a ratio CB of the lithium storage capacity of the anode and the lithium desorption capacity of the cathode within a specific range, so that the corresponding battery has a high-rate rapid charging ability and good cycle performance.

[0005] To achieve the above object, this application provides a lithium-ion battery and a power-consuming device including the same.

[0006] A first aspect of this application provides a lithium-ion battery comprising a positive electrode, a negative electrode, and an electrolyte, wherein the viscosity c of the electrolyte at 25°C is 1-6 mPa·s, and the ratio CB of the lithium storage capacity of the negative electrode to the lithium desorption capacity of the positive electrode is 1.05-1.5.

[0007] The lithium-ion battery of this application improves the high-rate rapid charging capability and cycle performance of the battery by including an electrolyte of a specific viscosity and having a ratio CB between the lithium-absorbable capacity of the negative electrode and the lithium-desorbable capacity of the positive electrode within a specific range, thereby improving the liquid-phase transport conditions of lithium ions and providing more active sites for lithium-ion absorption in the negative electrode.

[0008] In any embodiment, during the charging process of the battery from 0% charge to 70% charge at 35°C, a current exists that is four times or more the lithium desorbable capacity of the positive electrode within a unit time. This ensures further improvement in the high-rate rapid charging capability and cycle performance of the battery.

[0009] In any embodiment, the average current during the charging process of the battery from 0% charge to 70% charge at 35°C is at least four times the positive electrode's absorbable / desorbable capacity per unit time. This ensures further improvements in the battery's high-rate rapid charging capability and cycle performance.

[0010] In any embodiment, the negative electrode includes a current collector and a negative electrode active material layer attached to at least one surface of the current collector, negative electrode The active material layer includes a first active material layer containing a first negative electrode active material, and a second active material layer containing a second negative electrode active material, which is attached to the surface of the first active material layer away from the current collector. This improves the high-rate fast-charging capability and cycle performance of the battery by providing more active sites for lithium-ion intercalation at the negative electrode.

[0011] In any embodiment, the average volume particle size D of the first negative electrode active material v50This is the average volume particle size D of the second negative electrode active material. v50 This is larger than the above. This improves the high-rate fast-charging capability and cycle performance of the battery by providing even more active sites for lithium-ion storage at the anode.

[0012] In any embodiment, the following The activity The compaction density of the material layer is second The activity This is greater than the compaction density of the material layer. This can improve the high-rate fast-charging capability and cycle performance of the battery by providing even more active sites for lithium-ion intercalation at the anode.

[0013] In any embodiment, the thickness of the negative electrode active material layer is 30-150 μm, the porosity is 20-60%, and the compaction density is 1.2-1.9 g / cm³. 3 This improves the high-rate fast-charging capability and cycle performance of the battery by providing even more active sites for lithium-ion storage at the negative electrode.

[0014] In any embodiment, the electrolyte comprises a lithium salt, a solvent, and an additive, wherein the lithium salt comprises a main lithium salt and a secondary lithium salt. This further improves the liquid phase transport conditions of lithium ions, thereby improving the high-rate rapid charging capability and cycle performance of the battery.

[0015] In any embodiment, the main lithium salt and the secondary lithium salt are different, and the main lithium salt and the secondary lithium salt are each independently selected from at least one of LiPF6, LiN(SO2F)2, LiBF4, LiN(CF3SO2)2, LiClO4, LiAsF6, LiB(C2O4)2, LiBF2C2O4, LiDFOP, LiPO2F2, LiFSO3, and LiF. This further improves the liquid phase transport conditions for lithium ions, thereby improving the high-rate rapid charging capability and cycle performance of the battery.

[0016] In any embodiment, the main lithium salt is lithium hexafluorophosphate or LiFSI, and its content is 8-20 wt% based on the total weight of the electrolyte, and the secondary lithium salt is at least one of lithium difluoro(oxalato)borate, LiBF4, LiB(C2O4)2, and lithium difluorobis(oxalato)phosphate (LiDFOP), and its content is 0.001 wt%-2 wt% based on the total weight of the electrolyte. This further improves the liquid phase transport conditions of lithium ions, thereby improving the high-rate rapid charging capability and cycle performance of the battery.

[0017] In any embodiment, the solvent comprises a cyclic ester and a linear ester, wherein the cyclic ester accounts for 5-40% of the solvent mass and the linear ester accounts for 60-95% of the solvent mass. This further improves the viscosity of the electrolyte, thereby improving the liquid phase transport conditions for lithium ions, and thereby improving the high-rate rapid charging capability and cycle performance of the battery.

[0018] In any embodiment, the cyclic ester is ethylene carbonate, propylene carbonate, or a combination thereof, and the linear ester includes dimethyl carbonate. This further improves the viscosity of the electrolyte, thereby improving the liquid phase transport conditions for lithium ions, and thereby improving the high-rate rapid charging capability and cycle performance of the battery.

[0019] In any embodiment, the linear ester is selected from diethyl carbonate, ethyl methyl carbonate, methyl formate, methyl acetate, ethyl acetate, butyl acetate, methyl propionate, methyl butyrate, ethyl butyrate, propyl butyrate, butyl butyrate, isopropyl acetate, isoamyl acetate, and combinations thereof. This further improves the viscosity of the electrolyte, thereby improving the liquid phase transport conditions for lithium ions, and thereby improving the high-rate rapid charging capability and cycle performance of the battery.

[0020] In any embodiment, the molar concentration b (mol / L) of the lithium salt in the electrolyte, the percentage a% of the linear ester relative to the solvent mass in the solvent, and the viscosity c of the electrolyte at 25°C satisfy the following relationship, i.e. 2 ≤ c + 2 * a % ≤ 8, 2 ≤ c + b ≤ 8. This allows for further improvement of the electrolyte viscosity, thereby improving the liquid phase transport conditions for lithium ions, and consequently improving the high-rate rapid charging capability and cycle performance of the battery.

[0021] In any embodiment, the positive electrode includes a current collector and a positive electrode active material layer comprising a positive electrode active material attached to at least one surface of the current collector, wherein the positive electrode active material has the formula LiNi x Co y Q z M 1-x-y-z The material contains a ternary material O2, where Q is Mn or Al, and M is at least one of Co, Ni, Mn, Mg, Cu, Zn, Al, Sn, B, Ga, Cr, Sr, V, and Ti, with 0 ≤ x < 1, 0 ≤ y ≤ 1, 0 ≤ z ≤ 1, and x + y + z ≤ 1. This further improves the high-rate fast charging capability and cycle performance of the battery.

[0022] A second aspect of this application provides a power consumption device including a secondary battery selected from the first aspect of this application.

[0023] The secondary battery of this application improves the liquid phase transport conditions of lithium ions, rapidly moves lithium ions to the negative electrode, and provides more active sites for lithium ion storage at the negative electrode, thereby improving the high-rate rapid charging capability and cycle performance of the battery, by including an electrolyte of a specific viscosity and having a ratio CB of lithium-absorbable capacity of the negative electrode to lithium-desorbable capacity of the positive electrode within a specific range. [Brief explanation of the drawing]

[0024] [Figure 1] This is a schematic diagram of a secondary battery according to one embodiment of the present application. [Figure 2] Figure 1 is an exploded view of a secondary battery according to one embodiment of this application. [Figure 3] This is a schematic diagram of a power consumption device in which a secondary battery is used as a power source according to one embodiment of this application. [Modes for carrying out the invention]

[0025] The following describes in detail embodiments of the lithium-ion battery and power consumption device disclosed in this application, with appropriate reference to the drawings. However, unnecessary detailed explanations may be omitted. For example, detailed explanations of well-known matters and redundant explanations of structures that are actually the same may be omitted. This is to avoid making the following explanation unnecessarily long and to make it easily understandable to those skilled in the art. The drawings and the following explanation are provided to enable those skilled in the art to fully understand this application and do not limit the topics described in the claims.

