Patent Description:
An electrochemical apparatus is an energy storage apparatus capable of storing and releasing electrical energy. As a representative, batteries have been widely used in various fields such as consumer electronic devices and electric transportation tools due to the advantages of high energy density, rechargeability, desirable cycle life, and the like. <CIT> discloses examples of such batteries.

With the increasing demand for electrochemical apparatuses in various fields, increasingly high requirements are imposed on energy density, cycling performance, and the like of the electrochemical apparatuses.

However, in the related art, the cycling performance of electrochemical apparatuses deteriorates in high-temperature environments and consequently affects the service life thereof.

This application provides an electrochemical apparatus and an electronic apparatus. Such electrochemical apparatus has good cycling performance in high-temperature environments and therefore has a long service life.

According to a first aspect, an embodiment of this application provides an electrochemical apparatus including a positive electrode plate. The positive electrode plate includes a positive electrode current collector and a positive electrode active material layer disposed on a surface of the positive electrode current collector. The positive electrode active material layer includes a positive electrode active material and a conductive agent, the conductive agent containing secondary particles, where a total sectional area S<NUM> of the secondary particles and a sectional area S<NUM> of the positive electrode active material layer satisfy <NUM><So/Si≤<NUM>; diameter D<NUM> of the secondary particles satisfies <NUM><D<NUM>≤<NUM>; and percentages by number of secondary particles with the diameter D<NUM> within different ranges in a total number of secondary particles further satisfy:.

In the electrochemical apparatus provided in this embodiment of this application, the conductive agent contains secondary particles, where the total sectional area S<NUM> of the secondary particles and the sectional area S<NUM> of the positive electrode active material layer satisfy the foregoing relationship, the diameter D<NUM> of the secondary particles satisfies <NUM><D<NUM>≤<NUM>, and the percentage by number of secondary particles with the diameter D<NUM> within each range in the secondary particles satisfies the foregoing relationships. This can reduce agglomeration of the conductive agent to facilitate construction of a good conductive network structure in the positive electrode active material. In addition, with the conductive agent, a good conductive network structure can be formed in the positive electrode active material, and the conductive network structure helps to improve electron conduction capability of the positive electrode plate in high-temperature environments, thereby helping to reduce the resistance of the positive electrode plate. Therefore, the electrochemical apparatus provided in this embodiment of this application has good cycling performance in high-temperature environments and therefore has a long service life.

In any one of the foregoing embodiments according to the first aspect of this application, a total sectional area S<NUM> of the secondary particles and a sectional area S<NUM> of the positive electrode active material layer further satisfy <NUM>≤S<NUM>/S<NUM>≤<NUM>.

In any one of the foregoing embodiments according to the first aspect of this application, particle size distribution of the positive electrode active material satisfies <NUM>≤Dv<NUM>/Dv<NUM>≤<NUM>.

In any one of the foregoing embodiments according to the first aspect of this application, the positive electrode active material includes a nickel-cobalt-manganese ternary material.

In any one of the foregoing embodiments according to the first aspect of this application, the percentage of the number of moles of nickel to the total number of moles of nickel, cobalt, and manganese in the nickel-cobalt-manganese ternary material is greater than or equal to <NUM>%.

In any one of the foregoing embodiments according to the first aspect of this application, in a section along a thickness direction of the positive electrode active material layer, the number density ρ of the secondary particles per unit area satisfies p≤<NUM>,<NUM>/cm<NUM>.

In any one of the foregoing embodiments according to the first aspect of this application, the secondary particle is formed by agglomeration of a plurality of primary particles, where the primary particles include at least one of granular conductive carbon or carbon nanotubes.

In any one of the foregoing embodiments according to the first aspect of this application, length L of the carbon nanotubes and diameter D<NUM> of the carbon nanotubes satisfy the following characteristics:.

In any one of the foregoing embodiments according to the first aspect of this application, the positive electrode active material layer further includes a binder, and the binder satisfies at least one of the following characteristics:.

In any one of the foregoing embodiments according to the first aspect of this application,the binder has a molecular formula (A):.

where in the formula (A), VDF represents vinylidene fluoride, which is a structural unit of Polyvinylidene fluoride; TFE represents tetrafluoroethylene, which is a structural unit of Ploytetrafluoroethylene; HFP represents hexafluoropropylene, which is a structural unit of Ployhexafluoropropylene; PVP represents vinylpyrrolidone, which is a structural unit of polyvinyl pyrrolidone; <NUM>≤m≤<NUM>; <NUM>≤n≤<NUM>; <NUM>≤r≤<NUM>; <NUM>≤x≤<NUM>; and m+n+r+x=<NUM>.

