WO2023184784A1 - Secondary battery, battery module, battery pack and electric device - Google Patents

Abstract

The present application provides a secondary battery, a battery module, a battery pack and an electric device. The secondary battery comprises a pole piece and an electrolyte, wherein the pole piece and/or the electrolyte comprises a negative thermal expansion material, and the negative thermal expansion material comprises at least one of a metal element, an alloy, a metal oxide, a metal sulfide, a cyanide, a fluoride, a polymer compound and a metal organic framework with a negative thermal expansion coefficient between -60ºC and 100ºC. The pole piece of the secondary battery provided in the present application can still maintain a relatively high rebound performance in a low-temperature environment, such that the battery has good operation conditions at low temperatures.

Description

Secondary batteries, battery modules, battery packs and electrical devices

Cross-references to related applications

This application claims priority to Chinese patent application 202210335846.5 titled "Secondary Batteries, Battery Modules, Battery Packs and Electrical Devices" submitted on March 31, 2022. The entire content of this application is incorporated herein by reference. .

Technical field

The present application relates to the technical field of lithium batteries, and in particular to a secondary battery, a battery module, a battery pack and an electrical device.

Background technique

In recent years, as the application range of secondary batteries represented by lithium-ion batteries has become more and more extensive, secondary batteries are widely used in energy storage power systems such as hydropower, thermal power, wind power and solar power stations, as well as power tools, electric bicycles, Electric motorcycles, electric vehicles, military equipment, aerospace and other fields. Since secondary batteries have a wide range of applications and a wide temperature range when used, higher requirements are placed on their electrochemical performance at low temperatures.

Contents of the invention

This application was made in view of the above-mentioned issues, and its purpose is to provide a secondary battery, battery module, battery pack and electrical device that can enhance the resilience of the pole piece of the secondary battery at low temperatures and improve the performance of the secondary battery. Low temperature operating conditions.

A first aspect of the present application provides a secondary battery, including a pole piece and an electrolyte, wherein the pole piece and/or the electrolyte contains a negative thermal expansion material, and the negative thermal expansion material is included at -60°C. At least one of metal elements, alloys, metal oxides, metal sulfides, cyanides, fluorides, polymer compounds and metal organic frameworks with a negative thermal expansion coefficient between 100°C and 100°C.

Therefore, the present application adds the above-mentioned negative thermal expansion material to the pole pieces and/or the electrolyte of the secondary battery, so that the pole pieces can still maintain a high degree of rebound expansion at low temperatures, thereby improving the performance of the electrolyte in low-temperature environments. The fluidity in the battery is improved, thereby improving the lithium deposition of the pole pieces and improving the operating conditions of the battery cells in low-temperature environments.

In any embodiment, the negative thermal expansion material is selected from the group consisting of artificial hollow fibers, antimony, bismuth, gallium, nickel sulfide, bronze, rubber, zirconium tungstate, scandium fluoride, zinc cyanide (Zn(CN) ₂ ), At least one of cadmium cyanide (Cd(CN) ₂ ) and gallium ruthenium oxide. Optionally, the negative thermal expansion material includes gallium ruthenium oxide.

By selecting the above types of negative thermal expansion materials, the deformation degree of the pole piece between -60°C and 100°C can be effectively adjusted, and the deformation amount can be kept in a low range (for example, within 10%), thereby making the battery core Within this temperature range, normal throughput of the electrolyte can still be carried out, improving the fluidity of the electrolyte, accelerating the transmission rate of active ions (such as lithium ions), and improving the lithium precipitation of the pole pieces, thus improving the operating conditions of the battery cell. .

In any embodiment, the pole piece includes:

current collector, and

An active material layer is provided on at least one side of the current collector, and the active material layer includes the negative thermal expansion material.

By adding negative thermal expansion materials to the active material layer, the rebound expansion of the pole piece at low temperatures can be improved, allowing the battery core to maintain a certain degree of volume expansion and contraction, and improving the fluidity of the electrolyte in low temperature environments.

In any embodiment, the pole piece includes a positive pole piece and/or a negative pole piece, the active material layer includes a negative active material layer and/or a positive active material layer, the negative active material layer and/or the The negative thermal expansion material is included in the positive active material layer.

By adding the negative thermal expansion material to the negative active material and/or the positive active material, the resilience of the negative electrode piece and/or the positive electrode piece at low temperatures can be effectively improved.

In any embodiment, based on the total mass of the negative active material layer, the mass percentage of the negative thermal expansion material is 0.01% to 6%, preferably 0.8% to 1.85%.

In any embodiment, based on the total mass of the cathode active material layer, the mass percentage of the negative thermal expansion material is 0.01% to 6%, preferably 1% to 2.2%.

By controlling the mass percentage of the negative thermal expansion material in the negative active material layer and/or the positive active material layer within an appropriate range, it can be ensured that the negative electrode piece and/or the positive electrode piece still have excellent rebound performance at low temperatures, thus It greatly improves the fluidity of the electrolyte and significantly and effectively improves the lithium precipitation of the pole pieces, while also ensuring the complete uniformity of the pole pieces.

In any embodiment, the active material layer includes:

active material layer; and

A negative thermal expansion material layer is provided on the side of the active material layer close to the current collector and/or the side of the active material layer away from the current collector, wherein the negative thermal expansion material layer contains the negative thermal expansion material layer. Thermal expansion materials.

