Lithium-ion batteries and power-consuming 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 in particular to lithium ion batteries and power consuming devices. [Background technology]

[0002] In recent years, as the application range of lithium ion batteries becomes wider and wider, lithium ion batteries are widely used in energy storage power systems such as hydroelectric, thermal, wind and solar power stations, as well as in many fields such as electric tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace, etc. However, compared with conventional fuel oil-driven devices, problems such as range anxiety and long charging time have become major problems that hinder the development of secondary batteries, and how to improve the rapid charging ability of secondary batteries is one of the focal issues of interest to those skilled in the art.

[0003] Improving the fast charging capability of batteries is a system engineering effort that requires changes and upgrades to battery materials. In conventional technology, most research has been focused on improving the negative electrode material, but the formulation of materials such as electrolytes and conductive agents is also essential. Therefore, it is necessary to further improve conventional batteries with fast charging capabilities. Summary of the Invention

[0004] The present application has been made in view of the above problems, and an object of the present application is to provide a lithium ion battery having an improved electrolyte viscosity and CB value, which includes an electrolyte of a specific viscosity and has a ratio CB of the lithium absorbing capacity of the negative electrode to the lithium desorbing capacity of the positive electrode within a specific range, so that the corresponding battery has a high-rate fast charging capability and good cycle performance.

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

[0006] A first aspect of the present application provides a lithium-ion battery including a positive electrode, a negative electrode, and an electrolyte, wherein the electrolyte has a viscosity c of 1-6 mPa.s at 25° C., and a ratio CB of the lithium absorption 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 the present application includes an electrolyte having a specific viscosity and a ratio CB of the lithium absorption capacity of the negative electrode to the lithium desorption 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, thereby improving the high-rate fast charging ability and cycle performance of the battery.

[0008] In an optional embodiment, in the process of charging the battery from a charge state of 0% to a charge state of 70% at 35° C., there is a current of 4 times or more of the lithium desorbable capacity of the positive electrode per unit time, which ensures further improvement of the high-rate fast charging capability and cycle performance of the battery.

[0009] In an optional embodiment, the average current during charging the battery from a charge state of 0% to a charge state of 70% at 35° C. is at least four times the positive electrode occlusion / desorption capacity per unit time, thereby ensuring further improvement of the high-rate fast charging capability and cycle performance of the battery.

[0010] In an optional embodiment, the negative electrode includes a current collector and a negative electrode active material layer deposited on at least one surface of the current collector, the active material layer including a first active material layer including a first negative electrode active material and a second active material layer including a second negative electrode active material deposited on a surface of the first active material layer remote from the current collector, which can improve the high rate fast charge capability and cycling performance of the battery by providing even more active sites for lithium ion storage in the negative electrode.

[0011] In an optional embodiment, the first negative electrode active material has an average volume particle size D v50 is the average volume particle size D of the second negative electrode active materialv50 This can improve the high-rate fast charging capability and cycling performance of the battery by providing more and more active sites for lithium ion storage in the negative electrode.

[0012] In an optional embodiment, the first negative electrode active material layer has a greater packed density than the second negative electrode active material layer, which can improve the high-rate fast charge capability and cycle performance of the battery by providing more active sites for lithium ion storage in the negative electrode.

[0013] In an optional embodiment, the negative electrode active material layer has a thickness of 30-150 μm, a porosity of 20-60%, and a compaction density of 1.2-1.9 g / cm 3 This can improve the high-rate fast charging capability and cycling performance of the battery by providing more and more active sites for lithium ion storage in the negative electrode.

[0014] In an optional embodiment, the electrolyte solution includes a lithium salt, a solvent, and an additive, and the lithium salt includes a main lithium salt and a sub lithium salt, which can further improve the liquid phase transport conditions of lithium ions, thereby improving the high-rate fast charging capability and cycle performance of the battery.

[0015] In an optional embodiment, the primary and secondary lithium salts are different and each of the primary and secondary lithium salts is 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 O4 , LiDFOP, LiPO 2 F 2 , LiFSO 3 , LiF, thereby further improving the liquid phase transport conditions of lithium ions, thereby improving the high rate fast charging capability and cycle performance of the battery.

[0016] In an optional embodiment, the primary 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 , lithium difluorobis(oxalato)phosphate (LiDFOP), and its content is 0.001wt%-2wt% based on the total weight of the electrolyte, which can further improve the liquid phase transport conditions of lithium ions, thereby improving the high-rate fast charging ability and cycle performance of the battery.

[0017] In an optional embodiment, the solvent comprises a cyclic ester and a linear ester, the cyclic ester content being 5-40% by mass of the solvent, and the linear ester content being 60-95% by mass of the solvent, which can further improve the viscosity of the electrolyte, thereby improving the liquid phase transport conditions of lithium ions, and thereby improving the high-rate fast charging capability and cycle performance of the battery.

[0018] In an optional embodiment, the cyclic ester is ethylene carbonate, propylene carbonate, or a combination thereof, and the linear ester includes dimethyl carbonate, which can further improve the viscosity of the electrolyte, thereby improving the liquid phase transport conditions of lithium ions, thereby improving the high rate fast charging capability and cycle performance of the battery.

[0019] In an optional 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, which can further improve the viscosity of the electrolyte, thereby improving the liquid phase transport conditions of lithium ions, thereby improving the high rate fast charging capability and cycle performance of the battery.