[0026] The “range” disclosed in this application is limited in the form of a lower limit and an upper limit, and a given range is limited by selecting one lower limit and one upper limit, which define the boundary of a particular range. The range thus limited may or may not include the endpoints, and any combination is possible, that is, any lower limit can be combined with any upper limit to form a range. For example, if the ranges 60-120 and 80-110 are listed for a particular parameter, it is understood that the ranges 60-110 and 80-120 can also be assumed. Furthermore, if the minimum range values ​​are listed as 1 and 2, and the maximum range values ​​are listed as 3, 4 and 5, then the ranges 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5 can all be assumed. In this application, unless otherwise specified, the numerical range “ab” represents an abbreviation for any combination of real numbers a to b, where a and b are both real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have already been listed in this specification, and "0-5" is simply an abbreviated representation of combinations of these numbers. Also, when a parameter is described as an integer ≥ 2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc. Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical inventions.

[0027] Unless otherwise specified, all technical features and optional technical features of this application can be combined to form new technical concepts.

[0028] Unless otherwise specified, all steps of this application may be performed sequentially or randomly, preferably sequentially. For example, the fact that the method includes steps (a) and (b) means that the method may include steps (a) and (b) performed sequentially, or steps (b) and (a) performed sequentially. For example, the fact that the method mentioned above may further include step (c) means that step (c) may be added to the method in any order, for example the method may include steps (a), (b) and (c), or steps (a), (c) and (b), or steps (c), (a) and (b), etc.

[0029] Unless otherwise specified, the terms “includes” and “inclusion” as used in this application may be open or closed. For example, “includes” and “inclusion” may mean that other components not listed may be included or inclusion, or that only the listed components may be included or inclusion.

[0030] Unless otherwise specified, the term "or" is inclusive in this application. For example, the phrase "A or B" means "A, B, or both A and B." More specifically, the conditions A is true (or exists) and B is false (or does not exist), the condition A is false (or does not exist) but B is true (or exists), and the condition both A and B are true (or exist) all satisfy "A or B."

[0031] Currently, compared to conventional fuel-oil-powered devices, issues such as limited driving range and long charging times are major obstacles to the development of secondary batteries, and improving the rapid charging capability of secondary batteries is a key issue of interest to those skilled in the art. Improving the rapid charging capability of batteries is a matter of systems engineering and requires changes or upgrades to the battery materials. In the prior art, improvements to the negative electrode material have been the most extensively studied, but the formulation of materials such as the electrolyte and conductive agents is also essential. Therefore, there is a need to further improve conventional batteries with rapid charging capability. Through research, the inventors have discovered that a lithium-ion battery of the first embodiment of this application, containing an electrolyte of a specific viscosity and having a ratio CB of lithium absorbable capacity of the negative electrode to lithium desorbable capacity of the positive electrode within a specific range, has a high-rate rapid charging capability and good cycle performance.

[0032] Lithium-ion battery In some embodiments, the present application provides a lithium-ion battery comprising a positive electrode, a negative electrode, and an electrolyte, wherein the viscosity c of the electrolyte at 25°C, as measured according to GB / T10247-2008, is 1–6 mPa.s, preferably 2–5 mPa.s, and more optionally 3.5–4 mPa.s, and the ratio CB of the lithium-absorbable capacity of the negative electrode to the lithium-desorbable capacity of the positive electrode is 1.05–1.5, more optionally 1.1–1.3, and more optionally 1.1–1.2.

[0033] The lithium-ion battery of this application contains an electrolyte of a specific viscosity and has a ratio CB between the lithium-absorbable capacity of the negative electrode and the lithium-desorbable capacity of the positive electrode within a specific range, thereby enabling good and rapid infiltration and suck-back of the positive and negative electrodes, improving the liquid phase transport conditions for lithium ions, and providing more active sites for lithium-ion absorption in the negative electrode, thereby improving the high-rate rapid charging capability and cycle performance of the battery.

[0034] In this application, the term "lithium - desorbable capacity of the positive electrode" means the actual lithium - desorbable capacity of the positive electrode material in a battery. The test method is as follows. Disassemble the battery in the MBRAUN glove box of PRS340 / 11 - 119 - 11, take out the positive electrode plate, and assemble a CR2430 - type half coin - type battery of the positive - lithium piece. The area of the positive electrode plate adopted is, amm 2 whereas, as the electrolyte, a solution with 1M LiPF6 added to EC / EMC / DEC = 3 / 5 / 2 is adopted, and the assembled half coin - type battery is left standing for 3 h. The test is carried out at 25°C. First, charge at 0.1C in the voltage range of 2.5 - eV to desorb lithium, where e is the upper - limit operating voltage according to the cell design. Then, discharge at 0.05C until 2.5V to intercalate lithium. Perform 2 cycles. Denote the discharge coin - cell capacity of the second cycle as Y mAh. If the length of the positive electrode plate in the actual battery design is b mm, the width is c mm, and the number of coated surfaces of the positive electrode active material on the positive electrode current collector is d, then the positive - electrode lithium - desorption capacity = Y / a * b * c * d. In some embodiments, the lithium - desorbable capacity of the positive electrode is 2000 - 300000 mAh, optionally 3000 - 150000 mAh, and further optionally 3000 - 5000 mAh.

[0035] In this application, the term "lithium - intercalatable capacity of the negative electrode" means the actual lithium - intercalatable capacity of the negative electrode material in a battery. The test method is as follows. Disassemble the battery in the MBRAUN glove box of PRS340 / 11 - 119 - 11, take out the negative electrode plate, and assemble a CR2430 - type half coin - type battery of the negative - lithium piece. The area of the negative electrode plate adopted is, fmm 2The electrolyte used was a solution with EC / EMC / DEC = 3 / 5 / 2 and 1M of LiPF6 added. The assembled half-coin cell was then left to stand for 3 hours. The test was conducted at 25°C. First, 0.1C was used to discharge the battery in the voltage range of 2V-0V to absorb lithium. Then, 0.05C was used to charge the battery until it reached 2V to desorb lithium. Two cycles were performed, and the discharge capacity of the coin cell in the second cycle was denoted as ZmAh. If the negative electrode plate length in the actual battery design is hmm, the width is imm, and the number of coated surfaces of the negative electrode active material on the negative electrode current collector is d, then the lithium absorption capacity of the negative electrode is Z / f*h*i*d. In some embodiments, the lithium storage capacity of the negative electrode is 2100-315000mAh, optionally 3000-100000mAh, and optionally 3500-4500mAh.

[0036] In some embodiments, during the charging process of the battery from 0% to 70% state of charge (0-70%SOC) at 35°C, a current of four times or more the positive electrode's absorbable / desorbable capacity per unit time exists, optionally being five times or more the positive electrode's absorbable / desorbable capacity per unit time, and optionally being four to six-five times the positive electrode's absorbable / desorbable capacity per unit time. This ensures further improvement in the battery's high-rate rapid charging capability and cycle performance. In these embodiments, the current is an instantaneous current.

