Negative electrode pieces, electrochemical apparatus and electronic apparatus

Abstract

To provide a negative pole piece which improves the comprehensive performance of an electrochemical device.SOLUTION: A negative pole piece comprises a negative current collector and a negative active material layer arranged on at least one surface of the negative current collector, the negative active material layer comprises a negative active material, and the negative active material comprises graphite and niobium composite metal oxide; the niobium composite metal oxide comprises at least one of compounds with the molecular formula of TxNbyMzOa; the mass ratio of the niobium composite metal oxide to the graphite is (5-50):(50-95). An electrochemical device adopting the negative pole piece disclosed by the invention has good comprehensive performance.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to the field of electrochemical technology, and more particularly to negative electrode pieces, electrochemical apparatus, and electronic apparatus. [Background technology]

[0002] Lithium-ion batteries are widely used in fields such as household electrical appliances, electric vehicles, and energy storage due to their high specific energy and power density, long cycle life, and environmental friendliness. However, lithium-ion batteries as a power source for new energy vehicles have several practical problems. For example, energy density drops significantly at low temperatures, affecting cycle life accordingly, and storage characteristics are poor at high temperatures, severely limiting the wide range of applications for lithium-ion batteries. Therefore, improving the overall characteristics of lithium-ion batteries is an urgent technical challenge that requires the prompt resolution of those skilled in the art. [Overview of the Initiative] [Problems that the invention aims to solve]

[0003] The embodiments of the present invention aim to provide a negative electrode piece, an electrochemical apparatus, and an electronic apparatus in order to improve the overall characteristics of an electrochemical apparatus.

[0004] In the summary of the present invention, lithium-ion batteries are used as an example of an electrochemical apparatus, but the electrochemical apparatus of the present invention is not limited to lithium-ion batteries. Specific technical ideas are as follows. [Means for solving the problem]

[0005] A first aspect of the present invention provides a negative electrode piece comprising a negative electrode current collector and a negative electrode active material layer provided on at least one surface of the negative electrode current collector, wherein the negative electrode active material layer comprises a negative electrode active material, the negative electrode active material comprises graphite and a niobium composite metal oxide, and the niobium composite metal oxide has the molecular formula T x Nb y M z Oa The compound contains at least one of the following: T contains at least one of K, Li, Fe, V, W, Cr, Zr, Al, Mg, Zn, Cu, Mo, Na, Ga, P, Tc, Si, Ga, Sn, Ni, Co, Mn, Sr, Y, In, and Ti; M contains at least one of Al, Ti, W, Zr, Nb, In, Ru, Sb, Sr, Y, Ni, Co, Mn, Fe, Gr, Mo, Tc, Sn, Ga, Si, V, and Mg; and unlike T and M, a, x, y, and z satisfy 0 ≤ x / (x+y+z) ≤ 0.6, 1 ≤ a / (x+y+z) < 5, and 0 ≤ z / (x+y+z) ≤ 0.5, and the ratio of the mass of the niobium composite metal oxide to the mass of graphite is (5~50):(50~95). The negative electrode active material of the present invention solves the problem of poor electronic conductivity of niobium composite metal oxide by mixing niobium composite metal oxide and graphite and adjusting the ratio of the mass of niobium composite metal oxide to the mass of graphite within the range of the present invention, and also ensures that the niobium composite metal oxide is normal Li under low temperature conditions. + Because the negative electrode active material can be detached, i.e., normal charging and discharging are possible, heat is generated throughout the electrochemical apparatus system during the charging and discharging process. This generated heat increases the internal temperature of the electrochemical apparatus, and as the temperature rises, the dynamic properties of the graphite improve, thereby improving the low-temperature properties of the graphite. By applying the negative electrode piece containing the negative electrode active material of the present invention to an electrochemical apparatus, the electrochemical apparatus has good low-temperature properties, as well as high energy density and good storage properties. As a result, the electrochemical apparatus has good overall properties.

[0006] In some embodiments of the present invention, the structure of the niobium composite metal oxide is at least one of the Wazley-Ross cross-sectional structure and the tungsten bronze structure. If the structure of the niobium composite metal oxide is the above structure, Li + Niobium-complex metal oxides contribute to diffusion, and they also exhibit good structural stability, good cycling properties, and good storage properties. This contributes to improving the overall characteristics of electrochemical equipment.

[0007] In some embodiments of the present invention, the volume average particle diameter Dv50 of the niobium composite metal oxide -1 is 2 μm to 10 μm, and the volume average particle diameter Dv50 of the graphite -2 is 10 μm to 23 μm. By adjusting the volume average particle diameter Dv50 of the niobium composite metal oxide -1 and the volume average particle diameter Dv50 of the graphite -2 within the above ranges, the purpose of improving the compression density by combining large particles and small particles can be achieved, and while the electrochemical device has good low-temperature characteristics and storage characteristics, it contributes to the improvement of the energy density of the electrochemical device.

[0008] In some embodiments of the present invention, the volume average particle diameter Dv50 of the niobium composite metal oxide -1 and the number particle diameter D N 10 of the niobium composite metal oxide satisfy 3 ≦ Dv50 -1 / D N 10 ≦ 26. By adjusting Dv50 -1 / D N 10 within the above ranges, the reduction of small particles and the decrease in the specific surface area of the niobium composite metal oxide can be achieved, and the purpose of reducing gas generation due to side reactions during high-temperature storage can be achieved.

[0009] In some embodiments of the present invention, the volume average particle diameter Dv50 of the niobium composite metal oxide -1 and the volume average particle diameter Dv5 of the graphite -2 satisfy Dv50 -2 / Dv50 -1 ≧ 2. By adjusting Dv50 -2 / Dv50 -1 within the above ranges, the purpose of filling the particles of the niobium composite metal oxide into the gaps of the graphite can be achieved, and further, the compression density of the negative electrode sheet can be improved, and the energy density of the electrochemical device can be improved.

[0010] In some embodiments of the present invention, the specific surface area BET1 of the niobium composite metal oxide is 0.1 m 2 / g to 2.0 m 2 / g, and the specific surface area BET2 of the graphite is 0.5 m 2 / g~10m 2 The value is / g. By adjusting the specific surface area BET1 of the niobium composite metal oxide and the specific surface area BET2 of graphite within the above range, side reactions between the negative electrode active material and the electrolyte can be reduced, contributing to a decrease in gas generation during high-temperature storage.

[0011] In some embodiments of the present invention, the compressed density of the negative electrode piece is 1.6 g / cm³. 3 ~3.6g / cm 3 Therefore, by adjusting the compressive density of the niobium composite metal oxide and the graphite within the above range, it contributes to improving the overall characteristics of the electrochemical apparatus.

[0012] A second aspect of the present invention provides an electrochemical apparatus comprising a negative electrode piece provided in the first aspect of the present invention. Thus, the electrochemical apparatus possesses good overall characteristics.

[0013] A third aspect of the present invention provides an electronic device, including an electrochemical device provided in the second aspect of the present invention.