[0020] In an optional embodiment, in the electrolyte solution, the molar concentration b (mol / L) of the lithium salt, the percentage a % of the linear ester in the solvent relative to the solvent mass, and the viscosity c of the electrolyte solution at 25° C. satisfy the following relationship: 2≦c+2*a%≦8, 2≦c+b≦8, which can further improve the viscosity of the electrolyte, thereby improving the liquid phase transport conditions of lithium ions, thereby improving the high-rate fast charging capability and cycle performance of the battery.

[0021] In an optional embodiment, the positive electrode comprises a current collector and an active positive electrode layer deposited on at least one surface of the current collector, the active positive electrode layer comprising an active positive electrode material having the formula LiNi x Co y Q z M 1-x-y-z O 2 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, and 0≦x<1, 0≦y≦1, 0≦z≦1, and x+y+z≦1, which further improves the high-rate fast charging capability and cycle performance of the battery.

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

[0023] The secondary battery of the present application includes an electrolyte having a specific viscosity and has a ratio CB of the lithium absorption capacity of the negative electrode to the lithium desorption capacity of the positive electrode within a specific range, thereby improving the liquid phase transport conditions of lithium ions, allowing the lithium ions to move quickly to the negative electrode, and providing more active sites for lithium ion absorption in the negative electrode, thereby improving the high-rate fast charging ability and cycle performance of the battery. [Brief description of the drawings]

[0024] [Figure 1] FIG. 1 is a schematic diagram of a secondary battery according to an embodiment of the present application. [Diagram 2] FIG. 2 is an exploded view of the secondary battery according to the embodiment of the present application shown in FIG. [Diagram 3] 1 is a schematic diagram of a power consuming device in which a secondary battery according to an embodiment of the present application is used as a power source; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0025] Hereinafter, with appropriate reference to the drawings, an embodiment specifically disclosing the lithium ion battery and the power consumption device of the present application will be described in detail. However, unnecessary detailed description may be omitted. For example, detailed description of well-known matters and duplicated description of structures that are actually the same may be omitted. This is to avoid the following description becoming unnecessarily long and to allow those skilled in the art to easily understand. Note that the drawings and the following description are provided to allow those skilled in the art to fully understand the present application, and are not intended to limit the subject matter described in the claims.

[0026] The "ranges" disclosed in this application are defined in the form of lower and upper limits, and a given range is defined by selecting one lower limit and one upper limit, and the selected lower and upper limits define the boundaries of the particular range. Such defined ranges may be inclusive or exclusive of the extreme values, and may be arbitrarily combined, i.e., any lower limit may be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a particular parameter, it is understood that ranges of 60-110 and 80-120 are also envisaged. However, if 1 and 2 are listed as minimum range values, and 3, 4, and 5 are listed as maximum range values, the ranges 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5 are all envisaged. In this application, unless otherwise specified, the numerical range "ab" represents a shorthand representation of any combination of real numbers from a to b, where a and b are both real numbers. For example, the numerical range "0-5" represents a list of all real numbers between "0-5" already listed in this specification, and "0-5" is just a shorthand for combinations of these numbers. Also, expressing a parameter as an integer ≧2 is equivalent to disclosing that the parameter is, for example, the integers 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc. Unless otherwise stated, all the embodiments and optional embodiments in the present application can be combined with each other to form a new technical solution.

[0027] Unless otherwise stated, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

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

[0029] Unless otherwise specified, the terms "comprise" and "include" referred to in this application may be open ended or closed ended. For example, the terms "comprise" and "include" may further include or include other ingredients not listed, or may include or include only the ingredients listed.

[0030] Unless otherwise stated, in this application, the term "or" is inclusive. For example, the phrase "A or B" means "A, B, or both A and B." More specifically, "A or B" is satisfied in the following cases: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) but B is true (or exists); and A and B are both true (or exist).

[0031] At present, compared with conventional fuel oil-powered devices, problems such as range anxiety and long charging time are the main problems that hinder the development of secondary batteries, and how to improve the fast charging ability of secondary batteries is one of the focal issues of interest to those skilled in the art. Improving the fast charging ability of a battery is a system engineering, and requires the change or upgrade of battery materials. In the prior art, the improvement of the negative electrode material has been most studied, but the blending of materials such as electrolyte and conductive agent is also essential. Therefore, it is necessary to further improve the conventional batteries with fast charging ability. The inventor has found through research that the lithium-ion battery of the first aspect of the present application has a high-rate fast charging ability and good cycle performance by containing an electrolyte with a specific viscosity and having a ratio CB of the lithium absorption capacity of the negative electrode and the lithium desorption capacity of the positive electrode within a specific range.

[0032] Lithium-ion battery In some embodiments, the present application provides a lithium-ion battery, the battery comprising: a positive electrode; a negative electrode; and an electrolyte; wherein the electrolyte has a viscosity c at 25° C. of 1-6 mPa.s, preferably 2-5 mPa.s, and optionally 3.5-4 mPa.s, measured according to GB / T10247-2008; and a 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, optionally 1.1-1.3, and optionally 1.1-1.2.

[0033] The lithium ion battery of the present application includes an electrolyte with a specific viscosity, and has a ratio CB of the lithium absorption capacity of the negative electrode to the lithium desorption capacity of the positive electrode within a specific range, thereby realizing good and rapid infiltration and suck-back of the positive and negative electrodes, improving the liquid phase transport conditions of lithium ions, and providing more active sites for lithium ion absorption in the negative electrode, thereby improving the high-rate fast charging ability and cycle performance of the battery.

