Lithium-ion secondary battery

Abstract

Lithium-ion secondary battery, characterized in that the lithium-ion secondary battery comprises a positive electrode plate, a negative electrode plate and an electrolyte solution, wherein the final charging voltage of the lithium-ion secondary battery is ≥ 4.5 V, wherein the positive electrode plate comprises an active coating for the positive electrode containing an active material for the positive electrode and a solid electrolyte, wherein the active material for the positive electrode comprises a lithium cobalt oxide containing Al element, wherein the mass content c1 of the Al element in the active coating for the positive electrode is 6800 ppm - 15000 ppm, wherein the solid electrolyte comprises at least one compound of lithium aluminum titanium phosphorus oxide, lithium lanthanum zirconium tantalum oxide, and lithium lanthanum titanium oxide, wherein the negative electrode plate comprises a negative electrode active coating comprising a negative electrode active material containing a silicon-carbon material, wherein the mass content c2 of the Si element in the negative electrode active coating is 1.5% - 20%, and wherein the electrolyte solution comprises a solvent containing a carboxylic acid ester compound.

Description

Technical field

[0001] The present utility model relates to the technical field of batteries and, in particular, to a lithium-ion secondary battery. State of the art

[0002] Users strive for high battery capacity in any case. Increasing battery capacity results from improving the gram capacity of the materials, either for the negative electrode by increasing the gram capacity of the negative electrode material through doping with silicon, or for the positive electrode by increasing the gram capacity of the positive electrode material by increasing the cut-off voltage. However, at high voltages, the crystal lattice structure in the positive electrode material could collapse during battery charging / discharging, thus deteriorating the battery's cycling stability. Since silicon itself has poor electrical conductivity, the battery's low-temperature discharge characteristics deteriorate significantly when the negative electrode plate is coated with silicon, especially with a large amount of silicon (such as silicon).with silicon element in a mass content greater than or equal to 5% in the active coating for the negative electrode).

[0003] Therefore, the cycle stability and low-temperature discharge characteristics of the high-energy-density battery should be improved simultaneously. Disclosure of the utility model

[0004] The object of the present utility model is to overcome the problems of poor cycle stability and poor low-temperature discharge characteristics of a high-energy-density battery in the prior art and to provide a lithium-ion secondary battery. The lithium-ion secondary battery (hereinafter referred to as the battery) of the utility model uses a silicon-carbon material as the negative electrode active material and a lithium cobalt oxide as the positive electrode active material, so that, in combination with a high cut-off voltage (for example, ≥ 4.5 V), a high energy density can be achieved. Furthermore, by adjusting the content of the Al element in the lithium cobalt oxide, the crystal lattice structure of lithium cobalt oxide is stabilized, thereby improving the cycle stability of the battery.Regarding the problem of poor discharge characteristics of a battery with a large amount of doped silicon (such as with silicon element in a mass content greater than or equal to 5% in the active coating for the negative electrode) at low temperature, a solid electrolyte is added to the positive electrode plate and a certain solvent is added to the electrolyte solution to improve the discharge characteristics of the battery at low temperature.

[0005] The present utility model provides a lithium-ion secondary battery comprising a positive electrode plate, a negative electrode plate, and an electrolyte solution, wherein the end-of-charge voltage of the lithium-ion secondary battery is ≥ 4.5 V, wherein the positive electrode plate comprises an active coating for the positive electrode containing an active material for the positive electrode and a solid electrolyte, wherein the active material for the positive electrode comprises a lithium cobalt oxide containing Al element, wherein the mass content c1 of the Al element in the active coating for the positive electrode is 6800 ppm - 15000 ppm, wherein the solid electrolyte comprises at least one compound of lithium aluminum titanium phosphorus oxide, lithium lanthanum zirconium tantalum oxide, and lithium lanthanum titanium oxide, wherein the negative electrode plate comprises an active coating for the negative electrode,which comprises a negative electrode active material containing a silicon-carbon material, wherein the mass content c2 of the Si element in the negative electrode active coating is 1.5% - 20%, and wherein the electrolyte solution comprises a solvent containing a carboxylic acid ester compound.

[0006] As the upper limit of the battery's charging voltage increases, the potential on the positive electrode also becomes higher, which poses an ever-increasing challenge to the stability of the lithium cobalt oxide crystal lattice structure. On the one hand, the Al element can form an Al-O bond with the O element in the lithium cobalt oxide, which has a high bond energy, effectively suppressing the escape of oxygen from the crystal lattice. On the other hand, Al 3+The octahedral structure of lithium cobalt oxide is more stable, making it difficult for lithium cobalt oxide to convert into monoclinic crystals. This reduces the dynamics of monoclinic crystal formation, and thus suppresses the phase shift of lithium cobalt oxide. Therefore, adjusting the mass content of the Al element in the positive electrode active coating can achieve stabilization of lithium cobalt oxide. However, a higher content of the Al element does not always lead to better results. This is because increasing the Al element content reduces the gram capacity of lithium cobalt oxide, thus affecting the energy density of the entire battery. Therefore, adjusting the mass content of the Al element in the positive electrode active coating is necessary.If it is within a certain range, it can ensure that the positive electrode plate operates stably at a high voltage (for example, 4.5 V or more) and that the positive electrode plate has a sufficient specific capacity, and the loss of energy density due to an excessive mass content of the Al element can be prevented.

[0007] Silicon-carbon materials exhibit poor electrical conductivity, and the ionic conductivity of the electrolyte solution decreases significantly with lowering the temperature. In particular, systems doped with a large amount of silicon (such as those with a silicon element in a mass content greater than or equal to 5% in the negative electrode active coating) face the problem of the battery not being able to discharge under extreme weather conditions with low temperatures (such as temperatures of -20°C or lower). The ionic conductivity of a solid electrolyte decreases insignificantly with lowering the temperature.The addition of the solid electrolyte to the positive electrode plate allows ions to conduct along the solid electrolyte at extremely low temperatures, partially replacing the conduction path in the electrolyte solution, ensuring that the battery can discharge normally at low temperatures. Since discharge involves the removal of lithium from the negative electrode and its insertion into the positive electrode, it is preferable to accelerate the insertion of lithium into the positive electrode to improve the battery's low-temperature discharge characteristics. Therefore, the solid electrolyte is added to the positive electrode plate.

[0008] The solution described above can improve the battery's cycle stability and thus the battery's low-temperature discharge characteristics to a certain extent. However, the improvement in low-temperature discharge characteristics does not achieve the desired goal. Therefore, the battery's low-temperature discharge characteristics should be further improved. Compared to carbonate substances, carboxylic acid ester compounds have a lower melting point and lower viscosity, which means they remain more liquid at low temperatures and thus retain electrical conductivity and discharge characteristics. Furthermore, carboxylic acid ester compounds contribute to the formation of a stable, dense SEI (Solid Electrolyte Interphase) film with low impedance, which is essential for the battery's low-temperature discharge characteristics.Therefore, adding a carboxylic acid ester compound to the electrolyte solution can improve the electrochemical properties of the electrolyte solution, optimize the solvated structure of lithium ions, and form a stable SEI layer, thereby significantly improving the low-temperature discharge characteristics of the battery.

[0009] With the technical solutions described above, the present utility model has the following advantages over the prior art: The battery of the present utility model can have both a high energy density and excellent cycle stability and discharge properties at low temperatures.

[0010] The endpoints of a range or values ​​disclosed herein are not intended to be limited to the exact range or values, but should be understood to include the range or values ​​also including the values ​​that are close to the range or values. With respect to value ranges, one or more new value ranges can be obtained by combining endpoints of different ranges, an endpoint of a range with a stand-alone value point, and stand-alone value points, which are considered to be specifically disclosed herein. Short description of the characters Fig. Fig. 1 shows a schematic view (top view) of a groove in the surface of a negative electrode plate according to an example of the present utility model, wherein in Fig. 1(a) the groove is arranged continuously and in Fig. 1(b) the groove is arranged in sections. Fig.Fig. 2 shows a schematic view for the width of the groove according to an example of the present utility model, wherein in Fig. 2(a) to Fig. 2(c) the two longer sides of the groove are straight and in Fig. 2(d) the two longer sides of the groove are curved. Fig. Fig. 3 shows a schematic view for the distance of the groove according to an example of the present utility model, wherein in Fig. 3(a) the two adjacent longer sides are straight and parallel to each other, in Fig. 3(b) the two adjacent longer sides are straight but not parallel, and in Fig. 3(c) the two adjacent longer sides are curved. Fig. 4 shows a schematic structural view of a wound core according to an example of the present utility model. Fig. Fig. 5 is a schematic structural view of a positive electrode plate according to an example of the present utility model, wherein Fig. 5(a) is a plan view and Fig. 5(b) is a sectional view in the thickness direction. Fig. 6 shows a schematic plan view of a first surface of the positive electrode plate according to an example of the present utility model. Detailed embodiments

[0011] The following describes the specific embodiments of the present utility model in more detail. It should be understood that the detailed embodiments serve only to describe and explain the present utility model, without limiting it.

[0012] The present utility model provides a lithium-ion secondary battery comprising a positive electrode plate, a negative electrode plate, and an electrolyte solution. The cut-off voltage of the lithium-ion secondary battery is ≥ 4.5 V, for example, 4.5 V or 4.53 V. The term cut-off voltage has the proper meaning in the field and refers to the maximum voltage value the battery can safely reach during charging.

[0013] In the present utility model, the positive electrode plate may include a positive electrode active coating. The positive electrode active coating may include a positive electrode active material and a solid electrolyte. The positive electrode active material may contain lithium cobalt oxide. The lithium cobalt oxide contains Al element, and the mass content c1 of the Al element in the positive electrode active coating may be 6800 ppm - 15000 ppm, for example, 6800 ppm, 7000 ppm, 8000 ppm, 9000 ppm, 10000 ppm, 11000 ppm, 12000 ppm, 13000 ppm, 14000 ppm, or 15000 ppm.

[0014] In an example, c1 is 7100 ppm - 10000 ppm.

[0015] In the present utility model, the mass content c1 of the Al element in the positive electrode active coating can be measured using a conventional method in the field, such as inductively coupled plasma optical emission spectrometer (ICP-OES). The specific measurement method is as follows: The battery is discharged to 0% SOC and disassembled. The positive electrode plate is removed and immersed in a dimethyl carbonate (DMC) solvent for 12 hours. The positive electrode plate is then washed with the DMC solvent to remove the adhering lithium salt. After calcining in a muffle furnace at 400°C for 3 hours, the positive electrode active coating is lightly scraped off the surface of the positive electrode current collector. The mass content of the Al element is measured in ppm (parts per million) using ICP-OES. The specific implementation of the method is in accordance with GB / T 30902-2014.

[0016] In the present utility model, the chemical formula of lithium cobalt oxide Li a Co b M 1 c O2, where 0.8 ≤ a ≤ 1.05, 0.85 ≤ b < 1, 0 < c ≤ 0.15 and M 1at least one of Al, Mg, Ti, Y, La, Ga, Ge, Sn, Si, Zr, Ca, Sb, In, Ni and Mn. The lithium cobalt oxide may comprise first particles having an average particle size of 0.3 µm - 7 µm (for example, 0.3 µm, 0.5 µm, 1 µm, 2 µm, 3 µm, 4 µm, 5 µm, 6 µm, 7 µm) and second particles having an average particle size of 7.5 µm - 40 µm (for example, 7.5 µm, 10 µm, 15 µm, 20 µm, 25 µm, 30 µm, 35 µm or 40 µm). By using the lithium cobalt oxide with the first and second particles having different average particle sizes, due to their deviation in particle size distribution, the filling of the lithium cobalt oxide powder during the pressing process and thus the compact density and electron conductivity of the lithium cobalt oxide can be directly influenced, which is conducive to improving the energy density and fast charging capability of the entire battery.