According to a second aspect, an embodiment of this application provides an electronic apparatus including the electrochemical apparatus in any one of the foregoing embodiments according to the first aspect.

The foregoing description is merely an overview of the technical solution of this application. For a better understanding of the technical means in this application such that they can be implemented according to the content of the specification, and to make the above and other objectives, features, and advantages of this application more obvious and easier to understand, the following describes specific embodiments of this application.

Persons of ordinary skill in the art can clearly understand various other advantages and benefits by reading the detailed description of some embodiments below. The accompanying drawings are merely intended to illustrate some embodiments and are not construed as a limitation on this application. Moreover, throughout the accompanying drawings, same parts are denoted by same reference signs. In the accompanying drawings:.

electrochemical apparatus; <NUM>. housing; <NUM>. electrode assembly; and <NUM>. top cover assembly.

The following describes in detail some embodiments of technical solutions of this application with reference to the accompanying drawings. The following embodiments are merely intended for a clearer description of the technical solutions of this application and therefore are used as just examples which do not constitute any limitation on the protection scope of this application.

Unless otherwise defined, all technical and scientific terms used herein shall have the same meanings as commonly understood by those skilled in the art to which this application relates. The terms used herein are intended to merely describe the specific embodiments rather than to limit this application. The terms "include", "comprise", and any other variations thereof in the specification, claims and brief description of drawings of this application are intended to cover non-exclusive inclusions.

In this specification, reference to "embodiment" means that specific features, structures or characteristics described with reference to the embodiment may be incorporated in at least one embodiment of this application. The word "embodiment" appearing in various places in the specification does not necessarily refer to the same embodiment or an independent or alternative embodiment that is exclusive of other embodiments. It is explicitly or implicitly understood by persons skilled in the art that some embodiments described herein may be combined with other embodiments.

In the description of some embodiments of this application, the term "and/or" is only an associative relationship for describing associated objects, indicating that three relationships may be present. For example, A and/or B may indicate the following three cases: presence of only A, presence of both A and B, and presence of only B. In addition, the character "/" in this specification generally indicates an "or" relationship between contextually associated objects.

In the description of some embodiments of this application, it should be noted that, unless otherwise stated, "more than" and "less than" are inclusive of the number itself, and "more types" in "one or more types" and "more" in "one or more" mean more than two types (two).

The appended claims define the subject-matter of the invention.

Before explaining the protection scope provided by some embodiments of this application, it is necessary to first provide a specific description of some problems existing in the related art for a better understanding of some embodiments of this application.

With the development of electrochemical apparatus technologies, the application thereof in various fields has become increasingly widespread. in addition, increasingly high requirements are imposed on energy density, cycling performance, and the like of electrochemical apparatuses.

In the related art, an electrochemical apparatus typically includes a positive electrode plate, a negative electrode plate, and a separator provided between the positive electrode plate and the negative electrode plate, where the positive electrode plate includes a positive electrode current collector and a positive electrode active material layer disposed on a surface of the current collector. To improve electron conduction capability of the positive electrode plate, typically a conductive agent is added into the positive electrode plate active material layer, the conductive agent is mixed with a positive electrode active material, a binder, and the like to form a positive electrode slurry, and then the slurry is applied onto the surface of the positive electrode current collector to form the positive electrode active material layer. However, agglomeration of the conductive agent in the positive electrode slurry increases resistance of the positive electrode plate, resulting in degradation of the cycling performance of the electrochemical apparatus in high-temperature environments.

In view of this, an embodiment of this application provides an electrochemical apparatus and an electronic apparatus. Such electrochemical apparatus has good cycling performance in high-temperature environments.

In this application, the electrochemical apparatus includes any apparatus in which an electrochemical reaction takes place. Specific examples of the apparatus include all types of primary batteries, secondary batteries, fuel batteries, solar batteries, or capacitors. For example, the electrochemical apparatus is a lithium secondary battery, where the lithium secondary battery may include a lithium metal secondary battery, a lithium-ion secondary battery, a lithium polymer secondary battery, or a lithium-ion polymer secondary battery.

