Active material, negative pole piece, battery and electric equipment

Abstract

The invention relates to an active material, a negative pole piece, a battery and electric equipment. The active material has a first stability coefficient alpha 1 and a second stability coefficient alpha 2, and the active material satisfies the relational expression: alpha 1 = Dv50-Dv50 ', 0 < = alpha 1 < = 1 [mu] m; and a relational expression alpha2 = Dn50-Dn50 'is satisfied, and alpha2 is greater than or equal to 0 and less than or equal to 0.04 [mu] m; wherein Dv50 is the particle size of the active material measured when the cumulative volume fraction in the volume-based distribution reaches 50%, and Dv50'is the particle size of the active material measured when the cumulative volume fraction in the volume-based distribution reaches 50% after a 5-ton powder compaction test; dn50 is the particle size of the active material measured when the cumulative number fraction in the number-based distribution reaches 50%, and Dn50'is the particle size of the active material measured when the cumulative number fraction in the number-based distribution reaches 50% after a 5-ton powder compaction test.

Description

Technical Field

[0001] The present application relates to the technical field of batteries, and particularly relates to an active material, a negative electrode sheet, a battery, and an electrical device. Background Art

[0002] With the continuous development of energy storage technologies, lithium-ion batteries are widely used in various fields, and higher requirements are also put forward for the cycling performance of lithium-ion batteries. Therefore, how to improve the cycling stability of lithium-ion batteries to extend the service life of the batteries is an urgent problem to be solved. Summary of the Invention

[0003] In view of this, the present application provides an active material, a negative electrode sheet, a battery, and an electrical device. The active material has good compressive properties, so that the battery has good cycling stability.

[0004] The present application provides an active material. The active material has a first stability coefficient α1 and a second stability coefficient α2. Then the active material satisfies the relational expressions: α1 = Dv50 - Dv50', 0 ≤ α1 ≤ 1 μm; and satisfies the relational expression α2 = Dn50 - Dn50', 0 ≤ α2 ≤ 0.04 μm. Wherein, Dv50 is the particle size of the active material measured when the cumulative volume fraction in the volume-based distribution reaches 50%, Dv50' is the particle size of the active material measured when the cumulative volume fraction in the volume-based distribution reaches 50% after a 5-ton powder compaction test; Dn50 is the particle size of the active material measured when the cumulative number fraction in the number-based distribution reaches 50%, Dn50' is the particle size of the active material measured when the cumulative number fraction in the number-based distribution reaches 50% after a 5-ton powder compaction test.

[0005] Further, the active material is selected from at least one of artificial graphite and natural graphite, and the graphitization degree G of the active material ranges from: 93% ≤ G ≤ 96%.

[0006] Further, the active material includes primary particles and secondary particles. The secondary particles are aggregates of primary particles. The particle size of the primary particles is smaller than that of the secondary particles. In the active material, the mass fraction W1 of the primary particles ranges from: 40% ≤ W1 ≤ 95%.

[0007] Further, the difference γ between the specific surface area of the primary particles and the specific surface area of the secondary particles ranges from: 0.3 m 2 / g ≤ γ ≤ 0.6 m 2 / g.

[0008] Further, the difference β between the first Coulomb efficiency of the primary particles and the first Coulomb efficiency of the secondary particles ranges from: 0 ≤ β ≤ 0.6%.

[0009] Further, the active material satisfies the range: 10 μm ≤ Dv50 ≤ 15 μm.

[0010] Further, the specific surface area S of the active material ranges from: 1.0 m 2 / g ≤ S ≤ 2.0 m 2 / g.

[0011] Further, the gram capacity C of the active material ranges from: 340 mAh / g ≤ C ≤ 360 mAh / g.

[0012] This application provides a negative electrode sheet, which includes: a negative electrode material layer and a negative electrode current collector layer. The negative electrode material layer is disposed on at least one surface of the negative electrode current collector layer, and the negative electrode material layer includes the active material provided by this application.

[0013] This application provides a battery, which includes: the negative electrode sheet provided by this application, a separator, a positive electrode sheet, and an electrolyte. The separator is disposed on one side of the negative electrode sheet; the positive electrode sheet is disposed on the side of the separator away from the negative electrode sheet; the electrolyte includes a film-forming additive, and the film-forming additive includes a cyclic carbonate additive.

[0014] Further, in the electrolyte, the mass fraction of the film-forming additive is W2, and the battery satisfies the relationship: 0 ≤ W2 × α1 × α2 ≤ 4 × 10 -5 μm 2 .

[0015] Further, in the electrolyte, the mass fraction W2 of the film-forming additive ranges from: 0.01% ≤ W2 ≤ 1%.

[0016] This application provides an electrical device, which includes: a device body and the battery provided by this application, and the battery powers the device body.

[0017] In this application, the first stability coefficient α1 represents the difference in the particle size volume distribution coefficient of the active material before and after powder pressing, and the second stability coefficient α2 represents the value of the particle size number distribution coefficient of the active material before and after powder pressing. Both the first stability coefficient and the second stability coefficient can characterize the compressive performance of the active material. After being compacted by 5 tons of powder, the compaction stage after the active material is applied to the negative electrode sheet can be simulated. When both the first stability coefficient and the second stability coefficient are small, it indicates that the active material has good compressive performance. The active material can still maintain a relatively complete structure after being powder-compacted, avoiding changes in the structure due to the rupture of the active material, so as to avoid exposing more active reaction sites, thereby reducing the side reaction between the electrolyte in the battery and the active material, which is beneficial to slowing down the attenuation of the battery, thereby improving the cycle performance of the battery and extending the service life of the battery. Specifically, when the first stability coefficient α1 satisfies the range of 0 ≤ α1 ≤ 1 μm and the second stability coefficient α2 satisfies the range of 0 ≤ α2 ≤ 0.04 μm, both the first stability coefficient α1 and the second stability coefficient α2 are within a reasonable range, and the active material has good structural stability. When the active material is applied to the negative electrode sheet and assembled in the battery, after the negative electrode sheet is compacted, the active material still has good structural stability, and the active material has good compressive performance, avoiding excessive exposure of active sites of the active material, which leads to the attenuation of the battery. Therefore, when the active material is applied to the negative electrode sheet and assembled in the battery, the battery has good cycle stability and a long service life. When the first stability coefficient is too large and / or the second stability coefficient is too large, it proves that the degree of rupture of the active material after powder compaction is large, the structure of the active material collapses during the powder pressing process, and the compressive performance of the active material is too poor. As a result, when the active material is applied to the negative electrode sheet and compacted, the active material may expose too many active sites, thereby aggravating the attenuation of the battery and shortening the cycle life of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for the implementation will be briefly introduced below. Obviously, the drawings in the following description are some embodiments of the present application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0019] Figure 1 It is a schematic cross-sectional structure diagram of a negative electrode sheet according to an embodiment of the present application;

[0020] Figure 2 It is a schematic cross-sectional structure diagram of a battery according to an embodiment of the present application;

[0021] Figure 3For implementing the comparison chart of the cycling effects of Battery 1 and Comparative Battery 1;

[0022] Figure 4 The structural schematic diagram of the electrical device according to an embodiment of the present application;

[0023] Figure 5 The circuit block diagram of the electrical device according to an embodiment of the present application.

[0024] Explanation of reference numerals:

[0025] 100 - negative electrode tab, 110 - negative electrode material layer, 111 - active material, 120 - negative electrode current collector layer, 200 - battery, 210 - separator, 220 - positive electrode tab, 230 - electrolyte, 300 - electrical device, 310 - device body. Detailed implementation manners

[0026] Next, the technical solutions in the embodiments of the present application will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present application.