[0034] In this application, the term "lithium release capacity of positive electrode" refers to the actual lithium release capacity of the positive electrode material in the battery. The test method is as follows: In a MBRAUN glove box of PRS340 / 11-119-11, the battery is disassembled, the positive plate is taken, and a positive electrode-lithium strip CR2430 type half coin battery is assembled. The area of ​​the positive plate used is amm 2 The electrolyte is LiPF with EC / EMC / DEC=3 / 5 / 2. 6 A solution containing 1M of ... In some embodiments, the lithium release 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 absorption capacity of the negative electrode" refers to the actual lithium absorption capacity of the negative electrode material in the battery. The test method is as follows: In a PRS340 / 11-119-11 MBRAUN glove box, the battery is disassembled, the negative plate is taken, and a negative electrode-lithium piece CR2430 type half coin battery is assembled. The area of ​​the negative plate used is fmm 2 The electrolyte is LiPF with EC / EMC / DEC=3 / 5 / 2. 6A solution containing 1M of 1M 100% ... In some embodiments, the lithium storage capacity of the negative electrode is 2100-315000 mAh, optionally 3000-100000 mAh, and further optionally 3500-4500 mAh.

[0036] In some embodiments, in the process of charging the battery from 0% SOC to 70% SOC (0-70% SOC) at 35° C., a current is 4 times or more the positive electrode occluding / desorbing capacity per unit time, optionally the current is 5 times or more the positive electrode occluding / desorbing capacity per unit time, and further optionally the current is 4 to 6.5 times the positive electrode occluding / desorbing capacity per unit time. This ensures further improvement of the high-rate fast charging capability and cycle performance of the battery. In the embodiment, the current is an instantaneous current.

[0037] In this application, the "lithium desorption capacity of the positive electrode per unit time" refers to the amount of lithium desorbed from the positive electrode per unit time (1 h), and the average current generated during this process is used as the basis for current quantization in this application. This allows the lithium desorption capacity of the positive electrode to be related to the current.

[0038] In some embodiments, in the process of charging from a charge state of 0% to a charge state of 70% at 35° C., a method of direct charging at a constant current may be generally adopted. For example, charging from a charge state of 0% to a charge state of 70% at a current four times the positive electrode occluding / desorbing capacity in a unit time may be adopted. A method of stepwise charging may also be adopted. For example, for 0-10% SOC, a current A times the positive electrode occluding / desorbing capacity in a unit time is adopted. For 10-20% SOC, a current B times the positive electrode occluding / desorbing capacity in a unit time is adopted. For 20-30% SOC, a current B times the positive electrode occluding / desorbing capacity in a unit time is adopted. SOC adopts a current C times the positive electrode occlusion / desorption capacity in unit time, 30-40% SOC adopts a current D times the positive electrode occlusion / desorption capacity in unit time, 40-50% SOC adopts a current E times the positive electrode occlusion / desorption capacity in unit time, 50-60% SOC adopts a current F times the positive electrode occlusion / desorption capacity in unit time, 60-70% SOC adopts a current G times the positive electrode occlusion / desorption capacity in unit time, etc., where at least one of A, B, C, D, E, and F is not 4. As can be understood by those skilled in the art, in the stepwise charging method, the stepwise SOC and current magnitude may be adjusted as necessary.

[0039] For the packaged battery, use the positive electrode lithium desorption capacity detection method to test the lithium desorption capacity of the positive electrode, and use the above charging mode to charge the battery for two cycles. Then disassemble the battery to take out the positive plate, and use the positive electrode lithium desorption capacity detection method to test the lithium desorption capacity Z of the positive electrode at this time. If Z / X is 40% or more, it is deemed to meet the requirement that the charge rate is four times the positive electrode occlusion / desorption capacity within a unit time.

[0040] In some embodiments, the average current during charging the battery from 0% SOC to 70% SOC (0-70% SOC) at 35° C. is 4 times or more the positive electrode occlusion / desorption capacity per unit time, thereby ensuring further improvement of the high-rate fast charging capability and cycle performance of the battery.

[0041] In one embodiment, the test method of the average current of the 0-70% SOC is as follows: when adopting the constant current direct charging mode, the average current is the charging current, and when adopting the above-mentioned stepwise charging mode, 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 deposited on at least one surface of the current collector, the active material layers including a first active material layer including a first negative electrode active material and a second active material layer including a second negative electrode active material deposited on a surface of the first active material layer remote from the current collector.

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

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

[0045] In some embodiments, the packed density of the first negative electrode active material layer is greater than the packed density of the second negative electrode active material layer.

[0046] In some embodiments, the first negative electrode active material layer has a packed density of 1.3-2 g / cm 3 and the compaction density of the second negative electrode active material layer is 1.2-1.9 g / cm 3 The mass of the negative electrode material layer was weighed using a standard balance, the coating area of ​​the negative electrode plate was measured using a straight edge, and the unit area mass of the negative electrode material layer, i.e., the coating surface density CW (mg / cm 2) can be calculated by measuring the thickness of the negative electrode material layer (at least five points are measured and the average value is taken) using ion-polished cross-sectional morphological analysis of the scanning electron microscope (see JY / T010-1996 for details), and calculating the coating density = coating surface density CW (mg / cm 2 ) / thickness (cm) of the negative electrode material layer, the compaction density PD (unit: mg / cm 3 ) and then g / cm 3 Convert to.