[0014] Beneficial effects of the embodiments of the present invention: Embodiments of the present invention provide a negative electrode piece, an electrochemical apparatus, and an electronic apparatus. The negative electrode piece comprises a negative electrode current collector and a negative electrode active material layer provided on at least one surface of the negative electrode current collector, the negative electrode active material layer comprises a negative electrode active material, the negative electrode active material comprises graphite and a niobium composite metal oxide, the niobium composite metal oxide having molecular formula T x Nb y M z O aThe compound contains at least one of the following: T contains at least one of K, Li, Fe, V, W, Cr, Zr, Al, Mg, Zn, Cu, Mo, Na, Ga, P, Tc, Si, Ga, Sn, Ni, Co, Mn, Sr, Y, In, and Ti; M contains at least one of Al, Ti, W, Zr, Nb, In, Ru, Sb, Sr, Y, Ni, Co, Mn, Fe, Gr, Mo, Tc, Sn, Ga, Si, V, and Mg; and unlike T and M, a, x, y, z are 0≦x / (x+y+z)≦0.6, 1≦a / (x+y+z)<5, 0≦z / (x+y+z)≦0.5, and the ratio of the mass of the niobium composite metal oxide to the mass of graphite is (5~50):(50~95). The negative electrode active material of the present invention solves the problem of poor electronic conductivity of niobium composite metal oxide by mixing niobium composite metal oxide and graphite and adjusting the ratio of the mass of niobium composite metal oxide to the mass of graphite within the range of the present invention, and also ensures that the niobium composite metal oxide is normal Li under low temperature conditions. + Because the negative electrode active material can be detached, i.e., normal charging and discharging are possible, heat is generated throughout the electrochemical apparatus system during the charging and discharging process. This generated heat increases the internal temperature of the electrochemical apparatus, and as the temperature rises, the dynamic properties of the graphite improve, thereby improving the low-temperature properties of the graphite. By applying the negative electrode piece containing the negative electrode active material of the present invention to an electrochemical apparatus, the electrochemical apparatus has good low-temperature properties, as well as high energy density and good storage properties. As a result, the electrochemical apparatus has good overall properties.

[0015] Of course, when implementing any of the products or methods of the present invention, it is not necessarily required to achieve all of the above advantages simultaneously. [Brief explanation of the drawing]

[0016] To more clearly explain the embodiments of this application and the prior art, the following drawings necessary for describing the embodiments and the prior art will be briefly explained. Of course, the drawings described below are merely some of the embodiments of the present invention, and those skilled in the art can obtain other embodiments based on these drawings. [Figure 1] Figure 1 shows the capacitance-voltage measurement diagrams per gram for Examples 2, 3, and 4 of the present invention. [Figure 2] Figure 2 is a scanning electron microscope (SEM) image of artificial graphite in Comparative Example 1 of the present invention. [Figure 3] Figure 3 is an SEM image of the niobium composite metal oxide in Comparative Example 2 of the present invention. [Modes for carrying out the invention]

[0017] The technical concepts in the embodiments of the present invention will be described in detail below with reference to the drawings of the embodiments. Of course, the embodiments described are merely a part of the embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments that a person skilled in the art can obtain based on the present invention are all within the scope of protection of the present invention.

[0018] In the specific embodiments of the present invention, a lithium-ion battery is used as an example of an electrochemical apparatus, but the electrochemical apparatus of the present invention is not limited to a lithium-ion battery. Specific technical ideas are as follows.

[0019] A first aspect of the present invention provides a negative electrode piece comprising a negative electrode current collector and a negative electrode active material layer provided on at least one surface of the negative electrode current collector, wherein the negative electrode active material layer comprises a negative electrode active material, the negative electrode active material comprises graphite and a niobium composite metal oxide, and the niobium composite metal oxide has the molecular formula T x Nb y M z O aIt contains at least one of the following compounds. Here, T contains at least one of K, Li, Fe, V, W, Cr, Zr, Al, Mg, Zn, Cu, Mo, Na, Ga, P, Tc, Si, Ga, Sn, Ni, Co, Mn, Sr, Y, In, Hf, and Ti, and M contains at least one of Al, Ti, W, Zr, Nb, In, Ru, Sb, Sr, Y, Ni, Co, Mn, Fe, Gr, Mo, Tc, Sn, Ga, Si, V, and Mg, and unlike T and M, a, x, y, z satisfy 0 ≤ x / (x+y+z) ≤ 0.6, 1 ≤ a / (x+y+z) < 5, and 0 ≤ z / (x+y+z) ≤ 0.5. The ratio of the mass of the niobium composite metal oxide to the mass of graphite is (5~50):(50~95). For example, the ratio of the mass of niobium composite metal oxide to the mass of graphite is 5:95, 10:90, 15:85, 20:80, 25:75, 30:70, 35:65, 40:60, 45:55, 50:50, or any ratio within the range of any two of the above ratios.

[0020] Niobium composite metal oxides are formed by melting niobium oxide together with other metal oxides to form a pure phase M-Nb-O compound, and possess high theoretical capacity (340mAh / g~416mAh / g). Furthermore, niobium composite metal oxides contain lithium ions (Li + ) contributes to the diffusion of Li +Because the diffusion coefficient is 2 to 3 orders of magnitude higher than that of lithium titanate (LTO), a common anode active material, niobium composite metal oxides exhibit good rate characteristics. The operating temperature of niobium composite metal oxides is -40°C to 60°C, and the influence of temperature on the dynamic characteristics of niobium composite metal oxides is small, allowing for normal charging and discharging even under low-temperature conditions. In the charging and discharging process of an electrochemical apparatus, the volume change of the unit cell of niobium composite metal oxides is ≤10%. Therefore, niobium composite metal oxides have good structural stability, good cycle characteristics, and good storage characteristics. However, generally, niobium composite metal oxides have the problem of poor electronic conductivity. Graphite, a common anode active material, has good electronic conductivity, but its dynamic characteristics are greatly affected by temperature. At low temperatures, its reaction activity decreases and it undergoes severe polarization, leading to the deposition of a large amount of metallic lithium on the surface of the anode piece, which significantly affects the low-temperature characteristics of the electrochemical apparatus. + The small solid-phase diffusion coefficient in graphite is the main rate-limiting step in the poor capacitance characteristics of electrochemical devices. When electrochemical devices are charged at low temperatures, the small diffusion coefficient is due to Li + By inhibiting the diffusion process in graphite, lithium is more likely to form on the surface of graphite particles, causing permanent damage to electrochemical equipment.