[0017] In the present utility model, the average particle sizes of the first particles and the second particles can be measured using a conventional method in the field. For example, the battery is discharged to 0% SOC and disassembled. The positive electrode plate is removed and immersed in a dimethyl carbonate (DMC) solvent for 12 hours. The positive electrode plate is then washed with the DMC solvent to remove the lithium salt adhering thereto. After calcining in a muffle furnace at 400°C for 3 hours, the positive electrode active coating is lightly scraped off from the surface of the positive electrode current collector. Measurement is performed on a laser particle sizer to enable the particle size ranges of the first particles and the second particles to be determined from the curve thus obtained.

[0018] In the present utility model, the solid electrolyte may comprise at least one compound of lithium aluminum titanium phosphorus oxide, lithium lanthanum zirconium tantalum oxide, and lithium lanthanum titanium oxide. The lithium aluminum titanium phosphorus oxide may be a lithium aluminum titanium phosphorus oxide of the superionic conductor type with a molecular formula of Li 1+x Al x Ti 2-x (PO4)3, with 0 < x ≤ 0.5. The lithium lanthanum zirconium tantalum oxide can be a garnet-type lithium lanthanum zirconium tantalum oxide with a molecular formula of Li 7-y La3Zr 2-y Ta y O 12 , with 0 ≤ y ≤ 0.5. The lithium lanthanum titanium oxide may be a perovskite-type lithium lanthanum titanium oxide with a molecular formula of Li 3z La 2 / 3-zTiO3, where 0 < z ≤ 0.2. The solid electrolyte satisfying the above-mentioned molecular formula exhibits strong ionic conductivity and a high dielectric factor, as well as good affinity for the electrolyte solution. When used in a positive electrode plate, it can increase the ion transfer ability of the positive electrode plate and improve the dynamics of the battery, so that the battery has good low-temperature discharge characteristics and good cycling stability while maintaining high energy density.

[0019] In the present utility model, the negative electrode plate may comprise a negative electrode active coating. The negative electrode active coating may comprise a negative electrode active material containing a silicon-carbon material. A silicon-carbon material is understood to mean a composite material containing the elements carbon and silicon, including, for example, a material formed from silicon and / or oxidized silicon (partially or completely) filled in the pores of a porous carbon.

[0020] In the present utility model, the mass content c2 of the Si element in the active coating for the negative electrode may be 1.5% - 20%, for example 1.5%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19% or 20%.

[0021] In one example, c2 is 4% - 12%.

[0022] In the present utility model, the mass content c2 of the Si element in the negative electrode active coating can be measured using a conventional method in the field. For example, the battery is discharged to 0% SOC and disassembled. The negative electrode plate is removed and immersed in a DMC solvent for 12 hours. Then, the negative electrode plate is washed with the DMC solvent to remove the lithium salt adhering to it. After air drying, the negative electrode plate is subjected to a high-temperature treatment at 400°C for 2 hours in an inert atmosphere (such as a tube furnace in a nitrogen or argon atmosphere). The negative electrode active coating is then scraped off from the negative electrode current collector. The negative electrode active coating is collected as a test sample.On a thermogravimetric analyzer (such as a TGA 550 model), a 5 mg - 15 mg test sample is taken, heated from room temperature (25 °C) to 900 °C at a heating rate of 10 °C / min in an air or oxygen atmosphere, and held at 900 °C for 40 minutes, so that the silicon is sufficiently oxidized to silicon dioxide upon evaporation of components other than silicon in the negative electrode active coating. The remaining substance is the ash of the negative electrode active coating, and from the mass of the ash, the mass content of the Si element in the negative electrode active coating can be calculated using the following equation: . The mass content of the Si element in the active coating for the negative electrode = 7 × mass of the ash / (15 × mass of the test sample).

[0023] In the present utility model, the mass content of the Si element in the silicon-carbon material may be 30% - 80%, for example 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75% or 80%.

[0024] In the present utility model, the electrolyte solution may comprise a solvent. The solvent may contain a carboxylic acid ester compound. The carboxylic acid ester compound includes, for example, at least one of the following solvents, which may be substituted or unsubstituted with fluorine: ethyl acetate, propyl acetate, n-butyl acetate, isobutyl acetate, n-pentyl acetate, isopentyl acetate, methyl propionate (PP), ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, and ethyl n-butyrate.

[0025] In the present utility model, the mass content of the carboxylic acid ester compound in the electrolyte solution may be 10% - 80%, for example 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75% or 80%.

[0026] In one example, the mass content of the carboxylic acid ester compound in the electrolyte solution is 20% - 65%.

[0027] In the present utility model, the mass content of the carboxylic acid ester compound in the electrolyte solution can be measured using a conventional method in the field. For example, the battery is discharged to 0% SOC. The electrolyte solution is extracted from the battery and measured by gas chromatography (GC).

[0028] In the present utility model, the solid electrolyte contains a characteristic element. The characteristic element includes at least one of Ti, Zr, La, and Ta. The ratio of the mass content c3 of the characteristic element in the positive electrode active coating to the mass content c4 of the Co element in the positive electrode active coating can be 0.001-0.0055, for example, 0.001, 0.0015, 0.002, 0.0025, 0.003, 0.0035, 0.004, 0.0045, 0.005, or 0.0055.

[0029] In one example, the ratio of the mass content c3 of the characteristic element in the positive electrode active coating to the mass content c4 of the Co element in the positive electrode active coating is 0.0015 - 0.0035.

[0030] By adjusting the ratio of the mass content of the characteristic element to the mass content of the cobalt element in the positive electrode active coating, both low-temperature discharge characteristics and high-temperature stabilization of the battery can be achieved. This is because the ratio between them indicates the mass ratio of the solid electrolyte to the lithium cobalt oxide in the positive electrode active coating. Therefore, when the ratio between them is small (such as less than 0.001), the mass content of the solid electrolyte in the positive electrode active coating is relatively low, and the solid electrolyte exhibits limited improvement in the low-temperature discharge characteristics of the battery.On the other hand, when the ratio between them is large (such as greater than 0.0055), there is a relatively high mass content of the solid electrolyte in the positive electrode active coating, which affects the high-temperature characteristics of the battery because the solid electrolyte is unstable in a high-temperature environment and is easy to generate gas.

[0031] In the present utility model, the mass content c3 of the characteristic element in the positive electrode active coating may be 600 ppm - 3000 ppm, for example 600 ppm, 700 ppm, 800 ppm, 900 ppm, 1000 ppm, 1100 ppm, 1200 ppm, 1300 ppm, 1400 ppm, 1500 ppm, 1600 ppm, 1700 ppm, 1800 ppm, 1900 ppm, 2000 ppm, 2500 ppm or 3000 ppm.

[0032] In one example, c3 is 900 ppm - 2000 ppm.

[0033] In the present utility model, the mass content c3 of the characteristic element in the positive electrode active coating can be measured using a conventional method in the field, such as ICP-OES. The specific measurement method is as follows: The battery is discharged to 0% SOC and disassembled. The positive electrode plate is removed and immersed in a DMC solvent for 12 hours. The positive electrode plate is then washed with the DMC solvent to remove the adhered lithium salt. After calcining in a muffle furnace at 400°C for 3 hours, the positive electrode active coating is lightly scraped off the surface of the positive electrode current collector. The mass content of the characteristic element is measured in ppm (parts per million) using ICP-OES. The specific method is implemented according to GB / T 30902-2014.

[0034] In the present utility model, the mass content c3 of the characteristic element in the positive electrode active coating refers to the mass content of at least one characteristic element of the solid electrolyte in the positive electrode active coating. For example, if the solid electrolyte is a lithium lanthanum zirconium tantalum oxide containing three characteristic elements of La, Zr, and Ta, it is sufficient that the mass content of at least one of the elements La, Zr, and Ta in the positive electrode active coating satisfies the above-described condition regarding c3.

[0035] In the present utility model, the mass content c4 of the Co element in the active coating for the positive electrode can be 400000 ppm - 750000 ppm, for example 400000 ppm, 450000 ppm, 500000 ppm, 550000 ppm, 600000 ppm, 650000 ppm, 700000 ppm or 750000 ppm.

[0036] In one example, c4 is 500000 ppm - 650000 ppm.

[0037] In the present utility model, the average particle size of the solid electrolyte may be 500 nm - 3 µm, for example, 500 nm, 600 nm, 700 nm, 800 nm, 900 nm, 1 µm, 1.1 µm, 1.2 µm, 1.3 µm, 1.4 µm, 1.5 µm, 1.6 µm, 1.7 µm, 1.8 µm, 1.9 µm, 2 µm, 2.1 µm, 2.2 µm, 2.3 µm, 2.4 µm, 2.5 µm, 2.6 µm, 2.7 µm, 2.8 µm, 2.9 µm or 3 µm.

[0038] In one example, the average particle size of the solid electrolyte can be 1 µm - 2 µm.

[0039] In the present utility model, the average particle size of the solid electrolyte can be measured using a conventional method in the field. For example, the battery is discharged to 0% SOC and disassembled. The positive electrode plate is removed and immersed in a DMC solvent for 12 hours. Then, the positive electrode plate is washed with the DMC solvent to remove the adhered lithium salt. Using an argon ion dilution device (CP), the positive electrode plate is laser-cut and then observed by SEM. At a magnification of 5K, it is measured by randomly selecting at least 20 solid electrolyte particles, measuring their particle sizes, and averaging them. If the number of solid electrolyte particles is less than 20 at a magnification of 5K, another image is taken until 20 solid electrolyte particles are present.

[0040] In the present utility model, the electrolyte solution may also include vinylene carbonate (VC). VC is an unsaturated additive with good film-forming ability. It can be preferentially reduced and decomposed at the negative electrode during battery formation and participate in the formation of an SEI film to ensure the stability of the interface between the silicon-carbon material and the electrolyte solution. (Therefore, the VC content in the electrolyte solution, measured in the finished battery, is significantly lower than the amount of VC used in battery production.)) The SEI film, which is derived from the reduction and decomposition of the VC, can contribute to the suppression of the volume expansion of the silicon-carbon material during cycling due to the enrichment of some highly elastic polymers, so that a high mobility of lithium ions in the SEI film is ensured with an increased cycling stability and thus the discharge characteristics of the battery at low temperature are improved.

[0041] In the present utility model, the mass content c5 of vinylene carbonate in the electrolyte solution can be 0.01% - 15%, for example 0.01%, 0.05%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14% or 15%.

[0042] In the present utility model, the vinylene carbonate mass content c5 in the electrolyte solution can be measured using a conventional method in the field. For example, the battery is discharged to 0% SOC. The electrolyte solution is extracted from the battery and measured by GC.

[0043] In the present utility model, the mass content c3 of the characteristic element in the active coating for the positive electrode and the mass content c1 of the Al element in the active coating for the positive electrode are 5 × 10 -6 ≤ c3 × c1 ≤ 2.5 × 10 - 5 , for example 5 × 10 -6 , 6 × 10 -6 , 7 × 10 -6 , 8 × 10 -6 , 9 × 10 -6 , 1 × 10 -5 , 1.5 × 10 -5 , 2 × 10 -5 or 2.5 × 10 -5 .

