Formation method of battery

Abstract

The invention discloses a battery formation method. The method comprises the following steps: carrying out first-stage formation treatment and second-stage formation treatment on a battery to be formed; the temperature of the first-stage formation treatment is higher than that of the second-stage formation treatment; the first-stage formation treatment comprises the steps of performing first-step charging treatment, second-step charging treatment and third-step charging treatment in sequence; the charging multiplying power of the first-step charging treatment, the charging multiplying power of the second-step charging treatment and the charging multiplying power of the third-step charging treatment are sequentially increased, and the charging multiplying power of the first-step charging treatment ranges from 0.02 C to 0.1 C. According to the formation method of the battery, the SEI film component and structure optimization can be realized, so that the side reaction at the positive and negative electrode / electrolyte interface is reduced, the thermal shock performance and the stability of the battery are improved, and the overall performance is excellent.

Description

Technical Field

[0001] The present application relates to the field of battery technology, and in particular to a battery formation method. Background Art

[0002] With the development of science and technology, batteries play an increasingly important role in people's lives and work, and their safety has also been widely concerned. When batteries encounter thermal shock, they are very likely to cause combustion or even explosion due to internal short circuits and rapid rise in internal temperature. Therefore, how to improve the thermal shock performance of batteries needs to be studied. Summary of the invention

[0003] The present application aims to solve at least one of the technical problems in the related art to a certain extent. To this end, one purpose of the present application is to propose a battery formation method, a battery and an electrical device, and the battery formation method of the present application can optimize the SEI film components and structure, so as to reduce the side reactions at the positive and negative electrode / electrolyte interfaces, improve the thermal shock performance and stability of the battery, and achieve excellent overall performance.

[0004] The first aspect of the present application provides a battery formation method. According to an embodiment of the present application, the method comprises: subjecting a battery to be formed to a first stage formation treatment and a second stage formation treatment;

[0005] The temperature of the first stage chemical formation treatment is greater than the temperature of the second stage chemical formation treatment;

[0006] The first stage formation treatment includes: performing a first step of charging, a second step of charging and a third step of charging in sequence; the charging rates of the first step of charging, the second step of charging and the third step of charging treatment are increased in sequence, and the charging rate of the first step of charging treatment is 0.02C to 0.1C.

[0007] According to the embodiments of the present application, the battery to be formed is first subjected to a formation treatment method of high temperature (first) and then low temperature (second), and a three-step charging method is adopted in the high temperature stage, and the charging current is increased sequentially, and the first step charging current meets the above conditions, which is helpful to form a relatively dense SEI film inner layer and a loose SEI film outer layer structure, and realize the further optimization of the SEI film components and structure, thereby reducing the side reactions at the positive and negative electrode / electrolyte interfaces, and ultimately improving the thermal shock performance of the battery.

[0008] According to an embodiment of the present application, the battery formation method may also have the following additional technical features:

[0009] According to an embodiment of the present application, the temperature of the first stage chemical formation treatment is 75° C. to 85° C.;

[0010] And / or, the temperature of the second stage chemical conversion treatment is 30°C to 45°C.

[0011] According to an embodiment of the present application, the pressure of the first stage chemical formation treatment is greater than the pressure of the second stage chemical formation treatment.

[0012] According to an embodiment of the present application, the pressure of the first stage chemical formation treatment is 10kgf / 2pcs to 15kgf / 2pcs;

[0013] And / or, the pressure of the second stage chemical formation treatment is 5kgf / 2pcs to 7kgf / 2pcs.

[0014] According to an embodiment of the present application, the first step of charging treatment takes 20 minutes to 100 minutes;

[0015] The cut-off voltage of the first step charging process is no more than 3.5V.

[0016] According to an embodiment of the present application, the charging rate of the second step of charging treatment is 0.1C to 0.2C;

[0017] And / or, the second step of charging treatment lasts for 20 minutes to 40 minutes;

[0018] And / or, the cut-off voltage of the second step charging process is no more than 3.8V.

[0019] According to an embodiment of the present application, the charging rate of the third step of charging treatment is 0.5C to 1.2C;

[0020] And / or, the duration of the third step of charging treatment is 25 min to 60 min;

[0021] And / or, the cut-off voltage of the third step charging process is no more than 4.2V.

[0022] According to an embodiment of the present application, the second stage formation treatment includes: sequentially performing a fourth step charging treatment and a fifth step circulation.

[0023] According to an embodiment of the present application, the charging rate of the fourth step of charging treatment is 0.5C to 0.7C, constant current and constant voltage;

[0024] And / or, the cut-off voltage of the fourth step charging process is 4.48V to 4.56V, and the cut-off current is 0.02C to 0.03C.