An embodiment of this application provides an electrochemical apparatus including a positive electrode plate. The positive electrode plate includes a positive electrode current collector and a positive electrode active material layer disposed on a surface of the positive electrode current collector. The positive electrode active material layer includes a positive electrode active material and a conductive agent, the conductive agent containing secondary particles, where a total sectional area S<NUM> of the secondary particles and a sectional area S<NUM> of the positive electrode active material layer satisfy <NUM><S<NUM>/S<NUM>≤<NUM>; diameter D<NUM> of the secondary particles satisfies <NUM><D<NUM>≤<NUM>; and percentages by number of the secondary particles with the diameter D<NUM> within different ranges in a total number of secondary particles further satisfy:.

In this embodiment of this application, the positive electrode plate may be provided with the positive electrode active material layer on one surface of the positive electrode current collector or on both surfaces of the positive electrode current collector. This is not particularly limited in this embodiment of this application.

In this application, the secondary particle contained in the conductive agent is formed by agglomeration of a plurality of primary particles.

In the electrochemical apparatus provided in this embodiment of this application, the conductive agent contains secondary particles, where the total sectional area S<NUM> of the secondary particles and the sectional area S<NUM> of the positive electrode active material layer satisfy the foregoing relationship, the diameter D<NUM> of the secondary particles satisfies <NUM><D<NUM>≤<NUM>, and the percentage by number of the secondary particles with the diameter D<NUM> within each range in the secondary particles further satisfies the foregoing relationships. This can reduce agglomeration of the conductive agent to facilitate construction of a good conductive network structure in the positive electrode active material. In addition, with the conductive agent, a good conductive network structure can be formed in the positive electrode active material, and the conductive network structure helps to improve electron conduction capability of the positive electrode plate in high-temperature environments, thereby helping to reduce the resistance of the positive electrode plate. Therefore, the electrochemical apparatus provided in this embodiment of this application has good cycling performance in high-temperature environments and therefore has a long service life.

The positive electrode current collector is not particularly limited in this embodiment of this application. The positive electrode current collector may be a metal foil or a porous metal plate, for example, a foil or porous plate made of a metal such as aluminum, copper, nickel, titanium, iron, or alloy thereof. In some embodiments of this application, the positive electrode current collector is an aluminum foil.

In some embodiments of this application, a total sectional area S<NUM> of the secondary particles and a sectional area S<NUM> of the positive electrode active material layer further satisfy <NUM>≤S<NUM>/S<NUM>≤<NUM>.

In the foregoing embodiments, the total sectional area S<NUM> of the secondary particles and the sectional area S<NUM> of the positive electrode active material layer are helpful for reducing the resistance of the positive electrode plate, so as to reduce the swelling rate of the positive electrode plate and improve the cycling performance of the electrochemical apparatus.

In some embodiments of this application, particle size distribution of the positive electrode active material satisfies: <NUM>≤Dv<NUM>/Dv<NUM>≤<NUM>.

In some embodiments of this application, particle size distribution of the positive electrode active material satisfies <NUM>≤Dv<NUM>/Dv<NUM>≤<NUM>.

Dv<NUM> refers to a particle size at which the cumulative volume distribution percentage of the positive electrode active material reaches <NUM>%.

Dv50 refers to a particle size at which the cumulative volume distribution percentage of the positive electrode active material reaches <NUM>%.

In the foregoing embodiments, the particle size by volume of the positive electrode active material satisfies the foregoing relationship, helping to increase a compacted density of the positive electrode active material layer to allow for formation of a good conductive network structure in the positive electrode active material, thereby making the electrochemical apparatus achieve a high energy density and good charging and discharging rate performance.

In some examples, a particle size by volume Dv<NUM> of the positive electrode active material may be <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, or <NUM>. The particle size by volume Dv<NUM> of the positive electrode active material may be <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, or <NUM>. The particle size by volume Dv<NUM> of the positive electrode active material may be <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, or <NUM>. A ratio of the particle size by volume Dv<NUM> to the particle size by volume Dv<NUM> of the positive electrode active material may be <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, or <NUM>.

In some embodiments of this application, the positive electrode active material includes a nickel-cobalt-manganese ternary material. This can increase the capacity of the electrochemical apparatus and accordingly increase the energy density of the electrochemical apparatus.