[0044] In one example, 9.3 × 10 -6 ≤ c3 × c1 ≤ 1.5 × 10 -5 .

[0045] The mass content of the Al element in the positive electrode active coating affects the gram capacity of the positive electrode active material, and the low-temperature discharge capacity of the battery decreases with the increase in the mass content of the Al element. The content of the characteristic element directly affects the low-temperature discharge characteristics of the battery, so the low-temperature discharge capacity of the battery increases to a certain extent with the increase in the content of the characteristic element. Therefore, the battery has a high low-temperature discharge capacity, and no deterioration of the high-temperature characteristics occurs due to the excess of the solid electrolyte when the two contents satisfy a specific relationship.

[0046] In the present utility model, the silicon-carbon material may comprise primary spherical particles. The average particle size of the primary spherical particles may be 1 µm - 6 µm, for example, 1 µm, 2 µm, 3 µm, 4 µm, 5 µm, or 6 µm.

[0047] In one example, the average particle size of the primary spherical particles is 3 µm - 5 µm.

[0048] In the present utility model, the average particle size of the primary spherical particles can be measured using a conventional method in the field. For example, the battery is discharged to 0% SOC and disassembled. The negative electrode plate is removed and immersed in a DMC solvent for 12 hours. Then, the negative electrode plate is washed with the DMC solvent to remove the lithium salt adhering to it. Using an argon ion thinning device (CP), the negative electrode plate is laser-cut and then observed by SEM (in a high-voltage mode (back-scattered electrons BSE), in which the contrast of the silicon-carbon material is relatively high, so that the graphite material is distinguished from the electrically conductive agent in the negative electrode active coating).At a magnification of 5K, it is measured by randomly selecting at least 20 primary spherical particles, measuring their particle size, and averaging them. If the number of primary spherical particles is less than 20 at a magnification of 5K, another image is acquired until 20 primary spherical particles are present.

[0049] A typical silicon-carbon material is in the form of a block with an average particle size of approximately 6 µm - 12 µm. A large average particle size leads to poor conductivity of the particles. Furthermore, the high hardness of the silicon-carbon material results in a low compact density, making it difficult for the silicon content in the active coating for the negative electrode to reach 5% or more, thus resulting in only a limited increase in the energy density of the battery. By using the silicon-carbon material with primary spherical particles having an average particle size of 1 µm - 6 µm, not only a high silicon content, i.e.a silicon content in the active coating for the negative electrode of 1.5% - 20%, which significantly increases the energy density of the battery, but also maintains a small particle size, which improves the overall conductivity of the negative electrode plate and thus the discharge characteristics of the battery at low temperatures.

[0050] In the present utility model, the silicon-carbon material may also include secondary spherical particles formed from some primary spherical particles. The term "some" means that the number of primary spherical particles forming a secondary spherical particle is greater than 2.

[0051] Primary spherical particles with smaller particle sizes are beneficial for improving the energy density of the battery. However, such small particle sizes result in a large specific surface area, a correspondingly increased risk of side reactions with the electrolyte solution, and poor stability. To reduce the side reactions between the silicon-carbon material and the electrolyte solution, secondary spherical particles composed of several primary spherical particles are further added. Since the secondary spherical particles with a larger particle size have a small specific surface area, the risk of side reactions with the electrolyte solution is reduced and better stability is achieved.

[0052] In the present utility model, the average particle size of the secondary spherical particles may be 3 µm - 20 µm, for example 3 µm, 4 µm, 5 µm, 6 µm, 7 µm, 8 µm, 9 µm, 10 µm, 11 µm, 12 µm, 13 µm, 14 µm, 15 µm, 16 µm, 17 µm, 18 µm, 19 µm or 20 µm.

[0053] In the present utility model, the average particle size of the secondary spherical particles can be measured using a conventional method in the field. For example, the battery is discharged to 0% SOC and disassembled. The negative electrode plate is removed and immersed in a DMC solvent for 12 hours. Then, the negative electrode plate is washed with DMC to remove the lithium salt adhering to it. Using an argon ion thinning device (CP), the negative electrode plate is laser-cut and then observed with SEM (in high-voltage mode). At a magnification of 5K, it is measured by randomly selecting at least 20 particles of the secondary spherical particles, measuring their particle sizes, and averaging them.If the number of secondary spherical particles is less than 20 at a magnification of 5K, another image is taken until there are 20 secondary spherical particles in it.

[0054] In the present utility model, the proportion of the number of primary spherical particles in the total number of primary and secondary spherical particles in the negative electrode active coating is 0.1 - 0.9, for example, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8 or 0.9.

[0055] In one example, the proportion of the number of primary spherical particles in the total number of primary and secondary spherical particles in the negative electrode active coating is 0.3 - 0.8.

[0056] In the present utility model, the number of primary spherical particles and the number of secondary spherical particles in the negative electrode active coating can be measured using a conventional method in the field. For example, the battery is discharged to 0% SOC and disassembled. The negative electrode plate is removed and immersed in a DMC solvent for 12 hours. Then, the negative electrode plate is washed with DMC solvent to remove the adhered lithium salt. In the thickness direction of the negative electrode plate, the negative electrode plate is laser-cut using an argon ion thinning device (CP), and then observed with SEM (in a high-voltage mode) to capture an image of the cross-section of the negative electrode plate in the thickness direction.At a magnification of 1K, it is measured by selecting at least 20 images of different sections and counting and averaging the number of primary spherical particles and the number of secondary spherical particles in each of the images.

[0057] In the present utility model, the negative electrode active material may also comprise a graphite material. The graphite material includes, for example, artificial graphite and / or natural graphite. The graphite material includes secondary particles. The secondary particles are formed from several primary particles. The term "several" means that the number of primary particles forming one secondary particle is greater than two.

[0058] In the present utility model, the average particle size of the secondary particles may be 6 µm - 20 µm, for example 6 µm, 7 µm, 8 µm, 9 µm, 10 µm, 11 µm, 12 µm, 13 µm, 14 µm, 15 µm, 16 µm, 17 µm, 18 µm, 19 µm or 20 µm.

[0059] By customizing the use of a specific graphite material and adjusting the structure and particle size of the graphite material, the graphite material includes secondary particles formed from primary particles and has an average particle size of 6 µm - 20 µm, so that the energy density of the battery can be further increased. Compared with the graphite material containing primary particles, the graphite material containing secondary particles with a specific particle size can increase the energy density of the battery. Therefore, the graphite material better matches the specific silicon-carbon material, which is beneficial for increasing the energy density of the battery.

[0060] In the present utility model, the average particle size of the secondary particles can be measured using a conventional method in the field. For example, the battery is discharged to 0% SOC and disassembled. The negative electrode plate is removed and immersed in a DMC solvent for 12 hours. The negative electrode plate is then washed with the DMC solvent to remove the lithium salt adhering thereto. Subsequently, the negative electrode active coating is washed off the negative electrode current collector with deionized water, ultrasonicated, and centrifuged. After removing the filtrate and drying in air, the obtained sample is dispersed in deionized water containing nonylphenol polyoxyethylene ether (in which the mass content of nonylphenol polyoxyethylene ether is 0.02%-0.03%) to obtain a mixture.After ultrasonic treatment for 2 minutes, a measurement is performed using a Malvern particle size tester, so that the obtained mean particle size Dv50 represents the average particle size of the secondary particles. Due to the specific compositions and particle sizes of the graphite material and the silicon-carbon material in the present utility model, the silicon-carbon material has little influence on the average particle size of the secondary particles of the graphite material. Therefore, the data measured by the measurement method described above represent the average particle size of the secondary particles.

[0061] In the present utility model, the lithium-ion secondary battery may also include a separator. The separator may include an organic coating comprising polymer particles containing at least one of the cyano, isocyano, isocyanate, and triazinyl groups. For example, the polymer particles include at least one of polyacrylonitrile, nitrile rubber, 1,3,5-triazine-2,4,6-triamine, cyanuric acid, melamine, and melamine trithiocyanurate.

[0062] In one example, the organic coating faces the positive electrode plate.

[0063] With an organic coating facing the positive electrode plate, the organic cyanide compound in the organic coating can diffuse to the surface of the positive electrode plate, which serves to stabilize the metallic ions and the crystalline structure of the positive electrode active material and reduce the release of active oxygen, promotes the increase of the stability of the positive electrode active material and thus improves the cycle stability of the battery.

[0064] In the present utility model, the mass content of the N element in the organic coating may be 10.5% - 55%, for example 10.5%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50% or 55%.

[0065] In one example, the mass content of the N element in the organic coating is 15% - 35%.

[0066] In the present utility model, the mass content of the N element in the organic coating can be measured using a conventional method in the field. For example, the battery is discharged to 0% SOC and disassembled. The separator is removed and immersed in a DMC solvent for 12 hours. The separator is then washed with DMC solvent to remove the adhered lithium salt. The adhesive layer on the outer surface of the organic coating is gently peeled off using an adhesive strip (if there is no adhesive layer on the outer surface of the organic coating, this step is omitted), and the organic coating is then observed using SEM combined with an energy dispersive spectrometer (EDS).At a magnification of 30K, the particles in the organic coating are scanned point by point, with at least 20 locations being selected, their mass content of the element nitrogen being measured and averaged.

[0067] In the present utility model, the separator may also comprise a substrate layer and / or an adhesive layer. The substrate layer comprises, for example, polyethylene. The adhesive layer comprises, for example, polyvinylidene fluoride (PVDF) and / or polymethyl methacrylate (PMMA).

[0068] In one example, the separator comprises the substrate layer, the organic coating on one surface of the substrate layer, and the adhesive layer on the other surface of the substrate layer.

[0069] In one example, the separator comprises the substrate layer, the organic coating on one surface of the substrate layer, and the adhesive layer on the two outer surfaces of the separator.

[0070] In the present utility model, the thickness h of the organic coating can be 0.5 µm - 4 µm, for example 0.5 µm, 1 µm, 2 µm, 3 µm or 4 µm.

[0071] In one example, h is 1 µm - 2 µm.

[0072] In the present utility model, the outer surface of the negative electrode active coating may be provided with first recesses. The negative electrode plate comprises a negative electrode current collector and the negative electrode active coating on at least one surface of the negative electrode current collector. The outer surface of the negative electrode active coating is the surface of the negative electrode active coating facing away from the negative electrode current collector.

[0073] On the outer surface of the negative electrode active coating, first recesses are provided, which create a certain free space for the volume expansion of the negative electrode active material, which can reduce the expansion of the negative electrode current collector caused by the volume expansion of the negative electrode active material and promote the further improvement of the cycle stability of the battery.

[0074] In the present utility model, the first recess may comprise either a recessed hole or a groove. The first recess may be created by laser drilling or linear laser cutting. If the first recess is a groove, it may be arranged either continuously or in sections. Fig. Fig. 1 shows a schematic view (top view) of a groove in the surface of a negative electrode plate according to an example of the present utility model, wherein in Fig. 1(a) the groove is arranged continuously and in Fig. 1(b) the groove is arranged in sections. From the figure, it can be seen that on the surface of the negative electrode plate (i.e., on the surface of the active coating for the negative electrode) several grooves are provided, with the groove in Fig. 1(a) throughout and in Fig. 1(b) is arranged in sections in the width direction of the negative electrode plate. It should be understood that in Fig. 1 only the situation in which the groove is arranged in the width direction of the negative electrode plate is shown, but the groove may also be arranged in the length direction of the negative electrode plate.