[0025] According to an embodiment of the present application, the fifth cycle treatment includes cyclically performing a fifth discharge treatment and a fifth charge treatment, and the cycle rate is 0.5C to 0.7C;

[0026] The fifth discharge process discharges at a constant current to 2.75V to 3.4V;

[0027] The fifth charging process is performed with constant current charging for 52 min to 72 min.

[0028] According to an embodiment of the present application, the battery to be formed is pre-aged at a temperature of 30° C. to 45° C. for a time of 24 h to 72 h.

[0029] According to an embodiment of the present application, the battery includes a lithium-ion battery.

[0030] According to an embodiment of the present application, the battery includes a negative electrode plate, and the negative electrode active material of the negative electrode plate includes a silicon-containing substance.

[0031] The second aspect of the present application provides a battery. According to an embodiment of the present application, the battery is obtained by forming a battery to be formed using the battery formation method described in the first aspect of the present application.

[0032] The third aspect of the present application provides an electric device. According to an embodiment of the present application, the electric device includes the battery described in the second aspect of the present application.

[0033] Additional aspects and advantages of the present application will be given in part in the description below, and in part will become apparent from the description below, or will be learned through the practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] The above and / or additional aspects and advantages of the present application will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0035] Figure 1 and Figure 2 The flowcharts of the battery formation method according to one embodiment of the present application are shown respectively. DETAILED DESCRIPTION

[0036] The embodiments of the present application are described in detail below. The embodiments described below are exemplary and are only used to explain the present application, and cannot be understood as limiting the present application.

[0037] It should be noted that the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. Further, in the description of this application, unless otherwise specified, the meaning of "plurality" is two or more.

[0038] The endpoints and any values ​​of the ranges disclosed in this application are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be regarded as specifically disclosed in this application.

[0039] In the present application, the terms "comprise" or "include" are open expressions, that is, including the contents specified in the present application but not excluding other contents.

[0040] "Thermal shock" refers to an object experiencing extreme temperature changes in a short period of time. This rapid temperature change can cause thermal stress inside the object, which may cause the material to rupture, deform or other damage. In the field of battery technology, the impact of thermal shock on batteries is particularly significant, as shown below: internal short circuit, thermal runaway, electrolyte decomposition, electrode material degradation and diaphragm damage. Thermal shock significantly affects the performance and safety of the battery. "Thermal shock performance of a battery" refers to the ability of a battery to maintain its performance and structural integrity and avoid thermal runaway or damage when encountering sudden temperature changes or high temperature environments.

[0041] In view of this, the study found that the solid electrolyte interface (SEI) film structure of the battery has a significant impact on the thermal shock performance, among which the SEI film structure with a dense inner layer and a loose outer layer can effectively improve the thermal shock performance of the battery. Based on this, in the battery formation process, a high temperature followed by a low temperature formation method is adopted. In the high temperature formation stage, different charging rates are used, and a lower charging rate is used in the initial stage, thereby promoting the formation of a SEI film with a dense inner layer and a loose outer layer. This structure not only reduces the side reactions between the positive and negative electrodes and the electrolyte, but also effectively improves the thermal shock performance of high-capacity silicon negative electrode batteries.

[0042] In the first aspect of the present application, a battery formation method is proposed. According to the embodiments of the present application, see Figure 1 The method includes: S100 first stage formation treatment and S200 second stage formation treatment. Specifically, the battery to be formed is subjected to S100 first stage formation treatment and S200 second stage formation treatment, wherein the temperature of S100 first stage formation treatment is greater than the temperature of S200 second stage formation treatment.

[0043] The solid electrolyte interface (SEI) film structure has a significant impact on the thermal shock performance of the battery. By deeply analyzing the formation mechanism of the SEI film, especially the relationship between voltage and product growth, an SEI film structure with improved thermal shock performance of the battery was determined, that is, a SEI film with a dense inner layer and a loose outer layer. This structure not only optimizes the electrochemical performance of the battery, but also significantly improves its stability and safety under extreme temperature conditions, and improves the thermal shock performance of the battery.

[0044] In the initial stage of SEI film formation (one-step charging stage), under high temperature and high pressure conditions, a large number of electrons gather on the surface of the negative electrode material, which is more likely to react with the film-forming additive / lithium ions by two electrons. The inner layer of the generated solid electrolyte interface (SEI) film is mainly composed of inorganic lithium salts, such as LiF, Li2CO3, Li2O, etc. The inner layer of the SEI film formed by these inorganic lithium salts is relatively dense, which can effectively isolate the direct contact between the electrode material and the electrolyte, thereby reducing the side reactions at the electrode material / electrolyte interface, obtaining a stable inner layer structure of the SEI film and reducing the consumption of lithium ions. After the inner layer of the SEI film is formed (two-step / three-step charging stage), electrons need to pass through the inner layer of the SEI film to react with the film-forming additive / lithium ions. Therefore, single electron reactions are more likely to occur at this time, and the outer layer of the SEI film generated is mainly composed of organic lithium salts, such as LEDC / LMC / LEC, etc. This loose and porous outer layer is conducive to the transmission of lithium ions, ensuring that the battery has high conductivity and charge and discharge efficiency during the charge and discharge process. Under low temperature and low pressure conditions, the intermediate product obtained from the first stage formation treatment is further subjected to a second charging treatment. The unstable organic lithium salts in the battery SEI film are further decomposed during the charging process to form more stable components, thereby obtaining a more stable SEI film, further improving the stability of the battery and ultimately obtaining better thermal shock performance.