In some embodiments of this application, the nickel-cobalt-manganese ternary material may be a ternary structural material such as NCM811, NCM622, NCM613, NCM523, or NCM111.

In NCM811, N represents nickel, C represents cobalt, M represents manganese, and <NUM> represents a molar ratio of element nickel, element cobalt, and element manganese in the ternary material. To be specific, the molar ratio of element nickel:element cobalt:element manganese is <NUM>:<NUM>:<NUM>, and in this case, the percentage of the number of moles of nickel to the total number of moles of nickel, cobalt, and manganese in the nickel-cobalt-manganese ternary material is <NUM>%. In NCM523, a molar ratio of element nickel:element cobalt:element manganese is <NUM>:<NUM>:<NUM>, and the percentage of the number of moles of nickel to the total number of moles of nickel, cobalt, and manganese in the nickel-cobalt-manganese ternary material is <NUM>%.

In some embodiments of this application, the percentage of the number of moles of nickel to the total number of moles of nickel, cobalt, and manganese in the nickel-cobalt-manganese ternary material is greater than or equal to <NUM>%. This makes the electrochemical apparatus achieve a high energy density.

In some other embodiments of this application, the positive electrode active material may further include an olivine-structured material such as lithium manganese iron phosphate, lithium iron phosphate, or lithium manganese phosphate, as well as at least one of a lithium cobaltate material, a lithium manganate material, or other metal oxides allowing for intercalation and deintercalation of lithium.

In some embodiments of this application, in a section along a thickness direction of the positive electrode active material layer, the number density ρ of the secondary particles per unit area satisfies p≤<NUM>,<NUM>/cm<NUM>.

In the foregoing embodiments, the number density ρ of the secondary particles per unit area being within the appropriate range mentioned above contributes to uniform dispersion of the conductive agent on the surface of the positive electrode active material, such that the positive electrode plate has a better conductive network structure, reducing the resistance of the electrochemical apparatus, thereby improving the cycling performance of the electrochemical apparatus in high-temperature environments.

In some examples, the number density ρ of the secondary particles per unit area may be <NUM>,<NUM>/cm<NUM>, <NUM>,<NUM>/cm<NUM>, <NUM>,<NUM>/cm<NUM>, <NUM>,<NUM>/cm<NUM>, <NUM>,<NUM>/cm<NUM>, <NUM>,<NUM>/cm<NUM>, <NUM>,<NUM>/cm<NUM>, <NUM>,<NUM>/cm<NUM>, <NUM>,<NUM>/cm<NUM>, <NUM>,<NUM>/cm<NUM>, <NUM>,<NUM>/cm<NUM>, <NUM>,<NUM>/cm<NUM>, <NUM>,<NUM>/cm<NUM>, <NUM>,<NUM>/cm<NUM>, <NUM>,<NUM>/cm<NUM>, <NUM>,<NUM>/cm<NUM>, <NUM>,<NUM>/cm<NUM>, <NUM>,<NUM>/cm<NUM>, or <NUM>,<NUM>/cm<NUM>.

In some embodiments of this application, the secondary particle is formed by agglomeration of a plurality of primary particles, where the primary particles include at least one of granular conductive carbon or carbon nanotubes.

It can be understood that the secondary particle may be formed by agglomeration of a plurality of granular conductive carbon, by agglomeration of a plurality of carbon nanotubes, or by agglomeration of granular conductive carbon and carbon nanotubes.

In some embodiments of this application, length L of the carbon nanotubes and diameter D<NUM> of the carbon nanotubes satisfy the following characteristics:.

In the foregoing embodiments, the carbon nanotubes satisfying the foregoing relationships can not only contribute to construction of a conductive network structure in the positive electrode active material but also allow broken positive electrode active material to be connected to further construct a better conductive network structure, thereby improving the cycling performance of the electrochemical apparatus in high-temperature environments.

In some examples, the length L of the carbon nanotubes may be <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, or <NUM>. The diameter D<NUM> of the carbon nanotubes may be <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, or <NUM>. The length-to-diameter ratio L/D<NUM> of the carbon nanotubes may be <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, or <NUM>.

In some other examples, the granular conductive carbon may be carbon black, acetylene black, Ketjen black, or the like.

In some embodiments of this application, the positive electrode active material layer further includes a binder, and the binder satisfies at least one of the following characteristics:.