[0037] In this application, the "lithium desorbable capacity of the positive electrode per unit time" is defined as the amount of lithium desorbed from the positive electrode per unit time (1h), and the average current generated in this process is used as the basis for current quantization in this application. This allows for a correlation between the lithium desorbable capacity of the positive electrode and the current.

[0038] In some embodiments, during the charging process from 0% to 70% charge at 35°C, a method of direct charging with a constant current may generally be adopted. For example, a method of charging in stages may be adopted, where a current four times the positive electrode's absorbable / desorbable capacity per unit time is used to charge from 0% to 70% charge. For example, for 0-10% SOC, a current A times the positive electrode's absorbable / desorbable capacity per unit time is used, for 10-20% SOC, a current B times the positive electrode's absorbable / desorbable capacity per unit time is used, and for 20-30%... The SOC is set using a current that is C times the positive electrode's absorbable / desorbable capacity per unit time; 30-40% SOC uses a current that is D times the positive electrode's absorbable / desorbable capacity per unit time; 40-50% SOC uses a current that is E times the positive electrode's absorbable / desorbable capacity per unit time; 50-60% SOC uses a current that is F times the positive electrode's absorbable / desorbable capacity per unit time; 60-70% SOC uses a current that is G times the positive electrode's absorbable / desorbable capacity per unit time, and so on, where at least one of A, B, C, D, E, and F is not 4. As those skilled in the art will understand, in a stepwise charging method, the magnitudes of the stepwise SOC and current may be adjusted as needed.

[0039] For a packaged battery, the positive electrode lithium desorption capacity detection method is used to test the lithium desorption capacity of the positive electrode. The battery is then charged for two cycles using the above charging mode, and after disassembly, the positive electrode plate is removed. The positive electrode lithium desorption capacity detection method is used to test the lithium desorption capacity Z of the positive electrode at this time. If Z / X ≥ 40%, it is considered to meet the requirement of a charging rate that satisfies four times the positive electrode's absorbable / desorbable capacity per unit time.

[0040] In some embodiments, the average current during the charging process of the battery from 0% to 70% charge at 35°C (0-70% SOC) is more than four times the positive electrode's absorbable / desorbable capacity per unit time. This ensures further improvements in the battery's high-rate rapid charging capability and cycle performance.

[0041] In one embodiment, the test method for the average current of the 0-70% SOC is as follows: When a method of direct charging with a constant current is adopted, the average current is the charging current; when the stepwise charging method described above is adopted, the average current is (A+B+C+D+E+F+G) / 7.

[0042] In some embodiments, the negative electrode includes a current collector and a negative electrode active material layer attached to at least one surface of the current collector, negative electrode The active material layer includes a first active material layer containing a first negative electrode active material, and a second active material layer containing a second negative electrode active material, which is attached to the surface of the first active material layer away from the current collector.

[0043] In some embodiments, the average volume particle size D of the first negative electrode active material v50 This is the average volume particle size D of the second negative electrode active material. v50 It is larger than that.

[0044] In some embodiments, the average volume particle size D of the first negative electrode active material is measured based on particle size distribution laser diffraction (see GB / T19077.1-2009 for specifics). v50 The average volume particle size D of the second negative electrode active material is 10-20 μm. v50 The size is 9-19 μm.

[0045] In some embodiments, the first The activity The compaction density of the material layer is second The activity It is greater than the compaction density of the material layer.

[0046] In some embodiments, the first The activity The compaction density of the material layer is 1.3-2 g / cm³. 3 And the second The activity The compaction density of the material layer is 1.2–1.9 g / cm³. 3 The mass of the negative electrode material layer is weighed using a standard balance, and the coating area of ​​the negative electrode plate is measured using a straight ruler. The unit area mass of the negative electrode material layer, i.e., the coating surface density CW (mg / cm³), is then calculated. 2The following can be calculated: The thickness of the negative electrode material layer is measured by scanning electron microscopy ion polishing cross-sectional morphological analysis (see JY / T010-1996 for details) (measurements are taken at least 5 locations and the average value is taken), and the compaction density of the coating film = coating surface density of the negative electrode plate CW (mg / cm³) can be calculated. 2 Based on the thickness (cm) of the negative electrode material layer, the compaction density PD (unit: mg / cm³) of the negative electrode material layer is calculated. 3 ) calculate, and further g / cm³ 3 Convert to [the appropriate value].

[0047] In some embodiments, measurements are taken based on ion polishing cross-sectional morphological analysis using scanning electron microscopy (see JY / T010-1996) (at least 5 locations are measured and the average value is taken), and the first The activity The thickness of the material layer is 10-120 μm, and the second The activity The thickness of the material layer is 10-120 μm.

[0048] In some embodiments, the thickness of the negative electrode active material layer is 30-150 μm, the porosity is 20-60%, optionally 25-40%, and optionally 27-33%, and the compaction density is 1.2-1.9 g / cm³. 3 Therefore, it can be optionally 1.3-1.8 g / cm³. 3 That is the case.

[0049] In some embodiments, the electrolyte comprises a lithium salt, a solvent, and an additive, wherein the lithium salt comprises a main lithium salt and a secondary lithium salt.

[0050] In some embodiments, the main lithium salt and the secondary lithium salt are different, and each is independently selected from at least one of LiPF6, LiN(SO2F)2(LiFSI), LiBF4, LiN(CF3SO2)2(LiTFSI), LiClO4, LiAsF6, LiB(C2O4)2(LiBOB), LiBF2C2O4(LiDFOB), lithium difluorobis(oxalato)phosphate (LiDFOP), LiPO2F2, LiFSO3, and LiF. The difference between the main lithium salt and the secondary lithium salt is that their content differs.

[0051] In some preferred embodiments, the main lithium salt is lithium hexafluorophosphate or LiFSI or a mixture thereof, and its content is 8-20 wt%, optionally 10-15 wt%, based on the total weight of the electrolyte, and the secondary lithium salt is at least one of lithium difluoro(oxalato)borate LiBF2C2O4 (LiDFOB), LiBF4, LiB(C2O4)2 (LiBOB), or lithium difluorobis(oxalato)phosphate (LiDFOP), optionally LiDFOB or LiDFOP, and its content is 0.001 wt%-2 wt%, for example 1-2 wt%, optionally 0.8-1.5 wt%, based on the total weight of the electrolyte.

[0052] In some preferred embodiments, the molar concentration b of the lithium salt in the electrolyte is 0.6–1.5 mol / L, and optionally 0.8–1.2 mol / L.

[0053] In some embodiments, the solvent comprises a cyclic ester and a linear ester, wherein the cyclic ester content is 5-40% of the solvent mass, optionally 25-35%, and the linear ester content is 60-95% of the solvent mass, optionally 65-80%.

[0054] In some embodiments, the cyclic ester is ethylene carbonate (EC), propylene carbonate (PC), or a combination thereof, and the linear ester includes dimethyl carbonate (DMC).

[0055] In some embodiments, the linear ester may further contain, in addition to DMC, at least one component selected from diethyl carbonate (DEC), ethyl methyl carbonate (EMC), methyl formate, methyl acetate (MA), ethyl acetate (EA), butyl acetate, acetonitrile (SN), methyl propionate, ethyl propionate (EP), methyl butyrate, ethyl butyrate, propyl butyrate, butyl butyrate, isopropyl acetate, isoamyl acetate, and combinations thereof, optionally diethyl carbonate (DEC), ethyl acetate (EA), methyl acetate (MA), acetonitrile (SN), ethyl propionate (EP), and combinations thereof.