[0027] The terms "first", "second", etc. in the specification and claims of the present application and the above-mentioned accompanying drawings are used to distinguish different objects, rather than to describe a specific order. In addition, the terms "comprising" and "having" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device that includes a series of steps or units is not limited to the listed steps or units, but optionally further includes steps or units not listed, or optionally further includes other steps or units inherent to these processes, methods, products or devices.

[0028] Referring to "embodiment" or "embodiment manner" herein means that a specific feature, structure or characteristic described in connection with the embodiment or embodiment manner may be included in at least one embodiment of the present application. The phrase appears in various positions in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment mutually exclusive with other embodiments. Those skilled in the art explicitly and implicitly understand that the embodiments described herein can be combined with other embodiments.

[0029] With the continuous development of energy storage technologies, lithium-ion batteries are widely used in various fields, and higher requirements are also put forward for the cycling performance of lithium-ion batteries. In a lithium-ion battery, if the stability of the active material is too poor, it may lead to the attenuation of the battery, thereby affecting the cycling stability of the battery. Therefore, how to improve the cycling stability of lithium-ion batteries to extend the service life of the battery is an urgent problem to be solved.

[0030] Please refer to Figure 1 , this application provides an active material 111. The active material 111 has a first stability coefficient α1 and a second stability coefficient α2. Then the active material 111 satisfies the relational expressions: α1 = Dv50 - Dv50’, 0 ≤ α1 ≤ 1 μm; and satisfies the relational expression α2 = Dn50 - Dn50’, 0 ≤ α2 ≤ 0.04 μm; where Dv50 is the particle size of the active material 111 measured when the cumulative volume fraction in the volume-based distribution reaches 50%, Dv50’ is the particle size of the active material 111 measured when the cumulative volume fraction in the volume-based distribution reaches 50% after a 5-ton powder compaction test; Dn50 is the particle size of the active material 111 measured when the cumulative number fraction in the number-based distribution reaches 50%, Dn50’ is the particle size of the active material 111 measured when the cumulative number fraction in the number-based distribution reaches 50% after a 5-ton powder compaction test.

[0031] Specifically, the value of α1 can be, but is not limited to, 0, 0.1 μm, 0.2 μm, 0.3 μm, 0.4 μm, 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, and 1 μm, etc.

[0032] Specifically, the value of α2 can be, but is not limited to, 0, 0.001 μm, 0.005 μm, 0.01 μm, 0.015 μm, 0.02 μm, 0.025 μm, 0.03 μm, 0.035 μm, and 0.04 μm, etc.

[0033] It can be understood that the active material 111 is applied to the negative electrode plate 100 and assembled in the battery 200. The active material 111 is used to store and release active ions. The battery 200 further includes an electrolyte 230, and the electrolyte 230 is used to output active ions. When the battery 200 is a lithium-ion battery, the active ions are lithium ions.

[0034] Understandably, the first stability coefficient is the particle size stability coefficient, which characterizes the difference in the particle size of the active material 111 before and after powder compaction, and is an important parameter for describing whether the active material 111 breaks before and after powder compaction. The larger the first stability coefficient, the weaker the compressive capacity of the active material 111; conversely, the smaller the first stability coefficient, the stronger the compressive capacity of the active material 111.

[0035] Understandably, the second stability coefficient is the quantity distribution coefficient, which characterizes the difference in the particle size of the active material 111 before and after powder compaction, and is an important parameter for describing whether the active material 111 breaks before and after powder compaction. The larger the second stability coefficient, the weaker the compressive capacity of the active material 111; conversely, the smaller the second stability coefficient, the stronger the compressive capacity of the active material 111.

[0036] Understandably, after compaction of 5 tons of powder, the compaction stage after the active material 111 is applied to the negative electrode sheet 100 can be simulated, and Dv50’ and Dn50’ are used to characterize the particle size of the active material 111 after the active material 111 is applied to the negative electrode sheet 100 and compacted.

[0037] In this embodiment, the first stability coefficient α1 represents the difference in the particle size volume distribution coefficient of the active material 111 before and after powder pressing, and the second stability coefficient α2 represents the value of the particle size number distribution coefficient of the active material 111 before and after powder pressing. Both the first stability coefficient and the second stability coefficient can characterize the compressive performance of the active material 111. After being compacted by 5 tons of powder, the compaction stage after the active material 111 is applied to the negative electrode sheet 100 can be simulated. When both the first stability coefficient and the second stability coefficient are small, it indicates that the active material 111 has good compressive performance. The active material 111 can still maintain a relatively complete structure after powder compaction, avoiding changes in the structure due to the rupture of the active material 111, so as to avoid exposing more active reaction sites, thereby reducing the side reaction between the electrolyte 230 in the battery 200 and the active material 111, which is beneficial to slowing down the attenuation of the battery 200, thereby improving the cycle performance of the battery 200 and extending the service life of the battery 200. Specifically, when the first stability coefficient α1 satisfies the range 0 ≤ α1 ≤ 1 μm and the second stability coefficient α2 satisfies the range 0 ≤ α2 ≤ 0.04 μm, both the first stability coefficient α1 and the second stability coefficient α2 satisfy a reasonable range, and the active material 111 has good structural stability. When the active material 111 is applied to the negative electrode sheet 100 and assembled in the battery 200, after the negative electrode sheet 100 is compacted, the active material 111 still has good structural stability, and the active material 111 has good compressive performance, avoiding the exposure of too many active sites of the active material 111 and resulting in the attenuation of the battery 200. Therefore, when the active material 111 is applied to the negative electrode sheet 100 and assembled in the battery 200, the battery 200 has good cycle stability and a long service life. When the first stability coefficient is too large and / or the second stability coefficient is too large, it proves that the degree of rupture of the active material 111 after powder compaction is large, the structure of the active material 111 collapses during the powder pressing process, and the compressive performance of the active material 111 is too poor. As a result, when the active material 111 is applied to the negative electrode sheet 100 and compacted, the active material 111 may expose too many active sites, thereby exacerbating the attenuation of the battery 200 and shortening the cycle life of the battery 200.

[0038] Most preferably, the value of the first stability coefficient α1 is 0, and the value of the second stability coefficient α2 is 0.

[0039] In some embodiments, the active material 111 is selected from at least one of artificial graphite and natural graphite, and the graphitization degree G of the active material 111 ranges from 93% ≤ G ≤ 96%.

[0040] Specifically, the graphitization degree value of the active material 111 can be, but is not limited to, 93%, 93.2%, 93.5%, 93.7%, 94%, 94.2%, 94.5%, 94.7%, 94.8%, 95%, 95.2%, 95.5%, 95%, etc.

[0041] It can be understood that the graphitization degree of the active material 111 is an index for measuring the degree to which carbon atoms form a close-packed hexagonal graphite crystal structure. The closer the lattice size is to the lattice constant of ideal graphite, the higher the graphitization degree.