[0045] Furthermore, the first stage formation treatment S100 includes a first step of charging S110, a second step of charging S120 and a third step of charging S130, and the charging rates of the first step of charging S110, the second step of charging S120 and the third step of charging S130 are increased successively to improve production efficiency and meet actual production capacity requirements; the charging rate of the first step of charging treatment is 0.02C to 0.1C.

[0046] In the first stage of high-temperature formation, the above-mentioned low-rate charging method is first used. Low-rate charging helps electrons react with film-forming additives / lithium ions at the electrode material / electrolyte interface to generate inorganic lithium salts, and deposits more evenly on the surface of the electrode material, thereby promoting the formation of a more uniform and dense SEI film inner layer. This film can effectively prevent excessive consumption of lithium ions and build a stable SEI film inner layer structure. At the same time, in the early stage of formation, the reaction at the electrode material / electrolyte interface is more active, and low-rate charging can slow down the reaction rate, thereby reducing the generation of gas and the consumption of active substances in certain side reactions. Furthermore, low-rate charging helps control the battery temperature and avoid overheating. With the stable formation of the SEI film, increasing the charging rate can shorten the formation time to meet the actual needs of industrial generation.

[0047] In the present application, the term "battery to be formed" refers to a battery that has been assembled, electrolyte infiltrated, sealed and aged and is ready for formation. In some embodiments, the battery to be formed has been aged in advance, and the temperature of the aging treatment is 30°C to 45°C, including but not limited to: 30°C, 32°C, 35°C, 37°C, 40°C, 42°C, 45°C, and the time is 24h to 72h, including but not limited to: 24h, 30h, 36h, 42h, 48h, 54h, 60h, 66h, 72h. This helps the electrolyte to fully infiltrate the electrode material, form a stable and uniform SEI film, and improve the thermal shock performance of the battery.

[0048] According to an embodiment of the present application, the temperature of the first stage formation treatment S100 is 75°C to 85°C, including but not limited to: 75°C, 78°C, 79°C, 80°C, 81°C, 82°C, 83°C, 84°C, 85°C, etc. As a result, under the above-mentioned high temperature and high pressure conditions, a large number of electrons gather on the surface of the negative electrode material, which is more conducive to the formation of a dense SEI film inner layer and a loose and porous SEI film outer layer. The overall SEI film structure is stable, the consumption of lithium ions is reduced, the transmission of lithium ions is promoted, and the thermal shock performance is improved. In addition, the SEI film has good film formation uniformity, less consumption during the film formation process, and high battery capacity. When the formation temperature in the first stage is too high, the decomposition of the SEI film is aggravated, the consumption during the film formation process increases, and the battery capacity decreases.

[0049] According to an embodiment of the present application, the pressure of the first stage formation treatment S100 is 10kgf / 2pcs to 15kgf / 2pcs, including but not limited to: 10kgf / 2pcs, 11kgf / 2pcs, 12kgf / 2pcs, 13kgf / 2pcs, 14kgf / 2pcs, 15kgf / 2pcs, etc. Therefore, under the above-mentioned high temperature and high pressure conditions, a large number of electrons gather on the surface of the negative electrode material, which is more conducive to the formation of a dense SEI film inner layer and a loose and porous SEI film outer layer. The overall SEI film structure is stable, the consumption of lithium ions is reduced, the transmission of lithium ions is promoted, and the thermal shock performance is improved. In addition, the SEI film has good film formation uniformity, less consumption during the film formation process, high cell flatness, and high battery capacity.

[0050] According to the embodiment of the present application, the charging rate of the first step of charging treatment is 0.02C to 0.1C, including but not limited to: 0.02C, 0.03C, 0.04C, 0.05C, 0.06C, 0.07C, 0.08C, 0.09C, 0.1C, etc. As a result, a large number of electrons are gathered on the surface of the negative electrode material, which is more conducive to the formation of a dense SEI film inner layer and a loose and porous SEI film outer layer. The overall SEI film structure is stable, the consumption of lithium ions is reduced, the transmission of lithium ions is promoted, and the thermal shock performance is improved. In addition, the SEI film has good film uniformity, less consumption during the film formation process, and high battery capacity.