In this application, the negative thermal expansion material layer is provided as a separate film layer, which is conducive to regulating the degree of rebound of the negative electrode piece and/or the positive electrode piece at low temperatures by regulating the thickness of the film layer, which is more conducive to Improve the lithium deposition situation of the pole pieces.

In any embodiment, the thickness of the negative thermal expansion material layer is 0.1 μm to 50 μm, preferably 5 μm to 45 μm.

The thickness of the negative thermal expansion material layer is within a suitable range, which is conducive to significantly improving the resilience of the pole piece at low temperatures, greatly improving the fluidity of the electrolyte, reducing the transfer resistance of charges and active ions, thereby effectively improving the pole piece The situation of lithium evolution.

In any embodiment, based on the total mass of the electrolyte, the mass percentage of the negative thermal expansion material is 0.01% to 5%, preferably 2% to 3.5%.

The mass percentage of negative thermal expansion materials in the electrolyte is within an appropriate range, which can greatly increase the freezing point of the electrolyte, allowing the electrolyte to maintain very good fluidity in low-temperature environments, thereby accelerating the release of active ions (such as lithium ions) The transmission rate can reduce the concentration gradient of lithium ions in the directions perpendicular to and parallel to the pole piece, and improve the lithium deposition of the pole piece.

A second aspect of the present application provides a battery module including the secondary battery of the first aspect of the present application.

A third aspect of the present application provides a battery pack, including the battery module of the second aspect of the present application.

A fourth aspect of the present application provides an electrical device, including at least one selected from the secondary battery of the first aspect of the present application, the battery module of the second aspect of the present application, or the battery pack of the third aspect of the present application. kind.

The battery modules, battery packs and electrical devices of the present application include the secondary battery provided by the present application, and thus have at least the same advantages as the secondary battery.

Description of drawings

Figure 1 is a test chart of interface lithium evolution of the negative electrode sheet of Example 1 at -10°C.

Figure 2 is a test chart of the interface lithium evolution of the negative electrode sheet of Comparative Example 1 at -10°C.

Figure 3 is a comparison chart of the resilience test results of the negative electrode piece in Example 1 and Comparative Example 1.

FIG. 4 is a schematic diagram of a secondary battery according to an embodiment of the present application.

FIG. 5 is an exploded view of the secondary battery according to the embodiment of the present application shown in FIG. 4 .

Figure 6 is a schematic diagram of a battery module according to an embodiment of the present application.

Figure 7 is a schematic diagram of a battery pack according to an embodiment of the present application.

FIG. 8 is an exploded view of the battery pack according to an embodiment of the present application shown in FIG. 7 .

FIG. 9 is a schematic diagram of a power consumption device using a secondary battery as a power source according to an embodiment of the present application.

Explanation of reference symbols:

1 battery pack; 2 upper box; 3 lower box; 4 battery module; 5 secondary battery; 51 shell; 52 electrode assembly; 53 top cover assembly.

Detailed ways

Hereinafter, embodiments specifically disclosing the secondary battery, battery module, battery pack, and electrical device of the present application will be described in detail with reference to the drawings as appropriate. However, unnecessary detailed explanations may be omitted. For example, detailed descriptions of well-known matters may be omitted, or descriptions of substantially the same structure may be repeated. This is to prevent the following description from becoming unnecessarily lengthy and to facilitate understanding by those skilled in the art. In addition, the drawings and the following description are provided for those skilled in the art to fully understand the present application, and are not intended to limit the subject matter described in the claims.

"Ranges" disclosed herein are defined in terms of lower and upper limits. A given range is defined by selecting a lower limit and an upper limit that define the boundaries of the particular range. Ranges defined in this manner may be inclusive or exclusive of the endpoints, and may be arbitrarily combined, that is, any lower limit may be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a particular parameter, understand that ranges of 60-110 and 80-120 are also expected. Furthermore, if the minimum range values 1 and 2 are listed, and if the maximum range values 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2- 3, 2-4 and 2-5. In this application, unless stated otherwise, the numerical range "a-b" represents an abbreviated representation of any combination of real numbers between a and b, where a and b are both real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" have been listed in this article, and "0-5" is just an abbreviation of these numerical combinations. In addition, when stating that a certain parameter is an integer ≥ 2, it is equivalent to disclosing that the parameter is an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

If there is no special description, all embodiments and optional embodiments of the present application can be combined with each other to form new technical solutions.

If there is no special description, all technical features and optional technical features of the present application can be combined with each other to form new technical solutions.

If there is no special instructions, all steps of the present application can be performed sequentially or randomly, and are preferably performed sequentially. For example, the method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, mentioning that the method may also include step (c) means that step (c) may be added to the method in any order. For example, the method may include steps (a), (b) and (c). , may also include steps (a), (c) and (b), may also include steps (c), (a) and (b), etc.

If there is no special explanation, the words "include" and "include" mentioned in this application represent open expressions, which may also be closed expressions. For example, "comprising" and "comprising" may mean that other components not listed may also be included or included, or only the listed components may be included or included.

In this application, the term "or" is inclusive unless otherwise specified. For example, the phrase "A or B" means "A, B, or both A and B." More specifically, condition "A or B" is satisfied by any of the following conditions: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists) ; Or both A and B are true (or exist).