[0075] In the present utility model, the depth of the first depression can be 5 µm - 40 µm, for example, 5 µm, 10 µm, 15 µm, 20 µm, 25 µm, 30 µm, 35 µm, or 40 µm. The depth of the first depression has the ordinary meaning in the field and refers to the perpendicular distance from the deepest point in the first depression to the surface of the negative electrode plate. The depth of the first depression can be measured using a conventional method in the field, for example, using a 3D contour measuring device, by measuring and averaging the depths of all first depressions or at least 20 of the first depressions in the surface of the negative electrode active coating.

[0076] In one example, the depth of the first depression is 15 µm - 30 µm.

[0077] In the present utility model, the width of the first recess may be 40 µm - 200 µm, for example 40 µm, 50 µm, 60 µm, 70 µm, 80 µm, 90 µm, 100 µm, 150 µm or 200 µm.

[0078] In one example, the width of the first depression is 60 µm - 100 µm.

[0079] If the first recess is a recessed hole, the width of the first recess is the diameter of the recessed hole. The diameter of the recessed hole has the ordinary meaning in the field. If the shape of the orthogonal projection of the recessed hole onto the surface of the negative electrode plate is a regular circle, the diameter of the recessed hole is equal to the diameter of the regular circle. If the shape of the orthogonal projection of the recessed hole onto the surface of the negative electrode plate is an irregular circle (such as an oval or a curved irregular polyhedron), the diameter of the recessed hole is equal to the diameter of an equivalent circle having the same area as the irregular circle.The diameter of the recessed hole can be measured by a conventional means in the field, for example, a 3D contour gauge, by measuring and averaging the diameters of at least 20 of the recessed holes on the surface of the negative electrode active coating.

[0080] If the first recess is a groove, the width of the first recess is the width of the groove. The width of the groove has the ordinary meaning in the field. The orthogonal projection of the groove onto the surface of the negative electrode plate includes two longer sides, and the width of the groove is the average distance from one longer side to the other longer side in the longitudinal or width direction of the negative electrode plate. Fig. Fig. 2 shows a schematic view for the width of the groove according to an example of the present utility model, wherein in Fig. 2(a) to Fig.2(c) the two longer sides of the groove are straight and in Fig. 2(d) the two longer sides of the groove are curved. In Fig. 2(a) and Fig. 2(b), the two longer sides are arranged parallel to each other. The perpendicular distances from any point on one longer side to the other longer side in the width direction of the negative electrode plate are therefore equal. The width of the groove refers to the perpendicular distance L1 from any point on one longer side to the other longer side in the length or width direction of the negative electrode plate. Fig.2(c), the two longer sides of the groove are straight but not parallel to each other. The distances from any point on one longer side to the other longer side in the width direction are therefore different. The widths of the groove can be averaged, i.e., 50 locations are taken equidistantly on a longer side based on their length (thus, the distances between the locations are equal, so the calculation result can be more accurate), and the widths L1 corresponding to the locations are measured and averaged to determine the width of the groove. Fig.2(d), the two longer sides are curved. The distances of any point on one longer side to the other longer side in the width direction are therefore different. The width of the groove can also be averaged, i.e., 50 locations are randomly selected on a longer side (the reason for the random selection of the 50 locations for measurement is that the two longer sides in Fig. 2(d) are curved and there is no relationship between the two longer sides as in Fig. 2(c)), and the widths L1 corresponding to the locations are measured and averaged to determine the groove width. The groove width can be measured using a conventional means in the field, such as a 3D contour gauge, by measuring and averaging the widths of all the grooves or at least five of the grooves in the surface of the negative electrode active coating.

[0081] In the present utility model, the distance between the first recesses may be 0.5 mm - 5 mm, for example 0.5 mm, 0.6 mm, 0.7 mm, 0.8 mm, 0.9 mm, 1 mm, 1.5 mm, 2 mm, 2.5 mm, 3 mm, 3.5 mm, 4 mm, 4.5 mm or 5 mm.

[0082] In one example, the distance between the first recesses is 0.8 mm - 1.5 mm.

[0083] If the first recess is a recessed hole, the distance between the first recesses is the distance between the recessed holes. The distance between the recessed holes has the ordinary meaning in the field. It is the shortest distance between the edges of two adjacent recessed holes in the surface of the negative electrode plate, which can be measured by a conventional means in the field. For example, using SEM, all or at least 10 groups of adjacent recessed holes in the field of view of the electronic microscope can be selected, their distances measured, and averaged.

[0084] If the first recess is a groove, the distance between the first recesses is the inter-groove distance. It should be understood that there is no inter-groove distance when there is only a single groove in the surface of the negative electrode plate. The inter-groove distance has the ordinary meaning in the field and refers to the average distance between two adjacent longer sides of two adjacent grooves in the longitudinal direction or width direction of the negative electrode plate. Fig. Fig. 3 shows a schematic view for the distance of the groove according to an example of the present utility model, wherein in Fig. 3(a) the two adjacent longer sides are straight and parallel to each other, in Fig. 3(b) the two adjacent longer sides are straight but not parallel, and in Fig. 3(c) the two adjacent longer sides are curved. In Fig.3(a), the two longer sides are straight and parallel to each other. The distances from any point on one of the longer sides to the other longer side in the width direction are therefore equal. The distance between the grooves refers to the distance L2 from any point on one longer side to the other longer side in the width direction. Fig.3(b), the two adjacent longer sides are straight but not parallel to each other. The distances from any point on one longer side to the other longer side in the width direction are therefore different. The distances between the grooves can be averaged, i.e., 50 locations are taken equidistantly on a longer side based on their length (thus, the distances between the locations are equal, so the calculation result can be more accurate), and the widths L2 corresponding to the locations are measured and averaged to determine the distance. Fig.3(c), the two adjacent longer sides are curved. The distances from any point on one longer side to the other longer side in the width direction are therefore different. The distances between the grooves can also be averaged, i.e., 50 locations are randomly selected on a longer side (the reason for the random selection of the 50 locations for measurement is that the two longer sides in Fig. 3(c) are curved and there is no relationship between the two longer sides as in Fig. 3(b)), and the widths L2 corresponding to the locations are measured and averaged to determine the distance. The distance between the grooves can be measured using a conventional means in the field, such as a 3D contour gauge, by measuring and averaging the distances between all the grooves or at least five of the grooves in the surface of the negative electrode active coating.

[0085] In the present utility model, the positive electrode plate may include a positive electrode current collector and the positive electrode active coating on at least one surface of the positive electrode current collector. The length of the positive electrode active coating on a first surface of the positive electrode current collector is greater than the length of the positive electrode active coating on a second surface of the positive electrode current collector. It should be understood that in the coating, a single-sided coating region in which the positive electrode current collector is provided with the positive electrode active coating on only one surface and a double-sided coating region in which the positive electrode current collector is provided with the positive electrode active coating on both surfaces exist on the positive electrode plate.This results in unequal lengths of the positive electrode active coating on the two surfaces of the positive electrode plate. In the present utility model, the surface on which the length of the positive electrode active coating on the surface of the positive electrode current collector is longer is defined as the first surface, and the surface on which the length of the positive electrode active coating is shorter is defined as the second surface. The area where the projections of the positive electrode active coating on the first surface and the positive electrode active coating on the second surface overlap in the thickness direction of the positive electrode plate represents the double-sided coating area, and the area where these projections do not overlap represents the single-sided coating area.Due to the special structure of the wound battery, the first surface is usually facing the winding center of the wound core and the second surface is facing away from it.

[0086] In the present utility model, the surface of the positive electrode active coating is provided with second recesses on the first surface, and the surface of the positive electrode active coating is provided with projections on the second surface. The surface of the positive electrode plate is embossed to form a structure with recesses on one side and projections on the other side.

[0087] The electrolyte solution in the battery is stored in a gap between the wound core and an aluminum-plastic foil, and in gaps between the layers of electrode plates. Storage between the layers is mainly due to slow wetting through the pores of the electrode plates and the capillary effect, and is more difficult and time-consuming than wetting through the gap between the wound core and the aluminum-plastic foil. Therefore, the amount of liquid stored between the inner layers of the electrode plates of the wound core is much smaller than between the outer layers of the electrode plates.By embossing the positive electrode plate and forming the recesses on one side and the protrusions on the other side, more spaces for liquid storage can be provided to shorten the transfer distance of ions, reduce the polarity of the positive and negative electrode plates, and increase the overall charging speed of the battery.

[0088] The inventor also conducted a force analysis of the positive electrode active coatings facing and away from the winding center in the wound core and found that when a first surface facing the winding center and provided with recesses and a second surface facing away from the winding center and provided with projections, not only the structural stability of the positive electrode plate itself is promoted, but also an excellent buffer space for the volume expansion of the negative electrode plate can be created to enable the improvement of the cycle life of the battery. Fig.4 shows a schematic structural view of a wound core according to an example of the present utility model. From the figure, it can be seen that the wound core includes a negative electrode plate 1 and a positive electrode plate 2. The surface of the positive electrode active coating on the first surface is provided with second recesses, and the surface of the positive electrode active coating on the second surface is provided with projections. The first surface faces the winding center of the wound core, and the second surface faces away from it.

[0089] In the present utility model, the shapes of the orthogonal projections of the second recesses and the projections onto the surface of the positive electrode plate are not limited and they may be circular, oval, linear (straight or wavy), polyhedral.

[0090] In the present utility model, the positive electrode plate includes a positive electrode tab welding area, a deposition area, and an exposed area. The exposed area refers to the area not coated with the positive electrode active coating outside the positive electrode tab welding area on the positive electrode current collector. The deposition area includes the double-sided coated area and the single-sided coated area. Fig. Fig. 5 is a schematic structural view of a positive electrode plate according to an example of the present utility model, wherein Fig. 5(a) is a plan view and Fig.5(b) is a sectional view taken in the thickness direction. From the figure, it can be seen that the positive electrode plate includes a positive electrode tab welding area 3, a deposition area 4, and an exposed area 5, wherein the deposition area 4 includes a double-sided coated area 10 and a single-sided coated area 20.

[0091] In one example, the second recesses and the projections are located in the application area.

[0092] In one example, the second recesses and the projections are located in the double-sided coated area.

[0093] In one example, the second recesses and the projections are located in the application area and in the double-sided coated area.

[0094] In the present utility model, the distance of the second recess to an edge of the welding area for the tab of the positive electrode is w1, with 0 mm < w1 ≤ 10 mm, for example 0.1 mm, 0.5 mm, 1 mm, 2 mm, 3 mm, 4 mm, 5 mm, 6 mm, 7 mm, 8 mm, 9 mm or 10 mm.

[0095] In the present utility model, the distance between the second recess and a first edge of the application area is w2, where 2 mm ≤ w2 ≤ 40 mm, for example 2 mm, 3 mm, 4 mm, 5 mm, 6 mm, 7 mm, 8 mm, 9 mm, 10 mm, 11 mm, 12 mm, 13 mm, 14 mm, 15 mm, 16 mm, 17 mm, 18 mm, 19 mm, 20 mm, 25 mm, 30 mm, 35 mm or 40 mm. The first edge is the edge at which the welding area for the tab of the positive electrode is arranged.