[0056] In one preferred embodiment, the cyclic ester is ethylene carbonate (EC), and the linear ester comprises dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC).

[0057] In some embodiments, the molar concentration b (mol / L) of the lithium salt in the electrolyte, the percentage a% of the linear ester relative to the solvent mass in the solvent, and the viscosity c of the electrolyte at 25°C satisfy the following relationship, i.e., 2 ≤ c + 2*a % ≤ 8, and optionally 3 ≤ c + 2*a % ≤ 7. 2 ≤ c + b ≤ 8, and optionally 3 ≤ c + b ≤ 7.

[0058] In some embodiments, the positive electrode includes a current collector and a positive electrode active material layer comprising a positive electrode active material attached to at least one surface of the current collector, wherein the positive electrode active material has the formula LiNi x Co y Q z M 1-x-y-zThe material contains a ternary material O2, where Q is Mn or Al, and M contains at least one of Co, Ni, Mn, Mg, Cu, Zn, Al, Sn, B, Ga, Cr, Sr, V, and Ti, and 0 ≤ x < 1, optionally 0.5 ≤ x < 1, 0 ≤ y ≤ 1, 0 ≤ z ≤ 1, and x + y + z ≤ 1.

[0059] The lithium-ion battery and power consumption device of this application will be described below with due reference to the drawings.

[0060] Generally, a lithium-ion battery includes a positive electrode, a negative electrode, an electrolyte, and a separator. During charging and discharging of the battery, active lithium ions intercept and deintercept by moving back and forth between the positive and negative electrodes. The electrolyte acts as a conductor of ions between the positive and negative electrodes. The separator is placed between the positive and negative electrodes and primarily serves to prevent short circuits between the electrodes while also allowing lithium ions to pass through.

[0061] positive electrode The positive electrode includes a positive electrode current collector and a positive electrode film layer placed on at least one surface of the positive electrode current collector, the positive electrode film layer including a positive electrode active material. The positive electrode active material has the formula LiNi x Co y Q z M 1-x-y-z The material comprises a ternary material O2, where Q is Mn or Al, and M comprises at least one of Co, Ni, Mn, Mg, Cu, Zn, Al, Sn, B, Ga, Cr, Sr, V, and Ti, and 0 ≤ x < 1, optionally 0.5 ≤ x < 1, 0 ≤ y ≤ 1, 0 ≤ z ≤ 1, and x + y + z ≤ 1.

[0062] For example, a positive electrode current collector has two opposing surfaces in its own thickness direction, and the positive electrode film layer is placed on one or both of the two opposing surfaces of the positive electrode current collector.

[0063] In some embodiments, the positive electrode current collector may be a metal foil sheet or a composite current collector. For example, aluminum foil may be used as the metal foil sheet. The composite current collector may include a polymer material substrate and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector may be formed by forming a metal material on a polymer material substrate. Here, the metal material includes, but is not limited to, aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. The polymer material substrate includes, but is not limited to, substrates such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0064] In some embodiments, the positive electrode active material is lithium nickel cobalt oxide, lithium nickel cobalt manganese oxide (LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2(NCM 333 (This can be abbreviated as LiNi) 0.5 Co 0.2 Mn 0.3 O2(NCM 523 (This can be abbreviated as LiNi) 0.5 Co 0.25 Mn 0.25 O2(NCM 211 (This can be abbreviated as LiNi) 0.6 Co 0.2 Mn 0.2 O2(NCM 622 (This can be abbreviated as LiNi) 0.65 Co 0.07 Mn 0.28 O2, LiLiLi 0.8 Co 0.1 Mn 0.1 O2(NCM 811 (This may be abbreviated as LiNi)), lithium nickel cobalt aluminum oxide (for example, LiNi 0.85 Co 0.15 Al 0.05 O2), LiNi 1 / 3 Co 1 / 3 Al 1 / 3It may be at least one of O2 or a modified compound thereof, preferably NCM. 622 However, this application is not limited to these materials, and other conventional materials that can be used as positive electrode active materials for batteries may also be used. These positive electrode active materials may be used individually or in combination of two or more.

[0065] In some embodiments, the positive electrode active material may further include other positive electrode active materials for batteries that are well known in the art. For example, the other positive electrode active material may include at least one of the following materials: olivine-structured lithium-containing phosphates, lithium cobalt oxide (e.g., LiCoO2), lithium nickel oxide (e.g., LiNiO2), lithium manganese oxide (e.g., LiMnO2, LiMn2O4), lithium manganese cobalt oxide, lithium nickel manganese oxide and its modified compounds. Examples of olivine-structured lithium-containing phosphates may include, but are not limited to, at least one of lithium iron phosphate (e.g., LiFePO4 (which may be abbreviated as LFP)), lithium iron phosphate-carbon composites, lithium manganese phosphate (e.g., LiMnPO4), lithium manganese phosphate-carbon composites, lithium manganese iron phosphate, and lithium manganese iron phosphate-carbon composites.

[0066] In some embodiments, based on the total weight of the positive electrode film layer, the weight ratio of the positive electrode active material in the positive electrode film layer is 80-100% by weight.

[0067] In some embodiments, the positive electrode film layer optionally further comprises an adhesive. For example, the adhesive may comprise at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorine-containing acrylate resin. Based on the total weight of the positive electrode film layer, the weight ratio of the adhesive to the positive electrode film layer is 0-20% by weight.

[0068] In some embodiments, the cathode film layer optionally further comprises a conductive agent. For example, the conductive agent may include at least one of superconducting carbon, carbon black (e.g., acetylene black, Ketjen black), carbon dots, carbon nanotubes, graphene, and carbon nanofibers. Based on the total weight of the cathode film layer, the weight ratio of the conductive agent in the cathode film layer is 0-20% by weight.

[0069] In some embodiments, the positive electrode plate may be manufactured by the following method: The above components for manufacturing the positive electrode plate, such as a positive electrode active material, a conductive agent, an adhesive, and any other components, are dispersed in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry, wherein the solid content of the positive electrode slurry is 40-80 wt%, and the viscosity at room temperature is adjusted to 5000-25000 mPa·s; the positive electrode slurry is coated onto the surface of the positive electrode current collector, dried, and then cold-pressed using a cold rolling mill to form the positive electrode plate, wherein the unit surface density of the positive electrode powder coating is 12-26 mg / cm³. 2 Therefore, the compaction density of the positive electrode plate is 2.0-3.6 g / cm³. 3 Therefore, it can be optionally 2.3-3.5 g / cm³. 3 The formula for calculating the consolidated density is as follows: Consolidation density = Coating surface density / (Thickness of electrode plate after pressing - Thickness of current collector)

[0070] negative electrode The negative electrode comprises a negative electrode current collector and a negative electrode film layer (also called a negative electrode active material layer) placed on at least one surface of the negative electrode current collector, wherein the negative electrode film layer comprises a negative electrode active material. The negative electrode includes the technical features relating to the negative electrode described above in this application.

[0071] For example, the negative electrode current collector has two opposing surfaces in its own thickness direction, and the negative electrode film layer is placed on one or both of the two opposing surfaces of the negative electrode current collector.