In the foregoing embodiments, the binder satisfies at least one of (I), (II), (III) or (IV). This can contribute to dispersion of slurry compositions such as the conductive agent and the positive electrode active material so as to inhibit formation of gel, thereby reducing occurrence of abnormal agglomeration of the compositions. Especially in a high-nickel positive electrode active material system, formation of gel in the slurry can be further inhibited, and the electron conduction capability of the positive electrode plate can be improved, thereby further improving the cycling performance of the electrochemical apparatus in high-temperature environments.

In some embodiments of this application, the binder has a molecular formula (A):.

where in the formula (A), VDF represents a structural unit of vinylidene fluoride; TFE represents a structural unit of tetrafluoroethylene; HFP represents a structural unit of hexafluoropropylene; PVP represents a structural unit of polyvinyl pyrrolidone; <NUM>≤m≤<NUM>; <NUM>≤n≤<NUM>; <NUM>≤r≤<NUM>; <NUM>≤x≤<NUM>; and m+n+r+x=<NUM>.

In the foregoing embodiments, when x=<NUM>, the binder having the molecular formula (A) can be prepared using the following preparation method:.

In some embodiments of this application, an adhesion force F of the positive electrode active material layer satisfies <NUM> N/m≤F≤<NUM> N/m.

In the foregoing embodiments, the binder can help the positive electrode active material layer to have an adhesion force F satisfying the foregoing relationship. This helps the positive electrode plate to meet the requirements on adhesion force during processing and also can slow down an increase in the swelling rate of the positive electrode plate during cycling, allowing the electrochemical apparatus to have better cycling performance in high-temperature environments.

The adhesion force mentioned in the foregoing embodiments can be tested using the following test method:.

The positive electrode plate in this application can be prepared according to conventional methods in the art. For example, an active material, a conductive agent, and a binder are dispersed in and mixed with N-methylpyrrolidone (NMP) to form a uniform positive electrode slurry; and the positive electrode slurry is applied onto the positive electrode current collector, and then dried, cold-pressed, cut, slit, and dried again to obtain a positive electrode plate.

In some embodiments of this application, the electrochemical apparatus further includes a negative electrode plate, a separator, and an electrolyte.

The negative electrode plate 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. It can be understood that the negative electrode plate may be provided with the negative electrode active material layer on one surface of the negative electrode current collector or on both surfaces of the negative electrode current collector. This is not particularly limited in these embodiments of this application.

The negative electrode current collector may be a metal foil or a porous metal plate, for example, a foil or porous plate made of a metal such as copper, nickel, titanium, iron, or alloy thereof. In some embodiments of this application, the negative electrode current collector is a copper foil.

A type of the negative electrode active material in the negative electrode active material layer is not limited in this application and can be selected as required. For example, other negative electrode active materials include but are not limited to natural graphite, artificial graphite, mesocarbon microbeads (MCMB), hard carbon, soft carbon, silicon, a silicon-carbon composite, SiO, Li-Sn alloy, Li-Sn-O alloy, Sn, SnO, SnO<NUM>, spinel-structure Li<NUM>Ti<NUM>O<NUM>, or Li-Al alloy.

In some embodiments of this application, the negative electrode active material layer further includes a binder. The binder may be at least one selected from styrene-butadiene rubber (SBR), polyacrylic acid (PAA), polyacrylic acid sodium (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), or carboxymethyl chitosan (CMCS).

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

In some embodiments of this application, the negative electrode active material layer may further include other additives such as a thickener (for example, sodium carboxymethyl cellulose (CMC-Na)).

However, this application is not limited to the foregoing materials. Other well-known materials can alternatively be used for the negative electrode plate in this application, serving as negative electrode active materials, conductive agents, binders, and thickeners.

The negative electrode plate in this application can be prepared according to conventional methods in the art. For example, a negative electrode active material, a conductive agent, a binder, and a thickener are dispersed in a solvent that may be N-methylpyrrolidone (NMP) or deionized water, to form a uniform negative electrode slurry; the negative electrode slurry is applied onto the negative electrode current collector, and then dried and cold-pressed to obtain a negative electrode active material layer; and then a negative electrode plate is obtained.

The separator is provided between the positive electrode plate and the negative electrode plate to mainly prevent short circuit between the positive and negative electrodes and to allow active ions to pass through. The separator is not limited to any particular type in this application, and may be any well-known porous separator with good chemical stability and mechanical stability.