[0021] There is a positive correlation between the energy density of an electrochemical apparatus and the capacity per gram of the anode active material; a higher capacity per gram corresponds to a higher energy density. However, there is a negative correlation between the energy density of an electrochemical apparatus and the voltage platform of the anode active material; a higher voltage platform corresponds to a lower energy density of the electrochemical apparatus. Niobium composite metal oxides have a higher voltage platform for lithium absorption compared to graphite; therefore, from the perspective of energy density, it is necessary to control the ratio of niobium composite metal oxides to graphite. If the ratio of the mass of niobium composite metal oxides to the mass of graphite is less than 5:95, the proportion of niobium composite metal oxides in the anode active material is too low, and the improvement in the low-temperature characteristics of the electrochemical apparatus is not evident. If the ratio of the mass of niobium composite metal oxides to the mass of graphite is greater than 50:50, the proportion of niobium composite metal oxides in the anode active material is too high, affecting the energy density of the electrochemical apparatus. Firstly, niobium composite metal oxides have a lower capacity per gram compared to graphite, and secondly, niobium composite metal oxides have a higher voltage platform for lithium absorption compared to graphite, thus affecting the energy density of the electrochemical apparatus. Therefore, it is necessary to consider the appropriate ratio of niobium composite metal oxide to graphite. The negative electrode active material of the present invention can solve the problem of poor electronic conductivity of niobium composite metal oxides by mixing niobium composite metal oxide and graphite and adjusting the ratio of the mass of niobium composite metal oxide to the mass of graphite within the range of the present invention, and also by ensuring that the niobium composite metal oxide performs normally under low temperature conditions. + Because the negative electrode active material can be detached, i.e., normal charging and discharging are possible, heat is generated throughout the electrochemical apparatus system during the charging and discharging process. This generated heat increases the internal temperature of the electrochemical apparatus, and as the temperature rises, the dynamic properties of the graphite improve, thereby improving the low-temperature properties of the graphite. By applying the negative electrode piece containing the negative electrode active material of the present invention to an electrochemical apparatus, the electrochemical apparatus has good low-temperature properties, as well as high energy density and good storage properties. As a result, the electrochemical apparatus has good overall properties.

[0022] In this invention, low temperature means a temperature of -10°C or a temperature below -10°C.

[0023] The above-mentioned "negative electrode active material layer provided on at least one surface of the negative electrode current collector" refers to a negative electrode active material layer provided on one surface of the negative electrode current collector, or a negative electrode active material layer provided on two surfaces of the negative electrode current collector. Here, "surface" may refer to a part of the surface or all of the surface of the negative electrode current collector.

[0024] Furthermore, niobium composite metal oxide T x Nb y M z O a is Nb 16 W5O 55 Nb 18 W 16 O 93 TiNb2O7, Nb 16 W5O 93 , Cr 0.5 Nb 24.5 O 62 Ti2Nb 14 O 39 TiNb 24 O 62 TiNb6O 17 Ni2Nb 34 O 87 Cu2Nb 34 O 87 , Cr 0.5 Nb 24.5 O 62 , V3Nb 17 O 50 Zn2Nb 34 O 87 , Al 0.5 Nb 24.5 O 62 MoNb 12 O 33 , ZrNb 24 O 62 AlNb 11 O 29 Mg2Nb 34 O 87 GaNb 11 O 29 Mo3Nb 14 O 44 , CrNb 11 O 29, HfNb 24 O 62 , FeNb 11 O 28 , GaNb 49 O 124 , NaNb 13 O 33 , Ni2Nb 34 O 87 , TiNb6O 17 , WNb 12 O 33 , LiNbO3, Li3NbO4, TiCr 0.5 Nb 10.5 O2, VNb9O 25 , KNb5O 13 , K6Nb 10.8 O 30 , PNb9O 25 , Nb 18 W8O 69 , Ti2Nb 10 O 29 , Cr 0.2 Fe 0.8 Nb 11 O 29 , Fe 0.8 Mn 0.2 Nb 11 O 29 , Fe 0.8 V 0.2 Nb 11 O 29 Or Cu 0.02 Ti 0.94 Nb 2.04 Includes at least one of O7.

[0025] In some embodiments of the present invention, the structure of the niobium composite metal oxide is at least one of the Wadsley-Roth cross-sectional structure or the tungsten bronze structure. When the structure of the niobium composite metal oxide is the above structure, Li + Contributes to the diffusion of, and the niobium composite metal oxide has good structural stability, good cycle characteristics, and good storage characteristics. This contributes to the improvement of the overall characteristics of the electrochemical device. [[ID=八十六]]

[0026] The present invention is not particularly limited in terms of the method for controlling the niobium composite metal oxide structure, and is sufficient as long as the objective of the present invention is achieved. For example, this may be achieved by controlling the firing temperature, firing time, type of raw materials, and the mixing ratio of different raw materials in the preparation process of the niobium composite metal oxide.

[0027] In some embodiments of the present invention, the volume-average particle size Dv50 of the niobium composite metal oxide -1 The particle size is 2 μm to 10 μm, and the volume-average particle size of graphite is Dv50. -2 The size is 10 μm to 23 μm. For example, Dv50 -1 This is a value within the range of 2μm, 3μm, 4μm, 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, or any two of the above values. Dv50 -2 This is 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, 20 μm, 21 μm, 22 μm, 23 μm, or any value within the range between any two of the above values. In order to improve the effect of graphite on improving the electronic conductivity of niobium composite metal oxide, the volume average particle diameter Dv50 of the niobium composite metal oxide -1 and the volume-average particle size of graphite Dv50 -2 By adjusting these parameters within the above range, the niobium composite metal oxide and graphite have a suitable contact area, contributing to good electronic conductivity of the niobium composite metal oxide. The objective of improving compressive density by combining large and small particles can also be achieved, contributing to improved energy density of the electrochemical apparatus while maintaining good low-temperature and storage characteristics. As a result, the electrochemical apparatus possesses excellent overall characteristics.

[0028] In some embodiments of the present invention, the volume-average particle size Dv50 of the niobium composite metal oxide -1 and the number of niobium composite metal oxide particles and particle size D N 10 is equivalent to 3 ≤ Dv50 -1 / D N The condition 10 ≤ 26 is satisfied. For example, Dv50 -1 / D NThe value of 10 is 3, 5, 8, 11, 14, 17, 20, 23, 26, or any number within the range between any two of the above values. The smaller the particle size of the niobium composite metal oxide particles, the larger the specific surface area and the more side reactions there are with the electrolyte. The better the uniformity of the niobium composite metal oxide particle size, the fewer smaller particles fill the gaps between larger particles, which is unfavorable for improving the compressive density of the niobium composite metal oxide. Dv50 -1 / D N By adjusting 10 within the above range, the number of small particles in the niobium composite metal oxide and the uniformity of the niobium composite metal oxide particle size are within a suitable range, which contributes to reducing the reaction between the niobium composite metal oxide and the electrolyte, and also contributes to improving the compressive density of the niobium composite metal oxide. In this way, it contributes to improving the low-temperature characteristics, energy density, and storage characteristics of the electrochemical apparatus. As a result, the electrochemical apparatus has good overall characteristics.

[0029] This invention relates to the number of particles D of niobium composite metal oxides. N There are no particular restrictions on 10, as long as the objective of the present invention can be achieved. For example, the number of particles of a niobium composite metal oxide, and the particle size D N 10 is between 0.1 μm and 2 μm.