[0047] In some embodiments, the first negative electrode active material layer has a thickness of 10-120 μm and the second negative electrode active material layer has a thickness of 10-120 μm, as measured (average value of at least five measurements) based on scanning electron microscopy ion-polished cross-sectional morphology analysis (see JY / T010-1996).

[0048] In some embodiments, the negative electrode active material layer has a thickness of 30-150 μm, a porosity of 20-60%, optionally 25-40%, and further optionally 27-33%, and a compaction density of 1.2-1.9 g / cm. 3 and optionally 1.3-1.8 g / cm 3 It is.

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

[0050] In some embodiments, the primary and secondary lithium salts are different and each of the primary and secondary lithium salts is independently LiPF 6 , LiN(SO 2 F) 2 (LiFSI), LiBF 4 , LiN(CF 3 SO 2 ) 2 (LiTFSI), LiClO 4 , LiAsF 6 , LiB(C 2 O4 ) 2 (LiBOB), LiBF 2 C 2 O 4 (LiDFOB), lithium difluorobis(oxalato)phosphate (LiDFOP), LiPO 2 F 2 , LiFSO3, and LiF. The difference between the main lithium salt and the sub lithium salt is that their contents are different.

[0051] In some preferred embodiments, the primary lithium salt is lithium hexafluorophosphate or LiFSI or a mixture of both, the content of which is 8-20 wt %, optionally 10-15 wt %, based on the total weight of the electrolyte, and the secondary lithium salt is lithium difluoro(oxalato)borate LiBF 2 C 2 O 4 (LiDFOB), LiBF 4 , LiB(C 2 O 4 ) 2 (LiBOB), lithium difluorobis(oxalato)phosphate (LiDFOP), optionally LiDFOB or LiDFOP, the content of which 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, optionally 0.8-1.2 mol / L.

[0053] In some embodiments, the solvent comprises cyclic esters and linear esters, the cyclic ester content being 5-40% by weight of the solvent, optionally 25-35%, and the linear ester content being 60-95% by weight of the solvent, 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 comprises dimethyl carbonate (DMC).

[0055] In some embodiments, the linear ester may further comprise, 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 esters include dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC).

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

[0058] In some embodiments, the positive electrode comprises a current collector and an active positive electrode layer deposited on at least one surface of the current collector, the active positive electrode layer comprising an active positive electrode material having the formula LiNi x Co y Q z M 1-x-y-z O 2where 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, x+y+z≦1.

[0059] The lithium ion battery and power consuming device of the present application will now be described with appropriate 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 shuttle between the positive electrode and the negative electrode, absorbing and desorbing. The electrolyte functions to conduct ions between the positive electrode and the negative electrode. The separator is disposed between the positive electrode and the negative electrode, and mainly functions to prevent short-circuiting between the positive and negative electrodes, while allowing lithium ions to pass through.

[0061] positive electrode The positive electrode includes a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector, the positive electrode film layer including a positive electrode active material having the formula LiNi x Co y Q z M 1-x-y-z O 2 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, x+y+z≦1.

[0062] For example, the positive electrode current collector has two opposing surfaces in the thickness direction of the positive electrode current collector, and the positive electrode film layer is disposed on either 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, an aluminum foil may be used as the metal foil sheet. The composite current collector may include a polymeric material base layer and a metal layer formed on at least one surface of the polymeric material base layer. The composite current collector may be formed by forming a metal material on a polymeric material substrate. Here, the metal material includes, but is not limited to, aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, silver alloy, etc. The polymeric material substrate includes, but is not limited to, substrates such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.

[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 O 2 (NCM 333 (may be abbreviated as "LiNi") 0.5 Co 0.2 Mn 0.3 O 2 (NCM 523 (may be abbreviated as "LiNi") 0.5 Co 0.25 Mn 0.25 O 2 (NCM 211 (may be abbreviated as "LiNi") 0.6 Co 0.2 Mn 0.2 O 2 (NCM 622 (may be abbreviated as "LiNi") 0.65 Co 0.07 Mn 0.28 O 2 , LiNi 0.8 Co 0.1 Mn 0.1 O 2 (NCM 811 Lithium nickel cobalt aluminum oxide (e.g., LiNi 0.85 Co 0.15 Al0.05 O 2 ), LiNi 1 / 3 Co 1 / 3 Al 1 / 3 O 2 or at least one of its modifying compounds, preferably NCM 622 However, the present application is not limited to these materials, and other conventional materials that can be used as a positive electrode active material for a battery may also be used. These positive electrode active materials may be used alone 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 materials include lithium-containing phosphates with an olivine structure, lithium cobalt oxides (e.g., LiCoO 2 ), lithium nickel oxide (e.g., LiNiO 2 ), lithium manganese oxide (e.g., LiMnO 2 , LiMn 2 O 4 ), lithium manganese cobalt oxide, lithium nickel manganese oxide, and modified compounds thereof. An example of a lithium-containing phosphate having an olivine structure is lithium iron phosphate (e.g., LiFePO 4 (which may be abbreviated as LFP)), lithium iron phosphate and carbon composites, lithium manganese phosphate (e.g., LiMnPO 4 ), a composite material of lithium manganese phosphate and carbon, lithium iron manganese phosphate, and a composite material of lithium iron manganese phosphate and carbon, but are not limited thereto.