[0051] According to the embodiment of the present application, the charging rate of the second step charging treatment is 0.1C to 0.2C, including but not limited to: 0.1C, 0.12C, 0.15C, 0.18C, 0.2C, etc. As a result, it is helpful for a large number of electrons to gather on the surface of the negative electrode material, which is more conducive to the formation of a dense SEI film inner layer and a loose and porous SEI film outer layer. The overall SEI film structure is stable, the consumption of lithium ions is reduced, the transmission of lithium ions is promoted, and the thermal shock performance is improved. In addition, the SEI film has good film formation uniformity, less consumption during the film formation process, and high battery capacity.

[0052] According to the embodiments of the present application, the charging rate of the third step charging treatment is 0.5C to 1.2C, including but not limited to: 0.5C, 0.6C, 0.7C, 0.8C, according to the embodiments of the present application, 0.9C, 1.0C, 1.1C, 1.2C, etc. As a result, it is helpful for a large number of electrons to gather on the surface of the negative electrode material, which is more conducive to the formation of a dense inner layer of the SEI film and a loose and porous outer layer of the SEI film. The overall SEI film structure is stable, the consumption of lithium ions is reduced, the transmission of lithium ions is promoted, and the thermal shock performance is improved. In addition, the SEI film has good film formation uniformity, less consumption during the film formation process, and high battery capacity. When the three-step charging rate is too low, although the film formation uniformity is improved and the thermal shock performance is slightly increased, the formation time in the high temperature section is increased, the decomposition of the SEI film is aggravated, the consumption during the film formation process is increased, and the battery capacity decreases.

[0053] According to an embodiment of the present application, the first charging process S110, the second charging process S120 and the third charging process S130 all adopt a constant current charging mode.

[0054] According to an embodiment of the present application, the first step of charging process S110 lasts for 20 to 100 minutes, for example, 20 minutes, 30 minutes, 40 minutes, 50 minutes, 60 minutes, 70 minutes, 80 minutes, 90 minutes, and 100 minutes, and the cut-off voltage does not exceed 3.5 V. Thus, the stability of the SEI film structure is further improved, the consumption of lithium ions is reduced, the transmission of lithium ions is promoted, and the thermal shock performance is improved.

[0055] According to an embodiment of the present application, the second step of charging treatment S120 lasts for 20 to 40 minutes, for example, 20 minutes, 25 minutes, 30 minutes, 35 minutes, or 40 minutes, and the cut-off voltage does not exceed 3.8 V. Thus, the stability of the SEI film structure is further improved, the consumption of lithium ions is reduced, the transmission of lithium ions is promoted, and the thermal shock performance is improved.

[0056] According to an embodiment of the present application, the time of the third step charging process S130 is 25 min to 60 min, for example, 25 min, 30 min, 40 min, 50 min, 60 min, and the cut-off voltage does not exceed 4.2 V, for example, 4.2 V, 4.1 V, 4.0 V, 3.9 V, 3.8 V, 3.7 V, 3.6 V, 3.5 V. Thus, the stability of the SEI film structure is further improved, the consumption of lithium ions is reduced, the transmission of lithium ions is promoted, and the thermal shock performance is improved.

[0057] According to an embodiment of the present application, the second stage formation process S200 includes: sequentially performing a fourth step charging process S210 and a fifth step circulation process S220.

[0058] According to an embodiment of the present application, the temperature of the second stage formation treatment S200 is 30°C to 45°C, including but not limited to: 30°C, 35°C, 40°C, 45°C, etc. The second stage formation treatment adopts the above-mentioned low-temperature charge and discharge treatment to promote the further reaction and reconstruction of some unstable organic lithium salt components in the outer layer of the SEI film, generate more stable lithium salt components, and construct a more stable SEI film, thereby further improving the thermal shock performance of the battery; at the same time, effectively reduce the impedance of the battery and obtain better electrochemical performance. In addition, the SEI film has good film formation uniformity, less consumption during the film formation process, and high battery capacity. When the second stage formation temperature is too high, the consumption during the film formation process increases, the battery capacity decreases, and the thermal shock performance does not change significantly.

[0059] According to an embodiment of the present application, the pressure of the second stage formation treatment S200 is 5 to 7kgf / 2pcs, including but not limited to: 5kgf / 2pcs, 6kgf / 2pcs, 7kgf / 2pcs, etc. The second stage formation treatment adopts the above-mentioned low temperature and low pressure charge and discharge treatment to promote the further reaction and reconstruction of some unstable organic lithium salt components in the outer layer of the SEI film, generate more stable lithium salt components, and construct a more stable SEI film, thereby further improving the thermal shock performance of the battery; at the same time, effectively reduce the impedance of the battery and obtain better electrochemical performance. In addition, the SEI film has good film formation uniformity, less consumption during the film formation process, high battery capacity, and high cycle performance. When the second stage formation pressure is too low, the thickness of the battery cell is prone to be too thick; when the second stage formation pressure is too high, the residual amount of the battery cell is low, resulting in poor long cycle performance.