[0030] In some embodiments of the present invention, the volume-average particle size Dv50 of the niobium composite metal oxide -1 and the volume-average particle size of graphite Dv50 -2 That is, Dv50 -2 / Dv50 -1 The condition ≥ 2 is satisfied. In some embodiments, 2 ≤ Dv50 -2 / Dv50 -1 ≤ 7. For example, Dv50 -2 / Dv50 -1 The value is 2, 4, 5, 6, 7, 8, 9, 10, 11, 11.5, or any number within the range between any two of the above numbers. Dv50 -2 / Dv50 -1By adjusting the parameters within the above range, denser deposition of niobium composite metal oxides and graphite can be achieved, contributing to an improvement in the compressive density of the negative electrode pieces. This improves the low-temperature characteristics, energy density, and storage characteristics of the electrochemical apparatus. As a result, the electrochemical apparatus possesses excellent overall characteristics.

[0031] In the present invention, Dv50 -1 This refers to the central particle diameter of the powder, where the diameter of niobium composite metal oxide particles, which account for 50% of the total volume, is greater than this value, and the diameter of niobium composite metal oxide particles, which account for 50% of the total volume, is smaller than this value. Dv50 -2 This refers to the central particle diameter of the powder, where the diameter of graphite particles accounting for 50% of the total volume is greater than this value, and the diameter of graphite particles accounting for the remaining 50% of the total volume is smaller than this value. N The value 10 indicates that the diameter of the niobium composite metal oxide particles, which account for 10% of the total volume, is smaller than this value.

[0032] In some embodiments of the present invention, the specific surface area BET1 of the niobium composite metal oxide is 0.1 m². 2 / g~2.0m 2 The specific surface area of ​​graphite is 0.5 m² / g, and the specific surface area BET2 of graphite is 0.5 m². 2 / g~10m 2 The value is / g. For example, the specific surface area BET1 of a niobium composite metal oxide is 0.1m². 2 / g, 0.2m 2 / g, 0.4m 2 / g, 0.6m 2 / g, 0.8m 2 / g, 1.0m 2 / g, 1.2m 2 / g, 1.4m 2 / g, 1.6m 2 / g, 1.8m 2 / g, 2.0m 2 The value is either / g or any value within the range between any two of the above values. The specific surface area BET2 of graphite is 0.5m². 2 / g, 1m 2 / g, 2m 2 / g, 3m 2 / g, 4m 2 / g, 5m2 / g, 6m 2 / g, 7m 2 / g, 8m 2 / g, 9m 2 / g, 10m 2 / g or any value within the range between any two of the above values. By adjusting the specific surface area BET1 of the niobium composite metal oxide and the specific surface area BET2 of graphite within the above range, it contributes to reducing side reactions between the negative electrode active material and the electrolyte, and contributes to reducing the amount of solid electrolyte interface (SEI) film formed, thereby reducing the amount of SEI film Li + By reducing the inhibition of intercalation and contributing to the reduction of gas generation during high-temperature storage of the electrochemical apparatus, the thickness expansion coefficient of the electrochemical apparatus is reduced, thereby improving the storage characteristics of the electrochemical apparatus. As a result, the electrochemical apparatus has good overall characteristics.

[0033] The smaller the particles of the negative electrode active material, the larger the corresponding specific surface area, Li + The travel path is short, Li + This contributes to the desorption process and the volume per gram, but it also affects gas generation during high-temperature storage. This is because the larger the specific surface area of ​​the negative electrode active material, the greater the side reaction between the negative electrode active material and the electrolyte, causing the electrochemical apparatus to expand due to gas generation, which does not contribute to its safety and reliability.

[0034] This invention relates to the volume-average particle size Dv50 of niobium composite metal oxides. -1 , number of niobium composite metal oxide particles, particle size D N There are no particular restrictions on the method for controlling the specific surface area BET1 of 10 and the niobium composite metal oxide, as long as the objective of the present invention can be achieved. For example, this can be achieved by adjusting process parameters in the preparation process of the niobium composite metal oxide, such as crushing and sieving. Alternatively, it can be achieved by purchasing from a manufacturer.

[0035] This invention relates to the volume-average particle size Dv50 of graphite. -2 Furthermore, there are no particular restrictions on the method for controlling the specific surface area BET2 of graphite, as long as the objective of the present invention can be achieved. For example, it may be achieved by purchasing from a manufacturer.

[0036] There is a positive correlation between the compressible density of the negative electrode piece and the true density of the negative electrode active material, and this has a decisive influence on the compressible density of the negative electrode active material. Furthermore, the combination of large and small particles also affects the compressible density of the negative electrode piece, but its influence on the compressible density of the negative electrode piece is smaller than that of the true density.

[0037] In some embodiments of the present invention, the true density of graphite is lower than the true density of the niobium composite metal oxide, and the true density TD1 of the niobium composite metal oxide is 4.2 g / cm³. 3 ~5.5g / cm 3 Therefore, the true density of graphite TD2 is 2.20 g / cm³. 3 ~2.26 g / cm³ 3 For example, the true density TD1 of niobium composite metal oxide is 4.2 g / cm³. 3 4.4 g / cm³ 3 4.6 g / cm³ 3 4.8 g / cm³ 3 5.0 g / cm³ 3 5.2 g / cm³ 3 5.4 g / cm³ 3 5.5 g / cm³ 3 Or it is any value within the range between any two of the above values. The true density of graphite TD2 is 2.20 g / cm³. 3 2.21 g / cm³ 3 , 2.22 g / cm³ 3 2.23 g / cm³ 3 2.24 g / cm³ 3 2.25 g / cm³ 3 2.26 g / cm³ 3 Alternatively, it is any value within the range between any two of the above values. By adjusting the true density TD1 of the niobium composite metal oxide and the true density TD2 of graphite within the above range, the compressive density of the negative electrode piece is improved, thereby increasing the energy density of the electrochemical apparatus.

[0038] In this invention, true density is based on the actual volume of solid material within a volume of graphite or niobium composite metal oxide in a perfectly dense state, excluding internal pores or gaps between particles.

[0039] In some embodiments of the present invention, the compressed density of the negative electrode piece is 1.6 g / cm³. 3 ~3.6g / cm 3 For example, the compressed density of the negative electrode piece is 1.6 g / cm³. 3 1.8 g / cm³ 3 2.0 g / cm³ 3 , 2.2 g / cm³ 3 2.4 g / cm³ 3 2.6 g / cm³ 3 2.8 g / cm³ 3 3.0 g / cm³ 3 3.2 g / cm³ 3 3.4 g / cm³ 3 3.6 g / cm³ 3 Alternatively, it is any value within the range between any two of the above values. By controlling the compressive density of the negative electrode piece within the above range, the negative electrode piece has a high compressive density, thereby providing a high energy density. In this way, the electrochemical apparatus has good low-temperature characteristics and storage characteristics, as well as a high energy density. As a result, the electrochemical apparatus has good overall characteristics.