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

[0067] In some embodiments, the positive electrode membrane layer optionally further includes an adhesive. For example, the adhesive may include 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 membrane layer, the weight ratio of the adhesive in the positive electrode membrane layer is 0-20% by weight.

[0068] In some embodiments, the positive electrode membrane layer optionally further comprises a conductive agent. For example, the conductive agent may comprise 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 positive electrode membrane layer, the weight ratio of the conductive agent in the positive electrode membrane layer is 0-20% by weight.

[0069] In some embodiments, the positive plate may be manufactured in the following manner: The components for manufacturing the positive plate, such as the positive active material, conductive agent, adhesive and any other components, are dispersed in a solvent (e.g., N-methylpyrrolidone) to form a positive slurry, in which the solid content of the positive slurry is adjusted to 40-80 wt% and the viscosity at room temperature is adjusted to 5000-25000 mPa s, the positive slurry is coated on the surface of a positive current collector, dried, and then cold pressed by a cold rolling machine to form a positive plate, and the unit areal density of the positive powder coating is 12-26 mg / cm 2 The compaction density of the positive plate is 2.0-3.6g / cm 3 and optionally 2.3-3.5 g / cm 3 The formula for calculating the compaction density is as follows: Compaction density = coating surface density / (plate thickness after pressing - current collector thickness)

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

[0071] For example, the negative electrode current collector has two opposing surfaces in the thickness direction of the negative electrode current collector, and the negative electrode film layer is disposed on either 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, a copper foil may be used as the metal foil sheet. The composite current collector may include a polymeric material base layer and a metal layer formed on at least one surface of the polymeric material substrate. The composite current collector may be formed by forming a metal material on a polymeric material substrate. Here, the metal material includes, but is not limited to, copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, silver alloy, etc., and the polymeric material substrate includes, but is not limited to, polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.

[0073] In some embodiments, the negative electrode active material may be a negative electrode active material for batteries 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 silicone alone, silicon oxide, silicone carbon composite, silicone nitrogen composite, and silicone alloy. The tin-based material may be selected from at least one of tin alone, tin oxide, and tin alloy. However, the present application is not limited to these materials, and other conventional materials that can be used as a negative electrode active material for batteries may also be used. These negative electrode active materials may be used alone 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, SnO 2 , lithiated TiO with spinel structure 2 -Li 4 Ti 5 O 12 , Li-Al alloys.

[0075] In some embodiments, the negative electrode includes a current collector and a negative electrode active material layer deposited on at least one surface of the current collector, the active material layers including a first active material layer including a first negative electrode active material and a second active material layer including a second negative electrode active material deposited on a surface of the first active material layer remote 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, SnO 2 , lithiated TiO with spinel structure 2 -Li 4 Ti 5 O 12 , or Li-Al alloy, and the second negative electrode active material is at least one of 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, SnO 2 , lithiated TiO with spinel structure 2 -Li 4 Ti 5 O 12 , Li-Al alloy.

[0077] In some embodiments, when the negative electrode active material comprises a mixture of two or more materials, 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 comprises silicon, the silicon content of which is 1-25% by weight of the negative electrode active material layer and is distributed in at least one of the active material layers.

[0079] In some embodiments, the content of silicon (SiO) in the first active material layer is based on the weight of the first active material layer. 2 The silicon content (SiO ) in the second active material layer is 0-25%, based on the weight of the second active material layer. 2 (as) is 0-25%.

[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 membrane layer optionally further comprises an adhesive, which 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 membrane layer, the weight ratio of the adhesive in the negative electrode membrane layer is 0-30 wt%.

[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 membrane layer optionally further includes other auxiliary agents, such as a thickener (e.g., sodium carboxymethylcellulose (CMC-Na)), etc. Based on the total weight of the negative electrode membrane layer, the weight ratio of the other auxiliary agents in the negative electrode membrane layer is 0-15 wt%.

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

[0085] The porosity of the negative electrode active material layer can be obtained by a gas replacement method, and is expressed as 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 in the negative electrode per unit area can be obtained by weighing using a standard balance.

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

[0088] electrolyte The electrolyte serves to conduct ions between the positive and negative plates.

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

[0090] In some embodiments, the electrolyte includes a lithium salt, a solvent, and an additive, and the lithium salt includes a primary lithium salt and a secondary lithium salt.

[0091] In some embodiments, the primary and secondary lithium salts are different and each of the primary and secondary lithium salts is independently lithium hexafluorophosphate (LiPF 6 ), lithium bis(fluorosulfonyl)imide (LiN(SO 2 F) 2 , LiFSI), lithium tetrafluoroborate (LiBF 4 ), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium perchlorate (LiClO 4 ), lithium hexafluoroarsenate (LiAsF 6 ), lithium trifluoromethanesulfonate (LiTFS), lithium bis(oxalato)borate (LiB(C 2 O 4 ) 2 , LiBOB), lithium difluoro(oxalato)borate (LiBF 2 C 2 O 4 , LiDFOB), lithium difluorophosphate (LiPO 2 F 2 ), lithium difluorobis(oxalato)phosphate (LiDFOP), LiPO 2 F 2 , LiFSO 3 , LiF, and lithium tetrafluoro(oxalato)phosphate (LiTFOP).