During the research process, the inventor found that during the charging and discharging process of secondary batteries represented by lithium-ion batteries, both the positive and negative electrode plates expand to a certain extent, causing the battery core to also expand and contract to a certain extent. The core will repeatedly "suck in" and "spit out" the electrolyte like "breathing", so at different times, the infiltration of the electrolyte in the battery core will change in real time, so there are usually lithium ions in the direction perpendicular to the pole piece. Concentration gradient.

At the same time, in addition to the lithium ion concentration gradient in the direction perpendicular to the pole piece, in the direction parallel to the pole piece, affected by the uneven structure of the battery cell, the ion impedance is uneven, so that there is also a certain unevenness in the lithium ion concentration. Uniformity, and at the same time, due to the inconsistency in the volume changes of the electrode pole pieces during the charge and discharge process, the electrolyte in the electrode part also has a process of drying and rewetting.

The inventor also found that when the secondary battery is in a low-temperature environment, due to the influence of the external environment, the volume expansion and contraction of the positive and negative electrode plates will be affected to a certain extent, causing the "breathing" amplitude of the battery core to weaken, thereby causing To a certain extent, the fluidity of the electrolyte becomes weaker, and the lithium ion concentration gradient increases in both directions perpendicular to the pole piece and parallel to the pole piece, which will aggravate the lithium precipitation of the pole piece.

In view of the above technical problems, this application provides a secondary battery mainly from the perspective of the deformation degree of the positive and negative electrode plates in a low-temperature environment and the fluidity of the electrolyte. The secondary battery includes the electrode plates and the electrolyte, wherein , the pole piece and/or the electrolyte contains a negative thermal expansion material. In this application, by adding appropriate negative thermal expansion materials to the pole pieces and/or the electrolyte, the fluidity of the electrolyte in low temperature environments can be improved, and the degree of deformation of the pole pieces and the "breathing" amplitude of the battery core can be reduced. Large changes occur due to temperature changes, thereby improving the operating conditions of the battery core at low temperatures.

secondary battery

In one embodiment of the present application, the present application proposes a secondary battery including a pole piece and an electrolyte, wherein the pole piece and/or the electrolyte contains a negative thermal expansion material (NTE), and the negative thermal expansion material (NTE) is included in the negative thermal expansion material. Thermal expansion materials include at least one of metal elements, alloys, metal oxides, metal sulfides, cyanides, fluorides, polymer compounds and metal-organic frameworks that have a negative thermal expansion coefficient between -60°C and 100°C.

In this application, negative thermal expansion material refers to a type of material whose length or volume shrinks as the temperature increases; "having a negative thermal expansion coefficient between -60°C ~ 100°C" means that between -60°C and 100°C In at least one temperature range (for example, -60°C ~ 0°C), the average linear expansion coefficient or volume expansion coefficient is negative. Among them, the average linear expansion coefficient or volume expansion coefficient can be measured by the following method. For example, between -60°C and 100°C, take the temperature interval from T0°C to T°C, and test the length of the negative thermal expansion material at T0°C as L0, the volume is V0; the length at T°C is L, the volume is V, then the average linear expansion coefficient in the temperature interval from T0°C to T°C = (L-L0)/(T-T0)*L0, average Body expansion coefficient = (V-V0)/(T-T0)*V0.

Although the mechanism is not yet clear, the applicant unexpectedly discovered that since the above-mentioned negative thermal expansion material is added to the pole piece of the secondary battery in this application, under a lower temperature environment (such as between -60°C and 0°C) time), the negative thermal expansion material can weaken the shrinkage deformation of the pole piece due to the decrease in temperature, so that the pole piece can still maintain a high degree of rebound expansion, so the battery core can also maintain a certain degree of volume expansion and contraction, which can Maintain normal repeated "sucking in" and "spitting out" of the electrolyte to improve the fluidity of the electrolyte in low-temperature environments, thereby improving the lithium precipitation of the pole pieces and improving the operating conditions of the battery cells in low-temperature environments. In addition, this application can increase the freezing point of the electrolyte by adding the above-mentioned negative thermal expansion material to the electrolyte of the secondary battery, so that the electrolyte still maintains good fluidity in a low-temperature environment, thereby speeding up the activity of active ions (such as lithium). The transmission rate of ions) can improve the lithium deposition of the pole pieces, which can also improve the operating conditions of the battery cells in low-temperature environments.

In some embodiments, the negative thermal expansion material is selected from the group consisting of artificial hollow fibers, antimony, bismuth, gallium, nickel sulfide, bronze, rubber, zirconium tungstate, scandium fluoride, zinc cyanide (Zn(CN) ₂ ), At least one of cadmium cyanide (Cd(CN) ₂ ) and gallium ruthenium oxide (Ga ₂ RuO ₄ ). Optionally, the negative thermal expansion material includes gallium ruthenium oxide.

In this application, by selecting the above-mentioned types of negative thermal expansion materials, the deformation degree of the pole piece between -60°C and 100°C can be effectively adjusted, and the deformation amount can be kept in a low range (for example, within 10%). As a result, the battery core can still carry out normal throughput of the electrolyte within this temperature range, improve the fluidity of the electrolyte, accelerate the transmission rate of active ions (such as lithium ions), and improve the lithium precipitation of the pole pieces, thereby improving the battery core operating conditions. Among them, compared with other types of negative thermal expansion materials, gallium ruthenium oxide has a better effect on improving the deformation of the pole piece, and can better improve the fluidity of the electrolyte, thereby improving the battery core's temperature between -60°C and 100°C. operating conditions during the period.