[0040] The present invention does not have any particular limitations on the method for controlling the compression density of the negative electrode piece, as long as the objective of the present invention is achieved. For example, it may be achieved by controlling the pressure during the cold pressing process of the negative electrode piece, or by adjusting the type of negative electrode active material or the average particle size. The present invention does not have any particular limitations on the magnitude of the above pressure, as long as the objective of the present invention is achieved. For example, the pressure is 40t to 80t.

[0041] The present invention is not particularly limited in terms of the type of graphite, as long as it can achieve the objectives of the present invention. For example, graphite includes, but is not limited to, artificial graphite and natural graphite.

[0042] The present invention does not particularly limit the method for preparing niobium composite metal oxides, as long as the objective of the present invention is achieved. For example, the method for preparing niobium composite metal oxides includes, but is not limited to, the steps of selecting NbO2 and other metal oxides, mixing them according to the molar ratio of the molecular formula of the niobium composite metal oxide, calcining at 700°C to 1500°C for 2 to 24 hours after mixing, crushing, and sieving to obtain the desired niobium composite metal oxide. The present invention does not particularly limit the type of "other metal oxides" mentioned above, and those skilled in the art can select them as needed, as long as a niobium composite metal oxide within the scope of the present invention is obtained and the objective of the present invention is achieved.

[0043] The present invention does not have any particular limitations on the negative electrode current collector, as long as it can achieve the objectives of the present invention. For example, the negative electrode current collector may include copper foil, copper alloy foil, nickel foil, stainless steel foil, titanium foil, foamed nickel, and foamed copper. In the present invention, there are no particular limitations on the thickness of the negative electrode current collector or the negative electrode active material layer, as long as it can achieve the objectives of the present invention. For example, the thickness of the negative electrode current collector is 6 μm to 10 μm, and the thickness of the negative electrode active material layer is 30 μm to 130 μm.

[0044] In some embodiments of the present invention, the negative electrode active material layer further comprises at least one of a negative electrode conductive agent, a thickener, and a negative electrode binder. The present invention is not particularly limited in terms of the types of negative electrode conductive agent, thickener, and negative electrode binder, as long as the objectives of the present invention can be achieved. The present invention is not particularly limited in terms of the mass ratio of the negative electrode active material, negative electrode conductive agent, thickener, and negative electrode binder in the negative electrode active material layer, as long as the objectives of the present invention can be achieved. For example, the mass ratio of the negative electrode active material, negative electrode conductive agent, negative electrode binder, and thickener in the mass of the negative electrode active material layer is (90-98):(0.5-3):(1-4):(0.5-3).

[0045] A second aspect of the present invention provides an electrochemical apparatus comprising a negative electrode piece provided in the first aspect of the present invention. The electrochemical apparatus thus possesses good overall characteristics, such as good low-temperature characteristics and storage characteristics, and high energy density.

[0046] In some embodiments of the present invention, the electrochemical apparatus further includes a positive electrode piece. The present invention is not particularly limited to the positive electrode piece, as long as it can achieve the objectives of the present invention. For example, the positive electrode piece includes a positive electrode current collector and a positive electrode active material layer provided on at least one surface of the positive electrode current collector. The present invention is not particularly limited to the type of positive electrode current collector, as long as it can achieve the objectives of the present invention. For example, the positive electrode current collector may include aluminum foil and aluminum alloy foil. The positive electrode active material layer of the present invention includes a positive electrode active material, and the present invention is not particularly limited to the type of positive electrode active material, as long as it includes a transition metal element of the present invention, as long as it can achieve the objectives of the present invention. For example, the positive electrode active material may be lithium nickel cobalt manganese oxide (LiNi 0.8 Co 0.1 Mn 0.1 The positive electrode active material may contain at least one of the following: O2, lithium nickel-cobalt aluminate, lithium iron phosphate, lithium-rich manganese-based materials, lithium cobalt oxide (LiCoO2), lithium manganese oxide, lithium iron manganese phosphate, and lithium titanate. In the present invention, the positive electrode active material may further contain nonmetallic elements, for example, at least one of fluorine, phosphorus, boron, chlorine, silicon, or sulfur, and these elements can further improve the stability of the positive electrode active material. In the present invention, there are no particular restrictions on the thickness of the positive electrode current collector and the positive electrode active material layer, as long as the objective of the present invention is achieved. For example, the thickness of the positive electrode current collector is 5 μm to 20 μm, preferably 6 μm to 18 μm. The thickness of the positive electrode active material layer is 30 μm to 120 μm. Optionally, the positive electrode active material layer may further contain a positive electrode conductive agent and a positive electrode binder. The present invention does not place any particular restrictions on the types of positive electrode conductive agent and positive electrode binder in the positive electrode active material layer, as long as the objective of the present invention can be achieved. The present invention also does not place any particular restrictions on the mass ratio of the positive electrode active material, positive electrode conductive agent and positive electrode binder in the positive electrode active material layer, and those skilled in the art may select them as needed, as long as the objective of the present invention can be achieved. For example, the mass ratio of the positive electrode active material to the positive electrode conductive agent and positive electrode binder in the positive electrode active material layer is (90~98):(0.5~5):(1.5~5).

[0047] In some embodiments of the present invention, the electrochemical apparatus further includes a separator, which is provided between a positive electrode and a negative electrode to isolate the positive and negative electrode pieces, prevent short circuits inside the electrochemical apparatus, allow electrolyte ions to pass freely, and do not affect the electrochemical charging and discharging process. The present invention is not particularly limited to the separator, as long as it can achieve the objectives of the present invention. For example, the material of the separator may include, but is not limited to, at least one of polyethylene (PE), polyolefins (PO) mainly consisting of polypropylene (PP), polyester (e.g., polyethylene terephthalate (PET) film), cellulose, polyimide (PI), polyamide (PA), spandex, and aramid. The type of separator may include at least one of woven film, nonwoven film, microporous film, composite film, pressed film, and spun film.

[0048] In some embodiments of the present invention, the electrochemical apparatus further comprises a packaging bag and an electrolyte, the electrolyte and electrode assembly being housed in the packaging bag, and the electrode assembly comprising a positive electrode piece, a separator and a negative electrode piece. The present invention is not particularly limited to the packaging bag and electrolyte, and may be a packaging bag and electrolyte known in the art, as long as they can achieve the objectives of the present invention.

[0049] The present invention is not particularly limited in terms of the type of electrochemical apparatus and may include any apparatus that generates an electrochemical reaction. For example, the electrochemical apparatus includes, but is not limited to, lithium metal secondary batteries, lithium-ion secondary batteries (lithium-ion batteries), sodium-ion secondary batteries (sodium-ion batteries), lithium polymer secondary batteries, and lithium-ion polymer secondary batteries (lithium-ion polymer batteries).