[0092] In some embodiments, the primary and secondary lithium salts are different and each of the primary and secondary lithium salts is independently LiPF 6 , LiN(SO 2 F) 2 (LiFSI), LiBF 4 , LiN(CF 3 SO 2 )2 (LiTFSI), LiClO 4 , LiAsF 6 , LiB(C 2 O 4 ) 2 (LiBOB), LiBF 2 C 2 O 4 (LiDFOB), lithium difluorobis(oxalato)phosphate (LiDFOP), LiPO 2 F 2 , LiFSO3, and LiF. The difference between the main lithium salt and the sub lithium salt is that their contents are different.

[0093] In some preferred embodiments, the primary lithium salt is lithium hexafluorophosphate or LiFSI, the content of which is 8-20 wt % based on the total weight of the electrolyte, and the secondary lithium salt is lithium difluoro(oxalato)borate LiBF 2 C 2 O 4 (LiDFOB), LiBF 4 , LiB(C 2 O 4 ) 2 (LiBOB), lithium difluorobis(oxalato)phosphate (LiDFOP), and optionally LiDFOB or LiDFOP, the content of which 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, the cyclic ester content being 5-40% by weight of the solvent and the linear ester content being 60-95% by weight of the solvent.

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

[0097] In some embodiments, the linear ester may further comprise, 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 esters include dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC).

[0099] In some embodiments, the additives include carbonates (e.g., fluoroethylene carbonate FEC), sulfates (e.g., vinyl sulfate DTD), and sulfonates (e.g., 1,3-propane sultone PS). The carbonates include 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 sulfate ester includes 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 sulfonate ester includes at least one of 1,3-propane sultone (1,3-PS), propene sultone (PES), 3-fluoro-1,3-propane sultone (FPS), and vinyl methane disulfonate (MMDS). In some preferred embodiments, the additives include fluoroethylene carbonate (FEC), vinyl sulfate (DTD) and 1,3-propane sultone (1,3-PS).

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

[0101] In some embodiments, the electrolyte solution optionally further includes 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 performance of the battery, such as an additive that improves the overcharge performance of the battery, an additive that improves the high temperature or low temperature performance of the battery, etc.

[0102] Separator In some embodiments, the secondary battery further includes a separator. The present application is not particularly limited to the type of separator, and any known separator with a porous structure having good chemical stability 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 multi-layer composite film, and there is no particular limitation. When the separator is a multi-layer composite film, the materials of each layer may be the same or different, and there is no particular limitation.

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

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

[0106] In some embodiments, the secondary battery may include an exterior body, which may be used to package the electrode assembly and the electrolyte.

[0107] In some embodiments, the exterior of the secondary battery may be a hard case, such as a hard plastic case, an aluminum case, a steel case, etc. The exterior of the secondary battery may be a pouch, such as a bag-shaped pouch. The material of the pouch may be plastic, such as polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0108] The present application is not particularly limited to the shape of the secondary battery, which may be cylindrical, rectangular, or any other shape. For example, FIG. 1 shows a secondary battery 5 with a rectangular structure as an example.

[0109] In some embodiments, referring to FIG. 2, the exterior body may include a case 51 and a cover plate 53. The case 51 may include a bottom plate and a side plate connected on the bottom plate, and the bottom plate and the side plate surround the case 51 to form a receiving cavity. The case 51 has an opening communicating with the receiving cavity, and the cover plate 53 is provided to cover the opening to close the receiving cavity. The positive electrode plate, the negative electrode plate and the separator may form an electrode assembly 52 by a winding process or a stacking process. The electrode assembly 52 is packaged in the receiving cavity. The electrolyte is permeated into the electrode assembly 52. ​​The number of electrode assemblies 52 included in the secondary battery 5 may be one or more, and those skilled in the art may select according to actual specific needs.

[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, with the specific number being selectable by one skilled in the art based on the application and capacity of the battery module.

[0111] In the battery module, the secondary batteries 5 may be arranged in sequence along the longitudinal direction of the battery module, or may be arranged in any other manner. Furthermore, the secondary batteries 5 may be fixed by fasteners.

[0112] Optionally, the battery module may further include a housing having an accommodating space, and the multiple secondary batteries 5 are accommodated in the accommodating space.

[0113] In some embodiments, the battery modules may be further assembled into a battery pack, and the number of battery modules included in the battery pack may be one or more, and the specific number can be selected by one 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 may include an upper housing and a lower housing, and the upper housing may be provided to cover the lower housing to form a sealed space for accommodating the battery modules. The plurality of battery modules may be arranged in the battery box according to any manner.

[0115] The present application further provides a power consuming device, the power consuming device including at least one of the secondary battery, the battery module, or the battery pack according to the present application. The secondary battery, the battery module, or the battery pack may be used as a power source for the power consuming device, or may be used as an energy storage unit for the power consuming device. The power consuming device may include, but is not limited to, a mobile device (e.g., a mobile phone, a laptop, etc.), an electric vehicle (e.g., a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc.), an electric train, a ship, a satellite, an energy storage system, etc.

[0116] The power consumption device can be selected as a secondary battery, a battery module, or a battery pack depending on the demands of the usage.

[0117] 3 shows an example of a power consuming device, such as a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. A battery pack or a battery module can be adopted to meet the power consuming device's demand for high power and high energy density of secondary batteries.

[0118] Another example of the device may be a mobile phone, a tablet computer, a notebook computer, etc. Such devices are generally required to be lightweight and may employ a secondary battery as a power source.