[0042] In this embodiment, the active material 111 is selected from at least one of artificial graphite and natural graphite. There is a lamellar-like structure inside the active material 111, which is conducive to the insertion and extraction of active ions, so that the active material 111 has good performance. In this embodiment, the graphitization degree of the active material 111 can characterize the regularity of the active material 111. The higher the graphitization degree of the active material 111, the fewer the stress concentration sites on the surface of the active material 111 and the higher the orientation degree of the active material 111, and the active material 111 has better compressive characteristics. When the graphitization degree G of the active material 111 satisfies the range of 93% ≤ G ≤ 96%, the graphitization degree of the active material 111 is within a reasonable range. On the one hand, the orientation degree of the active material 111 is within a reasonable range, so that there are fewer stress concentration sites on the surface of the active material 111, and the compressive performance of the active material 111 is better, facilitating the first stability coefficient α1 of the active material 111 to satisfy the range of 0 ≤ α1 ≤ 1 μm and the second stability coefficient α2 to satisfy the range of 0 ≤ α2 ≤ 0.04 μm. When the active material 111 is applied to the negative electrode plate 100 and assembled in the battery 200, the active material 111 has good compressive performance. After the active material 111 is powder-compacted, it can still maintain a relatively complete structure, avoiding the change of the structure due to the rupture of the active material 111, so as to avoid exposing more active reaction sites, thereby reducing the side reaction between the electrolyte 230 in the battery 200 and the active material 111, which is conducive to slowing down the attenuation of the battery 200, thereby improving the cycle performance of the battery 200 and prolonging the service life of the battery 200. On the other hand, the lithium ions have good transport performance in the active material 111, which is conducive to the battery 200 having a high energy efficiency. When the graphitization degree of the active material 111 is too large, in the highly oriented active material 111, the graphite lamellae of the active material 111 are arranged too orderly, resulting in a single and narrow diffusion path for active ions during the insertion and extraction processes, which will increase the diffusion resistance of lithium ions and reduce the charge-discharge rate and rate performance of the battery 200. When the graphitization degree of the active material 111 is too small, correspondingly, the orientation degree of the active material 111 is low, which may lead to too large first stability coefficient α1 and / or second stability coefficient α2 of the active material 111, and the compressive performance of the active material 111 is too poor. When the active material 111 is applied to the negative electrode plate 100 and compacted, the active material 111 may expose too many active sites, thereby exacerbating the attenuation of the battery 200 and shortening the cycle life of the battery 200.

[0043] Optionally, during the preparation of the active material 111, the graphitization degree G of the active material 111 can be adjusted by adjusting the power transmission amount and power transmission time of the graphitization process. Specifically, the power transmission amount of the graphitization process is controlled at 5000 kWh / t to 7000 kWh / t, the power transmission time is controlled at 40 h to 70 h, and the packing depth from the upper surface of the graphitization furnace is controlled at 60 cm to 130 cm.

[0044] Specifically, the value of the power transmission amount of the graphitization process can be, but is not limited to, 5000 kWh / t, 5200 kWh / t, 5500 kWh / t, 5800 kWh / t, 6000 kWh / t, 6200 kWh / t, 6500 kWh / t, 6800 kWh / t, 7000 kWh / t, etc.

[0045] Specifically, the value of the power transmission time of the graphitization process can be, but is not limited to, 40 h, 42 h, 45 h, 48 h, 50 h, 52 h, 55 h, 58 h, 60 h, 62 h, 65 h, 68 h, 70 h, etc.

[0046] In this embodiment, when the power transmission amount during the graphitization process is controlled within 5000 kWh / t to 7000 kWh / t, the power transmission time is controlled within 40 h to 70 h, and the packing depth from the upper surface of the graphitization furnace is controlled within 60 cm to 130 cm, the graphitization degree G of the active material 111 can satisfy the range of 93% ≤ G ≤ 96%, so that there are fewer stress concentration sites on the surface of the active material 111, and the compressive performance of the active material 111 is better, facilitating the first stability coefficient α1 of the active material 111 to satisfy the range of 0 ≤ α1 ≤ 1 μm, and the second stability coefficient α2 to satisfy the range of 0 ≤ α2 ≤ 0.04 μm. When the active material 111 is applied to the negative electrode tab 100 and assembled in the battery 200, the active material 111 has better compressive performance. After the active material 111 is powder-compacted, it can still maintain a relatively complete structure, avoiding the change of the structure due to the rupture of the active material 111, so as to avoid exposing more active reaction sites, thereby reducing the side reaction between the electrolyte 230 in the battery 200 and the active material 111, which is beneficial to slowing down the attenuation of the battery 200, thereby improving the cycle performance of the battery 200 and extending the service life of the battery 200. When the power transmission amount during the graphitization process is lower than 5000 kWh / t and / or the power transmission time is less than 40 h, the graphitization degree of the active material 111 will be too low, resulting in too poor compressive performance and too low orientation degree of the active material 111, and too many active sites may be exposed during the compaction process. When the power transmission amount during the graphitization process is higher than 7000 kWh / t and / or the power transmission time is greater than 70 h, the graphitization degree of the active material 111 is difficult to continue to increase, and the manufacturing cost is increased. In addition, if the packing depth is lower than 60 cm, it is easy to cause oxidation of the active material 111, introducing more defects and reducing the compressive characteristics of the active material 111; if the packing depth is higher than 130 cm, the specific surface area of the active material 111 is too low, and it is easy to cause poor kinetic performance of the active material 111.

[0047] Optionally, in some embodiments, the active material 111 includes sulfur, and the sulfur content W3 of the active material 111 ranges from 0.3% ≤ W3 ≤ 2.5%.

[0048] Specifically, the value of the sulfur content W3 of the active material 111 can be, but is not limited to, 0.3%, 0.4%, 0.5%, 0.6%, 0.8%, 1%, 1.1%, 1.3%, 1.5%, 1.6%, 1.8%, 2%, 2.1%, 2.2%, 2.4% and 2.5%, etc.

[0049] In this embodiment, when the sulfur content W3 of the active material 111 satisfies the range of 0.3% ≤ W3 ≤ 2.5%, the sulfur content of the active material 111 is within a reasonable range, and the sulfur content of the active material 111 is relatively low to avoid sulfur affecting the nucleation process of graphite, thereby avoiding affecting the regularity of the active material 111, so that the active material 111 has better compressive properties, and thus the first stability coefficient α1 of the active material 111 satisfies the range of 0 ≤ α1 ≤ 1 μm, and the second stability coefficient α2 satisfies the range of 0 ≤ α2 ≤ 0.04 μm. When the active material 111 is applied to the negative electrode sheet 100 and compacted, the active material 111 still has good structural integrity to avoid the active material 111 exposing too many active sites, thereby slowing down the attenuation of the battery 200 and prolonging the cycle life of the battery 200. When the sulfur content of the active material 111 is too high, excessive sulfur will increase the defects of the flaky structure of graphite, thereby reducing the regularity of the active material 111, making the first stability coefficient and the second stability coefficient of the active material 111 too large, which is not conducive to the improvement of the cycle performance of the battery 200. When the sulfur content of the active material 111 is too low, it increases the processing difficulty of the raw materials of the active material 111, thereby increasing the processing cost of the active material 111.

[0050] Optionally, in some embodiments, the active material 111 only includes primary particles and does not include secondary particles; in other embodiments, the active material 111 only includes secondary particles and does not include primary particles. In other words, the active material 111 includes at least one of the primary particles and the secondary particles.

[0051] In some embodiments, the active material 111 includes primary particles and secondary particles. The secondary particles are aggregates of primary particles, and the particle size of the primary particles is smaller than that of the secondary particles. In the active material 111, the range of the mass fraction W1 of the primary particles is: 40% ≤ W1 ≤ 95%.

[0052] Specifically, the value of the mass fraction W1 of the primary particles can be, but is not limited to, 40%, 42%, 45%, 48%, 50%, 52%, 55%, 60%, 65%, 68%, 70%, 75%, 78%, 80%, 85%, 90%, and 95%, etc.