[0050] The preparation process for the electrochemical apparatus of the present invention is well known to those skilled in the art and is not particularly limited in the present invention. For example, the process may include steps such as stacking positive electrode pieces, separators and negative electrode pieces in order, winding or folding them as needed to obtain a wound electrode assembly, placing the electrode assembly in a packaging bag, pouring electrolyte into the packaging bag and sealing it to obtain the electrochemical apparatus, or stacking positive electrode pieces, separators and negative electrode pieces in order, then fixing the four corners of the entire stacked structure with adhesive tape to obtain a stacked electrode assembly, placing the electrode assembly in a packaging bag, pouring electrolyte into the packaging bag and sealing it to obtain the electrochemical apparatus, but is not limited to these steps. Furthermore, in order to prevent pressure rise inside the electrochemical apparatus, overcharging and over-discharging, etc., overcurrent protection elements, lead plates, etc. may be placed in the packaging bag as needed.

[0051] A third aspect of the present invention provides an electronic device including an electrochemical apparatus provided in the second aspect of the present invention. Therefore, the electronic device has good operational performance.

[0052] The electronic devices of the present invention are not particularly limited and may be any known electronic devices used in the prior art. For example, the electronic devices may include, but are not limited to, laptop computers, pen-input computers, mobile computers, e-book players, mobile phones, portable facsimile machines, portable copiers, portable printers, stereo headsets, video recorders, LCD televisions, portable cleaners, portable CD players, mini CDs, transceivers, electronic notebooks, calculators, memory cards, portable tape recorders, radios, backup power supplies, motors, automobiles, motorcycles, electric assist bicycles, bicycles, lighting fixtures, toys, game consoles, clocks, power tools, flashlights, cameras, large household storage batteries, and lithium-ion capacitors.

[0053] Examples The embodiments of the present invention will be described in more detail below with reference to examples and comparative examples. Each test and evaluation will be carried out according to the following methods.

[0054] Measurement method and equipment: Dv50 -1 Dv50 -2 and D N 10 measurements: Using a Malvern particle size analyzer, the particle size distribution of graphite and niobium composite metal oxide in the negative electrode active material was measured, and the Dv50 of the niobium composite metal oxide was determined. -1 and D N 10, and graphite Dv50 -2 The following was obtained. The specific measurements were performed according to the Chinese national standard GB / T19077-2016, "Particle Size Analysis: Laser Diffraction Method".

[0055] Measurement of specific surface area BET1 and BET2: Using a specific surface area analyzer (TristarII3020M), the specific surface area of ​​graphite and niobium composite metal oxides in the negative electrode active materials of each example and comparative example was measured by nitrogen adsorption. The specific measurements were performed in accordance with the Chinese national standard GB / T 19587-2017, "Measurement of Specific Surface Area of ​​Solid Materials by Gas Adsorption BET Method."

[0056] Measurement of the compressed density of the negative electrode piece: Compression density = Mass of the negative electrode active material layer per unit area (g / cm³) 2 ) / Thickness of the negative electrode active material layer (cm).

[0057] Measurement of volume per gram: The negative electrode piece from each example and comparative example was taken and assembled with the Li piece to form a coin cell. The capacity per gram after discharging to 5.0 mV was defined as the capacity per gram. The specific discharge process involved discharging to 5.0 mV at 0.05 C and charging to 3.0 V at 0.1 C. The capacity of the coin cell at this time was recorded as the capacity per gram. 0.05 C refers to the current value at 0.05 times the designed capacity per gram, and 0.1 C refers to the current value at 0.1 times the designed capacity per gram.

[0058] Measurement of low-temperature characteristics: The lithium-ion batteries in each example and comparative example were charged to 4.3V at 25°C at 0.2C, and the charged capacity was defined as C1. They were then charged to 4.3V at -20°C at 1C, and the charged capacity was defined as C2. The capacity retention rate R = C2 / C1 × 100%, where R represents the low-temperature characteristics, and a larger R value indicates better low-temperature characteristics.

[0059] Measurement of storage characteristics: The lithium-ion batteries of each example and comparative example were stored at 85°C for 12 hours, and the change in thickness of the lithium-ion batteries before and after storage was recorded. The thickness expansion rate T = (thickness after storage - thickness before storage) / thickness before storage × 100%. T represents the storage characteristics, and a smaller T value indicates better storage characteristics.

[0060] Example 1 <Preparation of negative electrode active material> Preparation of niobium composite metal oxides: Nb by solid-phase method 16 W5O 55 The following was synthesized: The raw materials were NbO2 and WO2, which were uniformly mixed in a molar ratio of 16:5, then calcined at 1150°C for 10 hours, crushed, and sieved to obtain Dv50. -1 It is 3.8 μm, D N 10 is 0.35 μm, and BET1 is 1.5 μm. 2 Nb is / g 16 W5O 55 This was obtained.

[0061] The above-mentioned niobium composite metal oxide Nb 16 W5O 55 The negative electrode active material was obtained by mixing it with artificial graphite in a mass ratio of 5:95.

[0062] Of these, the specific surface area of ​​artificial graphite is BET2 = 0.65 m². 2 / g, volume-average particle size Dv50 -2 The thickness was 15.9 μm. The structure of the niobium composite metal oxide was a Wazley-Ross cross-sectional structure.

[0063] <Preparation of negative electrode piece> The negative electrode active material obtained above, acetylene black as the negative electrode conductive agent, and styrene-butadiene rubber (SBR, with a weight-average molecular weight of 1 × 10) as the negative electrode binder. 5 ~1.1 × 10 5 The mixture was mixed with carboxymethylcellulose sodium (CMCNa), a thickening agent, in a mass ratio of 95:2:2:1. Deionized water was added as a solvent, and the mixture was stirred using a mixer until a homogeneous negative electrode slurry with a solid content of 70 wt% was obtained. The negative electrode slurry was uniformly applied to one surface of a 6 μm thick copper foil negative electrode current collector, dried at 90°C, and a negative electrode piece with a 130 μm thick negative electrode active material layer applied to one side was obtained. Subsequently, the above steps were repeated on the other surface of the copper foil to obtain a negative electrode piece with negative electrode active material layers applied to both sides. After cold pressing, slitting, and tab welding, a negative electrode piece with a size of 76 mm × 867 mm was obtained and set aside.

[0064] <Preparation of positive electrode piece> The positive electrode active material is lithium nickel cobalt manganese (molecular formula LiNi 0.5 Co 0.2 Mn 0.3 O2 (abbreviated as NCM523), acetylene black as the positive electrode conductive agent, and polyvinylidene fluoride (PVDF, weight-average molecular weight 2 × 10) as the positive electrode binder. 5 ~10×10 5 The two materials were mixed in a mass ratio of 94:3:3, N-methylpyrrolidone (NMP) was added as a solvent, and the mixture was stirred using a vacuum mixer until a homogeneous positive electrode slurry with a solid content of 75 wt% was obtained. The positive electrode slurry was uniformly applied to one surface of a 6 μm thick aluminum foil positive electrode current collector and dried at 90°C to obtain a positive electrode piece with a positive electrode active material layer applied to one side. Subsequently, the above steps were repeated on the other surface of the aluminum foil to obtain a positive electrode piece with positive electrode active material layers applied to both sides. After cold pressing, slitting, and tab welding, a positive electrode piece measuring 74 mm × 851 mm was obtained and set aside.