[0060] According to an embodiment of the present application, the second stage formation treatment S200 includes: sequentially performing the fourth step of charging S210, the first step of discharging 220 and the fifth step of charging 230. The intermediate product after the first stage formation treatment is first charged and discharged and charged in a cycle, further promoting the further reaction and reconstruction of some unstable organic lithium salt components in the outer layer of the SEI film, generating more stable lithium salt components, and constructing a more stable SEI film, thereby further improving the thermal shock performance of the battery; at the same time, effectively reducing the impedance of the battery and obtaining better electrochemical performance.

[0061] According to an embodiment of the present application, the charging rate of the fourth step charging process is 0.5C~0.7C, including but not limited to: 0.5C, 0.55C, 0.6C, 0.65C, 0.7C, etc., constant current and constant voltage; the cut-off voltage of the fourth step charging process is 4.48V~4.56V, including but not limited to: 4.48V, 4.49V, 4.50V, 4.51V, 4.52V, 4.53V, 4.54V, 4.55V, 4.56V, and the cut-off current is 0.02C~0.03C, including but not limited to: 0.02C, 0.022C, 0.024C, 0.025C, 0.026C, 0.028C, 0.03C, etc. As a result, some unstable organic lithium salt components are further promoted to react and reconstruct in the outer layer of the SEI film, generating more stable lithium salt components and building a more stable SEI film, thereby further improving the thermal shock performance of the battery. In addition, the SEI film has good film formation uniformity, less consumption during the film formation process, high battery capacity, effectively reducing the impedance of the battery, and obtaining better electrochemical performance.

[0062] According to the embodiment of the present application, the fifth step of the cycle treatment includes cyclically performing the fifth discharge treatment and the fifth charge treatment, and the cycle ratio is 0.5C to 0.7C, including but not limited to: 0.5C, 0.52C, 0.55C, 0.57C, 0.6C, 0.62C, 0.65C, 0.67C, 0.7C, etc. Thus, some unstable organic lithium salt components are further promoted to further react and reconstruct in the outer layer of the SEI film, generating more stable lithium salt components and constructing a more stable SEI film, thereby further improving the thermal shock performance of the battery; at the same time, the impedance of the battery is effectively reduced to obtain better electrochemical performance.

[0063] According to an embodiment of the present application, the fifth discharge treatment is performed at a constant current to discharge to 2.75V to 3.4V, including but not limited to: 2.75V, 2.8V, 3.0V, 3.2V, 3.4V. Thus, part of the unstable organic lithium salt components are further promoted to further react and reconstruct in the outer layer of the SEI film, generate more stable lithium salt components, and construct a more stable SEI film, thereby further improving the thermal shock performance of the battery; at the same time, the impedance of the battery is effectively reduced to obtain better electrochemical performance.

[0064] According to an embodiment of the present application, the fifth charging process is a constant current charging for 52min to 72min, including but not limited to: 52min, 55min, 60min, 65min, 70min, 72min, etc. Thus, some unstable organic lithium salt components are further promoted to further react and reconstruct in the outer layer of the SEI film, generating more stable lithium salt components and constructing a more stable SEI film, thereby further improving the thermal shock performance of the battery; at the same time, the impedance of the battery is effectively reduced to obtain better electrochemical performance.

[0065] According to an embodiment of the present application, Figure 2 The specific steps of a battery formation method are shown.

[0066] According to an embodiment of the present application, the battery includes a lithium-ion battery.

[0067] According to an embodiment of the present application, the battery includes a positive electrode sheet, and the positive electrode sheet includes a positive electrode active material.

[0068] When the battery is a lithium-ion battery, the positive electrode active material includes lithium iron phosphate, nickel-cobalt-manganese ternary, lithium cobalt oxide or lithium manganese oxide.

[0069] The positive electrode active material includes LiCoO2, LiMn2O4, LiMnO2, Li2MnO4, LiFePO4, LiNi x Co y Mn z M 1-x-y-z O2、Li 1+a Mn 1-x M x O2、LiCo 1-x M x O2、LiFe 1-x M x PO4 and Li2Mn 1-x At least one of O4, M is selected from at least one of Ni, Co, Mn, Al, Cr, Mg, Zr, Mo, V, Ti, B and F, 0≤a<0.2, 0≤x<1.

[0070] For example, 0≤a≤0.19, 0.05≤a≤0.15, 0.08≤a≤0.13, 0.1≤a≤0.12; 0≤x≤0.9, 0.1≤x≤0.8, 0.2≤x≤0.7, 0.3≤x≤0.6, 0.4≤x≤0.5, etc.