[0053] It can be understood that in the active material 111, the mass fraction of the primary particles is the ratio of the sum of the mass fractions of the primary particles to the mass of the active material 111.

[0054] It can be understood that the number of the primary particles is multiple, the number of the secondary particles is multiple, and the multiple primary particles and the multiple secondary particles are mixed and dispersed.

[0055] In this embodiment, the active material 111 includes primary particles and secondary particles, and the particle size of the primary particles is smaller than that of the secondary particles. The mixing of the primary particles and the secondary particles can enable the active material 111 to have a high tap density, so that the battery 200 has a high energy density. When the mass fraction W1 of the primary particles satisfies the range of 40% ≤ W1 ≤ 95%, the mass fractions of the primary particles and the secondary particles are both within a reasonable range. The primary particles and the secondary particles cooperate with each other to enable the active material 111 to have good compressive properties and also enable the active material 111 to have good electrical properties. When the active material 111 is applied to the negative electrode sheet 100 and assembled into the battery 200, the battery 200 has good energy efficiency and rate performance.

[0056] In some embodiments, the range of the difference γ between the specific surface area of the primary particles and the specific surface area of the secondary particles is: 0.3 m 2 / g ≤ γ ≤ 0.6 m 2 / g.

[0057] Specifically, the value of γ can be, but is not limited to, 0.3 m 2 / g, 0.32 m 2 / g, 0.35 m 2 / g, 0.38 m 2 / g, 0.4 m 2 / g, 0.42 m 2 / g, 0.45 m 2 / g, 0.5 m 2 / g, 0.52 m 2 / g, 0.53 m 2 / g, 0.54 m 2 / g, 0.56 m 2 / g, 0.58 m 2 / g and 0.6 m 2 / g, etc.

[0058] In this embodiment, when the difference γ between the specific surface area of the primary particles and the specific surface area of the secondary particles satisfies the range of 0.3 m 2 / g ≤ γ ≤ 0.6 m 2When it is [specific value] / g, the specific surface area of the primary particles and the specific surface area of the secondary particles are both within a reasonable range, so that the active material 111 has good compressive properties, which is beneficial to achieving that the active material 111 has a small first stability coefficient and a second stability coefficient, and the active material 111 has good structural stability. When the active material 111 is applied to the negative electrode sheet 100 and assembled in the battery 200, after the negative electrode sheet 100 is compacted, the active material 111 still has good structural stability, and the active material 111 has good compressive properties, avoiding excessive exposure of active sites of the active material 111 and resulting in the attenuation of the battery 200. Thus, when the active material 111 is applied to the negative electrode sheet 100 and assembled in the battery 200, the battery 200 has good cycle stability and a long service life. Moreover, the primary particles and the secondary particles cooperate with each other, so that the active material 111 has enough active sites, which is convenient for the insertion and extraction of active ions, and at the same time, it can avoid excessive consumption of the electrolyte 230 in the battery 200 due to too many active sites of the active material 111, and can further improve the cycle performance of the battery 200. When the difference between the specific surface area of the primary particles and the specific surface area of the secondary particles is too large, in other words, the specific surface area of the primary particles is too large, and / or the specific surface area of the secondary particles is too small, the synergistic effect between the primary particles and the secondary particles is reduced, the uniformity of the active material 111 is reduced, and the probability of side reactions between the electrolyte 230 and the active material 111 may increase, reducing the cycle stability of the battery 200. When the difference between the specific surface area of the primary particles and the specific surface area of the secondary particles is too small, the primary particles and the secondary particles are difficult to play a synergistic role, and the performance of the active material 111 in intercalating and deintercalating lithium ions is poor. Thus, when the active material 111 is applied to the negative electrode sheet 100, the energy efficiency of the battery 200 is low and the rate performance is poor.

[0059] In some embodiments, the range of the difference β between the first Coulomb efficiency of the primary particles and the first Coulomb efficiency of the secondary particles is: 0 ≤ β ≤ 0.6%.

[0060] Specifically, the value of β can be but is not limited to 0, 0.05%, 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, 0.36%, 0.4%, 0.45%, 0.5%, 0.55% and 0.6%, etc.

[0061] It can be understood that the secondary particles are aggregates of the primary particles, and the secondary particles are bonded by multiple primary particles. Then, the impedance of active ion transmission in the secondary particles is greater than the impedance of active ion transmission in the primary particles, and the first Coulomb efficiency of the primary particles is greater than the first Coulomb efficiency of the secondary particles.

[0062] In this embodiment, when the difference β between the first Coulombic efficiency of the primary particles and the first Coulombic efficiency of the secondary particles satisfies the range 0 ≤ β ≤ 0.6%, and the first Coulombic efficiency of the primary particles and the first Coulombic efficiency of the secondary particles are both within a reasonable range, the primary particles and the secondary particles are compounded so that the active material 111 has a relatively high first Coulombic efficiency. When the active material 111 is applied to the negative electrode sheet 100 and assembled into the battery 200, the battery 200 has a relatively high energy utilization rate. When the value of β is too large, the difference between the first Coulombic efficiency of the primary particles and the first Coulombic efficiency of the secondary particles is too large. In other words, the first Coulombic efficiency of the secondary particles is too small, resulting in a relatively low first Coulombic efficiency of the active material 111. When the active material 111 is applied to the negative electrode sheet 100 and assembled into the battery 200, the energy utilization rate of the battery 200 is relatively low.

[0063] In some embodiments, the active material 111 satisfies the range: 10 μm ≤ Dv50 ≤ 15 μm.

[0064] It can be understood that Dv50 is the particle size of the active material 111 measured when the cumulative volume fraction in the volume-based distribution reaches 50%, and Dv50 is the median particle size of the active material 111.

[0065] Specifically, the value of Dv50 can be, but is not limited to, 10 μm, 10.5 μm, 10.8 μm, 11 μm, 11.5 μm, 11.8 μm, 12 μm, 12.5 μm, 13 μm, 13.5 μm, 14 μm, 14.5 μm, 15 μm, etc.

[0066] It can be understood that when the active material 111 includes primary particles and secondary particles, the median particle size of the primary particles and the median particle size of the secondary particles both satisfy the range of 10 μm to 15 μm.

[0067] In this embodiment, when the active material 111 satisfies the range 10 μm ≤ Dv50 ≤ 15 μm and the value of Dv50 is within a reasonable range, after the active material 111 is applied to the negative electrode sheet 100 and compacted, the active material 111 can still maintain good structural integrity to avoid excessive exposure of active sites of the active material 111 and exacerbating the side reaction between the electrolyte 230 and the active material 111, so that the battery 200 has good cycle stability.

[0068] In some embodiments, the range of the specific surface area S of the active material 111 is: 1.0m 2 / g ≤ S ≤ 2.0m 2 / g.

[0069] Specifically, the value of the specific surface area S of the active material 111 can be, but is not limited to, 1.0 m 2 / g, 1.1 m 2 / g, 1.2 m 2 / g, 1.3 m 2 / g, 1.4 m 2 / g, 1.5 m 2 / g, 1.6 m 2 / g, 1.7 m 2 / g, 1.8 m 2 / g, 1.9 m 2 / g, and 2 m 2 / g, etc.

[0070] It can be understood that if the active material 111 has a low first stability coefficient and a low second stability coefficient, then before and after powder compaction of the active material 111, the change in the specific surface area of the active material 111 is small. In other words, before and after compaction, the specific surface area of the active material 111 satisfies the range of 1.0 m 2 / g ≤ S ≤ 2.0 m 2 / g.