In some embodiments of this application, a material of the separator may be one or more selected from glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride, but is not limited to these materials. Optionally, the separator may be made of polyethylene and/or polypropylene. The separator may be a single-layer film or a multi-layer composite film. When the separator is a multi-layer composite film, all layers may be made of same or different materials. In some other embodiments of this application, the separator may also be provided with a ceramic coating or a metal oxide coating.

In the electrochemical apparatus, the electrolyte is a carrier for ion transport and capable of transporting ions between the positive electrode plate and the negative electrode plate, ensuring the advantages such as good cycling performance of the electrochemical apparatus.

In some implementations of this application, the electrolyte includes an organic solvent, a lithium salt, and an optional additive. Types of the organic solvent, the lithium salt, and the additive are all not specifically limited and can be selected as required.

In some embodiments of this application, the lithium salt includes but is not limited to at least one of lithium hexafluorophosphate (LiPF<NUM>), lithium tetrafluoroborate (LiBF<NUM>), lithium perchlorate (LiClO<NUM>), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bistrifluoromethanesulfonimide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluoro(oxalato)borate (LiDFOB), lithium dioxalate borate (LiBOB), lithium difluorophosphate (LiPO<NUM>F<NUM>), lithium difluoro(dioxalato)phosphate (LiDFOP), or lithium tetrafluoro oxalato phosphate (LiTFOP). One of the foregoing lithium salts may be used alone, or two or more thereof may be used together.

In some embodiments of this application, the organic solvent includes but is not limited to at least one of ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butylene carbonate (BC), fluoroethylene carbonate (FEC), methylmethyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), <NUM>,<NUM>-butyrolactone (GBL), sulfolane (SF), methyl sulfonyl methane (MSM), ethyl methyl sulfone (EMS), or ethyl sulfonyl ethane (ESE). One of the foregoing organic solvents may be used alone, or two or more thereof may be used together.

In some embodiments of this application, the additive may include a negative electrode film-forming additive or a positive electrode film-forming additive or may include an additive capable of improving some performance of the battery, for example, an additive for improving overcharge performance of the battery, or an additive for improving high-temperature performance or low-temperature performance of the battery.

In some examples, the additive includes but is not limited to at least one of fluoroethylene carbonate (FEC), vinylene carbonate (VC), vinyl ethylene carbonate (VEC), diethyl dithiophosphate (DTD), acrylic acid sulfate, ethylene sulfite (ES), <NUM>,<NUM>-propyl sultone (PS), <NUM>,<NUM>-propane sultone (PST), sulfonate cyclic quaternary ammonium salt, succinic anhydride, succinonitrile (SN), adiponitrile (ADN), tri(methylsilyl) phosphate (TMSP), or tri(methylsilyl) borate (TMSB).

The electrolyte can be prepared using conventional methods in the art. For example, the electrolyte may be prepared by uniformly mixing the organic solvent, the lithium salt, and the optional additive. An order of adding the materials is not particularly limited. For example, the lithium and the optional additive are added into the organic solvent and the resulting mixture is well mixed to obtain an electrolyte. Alternatively, the lithium salt is first added into the organic solvent, and then the optional additive is added into the organic solvent and the resulting mixture is well mixed to obtain an electrolyte.

In some embodiments of this application, the positive electrode plate, the negative electrode plate, and the separator may be made into an electrode assembly through winding or lamination.

The electrochemical apparatus in some embodiments of this application further includes an outer package for packaging the electrode assembly and the electrolyte. In some embodiments of this application, the outer package may be a hard shell, for example, a hard plastic shell, an aluminum shell, or a steel shell. Alternatively, the outer package may be a soft pack, for example, a bag-type soft pack. The soft pack may be made of plastic, for example, at least one of polypropylene (PP), polybutylene terephthalate (PBT), or polybutylene succinate (PBS).

The electrochemical apparatus is not limited to any particular shape and may be cylindrical, rectangular, or of any other shape. For example, <FIG> shows an electrochemical apparatus <NUM> of a rectangular structure as an example.