In some embodiments, the pole piece includes: a current collector, and an active material layer disposed on at least one side of the current collector, where the active material layer includes the negative thermal expansion material.

In this application, by adding negative thermal expansion material to the active material layer, the rebound expansion property of the pole piece at low temperatures can be improved, allowing the battery core to maintain a certain degree of volume expansion and contraction, and improving the flow of electrolyte in low temperature environments. properties, reducing the transfer resistance of charges and active ions, thereby improving the lithium precipitation of the pole pieces and improving the operating conditions of the battery cells.

In some embodiments, the pole piece includes a positive pole piece and/or a negative pole piece, the active material layer includes a negative active material layer and/or a positive active material layer, the negative active material layer and/or the The negative thermal expansion material is included in the positive active material layer.

As a specific example, the negative thermal expansion material is included in the negative active material layer and/or the positive active material layer, which is equivalent to adding the negative thermal expansion material as an additive to the negative active material and/or the positive active material, and then containing the negative thermal expansion material. The negative active material and/or the positive active material of the negative thermal expansion material is coated on at least one side of the current collector as a separate active material layer. By adding negative thermal expansion materials to the negative active material and/or the positive active material, the resilience of the negative electrode piece and/or the positive electrode piece at low temperatures can be effectively improved, the fluidity of the electrolyte can be improved, and the charge and active ions can be reduced. The transfer impedance is improved, thereby improving the lithium deposition of the pole piece and improving the operating conditions of the battery cell.

In some embodiments, based on the total mass of the negative active material layer, the mass percentage of the negative thermal expansion material is 0.01% to 6%, for example, the mass percentage of the negative thermal expansion material is 0.05%, 0.1%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6% or within the range of any of the above values. Preferably, the mass percentage of the negative thermal expansion material is 0.8% to 1.85%.

In some embodiments, based on the total mass of the cathode active material layer, the mass percentage of the negative thermal expansion material is 0.01% to 6%, for example, the mass percentage of the negative thermal expansion material is 0.05%, 0.1%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6% or within the range of any of the above values. Preferably, the mass percentage of the negative thermal expansion material is 1% to 2.2%.

In this application, by controlling the mass percentage of the negative thermal expansion material in the negative active material layer and/or the positive active material layer within an appropriate range, it can be ensured that the negative electrode piece and/or the positive electrode piece still have excellent performance at low temperatures. The rebound performance can greatly improve the fluidity of the electrolyte, significantly and effectively improve the lithium precipitation of the pole pieces, and at the same time ensure the complete uniformity of the pole pieces.

In some embodiments, the active material layer includes: an active material layer and a negative thermal expansion material layer. The negative thermal expansion material layer is disposed on a side of the active material layer close to the current collector and/or the active material layer. A side of the layer away from the current collector, wherein the negative thermal expansion material is included in the negative thermal expansion material layer.

As a specific example, the negative thermal expansion material layer is disposed on the side of the active material layer close to the current collector, which is equivalent to disposing the negative thermal expansion material layer between the active material layer and the current collector. When the negative thermal expansion material layer is disposed on the side of the active material layer away from the current collector, it is equivalent to disposing the active material layer between the negative thermal expansion material layer and the current collector.

In this application, by arranging the negative thermal expansion material layer as a separate film layer on the side of the active material layer close to and/or away from the current collector, the rebound expansion properties of the negative electrode piece and/or the positive electrode piece at low temperatures can be improved. This further improves the volume expansion and contraction of the battery core, allowing the battery core to maintain normal "sucking in" and "spitting out" electrolyte at low temperatures, thus improving the fluidity of the electrolyte in low temperature environments, thereby improving the analysis of the pole pieces. Lithium state improves the operating conditions of batteries in low-temperature environments. Moreover, arranging the negative thermal expansion material layer as a separate film layer is also conducive to regulating the degree of rebound of the negative electrode piece and/or the positive electrode piece at low temperatures by regulating the thickness of the film layer, which is more conducive to the control of the electrode. Improve the lithium deposition situation of tablets.

In some embodiments, the thickness of the negative thermal expansion material layer is 0.1 μm to 50 μm. For example, the thickness of the negative thermal expansion material layer is 0.5 μm, 1 μm, 5 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm. , 40μm, 45μm, 50μm or within the range of any of the above values. Preferably, the thickness of the negative thermal expansion material layer is 5 μm to 45 μm.

In this application, the thickness of the negative thermal expansion material layer is within a suitable range, which is conducive to significantly improving the resilience of the pole piece at low temperatures, greatly improving the fluidity of the electrolyte, and reducing the transfer resistance of charges and active ions, thus Effectively improve the lithium precipitation situation of the pole piece.

In some embodiments, based on the total mass of the electrolyte, the mass percentage of the negative thermal expansion material is 0.01% to 5%. For example, the mass percentage of the negative thermal expansion material is 0.05%, 0.1% , 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5% or within the range of any of the above values. Preferably, the mass percentage of the negative thermal expansion material is 2% to 3.5%.