[0096] In the present utility model, the distance between the second recess and a second edge of the deposition area is w3, where 2 mm ≤ w3 ≤ 25 mm, for example 2 mm, 3 mm, 4 mm, 5 mm, 6 mm, 7 mm, 8 mm, 9 mm, 10 mm, 11 mm, 12 mm, 13 mm, 14 mm, 15 mm, 16 mm, 17 mm, 18 mm, 19 mm, 20 mm, or 25 mm. The second edge is the edge opposite the edge where the welding area for the positive electrode tab is located.

[0097] In the present utility model, the distance between the second recess and a third edge of the application area is w4, where 0 mm < w4 ≤ 20 mm, for example 0.1 mm, 0.5 mm, 1 mm, 2 mm, 3 mm, 4 mm, 5 mm, 6 mm, 7 mm, 8 mm, 9 mm, 10 mm, 11 mm, 12 mm, 13 mm, 14 mm, 15 mm, 16 mm, 17 mm, 18 mm, 19 mm or 20 mm. The third edge is the edge of the application area that is closer to a starting point for winding.

[0098] In the present utility model, the distance of the second recess to a cutting line between the double-sided coated area and the single-sided coated area is w5, with 0 mm < w5 ≤ 20 mm, for example 0.1 mm, 0.5 mm, 1 mm, 2 mm, 3 mm, 4 mm, 5 mm, 6 mm, 7 mm, 8 mm, 9 mm, 10 mm, 11 mm, 12 mm, 13 mm, 14 mm, 15 mm, 16 mm, 17 mm, 18 mm, 19 mm or 20 mm.

[0099] By controlling w1, w2, w3, w4 and w5, the detachment of powder from the positive electrode plate can be prevented, which is beneficial for improving the cycle life of the battery.

[0100] Fig.6 shows a schematic plan view of a first surface of the positive electrode plate according to an example of the present utility model. From the figure, it can be seen that the first surface is provided with several second recesses 6, where w1 represents the distance of the second recess 6 to the edge of the positive electrode tab welding area 3, w2 represents the distance of the second recess 6 to the first edge of the deposition area 4, w3 represents the distance of the second recess 6 to the second edge of the deposition area 4, w4 represents the distance of the second recess 6 to the third edge of the deposition area 4, and w5 represents the distance of the second recess 6 to the intersection line between the double-sided coated area 10 and the single-sided coated area 20.

[0101] In the present utility model, the depth of the second recess can be 3 µm - 40 µm, for example, 3 µm, 5 µm, 10 µm, 15 µm, 20 µm, 25 µm, 30 µm, 35 µm, or 40 µm. The height of the projection can be 3 µm - 40 µm, for example, 3 µm, 5 µm, 10 µm, 15 µm, 20 µm, 25 µm, 30 µm, 35 µm, or 40 µm.

[0102] In one example, the depth of the second recess is 10 µm - 30 µm. The height of the projection is 10 µm - 30 µm.

[0103] In the present utility model, the depth of the second recess and the height of the protrusion have the ordinary meanings in the field. The depth of the second recess refers to the vertical distance from the deepest point in the second recess to the surface of the positive electrode plate. The height of the protrusion refers to the vertical distance from the highest point of the protrusion to the surface of the positive electrode plate. The depth of the second recess and the height of the protrusion can be measured using a conventional method in the field, for example, using a 3D contour measuring device by selecting at least 20 of the second recesses and 20 of the protrusions on the surface of the positive electrode plate, measuring the depths of the second recesses and the heights of the protrusions, and averaging them to determine the depth of the second recess and the height of the protrusion, respectively.

[0104] In the present utility model, the width of the second recess can be 0.2 mm - 8 mm, for example, 0.2 mm, 0.5 mm, 1 mm, 2 mm, 3 mm, 4 mm, 5 mm, 6 mm, 7 mm, or 8 mm. The width of the projection can be 0.2 mm - 8 mm, for example, 0.2 mm, 0.5 mm, 1 mm, 2 mm, 3 mm, 4 mm, 5 mm, 6 mm, 7 mm, or 8 mm.

[0105] In one example, the width of the second recess is 1 mm - 3 mm. The width of the projection is 1 mm - 3 mm.

[0106] In the present utility model, when the projection shape of the second recess in the thickness direction of the positive electrode plate is a regular circle, the width of the second recess is exactly the diameter of the regular circle. When the projection shape of the second recess in the thickness direction of the positive electrode plate is an irregular circle, the width of the second recess is exactly the equivalent diameter of a circle having the same area as the irregular circle. When the projection shape of the protrusion in the thickness direction of the positive electrode plate is a regular circle, the width of the protrusion is also exactly the diameter of the regular circle.When the projection shape of the protrusion in the thickness direction of the positive electrode plate is an irregular circle, the width of the protrusion is just the equivalent diameter of a circle having the same area as the irregular circle. The width of the second recess and the width of the protrusion can be measured using a conventional method in the field, such as a 3D contour gauge.

[0107] In the present utility model, the distance between the second recesses can be 0.5 mm - 8 mm, for example, 0.5 mm, 1 mm, 2 mm, 3 mm, 4 mm, 5 mm, 6 mm, 7 mm, or 8 mm. The distance between the projections can be 0.5 mm - 8 mm, for example, 0.5 mm, 1 mm, 2 mm, 3 mm, 4 mm, 5 mm, 6 mm, 7 mm, or 8 mm.

[0108] In one example, the distance between the second recesses is 1 mm - 3 mm. The distance between the projections is 1 mm - 3 mm.

[0109] In the present utility model, the distance between the second recesses is the shortest distance between the edges of the orthogonal projections of two adjacent second recesses onto the surface of the positive electrode plate, and the distance between the projections is the shortest distance between the edges of the orthogonal projections of two adjacent projections onto the surface of the positive electrode plate. The distance between the second recesses and the distance between the projections can be measured using a conventional method in the field, such as a 3D contour measuring device, by selecting at least 10 groups of adjacent second recesses and projections on the surface of the positive electrode plate, measuring their distances, and averaging them.

[0110] In the present utility model, the positive electrode active coating may also include a positive electrode conductive agent and a positive electrode binder, and the negative electrode active coating may also include a negative electrode conductive agent and a negative electrode binder. The positive electrode conductive agent and the negative electrode conductive agent may be conventional conductive agents. The positive electrode binder and the negative electrode binder may be conventional binders.

[0111] It should be noted that the terms “first” and “second” are used solely to distinguish between different substances or uses, without indicating the difference in order.

[0112] The present utility model is explained in more detail below in connection with the exemplary embodiments. The described exemplary embodiments of the present utility model do not represent all, but only a portion of the exemplary embodiments of the present utility model. Based on the exemplary embodiment of the present utility model, the other exemplary embodiments that can be obtained by a person skilled in the art without inventive step are intended to fall within the scope of protection of the present utility model.

[0113] Unless specifically stated, all materials used in the following examples are commercially available and analytically pure.

[0114] The following examples are used to describe the lithium ion secondary battery of the present utility model. Example 1

[0115] A battery was manufactured using the following procedure: (1) Preparation of a positive electrode plate lithium cobalt oxide (wherein M 1 Al), a solid electrolyte (lithium-aluminium-titanium-phosphorus oxide with the chemical formula Li 1.3 Al 0.3 Ti 1.7(PO4)3 with an average particle size of 1.5 μm), a positive electrode electrically conductive agent (electrically conductive carbon black), and a positive electrode binder (polyvinylidene fluoride) were mixed in a mass ratio of 96.039:0.961:1:2. N-methylpyrrolidone (NMP) was added and stirred homogeneously to formulate a positive electrode slurry. This positive electrode slurry was coated on the first and second surfaces of an aluminum foil (with the coating length of the positive electrode slurry on the first surface of the aluminum foil being longer than that on the second surface), baked, and rolled to obtain a positive electrode plate with a thickness of 100 μm.On the deposition area of ​​the positive electrode plate, a positive electrode tab welding area with a fixed dimension of 20 mm in the width direction of the positive electrode plate was provided. A nickel tab was laser-welded into the positive electrode tab welding area. A double-sided coated area was embossed again by rolling from the first surface to the second surface, avoiding the positive electrode tab welding area, to form the second recesses (on the first surface) and the projections (on the second surface). The shapes of the orthogonal projections of the second recesses and the projections onto the surface of the positive electrode plate are circular.

[0116] The mass content c1 of the Al element in the active coating for the positive electrode was 8273 ppm, the mass content c3 of the characteristic element (Ti) in the active coating for the positive electrode was 1578 ppm, the mass content c4 of the Co element in the active coating for the positive electrode was 580215 ppm, c3 / c4 0.0027, c3 × c1 1.31 × 10 -5 , the width of the second depression was 2 mm, its depth was 20 µm, and the distance between the second depressions was 2 mm. w1 was 7 mm, w2 27 mm, w3 15 mm, w4 7 mm, w5 7 mm. (2) Preparation of a negative electrode plate Artificial graphite (as secondary particles), a silicon-carbon material (in which the number of primary spherical particles accounted for 0.55 of the total number of primary and secondary spherical particles, the average particle size of the primary spherical particles was 4.1 μm, and the mass content of Si element in the silicon-carbon material was 40%), a negative electrode electrically conductive agent (carbon nanotubes), a negative electrode dispersant (lithium carboxymethylcellulose), and a negative electrode binder (polyacrylic acid) were mixed in a mass ratio of 77:20:0.4:0.1:2.5, and deionized water was added thereto to formulate a negative electrode slurry.This negative electrode slurry was applied to two surfaces of a carbon-coated copper foil, baked, and rolled to obtain a negative electrode plate with a thickness of 110 µm. Laser cutting was used to create the first recesses (grooves) on the surface of the negative electrode plate.