[0071] Understandable, Li 1+a Mn 1-x M x O2、LiCo 1-x M x O2 and LiFe 1-x M x In PO4, the selection of M in each chemical formula is independent of each other and does not affect each other. They can be the same or different. Similarly, in the above-mentioned list of positive electrode active materials, the selection of a and x is also opposite to each other and does not affect each other. They can be the same or different.

[0072] The positive electrode current collector may include a metal foil or a composite positive electrode current collector. For example, the metal foil may be aluminum foil. The composite positive electrode current collector may include a polymer material base and a metal layer formed on at least one side of the polymer material base. For example, the composite negative electrode current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, etc.) on a polymer material substrate (such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT) and the like).

[0073] The positive electrode active material layer may further optionally include a conductive agent. As an example, the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0074] The positive electrode active material layer may also optionally include a binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorine-containing acrylate resin.

[0075] According to an embodiment of the present application, the battery includes a negative electrode plate, and the negative electrode active material of the negative electrode plate includes a silicon-containing substance.

[0076] The theoretical specific capacity of silicon is as high as 4200mAh / g, which is ten times that of graphite. In addition, it has the characteristics of abundant reserves, low cost, environmental friendliness, and low separation potential (~0.4V vs.Li / Li + In some embodiments, the negative electrode active material includes graphite and a silicon-containing substance, wherein the content of graphite is 2% to 30%, and the content of the silicon-containing substance is 70% to 98%. For example, the silicon-containing substance may include at least one of silicon oxygen, silicon carbon, and silicon nanoparticles.

[0077] According to an embodiment of the present application, the negative electrode plate includes a negative electrode current collector and a negative electrode active material layer, the negative electrode active material layer is located on at least one side of the negative electrode current collector, and the negative electrode active material layer includes a negative electrode active material.

[0078] The negative electrode plate includes a negative electrode current collector, and the negative electrode current collector can be a metal foil or a composite current collector. For example, as the metal foil, a copper foil can be used. The composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), etc.).

[0079] The negative electrode active material layer may also optionally include a binder, which may include one or more of sodium carboxymethyl cellulose (CMC-Na), lithium carboxymethyl cellulose (CMC-Li), lithium polyacrylate (PAA-Li), sodium polyacrylate (PAA-Na) or styrene-butadiene rubber (SBR). The mass ratio of the negative electrode slurry is active material: binder: conductive agent = 100: 1.0-4.0: 0.05-0.5; the compaction density of the negative electrode sheet obtained after rolling is 1.55-1.80 g / cm 3 .

[0080] The negative electrode active material layer may further optionally include a conductive agent, which may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0081] According to an embodiment of the present application, the battery includes a separator and an electrolyte.

[0082] The diaphragm can be any known porous structure isolation membrane with good chemical stability and mechanical stability. For example, the diaphragm can include at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, polyvinylidene fluoride, and ceramic coating modified diaphragm.

[0083] The electrolyte includes lithium salt LiPF6, carbonate solvents and various additives, wherein the various additives include SEI film-forming additives, overcharge additives, flame retardant additives, and high and low temperature performance improvement additives, etc. Exemplarily, the SEI film-forming additive includes one or more of lithium bis(oxalatoborate), fluoroethylene carbonate or vinylene carbonate, and the lithium salt electrolyte content in the electrolyte is 0.5 mol / L to 2.0 mol / L.

[0084] The second aspect of the present application provides a battery. According to an embodiment of the present application, the battery is obtained by forming a battery to be formed using the formation method of the battery described in the first aspect of the present application. The features and advantages described above for the formation method of the battery are also applicable to the battery and will not be repeated here.

[0085] The battery may include an outer packaging for packaging the positive electrode sheet, the negative electrode sheet and the electrolyte.

[0086] The outer packaging may include a shell and a cover plate. The shell may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate are enclosed to form a receiving cavity. The shell has an opening connected to the receiving cavity, and the cover plate can be covered on the opening to close the receiving cavity.

[0087] The outer packaging of the battery can be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell; the outer packaging of the battery can also be a soft package, such as a bag-type soft package. The material of the soft package can be plastic, such as at least one of polypropylene (PP), polybutylene terephthalate (PBT), and polybutylene succinate (PBS).

[0088] The battery of the present application may include a battery cell form, a battery module form and a battery pack form. In some embodiments, the battery cells can be assembled into a battery module, and the number of battery cells contained in the battery module can be one or more, and the specific number can be selected by those skilled in the art according to the application and capacity of the battery module. In some embodiments, the battery modules can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be one or more, and the specific number can be selected by those skilled in the art according to the application and capacity of the battery pack.