In this application, the mass percentage of negative thermal expansion materials in the electrolyte is within an appropriate range, which can greatly increase the freezing point of the electrolyte, so that the electrolyte still maintains very good fluidity in a low-temperature environment, thereby accelerating the activation of active ions ( Such as the transmission rate of lithium ions), reducing the concentration gradient of lithium ions in the direction perpendicular to the pole piece and parallel to the pole piece, improving the lithium precipitation situation of the pole piece, thus greatly improving the operating conditions of the battery cell in a low-temperature environment .

It should be noted that in this application, the negative thermal expansion material can be provided in the negative electrode sheet, the positive electrode sheet, the electrolyte, or any combination of the three of the secondary battery. When disposed in the negative electrode plate, the negative thermal expansion material can be added to the negative active material layer as an additive, or can be provided as a separate film layer on one side of the negative active material layer, or both methods can exist at the same time. When disposed in the cathode plate, the negative thermal expansion material can be added to the cathode active material layer as an additive, or can be provided as a separate film layer on one side of the cathode active material layer, or both methods can exist at the same time. . Any of the above arrangements or combinations thereof can be considered to fall within the protection scope of this application.

In some embodiments, the secondary battery of the present application includes a lithium-ion secondary battery or a sodium-ion secondary battery.

In addition, the secondary battery, battery module, battery pack and electric device of the present application will be described below with appropriate reference to the drawings.

In some embodiments, the secondary battery includes a separator in addition to a positive electrode sheet, a negative electrode sheet, and an electrolyte. During the charging and discharging process of the battery, active ions are inserted and detached back and forth between the positive and negative electrodes. The electrolyte plays a role in conducting ions between the positive and negative electrodes. The isolation film is placed between the positive electrode piece and the negative electrode piece. It mainly prevents the positive and negative electrodes from short-circuiting and allows ions to pass through.

[Positive pole piece]

The positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer disposed on at least one surface of the positive electrode current collector. The positive electrode active material layer includes a positive electrode active material layer, and the positive electrode active material layer includes a positive electrode active material.

As an example, the positive electrode current collector has two surfaces facing each other in its own thickness direction, and the positive electrode active material layer is disposed on any one or both of the two opposite surfaces of the positive electrode current collector.

In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. For example, as the metal foil, aluminum 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 base layer. The composite current collector can be formed by forming metal materials (aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver and silver alloys, etc.) on polymer material substrates (such as polypropylene (PP), polyterephthalate It is formed on substrates such as ethylene glycol ester (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

In some embodiments, the cathode active material may be a cathode active material known in the art for batteries. As an example, the cathode active material may include at least one of the following materials: an olivine-structured lithium-containing phosphate, a lithium transition metal oxide, and their respective modified compounds. However, the present application is not limited to these materials, and other traditional materials that can be used as positive electrode active materials of batteries can also be used. Only one type of these positive electrode active materials may be used alone, or two or more types may be used in combination. Examples of lithium transition metal oxides may include, but are not limited to, lithium cobalt oxides (such as LiCoO ₂ ), lithium nickel oxides (such as LiNiO ₂ ), lithium manganese oxides (such as LiMnO ₂ , LiMn ₂ O ₄ ), lithium Nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (such as LiNi _1/3 Co _1/3 Mn _1/3 O ₂ (also referred to as NCM333), LiNi _0.5 Co _0.2 Mn _0.3 O ₂ (can also be abbreviated to NCM523), LiNi _0.5 Co0. ₂₅ Mn _0.25 O ₂ (can also be abbreviated to NCM211), LiNi _0.6 Co _0.2 Mn _0.2 O ₂ (can also be abbreviated to NCM622), LiNi0 _.8 Co At least one of _0.1 Mn _0.1 O ₂ (also referred to as NCM811), lithium nickel cobalt aluminum oxide (such as LiNi _0.85 Co0 _.15 Al _0.05 O ₂ ) and its modified compounds. Lithium-containing phosphate with olivine structure Examples of salts may include, but are not limited to, lithium iron phosphate (such as LiFePO ₄ (also referred to as LFP)), composites of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO ₄ ), composites of lithium manganese phosphate and carbon , lithium iron manganese phosphate, at least one composite material of lithium iron manganese phosphate and carbon.

In some embodiments, the positive active material layer optionally further includes a binder. As examples, the binder may include polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene At least one of ethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer and fluorine-containing acrylate resin.

In some embodiments, the positive active material layer optionally further includes 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.

In some embodiments, the positive electrode sheet can be prepared by dispersing the above-mentioned components for preparing the positive electrode sheet, such as positive active material, conductive agent, binder and any other components in a solvent (such as N -methylpyrrolidone) to form a positive electrode slurry; the positive electrode slurry is coated on the positive electrode current collector, and after drying, cold pressing and other processes, the positive electrode piece can be obtained.

[Negative pole piece]

The negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer disposed on at least one surface of the negative electrode current collector. The negative electrode active material layer includes a negative electrode active material layer, and the negative electrode active material layer includes a negative electrode active material.

As an example, the negative electrode current collector has two opposite surfaces in its own thickness direction, and the negative electrode active material layer is disposed on any one or both of the two opposite surfaces of the negative electrode current collector.