[0117] The mass content c2 of the Si element in the active coating for the negative electrode was 8%, the width of the groove was 79.6 µm, the depth thereof was 20.2 µm and the distance between the grooves was 1.3 mm. (3) Preparation of an electrolyte solution

[0118] In a glove box (H2O < 0.01 ppm, O2 < 0.01 ppm, Ar atmosphere), ethylene carbonate, propylene carbonate, and diethyl carbonate were mixed in a weight ratio of 1:3:6 to obtain an organic solvent. Then, a mixed solvent was prepared by adding a carboxylic acid ester compound (PP) in an amount of 45% based on the total mass of the electrolytic solution. In this mixed solvent, 15% of fluoroethylene carbonate, 7.5% of VC (where c5 was 7.5%), and 12.5% ​​of lithium hexafluorophosphate, each based on the total mass of the electrolytic solution, were dissolved to obtain the electrolytic solution. (4) Manufacturing a separator

[0119] 1,3,5-Triazine-2,4,6-triamine was ground, homogeneously mixed with styrene-butadiene rubber and lithium polyacrylate in a mass ratio of 63:30:7, and added with NMP to obtain an organic coating slurry. This organic coating slurry was coated on one surface of a polyethylene film to form an organic coating with a thickness h of 1.3 µm and dried. A PMMA adhesive layer was coated on the other surface of the polyethylene film, and a PVDF+PMMA adhesive layer (in a mass ratio of PVDF and PMMA of 7:3) was coated on the outer surface of the organic coating to obtain a separator. The mass content of the N element in the organic coating was 28%. (5) Manufacture of the battery

[0120] The positive electrode plate prepared in step (1), the separator prepared in step (4), and the negative electrode plate prepared in step (2) were wound to obtain a wound core with the organic coating facing the positive electrode plate. A battery was obtained after packaging, baking, liquid filling, formation, secondary packaging, sorting, and OCV. Example 2

[0121] A battery was manufactured using the following procedure: (1) Preparation of a positive electrode plate lithium cobalt oxide (wherein M 1 Al), a solid electrolyte (lithium-aluminium-titanium-phosphorus oxide with the chemical formula Li 1.3 Al 0.3 Ti 1.7(PO4)3 with an average particle size of 1.2 μm), a positive electrode conductive agent (electroconductive carbon black), and a positive electrode binder (polyvinylene fluoride) were mixed in a mass ratio of 96.042:0.958:1:2. N-methylpyrrolidone (NMP) was added and stirred homogeneously to formulate a positive electrode slurry. This positive electrode slurry was coated on the first and second surfaces of an aluminum foil (with the coating length of the positive electrode slurry on the first surface of the aluminum foil being longer than that on the second surface), baked, and rolled to obtain a positive electrode plate with a thickness of 100 μm.On the deposition area of ​​the positive electrode plate, a positive electrode tab welding area with a fixed dimension of 15 mm in the width direction of the positive electrode plate was provided. A nickel tab was laser welded into the positive electrode tab welding area. A double-sided coated area was embossed again by rolling from the first surface to the second surface, avoiding the positive electrode tab welding area, to form the second recesses (on the first surface) and the projections (on the second surface). The shapes of the orthogonal projections of the second recesses and the projections onto the surface of the positive electrode plate are circular.

[0122] The mass content c1 of the Al element in the active coating for the positive electrode was 7126 ppm, the mass content c3 of the characteristic element (Ti) in the active coating for the positive electrode was 1991 ppm, the mass content c4 of the Co element in the active coating for the positive electrode was 564282 ppm, c3 / c4 0.0035, c3 × c1 1.42 × 10 -5 , the width of the second depression was 1 mm, its depth was 10 µm, and the distance between the second depressions was 1 mm. w1 was 5 mm, w2 20 mm, w3 10 mm, w4 5 mm, and w5 5 mm.

[0123] (2) Preparation of a negative electrode plate Artificial graphite (as secondary particles), a silicon-carbon material (in which the number of primary spherical particles accounted for 0.32 of the total number of primary and secondary spherical particles, the average particle size of the primary spherical particles was 3 μm, and the mass content of Si element in the silicon-carbon material was 40%), a negative electrode electrically conductive agent (carbon nanotubes), a negative electrode dispersant (lithium carboxymethylcellulose), and a negative electrode binder (polyacrylic acid) were mixed in a mass ratio of 77:20:0.4:0.1:2.5, and deionized water was added thereto to formulate a negative electrode slurry.This negative electrode slurry was applied to two surfaces of a carbon-coated copper foil, baked, and rolled to obtain a negative electrode plate with a thickness of 110 µm. Laser cutting was used to create the first recesses (grooves) on the surface of the negative electrode plate.

[0124] The mass content c2 of the Si element in the active coating for the negative electrode was 8%, the width of the groove was 60.1 µm, the depth thereof was 15.4 µm and the distance between the grooves was 0.8 mm. (3) Preparation of an electrolyte solution

[0125] In a glove box (H2O < 0.01 ppm, O2 < 0.01 ppm, Ar atmosphere), ethylene carbonate, propylene carbonate, and diethyl carbonate were mixed in a weight ratio of 1:3:6 to obtain an organic solvent. Then, a mixed solvent was prepared by adding a carboxylic acid ester compound (PP) in an amount of 20% based on the total mass of the electrolytic solution. In this mixed solvent, 15% of fluoroethylene carbonate, 10% of VC (where c5 was 10%), and 12.5% ​​of lithium hexafluorophosphate, each based on the total mass of the electrolytic solution, were dissolved to obtain the electrolytic solution. (4) Manufacturing a separator

[0126] 1,3,5-Triazine-2,4,6-triamine was ground, homogeneously mixed with styrene-butadiene rubber and lithium polyacrylate in a mass ratio of 40:50:10, and added with NMP to obtain an organic coating slurry. This organic coating slurry was coated on one surface of a polyethylene film to form an organic coating with a thickness h of 1 µm and dried. A PMMA adhesive layer was coated on the other surface of the polyethylene film, and a PVDF+PMMA adhesive layer (with a PVDF and PMMA mass ratio of 7:3) was coated on the outer surface of the organic coating to obtain a separator. The mass content of the N element in the organic coating was 15%. (5) Manufacture of the battery

[0127] The positive electrode plate prepared in step (1), the separator prepared in step (4), and the negative electrode plate prepared in step (2) were wound to obtain a wound core with the organic coating facing the positive electrode plate. A battery was obtained after packaging, baking, liquid filling, formation, secondary packaging, sorting, and OCV. Example 3

[0128] A battery was manufactured using the following procedure: (1) Preparation of a positive electrode plate lithium cobalt oxide (wherein M 1 Al), a solid electrolyte (lithium-aluminium-titanium-phosphorus oxide with the chemical formula Li 1.3 Al 0.3 Ti 1.7(PO4)3 with an average particle size of 1.7 μm), a positive electrode conductive agent (electroconductive carbon black), and a positive electrode binder (polyvinylene fluoride) were mixed in a mass ratio of 96.033:0.967:1:2. N-methylpyrrolidone (NMP) was added and stirred homogeneously to formulate a positive electrode slurry. This positive electrode slurry was coated on the first and second surfaces of an aluminum foil (with the coating length of the positive electrode slurry on the first surface of the aluminum foil being longer than that on the second surface), baked, and rolled to obtain a positive electrode plate with a thickness of 100 μm.On the deposition area of ​​the positive electrode plate, a positive electrode tab welding area with a fixed dimension of 25 mm in the width direction of the positive electrode plate was provided. A nickel tab was laser-welded into the positive electrode tab welding area. A double-sided coated area was embossed again by rolling from the first surface to the second surface, avoiding the positive electrode tab welding area, to form the second recesses (on the first surface) and the projections (on the second surface). The shapes of the orthogonal projections of the second recesses and the projections onto the surface of the positive electrode plate are circular.

[0129] The mass content c1 of the Al element in the active coating for the positive electrode was 9986 ppm, the mass content c3 of the characteristic element (Ti) in the active coating for the positive electrode was 936 ppm, the mass content c4 of the Co element in the active coating for the positive electrode was 618542 ppm, c3 / c4 0.0015, c3 × c1 9.35 × 10 -6 , the width of the second depression was 3 mm, its depth was 30 µm, and the distance between the second depressions was 3 mm. w1 was 9 mm, w2 34 mm, w3 20 mm, w4 10 mm, and w5 10 mm. (2) Preparation of a negative electrode plate Artificial graphite (as secondary particles), a silicon-carbon material (in which the number of primary spherical particles accounted for 0.79 of the total number of primary and secondary spherical particles, the average particle size of the primary spherical particles was 4.9 μm, and the mass content of Si element in the silicon-carbon material was 40%), a negative electrode electrically conductive agent (carbon nanotubes), a negative electrode dispersant (lithium carboxymethylcellulose), and a negative electrode binder (polyacrylic acid) were mixed in a mass ratio of 77:20:0.4:0.1:2.5, and deionized water was added thereto to formulate a negative electrode slurry.This negative electrode slurry was applied to two surfaces of a carbon-coated copper foil, baked, and rolled to obtain a negative electrode plate with a thickness of 110 µm. Laser cutting was used to create the first recesses (grooves) on the surface of the negative electrode plate.

[0130] The mass content c2 of the Si element in the active coating for the negative electrode was 8%, the width of the groove was 99.2 µm, the depth thereof was 29.5 µm and the distance between the grooves was 1.5 mm. (3) Preparation of an electrolyte solution

[0131] In a glove box (H2O < 0.01 ppm, O2 < 0.01 ppm, Ar atmosphere), ethylene carbonate, propylene carbonate, and diethyl carbonate were mixed in a weight ratio of 1:3:6 to obtain an organic solvent. Then, a mixed solvent was prepared by adding a carboxylic acid ester compound (PP) in an amount of 65% based on the total mass of the electrolytic solution. In this mixed solvent, 15% of fluoroethylene carbonate, 5% of VC (where c5 was 5%), and 12.5% ​​of lithium hexafluorophosphate were dissolved, each based on the total mass of the electrolytic solution, to obtain the electrolytic solution. (4) Manufacturing a separator

[0132] 1,3,5-Triazine-2,4,6-triamine was ground, homogeneously mixed with styrene-butadiene rubber and lithium polyacrylate in a mass ratio of 80:15:5, and added with NMP to obtain an organic coating slurry. This organic coating slurry was coated on one surface of a polyethylene film to form an organic coating with a thickness h of 2 µm and dried. A PMMA adhesive layer was coated on the other surface of the polyethylene film, and a PVDF+PMMA adhesive layer (with a mass ratio of PVDF and PMMA of 7:3) was coated on the outer surface of the organic coating to obtain a separator. The mass content of the N element in the organic coating was 35%. (5) Manufacture of the battery

[0133] The positive electrode plate prepared in step (1), the separator prepared in step (4), and the negative electrode plate prepared in step (2) were wound to obtain a wound core with the organic coating facing the positive electrode plate. A battery was obtained after packaging, baking, liquid filling, formation, secondary packaging, sorting, and OCV. Examples of Group 4

[0134] This group of examples is used to research the influence of changing the mass content c1 of the Al element in the active coating for the positive electrode.

[0135] This group of examples was carried out as in Example 1, but with c1 modified as follows: For Example 4a, c1 was 6852 ppm, where c3 × c1 was 1.08 × 10 -5 fraud. For Example 4b, c1 was 14874 ppm, where c3 × c1 was 2.35 × 10 -5 fraud. Examples of Group 5

[0136] This group of examples is used to research the influence of changing the type of solid electrolyte.

[0137] This group of examples was carried out as in Example 1, but with the following modified solid electrolytes: In Example 5a, lithium aluminum titanium phosphorus oxide was replaced by lithium lanthanum zirconium tantalum oxide with the chemical formula Li 6.5 La3Zr 1.5 Ta 0.5 O 12 and in addition, the formulation of the positive electrode slurry was adjusted so that the mass ratio of the lithium cobalt oxide, the solid electrolyte, the electrically conductive agent for the positive electrode and the binder for the positive electrode was 96.047 : 0.953 : 1 : 2, wherein the mass content c3 of the characteristic element (Zr) was 1676, in order to achieve a mass content c3 of the characteristic element similar to Example 1.

[0138] In Example 5b, lithium aluminum titanium phosphorus oxide was replaced by lithium lanthanum titanium oxide with the chemical formula Li 30.3 La 0.567 TiO3, and also the formulation of the positive electrode slurry was adjusted so that the mass ratio of lithium cobalt oxide, solid electrolyte, positive electrode electrically conductive agent and positive electrode binder was 96.032:0.968:1:2, with the mass content c3 of the characteristic element (La) being 1628. Examples of Group 6

[0139] This group of examples is used to investigate the influence of changing the mass content c2 of the Si element in the active coating for the negative electrode.