[0072] In some embodiments, the negative electrode current collector may be a metal foil sheet or a composite current collector. For example, copper foil may be used as the metal foil sheet. The composite current collector may include a polymer material substrate and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector may be formed by forming a metal material on the polymer material substrate. Here, the metal material includes, but is not limited to, copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys, and the polymer material substrate includes, but is not limited to, substrates such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0073] In some embodiments, the negative electrode active material may be a negative electrode active material for batteries that is well known in the art. For example, the negative electrode active material may include at least one of materials such as artificial graphite, natural graphite, soft carbon, hard carbon, silicone-based materials, tin-based materials, and lithium titanate. The silicone-based material may be selected from at least one of elemental silicone, silicon oxide, silicone-carbon composites, silicone-nitrogen composites, and silicone alloys. The tin-based material may be selected from at least one of elemental tin, tin oxides, and tin alloys. However, this application is not limited to these materials, and other conventional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used individually or in combination of two or more.

[0074] In some embodiments, the negative electrode active material is natural graphite, artificial graphite, mesocarbon microbeads (abbreviated as MCMB), hard carbon, soft carbon, silicon, silicon-carbon composite, silicon-oxygen composite, Li-Sn alloy, Li-Sn-O alloy, Sn, SnO, SnO2, or lithium-ionized TiO2-Li4Ti5O with a spinel structure. 12 , including one or more Li-Al alloys.

[0075] In some embodiments, the negative electrode includes a current collector and a negative electrode active material layer attached to at least one surface of the current collector, negative electrode The active material layer includes a first active material layer containing a first negative electrode active material, and a second active material layer containing a second negative electrode active material, which is attached to the surface of the first active material layer away from the current collector.

[0076] In some embodiments, the first negative electrode active material is natural graphite, artificial graphite, mesocarbon microbeads (abbreviated as MCMB), hard carbon, soft carbon, silicon, silicon-carbon composite, silicon-oxygen composite, Li-Sn alloy, Li-Sn-O alloy, Sn, SnO, SnO2, or lithium-ionized TiO2-Li4Ti5O with a spinel structure. 12 The second negative electrode active material is at least one of the following: natural graphite, artificial graphite, mesocarbon microbeads (abbreviated as MCMB), hard carbon, soft carbon, silicon, silicon-carbon composite, silicon-oxygen composite, Li-Sn alloy, Li-Sn-O alloy, Sn, SnO, SnO2, lithium-ionized TiO2-Li4Ti5O with a spinel structure. 12 It is at least one of the Li-Al alloys.

[0077] In some embodiments, when the negative electrode active material includes two types and a mixture of two or more types, the average volume particle size of the negative electrode active material is the average volume particle size of the mixture.

[0078] In some embodiments, the negative electrode active material includes silicon. The silicon content accounts for 1-25% of the weight of the negative electrode active material layer and is distributed in at least one layer of the active material layer.

[0079] In some embodiments, the silicon content (as SiO2) in the first active material layer is 0-25% based on the weight of the first active material layer, and the silicon content (as SiO2) in the second active material layer is 0-25% based on the weight of the second active material layer.

[0080] In some embodiments, the weight ratio of the negative electrode active material in the negative electrode film layer is 70-100% by weight, based on the total weight of the negative electrode film layer.

[0081] In some embodiments, the negative electrode film layer optionally further comprises an adhesive. The adhesive may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS). Based on the total weight of the negative electrode film layer, the weight ratio of the adhesive to the negative electrode film layer is 0-30% by weight.

[0082] In some embodiments, the negative electrode film layer optionally further comprises a conductive agent. The conductive agent may be selected from at least one of superconducting carbon, carbon black (e.g., acetylene black, Ketjen black), carbon dots, carbon nanotubes, graphene, and carbon nanofibers. Based on the total weight of the negative electrode film layer, the weight ratio of the conductive agent in the negative electrode film layer is 0-20% by weight.

[0083] In some embodiments, the negative electrode film layer optionally further comprises other additives, such as thickeners (e.g., sodium carboxymethylcellulose (CMC-Na)). Based on the total weight of the negative electrode film layer, the weight ratio of the other additives in the negative electrode film layer is 0-15% by weight.

[0084] In some embodiments, the negative electrode plate may be manufactured by the following method: The above components for manufacturing the negative electrode plate, such as a negative electrode active material, a conductive agent, an adhesive, and any other components, are dispersed in a solvent (e.g., deionized water) to form a negative electrode slurry, the solid content of the negative electrode slurry is adjusted to 30-70 wt%, and the viscosity at room temperature is adjusted to 2000-10000 mPa·s, the obtained negative electrode slurry is coated onto a negative electrode current collector, and after a drying process, the negative electrode plate is obtained by cold pressing, for example, by rolling. The unit surface density of the negative electrode powder coating is 6-16 mg / cm³. 2 Therefore, the compaction density of the negative electrode plate is 1.2-2.0 g / m³. 3 That is the case.

[0085] The porosity of the negative electrode active material layer can be obtained by the gas displacement method, and the porosity P = (V1 - V2) / V1 × 100%, where V1 represents the apparent volume of the negative electrode film and V2 represents the actual volume of the negative electrode film.

[0086] The mass of the negative electrode active material per unit area of ​​the negative electrode can be obtained by weighing it using a standard balance.

[0087] The thickness of the negative electrode active material layer can be obtained by measuring with a micrometer, for example, using a micrometer with part number Mitutoyo293-100 and an accuracy of 0.1 μm. It should be noted that the thickness of the negative electrode active material layer described in this invention refers to the thickness of the negative electrode active material layer in the negative electrode plate for battery assembly after compaction by cold pressing.

[0088] electrolyte The electrolyte plays a role in conducting ions between the positive and negative electrodes.

[0089] The aforementioned electrolyte includes the technical features described above in this application.

[0090] In some embodiments, the electrolyte comprises a lithium salt, a solvent, and an additive, wherein the lithium salt comprises a main lithium salt and a secondary lithium salt.

[0091] In some embodiments, the main lithium salt and the secondary lithium salt are different, and the main lithium salt and the secondary lithium salt are each independently selected from one or more of the following: lithium hexafluorophosphate (LiPF6), lithium bis(fluorosulfonyl)imide (LiN(SO2F)2, LiFSI), lithium tetrafluoroborate (LiBF4), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium trifluoromethanesulfonate (LiTFS), lithium bis(oxalato)borate (LiB(C2O4)2, LiBOB), lithium difluoro(oxalato)borate (LiBF2C2O4, LiDFOB), lithium difluorophosphate (LiPO2F2), lithium difluorobis(oxalato)phosphate (LiDFOP), LiPO2F2, LiFSO3, LiF, and lithium tetrafluoro(oxalato)phosphate (LiTFOP).

[0092] In some embodiments, the main lithium salt and the secondary lithium salt are different, and each is independently selected from at least one of LiPF6, LiN(SO2F)2(LiFSI), LiBF4, LiN(CF3SO2)2(LiTFSI), LiClO4, LiAsF6, LiB(C2O4)2(LiBOB), LiBF2C2O4(LiDFOB), lithium difluorobis(oxalato)phosphate (LiDFOP), LiPO2F2, LiFSO3, and LiF. The difference between the main lithium salt and the secondary lithium salt is that their content differs.