In some embodiments of this application, referring to <FIG>, the outer package may include a housing <NUM> and a top cover assembly <NUM>. The housing <NUM> includes a base plate and side plates connected to the base plate, and the base plate and the side plates enclose an accommodating cavity. The housing <NUM> has an opening communicating with the accommodating cavity, and the top cover assembly <NUM> can cover the opening to close the accommodating cavity. The positive electrode plate, the negative electrode plate, and the separator may be made into an electrode assembly <NUM> through winding or lamination. The electrode assembly <NUM> is packaged in the accommodating cavity. The electrochemical apparatus <NUM> may include one or more electrode assemblies <NUM>, and persons skilled in the art may make choices according to actual requirements.

After being injected into the housing, the electrolyte is subjected to processes such as vacuum packaging, standing, formation, and vacuum formation to obtain an electrochemical apparatus.

According to a second aspect, this application provides an electronic apparatus including the electrochemical apparatus according to the first aspect of this application.

The electronic apparatus is not particularly limited in some embodiments of this application and may be any known electronic apparatus used in the prior art. In some embodiments of this application, the electronic apparatus may include but is not limited to a notebook computer, a pen-input computer, a mobile computer, an electronic book player, a portable telephone, a portable fax machine, a portable copier, a portable printer, a stereo headset, a video recorder, a liquid crystal television, a portable cleaner, a portable CD player, a mini-disc, a transceiver, an electronic notepad, a calculator, a memory card, a portable recorder, a radio, a standby power source, a motor, an automobile, a motorcycle, a motor bicycle, a bicycle, a lighting appliance, a toy, a game console, a timepiece, an electric tool, a flash lamp, a camera, a large household battery, or a lithium-ion capacitor.

Content disclosed in this application is described in detail in the following examples. These examples are merely for illustrative purposes because various modifications and changes made without departing from the scope of the content disclosed in this application are apparent to persons skilled in the art. All reagents used in Examples are commercially available or synthesized in a conventional manner, and can be used directly without further processing, and all instruments used in Examples are commercially available.

For ease of description, the lithium-ion secondary battery is used as an example of the electrochemical apparatus for detailed description of the electrochemical apparatus and manufacturing method thereof in the following examples.

A conductive agent (CNT-<NUM>) and a binder Y1 were added into NMP, stirred and mixed to prepare a conductive glue solution (with a solid content of <NUM>%);.

Artificial graphite, styrene-butadiene rubber, and sodium carboxymethyl cellulose at a mass ratio of <NUM>:<NUM>:<NUM> were mixed with deionized water and an additive, and a resulting mixture was well stirred to obtain a negative electrode slurry; and
the negative electrode slurry was applied onto a copper foil with a thickness of <NUM>, followed by drying, cold pressing, cutting, and tab welding, to obtain a negative electrode plate.

In a dry argon environment, EC, PC, and DEC (at a weight ratio of <NUM>:<NUM>:<NUM>) were mixed, then LiPF<NUM> was added, and the resulting mixture was well mixed to form a base electrolyte, where the concentration of LiPF<NUM> was <NUM> mol/L.

A polyethylene (PE) porous polymer film was used as the separator.

The positive electrode plate, the separator, and the negative electrode plate were wound in sequence to form an electrode assembly, the electrode assembly was placed into an outer packaging foil, and the electrolyte was injected into the outer packaging foil to infiltrate the electrode assembly, followed by processes such as packaging, formation, and shaping to obtain a lithium-ion secondary battery.

Preparation methods were similar to the preparation method in Example <NUM> except that some parameters of the positive electrode plate were different, specifically as shown in Table <NUM>.

Preparation methods were similar to the preparation method in example <NUM> except that some parameters of the positive electrode plate were different, specifically as shown in Table <NUM>.

Table <NUM> lists different parameters and test results of Examples <NUM> to <NUM> and Comparative examples <NUM> to <NUM>.

As shown in Table <NUM>, it can be learned from comparison between the test results of Examples <NUM>-<NUM> and Comparative examples <NUM>-<NUM> that when the total sectional area S<NUM> of the secondary particles and the sectional area S<NUM> of the positive electrode active material layer satisfy <NUM><S<NUM>/S<NUM>≤<NUM>, the diameter D<NUM> of the secondary particles satisfies <NUM><D<NUM>≤<NUM>, and the percentage by number of the secondary particles with the diameter D<NUM> within each range in the secondary particles further satisfies: when <NUM><D<NUM>≤<NUM>, <NUM>%≤η<NUM>≤<NUM>%; when <NUM><D<NUM>≤<NUM>, <NUM>%≤η<NUM>≤<NUM>%; and when <NUM><D<NUM>≤<NUM>, <NUM>%≤η<NUM>≤<NUM>%, the electrochemical apparatus has good cycling performance in high-temperature environments and therefore has a long service life.