[0071] In this embodiment, when the specific surface area S of the active material 111 satisfies the range of 1.0 m 2 / g ≤ S ≤ 2.0 m 2 / g, the specific surface area of the active material 111 is within a reasonable range, so the active sites exposed by the active material 111 are within a reasonable range. In addition, the first stability coefficient and the second stability coefficient of the active material 111 are both within a reasonable range. Then, when the active material 111 is applied to the negative electrode plate 100 and powder-compacted, the active material 111 still has good structural stability to avoid exposing more active reaction sites, thereby reducing the side reaction between the electrolyte 230 in the battery 200 and the active material 111, which is beneficial to slowing down the attenuation of the battery 200, thereby improving the cycle performance of the battery 200 and prolonging the service life of the battery 200. When the specific surface area S of the active material 111 is too large, when the active material 111 is applied to the negative electrode plate 100 and assembled in the battery 200, the side reaction between the active material 111 and the electrolyte 230 is aggravated, resulting in poor cycle stability of the battery 200. When the specific surface area S of the active material 111 is too small, the impedance of lithium ions to escape from or embed into the active material 111 is increased, thereby reducing the cycle performance of the battery 200.

[0072] In some embodiments, the range of the specific capacity C of the active material 111 is: 340 mAh / g ≤ C ≤ 360 mAh / g.

[0073] Specifically, the value of the gram capacity C of the active material 111 can be, but is not limited to, 340 mAh / g, 342 mAh / g, 345 mAh / g, 350 mAh / g, 352 mAh / g, 355 mAh / g, 358 mAh / g, 360 mAh / g, etc.

[0074] In this embodiment, when the gram capacity C of the active material 111 satisfies the range 340 mAh / g ≤ C ≤ 360 mAh / g, the gram capacity of the active material 111 is within a reasonable range, and the active material 111 has a relatively high gram capacity. When the active material 111 is applied to the negative electrode plate 100 and assembled in the battery 200, the negative electrode plate 100 has a relatively high energy density, and the battery 200 has a relatively high capacity and energy efficiency.

[0075] This application provides a negative electrode plate 100, which includes: a negative electrode material layer 110 and a negative electrode current collector layer 120. The negative electrode material layer 110 is disposed on at least one surface of the negative electrode current collector layer 120, and the negative electrode material layer 110 includes the active material 111 provided by this application.

[0076] Optionally, the negative electrode material layer 110 is disposed on at least one surface of the negative electrode current collector layer 120. It can be that the negative electrode material layer 110 is disposed on one surface of the negative electrode current collector layer 120, or the negative electrode material layer 110 is disposed on two opposite surfaces of the negative electrode current collector layer 120.

[0077] In this embodiment, the negative electrode plate 100 includes the active material 111 provided by this application. The active material 111 satisfies the relational expressions: α1 = Dv50 - Dv50', 0 ≤ α1 ≤ 1 μm; and satisfies the relational expression α2 = Dn50 - Dn50', 0 ≤ α2 ≤ 0.04 μm. The active material 111 has a relatively small first stability coefficient and a relatively small second stability coefficient. The active material 111 has good compressive properties. After the active material 111 is powder-compacted, it can still maintain a relatively complete structure, avoiding the change of the structure due to the rupture of the active material 111, so as to avoid exposing more active reaction sites, thereby reducing the side reaction between the electrolyte 230 in the battery 200 and the active material 111, which is beneficial to slowing down the attenuation of the battery 200, thereby improving the cycle performance of the battery 200 and extending the service life of the battery 200.

[0078] Please refer to Figure 2, this application provides a battery 200, which includes: a negative electrode sheet 100 provided by this application, a separator 210, a positive electrode sheet 220, and an electrolyte 230. The separator 210 is disposed on one side of the negative electrode sheet 100; the positive electrode sheet 220 is disposed on the side of the separator 210 away from the negative electrode sheet 100; the electrolyte 230 includes a film-forming additive, and the film-forming additive includes a cyclic carbonate additive.

[0079] It can be understood that the positive electrode sheet 220, the separator 210, and the negative electrode sheet 100 are stacked.

[0080] In this embodiment, the electrolyte 230 is used to infiltrate at least part of the positive electrode sheet 220, at least part of the separator 210, and at least part of the negative electrode sheet 100 to facilitate the transmission of active ions. Among them, the electrolyte 230 includes a film-forming additive, and the film-forming additive includes a cyclic carbonate additive. The cyclic carbonate additive has higher reducibility than other additives in the electrolyte 230, so that the cyclic carbonate additive preferentially forms a film on the surface of the negative electrode sheet 100, which is beneficial to maintaining the interfacial stability between the electrolyte 230 and the negative electrode sheet 100. On the one hand, the structure of the active material 111 has changed to a certain extent after powder compaction, but it still has good compressive performance to avoid exposing too many active sites. On the other hand, the interfacial film preferentially formed by the cyclic carbonate additive on the surface of the negative electrode sheet 100 further protects the active material 111 to further slow down the side reaction between the active material 111 and the electrolyte 230. In other words, the cyclic carbonate additive and the active material 111 have a synergistic effect to greatly slow down the side reaction between the active material 111 and the electrolyte 230, so that the battery 200 has good cycle stability and the battery 200 has a long service life.

[0081] Optionally, the cyclic carbonate additive is selected from at least one of vinylene carbonate, ethylene carbonate, butylene carbonate, and diethyl carbonate.

[0082] In some embodiments, in the electrolyte 230, the mass fraction of the film-forming additive is W2, and the battery 200 satisfies the relationship: 0 ≤ W2 × α1 × α2 ≤ 4 × 10 -5 μm 2 .

[0083] Specifically, the value of W2 × α1 × α2 can be, but is not limited to, 0, 0.06 × 10 -5 μm 2 , 0.12 × 10 -5 μm 2 , 0.35 × 10-5 μm 2 , 0.46×10 -5 μm 2 , 0.68×10 -5 μm 2 , 0.8×10 -5 μm 2 , 1×10 -5 μm 2 , 1.2×10 -5 μm 2 , 1.5×10 -5 μm 2 , 2×10 -5 μm 2 , 2.3×10 -5 μm 2 , 2.5×10 -5 μm 2 , 2.8×10 -5 μm 2 , 3×10 -5 μm 2 , 3.1×10 -5 μm 2 , 3.5×10 -5 μm 2 and 4×10 -5 μm 2 wait.