[0065] <Preparation of the separator> A porous polyethylene (PE) thin film with a thickness of 8 μm was used as the separator.

[0066] <Preparation of Electrolyte> In an environment with a water content of less than 10 ppm, lithium hexafluorophosphate, a lithium salt, was mixed with a non-aqueous organic solvent (ethylene carbonate (EC): propylene carbonate (PC): polypropylene (PP): diethyl carbonate (DEC) = 1:1:1:1, mass ratio) to prepare an electrolyte with a lithium salt concentration of 1.0 mol / L.

[0067] <Preparation of Lithium-ion Batteries> An electrode assembly was obtained by stacking the positive electrode, separator, and negative electrode in order, with the separator acting as an intermediary between the positive electrode and negative electrode pieces to provide isolation, and then winding the stack. The electrode assembly was placed in an aluminum plastic film packaging bag, moisture was removed at 80°C, the electrolyte described above was injected and the bag was sealed, and after processes such as formation, degassing, and shaping, a lithium-ion battery was obtained.

[0068] Examples 2 to 4 The procedure was the same as in Example 1, except that the relevant preparation parameters were adjusted according to Table 1.

[0069] Example 5 Preparation of niobium composite metal oxides: Nb by solid-phase method 16 W5O 93 The following was synthesized: The raw materials were NbO2 and WO2, which were mixed in a molar ratio of 16:5 and homogenized. After firing at 1200°C for 10 hours, the mixture was crushed and sieved to obtain Dv50. -1 It is 6.2 μm, D N 10 is 0.5 μm, and BET1 is 1.2 μm. 2 Nb is / g 16 W5O 93 This was obtained.

[0070] Other than this, it was the same as Example 3.

[0071] Example 6 Preparation of niobium composite metal oxide: TiNb2O7 was synthesized by solid-phase method. The raw materials were NbO2 and TiO2, which were mixed in a 2:1 molar ratio until homogenized, then calcined at 1150°C for 10 hours, crushed, and sieved to obtain Dv50. -1 It is 5.8 μm, D N 10 is 0.26 μm, and BET1 is 1.3 μm. 2 TiNb2O7 at a concentration of / g was obtained.

[0072] Other than this, it was the same as Example 3.

[0073] Example 7 Preparation of niobium composite metal oxides: Fe by solid-phase method 0.8 Nb 11 Mn 0.2 O 29 The following was synthesized: The raw materials were Fe2O3, Nb2O5, and Mn2O3, which were mixed in a molar ratio of 0.8:11:0.2 and homogenized. After firing at 130°C for 4 hours, the mixture was crushed and sieved to obtain Dv50. -1 It is 3.4 μm, D N 10 is 0.3 μm, and BET1 is 1.6 μm. 2 Fe / g 0.8 Nb 11 Mn 0.2 O 29 This was obtained.

[0074] Other than this, it was the same as Example 3.

[0075] Examples 8 to 16 The procedure was the same as in Example 3, except that the relevant preparation parameters were adjusted according to Table 1.

[0076] Comparative Examples 1 to 4 The procedure was the same as in Example 1, except that the relevant preparation parameters were adjusted according to Table 1.

[0077] The preparation parameters and characteristic parameters for each example and comparative example are shown in Tables 1 and 2.

[0078] [Table 1] In Table 1, "\" indicates that there are no relevant adjustment parameters.

[0079] [Table 2]

[0080] As can be seen from Examples 1 to 16 and Comparative Examples 1 to 4, in the lithium-ion battery of the embodiment of the present invention, the negative electrode active material is graphite and niobium composite metal oxide T x Nb y M z O a The lithium-ion battery of the embodiment of the present invention has high capacity per gram, capacity retention rate R, and low thickness expansion rate T, as the ratio of the mass of the niobium composite metal oxide to the mass of graphite is within the range of the present invention. This indicates that the lithium-ion battery of the present invention has good overall characteristics, as it has high energy density, good low-temperature characteristics and high-temperature storage characteristics. However, in the lithium-ion battery of the comparative example, the negative electrode active material is graphite and niobium composite metal oxide T x Nb y M z O aBy including one of the above, or by having a ratio of the mass of niobium composite metal oxide to the mass of graphite that is outside the scope of the present invention, the comparative lithium-ion battery is inferior in at least one of the capacity per gram, capacity retention rate R, and thickness expansion rate T. This indicates that the overall characteristics of the lithium-ion battery are inferior because at least one of the energy density, low-temperature characteristics, and high-temperature storage characteristics of the comparative lithium-ion battery is inferior. Figure 1 shows the capacity-voltage measurement diagrams per gram for Examples 2, 3, and 4, and the amount of niobium composite metal oxide used in the negative electrode active material of Examples 2, 3, and 4 tends to increase. As can be seen from Figure 1, the voltage platform of the negative electrode active material increases with increasing amount of niobium composite metal oxide used. This also means that the voltage platform of the lithium-ion battery decreases (the voltage platform of a lithium-ion battery = positive electrode potential - negative electrode potential), and the energy density of the lithium-ion battery decreases. However, as can be seen from the table, lithium-ion batteries in which the amount of niobium composite metal oxide used is within the scope of the present invention have a high capacity per gram. This indicates that if a negative electrode active material in which the ratio of the mass of niobium composite metal oxide to the mass of graphite is adjusted within the range of the present invention is applied to a lithium-ion battery, the lithium-ion battery can have a high energy density. Figure 2 shows an SEM image of artificial graphite in Comparative Example 1 of the present invention, and Figure 3 shows an SEM image of niobium composite metal oxide in Comparative Example 2 of the present invention. Comparing Figures 2 and 3, it can be seen that the particle size of the artificial graphite in Figure 2 is larger than the particle size of the niobium composite metal oxide in Figure 3.

[0081] The ratio of the mass of niobium composite metal oxide to the mass of graphite typically affects the energy density, low-temperature characteristics, and high-temperature storage characteristics of lithium-ion batteries. As can be seen from Examples 1 to 4 and Comparative Examples 1 to 4, lithium-ion batteries in which the ratio of the mass of niobium composite metal oxide to the mass of graphite falls within the range of the present invention have high capacity per gram and capacity retention rate R, as well as a relatively low thickness expansion rate T. This indicates that lithium-ion batteries have high energy density, good low-temperature characteristics, and good high-temperature storage characteristics, resulting in good overall characteristics. In the lithium-ion batteries of Comparative Examples 1 and 3, artificial graphite and a mixture in which the ratio of the mass of niobium composite metal oxide to the mass of graphite is 2:98 were selected as the negative electrode active material, and the lithium-ion batteries had high capacity per gram, but low capacity retention rate R and high thickness expansion rate T. In the lithium-ion batteries of Comparative Examples 2 and 4, a mixture was selected as the negative electrode active material in which the ratio of the mass of niobium composite metal oxide to the mass of graphite was 98:2, respectively. The lithium-ion batteries exhibited a high capacity retention rate R and a low thickness expansion rate T, but had a low capacity per gram. As is known to those skilled in the art, increasing the capacity per gram is difficult. Consequently, the overall characteristics of the lithium-ion batteries of Comparative Examples 1 to 4 are inferior.