Table <NUM> lists the test results obtained when the positive electrode active materials in Example <NUM> and Examples <NUM>-<NUM> have different Dv<NUM>/Dv<NUM> ratios and number densities.

As shown in Table <NUM>, the ratio of Dv<NUM> and Dv<NUM> of the positive electrode active material layer is within an appropriate range, not only allowing positive electrode active material particles with a small particle size to fill gaps of positive electrode active material particles with a large particle size so as to enhance contact between active particles of the positive electrode active material but also allowing the positive electrode active materials to be uniformly distributed so that their agglomeration is reduced, thereby helping to reduce the resistance of the positive electrode plate and reduce the swelling rate of the electrochemical apparatus, such that the electrochemical apparatus has good high-temperature cycling performance.

Table <NUM> lists the test results obtained when the positive electrode active materials in Examples <NUM>, <NUM>, and <NUM> have different nickel content, that is, different number densities.

It can be learned from Table <NUM> that the percentage of the number of moles of nickel to the total number of moles of nickel, cobalt, and manganese in the positive electrode active material layer is within an appropriate range, and the number density ρ of the secondary particles is within an appropriate range. Therefore, a high nickel content can improve the conductivity of the positive electrode plate, and the conductive agent containing the secondary particles can effectively inhibit formation of gel in the positive electrode slurry, thereby further helping to reduce the resistance of the positive electrode plate and the swelling rate of the electrochemical apparatus, so that the electrochemical apparatus has good high-temperature cycling performance.

Table <NUM> lists different binders and test results of Example <NUM> and Examples <NUM>-<NUM>.

It can be learned from Table <NUM> that the binder in the positive electrode active material layer includes various structural units and is capable of effectively inhibiting formation of gel and reducing agglomeration of the secondary particles, thereby facilitating improvement of the cycling performance of the lithium-ion secondary battery in high-temperature environments.

Table <NUM> lists the test results of Example <NUM> and Examples <NUM>-<NUM> when the carbon nanotubes have different lengths, diameters, and length-to-diameter ratios.

It can be learned from Table <NUM> that an appropriate length-to-diameter ratio of the carbon nanotubes facilitates formation of a conductive network structure in the positive electrode active material, thereby improving the electron conduction capability of the positive electrode plate and also reducing agglomeration of the positive electrode active material. In addition, an appropriate length-to-diameter ratio of the carbon nanotubes can allow the electrochemical apparatus to have a relatively high oxidization reduction potential, reducing occurrence of side reaction in the electrolyte, thereby allowing the electrochemical apparatus to have good electrochemical stability. Therefore, an appropriate length-to-diameter ratio of the carbon nanotubes can further allow the electrochemical apparatus to have good cycling performance and electrochemical stability in high-temperature environments.

Claim 1:
An electrochemical apparatus, comprising: a positive electrode plate, wherein the positive electrode plate comprises a positive electrode current collector and a positive electrode active material layer disposed on a surface of the positive electrode current collector, and the positive electrode active material layer comprises a positive electrode active material and a conductive agent, the conductive agent containing secondary particles;
wherein a total sectional area S<NUM> of the secondary particles and a sectional area S<NUM> of the positive electrode active material layer satisfy <NUM><S<NUM>/S<NUM>≤<NUM>;
a diameter D<NUM> of the secondary particles satisfies <NUM><D<NUM>≤<NUM>;
wherein a percentage η<NUM> of the secondary particles having the diameter D<NUM> satisfying <NUM><D<NUM>≤<NUM> in the secondary particles satisfies <NUM>%≤η<NUM>≤<NUM>%;
a percentage η<NUM> of the secondary particles having the diameter D<NUM> satisfying <NUM><D<NUM>≤<NUM> in the secondary particles satisfies <NUM>%≤η<NUM>≤<NUM>%; and
a percentage η<NUM> of the secondary particles having the diameter D<NUM> satisfying <NUM><D<NUM>≤<NUM> in the secondary particles satisfies <NUM>%≤η<NUM>≤<NUM>%.