[0084] In this embodiment, when the battery 200 satisfies the relationship 0≤W2×α1×α2≤4×10 -5 μm 2When the mass fraction of the film-forming additive, the value of α1, and the value of α2 are all within a reasonable range, the film-forming additive and the active material 111 have a good synergistic effect to slow down the side reaction between the electrolyte 230 and the negative electrode sheet 100, so that the battery 200 has both good cycle stability and high charge-discharge efficiency. On the one hand, the first stability coefficient α1 and the second stability coefficient α2 of the active material 111 are within a reasonable range, so that the active material 111 has good structural stability. After the active material 111 is applied to the negative electrode sheet 100 and compacted, the active material 111 still has good structural stability, and the active material 111 has good compressive performance, avoiding excessive exposure of active sites of the active material 111 and resulting in the attenuation of the battery 200. Therefore, when the active material 111 is applied to the negative electrode sheet 100 and assembled in the battery 200, the battery 200 has good cycle stability and a long service life. On the other hand, the mass fraction of the film-forming additive is within a reasonable range. The film-forming additive can preferentially form a film on the surface of the negative electrode sheet 100 to protect the active material 111 whose structure has changed after powder pressing, thereby slowing down the side reaction between the active material 111 and the electrolyte 230, ensuring that the active material 111 can exert its electrical properties, and making the battery 200 have good cycle stability. When the value of W2×α1×α2 is too large, the first stability coefficient α1 and the second stability coefficient α2 of the active material 111 are too large, or the mass fraction of the film-forming additive is too large. When the first stability coefficient α1 and / or the second stability coefficient α2 of the active material 111 is too large, the degree of rupture of the active material 111 after powder compaction is large, the structure of the active material 111 collapses and is severely damaged during the powder pressing process, and the compressive performance of the active material 111 is too poor. Therefore, when the active material 111 is applied to the negative electrode sheet 100 and compacted, the active material 111 may expose too many active sites, thereby aggravating the attenuation of the battery 200 and shortening the cycle life of the battery 200. When the mass fraction of the film-forming additive is too large, it may increase the internal resistance of the battery 200, thereby reducing the charge-discharge efficiency of the battery 200. When the value of W2×α1×α2 is too large, if the first stability coefficient and the second stability coefficient of the active material 111 are too large, the active material 111 is severely damaged during the compaction process. Even if a large amount of film-forming additive is added, the dynamic balance of the interface film cannot be balanced. In addition, when the mass fraction of the film-forming additive is too large, it will also deteriorate the electrical properties of the battery 200.

[0085] In some embodiments, in the electrolyte 230, the range of the mass fraction W2 of the film-forming additive is: 0.01% ≤ W2 ≤ 1%.

[0086] Specifically, the value of the mass fraction W2 of the film-forming additive can be, but is not limited to, 0.01%, 0.05%, 0.1%, 0.15%, 0.18%, 0.2%, 0.22%, 0.25%, 0.3%, 0.4%, 0.5%, 0.55%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, etc.

[0087] In this embodiment, when the mass fraction W2 of the film-forming additive satisfies the range 0.01% ≤ W2 ≤ 1%, the mass fraction of the film-forming additive is within a reasonable range. On the one hand, the film-forming additive can preferentially form a film on the surface of the negative electrode plate 100 to protect the active material 111 whose structure has changed after powder pressing, thereby slowing down the side reaction between the active material 111 and the electrolyte 230, ensuring that the active material 111 can exhibit electrical performance, and enabling the battery 200 to have good cycle stability. On the other hand, it can avoid excessive film-forming additive from increasing the internal resistance of the battery 200, which is beneficial to improving the charge and discharge efficiency of the battery 200, thereby enabling the battery 200 to have better performance. When the mass fraction of the film-forming additive is too large, it may increase the internal resistance of the battery 200, thereby reducing the charge and discharge efficiency of the battery 200. When the mass fraction of the film-forming additive is too small, after the active material 111 is applied to the negative electrode plate 100 and compacted, even if the active material 111 has high compressive performance, part of the active material 111 is still structurally damaged during the compaction process. It is difficult for the film-forming additive to form a film on the surface of the negative electrode plate 100 and protect the negative electrode plate 100, and it is difficult for the film-forming additive to slow down the side reaction between the electrolyte 230 and the negative electrode plate 100, reducing the cycle performance of the battery 200.

[0088] The technical solution of the present application will be further introduced in multiple embodiments as follows:

[0089] Examples 1 to 6, Comparative Examples 1 to 3:

[0090] 1. Preparation of the negative electrode plate 100:

[0091] (1) Preparation of the active material 111:

[0092] Select petroleum coke with a sulfur content of 0.3% to 2.5%. After the shaping process, control the median particle size of the petroleum coke to be between 9 μm and 14 μm. The control parameters of the shaping process can mainly reflect the regularity of the material, reduce the stress concentration sites on the material surface, and thus improve the compressive characteristics of the material. After the graphitization process, an intermediate material is obtained, and the graphitization degree of the intermediate material is controlled between 93% and 96%. The graphitization degree of the intermediate material can reflect the surface defect degree and the orientation degree of the intermediate material. The higher the orientation degree, the better the compressive characteristics of the intermediate material, thereby improving the compressive characteristics of the intermediate material. Finally, through the finished product processing process, the active materials 111 of Examples 1 to 6 are obtained.

[0093] Among them, the sulfur content W3 value, the median particle size Dv50 value, and the graphitization degree G value of the active materials 111 of Examples 1 to 6 are shown in Table 1.

[0094] Among them, the detection methods for the first stability coefficient α1 and the second stability coefficient α2 of the active material 111 are as follows: Use a laser diffraction particle size distribution measuring instrument (Malvern Mastersizer 3000). According to the laser diffraction method for particle size distribution GB / T19077-2016, measure the particle size distribution of the active material 111 to obtain Dv50, Dv50’, Dn50, and Dn50’. Calculate the value of α1 through the formula α1 = Dv50 - Dv50’, and calculate the value of α2 through the formula α2 = Dn50 - Dn50’. The values of the first stability coefficient α1 and the second stability coefficient α2 of the active materials 111 of Examples 1 to 6 and Comparative Examples 1 to 3 are shown in Table 1.

[0095] (2) Preparation of the negative electrode plate 100:

[0096] Fully dissolve carboxymethyl cellulose with a mass content of 0.5% and a binder with a mass content of 1.7% in water, add carbon black conductive agent with a mass content of 0.8% and active material 111 with a mass content of 97% to make a uniformly dispersed slurry. Uniformly coat the slurry on the surface of the negative electrode current collector layer 120 (copper foil), and then transfer it to a vacuum drying oven for complete drying. The slurry forms the negative electrode material layer 110, thereby obtaining the negative electrode plates 100 of Examples 1 to 6 and Comparative Examples 1 to 3.

[0097] Among them, the active material 111 of Example 1 is applied to the negative electrode plate 100 of Example 1, the active material 111 of Example 2 is applied to the negative electrode plate 100 of Example 2, the active material 111 of Comparative Example 1 is applied to the negative electrode plate 100 of Comparative Example 1, and so on.

[0098] 2. Preparation of the positive electrode plate 220:

[0099] The lithium iron phosphate of the positive electrode active material 111, the conductive carbon black (SP) of the positive electrode conductive agent, and the polyvinylidene fluoride (PVDF) of the positive electrode binder are dispersed in the solvent N-methylpyrrolidone (NMP) according to a mass ratio of 97:0.5:2.5. The positive electrode slurry is coated on the positive electrode current collector layer (aluminum foil), and after drying, cold pressing, slitting, and cutting, the positive electrode material layer is obtained, and the positive electrode plate 220 is obtained.

[0100] 3. Preparation of the electrolyte 230:

[0101] In an argon atmosphere glove box with a water content ≤ 1 ppm, ethylene carbonate (EC), diethyl carbonate (DEC), and ethyl methyl carbonate (EMC) are mixed according to a mass ratio of 1:1:1. Then, the dry lithium salt lithium hexafluorophosphate is dissolved in the solvent, stirred until completely dissolved and uniform, and the film-forming additive (vinylene carbonate) is added and mixed evenly to obtain the electrolytes 230 of Examples 1 to 6 and Comparative Examples 1 to 3.

[0102] Among them, the values of the mass fraction W2 of the film-forming additive and the value of W2×α1×α2 in the electrolytes 230 of Examples 1 to 6 and Comparative Examples 1 to 3 are shown in Table 1.

[0103] 4. Preparation of the separator 210:

[0104] Use a 16-μm polyethylene film as the separator 210.