[0089] The third aspect of the present application provides an electric device. According to an embodiment of the present application, the electric device includes the battery described in the second aspect of the present application. The features and advantages described above for the battery are also applicable to the electric device and will not be repeated here.

[0090] Battery cells, battery modules, and battery packs can be used as power sources for electrical devices or as energy storage units for electrical devices. Electrical devices may include, but are not limited to, mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships, satellites, energy storage systems, etc.

[0091] As an electrical device, a battery cell, battery module or battery pack can be selected according to its usage requirements.

[0092] As an embodiment, the electric device may be a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, etc. In order to meet the requirements of the electric device for high power and high energy density of the battery, a battery pack or a battery module may be used.

[0093] As another embodiment, the device may be a mobile phone, a tablet computer, a notebook computer, etc. The device is usually required to be light and thin, and a battery cell may be used as a power source.

[0094] The scheme of the present application will be explained below in conjunction with the embodiments. It will be appreciated by those skilled in the art that the following embodiments are only used to illustrate the present application and should not be considered as limiting the scope of the present application. If no specific technology or conditions are indicated in the embodiments, the technology or conditions described in the literature in this area or the product specification are carried out. The reagents used or the instruments that do not indicate the manufacturer are all conventional products that can be obtained commercially.

[0095] Example 1

[0096] (1) Lithium cobalt oxide, conductive agent carbon nanotubes (CNT), and binder polyvinylidene fluoride (PVDF) are prepared into a positive electrode slurry in a weight ratio of 97.5:1.5:1, and the positive electrode slurry is evenly coated on aluminum foil, dried in an oven, and then pressed and rolled to form a positive electrode sheet.

[0097] (2) Graphite / silicon carbon, conductive agent carbon nanotube (CNT), binder styrene-butadiene rubber and polyacrylic acid (PAA / SBR), and sodium carboxymethyl cellulose (CMC) are prepared into a negative electrode slurry in a weight ratio of 96.4:0.2:3.2:0.2, and the negative electrode slurry is evenly coated on a copper foil, dried in an oven, and then pressed and rolled to form a negative electrode sheet.

[0098] (3) Stack the positive electrode sheet, separator (PE), and negative electrode sheet in order to complete the assembly. Soak the assembled battery cell in electrolyte (EC / EP / PC / DEC / PP / LiPF6 / LiBF4 / FEC=10:42:13:18:17:14:2:14, w / w) and seal it.

[0099] (4) Place in an oven at 45°C for 24 hours.

[0100] (5) First stage formation: The first stage temperature is 81°C, the pressure is 12kgf / 2pcs, the first step charging is 0.1C current charging for 20min, and the cut-off voltage is 3.1V; the second step charging is 0.2C current constant current charging for 20min, and the cut-off voltage is 3.5V; the third step charging is 0.8C current constant current charging for 40min, and the cut-off voltage is 4.0V;

[0101] (6) Second stage formation: The temperature of the second stage is 45°C and the pressure is 5kgf / 2pcs. The four-step charging is 0.7C current constant current constant voltage charging to 4.53V, and the cut-off current is 0.025C; the five-step cyclic discharge is 0.7C current constant current discharge to 3.0V; the five-step cyclic charging is 0.7C current constant current charging for 52min. Remove the vacuum and remove the air bag to obtain a silicon negative electrode lithium ion battery.

[0102] The differences between Examples 2-10, Comparative Example 1 and Comparative Example 2 and Example 1 are shown in Table 1.

[0103] Thermal shock test

[0104] At 23±2℃ and normal pressure (0.1MPa), 60 silicon negative electrode batteries prepared in Examples 1-10, Comparative Example 1 and Comparative Example 2 were charged at a constant current of 0.2C to a charge and discharge cut-off voltage of 4.53V, and then charged at a constant voltage to a cut-off current of 0.025C. After the battery cell is fully charged, the test is carried out within 24 hours. The test steps are as follows: heat with a convection method or a circulating hot air oven at a starting temperature of 25±3℃, a temperature change rate of 5±2℃ / min, and heat to 132±2℃, 134±2℃, 136±2℃, and maintain for 60 minutes before the test is terminated. The thermal shock passing standard is: the battery cell does not catch fire or explode. The results of the battery cell thermal shock test are expressed as a pass rate.

[0105] The results are shown in Table 1. The overall performance of the battery cells of Examples 1-10 is better than that of Comparative Examples 1 and 2.

[0106] Comparative Examples 1-3, Comparative Examples 1 and 2: Within a certain range, the smaller the one-step charging rate is, the denser and more uniform the inner layer of the SEI film is, and the better its thermal shock performance is. However, in order to take into account production efficiency, it is more appropriate to select a one-step charging rate of 0.02C to 0.1C, which can be selected according to actual production capacity requirements.