[0093] In some preferred embodiments, the main lithium salt is lithium hexafluorophosphate or LiFSI, and its content is 8-20 wt% based on the total weight of the electrolyte, and the secondary lithium salt is at least one of lithium difluoro(oxalato)borate LiBF2C2O4 (LiDFOB), LiBF4, LiB(C2O4)2 (LiBOB), and lithium difluorobis(oxalato)phosphate (LiDFOP), optionally LiDFOB or LiDFOP, and its content is 0.001 wt%-2 wt% based on the total weight of the electrolyte.

[0094] In some preferred embodiments, the molar concentration b of the lithium salt in the electrolyte is 0.8–1.2 mol / L.

[0095] In some embodiments, the solvent comprises a cyclic ester and a linear ester, wherein the cyclic ester accounts for 5-40% of the solvent mass and the linear ester accounts for 60-95% of the solvent mass.

[0096] In some embodiments, the cyclic ester is ethylene carbonate (EC), propylene carbonate (PC), or a combination thereof, and the linear ester includes dimethyl carbonate (DMC).

[0097] In some embodiments, the linear ester may further contain, in addition to DMC, at least one component selected from diethyl carbonate (DEC), ethyl methyl carbonate (EMC), methyl formate, methyl acetate (MA), ethyl acetate (EA), butyl acetate, acetonitrile (SN), methyl propionate, ethyl propionate (EP), methyl butyrate, ethyl butyrate, propyl butyrate, butyl butyrate, isopropyl acetate, isoamyl acetate, and combinations thereof, optionally diethyl carbonate (DEC), ethyl acetate (EA), methyl acetate (MA), acetonitrile (SN), ethyl propionate (EP), and combinations thereof.

[0098] In one preferred embodiment, the cyclic ester is ethylene carbonate (EC), and the linear ester comprises dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC).

[0099] In some embodiments, the additive comprises a carbonate (e.g., fluoroethylene carbonate FEC), a sulfate ester (e.g., vinyl sulfate DTD), and a sulfonic acid ester (e.g., 1,3-propanesultone PS). The carbonate comprises at least one of fluoroethylene carbonate (FEC), vinylene carbonate (VC), 1,2-difluoroethylene carbonate, 1,1-difluoroethylene carbonate, 1,1,2-trifluoroethylene carbonate, 1,1,2,2-tetrafluoroethylene carbonate, 1-fluoro-2-methylethylene carbonate, 1-fluoro-1-methylethylene carbonate, 1,2-difluoro-1-methylethylene carbonate, 1,1,2-trifluoro-2-methylethylene carbonate, or trifluoromethylethylene carbonate. The aforementioned sulfate ester comprises at least one of vinyl sulfate (DTD), diethyl sulfate (DES), dimethyl sulfate (DMS), and 4,4-bis(1,3,2-dioxathiolane)-2,2,2,2-tetraoxide. The aforementioned sulfonic acid ester comprises at least one of 1,3-propanesultone (1,3-PS), propensultone (PES), 3-fluoro-1,3-propanesultone (FPS), and vinyl methanedisulfonate (MMDS). In some preferred embodiments, the additive comprises fluoroethylene carbonate (FEC), vinyl sulfate (DTD), and 1,3-propanesultone (1,3-PS).

[0100] In some preferred embodiments, the mass percentage of the additive content relative to the total mass of the electrolyte is 0-7%.

[0101] In some embodiments, the electrolyte optionally further comprises other additives. For example, the other additives may include a negative electrode film forming additive and a positive electrode film forming additive, and may further include additives that can improve some of the battery's performance, such as an additive that improves the battery's overcharge performance, or an additive that improves the battery's high-temperature or low-temperature performance.

[0102] Separator In some embodiments, the secondary battery further includes a separator. This application is not particularly limited to the type of separator, and any known porous separator having good chemical and mechanical stability may be selected.

[0103] In some embodiments, the material of the separator may be selected from at least one of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator may be a single-layer film or a multilayer composite film, and is not particularly limited. If the separator is a multilayer composite film, the materials of each layer may be the same or different, and is not particularly limited.

[0104] In some embodiments, the thickness of the separator is 4-40 μm, and optionally 12-20 μm.

[0105] In some embodiments, the positive electrode plate, the negative electrode plate, and the separator may be manufactured as an electrode assembly by a winding process or a lamination process.

[0106] In some embodiments, the secondary battery may include an outer casing. This casing may be used to package the electrode assembly and electrolyte.

[0107] In some embodiments, the casing of the secondary battery may be a rigid case, such as a rigid plastic case, an aluminum case, or a steel case. The casing of the secondary battery may also be a pouch, such as a bag-shaped pouch. The material of the pouch may be plastic, and examples of plastics include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0108] This application does not particularly limit the shape of the secondary battery, which may be cylindrical, rectangular, or any other shape. For example, Figure 1 shows a secondary battery 5 with a rectangular structure as an example.

[0109] In some embodiments, referring to Figure 2, the casing may include a case 51 and a cover plate 53. The case 51 may include a bottom plate and side plates connected to the bottom plate, and the bottom plate and side plates surround and form a housing cavity. The case 51 has an opening that communicates with the housing cavity, and the cover plate 53 can close the housing cavity by covering the opening. The positive electrode plate, the negative electrode plate and the separator can form an electrode assembly 52 by a winding process or a lamination process. The electrode assembly 52 is packaged within the housing cavity. The electrolyte permeates the electrode assembly 52. ​​The number of electrode assemblies 52 included in the secondary battery 5 may be one or more, and a person skilled in the art can select according to the actual specific requirements.

[0110] In some embodiments, the secondary batteries may be assembled into a battery module, and the number of secondary batteries included in the battery module may be one or more, the specific number which can be selected by those skilled in the art based on the application and capacity of the battery module.

[0111] In the battery module, the multiple secondary batteries 5 may be arranged sequentially along the longitudinal direction of the battery module. Of course, they may be arranged according to any other method. Furthermore, the multiple secondary batteries 5 may be secured with fasteners.

[0112] Optionally, the battery module may further include a housing having a housing space, in which a plurality of secondary batteries 5 are housed.

[0113] In some embodiments, the battery modules may be further assembled into a battery pack, the number of battery modules included in the battery pack may be one or more, and the specific number can be selected by those skilled in the art based on the application and capacity of the battery pack.

[0114] The battery pack may include a battery box and a plurality of battery modules installed in the battery box. The battery box includes an upper housing and a lower housing, the upper housing being provided to cover the lower housing and forming a sealed space for housing the battery modules. The plurality of battery modules may be arranged inside the battery box in any manner.

[0115] Furthermore, this application provides a power consumption device comprising at least one of a secondary battery, battery module, or battery pack according to this application. The secondary battery, battery module, or battery pack may be used as a power source for the power consumption device or as an energy storage unit for the power consumption device. The power consumption device may include, but is not limited to, mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.

[0116] As the power consumption device, a secondary battery, battery module, or battery pack can be selected according to the usage requirements.

[0117] Figure 3 shows an example of a power consumption device. This power consumption device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the power consumption device's demand for high power and high energy density of secondary batteries, a battery pack or battery module can be employed.

[0118] Other examples of such devices may include mobile phones, tablet computers, and laptop computers. These devices generally require lightweight designs and can utilize rechargeable batteries as their power source.