[0119] Working Example In order to clarify the technical problems, technical solutions and beneficial effects that the present application aims to solve, the present application will be described in more detail below in conjunction with the embodiments and drawings. It is apparent that the described embodiments are only some of the embodiments of the present application, and not all of the embodiments. The following description of at least one exemplary embodiment is for illustrative purposes only, and is not a limitation on the present application and its applications. All other embodiments obtained based on the embodiments of the present application without the need for creative efforts by those skilled in the art are within the scope of protection of the present application.

[0120] If specific techniques or conditions are not specified in the examples, they will be performed according to techniques or conditions described in the literature in the art or in the product instructions. Reagents or instruments used that are not specified by manufacturer are all common products that can be purchased commercially.

[0121] 1. Example Example 1 1. Electrolyte production The electrolyte was prepared in a glove box with an argon gas atmosphere and a water content of <10 ppm. Ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) were mixed in a mass ratio of 3:5:2, and 1 mol / L of the main lithium salt LiPF 6 and the secondary lithium salt LiBF, which accounts for 1 wt% of the entire electrolyte. 4 +LiDFOB and the additive FEC+DTD+1,3-PS, which accounts for 4 wt% of the total electrolyte, were added and mixed uniformly to obtain the electrolyte. The viscosity of the electrolyte is 3.8 mPa.s.

[0122] 2. Manufacturing of positive electrode plates Positive electrode active material ternary material LiNi 0.65 Co 0.07 Mn 0.28 O 2The adhesive polyvinylidene fluoride and the conductive agent acetylene black were mixed in a weight ratio of 98:1:1 and dissolved in a solvent N-methylpyrrolidone (NMP) to prepare a positive electrode slurry. The slurry was then applied onto an aluminum foil current collector, dried, and then cold pressed, deburred, cut, slit, etc. to manufacture and prepare a positive electrode plate measuring 87 x 665 mm.

[0123] 3. Manufacturing of negative electrode plates The negative electrode active material graphite and SiO 2 The adhesive styrene butadiene rubber and the dispersant sodium carboxymethyl cellulose were dissolved in deionized water in a weight ratio of 96.5:1.5:1:1 to form a first negative electrode slurry. A 6 μm copper foil was used as the negative electrode current collector. The first layer of the negative electrode slurry was first coated on the negative electrode current collector, with the coating weight being 4.25 mg / cm. 2 The first active material layer was dried and then coated with the second negative electrode slurry. 2 A second negative electrode slurry was formed by dissolving styrene butadiene rubber as an adhesive and sodium carboxymethyl cellulose as a dispersant in deionized water at a weight ratio of 96.5:1.5:1:1, and the coating weight of the second active material layer was 4.25 mg / cm. 2 A second active material layer was formed.

[0124] The composite negative electrode plate was obtained through drying, cold pressing, and cutting. 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 / cm. 3 A negative plate with a size 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 thick alumina ceramic layer was coated on each side of the separator substrate. Finally, 2.5 mg of the adhesive polyvinylidene fluoride (PVDF) was coated on each side of the ceramic layer and then dried.

[0126] 5. Battery Assembly The positive electrode plate, separator, and negative electrode plate were sequentially wound or stacked, and the separator was positioned between the positive and negative electrode plates to obtain a bare cell. The bare cell was then placed in an exterior body, and 9.3 g of the above-prepared electrolyte was injected into the dried cell. After leaving the cell to stand, forming, shaping, and other processes, a lithium-ion secondary battery with a capacity of 3100 mAh was obtained.

[0127] The preparation steps of Examples 2-26 and Comparative Examples 1-3 are similar to that of Example 1, but the materials or compositions of the electrolyte or negative electrode are changed. See Table 1.

[0128] Parameter Test Porosity P% test of 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 diameter, such as helium gas or nitrogen gas, the actual volume of the sample to be tested is accurately measured by the displacement method, and the porosity of the sample to be tested is obtained by combining 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, the shear force experienced by the rotor as it continues to rotate at a constant speed on the sample generates a torque on the spring, which is proportional to the viscosity, thereby providing a viscosity value.

[0130] Specifically, Brookfield (DV-2TLV) viscometer was used to test the viscosity of the finished electrolyte. The environmental temperature was controlled at 25℃ and the environmental humidity was controlled at <80%, 30mL of electrolyte was taken and kept in a water bath at a constant temperature of 25℃ for at least 30 minutes, the rotor was placed in a sample cup, the sample was added to about 0.3cm from the mouth of the cup, the connected viscometer was started, the rotation speed was selected to 70RPM to perform the test, 10 data points were collected, and the average value of the multiple points was calculated.

[0131] [Table 1] JPEG2025515904000002.jpg254146JPEG2025515904000003.jpg253146

[0132] Second, battery performance test 1. Lithium release capacity of the positive electrode Disassemble the battery in the MBRAUN glove box of PRS340 / 11-119-11, take out the positive plate, and assemble a CR2430 type half coin cell battery with a positive electrode and lithium strip. The area of ​​the positive plate used is amm 2 Here, the electrolyte is LiPF 6 A solution containing 1M of 1M 100% ...

[0133] 2.Lithium storage capacity of the negative electrode Disassemble the battery in the glove box of PRS340 / 11-119-11MBRAUN, take out the negative plate, and assemble a negative-lithium strip CR2430 type half coin battery. The area of ​​the negative plate used is fmm 2 Here, the electrolyte is LiPF 6A solution containing 1M of 1M 100% ...