In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, as the metal foil, 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 base material. The composite current collector can be formed by forming metal materials (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as polypropylene (PP), polyterephthalate It is formed on substrates such as ethylene glycol ester (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

In some embodiments, the negative active material may be a negative active material known in the art for batteries. As an example, the negative active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, lithium titanate, and the like. The silicon-based material may be selected from at least one of elemental silicon, silicon oxide compounds, silicon carbon composites, silicon nitrogen composites and silicon alloys. The tin-based material may be selected from at least one of elemental tin, tin oxide compounds and tin alloys. However, the present application is not limited to these materials, and other traditional materials that can be used as battery negative electrode active materials can also be used. Only one type of these negative electrode active materials may be used alone, or two or more types may be used in combination.

In some embodiments, the negative active material layer optionally further includes a binder. The binder can be selected from styrene-butadiene rubber (SBR), polyacrylic acid (PAA), polysodium acrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), poly At least one of methacrylic acid (PMAA) and carboxymethyl chitosan (CMCS).

In some embodiments, the negative active material layer optionally further includes a conductive agent. The conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.

In some embodiments, the negative active material layer optionally includes other auxiliaries, such as thickeners (such as sodium carboxymethyl cellulose (CMC-Na)) and the like.

In some embodiments, the negative electrode sheet can be prepared by dispersing the above-mentioned components for preparing the negative electrode sheet, such as negative active materials, conductive agents, binders and any other components in a solvent (such as deionized water) to form a negative electrode slurry; the negative electrode slurry is coated on the negative electrode current collector, and after drying, cold pressing and other processes, the negative electrode piece can be obtained.

[Electrolyte]

The electrolyte plays a role in conducting ions between the positive and negative electrodes. This application has no specific restrictions on the type of electrolyte and can be selected according to needs.

In some embodiments, the electrolyte solution includes an electrolyte salt and a solvent.

In some embodiments, the electrolyte salt may be selected from the group consisting of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bisfluorosulfonimide, lithium bistrifluoromethanesulfonimide, trifluoromethane At least one of lithium sulfonate, lithium difluorophosphate, lithium difluoroborate, lithium dioxaloborate, lithium difluorodioxalate phosphate and lithium tetrafluoroxalate phosphate.

In some embodiments, the solvent may be selected from the group consisting of ethylene carbonate, propylene carbonate, methylethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methylpropyl carbonate, ethylpropyl carbonate, Butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate At least one of ester, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone.

In some embodiments, the electrolyte optionally further includes additives. For example, additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain properties of the battery, such as additives that improve battery overcharge performance, additives that improve battery high-temperature or low-temperature performance, etc.

[Isolation film]

In some embodiments, the secondary battery further includes a separator film. This application has no special restrictions on the type of isolation membrane, and any well-known porous structure isolation membrane with good chemical stability and mechanical stability can be selected.

In some embodiments, the material of the isolation membrane can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride. The isolation film can be a single-layer film or a multi-layer composite film, with no special restrictions. When the isolation film is a multi-layer composite film, the materials of each layer can be the same or different, and there is no particular limitation.

In some embodiments, the positive electrode piece, the negative electrode piece and the separator film can be made into an electrode assembly through a winding process or a lamination process.

In some embodiments, the secondary battery may include an outer packaging. The outer packaging can be used to package the above-mentioned electrode assembly and electrolyte.

In some embodiments, the outer packaging of the secondary battery may be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer packaging of the secondary battery may also be a soft bag, such as a bag-type soft bag. The material of the soft bag may be plastic, and examples of the plastic include polypropylene, polybutylene terephthalate, polybutylene succinate, and the like.

This application has no particular limitation on the shape of the secondary battery, which can be cylindrical, square or any other shape. For example, FIG. 4 shows a square-structured secondary battery 5 as an example.

In some embodiments, referring to FIG. 5 , the outer package may include a housing 51 and a cover 53 . The housing 51 may include a bottom plate and side plates connected to the bottom plate, and the bottom plate and the side plates enclose a receiving cavity. The housing 51 has an opening communicating with the accommodation cavity, and the cover plate 53 can cover the opening to close the accommodation cavity. The positive electrode piece, the negative electrode piece and the isolation film can be formed into the electrode assembly 52 through a winding process or a lamination process. The electrode assembly 52 is packaged in the containing cavity. The electrolyte soaks into the electrode assembly 52 . The number of electrode assemblies 52 contained in the secondary battery 5 can be one or more, and those skilled in the art can select according to specific actual needs.

In some embodiments, secondary batteries can be assembled into battery modules, and the number of secondary batteries contained in the battery module can be one or more. Those skilled in the art can select the specific number according to the application and capacity of the battery module.

FIG. 6 is a battery module 4 as an example. Referring to FIG. 6 , in the battery module 4 , a plurality of secondary batteries 5 may be arranged in sequence along the length direction of the battery module 4 . Of course, it can also be arranged in any other way. Furthermore, the plurality of secondary batteries 5 can be fixed by fasteners.

Optionally, the battery module 4 may further include a housing having an accommodation space in which a plurality of secondary batteries 5 are accommodated.

In some embodiments, the above-mentioned battery modules can also be assembled into a battery pack. The number of battery modules contained in the battery pack can be one or more. Those skilled in the art can select the specific number according to the application and capacity of the battery pack.