[0119] Examples To further clarify the technical problem, technical solution, and beneficial effects that this application aims to solve, the application will be described in more detail below, linking examples and drawings. It is clear that the described examples represent only a subset of, and not all, examples of, this application. The description of at least one exemplary example below is for illustrative purposes only and is not a limitation on this application or its applications. All other examples that can be obtained based on the examples of this application without creative effort by a person skilled in the art are all within the scope of protection of this application.

[0120] If specific techniques or conditions are not specified in the examples, the techniques or conditions described in the literature in the art, or in the product instruction manual, shall be followed. Unless the manufacturer is specified for the reagents or instruments used, they are all common products available commercially.

[0121] I. Examples Example 1 1. Manufacturing of electrolyte The electrolyte was prepared in a glove box under an argon gas atmosphere with a water content of <10 ppm. First, ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) were mixed in a mass ratio of 3:5:2. Then, 1 mol / L of the main lithium salt LiPF6, the secondary lithium salt LiBF4 + LiDFOB (which accounted for 1 wt% of the total electrolyte), and the additive FEC + DTD + 1,3-PS (which accounted for 4 wt% of the total electrolyte) were added and mixed uniformly to obtain the electrolyte. The viscosity of the electrolyte was 3.8 mPa.s.

[0122] 2. Manufacturing of the positive electrode plate Cathode active material ternary material LiNi 0.65 Co 0.07 Mn 0.28 O2, polyvinylidene fluoride (an adhesive), and acetylene black (a conductive agent) were mixed in a weight ratio of 98:1:1 and dissolved in the solvent N-methylpyrrolidone (NMP) to prepare a positive electrode slurry. The slurry was then applied to the aluminum foil of the current collector, dried, and then subjected to cold pressing, deburring, cutting, and slitting to produce a positive electrode plate with dimensions of 87*665mm.

[0123] 3. Manufacturing of the negative electrode plate The first negative electrode slurry is formed by dissolving graphite (the negative electrode active material), SiO2, styrene-butadiene rubber (the adhesive), and sodium carboxymethylcellulose (the dispersant) in deionized water in a weight ratio of 96.5:1.5:1:1. A 6 μm copper foil is used as the negative electrode current collector, and the first layer of negative electrode slurry is first coated onto the negative electrode current collector, with a coating weight of 4.25 mg / cm³. 2 This formed the first active material layer. After the first active material layer dried, the second negative electrode slurry was applied. The second negative electrode slurry was formed by dissolving graphite (negative electrode active material), SiO2, styrene-butadiene rubber (adhesive), and sodium carboxymethylcellulose (dispersant) in deionized water in a weight ratio of 96.5:1.5:1:1, and the coating weight of the second active material layer was 4.25 mg / cm². 2 This formed a second active material layer.

[0124] Furthermore, a composite negative electrode plate was obtained through drying, cold pressing, and cutting in sequence. After cold pressing, the thickness of the composite active material layer coated on one surface of the copper foil was 51 μm, and the compaction density of the active material layer was 1.65 g / cm³. 3 Therefore, a negative electrode plate with dimensions of 93*691mm was manufactured and prepared.

[0125] 4. Separator The separator substrate was made of polyethylene (PE) with a thickness of 8 μm. A 2 μm alumina ceramic layer was applied to each side of the separator substrate, and finally, 2.5 mg of polyvinylidene fluoride (PVDF) adhesive was applied to each side of the ceramic layer and dried.

[0126] 5. Battery assembly The positive electrode plate, separator, and negative electrode plate are sequentially wound or stacked, and the separator is positioned between the positive and negative electrode plates to obtain a bare cell. The bare cell is placed in an outer casing, 9.3 g of the manufactured electrolyte is injected into the dried cell, and after processes such as standing, chemical formation, and shaping, a lithium-ion secondary battery with a capacity of 3100 mAh is obtained.

[0127] The manufacturing steps for Example 2-26 and Comparative Example 1-3 are similar to those of Example 1, but the electrolyte or negative electrode material or composition is changed. See Table 1.

[0128] Parameter testing Porosity P% test of the negative electrode active material layer The porosity P% of the negative electrode active material layer may be measured as follows: Using an inert gas with a small molecular size, such as helium or nitrogen, the actual volume of the sample to be tested was accurately measured by the displacement method, and the porosity of the sample to be tested was obtained by applying Bohr's law (PV=nRT). The porosity P = (V11-V12) / V11 × 100%, where V11 represents the apparent volume of the negative electrode active material layer and V12 represents the actual volume of the negative electrode active material layer.

[0129] Electrolyte viscosity test At a constant temperature, when the rotor continues to rotate at a constant speed over the sample, the shear force it experiences generates torque in the spring. This torque is proportional to the viscosity, and thus the viscosity value can be obtained.

[0130] Specifically, a Brookfield (DV-2TLV) viscometer was used to test the viscosity of the finished electrolyte. The ambient temperature was controlled to 25°C and the ambient humidity to <80%. 30 mL of the electrolyte was taken and kept in a 25°C water bath at a constant temperature for at least 30 minutes. The rotor was placed in the sample cup, the sample was added to a level of approximately 0.3 cm from the top of the cup, the connected viscometer was started, and a rotation speed of 70 RPM was selected to perform the test. Ten data points were collected, and the average value of these points was calculated.

[0131] [Table 1] JPEG0007879951000002.jpg254146JPEG0007879951000003.jpg253146

[0132] 2. Battery performance test 1. Desorbable lithium capacity of the positive electrode Disassemble the battery inside the MBRAUN glove box of PRS340 / 11-119-11, remove the positive electrode plate, and assemble a CR2430 type half-coin cell battery with a lithium positive electrode plate. The area of ​​the positive electrode plate used is amm 2Here, a solution with EC / EMC / DEC = 3 / 5 / 2 and 1M of LiPF6 added was used as the electrolyte, and the assembled half-coin cell was left standing for 3 hours. The test was performed at 25°C. First, 0.1C was used to charge the cell in a voltage range of 2.5-eV to desorb lithium, where e is the upper limit operating voltage according to the cell design. Then, 0.05C was used to discharge the cell until it reached 2.5V to absorb lithium. Two cycles were performed, and the discharge capacity of the coin cell in the second cycle was denoted as Y mAh. If the positive electrode film length of the actual battery design is b mm, the width is cm mm, and the number of coated surfaces of the positive electrode active material on the positive electrode current collector is d, then the positive electrode lithium desorption capacity is X = Y / a * b * c * d.

[0133] 2. Lithium storage capacity of the negative electrode Disassemble the battery inside the glove compartment of the PRS340 / 11-119-11MBRAUN, remove the negative electrode plate, and assemble a CR2430 type half-coin cell battery with a lithium negative electrode plate. The area of ​​the negative electrode plate used is fmm. 2 Here, a solution with EC / EMC / DEC = 3 / 5 / 2 and 1M of LiPF6 added is used as the electrolyte, and the assembled half-coin cell is left to stand for 3 hours. The test is performed at 25°C, first discharging at 0.1C in the voltage range of 2V-0V to absorb lithium, and then charging at 0.05C until 2V to desorb lithium, and two cycles are performed. The discharge capacity of the coin cell in the second cycle is denoted as ZmAh, and if the negative electrode film length of the actual battery design is hmm, the width is imm, and the number of coated surfaces of the negative electrode active material on the negative electrode current collector is d, then the lithium absorption capacity of the negative electrode = Z / f*h*i*d.