[0140] This group of examples was carried out as in Example 1, but with c2 adjusted as follows by the mass contents of the graphite material and the silicon-carbon material in the negative electrode slurry: In Example 6a, the artificial graphite, the silicon-carbon material, the electrically conductive agent for the negative electrode, the dispersant for the negative electrode and the binder for the negative electrode were mixed in a mass ratio of 87:10:0.4:0.1:2.5, where c2 was 4%. In Example 6b, the artificial graphite, the silicon-carbon material, the electrically conductive agent for the negative electrode, the dispersant for the negative electrode, and the binder for the negative electrode were mixed in a mass ratio of 67:30:0.4:0.1:2.5, where c2 was 12%. In Example 6c, the artificial graphite, the silicon-carbon material, the electrically conductive agent for the negative electrode, the dispersant for the negative electrode, and the binder for the negative electrode were mixed in a mass ratio of 93:4:0.4:0.1:2.5, where c2 was 1.6%. In Example 6d, the artificial graphite, the silicon-carbon material, the electrically conductive agent for the negative electrode, the dispersant for the negative electrode, and the binder for the negative electrode were mixed in a mass ratio of 52:45:0.4:0.1:2.5, where c2 was 18%. Examples of Group 7

[0141] This group of examples is used to investigate the influence of changing the mass content c3 of the characteristic element in the active coating for the positive electrode.

[0142] This group of examples was carried out as in Example 1, but with c3 adjusted by the contents of the solid electrolyte in the slurry for the positive electrode as follows: In Example 7a, the formulation of the positive electrode slurry was adjusted so that the mass ratio of the lithium cobalt oxide, the solid electrolyte, the electrically conductive agent for the positive electrode and the binder for the positive electrode was 96.031 : 0.969 : 1 : 2, where c3 was 605 ppm, c3 / c4 was 0.001 and c3 × c1 was 5.01 × 10 -6 fraud. In Example 7b, the formulation of the positive electrode slurry was adjusted so that the mass ratio of the lithium cobalt oxide, the solid electrolyte, the positive electrode electrically conductive agent, and the positive electrode binder was 96.05:0.95:1:2, where c3 was 2967 ppm, c3 / c4 was 0.0051, and c3 × c1 was 2.45 × 10 -5 fraud. Examples of Group 8

[0143] This group of examples is used to research the influence of changing the product of the mass content c3 of the characteristic element in the active coating for the positive electrode and the mass content c1 of the Al element in the active coating for the positive electrode c3 × c1.

[0144] This group of examples was performed as in Example 2 and Example 3, but with c3 × c1 set by c1 as follows: Example 8a was carried out according to Example 2, but with c1 of 9875 ppm and c3 × c1 of 1.97 × 10 -5 . Example 8b was carried out according to Example 3, but with c1 of 7233 ppm and c3 × c1 of 6.77 × 10 -6 . Example 9

[0145] This example is used to research the influence of whether the second recesses on the surface of the positive electrode active coating are located on the first surface and whether the protrusions on the surface of the positive electrode active coating are located on the second surface.

[0146] This example was carried out as in Example 1 except that the embossing was carried out from the second surface after the first surface, that is, the surface of the active coating for the positive electrode on the second surface was provided with the second depressions and the surface of the active coating for the positive electrode on the first surface was provided with the projections. Example 10

[0147] This example is used to investigate the influence of the absence of the second recesses and protrusions on the surface of the active coating for the positive electrode.

[0148] This example was carried out as in Example 1, but without embossing. Example 11

[0149] This example is used to research the influence of whether the one-sided coated area is provided with the second depressions.

[0150] This example was carried out as in Example 1, except that embossing was carried out in the single-sided coated area and the double-sided coated area, avoiding the welding area for the positive electrode tab. Examples of Group 12

[0151] This group of examples is used to research the influence of changing w1, w2, w3, w4 and w5.

[0152] This group of examples was carried out as in Example 1, but with w1, w2, w3, w4 and w5 modified as follows: In Example 12a, w1 was 0.5 mm, w2 was 2 mm, w3 was 2 mm, w4 was 0.5 mm, and w5 was 0.5 mm. In Example 12b, w1 was 10 mm, w2 was 40 mm, w3 was 25 mm, w4 was 20 mm, and w5 was 20 mm. Examples of Group 13

[0153] This group of examples is used to research the influence of changing the average particle size of the primary spherical particles.

[0154] This group of examples was carried out as in Example 1, but with the following changes: In Example 13a, the average particle size of the primary spherical particles was 1.1 µm. In Example 13b, the average particle size of the primary spherical particles was 6 µm. Examples of Group 14

[0155] This group of examples is used to research the influence of changing the proportion of the number of primary spherical particles in the total number of primary and secondary spherical particles.

[0156] This group of examples was carried out as in Example 1, but with the following proportions of the number of primary spherical particles changed: In Example 14a, the silicon-carbon material consisted entirely of the primary spherical particles, that is, the proportion of the number of the primary spherical particles in the total number of the primary and secondary spherical particles was 1. In Example 14b, the proportion of the number of primary spherical particles in the total number of primary and secondary spherical particles was 0.11. Example 15

[0157] This example was carried out as in Example 1, except that the artificial graphite was primary particles with an average particle size of 6.1 µm. Example 16

[0158] This example is used to research the influence of changing the type of first wells.

[0159] This example was carried out as in Example 1, except that recessed holes were laser-cut in the surface of the negative electrode plate, the width of the recessed hole being 85.2 µm, the depth thereof being 20.1 µm, and the distance between the recessed holes being 0.5 mm. Example 17

[0160] This example is used to investigate the influence of changing the mass content of the carboxylic acid ester compound in the electrolyte solution.

[0161] This example was carried out as in Example 1, but with a PP content of 10%. Examples of Group 18

[0162] This group of examples is used to investigate the influence of changing the mass content c5 of vinylene carbonate in the electrolyte solution.

[0163] This group of examples was carried out as in Example 1, but with c5 adjusted as follows by the amount of vinylene carbonate used in the electrolyte solution: In Example 18a, no vinylene carbonate was added to the electrolyte solution, so c5 was equal to 0. For example 18b, c5 was 0.05%. In Example 18c, c5 was 15%. Example 19

[0164] This example is used to research the influence of changing the organic coating.

[0165] This example was carried out as in Example 1, except that the organic coating was replaced by a ceramic coating of boehmite of the same thickness. Example 20

[0166] This example is used to investigate the influence of whether the organic coating is aligned with the positive electrode plate.

[0167] This example was performed as in Example 1, except that the organic coating was aligned with the negative electrode plate. Examples of Group 21

[0168] This group of examples is used to investigate the influence of changing the mass content of the N element in the organic coating.

[0169] This group of examples was carried out as in Example 1, but with the mass contents of the N element in the organic coating adjusted by the composition of the substance(s) in the organic coating as follows: In Example 21a, 1,3,5-triazine-2,4,6-triamine was replaced by polyacrylonitrile of the same mass, the mass content of the N element in the organic coating being 10.5%.

[0170] In Example 21b, the mass ratio of 1,3,5-triazine-2,4,6-triamine, styrene-butadiene rubber, and lithium polyacrylate was 94:5:1, with the mass content of N element in the organic coating being 55%. Examples of Group 22

[0171] This group of examples is used to research the influence of changing the thickness h of the organic coating.

[0172] This group of examples was carried out as in Example 1, but with h modified as follows: In Example 22a, h was 0.5 µm. In Example 22b, h was 4 µm.

[0173] The examples described above satisfy the following conditions: the average particle size of the first particles of lithium cobalt oxide is 0.3 µm - 7 µm and the average particle size of the second particles of lithium cobalt oxide is 7.5 µm - 40 µm.

[0174] The above-described examples, except for Example 14a, satisfy the condition that the average particle size of the secondary spherical particles of the silicon-carbon material is 3 µm–20 µm. The above-described examples, except for Example 15, satisfy the condition that the average particle size of the secondary particles of the graphite material is 6 µm–20 µm. Comparison example 1

[0175] This example was carried out as in Example 1, except that no solid electrolyte was added to the positive electrode plate, i.e., the lithium cobalt oxide, the electrically conductive agent for the positive electrode, and the binder for the positive electrode were mixed in a mass ratio of 97:1:2, added with NMP, and formulated into a slurry for the positive electrode. Comparative examples of Group 2

[0176] This group of comparative examples is used to research the influence of changing the mass content c1 of the Al element in the active coating for the positive electrode.

[0177] This group of comparative examples was carried out as in Example 1, but with c1 modified as follows: In Comparative Example 2a, c1 was 6354 ppm. In Comparative Example 2b, c1 was 17895 ppm. Comparison example 3

[0178] This comparative example is used to research the influence of changing the mass content c2 of the Si element in the active coating for the negative electrode.

[0179] This was carried out as in Example 1, but with mass contents c2 adjusted as follows by the mass contents of the graphite material and the silicon-carbon material in the negative electrode slurry: The artificial graphite, the silicon-carbon material, the electrically conductive agent for the negative electrode, the dispersant for the negative electrode and the binder for the negative electrode were mixed in a mass ratio of 37:60:0.4:0.1:2.5, where c2 was 24%. Comparison example 4

[0180] This comparative example is used to investigate the influence of the absence of the carboxylic acid ester compound in the electrolyte solution.

[0181] This was carried out as in Example 1, but without PP in the electrolyte solution. Example of tests(1) Volumetric energy density test

[0182] The batteries manufactured in the examples and comparative examples were subjected to the volumetric energy density test using the following test method: The battery was charged with a current of 0.2 C up to 4.5 V, charged at a constant voltage until a current drop of 0.02 C, and discharged with a current of 0.2 C up to 3.0 V. The discharge energy was denoted as E. The thickness, width, and length of the battery were measured and multiplied to obtain the battery volume, denoted as V. The volumetric energy density was calculated using the equation VED = E / V. The results are recorded in Table 1. (2) Low temperature discharge test

[0183] The batteries manufactured in the examples and comparative examples were subjected to the low-temperature discharge test using the following test method: The battery was charged at room temperature (25°C) with a constant current of 0.2 C and a constant voltage until finally at 4.5 V and 0.02 C, allowed to stand for 5 minutes, and discharged at 0.2 C to 3.0 V. The discharge capacity C1 was recorded. The battery was again fully charged at room temperature at 0.2 C with a constant current and a constant voltage until finally at 4.5 V and 0.02 C. The fully charged battery was placed in a thermostat at -20°C, allowed to stand for 2 hours, and then discharged at 0.2 C to 3.0 V. The discharge capacity C2 was recorded. C2 / C1 represented the capacity retention rate when discharged at 0.2 C at a low temperature of -20°C. The results are summarized in Table 1. (3) Test for cycles at a high temperature of 45°C

[0184] The batteries manufactured in the examples and comparative examples were subjected to the test for cycling at a high temperature of 45°C using the following test method: The battery was left to stand in a thermostatic chamber at 45°C for 2 hours, charged at 3°C ​​with a constant current up to 4.2 V, then charged at a constant current of 2°C and a constant voltage until finally at 4.5 V and 0.05°C, and left to stand for 10 minutes. The battery was then discharged at 0.7°C to 3.0 V. The cycles were repeated 500 times. The discharge capacity of the fully charged battery after the 500th cycle was measured, which was designated as C1. The discharge capacity of the battery after the first full charge was designated as C0. C1 / C0 represented the retention rate for the capacity after the 500th cycle. The results are summarized in Table 1. (4) Test for storage at high temperature