[0082] The type of niobium composite metal oxide typically affects the energy density, low-temperature characteristics, and high-temperature storage characteristics of lithium-ion batteries. As can be seen from Examples 3 and 5-7, lithium-ion batteries in which the type of niobium composite metal oxide is selected from within the scope of the present invention exhibit high capacity per gram, high capacity retention rate R, and low thickness expansion rate T. This indicates that lithium-ion batteries have high energy density, good low-temperature characteristics, and good high-temperature storage characteristics, resulting in good overall characteristics.

[0083] Volume-average particle size Dv50 of niobium composite metal oxides -1 , graphite volume-average particle size Dv50 -2The specific surface area BET1 of niobium composite metal oxide and the specific surface area BET2 of graphite typically affect the energy density, low-temperature characteristics, and high-temperature storage characteristics of lithium-ion batteries. As can be seen from Examples 3 and 5 to 16, the volume-average particle size Dv50 of niobium composite metal oxide -1 , graphite volume-average particle size Dv50 -2 Lithium-ion batteries in which the specific surface area BET1 of the niobium composite metal oxide and the specific surface area BET2 of graphite fall within the scope of the present invention possess high capacity per gram, a capacity retention rate R, and a low thickness expansion rate T. This indicates that lithium-ion batteries have high energy density, good low-temperature characteristics and high-temperature storage characteristics, and possess good overall characteristics.

[0084] Volume-average particle size Dv50 of niobium composite metal oxides -1 and the number of niobium composite metal oxide particles and particle size D N Dv50 (ratio to 10) -1 / D N 10 typically affects the energy density, low-temperature characteristics, and high-temperature storage characteristics of lithium-ion batteries. As can be seen from Examples 3, 5 to 16, Dv50 -1 / D N Lithium-ion batteries in which the value of 10 falls within the scope of the present invention have high capacity per gram and capacity retention rate R, and low thickness expansion rate T. This indicates that lithium-ion batteries have high energy density, good low-temperature characteristics, and high-temperature storage characteristics.

[0085] The compressed density of the negative electrode typically affects the capacity per gram, low-temperature characteristics, and high-temperature storage characteristics of a lithium-ion battery. As can be seen from Examples 1 to 16, lithium-ion batteries in which negative electrode pieces with a compressed density within the range of the present invention are selected exhibit high capacity per gram and capacity retention rate R, and low thickness expansion rate T. This indicates that lithium-ion batteries have high energy density, good low-temperature characteristics, and good high-temperature storage characteristics, resulting in good overall characteristics.

[0086] Graphite volume-average particle size Dv50 -2 and niobium composite metal oxide volume average particle diameter Dv50 -1Dv50 -2 / Dv50 -1 This typically affects the capacity per gram, low-temperature characteristics, and high-temperature storage characteristics of lithium-ion batteries. As can be seen from Examples 3, 5-11, and 14, Dv50 -2 / Dv50 -1 Lithium-ion batteries whose values ​​fall within the scope of the present invention possess high capacity per gram and capacity retention rate R, as well as a low thickness expansion rate T. This indicates that lithium-ion batteries have high energy density, good low-temperature characteristics and high-temperature storage characteristics, and possess good overall characteristics.

[0087] In this specification, the terms “include,” “contain,” or any other variation thereof mean “contain” in a non-exclusive sense. Therefore, a process, method, article, or device that includes a set of elements includes not only those elements but also other elements not explicitly listed, or elements specific to such a process, method, article, or device.

[0088] Each example in this specification is described in a relevant manner, and any identical or similar parts between examples may be cross-referenced. Each example is described with emphasis on the differences from the other examples.

[0089] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application are included within the scope of protection of the present invention.

Claims

1. It is a negative electrode piece, It includes a negative electrode current collector and a negative electrode active material layer provided on at least one surface of the negative electrode current collector, The aforementioned negative electrode active material layer contains a negative electrode active material. The negative electrode active material comprises graphite and a niobium composite metal oxide. The aforementioned niobium composite metal oxide has the molecular formula T ｘ Nb ｙ M ｚ O ａ It contains at least one of the following compounds: T includes at least one of K, Li, Fe, V, W, Cr, Zr, Al, Mg, Zn, Cu, Mo, Na, Ga, P, Tc, Si, Ga, Sn, Ni, Co, Mn, Sr, Y, In, Hf, and Ti. M includes at least one of Al, Ti, W, Zr, Nb, In, Ru, Sb, Sr, Y, Ni, Co, Mn, Fe, Gr, Mo, Tc, Sn, Ga, Si, V, and Mg, and Unlike T and M, a, x, y, and z satisfy x / (x+y+z)=0, 1≦a / (x+y+z)<5, and 0≦z / (x+y+z)≦0.

5. Volume average particle diameter Dv50 of the niobium composite metal oxide －１ The size is 2 μm to 7 μm. Number of particles D of the niobium composite metal oxide Ｎ 10 is between 0.1 μm and 2 μm. The volume average particle diameter Dv50 of the niobium composite metal oxide －１ and the number particle diameter D Ｎ 10 of the niobium composite metal oxide satisfy 5 ≦ Dv50 －１ / D Ｎ 10 ≦ 23 The specific surface area BET of the niobium composite metal oxide １ is 0.2m ２ / g to 1.8m ２ / g, The volume-average particle size Dv50-2 of the aforementioned graphite is 10 μm to 23 μm. The volume-average particle diameter Dv50-1 of the niobium composite metal oxide and the volume-average particle diameter Dv50-2 of the graphite satisfy 2 ≤ Dv50-2 / Dv50-1 ≤ 5.

3. The ratio of the mass of the niobium composite metal oxide to the mass of the graphite is (30-50):(50-70). Negative pole piece.

2. The structure of the niobium composite metal oxide is at least one of the following: a Wazley-Ross cross-sectional structure and a tungsten bronze structure. The negative electrode piece according to claim 1.

3. The specific surface area of ​​the aforementioned graphite BET ２ is 0.5m ２ / g to 10m ２ / g is The negative electrode piece according to claim 1.

4. The compressed density of the negative electrode piece is 1.6 g / cm³. ３ ~3.6 g / cm ３ That is, The negative electrode piece according to claim 1.

5. A negative electrode piece comprising the negative electrode piece described in any one of claims 1 to 4, Electrochemical apparatus.

6. The electrochemical apparatus described in claim 5 includes, electronic equipment.

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