[0134] 3. Charging capacity test Rate performance test (test to charge to 70% SOC): The test temperature was adjusted to 35°C, and lithium-ion batteries were charged at xC rates (x being 0.5, 0.8, 1, 1.2, 1.5, 2, 2.5, and 3), then discharged at 1C. The charge rate was progressively increased, and the charging stopped when the anode potential reached 0V. The maximum achievable charge rate within the 0-10% SOC, 10-20% SOC, 20-30% SOC, 30-40% SOC, 40-50% SOC, 50-60% SOC, and 60-70% SOC intervals was obtained, and the charging time (minutes) required to reach 0-70% SOC was calculated.

[0135] 4. Cycle performance test At 25°C, the secondary battery was charged with a constant current of 1C to 4.3V, and then charged with a constant voltage until the current reached 0.05C. At this point, the secondary battery was fully charged, and the charge capacity at this time was recorded as the first charge capacity. After letting the secondary battery stand for 5 minutes, it was discharged with a constant current of 1C to 2.8V. This constituted one charge-discharge cycle, and the discharge capacity at this time was recorded as the first discharge capacity. The secondary battery was subjected to a cycle charge-discharge test using the above method, and the discharge capacity after each cycle was recorded. The capacity retention rate (%) of the secondary battery after 600 cycles at 45°C is calculated as: discharge capacity after 600 cycles / first discharge capacity × 100%.

[0136] III. Test Results of Each Example and Comparative Example Batteries for each example and comparative example were manufactured according to the method described above, and each performance parameter was measured. The results are shown in Table 2 below.

[0137] [Table 2]

[0138] As can be seen from the above examples and comparative examples, the lithium-ion battery of this application has good rapid charging capability and capacity retention rate when the electrolyte viscosity is in the range of 1-6 mPa.s, the CB value is 1.1-1.5, and consequently the porosity of the negative electrode active material is in the range of 25-40%. For example, the charging time required to reach 0-80% SOC can be reduced to 6 minutes, and the capacity retention rate after 600 cycles is still maintained at 95% or more (see Example 12).

[0139] It should be noted that this application is not limited to the embodiments described above. The embodiments described above are illustrative, and any embodiment that has substantially the same configuration as the technical idea and produces the same effects within the scope of the technical proposal of this application is included within the scope of the technical proposal of this application. Furthermore, other forms constructed by combining some of the components of the embodiments, with various modifications that a person skilled in the art could conceive of, are also included within the scope of this application, as long as they do not depart from the spirit of this application. [Explanation of symbols]

[0140] 5: Secondary battery 51: Case 52: Electrode Assembly 53: Cover plate 6:Power consumption device

Claims

1. A lithium-ion battery comprising a positive electrode, a negative electrode, and an electrolyte, The viscosity c of the electrolyte at 25°C is 1-6 mPa·s, and the ratio CB of the lithium storage capacity of the negative electrode to the lithium desorption capacity of the positive electrode is 1.05-1.

5. The negative electrode includes a current collector and a negative electrode active material layer attached to at least one surface of the current collector. The negative electrode active material layer includes a first active material layer containing a first negative electrode active material, and a second active material layer containing a second negative electrode active material, which is attached to the surface of the first active material layer away from the current collector. The electrolyte comprises a lithium salt, a solvent, and an additive. The lithium salt comprises a main lithium salt and a secondary lithium salt. A lithium-ion battery that differs from the aforementioned main lithium salt and secondary lithium salt.

2. The lithium-ion battery according to claim 1, characterized in that, during the process of charging the lithium-ion battery from a 0% charge state to a 70% charge state at 35°C, there exists a current with a positive electrode storage / desorption capacity of four times or more per unit time.

3. The lithium-ion battery according to claim 1, characterized in that the average current during the process of charging the lithium-ion battery from a 0% charge state to a 70% charge state at 35°C is four times or more the positive electrode storage and desorption capacity per unit time.

4. The average volume particle size D of the first negative electrode active material ｖ５０ This is the average volume particle size D of the second negative electrode active material. ｖ５０ A lithium-ion battery according to claim 1, characterized in that it is larger than [the specified size].

5. The lithium-ion battery according to claim 1, characterized in that the compaction density of the first active material layer is greater than the compaction density of the second active material layer.

6. The thickness of the negative electrode active material layer, which includes the first active material layer and the second active material layer, is 30–150 μm, the porosity is 20–60%, and the compaction density is 1.2–1.9 g / cm³. ３ The lithium-ion battery according to claim 1, characterized in that it is the same as described in claim 1.

7. The main lithium salt and the sub-lithium salt are each independently LiPF ６ , LiN(SO ２ F) ２ , LiBF ４ , LiN(CF ３ SO ２ ), ２ , LiClO ４ , LiAsF ６ , LiB(C ２ O ４ ), ２ , LiBF ２ C ２ O ４ , LiDFOP, LiPO ２ F ２ , LiFSO ３ , LiF, and are selected from at least one of them. The lithium ion battery according to claim 1, characterized in that.

8. The main lithium salt is lithium hexafluorophosphate or LiFSI, and its content is 8-20 wt% based on the total weight of the electrolyte, and the secondary lithium salt is lithium difluoro(oxalato)borate, LiBF ４ LiB(C) ２ O ４ ) ２ The lithium-ion battery according to claim 1, characterized in that it is at least one of the following: difluorobis(oxalato) lithium phosphate (LiDFOP), and its content is 0.001 wt% to 2 wt% based on the total weight of the electrolyte.

9. The lithium-ion battery according to claim 1, wherein the solvent comprises a cyclic ester and a linear ester, the cyclic ester content accounting for 5-40% of the solvent mass, and the linear ester content accounting for 60-95% of the solvent mass.

10. The lithium-ion battery according to claim 9, characterized in that the cyclic ester is ethylene carbonate, propylene carbonate, or a combination thereof, and the linear ester contains dimethyl carbonate.

11. The lithium-ion battery according to claim 10, characterized in that the linear ester is selected from diethyl carbonate, ethyl methyl carbonate, methyl formate, methyl acetate, ethyl acetate, butyl acetate, methyl propionate, methyl butyrate, ethyl butyrate, propyl butyrate, butyl butyrate, isopropyl acetate, isoamyl acetate, and combinations thereof.

12. In the aforementioned electrolyte, the molar concentration b (mol / L) of the lithium salt, the percentage a% of the linear ester relative to the solvent mass in the solvent, and the viscosity c of the electrolyte at 25°C satisfy the following relationship, i.e., 2 ≤ c + 2 * a % ≤ 8, The lithium-ion battery according to claim 1, characterized in that 2 ≤ c + b ≤ 8.

13. The positive electrode comprises a current collector and a positive electrode active material layer containing a positive electrode active material attached to at least one surface of the current collector, wherein the positive electrode active material has the formula LiNi ｘ Co ｙ Q ｚ M １－ｘ－ｙ－ｚ O ２ A lithium-ion battery according to any one of claims 1 to 3, comprising a ternary material wherein Q is Mn or Al, and M comprises at least one of Co, Ni, Mn, Mg, Cu, Zn, Al, Sn, B, Ga, Cr, Sr, V, and Ti, and wherein 0 ≤ x < 1, 0 ≤ y ≤ 1, 0 ≤ z ≤ 1, and x + y + z ≤ 1.

14. A power consumption device characterized by including a lithium-ion battery according to any one of claims 1 to 3.

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