[0107] Comparing Example 1 and Example 4: the two-step charging rate of the first stage formation is too high, the film formation uniformity is reduced, and the thermal shock performance is reduced; when the two-step charging rate of the first stage formation is 0.1C to 0.2C, the battery performance is better.

[0108] Comparison of Example 1 and Example 5: The three-step charging rate of the first stage formation is too high, the film formation uniformity is reduced, and the thermal shock performance is reduced. When the three-step charging rate of the first stage formation is 0.5C to 1.2C, the battery performance is better.

[0109] Comparison of Example 1 and Example 6: The first stage formation temperature is low, the gel effect of the battery cell is poor, the overall battery performance is poor, and the thermal shock performance is reduced. When the first stage formation temperature is 75°C to 85°C, the battery performance is better.

[0110] Comparison of Example 1 and Example 7: The first stage formation pressure is low, the flatness of the battery cell deteriorates, and the thermal shock performance is reduced. When the first stage formation pressure is 10kgf / 2pcs to 15kgf / 2pcs, the battery performance is better.

[0111] Comparison of Example 1 and Example 8: The second stage formation temperature is too low, which is not conducive to the reconstruction of the SEI film, and its thermal shock performance is reduced. When the second stage formation temperature is 30°C to 45°C, the battery performance is better.

[0112] Comparison of Example 1, Example 9 and Example 10: The four-step charging rate is too low, the high temperature time increases, the SEI film decomposition intensifies, the consumption increases during the film formation process, the battery capacity decreases, and the thermal shock performance decreases; the four-step charging rate is too high, which is not conducive to the reconstruction of the SEI film, and its thermal shock performance decreases. When the four-step charging rate is 0.5C to 0.7C, the battery performance is better.

[0113]

Claims

1. A battery formation method, characterized in that: include: The battery to be formed is subjected to a first-stage formation treatment and a second-stage formation treatment; The temperature of the first stage chemical formation treatment is greater than the temperature of the second stage chemical formation treatment; The first stage formation treatment includes: sequentially performing a first step charging treatment, a second step charging treatment and a third step charging treatment; The charging rates of the first charging process, the second charging process and the third charging process are increased in sequence, and the charging rate of the first charging process is 0.02C to 0.1C.

2. The method according to claim 1, characterized in that The temperature of the first stage chemical treatment is 75°C to 85°C; And / or, the temperature of the second stage chemical conversion treatment is 30°C to 45°C.

3. The method according to claim 1, characterized in that The pressure of the first stage chemical formation treatment is greater than the pressure of the second stage chemical formation treatment.

4. The method according to claim 1 or 3, characterized in that: The pressure of the first stage chemical treatment is 10kgf / 2pcs to 15kgf / 2pcs; And / or, the pressure of the second stage chemical formation treatment is 5kgf / 2pcs to 7kgf / 2pcs.

5. The method according to claim 1, characterized in that The first step of charging treatment takes 20 to 100 minutes. The cut-off voltage of the first step charging process is no more than 3.5V.

6. The method according to claim 1, characterized in that The charging rate of the second step charging treatment is 0.1C to 0.2C; And / or, the second step of charging treatment lasts for 20 minutes to 40 minutes; And / or, the cut-off voltage of the second step charging process is no more than 3.8V.

7. The method according to claim 1, characterized in that The charging rate of the third step of charging treatment is 0.5C to 1.2C; And / or, the duration of the third step of charging treatment is 25 min to 60 min; And / or, the cut-off voltage of the third step charging process is no more than 4.2V.

8. The method according to claim 1, characterized in that The second stage formation treatment includes: a fourth step of charging treatment and a fifth step of circulation treatment are performed in sequence.

9. The method according to claim 8, characterized in that The charging rate of the fourth step charging treatment is 0.5C to 0.7C, constant current and constant voltage; And / or, the cut-off voltage of the fourth step charging process is 4.48V to 4.56V, and the cut-off current is 0.02C to 0.03C.

10. The method according to claim 8, characterized in that The fifth step of the cycle treatment includes cyclically performing a fifth discharge treatment and a fifth charge treatment, and the cycle rate is 0.5C to 0.7C; The fifth discharge process discharges at a constant current to 2.75V to 3.4V; The fifth charging process is performed with constant current charging for 52 min to 72 min.

11. The method according to claim 1, characterized in that: The battery to be formed is pre-aged at a temperature of 30° C. to 45° C. for a time of 24 h to 72 h.

12. The method according to claim 1, characterized in that The battery comprises a lithium ion battery.

13. The method according to claim 1 or 12, characterized in that: The battery comprises a negative electrode plate, and the negative electrode active material of the negative electrode plate comprises a silicon-containing substance.

14. A battery, characterized in that: The battery is obtained by forming a battery to be formed using the battery formation method according to any one of claims 1 to 13.

15. An electrical equipment, characterized in that: Comprising the battery of claim 14.

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