[0134] 3.Charging capacity test Rate performance test (test to charge to 70% SOC): The test temperature was adjusted to 35℃, and the lithium-ion battery was charged at xC rate (x is 0.5, 0.8, 1, 1.2, 1.5, 2, 2.5, 3), and then discharged at 1C. The charge rate was gradually increased, and the charge stop condition was set to 0V when the anode potential reached 0V. Simulation was performed to obtain the maximum possible charge rate within the range of 0-10% SOC, 10-20% SOC, 20-30% SOC, 30-40% SOC, 40-50% SOC, 50-60% SOC, and 60-70% SOC, and the charge time (min) required for 0-70% SOC was calculated.

[0135] 4. Cycle performance test At 25°C, the secondary battery was charged at a constant current of 1C to 4.3V, and then charged at a constant voltage of 0.05C, at which point the secondary battery was fully charged. The charge capacity at this time was recorded and used as the first charge capacity. The secondary battery was left to stand for 5 minutes, and then discharged at a constant current of 1C to 2.8V, which was one cycle charge / discharge process. The discharge capacity at this time was recorded and used 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 at 45°C after 600 cycles = discharge capacity after 600 cycles / first discharge capacity x 100%.

[0136] 3. Test results of each embodiment and comparative example According to the above-mentioned method, the batteries of the examples and the comparative examples were manufactured, and the performance parameters were 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 the present application has good fast 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 the porosity of the negative electrode active material is in the range of 25-40%, for example, the charging time required for 0-80% SOC can be shortened 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 the present application is not limited to the above-mentioned embodiment. The above-mentioned embodiment is an example, and any embodiment having substantially the same configuration as the technical idea and the same effect within the scope of the technical proposal of the present application is included in the technical scope of the present application. In addition, various modifications that a person skilled in the art can make to the embodiment and other forms constructed by combining some of the components in the embodiment are also included in the scope of the present application, within the scope of the purpose of the present 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 absorption capacity of the negative electrode to the lithium desorption capacity of the positive electrode is 1.05-1.

5.

2. 2. The battery according to claim 1, wherein a current is four or more times the positive electrode occlusion / desorption capacity per unit time during the process of charging the battery from a charge state of 0% to a charge state of 70% at 35°C.

3. 3. The battery according to claim 1, wherein an average current during charging of the battery at 35° C. from a charge state of 0% to a charge state of 70% is four or more times the positive electrode occlusion / desorption capacity per unit time.

4. The negative electrode includes a current collector and a negative electrode active material layer deposited on at least one surface of the current collector; The active material layer includes a first active material layer including a first negative electrode active material, and a second active material layer including a second negative electrode active material attached to a surface of the first active material layer remote from the current collector. The battery according to any one of claims 1 to 3, comprising:

5. The average volume particle size D of the first negative electrode active material ｖ５０ is the average volume particle size D of the second negative electrode active material ｖ５０ 5. The battery of claim 4, wherein the

6. 6. The battery according to claim 4, wherein the first negative electrode active material layer has a greater compaction density than the second negative electrode active material layer.

7. 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 / cm ３ The battery according to any one of claims 4 to 6, characterized in that

8. The electrolyte solution includes a lithium salt, a solvent, and an additive, 8. The battery according to claim 1, wherein the lithium salt includes a main lithium salt and a sub lithium salt.

9. The main lithium salt and the auxiliary lithium salt are different, and the main lithium salt and the auxiliary 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 9. The battery of claim 8, wherein the lithium ion is selected from at least one of the following: LiF.

10. The primary lithium salt is lithium hexafluorophosphate or LiFSI, the content of which 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 10. The battery according to claim 8, characterized in that the electrolyte is at least one of lithium difluorobis(oxalato)phosphate (LiDFOP), and the content thereof is 0.001 wt %-2 wt % based on the total weight of the electrolyte.

11. The battery according to any one of claims 8 to 10, characterized in that the solvent contains a cyclic ester and a linear ester, the content of the cyclic ester being 5-40% by mass of the solvent, and the content of the linear ester being 60-95% by mass of the solvent.

12. 12. The battery of claim 11, wherein the cyclic ester is ethylene carbonate, propylene carbonate, or a combination thereof, and the linear ester comprises dimethyl carbonate.

13. 13. The battery of claim 12, wherein 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.

14. In the electrolytic solution, the molar concentration b (mol / L) of the lithium salt, the percentage a % of the linear ester in the solvent relative to the solvent mass, and the viscosity c of the electrolytic solution at 25° C. satisfy the following relationship, i.e. 2≦c+2*a%≦8, The battery according to any one of claims 8 to 13, characterized in that 2≦c+b≦8.

15. The positive electrode includes a current collector and a positive electrode active material layer deposited on at least one surface of the current collector, the positive electrode active material having the formula LiNi ｘ Co ｙ Q ｚ M １－ｘ－ｙ－ｚ O ２ wherein Q is Mn or Al, M is at least one of Co, Ni, Mn, Mg, Cu, Zn, Al, Sn, B, Ga, Cr, Sr, V, and Ti, and 0≦x<1, 0≦y≦1, 0≦z≦1, and x+y+z≦1.

16. A power consuming device comprising the secondary battery according to any one of claims 1 to 15.

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