7 and 8 illustrate the battery pack 1 as an example. Referring to FIGS. 7 and 8 , the battery pack 1 may include a battery box and a plurality of battery modules 4 disposed in the battery box. The battery box includes an upper box 2 and a lower box 3 . The upper box 2 can be covered with the lower box 3 and form a closed space for accommodating the battery module 4 . Multiple battery modules 4 can be arranged in the battery box in any manner.

In addition, the present application also provides an electrical device, which includes at least one of the secondary battery, battery module, or battery pack provided by the present application. The secondary battery, battery module, or battery pack may be used as a power source for the electrical device, or may be used as an energy storage unit for the electrical device. The electric device may include mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, and electric golf carts). , electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc., but are not limited to these.

As the power-consuming device, a secondary battery, a battery module or a battery pack can be selected according to its usage requirements.

Figure 9 is an electrical device as an example. The electric device is a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, etc. In order to meet the high power and high energy density requirements of the secondary battery for the electrical device, a battery pack or battery module can be used.

As another example, the device may be a mobile phone, a tablet, a laptop, etc. This device is usually required to be thin and light, and secondary batteries can be used as power sources.

Example

Hereinafter, examples of the present application will be described. The embodiments described below are illustrative and are only used to explain the present application and are not to be construed as limitations of the present application. If specific techniques or conditions are not specified in the examples, the techniques or conditions described in literature in the field or product instructions will be followed. If the manufacturer of the reagents or instruments used is not indicated, they are all conventional products that can be purchased commercially.

Example 1

Preparation of negative electrode plates

Mix 90 parts of negative active material graphite, 3 parts of negative thermal expansion material Ga2RuO4 powder, 2.2 parts of binder PVDF, 1.5 parts of conductive graphite, 1.5 parts of 1.3-butanediol, and 1.8 parts of NMP, add an appropriate amount of deionized water and stir evenly , to obtain the negative electrode slurry; apply the negative electrode slurry evenly on both surfaces of the negative electrode current collector copper foil to obtain the negative electrode active material layer; and then dry, cold press, cut, etc. to obtain the negative electrode pole pieces.

Preparation of positive electrode plates

Dissolve 97 parts of the positive active material lithium iron phosphate, 3 parts of the binder PVDF, and 1 part of the conductive agent acetylene black in the solvent NMP, stir and mix thoroughly to obtain a positive electrode slurry; apply the positive electrode slurry evenly on the positive electrode assembly On the two surfaces of the fluid copper foil, a positive active material layer is obtained; and then through drying, cold pressing, cutting, etc., a positive electrode piece is obtained.

Preparation of electrolyte

Mix ethylene carbonate (EC), ethyl methyl carbonate (EMC) and diethyl carbonate (DEC) at a volume ratio of 1:1:1 to obtain an organic solvent; dissolve LiPF6 in the above organic solvent, and then add Fluoroethylene carbonate (FEC) is mixed evenly to obtain an electrolyte.

Preparation of isolation film

Polypropylene film is used as the isolation film.

Preparation of secondary batteries

Stack the positive electrode sheet, isolation film, and negative electrode sheet in order and wind them to obtain an electrode assembly. Put the electrode assembly into the outer packaging, add the above-mentioned electrolyte, and go through processes such as packaging, standing, forming, and shaping to obtain the second electrode assembly. Secondary battery.

Examples 2 to 4

The preparation methods of Examples 2 to 4 are similar to Example 1, except that the content of Ga ₂ RuO ₄ powder in the negative active material layer is adjusted.

Examples 5 to 7

The preparation methods of Examples 5 to 7 are similar to Example 1, except that Ga ₂ RuO ₄ is not added to the negative active material layer, but Ga ₂ RuO ₄ is added to the positive active material layer, and the positive active material is adjusted. The content of Ga ₂ RuO ₄ powder in the layer.

Examples 8 to 13

The preparation methods of Examples 5 to 7 are similar to Example 1, except that Ga ₂ RuO ₄ is not added to the negative active material layer, but Ga ₂ RuO ₄ is applied to the negative active material layer as a separate negative thermal expansion material layer. The side closer to/away from the current collector, and the thickness of the negative thermal expansion material layer is adjusted.

Examples 14 to 16

The preparation methods of Examples 8 to 13 are similar to Example 1, except that Ga ₂ RuO ₄ is not added to the negative active material layer, but Ga ₂ RuO ₄ powder is added to the electrolyte, and the electrolyte is adjusted. Ga ₂ RuO ₄ content.

Example 17

The preparation method of Example 17 is similar to that of Example 1, except that Ga ₂ RuO ₄ is added to the electrolyte solution at the same time.

Example 18

The preparation method of Example 18 is similar to that of Example 8, except that Ga ₂ RuO ₄ is added to the electrolyte solution at the same time.

Comparative example 1

The preparation method of Comparative Example 1 is similar to that of Example 1, except that Ga ₂ RuO ₄ is not added to the negative active material layer, that is, Ga ₂ RuO ₄ is not added to the secondary battery.

The relevant parameters of the secondary batteries of the above-mentioned Examples 1 to 18 and Comparative Example 1 are shown in Table 1 below.

Table 1: Parameter results of Examples 1 to 18 and Comparative Example 1

test part

In addition, the performance of the secondary batteries of the above-mentioned Examples 1 to 18 and Comparative Example 1 was tested, and the test results are shown in Table 2 below.