[0105] 5. Preparation of the battery 200:

[0106] The prepared positive electrode plate 220, separator 210, and negative electrode plate 100 are stacked in sequence, with the separator 210 in the middle of the positive electrode plate 220 and the negative electrode plate 100. After winding, the bare battery core is obtained. After welding the electrode tabs, the bare battery core is assembled into the outer package, and the prepared electrolyte 230 is injected. Then, the battery core is encapsulated, left standing, formed, shaped, capacity tested, etc., and finally, the implementation batteries 1 to 6 and the comparative batteries 1 to 3 are prepared.

[0107] Among them, the electrolyte 230 of Example 1 is applied to the implementation battery 1, the electrolyte 230 of Example 2 is applied to the implementation battery 2, the electrolyte 230 of Comparative Example 1 is applied to the comparative battery 1, and so on.

[0108] The following Table 1 shows the performance parameters of the active material 111 and the performance parameters of the electrolyte 230 of Examples 1 to 6 and Comparative Examples 1 to 3.

[0109] Table 1: Performance parameters of the active material 111 and the performance parameters of the electrolyte 230 of Examples 1 to 6 and Comparative Examples 1 to 3.

[0110]

[0111] In addition, after the active material 111 undergoes a graphitization process, the active material 111 is obtained, and the value of the mass fraction W1 of the primary particles, the value of the difference γ between the specific surface area of the primary particles and the specific surface area of the secondary particles, and the value of the difference β between the first Coulomb efficiency of the primary particles and the first Coulomb efficiency of the secondary particles in the active material 111 can be measured. Among them, the values of other parameters of the active material 111 in Examples 1 to 6 and Comparative Examples 1 to 3 are shown in Table 2.

[0112] Table 2: Other parameters of the active material 111 in Examples 1 to 6 and Comparative Examples 1 to 3.

[0113]

[0114] Battery 200 performance test:

[0115] Performance tests of Implementation Batteries 1 to 6 and Comparative Batteries 1 to 3:

[0116] At 25°C, Implementation Batteries 1 to 6 and Comparative Batteries 1 to 3 are subjected to a constant-power charge-discharge cycle test on a charge-discharge instrument. The charge-discharge rate is 0.5C, the charge-discharge voltage window is 2.5V to 3.65V, and the battery 200 is cycled until the capacity is less than 80% of the initial capacity, and the number of cycles is recorded.

[0117] Calculate the capacity retention rate after 500 cycles. The calculation formula is: Capacity retention rate after the Nth cycle = (Discharge capacity after the Nth cycle / Discharge capacity of the first cycle) × 100%.

[0118] Among them, usually, one complete charge-discharge is called one charge-discharge cycle, and cycling N times means repeating the above process N times.

[0119] Among them, the values of the capacity retention rates of Implementation Batteries 1 to 6 and Comparative Batteries 1 to 3 after cycling 500 times at 25°C are shown in Table 3.

[0120] Table 3: Performance parameters of Implementation Batteries 1 to 6 and Comparative Batteries 1 to 3

[0121]

[0122] Please refer to Tables 1 to 3. The capacity retention rates of Implementation Batteries 1 to 6 after 500 cycles at 25°C are all higher than those of Comparative Batteries 1 to 3 after 500 cycles at 25°C. This is because: in Examples 1 to 6, the sulfur content W3 of the active material 111 satisfies the range 0.3% ≤ W3 ≤ 2.5%, the Dv50 of the active material 111 satisfies the range 10 μm ≤ Dv50 ≤ 15 μm, the graphitization degree G of the active material 111 satisfies the range 93% ≤ G ≤ 96%, and the mass fraction W2 of the film-forming additive in the electrolyte 230 satisfies the range 0.01% ≤ W2 ≤ 1%, so that the active material 111 has better compressive strength. The first stability coefficient α1 of the active material 111 satisfies the range 0 ≤ α1 ≤ 1 μm, and the second stability coefficient satisfies the range 0 ≤ α2 ≤ 0.04 μm. In addition, the battery 200 also satisfies the relational expression 0 ≤ W2 × α1 × α2 ≤ 4 × 10 -5 μm 2Among the implementation cells 1 to 6, the active material 111 has good compressive properties. When the active material 111 is applied to the negative electrode tab 100 and assembled into the battery 200, the active material 111 can still maintain a relatively complete structure after powder compaction, avoiding changes in the structure due to the rupture of the active material 111, so as to avoid exposing more active reaction sites, thereby reducing the side reaction between the electrolyte 230 in the battery 200 and the active material 111, which is beneficial to slowing down the attenuation of the battery 200, thereby improving the cycling performance of the battery 200 and extending the service life of the battery 200. In Comparative Example 1, the value of Dv50 of the active material 111 is too large, and the power transmission amount during the graphitization process of the active material 111 is too small, resulting in too low a degree of graphitization of the active material 111 and too large a value of the first stability coefficient α1 of the active material 111. In other words, the structural stability of the active material 111 becomes poor. The structure of the active material 111 is damaged after compaction and too many sites are exposed. In addition, the electrolyte 230 in Comparative Example 1 does not include the cyclic carbonate additive, making it difficult to protect the active material 111 with a damaged structure, thereby exacerbating the side reaction between the electrolyte 230 and the negative electrode tab 100, resulting in a low cycling capacity retention rate of Comparative Battery 1. In Comparative Example 2, the power transmission time during the graphitization process of the active material 111 is too short, resulting in too low a degree of graphitization of the active material 111. Correspondingly, the degree of orientation of the active material 111 is too low, resulting in too large a second stability coefficient α2 of the active material 111, so that the structural stability and compressive properties of the active material 111 are poor. The structure of the active material 111 is damaged after compaction and too many sites are exposed. In addition, the electrolyte 230 in Comparative Example 2 does not include the cyclic carbonate additive, making it difficult to protect the active material 111 with a damaged structure, thereby exacerbating the side reaction between the electrolyte 230 and the negative electrode tab 100, resulting in a low cycling capacity retention rate of Comparative Battery 2. By comprehensively comparing the data of Comparative Battery 1 and Comparative Battery 2, it can be seen that the active material 111 and the film-forming additive have a synergistic effect, which can effectively improve the cycling stability of the corresponding battery 200.In Comparative Example 3, the amount of electricity transmitted during the graphitization process of the active material 111 was too small, and the power transmission time was too short, resulting in the first stability coefficient, the second stability coefficient of the active material 111, and the mass fraction of the film-forming additive being too large, resulting in an excessive value of W2×α1×α2, and thus the cycle stability of the comparative battery 3 was significantly lower than that of other batteries 200. This is because: since the first stability coefficient and the second stability coefficient of the active material 111 are both large, too many active sites are exposed after the active material 111 is compacted, exacerbating the side reaction between the negative electrode sheet 100 and the electrolyte 230. In addition, although the film-forming additive can damage the active material 111 with a damaged structure, the excessive amount of the film-forming additive increases the internal resistance of the comparative battery 3, resulting in poor cycle performance of the comparative battery 3. Furthermore, the granulation effect of the active material 111 in Comparative Example 3 is poor. The granulation effect refers to the fact that after the secondary granulation process, the particle structure, particle size distribution, morphology, and performance of the active material 111 do not reach the ideal state or design requirements. In other words, the active material 111 does not achieve the expected optimization goal during the secondary granulation process, resulting in poor structural stability of the active material 111.

[0123] Furthermore, it can be seen from the data of Examples 1 to 6 and Comparative Examples 1 to 3 that as the value of the amount of electricity transmitted during the graphitization process, the power transmission time, and the packing depth increase, the graphitization degree of the active material 111 gradually increases.