[0185] The batteries manufactured in the examples and comparative examples were subjected to the high temperature storage test using the following test method: The battery was charged at room temperature (25°C) with a constant current of 0.2 C and a constant voltage until finally charged at 4.5 V and 0.02 C. The thickness h1 of the fully charged battery was measured using a 600 ppg thickness gauge, and the battery was allowed to stand still for 6 hours at 85°C ± 2°C. Once the battery was removed, the thickness h2 of the battery was measured. (h2-h1) / h1 represented the thickness expansion. The results are summarized in Table 1. Table 1 Energy density (Wh / L) Low temperature discharge capacity retention rate (%) Cyclic retention rate for capacity at high temperature (%) Thickness expansion (%) Example 1 807 85,5 85,5 3,3 Example 2 813 85,8 84,5 4,5 Example 3 798 84,6 85,9 3,3 Example 4a 815 85,1 83,6 3,5 Example 4b 798 85,3 86,1 3,2 Example 5a 810 85,8 85,4 4,5 Example 5b 807 84,2 85,6 3,1 Example 6a 780 90,1 88,5 2,7 Example 6b 810 80,4 81,9 4,8 Example 6c 750 91,3 89,8 2,5 Example 6d 825 76,4 78,3 5,6 Example 7a 806 78,5 85,3 3,1 Example 7b 806 86,5 85,5 5,3 Example 8a 807 84,8 85,4 4,6 Example 8b 805 83, 6 85,0 3,5 Example 9 807 85, 1 83,3 3,6 Example 10 806 83, 9 81,5 3,5 Example 11 807 85,2 83,3 3,5 Example 12a 806 85,3 83, 9 3,4 Example 12b 807 84,5 83, 9 3,5 Example 13a 812 85, 9 83,5 4,3 Example 13b 803 84, 9 85,7 3,1 Example 14a 816 86,1 82,5 6,3 Example 14b 797 84,5 85,5 3,2 Example 15 801 85,8 84,3 3,6 Example 16 806 85, 9 85, 1 4,8 Example 17 806 83,5 84,5 3,3 Example 18a 807 81,5 84, 1 3 Example 18b 807 83,8 84, 9 3 Example 18c 806 85,7 83, 9 4,5 Example 19 807 85, 6 80,5 3 Example 20 806 85, 6 80, 9 3,5 Example 21a 809 85, 6 84, 1 3,2 Example 21b 805 85, 1 85, 9 3, 9 Example 22a 815 85,8 83, 6 3 Example 22b 795 84,7 85, 9 4,2 Comparison example 1 809 75,5 85 3 Comparison example 2a 815 85, 1 79, 6 3,5 Comparison example 2b 790 85,3 86,1 3,2 Comparison example 3 835 73,4 75,3 8,3 Comparison example 4 807 80,5 83,8 3,7

[0186] It can be seen from Table 1 that the battery of the present utility model can exhibit high energy density, excellent cycle stability, good low-temperature discharge and high-temperature storage properties simultaneously compared with the comparative examples.

[0187] The preferred embodiments of the present utility model have been described in detail above, but the present utility model is not intended to be limited thereto. Within the scope of the technical concepts of the present utility model, simple modifications of the technical solutions may be made, including combinations of individual technical features in other suitable ways, which shall also be considered as the disclosure of the present utility model and included within the scope of protection of the present utility model. Summary

[0188] The present utility model relates to the technical field of batteries, and more particularly to a lithium-ion secondary battery. The battery comprises a positive electrode plate, a negative electrode plate, and an electrolyte solution. The cut-off voltage of the lithium-ion secondary battery is ≥ 4.5 V. The positive electrode plate comprises a positive electrode active coating containing a positive electrode active material and a solid electrolyte. The positive electrode active material comprises a lithium cobalt oxide containing Al element, and the mass content c1 of the Al element in the positive electrode active coating is 6800 ppm - 15000 ppm. The solid electrolyte comprises at least one compound of lithium aluminum titanium phosphorus oxide, lithium lanthanum zirconium tantalum oxide, and lithium lanthanum titanium oxide. The negative electrode plate comprises a negative electrode active coating containing a silicon carbon material.The mass content c2 of the Si element in the active coating for the negative electrode is 1.5%-20%. The electrolyte solution comprises a carboxylic acid ester compound. The battery of the present utility model can exhibit both high energy density and excellent cycle stability and low-temperature discharge characteristics. QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited non-patent literature

[0000] GB / T 30902-2014 [0015, 0033] Binder for the positive electrode 96.047 : 0.953 : 1 : 2

[0137]

Claims

[1] Lithium-ion secondary battery, characterized by that the lithium-ion secondary battery comprises a positive electrode plate, a negative electrode plate and an electrolyte solution, wherein the final charging voltage of the lithium-ion secondary battery is ≥ 4.5 V, wherein the positive electrode plate comprises a positive electrode active coating containing a positive electrode active material and a solid electrolyte, wherein the positive electrode active material comprises a lithium cobalt oxide containing Al element, wherein the mass content c1 of the Al element in the positive electrode active coating is 6800 ppm - 15000 ppm, wherein the solid electrolyte comprises at least one compound of lithium aluminum titanium phosphorus oxide, lithium lanthanum zirconium tantalum oxide, and lithium lanthanum titanium oxide, wherein the negative electrode plate comprises a negative electrode active coating comprising a negative electrode active material containing a silicon-carbon material, wherein the mass content c2 of the Si element in the negative electrode active coating is 1.5% - 20%, and wherein the electrolyte solution comprises a solvent containing a carboxylic acid ester compound. [2] Lithium ion secondary battery according to claim 1, characterized by that the mass content c1 of the Al element in the active coating for the positive electrode is 7100 ppm - 10000 ppm, and / or the mass content c2 of the Si element in the active coating for the negative electrode is 4% - 12%, and / or the mass content of the carboxylic acid ester compound in the electrolyte solution is 10% - 80%, preferably 20% - 65%, and / or the carboxylic acid ester compound comprises at least one of the following solvents, which are substituted or unsubstituted with fluorine: ethyl acetate, propyl acetate, n-butyl acetate, isobutyl acetate, n-pentyl acetate, isopentyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate and ethyl n-butyrate. [3] Lithium ion secondary battery according to claim 1 or 2, characterized by that the solid electrolyte contains a characteristic element comprising at least one of Ti, Zr, La and Ta, wherein preferably the ratio of the mass content c3 of the characteristic element in the positive electrode active coating to the mass content c4 of the Co element in the positive electrode active coating is 0.001 - 0.0055, more preferably 0.0015 - 0.0035, wherein preferably the mass content c3 of the characteristic element in the active coating for the positive electrode is 600 ppm - 3000 ppm, more preferably 900 ppm - 2000 ppm, wherein preferably the mass content c4 of the Co element in the active coating for the positive electrode is 400,000 ppm - 750,000 ppm, more preferably 500,000 ppm - 650,000 ppm, and wherein preferably the average particle size of the solid electrolyte is 500 nm - 3 µm, more preferably 1 µm - 2 µm. [4] Lithium ion secondary battery according to claim 1 or 2, characterized by that the electrolyte solution also comprises a vinylene carbonate, and wherein preferably the mass content c5 of vinylene carbonate in the electrolyte solution is 0.01% - 15%. [5] Lithium ion secondary battery according to claim 1 or 2, characterized bythat the solid electrolyte contains a characteristic element comprising at least one element of Ti, Zr, La and Ta, wherein preferably the mass content c3 of the characteristic element in the active coating for the positive electrode and the mass content c1 of the Al element in the active coating for the positive electrode are 5 × 10 -6 ≤ c3 × c1 ≤ 2.5 × 10 -5 , preferably 9.3 × 10 -6 ≤ c3 × c1 ≤ 1.5 × 10 -5 , applies. [6] Lithium ion secondary battery according to claim 1 or 2, characterized by that the lithium-ion secondary battery also comprises a separator with an organic coating, wherein the organic coating comprises polymer particles containing at least one of the groups of cyano, isocyano, isocyanate and triazinyl, wherein preferably the polymer particles contain N element and the mass content of the N element in the organic coating is 10.5% - 55%, more preferably 15% - 35%, wherein preferably the organic coating faces the positive electrode plate, wherein preferably the polymer particles comprise at least one of polyacrylonitrile, nitrile rubber, 1,3,5-triazine-2,4,6-triamine, cyanuric acid, melamine, and melamine trithiocyanurate, and wherein preferably the thickness h of the organic coating is 0.5 µm - 4 µm. [7] Lithium ion secondary battery according to claim 1 or 2, characterized by that silicon-carbon material comprises primary spherical particles, and / or the mass content of the Si element in the silicon-carbon material is 30% - 80%, and / or the active material for the negative electrode also comprises a graphite material. [8] Lithium ion secondary battery according to claim 1 or 2, characterized by that the outer surface of the active coating for the negative electrode is provided with first depressions, wherein the depth of the first depressions is preferably 5 µm - 40 µm, wherein preferably the width of the first recesses is 40 µm - 200 µm, and wherein preferably the distance between the first recesses is 0.5 mm - 5 mm. [9] Lithium ion secondary battery according to claim 1 or 2, characterized bythat the positive electrode plate comprises a positive electrode current collector and the positive electrode active coating on at least one surface of the positive electrode current collector, wherein the length of the positive electrode active coating on a first surface of the positive electrode current collector is greater than the length of the positive electrode active coating on a second surface of the positive electrode current collector, wherein the area in which the projections of the positive electrode active coating on the first surface and the positive electrode active coating on the second surface overlap in the thickness direction of the positive electrode plate is a double-sided coated area and the area in which the projections do not overlap is a single-sided coated area, wherein the surface of the positive electrode active coating on the first surface is provided with second depressions and the surface of the positive electrode active coating on the second surface is provided with projections, wherein the second recesses and the projections are preferably located in the area coated on both sides, wherein preferably the positive electrode plate comprises a welding area for a tab of the positive electrode, an application area in which the second recesses and the projections are located, and an exposed area, wherein preferably the depth of the second depressions is 3 µm - 40 µm, the width of the second depressions is 0.2 mm - 8 mm, and the distance between the second depressions is 0.5 mm - 8 mm, and wherein preferably the height of the projections is 3 µm - 40 µm, the width of the projections is 0.2 mm - 8 mm, and the distance between the projections is 0.5 mm - 8 mm. [10] Lithium ion secondary battery according to claim 9, characterized by that the positive electrode plate comprises a welding area for a tab of the positive electrode, an application area comprising the double-sided coated area and the single-sided coated area, and an exposed area, wherein the distance of the second recess to an edge of the welding area for the tab of the positive electrode is w1, with 0 mm < w1 ≤ 10 mm, and / or wherein the distance of the second recess to a first edge of the application area at which the welding area for the tab of the positive electrode is arranged is w2, with 2 mm ≤ w2 ≤ 40 mm, and / or wherein the distance of the second recess to a second edge of the application area, which is opposite the edge at which the welding area for the tab of the positive electrode is arranged, is w3, with 2 mm ≤ w3 ≤ 25 mm, and / or wherein the distance of the second recess to a third edge of the application area, which is closer to a starting point for winding, is w4, with 0 mm < w4 ≤ 20 mm, and / or wherein the distance of the second recess to a cutting line between the double-sided coated area and the single-sided coated area is w5, with 0 mm < w5 ≤ 20 mm.

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