(1) Lithium evolution test

The pole piece cells in Examples 1 to 18 and Comparative Example 1 were fully charged and discharged at different rates in a low temperature environment (-10°C) for a certain number of cycles; at the end of the cycle, the cells were fully charged and the interface was disassembled. , observe the lithium precipitation at the interface of the pole piece.

(2)Pole piece rebound rate test

Take 3m of each pole piece in Examples 1 to 18 and Comparative Example 1, measure the thickness of different parts after cold pressing, calculate the average value, and record it as T0; the aforementioned pole pieces are fully tested in a low temperature environment (-10°C). Charge, and test the thickness of different parts, calculate the average value, record it as T1; place the fully charged pole piece in a low temperature environment (-10℃), measure the thickness of the pole piece in different parts after 24 hours, calculate the average value, record it is Tn; 24h pole piece rebound rate = (Tn-T0)/T0*100%.

(3) Charge transfer impedance test

Take the pole pieces in Examples 1 to 18 and Comparative Example 1 to prepare samples. The number of samples is no more than 5, and the total area is required to be 500cm ² (width is not less than 8cm). Among them, each sample can take 5 to 6 of the middle layer of the battery core. Layer the electrode piece, and then use an electrochemical impedance analyzer to conduct a charge transfer impedance test at low temperature (-10°C) on the electrode piece, and record the test results.

Table 2: Performance test results of Examples 1 to 18 and Comparative Example 1

According to the above results and the comparison between Figures 1 and 2, it can be seen that in Examples 1 to 18, regardless of whether the negative thermal expansion material (NTE) is added to the positive electrode piece, the negative electrode piece, or the electrolyte, the lithium evolution of the secondary battery is the same. has been significantly improved; and according to the comparison results in Figure 3 and Table 2, it can be seen that after adding negative thermal expansion material (NTE) to the negative electrode piece or the positive electrode piece, the rebound rate of the electrode piece at low temperature (-10℃) is significantly improved. Improvement, indicating that adding negative thermal expansion materials can indeed improve the rebound performance of the pole piece at low temperatures. In addition, according to Table 2, it can be seen that compared with Comparative Example 1, the charge transfer resistance of Examples 1 to 18 at low temperatures (-10°C) is reduced, indicating that adding negative thermal expansion materials can improve the resistance of the electrolyte at low temperatures (-10°C). ℃), thereby improving the operating conditions of secondary batteries at low temperatures.

It should be noted that the present application is not limited to the above-described embodiment. The above-mentioned embodiments are only examples. Within the scope of the technical solution of the present application, embodiments that have substantially the same structure as the technical idea and exert the same functions and effects are included in the technical scope of the present application. In addition, various modifications that can be thought of by those skilled in the art may be made to the embodiments without departing from the scope of the present application.

Claims (12)

1. A secondary battery including a pole piece and an electrolyte, wherein the pole piece and/or the electrolyte contains a negative thermal expansion material, and the negative thermal expansion material has negative thermal expansion between -60°C and 100°C. The coefficient is at least one of metal elements, alloys, metal oxides, metal sulfides, cyanides, fluorides, polymer compounds and metal organic frameworks.
2. The secondary battery according to claim 1, wherein the negative thermal expansion material is selected from the group consisting of artificial hollow fibers, antimony, bismuth, gallium, nickel sulfide, bronze, rubber, zirconium tungstate, scandium fluoride and gallium ruthenium oxide At least one of, optionally, the negative thermal expansion material includes gallium ruthenium oxide.
3. The secondary battery according to claim 1 or 2, wherein the pole piece includes:

   current collector, and

   An active material layer is provided on at least one side of the current collector, and the active material layer includes the negative thermal expansion material.
4. The secondary battery according to claim 3, wherein the electrode piece includes a positive electrode piece and/or a negative electrode piece, the active material layer includes a negative electrode active material layer and/or a positive electrode active material layer, and the negative electrode active material layer The negative thermal expansion material is included in the material layer and/or the cathode active material layer.
5. The secondary battery according to claim 4, wherein the mass percentage of the negative thermal expansion material is 0.01% to 6%, optionally 0.8% to 1.85%, based on the total mass of the negative active material layer.
6. The secondary battery according to claim 4, wherein the mass percentage of the negative thermal expansion material is 0.01% to 6%, optionally 1% to 2.2%, based on the total mass of the positive active material layer.
7. The secondary battery according to claim 3, wherein the active material layer includes:

   active material layer; and

   A negative thermal expansion material layer is provided on the side of the active material layer close to the current collector and/or the side of the active material layer away from the current collector, wherein the negative thermal expansion material layer contains the negative thermal expansion material layer. Thermal expansion materials.
8. The secondary battery according to claim 7, wherein the thickness of the negative thermal expansion material layer is 0.1 μm to 50 μm, preferably 5 μm to 45 μm.
9. The secondary battery according to claim 1 or 2, wherein the mass percentage of the negative thermal expansion material is 0.01% to 5%, preferably 2% to 3.5%, based on the total mass of the electrolyte.
10. A battery module including the secondary battery according to any one of claims 1 to 9.
11. A battery pack including the battery module according to claim 10.
12. An electrical device includes at least one selected from the group consisting of the secondary battery according to any one of claims 1 to 9, the battery module according to claim 10, or the battery pack according to claim 11.

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