[0124] Still further, please refer to Table 1 and Table 2. In the active material 111 of Examples 1 to 6, the mass fraction W1 of the primary particles satisfies the range of 40% ≤ W1 ≤ 95%, and the difference γ between the specific surface area of the primary particles and the specific surface area of the secondary particles ranges from: 0.3m 2 / g ≤ γ ≤ 0.6m 2 / g. The difference β between the first Coulomb efficiency of the primary particles and the first Coulomb efficiency of the secondary particles satisfies the range of 0 ≤ β ≤ 0.6%. The primary particles and the secondary particles cooperate with each other to enable the active material 111 to have good compressive performance and also enable the active material 111 to have good electrical performance. It can be understood that the mass fraction W1 of the primary particles, the difference γ between the specific surface area of the primary particles and the specific surface area of the secondary particles, and the difference β between the first Coulomb efficiency of the primary particles and the first Coulomb efficiency of the secondary particles are these parameters that can only be obtained after the graphite sintering undergoes the graphitization process. Therefore, it is impossible to design control variables for such parameters during the preparation process. The data in Table 2 only characterize the parameters of the active material 111 to show that the active material 111 has both good compressive performance and electrical performance, which also helps to improve the cycle stability of its corresponding battery 200.

[0125] Further, please refer to Figure 3 , Figure 3 which is a comparison chart of the cycling effects of the implementation battery 1 and the comparative battery 1. As can be seen from Figure 3 , as the number of cycles increases, the cycling capacity retention rates of the implementation battery 1 and the comparative battery 1 gradually decrease. Correspondingly, however, the cycling capacity retention rate of the implementation battery 1 is always higher than that of the comparative battery 1, indicating that the implementation battery 1 has better cycling stability than the comparative battery 1.

[0126] Please refer to Figure 4 and Figure 5 . The present application provides an electrical device 300, which includes: a device body 310 and the battery 200 provided by the present application, and the battery 200 supplies power to the device body 310.

[0127] It can be understood that the battery 200 is electrically connected to the device body 310.

[0128] In this embodiment, the battery 200 includes the active material 111 and the electrolyte 230 provided by this embodiment. The active material 111 has a relatively low first stability coefficient and second stability coefficient, and the electrolyte 230 includes a cyclic carbonate additive. The active material 111 and the electrolyte 230 have a good synergistic effect, which can greatly slow down the side reaction between the active material 111 and the electrolyte 230, so that the battery 200 has good cycling stability and a long service life. Further, the battery 200 can provide stable electrical energy for the device body 310, which is beneficial to improving the user experience.

[0129] Optionally, the electrical device 300 in the embodiments of the present application may be, but is not limited to, portable electronic devices such as mobile phones, tablet computers, laptop computers, desktop computers, smart bracelets, smart watches, e-readers, game consoles, etc. It may also be transportation means such as cars, trucks, sedans, freight trucks, bullet trains, high-speed rails, and electric scooters. In addition, it may also be various household appliances, etc. The electrical device 300 in the embodiments of the present application Figure 4 is an energy storage battery cabinet.

[0130] It can be understood that the electrical device 300 described in this embodiment is only one form of the electrical device 300 to which the battery 200 is applied, and should not be construed as a limitation on the electrical device 300 provided by the present application, nor should it be construed as a limitation on the electrical device 300 provided by each embodiment of the present application.

[0131] References to "embodiments" or "implementation manners" in this application mean that specific features, structures, or characteristics described in connection with the embodiments may be included in at least one embodiment of this application. The phrase appearing at various positions in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment mutually exclusive with other embodiments. Those skilled in the art explicitly and implicitly understand that the embodiments described in this application may be combined with other embodiments. In addition, it should also be understood that the features, structures, or characteristics described in each embodiment of this application can be arbitrarily combined with each other without contradiction to form another embodiment that does not depart from the spirit and scope of the technical solution of this application.

[0132] Finally, it should be noted that the above implementation manners are only used to illustrate the technical solutions of this application and not to limit them. Although the technical solutions of this application have been described in detail with reference to the above preferred implementation manners, those of ordinary skill in the art should understand that modifications or equivalent replacements can be made to the technical solutions of this application without departing from the spirit and scope of the technical solutions of this application.

Claims

1. An active material, characterized in that The active material has a first stability coefficient α1 and a second stability coefficient α2, and the active material satisfies the relationship: α1=Dv50-Dv50', 0≤α1≤1μm; and satisfies the relationship α2=Dn50-Dn50', 0≤α2≤0.04μm; Wherein, Dv50 is the particle size of the active material measured when the cumulative volume fraction in the volume-based distribution reaches 50%, and Dv50' is the particle size of the active material measured when the cumulative volume fraction in the volume-based distribution reaches 50% after a 5-ton powder compaction test; Dn50 is the particle size of the active material measured when the cumulative number fraction in the number-based distribution reaches 50%, and Dn50' is the particle size of the active material measured when the cumulative number fraction in the number-based distribution reaches 50% after a 5-ton powder compaction test.

2. The active material according to claim 1, characterized in that The active material is selected from at least one of artificial graphite and natural graphite, and the graphitization degree G of the active material is in the range of 93%≤G≤96%.

3. The active material according to claim 1, characterized in that The active material includes primary particles and secondary particles. The secondary particles are agglomerates of the primary particles. The particle size of the primary particles is smaller than that of the secondary particles. In the active material, the mass fraction W1 of the primary particles is in the range of 40%≤W1≤95%.

4. The active material according to claim 3, characterized in that The difference γ between the specific surface area of ​​the primary particles and the specific surface area of ​​the secondary particles is in the range of: 0.3 m 2 / g≤γ≤0.6m 2 / g.

5. The active material according to claim 3, characterized in that The range of the difference β between the first coulomb efficiency of the primary particles and the first coulomb efficiency of the secondary particles is: 0≤β≤0.6%.

6. The active material according to any one of claims 1 to 5, characterized in that The active material meets the range: 10 μm≤Dv50≤15 μm.

7. The active material according to any one of claims 1 to 5, characterized in that The specific surface area S of the active material is in the range of: 1.0 m 2 / g≤S≤2.0m 2 / g.

8. The active material according to any one of claims 1 to 5, characterized in that The range of the gram capacity C of the active material is: 340 mAh / g≤C≤360 mAh / g.

9. A negative electrode plate, characterized in that: The negative electrode sheet comprises: a negative electrode material layer and a negative electrode current collector layer, wherein the negative electrode material layer is disposed on at least one surface of the negative electrode current collector layer, and the negative electrode material layer comprises the active material according to any one of claims 1 to 8.

10. A battery, characterized in that: The battery comprises: The negative electrode sheet according to claim 9; A diaphragm, the diaphragm being arranged on one side of the negative electrode plate; A positive electrode sheet, the positive electrode sheet being disposed on a side of the diaphragm away from the negative electrode sheet; and The electrolyte comprises a film-forming additive, wherein the film-forming additive comprises a cyclic carbonate additive.

11. The battery according to claim 10, characterized in that In the electrolyte, the mass fraction of the film-forming additive is W2, and the battery satisfies the relationship: 0≤W2×α1×α2≤4×10 -5 μm 2 .

12. The battery according to claim 11, characterized in that In the electrolyte, the mass fraction W2 of the film-forming additive is in the range of 0.01%≤W2≤1%.

13. An electrical equipment, characterized in that: The electrical equipment includes: The device itself; and The battery according to any one of claims 10 to 12, wherein the battery is used to power the device body.

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